Osteomyelitis of the olecranon in

Peter Briston, Cambridge Vets

Osteomyelitis of the olecranon in an alpaca

Abstract

A four year old, male alpaca was seen for a puzzling but severe lameness in the right foreleg. After fruitless trial treatments, radiography revealed a focal osteomyelitis of the olecranon. A course of weekly sodium iodide intravenous infusions resulted in both radiographic and clinical improvement.

History

In April 2020 I was called out to see a four year old male alpaca (65kg) called Nestle, who presented with acute onset lameness of the right foreleg. On examination, he was 5/5 lame. The focus of pain was hard to localize, but no crepitus nor heat nor swelling was palpated, and there were no problems with flexion of all joints. The owner reported there had been a bit of social jostling in the boys’ group, so we treated for a sprain with a subcutaneous injection of meloxicam (Metacam, Boehringer) at 1mg/kg. Telephone feedback indicated a mild improvement, then regression to 5/5 lame.

Subsequent visits failed to find a definitive cause of the lameness, but with a suspicion of some heat and swelling around the fetlock, a course of amoxicillin (2 x 1500mg q 48h, Betamox LA, Norbrook) was prescribed with mild improvement. At this point radiographs were suggested but declined. An 8 day course of oxytetracycline (600mg q 48h, Engemycin, MSD) was prescribed with no improvement, and finally a Hail Mary shot of dexamethasone (Dexa 0.2, Phoenix) which actually made a big difference, but only for a few days.

Referral or x-rays were advised more strongly at this stage, with an involved discussion on what could be achieved and what might be diagnosed, to address owner reluctance.

Differential diagnoses

Ð Green stick fracture Ð Salter Harris Fracture Ð Infection (soft tissue or joint) Ð Osteosarcoma Ð Tendonitis Ð Synovitis

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Three weeks after the original visit, digital radiographs were taken by a colleague who is an equine clinician with an interest in imaging, access to cool toys, and the bravery to branch out into camelids!

Her second opinion lameness work-up identified pain in the right elbow, and radiographs of this joint revealed a radiolucent osteolytic lesion in the olecranon.

Diagnosis Osteomyelitis

Treatment

A literature search revealed that Ceftiofur was the most common antibiotic prescribed for osteomyelitis in camelids in the Americas, so a course of Excenel (Zoetis) at 6.6 mg/kg daily was undertaken. After 12 days, there was no improvement, so I changed to what I would have used in cattle - intravenous Sodium Iodide weekly, 5g in 50ml saline.

The first treatment was the most challenging. The fibre over the neck was very dense and hard to clip, the alpaca was hard to restrain, the angle was awkward on the shearing table, then he crushed on the floor, the jugular was hard to locate, and finally the patient displayed ataxia after the infusion. However, it resulted in a marked improvement in terms of lameness.

We opted to sedate the patient for the second treatment, with an I/M injection of 40mg Xylazine (Xylazine 2%, Phoenix) mixed with 100mg Ketamine.

Three weeks after the original visit, digital radiographs were taken by a colleague who is an equine clinician with an interest in imaging, access to cool toys, and the bravery to branch out into camelids!

This went much better, and using an extension set on the syringe allowed a degree of movement when administering the sodium iodide. Lameness improved to 3/5.

The third treatment we improved the procedure again by reversing sedation with 150mg tolazoline (Tolazine) I/V, but with no further clinical improvement.

On a six day follow-up after the fourth treatment, the owner again reported no further improvement, so we opted to repeat radiography rather than treatment. A series of conscious x-rays were taken (medio-lateral, dorso-palmar, and mediocranialdorsolateral oblique) to check for a sequestrum, and a repeat clinical exam performed.

The x-rays revealed no sequestrum or fracture. The osteolytic lesion had in fact largely resolved. This fitted with the clinical assessment of vastly reduced pain response to manipulation of the elbow joint and pressure application to the olecranon. The owner also believed he had improved a bit in lameness as he had trotted in on four legs with an occasional hop on three.

Reassured at this stage, we opted to monitor, and focus on rebuilding the musculature which had atrophied over the chronic duration of lameness.

Over the next few weeks, the owner reported he continued to improve gradually.

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Discussion

This case may not be groundbreaking in any one sense, but it brought together multiple learnings:

The value of a second opinion. My colleague’s lameness examination was subtly different to mine, probably because she is an equine clinician, whereas I deal with a narrower aetiological bundle of lameness in cattle and sheep.

The medical advantages of following a logical diagnostic work-up, and the challenge of persuading clients of its value when, in and of itself, it won’t “fix” the problem. I suspect many of us fall into the “treatment trials” trap not because we are ignorant or lazy but because we have been beaten down by decades of fruitless discussions with owners. Farm vets in particular often have to perform miracles with no ready access to full blood analysis / histopathology / imaging data, and it felt good to “do it right” (eventually) here!

The cause of the osteomyelitis in this case was a bit of a mystery. The owner at one point did recall the animal getting its leg caught in a gate gudgeon. This trauma may explain the site of the lesions. Most osteomyelitis is located in the mandible, probably caused by Actinomyces or Fusobacterium (Fowler, 1989).

Rousseau et al (2013) reviewed 36 records of cases of osseous sequestration in camelids, and found that only 7 were associated with trauma; the majority are proposed to be sequelae of osteomyelitis as a result of haematogenous spread from a soft tissue infection. They found surgical sequestrectomy and debridement had good results, but curettage in this case was rejected due to the anatomical site, cost and potential complications. No penetrating wound was found in this case, but blunt trauma may have compromised osseous vascular supply or caused local haemorrhage, with subsequent lowered redox allowing bacterial multiplication.

Treatment with antibiotics was frankly a failure, but good old undervalued sodium iodide had an immediate effect, if not complete resolution. This is a treatment I use with good results for septic pedal arthritis in cattle. Recommended dose rates are 70mg/kg in a 10-20% solution for cattle (Parkinson et al, 2019) and 40-60mg/kg in 50-100ml for alpacas (Vaughan, 2017); in this case the former dose was utilized as 50ml of a 10% solution.

The main challenge here was administration. With such long necks, restraint was best achieved with

reduced stress by sedation (xylazine and ketamine I/M) followed by reversal with tolazoline I/V. The jugular can be hard to locate in South American Camelids; the jugular vein is medial to the sternomandibularis muscle and to the transverse processes of the cervical vertebrae, and the carotid artery is close to the jugular vein, for much of its course down the neck (Fowler, 1989). In addition, there is no obvious jugular groove and the skin is thick and the fibre is thick.

I prefer High Neck Venipuncture, with access just below the mandibular ramus (here the vein is quite superficial and separated from the carotid by the omohyoideus muscle) with a 1” 16g needle. For Low Neck guidelines, refer to Fowler (1989). The extension set gave a degree of flexibility. The ataxia after the first treatment may have been due to IV infusion of sodium iodide not being slow enough, or to stress.

Although there has been a move away from “omnicompetence” within the profession (a lofty ideal at best, a minefield for litigation at worst), many of us still deal with multiple species, and South American Camelids present an enjoyable opportunity and challenge for this farm vet.

REFERENCES:

Fowler ME. (1989). Medicine and Surgery of South American Camelids, 2nd Edition. Iowa State Press

Parkinson TJ, Vermunt JJ, Malmo J, Laven R (2019). Diseases of Cattle in Australasia 2nd ed - A Comprehensive Textbook, Massey University Press

Rousseau M, Anderson DE, Niehaus AJ, Miesner MD, Nichols S (2013). Osseous sequestration in alpacas and llamas: 36 cases (1999–2010). JAVMA, Vol 243, No. 3

Acknowledgements

Kerri & Neil of Blue Ridge Alpacas

Sharon Jeong BVSc, Cambridge Equine Hospital

Laura Schwartfeger, The Lifestyle Vet

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