Published by the Florida Association of Equine Practitioners, an Equine-Exclusive Division of the FVMA
SURGICAL INTERVENTION IN THE INITIAL TREATMENT AND LONG-TERM MANAGEMENT OF LAMINITIS FRED J. CALDWELL
DVM, MS, DACVS, DACVSMR
DIAGNOSIS, TREATMENT, AND REHABILITATION OF DORSAL SACROILIAC LIGAMENT PATHOLOGY ROB VAN WESSUM
DVM, MS, DACVSMR (EQ), CERT PRACT KNMvD (EQ)
ULTRASOUND TISSUE CHARACTERIZATION SARAH PLEVIN BVMS, MRCVS, CVA, DABVP, DACVSMR, RCVS SPECIALIST
The President's Line Hello fellow practitioners,
EXECUTIVE COUNCIL RUTH-ANNE RICHTER
BSc (Hon), DVM, MS FAEP COUNCIL PAST PRESIDENT
ADAM CAYOT DVM
Here we are, two thirds of the way through the year already. Personally, I feel like it has flown by due to all of the turmoil and odd circumstances. I hope you are all safe and doing well. The passing of Phil Hinkle, the FAEP/FVMA executive director, is a tremendous blow to our organization. Phil served the Florida Veterinary Medical Association (FVMA) for over 34 years and became the executive director in 2007. He was a tireless worker and a passionate advocate for our profession. His efforts reunited the Florida Association of Equine Practitioners (FAEP) with the FVMA in 2011. His meeting planning and organizational skills were outstanding. Working with him was a pleasure and an honor. He will be missed. The FVMA has always had a robust succession plan in place in the event it needed to be utilized. Deputy Executive Director, Ann Wade, and Associate Deputy Executive Director, Jim Naugle, will be acting as interim Executive Director and Deputy Executive Director of the FAEP/FVMA.
We felt that the appropriate course to follow, given current conditions of the pandemic, was to cancel the Promoting Excellence Symposium (PES), scheduled for October of 2020, and the Ocala Equine Conference, scheduled for January of 2021. However, we have an excellent program already planned for PES in October 2021; it will be a tremendous meeting! I want to thank our educational partners who provide us with so many opportunities. We hope that social conditions will be such that the meeting can be delivered in a somewhat traditional fashion.
Currently, we feel that the market is flooded with online CE opportunities and have elected to abstain from offering any at this time. We will continue to monitor the situation and offer high quality educational opportunities in whatever format is possible and best for our members.
AMANDA M. HOUSE DVM, DACVIM
DVM, MS, DACT
ANNE L. MORETTA VMD, MS, CVSMT, CVA
JACQUELINE S. SHELLOW DVM, MS REPRESENTATIVE TO FVMA EXECUTIVE BOARD
Summer is a great time to be in Florida, and I hope you all were able to take advantage of our numerous outdoor opportunities to aid your mental health. I look forward to the weather changing in the fall and the holidays coming. The upcoming cooler months are also busy for many of us as the Northern horses get shipped down. Let us all hope business is good this fall! Please take the time to enjoy being an equine veterinarian, and the opportunity you have to share your time with these awesome animals and their owners. Stay active and busy; focus on the future. Take care everyone, Armon Blair, DVM FAEP Council President
If anyone is feeling too stressed or mentally unwell, please do not hesitate to reach out to colleagues, friends, or the FAEP (call 800.992.3862).
Opinions and statements expressed in The Practitioner reflect the views of the contributors and do not represent the official policy of the Florida Association of Equine Practitioners or the Florida Veterinary Medical Association, unless so stated. Placement of an advertisement does not represent the FAEP’s or FVMA’s endorsement of the product or service. FAEP | 7207 MONETARY DRIVE, ORLANDO, FL 32809 | PH: 800.992.3862 | FAX: 407.240.3710 | EMAIL: INFO@FVMA.ORG | WEBSITE: WWW.FAEP.NET
2 The Practitioner
Issue 3 • 2020
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4 The Practitioner
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SURGICAL INTERVENTION IN THE INITIAL TREATMENT AND LONG-TERM MANAGEMENT OF LAMINITIS FRED J. CALDWELL | DVM, MS, DACVS, DACVSMR
Laminitis is a devastating disease that can affect all ungulates. Affected horses are often frustrating for veterinarians to manage. Furthermore, there is often a significant emotional component that accompanies this disease. The chronic pain displayed by laminitic horses is difficult for owners to witness. Dependent on the severity of the condition and response to treatment, horses may make a full recovery with no residual lameness, survive but never return to their previous level of activity, or require humane destruction. The majority of the general public was unfamiliar with laminitis until it suddenly became a common topic of conversation following Barbaro’s catastrophic breakdown in the 2006 Preakness Stakes (G1). Following this highly publicized event, and the colt’s untimely loss due to support limb laminitis, much interest and funding has been directed toward laminitis research. Currently, there are many groups around the country that are working to better understand this disease, which is a significant cause of morbidity and mortality in horses.
Despite descriptions of laminitis dating back to antiquity, the pathogenesis of laminitis in horses has yet to be fully elucidated.1 Laminitis, by the simplest definition, is inflammation of the sensitive and insensitive laminae of the foot. Dependent upon the severity of the pathologic changes between the epidermal and dermal lamellae, the distal phalanx may be unable to maintain its normal position in the hoof capsule due to the horse's weight and the opposing forces of the deep digital flexor tendon.1-3 Inflammation and ischemia of the laminae, with resulting displacement of the distal phalanx compressing the solar corium, is believed to be responsible for the excruciating pain experienced by laminitic horses.2 If the horse survives the initial bout of laminitis, it may suffer chronic alterations in blood flow, subsequent infections, and reduced growth of hoof tissues, resulting in long term discomfort and loss of function. The initiating factor for the development of laminitis is often a condition that results in systemic inflammatory response syndrome, particularly acute gastrointestinal disease (strangulating obstruction, enterocolitis, anterior enteritis), pleuropneumonia, retained fetal membranes, or grain overload.1-3 Other conditions that place horses at risk of laminitis include chronic non-weight bearing lameness leading to support limb laminitis, and endocrine diseases, such as pituitary pars intermedia dysfunction (PPID, or equine cushings syndrome) or insulin dysregulation. WWW.FAEP.NET |
Figure 1. Horse with a typical, “rocked-back” laminitis stance. This position shifts weight to the pelvic limbs in an attempt to unweight the thoracic limbs. Image courtesy of Fred J. Caldwell.
The current theories of laminitis pathogenesis include a vascular derangement, inflammatory response, and a coagulopathy.2,6 Since medical treatment of disease is directed toward its specific pathogenesis, many treatments currently employed in the management of laminitis are largely empirical and based on clinical responses instead of controlled scientific study. Although the current understanding of the pathogenesis of laminitis and its medical management in the acute case is important, it is beyond the scope of this article and is therefore only discussed briefly. It is the author’s intention to discuss the surgical intervention in the treatment of laminitis, namely deep digital flexor (DDF) tenotomy. Severing the tendon can minimize displacement of the distal phalanx in the chronic uncompensated case. When tenotomy is performed in conjunction with therapeutic trimming and shoeing in chronic compensated cases, orientation of the distal phalanx within the hoof capsule can be restored (see below for the definition of compensated vs uncompensated). These efforts are all aimed at restoring comfort, and, quite possibly, returning to a limited level of athletic activity by improving the functional biomechanics of the foot.
@FLORIDA_VMA | The Practitioner 5
Figure 2. A: Lateral plain radiograph (RF) of a 16 year old American Paso Fino gelding presenting with chronic uncompensated laminitis. Measurements including coronary band-extensor process distance (CE), horn-lamellar zone width (H/L), palmar angle of P3, degree of dorsal capsular rotation of P3, and sole depth at the dorsal tip of P3. B: Venogram study on presentation demonstrating perfusion deficits in the coronary plexus and lamellar zone, distal displacement of the dorsal solar margin of P3 beneath the lamellar circumflex junction, and disorganization of the recovering vasculature in the lamellar zone dorsally. Note the remodeling of the solar margin of P3 (inset image). Image courtesy of Fred J. Caldwell.
Clinical Presentation of Laminitis
Clinical signs of laminitis vary greatly depending on the inciting cause and severity of the disease. Horses suffering from acute laminitis typically demonstrate varying levels of pain and lameness initially recognized as a reluctance to move and a characteristic “rocked back” stance (Figure 1) that is meant to reduce the weight on the thoracic limbs, which are most commonly affected by laminitis. Further examination reveals an elevated temperature of the hoof capsule, bounding digital pulses, sensitivity to hoof testers, and edema of the coronet or distal limb. Histopathologic changes within the diseased tissue of the foot and a grading scale of laminitis was first reported by Obel in 1948.4 The system, which bears his name, is based on a numeric score ranging from mild signs of shifting limb lameness (grade 1) to a reluctance to move or recumbency (grade 4). This grading system, albeit somewhat outdated and clinically limited, is the most commonly utilized and will continue to be until a more descriptive system is developed and accepted.
phalanx, and marking the hoof wall. Structures that should be marked include the dorsal hoof wall, sole from the apex of the frog to the toe, and the hoof wall at the heels so that accurate measurements can be performed to evaluate the position of the distal phalanx within the hoof capsule. The author routinely uses barium paste to mark the hoof capsule as it conforms well to any abnormal contours that may be present. Useful measurements to record from lateromedial radiographs of the digit include the dorsal hoof wall to dorsal aspect of the distal phalanx thickness (H/L zone), the distance between the coronary band and the extensor process of the distal phalanx (CE), degree of dorsal capsular rotation (if present), sole thickness at the distal margin of the distal phalanx, and the palmar angle of the distal phalanx (Figure 2A). Although these values have not been consistently correlated with prognosis, they are useful in determining disease progression and for guiding corrective trimming and shoeing.
Venography of the digital vasculature has been well described in the standing horse and is valuable in the diagnostic evaluation Phases of laminitis have been categorized as developmental, acute, of the equine foot and detection of perfusion derangements subacute, chronic compensated, and chronic uncompensated. associated with laminitis (Figure 2B).7,8 Areas of interest on Developmental marks the period before clinical signs are apparent. venograms include the dorsal lamellar zone (sublamellar vascular Acute laminitis is defined as the first 72 hours following clinical bed), coronary plexus, circumflex vessels (lamellar circumflex signs or until displacement of the distal phalanx is detected. If no junction) and their terminal papillae, and terminal arch (Figure displacement occurs within 72 hours, the horse is considered to 3). Venography has potential prognostic value in that it has be in the subacute phase. Once displacement occurs, laminitis been reported that horses lacking contrast in key areas such as is considered chronic. If displacement ceases and the distal the lamellar zone, circumflex vessels, and terminal arch have phalanx stabilizes, laminitis is considered compensated. Chronic a grave prognosis for recovery due to the significant damage uncompensated laminitis implies that the distal phalanx shows related to lack of perfusion and irreversible damage to the digital evidence of continued displacement.2,5,6 circulation (Figure 4).7
Diagnostics One of the most important principles in the initial management Evaluation of the laminitic horse would not be complete without of the acute or early chronic laminitic horse is to eliminate obtaining a comprehensive series of correctly positioned foot peripheral loading of the hoof wall (especially the dorsal hoof radiographs of diagnostic quality. Digital radiographs are wall) and move the ground reaction force (GRF) axially to the frog preferred because of their excellent fine detail (especially with and caudal portion of the foot. It is critically important to recruit venography); however, good quality conventional radiographs other areas to support weight bearing and move the GRF away are suitable if digital radiography is unavailable. It is important from the hoof wall to minimize laminar damage and separation. to be consistent in positioning the horse squarely on elevated Additionally, it is recommended to elevate the heels in order blocks, centering the x-ray beam at the solar surface of the distal to reduce the tension in the deep digital flexor tendon. This is 6 The Practitioner
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Figure 3. Non-laminitic venogram study (lateral, horizontal DP, and 65 degree DP) of a 12 year-old TB gelding, note the evidence of contrast filling key areas of the coronary plexus (CP), lamellar zone (LZ) or sublamellar vascular bed, circumflex vessels (CV) and lamellar circumflex junction (LCJ), and terminal arch (TA) in addition to normal orientation of terminal papillae of the CP and CV (insets). Image courtesy of Fred J. Caldwell.
believed to effectively reduce the shearing forces on the damaged laminae, improve vascular supply, minimize displacement of the distal phalanx, and improve the horseâ€™s comfort level.2,3,5,6
a combination thereof. Regardless, equine practitioners are getting better at returning horses with chronic laminitis to an acceptable level of function, and the DDF tenotomy can be a useful intervention in that process.
Deep digital flexor (DDF) tenotomy was first evaluated as a surgical alternative to euthanasia for horses with severe chronic laminitis that was refractory to traditional medical treatment.9 With careful case selection, long term survival rates for DDF tenotomy is fair to good with a small percentage of horses returning to light use.9-11 Since the early reports of DDF tenotomy in the management of chronic laminitis, the outcome of cases managed with tenotomy have improved significantly. It is unclear if this improvement in outcome is due to improved medical management of the disease, earlier intervention, more aggressive treatment, better materials and methods for digital support, or
The procedure has been described as being performed as a standing procedure in the mid metacarpal region or under general anesthesia in the mid pastern region.12 Due to simplicity in performing the procedure in the standing patient and the lower likelihood for subluxation of the distal interphalangeal joint (DIPJ), DDF tenotomy is most commonly performed at mid metacarpus.
Figure 4. Chronic laminitic venogram study (right front lateral, horizontal DP) of an 11 year old warmblood gelding, note perfusion deficits on both views within the coronary plexus and lamellar zone, and distal displacement of the dorsal solar margin of P3 beneath the lamellar circumflex junction evident on the lateral view (inset). Image courtesy of Fred J. Caldwell.
Figure 5. Lichty teat knife which is ideally suited for a minimally invasive DDF tenotomy. The end is blunt to allow passage between the SDFT and DDFT, and the surgically sharp blade is nearly the same width as the loaded DDFT. Image courtesy of Fred J. Caldwell.
For standing DDF tenotomy, the metacarpus is clipped and prepared from below the carpus to above the fetlock. A high palmar nerve block is performed with mepivacaine and the horse
@FLORIDA_VMA | The Practitionerâ€‚ 7
Figure 6. A: Relapse of horse in Figure 2, four months after presentation. The horse was initially treated with hoof wall manipulation (dorsal grooving) and Equicast® EVA foam shoes secured with 2” fiberglass casting material. Venogram (RF) performed five weeks into trimming/casting cycle demonstrates perfusion deficits present throughout the coronary plexus, lamellar zone, lamellar circumflex junction, and circumflex vasculature (inset- EVA shoe removed in preparation for tenotomy). B: Lateral radiograph (RF) immediately following mid-metacarpus tenotomy and placement of an aluminum wedge rail shoe with heel extension secured with Equilox®. Note the moderate subluxation present within the distal interphalangeal joint. Image courtesy of Fred J. Caldwell.
is sedated with detomidine (0.01 mg/kg IV) and butorphenol (0.01 mg/kg IV). An effective high palmar nerve block will desensitize the skin of the metacarpus and the flexor tendons. Procaine penicillin G (22,000 IU/kg) and phenylbutazone are administered preoperatively. The tenotomy is performed at the mid-metacarpus level to avoid entering the carpal flexor sheath or digital tendon sheath. A #15 surgical blade is used to create a stab incision on the lateral aspect of the limb between the superficial digital flexor tendon (SDFT) and DDFT. A curved mosquito hemostat is used to tunnel around the DDFT dorsally and palmarly. The author uses a blunt-tipped, Lichty teat knife (Figure 5) to perform the tenotomy in a minimally invasive fashion by inserting it between the SDFT and DDFT and cutting the tendon in situ in a palmar-medial to dorso-lateral direction. The transection is nearly effortless when the teat knife is surgically sharp and the horse is fully weight-bearing. A palpable gap of 2-3 cm can be appreciated following complete tenotomy. The stab incision is closed with a single cruciate suture and the limb is bandaged. The author will keep a pressure bandage on the limb for up to six weeks following tenotomy, and the cosmetic result is very good in all cases. Occasionally, the procedure may need to be used for horses that experience a laminitic relapse or flexural deformity of the DIPJ due to chronic non-weight bearing. A second tenotomy is usually performed mid pastern because scarring and fibrosis that accompanies tenotomy at mid metacarpus obscures the anatomy and makes repeat tenotomy at this site difficult. A modified standing DDF tenotomy at the level of the proximal interphalangeal joint has been described.13 This technique was easy to perform in the standing patient and resulted in good DDFT release with no complications when performed in six experimental horses with no evidence of laminitis. Even though horses were shod with extended heel shoes following the tenotomy, four of the six horses demonstrated signs of subluxation within 30 days following surgery. This is theorized to be related to the increased release and significant retraction of the DDFT when
8 The Practitioner
transected at this level due to the reduced soft tissue attachments within the tendon sheath. Deciding when to perform DDF tenotomy in acute or early chronic laminitis cases is not straightforward. Tenotomy is considered a salvage procedure because most horses never return to ridden work, either directly due to the tenotomy or because of the severity of the laminitis prompting the procedure. Typically, the author will recommend DDF tenotomy in the following acute or early chronic scenarios: • • •
Where the horse has failed to respond to initial supportive therapy and there is evidence of poor vascular perfusion in key areas on the venograms. When dorsal capsular rotation of the distal phalanx is progressing radiographically. When the horse is in unrelenting pain and refractory to medical treatment.
It is often noted that horses will appear significantly more comfortable within 12-24 hours following the procedure. The DDF tenotomy has utility in the chronic compensated cases as well, namely where therapeutic farrier techniques alone have not been successful in re-establishing a more normal orientation of P3 to the hoof capsule. Additionally, it can be beneficial for horses with radiographic evidence of vascular compression or distortion.8 The author has had good success with surgical intervention in horses that experience repeated, chronic abscesses/septic osteitis due to vascular derangements identified venographically, as well as horses with poor hoof wall production or reduced sole depth.
Hoof Capsule Manipulations/Alterations
Hoof capsule grooving can be an effective way to “uncouple” the coronary band from the load transmitted through the hoof wall to restore perfusion to the coronary plexus, increase the rate of hoof Issue 3 • 2020
wall growth, and prevent divergence of the hoof wall from the distal phalanx. Grooving is usually performed dorsally but can be performed anywhere below the coronary band where pressure is focused with subsequent perfusion deficits in the coronary plexus. A Dremel™ tool with a 5/16” round-shaped high-speed accessory bit cuts quickly through the hoof wall and allows accurate grooving down to the level of the stratum internum. The author has used this technique, along with partial hoof wall resection to remove the lamellar wedge, to enhance venographic evidence of perfusion, and encourage a more normal hoof wall growth with good success.
Equally as important as the surgery, is close attention to the mechanical principles of supporting the distal limb following DDF tenotomy. A window of opportunity exists following a DDF tenotomy to re-establish the angle of P3 with respect to the weight-bearing surface (0-degree palmar angle). In the chronic case, this requires aggressive trimming of the heels and a placement of a rail shoe that is parallel with the solar surface of P3 (Figure 6). The shoe is customarily secured with acrylic, and radiographic guidance is critically important in achieving the correct placement of the shoe. In order to prevent subluxation of the DIPJ and subsequent degenerative joint disease (a common sequela to DDF tenotomy)
the shoe is set in a palmar position or an extended heel shoe is used. The rail shoe allows adjustment of the heel elevation by interchanging plastic rail inserts, or alternatively, the horse is maintained in soft ride boots with wedge pads until there is no longer radiographic evidence of subluxation of the joint. Establishing a partnership with a competent and willing farrier, in order to achieve the goals of therapeutic trimming and shoeing in these cases, is crucial. The methodologies are not as important as meeting the principles of supporting the distal phalanx according to our current understanding.
The search for an effective cure for laminitis is continuing. Prevention is obviously the best treatment and, in cases where signs of laminitis become apparent, aggressive medical and supportive care is paramount. Thorough diagnostic evaluation is necessary to provide prognostic indicators and guide treatment. In refractory cases, DDF tenotomy should be considered for its potential to reduce laminar injury, improve vascular supply, reduce pain, and increase growth of the hoof structures. Recently, lag screw placement through the dorsal hoof and into the coffin bone was evaluated as a method of stabilizing P3 within the hoof capsule in an oligofructose laminitis model.14 Biomechanical testing indicated that the lag screw was sufficient to counteract distracting forces to have a stabilizing effect on P3. Application of the lag screw, however, did not ameliorate pain in the induced laminitis model. Although encouraged, the researchers concluded that further studies are necessary before the screw placement technique can be recommended as a treatment option for horses with laminitis in clinical practice. The techniques described in this review may be beneficial in alleviating pain, restoring normal hoof function, and improving overall outcome for chronically laminitic horses (Figure 7).
References: 1. Eades SC, Holm AMS, Moore RM. A review of the pathophysiology and treatment of acute laminitis: pathophysiologic and therapeutic implications of endothelin-1, in proceedings. Am Assoc Equine Prac. 2002:353-361. 2. Parks AH. Treatment of acute laminitis. Equine Vet Educ. 2003;15:273-280. 3. Parks AH, Balch OK, Collier MA. Treatment of acute laminitis: Supportive therapy. Vet Clin N Am: Eq Prac. 1999;15:363-374. 4. Obel N. Studies on the histopathology of acute laminitis [dissertation]. Uppsala, Almqvist & Wiksells Boltryckeri AB, 1948, pp 50-53. Figure 7. Lateral radiograph (RF) of horse in Figures 2 and 6, six months following bilateral DDF tenotomy. Note improved angle of P3 relative to the hoof capsule and increased sole depth. The horse was sound and returned to light riding 10 months later. Image courtesy of Fred J. Caldwell.
5. Morrison S. Foot management. Clin Tech Equine Prac. 2004;3:71-82. 6. Parks AH, O’Grady SE. Chronic laminitis: Current treatment strategies. Vet Clin N Am: Eq Prac. 2003;19:393-416. 7. Redden RF. A technique for performing digital venography in the standing horse. Equine Vet Educ. 2001;13:128.134.
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8. Kramer J, Rucker A, Leise B. Venographic evaluation of the circumflex vessels and lamellar circumflex junction in laminitic horses. Equine Vet Educ. 2020;32:386-392. 9. Allen D, White NA, Foerner JF, Gordon BJ. Surgical management of chronic laminitis in horses: 13 cases (1983-1985). J Am Vet Med Assoc. 1986;189:1604-1606. 10. Hunt RJ, Allen D, Baxter GM, Jackman BR, Parks AH. Mid-metacarpal deep digital flexor tenotomy in the management of refractory laminitis in horses. Vet Surg. 1991;20:15-20.
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11. Eastman TG, Honnas CM, Hague BA, et. al. Deep digital flexor tenotomy as a treatment for chronic laminitis in horses: 35 cases (1988-1997). J Am Vet Med Assoc. 1999;214:517-519. 12. Fürst AE and Lischer CJ, Foot. In: Auer JA, Stick JA, Kümmerle JM, and Prange T eds: Equine Surgery, 5th edition, St. Louis, Saunders, 2019:1543-1587. 13. Waguepack RW, Caldwell FJ. How to perform a modified standing deep digital flexor tenotomy at the level of the proximal interphalangeal joint, in proceedings. Am Assoc Equine Prac. 2009:230-237. 14. Carmalt KP, Carmalt JL, Henderson K, et. al. Novel technique for prevention of rotation of the distal phalanx relative to the hoof wall in horses with acute laminitis. Am J Vet Res. 2019;80:943-949.
Fred J. Caldwell, DVM, MS, DACVS, DACVSMR Dr. Fred Caldwell is a Kentucky native and a graduate of the Auburn University College of Veterinary Medicine. He completed a surgical internship at Hagyard-Davidson-McGee Assoc. PLLC and a residency in large animal surgery at the University of Georgia. He spent one year as a large animal emergency surgeon at Cornell University Hospital for Animals before returning to Auburn where he is currently an associate professor of equine sports medicine and surgery. Dr. Caldwell is a diplomate of the American College of Veterinary Surgeons and the American College of Sports Medicine and Rehabilitation. His clinical interests include lameness/ poor performance evaluation, rehabilitation, orthopedic surgery, laparoscopy, and dentistry. His research interests involve minimally invasive surgical techniques, tendon and ligament repair, regenerative medicine, and wound healing. He enjoys the outdoors, fly-fishing, woodworking, and spending time with his wife, Joanna, and their two daughters.
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Diagnosis, Treatment, and Rehabilitation of Dorsal Sacroiliac Ligament Pathology DR. ROB VAN WESSUM | DVM, MS, DACVSMR (EQ), CERT PRACT KNMvD (EQ)
In recent years, many papers have been published about diagnosis, imaging, and therapy for sacroiliac joint disease. However, not much attention has been given to the pathology of the dorsal sacroiliac ligaments and the diagnosis, imaging, and therapy of these structures. In 2006, a paper by Engeli et al. gave guidelines for technique and normal versus abnormal images of the dorsal sacroiliac ligaments and its adjacent structures.1 Tomlinson et al. found some clear pathology in ligaments of horses with upper hind limb lameness, especially when imaging the left and right side and comparing the images.2 Goff et al. found a clear increase in sacral movement after cutting the ligaments in vitro, indicating the ligaments might have a clear limiting function of mobility in the pelvis of the horse.3 However, other than in some highly specialized sports medicine practices, not many veterinarians recognize that pathology in the dorsal sacroiliac ligaments might be the cause of hind limb lameness, nor do they have knowledge on how to design a rehabilitation program for this problem.
This paper will give some more step-by-step ideas on how to diagnose and treat ligament pathology in the sacroiliac region for the general practitioner.
Figure 1. Schematic picture of the dorsal sacroiliac ligament (DSL) and its relationship to the tuber sacrale (TS) and the sacral bone. Note the two portions of the ligament. This appearance might show the two separate portions of the ligament at the attachment site to the tuber sacrale (see Figure 2, where the sagittal view of the ligament clearly shows the two parts separated by a small fascia) while this is not visible at the core portion or the attachment site to the sacral bone. Image courtesy of Dr. Rob van Wessum.
As with any lameness exam, a detailed history offers the best start. When sacroiliac pathology is present, the normal movement of Often, there is a sudden onset of symptoms noted by the owner the sacroiliac region of the horse will be compromised.5,6,7 Altered without a clear traumatic event related to it—though falls, trailering sacroiliac mobility can be associated with several, very specific accidents, and getting cast in a stall have been mentioned in some alterations in the normal gait patterns of the horse.7,8 A short cases. Typically, owners will not note any physical abnormality description of these gait alterations and how to evaluate them other than a lack of performance, because trauma to the dorsal during a clinical exam is listed below. sacroiliac ligaments is hidden within the muscle mass of the hind quarters. Symptoms are often described as a lack of engagement Tracking Narrow Behind from behind, poor quality canter, refusal to jump, not keeping One of the first alterations of gait due to sacroiliac dysfunction is the canter or swapping leads behind frequently. Results of (trial) tracking narrow behind. This is often visible in the walk and even treatments with anti-inflammatory medication (phenylbutazone, more obvious in the trot. In the walk, there are always at least firocoxib, ketoprofen) are often disappointing. two limbs on the ground in the support phase. In trot, there is a suspension phase with no limbs on the ground and then a diagonal A standard lameness exam, to localize the cause of lameness or support phase with two limbs on the ground, making loading and poor performance and to exclude sources of lameness other than rotational forces on the sacroiliac region more pronounced. When the sacroiliac area, can also be used to evaluate the presence of six sacral rotation is avoided, the horse will place the hind feet close together in what is called a narrow behind. It can look like the indicators for sacroiliac pathology.4 horse is walking or trotting on a cord as the hind feet are placed on the same line in front of each other. 12 The Practitioner
Issue 3 • 2020
Asymmetric Tail Position
The best way to evaluate tail position is to observe the walk in a straight line and in a serpentine away from the clinician.7,8 When observed from behind, a horse’s tail should be in a relatively central position; when walking serpentine, the tail should remain in a midposition, with slight movements toward the side of the bending in the serpentine. When sacral dysfunction is present, the tail may be held asymmetrically. When the tail is held to one side, and stays to one side in the serpentine, there is a clear indication of sacroiliac dysfunction.7,8
Bunny Hop Canter
Figure 2. Sagittal images of dorsal sacroiliac ligaments (DSL) and the attachment to the tuber sacrale (TS). Splitting the screen with images from left and right sides allows for easy comparison. The left DSL is larger in total size (right image with red line) than the right DSL (shorter red line on left image) and the two separate ligament portions are all different sizes. Image courtesy of Dr. Rob van Wessum.
When observing the walk on a straight line, the walk should be a clear, four-beat motion. When spinal dysfunction is present, and the horse is asked to perform a serpentine in hand, the walk becomes more lateral, similar to a pace (hind limb and front limb on the same side advance at the same time). This finding has been associated with cervical spinal cord compression (“wobblers”) but is not well described with other spinal dysfunction. In the author’s opinion, the loss of a four beat walk is a clear indicator of tension, possibly pain, and decreased mobility in the spine.9,10 The best way to test for the symptoms of a lateral walk and a narrow behind is to first have the horse walk and trot in hand to and from the examiner/clinician, as in any lameness exam, and then to have the horse walk again but in a serpentine pattern. Observing the horse from the side when it passes by on the straight line can also be very helpful.
The fourth gait alteration often associated with sacroiliac dysfunction is a deterioration of the quality of the canter. This may even be a clear complaint of the client! A normal canter is three beats; the motion of the left lead and right lead should be comparable and relatively symmetric. There is a clear moment of suspension, and, when the footfalls are observed as the feet land in their specific pattern, there is a clear separation of the landing moments between the two hind feet.11 When sacroiliac dysfunction is present, this clear three beat is less obvious or will completely disappear. The hind feet may land nearly at the same moment and very close together. A good way to describe this phenomenon is “bunny hop.”7–10 Observing the horse in a relaxed canter (tension in the horse can mimic the bunny hop canter without indicating true spinal dysfunction) in both leads, on a lunge or while ridden, facilitates the evaluation of the canter. The author would advise having the horse do some cantering for several minutes in each direction, so it is possible to analyze the quality of the canter over time and not be distracted by initial behavior such as excitement, bucking, etc.
Reduced Flexibility of the Lumbosacral Region
The last part of the exam for achieving information about the sacroiliac region is “hands-on.” After observing the flexibility of the lumbosacral region in walk, trot, and canter, now the clinician
When observing a horse going away and coming at the clinician, the front limbs and the hind limbs should be on two tracks, the hind limbs follow the front limbs in the same plane. With sacral dysfunction, one hip is often kept slightly lower (this may be subtle), resulting in a slight bending to one side. When the haunches are brought to one side, the observer notes that the horse is on three or more tracks. The hind limbs do not follow the front limbs in the same plane but are placed laterally, away from the central axis. This is easily observed when the horse is lunged on a circle. If the haunches are more in, one sees the front limbs making a circle with a slightly larger diameter than the hind limbs. Conversely, when the haunches are out, the hind limbs travel on a larger diameter. In the canter, younger/untrained horses often have slight haunchesin at the canter, but nearly every “normal moving” horse should be tracking straight (“true”) in a walk and trot on a 25 to 30 foot diameter circle. WWW.FAEP.NET |
Figure 3. Longitudinal images of DSL at the same location as in Figure 1. Note the same difference in size and appearance is visible in these 90 degree-offset images, so it is less likely that we are looking at an artifact. Image courtesy of Dr. Rob van Wessum. FLORIDAAEP |
@FLORIDA_VMA | The Practitioner 13
evaluates the flexibility by manipulating it. With one hand on the tuber coxae and one hand on the tail, lateral flexion in both directions is tested by simultaneously pulling on the tail and pushing slightly on the tuber coxae. Ventral flexion is evaluated by making the horse “tuck under” by scratching it with a pointy object on the hamstrings on each side. Lateral and ventral flexibility should be symmetrical. A clear reduction of lateral and/or ventral flexibility is a good indicator for sacroiliac dysfunction.8,9,10 In the author’s practice, we have included the serpentine walk, lunging in all three gaits, and the manipulation of the lumbosacral region, as a standard protocol in every lameness exam. During nine years of practice (2005–2014), the author has examined 811 cases with a complaint of reduced performance or subtle hind limb lameness. Of these, 327 (40%) were diagnosed with sacroiliac disease based on clinical exam, imaging data (ultrasonography and scintigraphy), and improvement in symptoms or abnormal diagnostic findings at two, four, and six month recheck intervals after initial treatment and rehabilitation. Of these 327 cases of diagnosed and clinically substantiated sacroiliac disease, 322 had a positive score (“present”) for at least three indicators mentioned above. Of the 489 cases with a final diagnosis different from sacroiliac disease, less than 2% (seven horses) had more than three indicators positive. As a rule of thumb, when one can observe three or more of the indicators mentioned above, there is a great chance the horse has sacroiliac pathology; when less than three are present, sacroiliac pathology is far less likely. This positive result gives a good indication of where to look, and ultrasonography of the dorsal sacroiliac ligaments is the first step in imaging. When clear abnormalities are found, the diagnosis of dorsal sacroiliac ligament pathology is made. Most often, the abnormalities are much more evident on one
side when comparing images from left and right, preferably in split screen. This does not exclude sacroiliac joint pathology, however, and other imaging modalities are needed to establish the condition of the joints. In the author’s experience, however, less than 5% of the total case load of sacroiliac pathology involves the sacroiliac joints when ligament pathology is present.
The dorsal sacroiliac ligaments are easily accessible for imaging when the anatomy of the ligaments is understood. For this reason, ultrasonography is the tool of choice. A 10-12 Mhz linear probe is preferable for imaging the ligaments. The attachment of the dorsal sacroiliac ligament is onto the cranial aspect of the tuber sacrale and to the distal aspect of the dorsal processes of the sacral bone. This means the ligaments are converging a bit when going more caudally as well as having a slight angle moving from tuber sacrale to sacral bone. The fibrillar aspect of the ligament, in general, makes a 4–7 degree angle with the median and a 4–10 degree angle with the horizon. This depends on the angle of the pelvis in a particular horse and how much the horse is standing under its body with its hindlegs, which one has to take into account when imaging to avoid artifact due to off-angle beam (see Figure 1). Preparation of the skin includes clipping with a 40 blade, cleaning, and degreasing as often this region of the skin is quite greasy, which will inhibit good contact with the probe and will strongly limit image quality. Leaving a piece of water-saturated paper towel on the clipped area for 10 minutes after clipping will moisturize the skin and assist in obtaining quality images. As multiple images are taken, it is best to put the images of the left and right ligament in a split screen setting, so comparation is quite easy (see Figures 2 and 3). I advise taking at least three longitudinal images, one of the attachment site to the tuber sacrale, one of the core portion of the ligament, and one of the attachment to the dorsal process of the sacral bone at S1 to S5. In larger horses, you might need more longitudinal images. For sagittal imaging, I would make images at the same areas where the longitudinal images were taken, to be sure that observed abnormalities in one direction are supported by similar findings in the 90-degree offset image. For the experienced imager, this will take about 10 minutes; for less experienced ultrasonographers, it might take up to an hour to obtain images of diagnostic value, so do not give up too soon when initial imaging is challenging.1
Figure 4. Longitudinal images of the core portion of the DSL. On one, there is a clear loss of definition of orientation of fibril pattern, which is indicative of older chronic desmopathy or scar tissue formation. On two, there’s a clearer, fibrillar pattern; the bottom portion seems more compact than the upper portion, indicative for edema within the fibrils. Image courtesy of Dr. Rob van Wessum.
14 The Practitioner
Pathology of the ligaments is assumed to be present when there is a clear disruption of fiber pattern with layers of fluid in between fibrillar layers and/or the bone contour at the attachment sites or loss of definition and fibrillar pattern in the core portion of the ligament. Clear pathology is nearly always much more obvious unilaterally, which is supported by my own experiences as well by Tomlinson et al.2
Issue 3 • 2020
work, such as hand walking or work in a hot walker or treadmill, is instituted as soon as possible.
Tissue-related Specifics for Rehabilitation
In general, soft tissues that comprise joint structures need a quick return to restrained or limited mobility soon after initial treatment for inflammation has begun, typically this is within one week. This is vital to preserve cartilage health and prevent contracture of peri-articular structures. Total rehabilitation time to resumption of full work can be as short as four to six weeks. Length of rehab is dictated by the specific nature of each injury, with injuries to the collateral ligaments being an exception. Such injuries require prolonged rehabilitation and a much more gradual return to work, similar to other tendinous structures described below.
Figure 5. Longitudinal image of the core portion of the ligament (in between attachments to TS and sacral bone) with some edema in between the fibrils (right) and normal appearance on the left. Image courtesy of Dr. Rob van Wessum.
In my experience, acute injury is more often observed at the attachment to the tuber sacrale, while more chronic changes are seen in the core part of the ligament as well as the attachment to the sacral bone. When more chronic changes are seen at the attachment to the sacral bone, these older, chronic fibrillar changes might have been activated by overstretching these structures in a later stage; edema can also be observed in the layers of the adjacent muscles in the sacral region. Often, edema is even visible when observing the clipped region at the sacral bone area. With chronic changes, the contralateral ligament often shows less echogenicity with normal fiber pattern. This is a sign of inactivity atrophy; and it is often seen in cases with a long presence of symptoms.
Treatment and Rehabilitation
Initial treatment depends on the severity of symptoms. When clear signs of inflammation are visible, like layers of fluid or clear areas of increased blood flow, an anti-inflammatory medication might be needed. Because of the low metabolism in ligament structures, I always go for at least four weeks of low dosage medication of phenylbutazone (1g BID for a 1350lb horse) or fibrocoxib. Cooling the affected region with an icepack for at least 45 minutes, at least once a day, after a walk is part of our standard protocol. An adjusted sheet with a homemade pouch for the icepack is helpful. I often use a bag of frozen peas as an icepack as they are very cost effective and easy to adapt to the surface.
Principals of Rehabilitation
Most recent developments in human rehabilitation are focused on early mobilization of the injured area soon after injury.12,13 Only with a fracture, a complete rupture of tendon or ligament, or major wounds, is strict immobilization still supported. A similar approach has been advocated for rehabilitation in horses. Periods of (stall) rest are now often accompanied with specific exercises or manipulations (i.e. passive mobilization of joints) and controlled WWW.FAEP.NET |
Injuries with bone involvement and periostial pathology, in general, need an intermediate amount of time for recovery. Bone turnover is a gradual but constantly occurring process and a rehabilitation program for these tissues will take a period of six weeks to three months depending on the severity of injury. Tendon and ligament tissue need a much longer period of (very) limited mobilization, with the total period of rehabilitation covering four to six months, at least. These structures are relatively avascular and composed of dense connective tissues whose function is to transmit tensile forces. Repair tissue is inelastic and requires time to remodel and regain tensile strength before it can withstand the rigors of regular work. For joint mobilization, passive mobility exercises are useful. A handler can make a horse move its spine by offering it a treat (â€œcarrot reachesâ€?) and adjust the range of motion of the allocated joints by making the horse reach and stretch for the treat in different angles and positions.13 Working in hand, under saddle, or lunging can achieve more dynamic mobilization of joints. Locomotion allows the spine to cycle through a series of precise motions that can be influenced. Specific exercises under saddle have been described to have specific areas of mobilization.14,15,16 These exercises can be used to engage the horse during work to activate specific muscle groups and mobilize different parts of the spine.17,18 Exercises for rehabilitation following tendon and ligament pathology are mostly stretching exercises. Stretching injured tendons and ligaments in a direction parallel to their fiber pattern is known as eccentric exercise; in human medicine, this is now the most common rehabilitation exercise.19 For tendon injuries in the distal extremities, walking on a hard surface, causing a relatively large ground reaction force to reflect from the footing, is a common exercise that, in its execution, is a form of eccentric exercise. The tendons are stretching with every stance phase of every stride.19 Daily hand walking of horses on hard, level ground (ideally pavement) is a simple and effective strategy that is achievable by almost every horse-handler combination. There are two distinct yet common injuries to the sacral region: desmitis of the (dorsal) sacral ligaments and arthritis of the sacroiliac joints. These pathologies are potentially related and may even be present at the same time.9,10 FLORIDAAEP |
@FLORIDA_VMA | The Practitionerâ€‚ 15
For both conditions, rotation of the lumbar spine in correlation with pelvic ventroflexion is the major contributing rehabilitation exercise. The best way to achieve such a position is work on circles. By changing the diameter of the circle from large (65+ feet) to small (15 feet), lateral flexion in the entire spine is enhanced, causing more rotation in the lumbar spine and making the inside hip come lower. This specific motion will have an eccentric effect on the outside (contralateral to the flexion side) ligaments and joint surfaces, while engaging the deeper sub-lumbar and pelvic musculature. Changing direction frequently will help both sides develop evenly. Initially the circle exercises are executed in walk, adding trot and canter in a later stage. While clear desmitis or desmopathy can require up to six months of rehabilitation time before returning to full work, rehabilitation of cases with joint involvement involves riding soon after initial treatment. For sacroiliac arthritis, the typical rehab periods consist of one to two weeks of walk only, two weeks of walk and trot, then another two weeks of adding cantering in before resuming full work. With serious desmopathy, the intervals will be in months; two months of walking on a hard surface in straight lines, one month of just walking, one month of walking and trotting, and then two months in which cantering is introduced gradually, all on circles. Involving the trainer or coach in this program will enhance its effectiveness. In our practice, I have found a greater understanding of the whole concept of rehabilitation when the trainer for the horse and rider felt like a part of the team. Overall compliance in turn was much better. Trainers feel more involved when specific attention is given to the parts of rehabilitation that can utilize the trainer’s skills in having the horse perform its exercises exactly as prescribed. When a horse is taken out of regular work, especially for a long period of time, this can result in a loss of income for the trainer. Bridging this gap by involving these trainers in the decision-making process during the rehabilitation program and offering them a role, assists in maintaining their revenue and ultimately increases satisfaction with the overall results. In our practice, each rehabilitation case is examined every two months until a complete recovery is made. During these recheck exams, the progression of the rehabilitation program is evaluated and adaptations to the program are made based on outcome of the evaluation, the goals of the owner and the trainer of the horse (coming show season), and the general protocol for the injury. This process of recheck exams has several important functions. In my experience, clients love to see the results of their efforts through improved performance during the clinical exam and improved quality of tissue on ultrasonography. This feedback process makes them even more focused on the correct execution of the remainder of the rehabilitation program. Additionally, compliance is reinforced and improved again. From an economic standpoint, a steady case load of recheck exams is an important contribution to the total case load of the practice. 16 The Practitioner
Figure 6. Longitudinal images of the attachment of the DSL to the dorsal processes of the tail bone. The right DSL (left image) is thin and atrophic but with a normal bone contour. The left DSL (right image) is enlarged and has a disrupted fiber pattern with signs of partial rupture of fibrils. On one, the attachment to the dorsal process of the sacral bone; on two, in between two dorsal processes of the sacral bone. Split screen imaging clarifies and enhances the comparison of the ligament condition on the left and right. Image courtesy of Dr. Rob van Wessum.
The repeated contact with owners and trainers at every recheck exam reinforces the veterinary-client-patient relationship. For this reason, after every recheck exam, I sit down with the involved parties for a 10-15 minute “progression meeting” to discuss the outcome of the exam and to describe the next phase of the rehabilitation program. During this meeting, the owner, trainer, and any additional caregivers are allowed to communicate any questions or concerns they might have, and there is ample time to address them. A recent study in the Netherlands among higher level dressage riders showed these riders feel a lack of communication and cooperation between their veterinarian and the other caregivers for the horse (physiotherapist, farrier, saddle fitter, and coaches).21 Offering a rehabilitation program, especially one that gets other caregivers involved in the process, has evolved our practice and provides our clients an opportunity for a “holistic” approach that is valued in this competitive and changing economic climate.
1. Engeli E, Yeager AE, Erb HN, Haussler KK. Ultrasonographic technique and normal anatomic features of the sacroiliac region in horses. Vet Radiol Ultrasound. 2006;47(4):391-403. doi:10.1111/j.1740-8261.2006.00159.x 2. Tomlinson JE, Sage AM, Turner TA. Ultrasonographic abnormalities detected in the sacroiliac area in twenty cases of upper hindlimb lameness. Equine Vet J. 2003;35(1):48-54. doi:10.2746/042516403775467540 3. Goff LM, Jasiewicz J, Jeffcott LB, Condie P, McGowan TW, McGowan CM. Movement between the equine ilium and Issue 3 • 2020
applications. J Orthop Sports Phys Ther. 2007;37(8):434-449. sacrum: in vivo and in vitro studies. Equine Vet J Suppl. doi:10.2519/jospt.2007.2350 2006;(36):457-461. doi:10.1111/j.2042-3306.2006.tb05587.x 4. van Wessum R. How to look for sacroiliac disease during 21. Loomans, JBA, Waaijer, PG, Maree, JTM, van Weeren, PR, Barneveld, A. Quality of equine veterinary care. Part lameness examination: some simple clinical indicators, in 2: Client satisfaction in equine top sports medicine in The proceedings. Am Assoc Equine Pract. 2014;60:244-246 Netherlands. Equine Veterinary Education, 2009;21: 421-428. 5. Jeffcott LB, Dalin G, Ekman S, Olsson SE. Sacroiliac lesions doi:10.2746/095777309X448944 as a cause of chronic poor performance in competitive horses. Equine Vet J. 1985;17(2):111-118. doi:10.1111/j.2042-3306.1985. tb02063.x Dr. Rob van Wessum, 6. Denoix JM, Audigié F, Coudry V. Review of diagnosis and DVM, MS, DACVSMR (EQ), treatment of lumbosacral pain in sport and racehorses, in Cert Pract KNMvD (EQ) proceedings. Am Assoc Equine Pract. 2005;51:366–373 Dr. Rob van Wessum, a native 7. Dyson SJ. Pain associated with the sacroiliac joint region: of the Netherlands, received his a diagnostic challenge, in proceedings. Am Assoc Equine veterinary degree from Utrecht Pract. 2004;51:143–146. University in 1991. He spent the 8. van Wessum R. Evaluation of back pain by clinical next five years as an equine and examination. In: Robinson NE and Sprayberry KA, eds. canine practitioner in a private practice in Weesp. Current therapy in equine medicine. St. Louis, MO: Saunders Elsevier, 2009;469–473. In 1996, Dr. van Wessum began his own equine lameness 9. van Wessum R. Sacroiliac disease. In: Robinson NE and clinic specializing in in-depth diagnostics for lameness, Sprayberry KA, eds. Current therapy in equine medicine. St sports medicine, and pre-purchase examinations. The same year, he was also appointed to the Department of Louis, MO: Saunders Elsevier, 2009;483–487. Equine Internal Medicine at the School of Veterinary 10. van Wessum R. Lameness associated with the axial skeleton: Medicine in Utrecht, where he performed research in the pelvis and the sacroiliac region. In: Baxter G, ed. Adam’s sports medicine and electromyography. In 1999, he lameness in horses 7th edition. New York, NY: Wileybecame a Certified Practitioner (Equine) of the KNMvD. Blackwell, 2020 763-783 From 1991 to 2003, he additionally served as the veterinarian for the canine and mounted divisions of 11. Kannus P. Immobilization or early mobilization after an the Police Department of Amsterdam. In the years 1995acute soft-tissue injury?. Phys Sportsmed. 2000;28(3):55-63. 2003, he was also active as the veterinarian for the K-9 doi:10.3810/psm.2000.03.775 and mounted units of several regional police forces in the 12. Järvinen MJ, Lehto MU. The effects of early mobilisation Netherlands as well as the Military Police (Koninklijke and immobilisation on the healing process following Marrechaussee). In 2003, he was appointed as the first muscle injuries. Spor ts Med. 1993;15(2):78-89. director of the Animal Science Center of the Dutch National Police Agency for the mounted and tracker dog doi:10.2165/00007256-199315020-00002 division. Some of his responsibilities included animal 13. Stubbs NC, Kaiser LJ, Hauptman J, Clayton HM. Dynamic forensic cases and the management of all horses and mobilisation exercises increase cross sectional area of dogs for the Dutch police and animal management for all musculus multifidus. Equine Vet J. 2011;43(5):522-529. state events, such as the royal wedding of Prince Williamdoi:10.1111/j.2042-3306.2010.00322.x Alexander and Princess Maxima. 14. Boldt H. Das Dressurpferd. Edition Haberbeck. 1978 Lage In 2005, Michigan State University (MSU) appointed him Lippe, GE. as the lameness and sports medicine expert at the McPhail 15. Heuschmann G. Tug of war: classical versus modern dressage. Equine Performance Center at MSU and became a faculty Trafalgar Square Publishing, North Pomfret, VT. 2007. member in the department of large animal clinical 16. German National Equestrian Federation FN. The principles sciences at the MSU College of Veterinary Medicine. At the end of 2009, Dr. van Wessum started his own sports of riding. Half Halt Press. 1997. medicine clinic in Mason, Michigan. In 2015, Dr. van 17. Steinbrecht, G. The gymnasium of the horse. Xenophon Press. Wessum became board certified by ACVSMR. 1995. 18. Stodulka R. Medizinische Reitlehre. Parey Verlag. 2006. To honor his background in law enforcement in the Netherlands and serve his community in the U.S., Dr. van 19. Alfredson, H. The Chronic Painful Achilles Tendon:Basic Wessum has been a special deputy of the Ingham County Biology and Treatment-Results of the New Methods of Sheriff’s Office since November 2013. Eccentric Training and Sclerosing Therapy. In: Tendinopathy in Athletes, Woo, LY, Renstrom FH and Arnoczky SP, He and his wife Kimberly, an ACVS diplomate, live on a 170-183,Blackwell Publishing, Malden, Mass. 2007 farm in Mason and enjoy life with horses, both in hobby and professional life. 20. Whittaker JL, Teyhen DS, Elliott JM, et al. Rehabilitative ultrasound imaging: understanding the technology and its
@FLORIDA_VMA | The Practitioner 17
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@FLORIDA_VMA | The Practitioner 19
ULTRASOUND TISSUE CHARACTERIZATION SARAH PLEVIN | BVMS, MRCVS, CVA, DABVP, DACVSMR, RCVS SPECIALIST
Overstrain injuries to the superficial digital flexor tendon (SDFT) are amongst the most common musculoskeletal injuries for all athletic equine disciplines but account for a significant amount of wastage in the Thoroughbred (TB) racehorse.1 Treatment options are numerous and varied, but all have a couple of things in common: time out of training, expense, and no guarantee of success. It makes sense then, that prevention of injury should always be the goal. Failing that, a method to optimally guide rehabilitation is needed. Unfortunately, limitations of current imaging diagnostics have restricted their use for accurately monitoring the tendon. However, a new ultrasound technology, called ultrasound tissue characterization (UTC), may get us one step closer to achieving the goals of injury prevention and optimal rehabilitation.
WHAT WOULD THE IDEAL TENDON IMAGING MODALITY ALLOW US TO DO? • Monitor the effects of exercise on the tendon • Early detection of overstrain injuries • Be able to stage the lesion – i.e. determine the level of degenerative change within the tendon structure • Fine tune therapy • Guide rehabilitation
WHY ARE TENDON INJURIES SO TRICKY? • Normal healthy tendon is made up from aligned organized tendon bundles. Deterioration of this structure ranges on a spectrum from complete disruption (core lesion) to more minor changes, but all affect the ability of the tendon to function optimally. • Degenerative changes within the tendon matrix are not uniform – meaning that not all overstrain injures to the SDFT are represented by the same level of deterioration or structural change. Figure 1: Functionally normal, healthy aligned tendon bundles. Image courtesy of Hans van Schie.
20 The Practitioner
Figure 2: On the left is a completely normal tendon, and on the right is one with an extensive scar. The scar contains no normal structure, but, on the conventional greyscale image, lots of echoes can still be seen. It is important to realize that there is often little relationship between grayscale and structure, that mess generates echoes too and that a 2D image cannot fully represent a 3D structure. Image courtesy of Hans van Schie.
• This means there is not a one size fits all pathology or diagnosis and, therefore, there cannot be a cureall treatment. • Most tendon injuries have a sneaky onset with tendon degeneration developing initially without clinical signs. Often by the time a problem is recognized, tendon matrix degradation has already begun. • Staging the structural integrity of the tendon or classifying the extent of structural deterioration present is, therefore, imperative; not only for optimal therapy selection and appropriate rehabilitation guidance, but also if prevention of injury is to be achieved.
WHY ISN’T CONVENTIONAL ULTRASOUND ENOUGH? • Unfortunately, although conventional ultrasound has historically been used to evaluate equine tendons, limitations have restricted its ability to accurately monitor tendon structure, predict injury, or guide rehabilitation.2 • Clinical improvement is usually not accurately correlated with changes in imaging status using conventional ultrasound, especially in the later stages of healing, with conventional ultrasound not demonstrating enough sensitivity to determine the type of tendon tissue under investigation.3 Issue 3 • 2020
• Although conventional ultrasound can easily demonstrate the presence of a core lesion when it first appears, by approximately two months post injury its capacity to provide information regarding the health of the tendon is limited. The ability of conventional B mode ultrasound to reliably evaluate and monitor the SDFT following the initial acute period is restricted by many factors including: its inability to accurately interpret the integrity of the underlying tendon tissue; its reliance on operator skills and the inherent lack of ability of a 2D ultrasound image to fully decipher a 3D tendon structure (Figure 2).4
WHAT IS ULTRASOUND TISSUE CHARACTERIZATION? Ultrasound tissue characterization is a relatively new technique intended to alleviate some of the problems encountered with conventional ultrasound by improving objective tendon characterization. It does this by standardizing instrumental settings, by providing a 3D reconstruction of the tendon, and by classifying and then quantifying tendon tissue into one of four color-coded echo types based on the integrity of the tendon structure.5 It can assess, in detail, the structural integrity of the tendon; it can discriminate a variety of pathological states and it is sensitive enough to detect the effect of changing loads on the tendon within days. 6,7
remodeling and adapting tendon or inferior repair. Red (Type III echoes) represents fibrillar tissue (the smaller basic unit or building block of tendon). This echo type can represent partial rupture of tendon where they reflect breakdown of normal structure, or they can represent initial healing as the tendon begins to rebuild. Black (Type IV echoes) are areas of cells or fluid and represent core lesions where no normal tendon tissue exists. Type I and II echoes are generated by structural reflections from larger structures (such as intact fibers), while Type III and IV are ‘interfering echoes’ from smaller entities below the limits of spatial resolution (Figure 3).5
HOW IS ULTRASOUND TISSUE CHARACTERIZATION CURRENTLY USED? The aim of ultrasound tissue characterization is not to replace conventional ultrasound but, on the contrary, it is recommended to perform an evaluation with both conventional B mode ultrasound and ultrasound tissue characterization to achieve a complete picture of tendon health. Currently, it is used successfully in elite human athletes, such as NBA and soccer players, to monitor the health of their tendons (Achilles tendon and patellar tendons) and to guide exercise regimens post injury.8 In the equine field, it is used predominantly in elite sport horses in Europe, as a part of routine maintenance evaluations to direct exercise, to monitor tendon health, and guide rehabilitation following an injury.
Figure 3: Color-coded, ultrasound tissue characterization echo types representing the stability of echo pattern over contiguous images related to tendon matrix integrity. Image courtesy of Hans van Schie.
WHAT DO THE COLORS MEAN? Ultrasound tissue characterization algorithms quantify the continuity of echopatterns over contiguous images by analyzing the intensity and distribution of relative grey levels of corresponding pixels. Green (Type I echoes) are normal, well aligned, and organized tendon fascicles and at least 85-90% of this echo type should be found in a healthy tendon (SDFT). Blue (Type II echoes) are areas of wavy or swollen tendon fascicles. They can represent
Figure 4: Ultrasound tissue characterization tracker frame with attached ultrasound probe and built in standoff. Image courtesy of Hans van Schie.
@FLORIDA_VMA | The Practitioner 21
structural composition of the tendon), and for quantification of tendon matrix integrity (Figure 7). The color-coded echo types provide semi-objective information regarding the integrity of the tendon matrix and reflect the underlying tendon health. Ultrasound tissue characterization can discriminate between healthy normal tendon, adaptive/remodeling tendon, and injured/healing tendon, often in cases where conventional ultrasound appears unremarkable (Figure 8). The key to this technology is to perform successive evaluations. This allows comparison of differences in tendon structure between scans. Such consecutive examinations, along with clinical data and history, allow veterinarians to determine if a tendon is static, adaptive, healing, or degenerating. This information enables changes in training intensity to be made accordingly (Figure 9).
Figure 6: The stacking-up of regular transverse ultrasound images to create a 3D rendition of the tendon. Image courtesy of Hans van Schie. Figure 5: Ultrasound tissue characterization machine positioned over the SDFT. It is held with gentle, steady pressure in this position for the 45 seconds it takes for the probe to move down the tendon and collect images. Horses need to stand still with all four limbs fully weight-bearing during this time. Image courtesy of Hans van Schie.
HOW DOES IT WORK? UTC consists of a standard linear array ultrasound probe mounted onto a motorized tracking device with a built-in standoff pad. Due to the sensitivity of the equipment, meticulous skin prep is required, and limbs typically need to be clipped to obtain good quality images (Figure 4). The probe moves non-invasively and automatically down the tendon from proximal to distal over a 12 cm scanning distance, which takes approximately 45 seconds (Figure 5). As it does so, transverse images are captured at regular distances and stored in real time in a high capacity laptop for processing. Images are automatically recorded every 0.2 mm to generate a 3D tendon volume made up of 600 images. This precise spatial ‘stacking’ of images is simply not possible to achieve with conventional ultrasound and is fundamental to the ultrasound tissue characterization technology (Figure 6). The tendon volume can subsequently be used for visualization of the tendon in 3D, for tissue characterization (to determine the
22 The Practitioner
Figure 7: Grey scale and colored images of the tendon in transverse, longitudinal, coronal, and 3D coronal. To generate the picture in color, the computer classifies and quantifies tendon structure into one of four color-coded echo types representing structural integrity. Image courtesy of Hans van Schie.
Figure 8: The image on the left shows a conventional, grey scale ultrasound image that is unremarkable. Conversely, the image on the right depicts an ultrasound tissue characterization image of the same tendon and shows an area of suspected injury, see red area denoted by the arrow. Image courtesy of Hans van Schie.
Issue 3 • 2020
Within 6 months substantial matrix degradation, initially without clinical signs. Figure 9: Image from an elite show jumper depicting tendon matrix degradation prior to clinical signs. To the left, the ‘normal’ SDFT scanned while training out of season in light exercise. Five months later, at the start of the season the horse showed no clinical signs, but ultrasound tissue characterization images already showed a mild increase in Type II (blue) and Type III (red) echoes. This tendon is in a reactive phase, which can be reversible when managed appropriately. Despite warning, the rider continued full training. Six weeks later: there is now a striking increase in Type II (blue), Type III (red), and Type IV (black) echoes. The tendon matrix is now in a degenerative phase. There are still no clinical signs and the rider continues competing. Six weeks later, after a competition, the horse now has clinical signs and there is a ‘rupture.’ This pre-clinical information has the potential to provide opportunity for early intervention and a change in exercise level prior to clinical injury. Research is ongoing to validate any predictive capabilities this technology may have and to develop optimal evaluation programs. Preliminary research has shown that while an acute increase in Type II echoes may be reversible within four days, an increase in echo Type III and IV may not be reversible within that time frame and may take 4-12 weeks, if reversal happens at all. Image courtesy of Hans van Schie.
• In most cases, the limb will need to be clipped to obtain diagnostic images. • Horse and operator need to be very still – even the slightest movement can cause erroneous results. • It is advisable to perform three scans of each tendon to reduce the likelihood of movement artifact in any single scan. • Training is needed not only for image acquisition but also for image interpretation. There is an intense and steep learning curve undertaken by the user in order to allow the technology to perform optimally.
RESEARCH As ultrasound tissue characterization semi-quantifies tendon structure, it is an ideal research tool to objectively assess different rehabilitation modalities by monitoring tendon integrity. Published equine research has reported correlation of ultrasound tissue characterization echo types with histological studies. Ultrasound tissue characterization was found to be able to distinguish between different tissue types (normal, granulation, and fibrotic tissue), where basic grey level statistics could not.9,10 Numerous, peer-reviewed research studies exist documenting the ability of ultrasound tissue characterization to evaluate and monitor tendon both in human and equine athletes.5,7,11,12 Ultrasound tissue characterization has been reported to be highly reproducible with both inter and intra-observer agreement levels being remarkably high.7,10,11
A normal and transient response of tendons to load application has been suggested in basic scientific research. In vitro and in vivo studies have shown the expression of anabolic and catabolic proteins to change within hours of loading and then return to baseline within 72 hours.12, 13 However, the ability to detect such subtle changes in tendon structure in response to exercising loads has not been possible using conventional imaging and this makes the ultrasound tissue characterization research in both humans and horses extremely exciting. Ultrasound tissue characterization has been used to detect these short-term temporal responses to load in the Achilles tendon of human athletes and in the superficial digital flexor tendon of racehorses. In both species, a loss of aligned fibrillar structure was observed 48 hours after maximal load with baseline levels returning 3-4 days later. On UTC images, these changes were documented as a decrease in Type I echoes (normal and aligned tendon bundles), an increase in Type II echoes (swollen and wavy bundles), and a constant level of degenerative indicators such as Type IV echoes.7,12 In both studies, all cases consisted of clinically normal individuals with no evidence of clinical decline or degenerative change on UTC examination and all changes were documented to be reversible in nature. For these reasons, the transient increase in Type II echoes, in response to increasing loads, was considered adaptive rather than degenerative, with both authors citing an increase in water content as a possible reason for the transient change in echo types.14
@FLORIDA_VMA | The Practitioner 23
Figure 10: Suggested timeline of repair visualized using ultrasound tissue characterization. As healing progresses, the proportion of red and black echoes decrease and blue and green increase. Image courtesy of Hans van Schie.
ADDITIONAL RECENT EQUINE RESEARCH A second Thoroughbred (TB) racehorse study performed by our practice, reported a reference range for normal juvenile TB SDFT ultrasound tissue characterization values and demonstrated changes in SDFT characterization over the first six months of training.11 It demonstrated the ability of ultrasound tissue characterization to non-invasively monitor physiological changes in maturing TB tendon. The study highlighted differences between tendons in the dominant versus nondominant limbs and, subsequently, tendon adaptations to loading during this early training period.11
HOW CAN THIS TECHNOLOGY BE USED IN THE RACEHORSE? Rehabilitation: It is widely accepted that the complete removal of load on tendons post-injury is deleterious for tendon health, and complete removal of exercise is only advocated in the very acute inflammatory phase following a tendon injury. Appropriate, progressive loading of the tendon is desired to stimulate remodeling and healing, and this is where ultrasound tissue characterization is proving to be most useful. Typically, an exercise regimen post-injury follows a generic format using clinical signs, conventional ultrasound, and the calendar as the only methods of assessment. However, as most early tendon degradation is silent and conventional ultrasound struggles to decipher the integrity of the tendon, unless a lesion is present, it has traditionally been difficult to precisely guide exercise regimens during rehabilitation. By providing real time information regarding the integrity of the tendon matrix, ultrasound tissue characterization allows veterinarians to take advantage of the limited window of opportunity that exists for appropriate tendon remodeling after injury. By mapping the ultrastructure of the healing tendon, and its remodeling response to exercise at each step in the
24 The Practitioner
rehabilitation regimen, it allows optimization of the most vital tool we have in our rehabilitation arsenal: exercise. While ultrasound tissue characterization technology is groundbreaking in its ability to non-invasively evaluate tendon structure and aid in tendon rehabilitation, it must be remembered that once a tendon is injured, it will always be inferior to uninjured tendon. Scar tissue will always be scar tissue. So, while green echoes are the goal (normal and aligned tendon bundles), and represent success for a rehabilitating tendon, they still just represent scar tissue, albeit aligned appropriately and in the best state to combat the strains of training and competition. This technology doesn’t remove the risk of reinjury in the injured tendon, and it doesn’t provide information regarding the biochemical make up of the lesion or the tendon. It simply tells us if the tendon is structurally normal and, by doing so, it improves our ability to monitor and guide healing. It provides veterinarians the best opportunity, currently, to adjust and tailor exercise regimens for the specific needs of the individual tendon and horse, allowing for informed decisions regarding the tendon’s capacity for performance (Figure 10).
THE FUTURE Injury Prediction? While the current scientific literature seems to support the use of ultrasound tissue characterization to guide rehabilitation and monitor the effects of changing loads on the tendon during training, numerous anecdotal accounts from clinical practice, both human and equine, also report the ability of ultrasound tissue characterization to warn of impending injury. Although, human research is currently ongoing to confirm this, equine research is needed to determine the specifics of any predictive capabilities the technology may have. For now, however, the evidence suggests that ultrasound tissue characterization can reliably and accurately be used to help guide rehabilitation of injured tendons, in both humans and horses, with the potential for a more successful return from injury.
Issue 3 • 2020
References: 1. Schie, H. T. V., & Bakker, E. M. (2000). Structure-related echoes in ultrasonographic images of equine superficial digital flexor tendons. American journal of veterinary research, 61(2), 202-209. 2. Gillis, C., Meagher, D., Cloninger, A., Locatelli, L., & Willits, N. (1995). Ultrasonographic cross-sectional area and mean echogenicity of the superficial and deep digital flexor tendons in 50 trained thoroughbred racehorses. American journal of veterinary research, 56(10), 1265-1269. 3. Khan, K. M., Forster, B. B., Robinson, J., Cheong, Y., Louis, L., Maclean, L., & Taunton, J. E. (2003). Are ultrasound and magnetic resonance imaging of value in assessment of Achilles tendon disorders? A two-year prospective study. British journal of sports medicine, 37(2), 149-153. 4. Gillis, C. L., Meagher, D. M., Pool, R. R., Stover, S. M., Craychee, T. J., & Willits, N. (1993). Ultrasonographically detected changes in equine superficial digital flexor tendons during the first months of race training. American journal of veterinary research, 54(11), 1797-1802. 5. Van Schie, H. T. M., de Vos, R. J., de Jonge, S., Bakker, E. M., Heijboer, M. P., Verhaar, J. A. N., Tol, J.L., & Weinans, H. (2010). Ultrasonographic tissue characterisation of human Achilles tendons: quantification of tendon structure through a novel non-invasive approach. British journal of sports medicine, 44(16), 1153-1159. 6. Docking, S. I., Rosengarten, S. D., & Cook, J. (2016). Achilles tendon structure improves on UTC imaging over a 5‐month pre‐season in elite Australian football players. Scandinavian Journal of Medicine & Science in Sports, 26(5), 557-563. 7. Docking, S. I., Daffy, J., Van Schie, H. T. M., & Cook, J. L. (2012). Tendon structure changes after maximal exercise in the Thoroughbred horse: use of ultrasound tissue characterisation to detect in vivo tendon response. The Veterinary Journal, 194(3), 338-342. 8. Antf lick, J., & Myers, C. (2014). Management of tendinopathies with ultrasound tissue characterisation. SportEX Medicine, (61). 9. Schie, H. T. V., Bakker, E. M., Jonker, A. M., & Weeren, P. R. V. (2003). Computerized ultrasonographic tissue characterization of equine superficial digital flexor tendons by means of stability quantification of echo patterns in contiguous transverse ultrasonographic images. American journal of veterinary research, 64(3), 366-375. 10. van Schie, H. T., Bakker, E. M., Jonker, A. M., & van Weeren, P. R. (2001). Efficacy of computerized discrimination between structure-related and non–structure–related echoes in ultrasonographic images for the quantitative evaluation of the structural integrity of superficial digital flexor tendons in horses. American journal of veterinary research, 62(7), 1159-1166.
11. Plevin, S., McLellan, J., van Schie, H., & Parkin, T. (2019). Ultrasound tissue characterisation of the superficial digital flexor tendons in juvenile Thoroughbred racehorses during early race training. Equine veterinary journal, 51(3), 349-355. 12. Rosengarten, S. D., Cook, J. L., Bryant, A. L., Cordy, J. T., Daffy, J., & Docking, S. I. (2015). Australian football players’ Achilles tendons respond to game loads within 2 days: an ultrasound tissue characterisation (UTC) study. British journal of sports medicine, 49(3), 183-187. 13. Maeda E, Fleischmann C, Mein CA, et al. (2010) Functional analysis of tenocytes gene expression in tendon fascicles subjected to cyclic tensile strain. Connect Tissue Res. 51, 434-44. 14. Cook J.L. & Purdam C.R. (2009) Is tendon pathology a continuum? A pathology model to explain the clinical presentation of load‐induced tendinopathy. Br. J. Sports Med. 43, 409– 416.
Sarah Plevin, BVMS, MRCVS, CVA, DABVP, DACVSMR, RCVS specialist Dr. Sarah Plevin is a sports medicine specialist and partner at Florida Equine Ve t e r i n a r y A s s o c i a t e s . Originally from the United Kingdom, she graduated from Glasgow Veterinary School in Scotland. After, c o mpl e t ing a s urg i c a l internship in Ocala, Florida, she went into general practice for a couple of years before undertaking a lameness fellowship and then pursing specialist qualifications. She is double boarded with the American Association of Veterinary Practitioners and the American College of Veterinary Sports Medicine and Rehabilitation. Dr. Plevin has also attained status as an equine sports medicine specialist from the Royal College of Veterinary Surgeons and is certified in veterinary acupuncture. Currently, Dr. Plevin devotes most of her time to clinical research and leads the research department at FEVA, where her focus is on preventing injuries in the juvenile TB racehorse. She has presented her work both nationally and internationally. Outside of work, Dr. Plevin is a keen swimmer and enjoys all outdoor activities. She is married with three young children and enjoys traveling extensively throughout the world with her family.
@FLORIDA_VMA | The Practitioner 25
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Published by the Florida Association of Equine Practitioners, an Equine-Exclusive Division of the FVMA