Vertebral Columns, Spring 2019 by International Society for the Advancement of Spine Surgery

Vertebral Columns International Society for the Advancement of Spine Surgery

ISASS19

Spring 2019

April 3-5, 2019 Anaheim, CA

Grand Plaza at Anaheim, Home of ISASS19. Cover: Grand Plaza at Anaheim. Credit: Visit Anaheim

In This Issue TDA Are Conventional Indications for Cervical Total Disc Arthroplasty Too Rigid?..................................................................................................... 3 BEST PRACTICES Developing a Pathway to Improve Efficiency in the Hospital and Decrease Hospital Stay...........................................................................6 MIS MIS Options for Pelvic Fixation.............................................................8

Editor in Chief Kern Singh Editorial Board Peter Derman, MD, MBA Brandon Hirsch, MD Sravisht Iyer, MD Safdar Khan, MD Yu-Po Lee, MD Grant Shifflett, MD Sheeraz Qureshi, MD Publisher Jonny Dover

TLIF Maximizing Lordosis with Minimally Invasive TLIF, Part 1: Key Considerations Prior to Cage Placement ............................................. 12 OUTCOMES The Use of PROMIS in Spine Surgery: An Overview of the Existing Literature.............................................................................................. 14

Vertebral Columns is published quarterly by the International Society for the Advancement of Spine Surgery. © 2019 ISASS. All rights reserved. Opinions of authors and editors do not necessarily reflect positions taken by the Society. This publication is available digitally at http://vertebralcolumns.com. ISSN 2414-6277.

Vertebral Columns • Spring 2019

TDA

Are Conventional Indications for Cervical Total Disc Arthroplasty Too Rigid? Grant D. Shifflett, MD Twentieth century surgeon Gathorne Robert Girdlestone famously remarked about his eponymous procedure, “If thine femoral head offends thee, pluck it out and cast it from thee.” As archaic and incredulous as that comment appears today so too might we one day consider our colleagues’ recommendation for a cervical fusion. Cervical total disc arthroplasty (cTDA) emerged from a desire to perform a less destructive procedure on the cervical spine, particularly in young patients, and to avoid the limitations and long-term sequelae of a fusion. The growth of cTDA that we see in many markets today has at least partially been patient driven by the excoriation of the term “fusion” and patients desiring “motion-preservation technologies.” Since its conceptualization and inception, cTDA has emerged as a great clinical option in young patients with one or two level cervical radiculopathy or myelopathy. A growing body of evidence has demonstrated the clinical efficacy of cTDA in terms of both short and long-term outcomes.1-8 In spite of this, anterior cervical discectomy and fusion (ACDF) remains the predominant surgical approach among spine surgeons treating one and two level degenerative pathologies of the cervical spine.9-12 Strict adherence to a set of narrow indications often discourages many

surgeons from identifying potential candidates and incorporating this procedure into their practices. This does not entirely explain the lack of adoption, as several retrospective studies have shown that a large number of patients are candidates for cTDA but their surgeons still perform an ACDF.13,14 This likely stems from an inherent bias against motion preservation technologies, concerns over reports of failures, the familiarity and quality of ACDF outcomes, and lower surgeon reimbursement rates for cTDA. Traditional indications for cTDA include patients age <65 with one or two level radiculopathy or myelopathy, preferably due to soft tissue disc disease over bony stenosis, with minimal spondylosis, including <50% collapse of the disc space and no facet arthrosis, and no kyphosis or instability. For many inexperienced arthroplasty surgeons these criteria can be construed to exclude most patients. Experienced arthroplasty surgeons, however, find these criteria easy to meet and are more interested in the appropriate expansion of these indications rather than fitting patients strictly into these parameters. To date, however, there is limited available data on the expansion of indications for cTDA. Notably, what is the role of cTDA in the treatment of patients with end-stage degenerative disc disease but minimal facet arthrosis? Cervical kyphotic deformities? High-level athletes?

Hybrid surgery? Instability? The preponderance of clinical data supporting improved outcomes as well as evolving evidence on the cost efficiency of this procedure implore us as surgeons to consider the significant value added by an expansion of indications and thus a larger number of cTDA performed nationally. Studies have shown the ability of cTDA to retain segmental motion and preserve motion characteristics.15,16 The potentially protective effect of cTDA for adjacent segment disease has been well-demonstrated in current 7+ year IDE trial data for a number of different artificial discs. These patients were carefully selected to comply with the previously defined inclusion criteria. As a result, patients with high-grade spondylosis were excluded. But is there a role for cTDA in these patients? One study out of Korea looked at moderate (Pfirrmann III) to severe spondylosis (Pfirrmann IV or V) and showed that comparable clinical and radiographic results were attainable.17 It could be argued that the patients who have minimal segmental motion as a result of the spondylosis and therefore are transferring the greatest stresses to adjacent segments might benefit from motion preservation technology; a segment that moves less than five degrees could potentially be taken to 5-10 degrees of motion with a cTDA. In our clinical center’s experience, Vertebral Columns • Spring 2019

patients with advanced degenerative disc disease in the absence of significant facet arthropathy have done well clinically, neurologically, and radiographically over the short term. A prominent clinical question is whether or not the “clock” can be reset on these degenerated levels and how this may be protective of adjacent levels. Biomechanical data and long term clinical and radiographic outcomes are needed to evaluate this theory. The importance of cervical sagittal parameters cannot be overstated when considering anterior or posterior cervical surgery. When deciding the appropriateness of cTDA many surgeons balk when global or segmental kyphosis is identified due to concerns of refractory pain and implant failure. Studies have shown, however, the ability of cTDA to recreate segmental and adjacent level lordosis comparably to ACDF with the added benefit of preserving motion at the index level.18-22 More specifically, Chen et al demonstrated that reducible kyphotic deformities on flexion and extension films can safely be treated with cTDA.18 The kyphosis may be largely attributable to pre-operative clinical symptoms and muscular weakness, which are alleviated by surgery and post-operative physiotherapy resulting in restoration of the sagittal alignment. Techniques such as leaving the cTDA slightly more anteriorly and preserving the posterior longitudinal ligament can be employed to provide additional check reigns to excessive segmental kyphosis and can correct the kyphosis without blocking range of motion. The severity of reducible and certainly irreducible kyphosis that is correctable remains undefined but warrants further investigation. 4

Vertebral Columns • Spring 2019

Hybrid surgery can be defined as a fusion-replacement construct at the time of the index operation or as placement of a cTDA adjacent to a prior fusion. This is the area of cTDA with possibly the greatest level of interest as the need is so commonly encountered clinically. Many patients present with multi-level disease with varying degrees of pathology from one affected level to another and hybrid surgery allows the surgeon to tailor the surgical plan to provide stability where it is needed and preserve motion where appropriate. This avoids the deleterious affects of multi-level fusion surgery on adjacent segments and also complications relating to long constructs such as pseudoarthrosis. Despite all of this, insurance carriers uniformly consider hybrid surgery experimental. Still, the clinical feasibility of this operation has been demonstrated both biomechanically and clinically with fewer adverse effects at adjacent levels, and similar complication profiles and post-operative outcome scores when compared to ACDF or cTDA alone.23-26 The frequency at which hybrid surgeries are still performed is unknown, but the need for further investigation is overwhelming. Available data have established the clinical efficacy of cTDA. The original clinical indications for the procedure were based on expert opinion and were likely too restrictive. Expanding indications are warranted to improve long-term outcomes, minimize the effects of adjacent segment disease, decrease complication profiles, and put an end to the days of endless fusions for patients. Short and long-term patient reported outcomes including radiographic data will be necessary to determine if the indications

can safely be expanded. Key areas of investigation include further research into utilization in older patients, those with more significant spondylosis, kyphosis and instability, professional athletes, greater than two level cTDA, utilization of hybrid surgery, and overall cost-effectiveness.

The importance of cervical sagittal parameters cannot be overstated when considering anterior or posterior cervical surgery. References 1. Burkus JK, Haid RW, Traynelis VC, Mummaneni PV. Long-term clinical and radiographic outcomes of cervical disc replacement with the Prestige disc: results from a prospective randomized controlled clinical trial. J Neurosurg Spine13:308–318 2010. 2. Coric D, Nunley P, Guyer RD, Musante D, Carmody CN, Gordon CR. Prospective, randomized, multicenter study of cervical arthroplasty: 269 patients from the Kineflex|C artificial disc investigational device exemption study with a minimum 2-year follow-up. J Neurosurg Spine15:348–358 2011. (Erratum in J Neurosurg Spine 16:322 2012). 3. Davis RJ, Kim KD, Hisey MS, Hoffman GA, Bae HW, Gaede SE: Cervical total disc replacement with Mobi-C cervical artificial disc compared with anterior discectomy and fusion for treatment of 2-level symptomatic degenerative disc disease: a prospective, randomized, controlled multicenter clinical trial. J Neurosurg Spine19:532–545 2013. 4. Heller JG, Sasso RC, Papadopoulos SM, Anderson PA, Fessler RG, Hacker RJ: Comparison of BRYAN cervical disc arthroplasty with anterior cervical decompression and fusion: clinical and radiographic results of a randomized, controlled, clinical trial. Spine (Phila Pa 1976)34:101–107 2009. 5. MummaneniPVBurkusJKHaidRWTraynelisVCZdeblickTA: Clinical and radiographic analysis of cervical disc arthroplasty compared with allograft fusion: a randomized controlled clinical trial. J Neurosurg Spine6:198–2092007

6. Murrey D, Janssen M, Delamarter R, Goldstein J, Zigler J, Tay B: Results of the prospective, randomized, controlled multicenter Food and Drug Administration investigational device exemption study of the ProDisc-C total disc replacement versus anterior discectomy and fusion for the treatment of 1-level symptomatic cervical disc disease. Spine J9:275–286 2009. 7. Phillips FM, Lee JY, Geisler FH, Cappuccino A, Chaput CD, DeVine JG: A prospective, randomized, controlled clinical investigation comparing PCM cervical disc arthroplasty with anterior cervical discectomy and fusion. 2-year results from the US FDA IDE clinical trial. Spine (Phila Pa 1976)38:E907–E918 2013. 8. Vaccaro A, Beutler W, PeppelmanW, Marzluff JM, High-smith J, Mugglin A: Clinical outcomes with selectively constrained SECURE-C cervical disc arthroplasty: two-year results from a prospective, randomized, controlled, multicenter investigational device exemption study. Spine (Phila Pa 1976)38:2227– 2239 2013. 9. Saifi C, Fein AW, Cazzulino A, Lehman RA, Phillips FM, An HS, Riew KD. Trends in resource utilization and rate of cervical disc arthroplasty and anterior cervical discectomy and fusion throughout the United States from 2006 to 2013. Spine J. 2018 Jun;18(6):10221029. doi: 10.1016/j.spinee.2017.10.072. Epub 2017 Nov 8. 10. Nesterenko SO, Riley LH 3rd, Skolasky RL. Anterior cervical discectomy and fusion versus cervical disc arthroplasty: current state and trends in treatment for cervical disc pathology. Spine (Phila Pa 1976). 2012 Aug 1;37(17):14704. doi: 10.1097/BRS.0b013e31824ee623. 11. Qureshi SA, Koehler SM, Lu Y, Cho S, Hecht AC. Utilization trends of cervical artificial disc replacement during the FDA investigational device exemption clinical trials compared to anterior cervical fusion. J Clin Neurosci. 2013 Dec;20(12):1723-6. doi: 10.1016/j. jocn.2013.03.002. Epub 2013 Aug 22. 12. 12. J Bone Joint Surg Am. 2017 Sep 20;99(18):e99. doi: 10.2106/JBJS.16.01082. Trends in the Treatment of Single and Multilevel Cervical Stenosis: A Review of the American Board of Orthopaedic Surgery Database. Arrojas A1, Jackson JB 3rd, Grabowski G. 13. 13. Asian Spine J. 2011 Dec;5(4):213-9. doi: 10.4184/asj.2011.5.4.213. Epub 2011 Nov 28. The Incidence of Potential Candidates for Total Disc Replacement among Lumbar and Cervical Fusion Patient Populations. Quirno M1, Goldstein JA, Bendo JA, Kim Y, Spivak JM. 14. 14. Spine J. 2008 Sep-Oct;8(5):711-6. Epub 2007 Nov 5. The prevalence of indications and contraindications to cervical total disc replacement. Auerbach JD1, Jones KJ, Fras CI, Balderston JR, Rushton SA, Chin KR. 15. Chang SW, Bohl MA, Kelly BP, Wade C. The segmental distribution of cervical range

of motion: A comparison of ACDF versus TDR-C. J Clin Neurosci. 2018 Nov;57:185-193. doi: 10.1016/j.jocn.2018.08.050. Epub 2018 Sep 7. 16. Auerbach JD, Anakwenze OA, Milby AH, Lonner BS, Balderston RA. Segmental contribution toward total cervical range of motion: a comparison of cervical disc arthroplasty and fusion. Spine (Phila Pa 1976). 2011 Dec 1;36(25):E1593-9. doi: 0.1097/BRS. 0b013e31821cfd47.

two level and hybrid constructs. Spine (Phila Pa 1976). 2015;40:1578–1585. doi:10.1097/ BRS.0000000000001044. [PubMed] 26. Wu B. Comparison of hybrid constructs with 2-level artificial disc replacement and 2-level anterior cervical discectomy and fusion for surgical reconstruction of the cervical spine: a kinematic study in whole cadavers. Med Sci Monit. 2015;21:1031–1037. doi:10.12659/ MSM.892712.

17. Chang Hyun Oh, Do Yeon Kim, Gyu Yeul Ji, Yeo Ju Kim, Seung Hwan Yoon, Dongkeun Hyun, Eun Young Kim, Hyeonseon Park, and Hyeong-Chun Park. Cervical Arthroplasty for Moderate to Severe Disc Degeneration: Clinical and Radiological Assessments after a Minimum Follow-Up of 18 Months: Pfirrmann Grade and Cervical Arthroplasty Yonsei Med J. 2014 Jul 1; 55(4): 1072–1079. Published online 2014 Jun 13. doi: 10.3349/ymj.2014.55.4.1072 PMCID: PMC4075369. PMID: 24954339. 18. Chen Y, Wang X, Lu X, Yang H, Chen D. Cervical disk arthroplasty versus ACDF for preoperative reducible kyphosis. Orthopedics. 2013 Jul;36(7):e958-65. doi: 10.3928/0147744720130624-29. 19. Guerin P, Obeid I, Gille O, Bourghli A, Luc S, Pointillart V, Vital JM. Sagittal alignment after single cervical disc arthroplasty. J Spinal Disord Tech. 2012;25:10–16. doi: 10.1097/ BSD.0b013e31820f916c. 20. Kim SW, Limson MA, Kim SB, Arbatin JJ, Chang KY, Park MS, Shin JH, Ju YS. Comparison of radiographic changes after ACDF versus Bryan disc arthroplasty in single and bi-level cases. Eur Spine J. 2009;18:218–231. 21. Kim SW, Shin JH, Arbatin JJ, Park MS, Chung YK, McAfee PC. Effects of a cervical disc prosthesis on maintaining sagittal alignment of the functional spinal unit and overall sagittal balance of the cervical spine. Eur Spine J. 2008;17:20–29. 22. Pickett GE, Mitsis DK, Sekhon LH, Sears WR, Duggal N. Effects of a cervical disc prosthesis on segmental and cervical spine alignment. Neurosurg Focus. 2004;17:E5. 23. Jia Z, Mo Z, Ding F, He Q, Fan Y, Ruan D. Hybrid surgery for multilevel cervical degenerative disc diseases: a systematic review of biomechanical and clinical evidence. Eur Spine J. 2014;23:1619–1632. doi:10.1007/s00586-0143389-5. [PubMed] 24. Cho BY, Lim J, Sim HB, Park J. Biomechanical analysis of the range of motion after placement of a two-level cervical ProDisc-C versus hybrid construct. Spine (Phila Pa 1976). 2010;35:1769–1776. doi:10.1097/BRS. 0b013e3181c225fa. [PubMed] 25. Gandhi AA, Kode S, DeVries NA, et al. Biomechanical analysis of cervical disc replacement and fusion using single level,

Vertebral Columns • Spring 2019

BEST PRACTICES

Developing a Pathway to Improve Efficiency in the Hospital and Decrease Hospital Stay Yu-Po Lee MD

Between 1998 to 2008, the number of spinal fusions has increased from 174,223 to 413,171 cases in the US.1 Over this time, hospital charges have also increased 3.3 times.1 Despite the high volume of spine procedures, there is substantial variation across facilities.2 There are variations in adherence to evidence-based care processes, operative times, length of stay, costs, patient-reported outcomes, and discharge rates.2 It seems counterintuitive that in this era of information exchange and computer networking, much variability exists from one hospital to the next in a country as advanced technologically as the US. In this context, the present article discusses the process that may improve operative room efficiency and patient discharge. In order to enhance operative and discharge efficiency, the process can be partitioned into pre-operative, operative, and post-operative components. In the pre-operative period, the surgical team can focus on identifying, evaluating, and mitigating risk factors that could delay surgery. The surgical team should identify patients with comorbid conditions that can affect a patientâ&#x20AC;&#x2122;s 6

Vertebral Columns â&#x20AC;˘ Spring 2019

perioperative morbidity and mortality. Conditions that have been identified as perioperative risks for complications include patients with pulmonary, cardiac, and renal conditions.3 Atelectasis is the main cause of pulmonary complications. Atelectasis can be prevented or treated by adequate analgesia, incentive spirometry (IS), deep breathing exercises, mobilization of secretions, and early ambulation. The main reason for post-operative pneumonia is aspiration. Use of tapered or polyurethane cuffs, and selective rather than the routine use of nasogastric tube can decrease chances of aspiration. Cardiac complications are common after non-cardiac surgery. Perioperative myocardial infarction is a serious risk for patients undergoing major surgery. Postoperative arrhythmias are also a frequent cause of morbidity, with atrial fibrillation having specific relevance to the peri-operative period. Postoperative systolic heart failure is rare outside of myocardial infarction or cardiac surgery, but the impact of preoperative diastolic dysfunction and its ability to cause postoperative heart failure can be a major source of postoperative morbidity. Identifying these patients and having a cardiac team monitoring them from the beginning of their hospital visit can be very helpful. Fluid management is also very im-

portant in managing these patients. Postoperative acute kidney injury affects patients after major spine surgery. Preexisting chronic kidney disease is a major risk factor for postoperative acute kidney injury. It carries a substantial risk for postoperative adverse outcomes, as well as long-term mortality and morbidity. To prevent postoperative acute kidney injury, avoiding intraoperative hypotension and hypoperfusion as well as nephrotoxic substances are important. Currently, no efficient pharmacotherapy for prevention or treatment of acute kidney injury is available. In general, goal-directed management protocols have reduced the incidence of postoperative acute kidney injury. Additionally, a restrictive fluid management regimen might reduce organ edema and be beneficial for kidney function, in conditions such as post-renal azotemia. In the management of patients with major medical co-morbidities, having a medicine team that is involved from beginning is important. It may take some discussions with hospital administration, but having a dedicated spine medicine team may be just as beneficial as having a dedicated operating room team when it comes to managing these complex patients. Identifying who these complex patients are can be helpful in surgical planning as well. In these patients, minimally invasive spine surgery may have a

role. Performing a limited decompression and fusion or even just a laminotomy and foraminotomy may be preferable to a lengthy instrumented fusion even if the outcome may be inferior. Patients who have a history of infections should also be identified as they are at risk of perioperative infections complications. Patients who are on anticoagulation therapy are at increased risk of bleeding complications in the perioperative period. Identifying these patients and having a discussion with the physician regarding the timing of anticoagulation can be helpful. In some cases, an IV filter may be helpful if the patients are at high risk of venous thromboembolism postoperatively. Depression and psychiatric issues can also compromise a patient’s outcome and recovery. In some cases, these patients may not be candidates for surgery even though they have a surgical issue. Patients who are older, obese, and have lower preop-

erative function are also at risk of longer lengths of stay. Identifying a rehab facility or skilled nursing facility for these patients to go to ahead of time can be helpful in discharge planning for these patients and decrease their length of stay. This is another category of patients who may benefit from minimally invasive spine surgery or a surgery that is less invasive. One of the biggest factors associated with an extended length of hospital stay is the lack of support at home. Identifying the caretakers for patients can help the facility patient discharge process and reduce readmission. Support after surgery can be in the form of family and even hired aides. It is beneficial to have a discussion on length of stay, discharge destination, pain control, and recovery course with patients because it is often during these discussions that disposition issues come up, given that many patients do not know what rehab or skilled nursing facilities they are eligible

for after surgery. The management of surgical patients has become more complex because patients are living longer and hospital reimbursements are decreasing. This presents challenges to the hospital, surgeon, and patient. But collaboration between surgeons with their patients and hospital administration can improve hospital and operating room efficiency and patient outcomes. References 1. Rajaee SS, Bae HW, Kanim LE, et al. Spinal fusion in the United States: analysis of trends from 1998 to 2008. Spine (Phila Pa 1976). 2012 Jan 1;37(1):67-76. 2. Goz V, Rane A, Abtahi AM, et al. Geographic variations in the cost of spine surgery. Spine (Phila Pa 1976). 2015 Sep 1;40(17):13809. 3. Guan J, Karsy M, Schmidt MH, et al. Multivariable analysis of factors affecting length of stay and hospital charges after single-level corpectomy. J Clin Neurosci. 2017 Oct;44:279283.

Vertebral Columns • Spring 2019

MIS

MIS Options for Pelvic Fixation Philip J. York MD, Sheeraz A. Qureshi MD MBA

As minimally invasive options for spinal fusion have improved, the indications for placing pedicle screws percutaneously have expanded significantly. There are numerous studies and reports in the literature of MIS techniques being implemented for long-construct fusions for both degenerative and deformity surgeries. One of the biggest challenges, however, is obtaining a stable base at the distal end of a fusion extending to the sacrum as fusions ending at S1 have been shown to have poor outcomes related to complications such as sacral fractures, higher rates of pseudarthrosis, and increased hardware failure due to excessive mechanical strain at the lumbosacral junction.1,2 Minimally invasive options such as anterior or posterior interbody techniques at the L5-S1 level have been shown to offer reasonable fusion rates but lack the biomechanical rigidity and protection of S1 that pelvic fixation offers. Adding robust pelvic fixation to a minimally invasive repertoire has been a challenge, however, there are now several techniques which have been described and that are continuing to be improved upon. Fixation options Iliac fixation Conventional pelvic fixation has been done in the form of iliac screws, placed at or near the posterior superior iliac spine (PSIS) (Figure 1) with robust fixation into 8

Vertebral Columns â&#x20AC;˘ Spring 2019

the dense bone above the sciatic notch and providing biomechanical support anterior to the center of rotation of the construct lever arm, thus, protecting the fixation at the lumbosacral junction. While this offers incredible biomechanical advantage, these screws have most commonly been placed in open surgeries and require aggressive soft tissue dissection from the midline out to and around the PSIS which has been associated with wound complications and increased risk of infection. Further, these screws are notorious for being prominent and often can be symptomatic. Especially relevant for the MIS surgeon is the challenge of creating connections between these screws and the remainder of the more proximal construct as the screws can be difficult to line up in the coronal plane and might require offset connectors. S2 Alar iliac fixation In an effort to address some of the downsides of iliac screws, fixation via S2 alar iliac (S2AI) screws were described passing from the bony Figure 1: Starting points for iliac screw (star) and S2 alar iliac (+).

corridor between and just lateral to the S1 and S2 neural foramen and extending through the sacroiliac joint (SIJ) into the ilium.3 These screws have been shown to be less prominent, require less soft tissue dissection, and provide adequate stability compared to iliac screws on multiple studies.4,5 Additionally, especially in patients with a wider pelvic morphology, the S2AI screw may be better in line with the S1 screws for direct connection with the rod without cross-connectors. Unilateral vs bilateral screw fixation Recently there has been interest in whether or not unilateral fixation via iliac or S2AI screws is sufficient to provide adequate stability to avoid the potential complications discussed. Based on biomechanical studies as well as small-series reports, it seems that unilateral fixation performs similarly well to bilateral fixation in both iliac and S2AI screws in terms of rates of sacral fracture, screw loosening, infection rates and hardware failure.6â&#x20AC;&#x201C;8 However, larger studies with randomization would be required to tease out whether or not there is truly no superiority of bilateral fixation and, if not, in what circumstances it would be indicated to utilize bilateral fixation points. At this time, the decision of whether or not unilateral vs bilateral fixation is warranted falls upon the surgeon to use their judgement. For now, either option can be reasonable. Techniques Free hand technique

Generally speaking, free hand technique for placement of pelvic fixation is considered an open technique where the regional landmarks are visible such as the PSIS, posterior inferior iliac spine (PIIS), the neural foramina, and the median and lateral sacral crests. Fluoroscopy In the case of MIS pelvic fixation, intraoperative fluoroscopy (fluoro) allows for accurate placement with a low risk of complication. Ideal iliac screw trajectory lies within the inner and outer table of the ilium. Specific radiographic views necessary for safe placement of percutaneous screws in this corridor of bone have been described in detail in the trauma literature for the retrograde placement of supraacetabular external fixation pins9 or for definitive fixation of various acetabular fractures10 via antegrade or retrograde technique. Wang et al 201611 described the use of these views for MIS pelvic screw fixation. First, the obturator outlet view is utilized to visualize the tear drop of the inner and outer table of the ilium. The entry site should lie within this teardrop on fluoro (Figure 2), starting just ventral to the PSIS. A drill or osteotome is used to remove enough cortical bone to enable recessing of the head to minimize prominence. A Jamshidi needle is then advanced to a premeasured depth for the desired screw length ensuring that the tip stays within the teardrop. An iliac oblique view can be used to be sure that the trajectory of the screw is above the sciatic notch (Figure 3) and an obturator inlet view can insure that the trajectory will not breech medial or lateral to the cortex. It is recommended that screw connections via screw extensions and the

Figure 2: Tear drop representing the safe corridor of bone from the PSIS to the AIIS. This can be seen on an obturator-outlet radiograph and can assist with both the starting point for an iliac screw as well as ensuring that the tip of the screw is within the bony corridor.

Figure 3: Iliac oblique view of the pelvis which can be utilized to ensure that screw placement is safely above the sciatic notch. rod should be passed from the most cranial tulip first going from proximal to distal. The biggest challenge remains connecting the iliac tulip to the rod as this often requires unique rod contours which are often difficult to pass beneath the skin and fascia. Some tips provided include maximizing the distance between the iliac and the S1 screws (i.e. high in S1 pedicle and low in tear drop), and being mindful to line up the start point of the iliac screw to be in the coronal plane. George et al12 described a simplified

Figure 4: Lateral view of a pelvis depicting the safe corridor of bone from the PSIS and AIIS. The sciatic notch can be visualized on most views of the pelvis and the screw must be safely above this region. fluoro technique that could reliably be performed with AP radiograph only to ensure that the trajectory is above the sciatic notch (Figure 4). After palpating the PSIS, a 2cm longitudinal incision is made just medial with subsequent dissection down to fascia with a Cobb. The fascia is then split longitudinally directly over PSIS, striping medially and maintaining a fascia for repair later. A chisel gouge is then used to remove enough bone from the medial half of the ilium to accommodate screw head and rod. A blunt curved pedicle probe is started just dorsal to the sacrum and SI joint with the curve aimed lateral to avoid SI penetration, advanced until resistance, and then turned 180 degrees and advanced, turning 180 degrees each time cortical bone is encountered. S2AI screws can also be placed percutaneously with fluoro assistance. A technique for MIS placement was described nicely by Oâ&#x20AC;&#x2122;Brien et al13 in which the S1 foramen was identified on fluoroscopy and a trochar was placed just distal and lateral to this foramen (Figure 1). AP radiographs were utilized to aim the trochar above Vertebral Columns â&#x20AC;˘ Spring 2019

the sciatic notch and inlet radiographs were used to prevent medial breech into the pelvis. Once the SI joint was cross, a blunt guidewire was used to advance through the ilium either by hand or with a driver until a cortex was reached. A tap was passed through the SI joint followed by the final screw. The teardrop view is less beneficial as the start point would fall medial to this and the screw would track from medial to lateral across the teardrop with this technique (Figure 5). Navigation Navigation has allowed for immediate anatomical feedback during placement of MIS pelvic fixation. Especially with anatomic variability in pelvic morphology, the ability to see the final projected destination of an iliac screw or to visualize the proximity to the central canal and the adjacent neuroforamen for S2AI screws is beneficial. However, there can be a learning curve in comprehending the various CT reconstructions with the complex pelvic anatomy and this can lead to misplacement especially if the surgeon is not already familiar with the use of intraoperative navigation. Additionally, the surgeon cannot forget the principles of screw placement discussed in the sections above. For iliac screws, a start point ventral to the PSIS and recessed to prevent prominence and a start point in line with the S1 screws is crucial to avoid struggling with passing the rods and connecting the construct. For S2AI screws, allowing sufficient distance between the start point and the S1 screws is helpful and avoiding anterior penetration of the SI joint is key which can be difficult to see on the reconstructed CT images used during navigation. 10

Vertebral Columns • Spring 2019

References 1. Godzik J, Hlubek RJ, Newcomb AG, et al. Supplemental rods are needed to maximally reduce rod strain across the lumbosacral junction with TLIF but not ALIF in long constructs. Spine J. 2019;000. doi:10.1016/j. spinee.2019.01.005. 2. Shen FH, Mason JR, Shimer AL, Arlet VM. Pelvic fixation for adult scoliosis. Eur Spine J. 2013;22 Suppl 2(Suppl 2):S265-75. doi:10.1007/s00586-012-2525-3.

Figure 5: A fluoroscopic view of the teardrop in the case of an S2AI screw. Note that the start point for the screw is medial to the teardrop in this screw but the tip of the screw resides safely within the teardrop. Robot-assisted A benefit to robotic-assisted placement of MIS pelvic fixation is the ability to plan the ideal screw trajectory, diameter and length preoperatively in a setting where the surgeon can take the time to understand any peculiarities in individual pelvic morphology. While this option is still relatively new, there has been data to support success in the implementation of robotic assistance for these fixation techniques.14 Conclusion With a growing trend towards performing larger fusion surgeries with MIS techniques, the ability to utilize robust pelvic fixation is exceedingly important. Iliac and S2AI screws provide rigid support to protect the fixation across the lumbopelvic region and can be placed with MIS techniques utilizing image-guidance. The challenge, going forward, is to create improved methods of connecting increasingly complex screw-rod constructs in an MIS fashion.

3. Chang T-L, Sponseller PD, Kebaish KM, Fishman EK. Low profile pelvic fixation: anatomic parameters for sacral alar-iliac fixation versus traditional iliac fixation. Spine (Phila Pa 1976). 2009;34(5):436-440. doi:10.1097/BRS. 0b013e318194128c. 4. Sutterlin CE, Field A, Ferrara LA, Freeman AL, Phan K, Phan K. Range of motion, sacral screw and rod strain in long posterior spinal constructs: a biomechanical comparison between S2 alar iliac screws with traditional fixation strategies. J spine Surg (Hong Kong). 2016;2(4):266-276. doi:10.21037/jss.2016.11.01. 5. O’Brien JR, Yu WD, Bhatnagar R, Sponseller P, Kebaish KM. An anatomic study of the S2 iliac technique for lumbopelvic screw placement. Spine (Phila Pa 1976). 2009;34(12):E43942. doi:10.1097/BRS.0b013e3181a4e3e4. 6. Tomlinson T, Chen J, Upasani V, Mahar A. Unilateral and Bilateral Sacropelvic Fixation Result in Similar Construct Biomechanics. Spine (Phila Pa 1976). 2008;33(20):2127-2133. doi:10.1097/BRS.0b013e31817bd8d5. 7. Saigal R, Lau D, Wadhwa R, et al. Unilateral versus bilateral iliac screws for spinopelvic fixation: are two screws better than one? Neurosurg Focus. 2014;36(5):E10. doi:10.3171/2014.3.FOCUS1428. 8. Nazemi AK, Gowd AK, Vaccaro AR, Carmouche JJ, Behrend CJ. Unilateral S2 alar-iliac screws for spinopelvic fixation. Surg Neurol Int. 2018;9:75. doi:10.4103/sni.sni_460_17. 9. Bishop JA, Routt ML (Chip). Osseous fixation pathways in pelvic and acetabular fracture surgery. J Trauma Acute Care Surg. 2012;72(6):1502-1509. doi:10.1097/ TA.0b013e318246efe5. 10. Starr AJ, Walter JC, Harris RW, Reinert CM, Jones AL. Percutaneous screw fixation of fractures of the iliac wing and fracture-dislocations of the sacro-iliac joint (OTA Types 61-B2.2 and 61-B2.3, or Young-Burgess “lateral compression type II”; pelvic fractures). J Orthop Trauma. 2002;16(2):116-123. http://www. ncbi.nlm.nih.gov/pubmed/11818807. Accessed February 25, 2019. 11. Wang MY, Williams S, Mummaneni P V., Sherman JD. Minimally Invasive Percutaneous Iliac Screws: Initial 24 Case Experiences

with CT Confirmation. Clin Spine Surg. 2016. doi:10.1097/BSD.0b013e3182733c43. 12. George SG, Lebwohl NH, Pasquotti G, Williams SK. Percutaneous and open iliac screw safety and accuracy using a tactile technique with adjunctive anteroposterior fluoroscopy. Spine J. 2018. doi:10.1016/j. spinee.2018.01.024. 13. Oâ&#x20AC;&#x2122;Brien JR, Matteini L, Yu WD, Kebaish KM. Feasibility of minimally invasive sacropelvic fixation: Percutaneous S2 alar iliac fixation. Spine (Phila Pa 1976). 2010;35(4):460-464. doi:10.1097/BRS.0b013e3181b95dca. 14. Hyun SJ, Kim KJ, Jahng TA. S2 alar iliac screw placement under robotic guidance for adult spinal deformity patients: technical note. Eur Spine J. 2017;26(8):2198-2203. doi:10.1007/s00586-017-5012-z.

Vertebral Columns â&#x20AC;˘ Spring 2019

TLIF

Maximizing Lordosis with Minimally Invasive TLIF, Part 1: Key Considerations Prior to Cage Placement Peter Derman MD MBA

Transforaminal interbody fusion (TLIF) via a tubular retractor is a minimally invasive surgical (MIS) alternative to the traditional open TLIF. While the means of accessing the spine differ, the goals of surgery are identical – neural element decompression and stabilization of the spine via interbody fusion supported by posterior pedicle screw instrumentation. Numerous studies have been performed comparing open to MIS TLIF. These have generally found similar radiographic outcomes (including restoration of lordosis) with reduced peri-operative morbidity, shorter length of stay, and less economic expense associated with the minimally invasive technique1. Additionally, some data suggest that there may be improvement in long-term outcomes such as back pain and disability with the MIS approach2. The importance of sagittal alignment is increasingly evident in the spine literature. Compared to other interbody techniques, TLIF has been shown least capable of producing substantial increases in segmental and global lumbar lordosis3. It is therefore imperative that surgeons take steps to maximize the attainable lordosis when 12

Vertebral Columns • Spring 2019

performing TLIFs. The technical margin of error is likely lower in MIS than traditional open TLIF as concurrent inter-transverse fusion is typically not performed. Strategies for achieving lordosis without increasing the risk of subsidence and pseudoarthrosis are therefore particularly salient in the setting of MIS TLIF. The groundwork for success is laid pre-operatively. A dual-energy x-ray absorptiometry (DEXA) scan should be performed in any patient at risk for osteopenia and osteoporosis. Because low bone mineral density (BMD) is a more important predictor of subsidence than cage design or placement4, optimization of patients’ BMD before elective TLIF surgery is extremely important to ensuring that lordosis can be achieved and maintained.

tention to seemingly small details can be hugely important. Patient positioning might be overlooked but is key for optimizing lordosis. Placing the patient on a four-post open Jackson frame with the pelvic pads positioned fairly low (i.e., at or immediately below the anterior superior iliac spines) and the lower extremities up on a flat board (rather than down in a sling) can help increase lordosis (Figure 1).

Careful and thorough disc space preparation is necessary to mobilize the spinal level, allow for maximal cage size, and improve fusion rates. A cadaveric study by Rihn et al. demonstrated that only about 75% of disc material is removed during MIS TLIFs, with the posterior contralateral quadrant the least likely to be thoroughly prepared5. Inadequate disc preparation is a common cause of suboptimal outcomes Once in the operating room, atafter both MIS and open TLIFs – a Figure 1: Patient Positioning. The patient is placed on a four-post open Jackson frame with the pelvic pads positioned low and the knees up on a flat board rather than in a sling to help optimize lordosis.

significant amount of time should therefore be allotted to this surgical step. Study authors also reported a significantly higher rate of endplate violations in their MIS than open groups (15% vs 5%, p=0.04)5. Because endplate violations likely pre-dispose to cage subsidence, which can negate any initial gains in lordosis, particular care must be taken in MIS TLIFs. Avoidance of aggressive use of endplate shavers is advisable. In the setting of severely collapsed levels and those with ankylosis, bilateral approaches for bilateral facetectomies may be considered. Similar to a posterior column osteotomy, this theoretically allows for greater mobilization of the disc space so that it can be fused in a position of greater lordosis. While the benefit of this technique has not been borne out in the current literature6, no high-quality, randomized controlled studies (RCTs) have been performed directly comparing unilateral to bilateral facetectomy in patients with advanced disc collapse or ankylosis.

In summary, a properly performed MIS TLIF should have radiographic outcomes that are similar to those of traditional open TLIF with the potential for improved clinical results. Regardless of the approach, however, the ability to significantly increase lordosis with TLIF is currently somewhat limited. Surgeons must therefore employ multiple tactics to maximize achievable lordosis. Such strategies include: optimizing bone mineral density; positioning the patient in lordosis; thorough disc preparation to mobilize the level and maximize fusion; avoiding endplate violations to reduce the chance of subsidence and loss of lordosis; and considering bilateral approaches in severely collapsed discs. In the upcoming Part 2 of this series, the impact of cage selection and placement on sagittal alignment will be discussed. References

BRS.0000000000001462 2. Li Y-B, Wang X-D, Yan H-W, Hao D-J, Liu Z-H. The Long-term Clinical Effect of Minimal-Invasive TLIF Technique in 1-Segment Lumbar Disease. Clin Spine Surg. 2017;30(6):E713-E719. doi:10.1097/ BSD.0000000000000334 3. Sembrano JN, Yson SC, Horazdovsky RD, Santos ERG, Polly DW. Radiographic Comparison of Lateral Lumbar Interbody Fusion Versus Traditional Fusion Approaches: Analysis of Sagittal Contour Change. Int J Spine Surg. 2015;9:16. doi:10.14444/2016 4. Lam FC, Alkalay R, Groff MW. The effects of design and positioning of carbon fiber lumbar interbody cages and their subsidence in vertebral bodies. J Spinal Disord Tech. 2012;25(2):116-122. doi:10.1097/ BSD.0b013e31820ef778 5. Rihn JA, Gandhi SD, Sheehan P, et al. Disc space preparation in transforaminal lumbar interbody fusion: a comparison of minimally invasive and open approaches. Clin Orthop Relat Res. 2014;472(6):1800-1805. doi:10.1007/ s11999-014-3479-z 6. Tye EY, Alentado VJ, Mroz TE, Orr RD, Steinmetz MP. Comparison of Clinical and Radiographic Outcomes in Patients Receiving Single-Level Transforaminal Lumbar Interbody Fusion With Removal of Unilateral or Bilateral Facet Joints. Spine. 2016;41(17):E1039-1045. doi:10.1097/BRS.0000000000001535

1. Goldstein CL, Phillips FM, Rampersaud YR. Comparative Effectiveness and Economic Evaluations of Open Versus Minimally Invasive Posterior or Transforaminal Lumbar Interbody Fusion: A Systematic Review. Spine. 2016;41 Suppl 8:S74-89. doi:10.1097/

Vertebral Columns â&#x20AC;˘ Spring 2019

OUTCOMES

The Use of PROMIS in Spine Surgery: An Overview of the Existing Literature Kelsey Young BS, Sravisht Iyer MD Background There has been an increase in patient reported outcomes measures (PROMs) in orthopaedics to evaluate outcomes from the patients’ perspective for both research and clinical use.5 Currently, there are various PROMs that assess patient outcomes, often referred to as “legacy measures.” These legacy measures are typically validated for different types of spinal pathology, e.g., the Oswestry Disability Index (ODI) for low back pain and the Neck Disability Index (NDI) for neck pain.3, 12 Unfortunately, outcomes from these different PROMs are frequently difficult to compare with one another even in patients with similar pathology.6 They are also limited by the time necessary for completion.6 In 2004, the National Institutes of Health developed the Patient-Reported Outcomes Measurement Information System (PROMIS) to provide a widely reliable and valid tool to measure patient outcomes across medicine.3 The PROMIS question banks are divided into a variety of domains (physical function, pain interference, etc.). These domains each contain questions that have been adapted from existing patient-outcome questionnaires and subsequently revised to optimize clarity and content. Because these question banks draw from a vari14

Vertebral Columns • Spring 2019

ety of sources, they are frequently large and exhaustive; the physical function (PF) question bank, for example, contains 124 questions. To maximize usability, the NIH has developed computer adaptive testing (CAT) and various short-form versions to reduce questionnaire burden. The PROMIS CATs are able to rapidly determine a patients’ ability by presenting questions based on past responses; e.g., they do not ask if you can run two miles if you answered you cannot walk one block on a previous question. Since its development, there has been in large increase in attention surrounding the validity, responsiveness, and ease of using PROMIS in spine patients. The purported strengths of PROMIS include: low floor and ceiling effects (improved coverage), rigorous psychometric validation and the availability of CAT and short-form instruments to lower questionnaire burden. Psychometric Properties of PROMIS in Spine The initial validation of PROMIS in spine patients was performed by Hung et al. using a 124 item data bank. These authors showed PROMIS Physical Function (PF) had 1.7% ceiling effect and a minimal 0.2% floor effect, and that item reliability was 1.00 and person reliability was 0.99. However, they did find limited item bias associated with sex, age, and education in some

items.8 Brodke et al. similarly found excellent ceiling and floor effects for the PROMIS PF computer assisted testing (CAT) (0.81% and 3.86% respectively).4 PROMIS Physical Function and Pain Validation with Legacy Measures Many studies have sought to validate the PROMIS PF, pain interference (PI), and pain behavior (PB) forms against legacy measures including the Oswestry Disability Index (ODI), Short Form-12 (SF-12), Visual Analog Scale (VAS), and Neck Disability Index (NDI). These studies have shown moderate to strong correlations between PROMIS PF, PI and PB scores with the ODI (|r|= 0.525-0.8907), NDI (|r|= 0.60-0.786), and SF-12 (|r|=0.440.854) among populations with spinal deformities,4,9,15,19,20 cervical pathology,2, 13, 14, 20 and lumbar stenosis,16 or who underwent lumbar discectomies,1 minimally invasive lumbar discectomies,11 minimally invasive TLIFs,7 anterior cervical spine surgery,17 and lumbar decompressions.18 Studies that assessed the correlation between these PROMIS PF, PI, and PB scores and VAS scores were less consistently statistically significant, but with |r|= 0.376-0.727 when significant.7,11,13 Overall, each study concluded that PROMIS PF, PI, and PB were valid and responsive measures of physical function and pain in their respective patient populations.

PROMIS Anxiety and Depression Validation with Legacy Measures Studies have also focused on the validity of PROMIS anxiety and depression measures in spine patients. In 2015, Hung et al. first assessed whether the PROMIS anxiety SF-4 or the PROMIS depression SF-4 could be used in place of the distress and risk assessment method modified Zung Depression Index (DRAM mZDI). Regression analyses were carried out to predict the mZDI total scores from the PROMIS anxiety SF-4 T scores and the PROMIS depression SF-4 T scores. All 3 instruments were highly correlated with each other. The intraclass correlation coefficients for the actual and predicted mZDI scores were also high, indicating that the PROMIS anxiety SF-4 scores and the depression SF-4 scores can accurately predict the mZDI scores and can be used as surrogates for the mZDI.10 In 2017 and 2018, Purvis et al. showed that various PROMIS domains were also highly correlated with the Generalized Anxiety Disorder-7 and Patient Health Questionnaire-8 forms in anterior cervical spine and lumbar disc degeneration patients.17, 18 These studies highlight the valid utility of PROMIS anxiety and depression tools in place of legacy measures. Ease of Completion All studies that have reported on the time needed to complete PROM questionnaires in spine patients have shown that PROMIS requires significantly less time than legacy measures.1,2,4,15,16 Papuga et al. first described how PROMIS CATs required on average 4.5 questions and took 35 seconds to complete, compared with the ODI/NDI requiring on average 10 questions and taking

188 seconds.15 Brodke et al. similarly reported the time required to answer all items in the PF CAT was 44 seconds while the ODI and SF-36 PFD was 169 and 99 seconds, respectively.4 These studies highlight how PROMIS can pose significantly less administrative burden compared to legacy measures. References 1. Bhatt S, Boody BS, Savage JW, Hsu WK, Rothrock NE, Patel AA. Validation of Patient-reported Outcomes Measurement Information System Computer Adaptive Tests in Lumbar Disk Herniation Surgery. J Am Acad Orthop Surg. 2018 Sep 18. Epub 2018/09/25. 2. Boody BS, Bhatt S, Mazmudar AS, Hsu WK, Rothrock NE, Patel AA. Validation of Patient-Reported Outcomes Measurement Information System (PROMIS) computerized adaptive tests in cervical spine surgery. J Neurosurg Spine. 2018 Mar;28(3):268-279. Epub 2018/01/06. 3. Brodke DJ, Saltzman CL, Brodke DS. PROMIS for Orthopaedic Outcomes Measurement. J Am Acad Orthop Surg. 2016 Nov;24(11):744-749. Epub 2016/10/19. 4. Brodke DS, Goz V, Voss MW, Lawrence BD, Spiker WR, Hung M. PROMIS PF CAT Outperforms the ODI and SF-36 Physical Function Domain in Spine Patients. Spine (Phila Pa 1976). 2017 Jun 15;42(12):921-929. Epub 2016/10/30. 5. Fidai MS, Saltzman BM, Meta F, Lizzio VA, Stephens JP, Bozic KJ, et al. Patient-Reported Outcomes Measurement Information System and Legacy Patient-Reported Outcome Measures in the Field of Orthopaedics: A Systematic Review. Arthroscopy. 2018 Feb;34(2):605614. Epub 2017/11/04.

9. Hung M, Saltzman CL, Voss MW, Bounsanga J, Kendall R, Spiker R, et al. Responsiveness of the Patient-Reported Outcomes Measurement Information System (PROMIS), Neck Disability Index (NDI) and Oswestry Disability Index (ODI) instruments in patients with spinal disorders. Spine J. 2018 Jun 30. Epub 2018/07/04. 10. Hung M, Stuart A, Cheng C, Hon SD, Spiker R, Lawrence B, et al. Predicting the DRAM mZDI using the PROMIS anxiety and depression. Spine (Phila Pa 1976). 2015 Feb 1;40(3):179-183. Epub 2014/11/14. 11. Khechen B, Haws BE, Patel DV, Bawa MS, Elboghdady IM, Lamoutte EH, et al. PROMIS Physical Function Score Strongly Correlates with Legacy Outcome Measures in Minimally Invasive Lumbar Microdiscectomy. Spine (Phila Pa 1976). 2018 Aug 7. Epub 2018/08/11. 12. McCormick JD, Werner BC, Shimer AL. Patient-reported outcome measures in spine surgery. J Am Acad Orthop Surg. 2013 Feb;21(2):99-107. Epub 2013/02/05. 13. Moses MJ, Tishelman JC, Stekas N, Jevotovsky DS, Vasquez-Montes D, Karia R, et al. Comparison of Patient Reported Outcome Measurement Information System (PROMIS) with Neck Disability Index (NDI) and Visual Analog Scale (VAS) in Patients with Neck Pain. Spine (Phila Pa 1976). 2018 Jul 13. Epub 2018/07/18. 14. Owen RJ, Zebala LP, Peters C, McAnany S. PROMIS Physical Function Correlation With NDI and mJOA in the Surgical Cervical Myelopathy Patient Population. Spine (Phila Pa 1976). 2018 Apr 15;43(8):550-555. Epub 2017/08/09. 15. Papuga MO, Mesfin A, Molinari R, Rubery PT. Correlation of PROMIS Physical Function and Pain CAT Instruments With Oswestry Disability Index and Neck Disability Index in Spine Patients. Spine (Phila Pa 1976). 2016 Jul 15;41(14):1153-1159. Epub 2016/02/26.

6. Guzman JZ, Cutler HS, Connolly J, Skovrlj B, Mroz TE, Riew KD, et al. Patient-Reported Outcome Instruments in Spine Surgery. Spine (Phila Pa 1976). 2016 Mar;41(5):429-437. Epub 2015/11/17.

16. Patel AA, Dodwad SM, Boody BS, Bhatt S, Savage JW, Hsu WK, et al. Validation of Patient Reported Outcomes Measurement Information System (PROMIS) Computer Adaptive Tests (CATs) in the Surgical Treatment of Lumbar Spinal Stenosis. Spine (Phila Pa 1976). 2018 Nov 1;43(21):1521-1528. Epub 2018/03/21.

7. Haws BE, Khechen B, Guntin JA, Cardinal KL, Bohl DD, Singh K. Validity of PROMIS in minimally invasive transforaminal lumbar interbody fusion: a preliminary evaluation. J Neurosurg Spine. 2018 Jul;29(1):28-33. Epub 2018/04/14.

17. Purvis TE, Andreou E, Neuman BJ, Riley LH, 3rd, Skolasky RL. Concurrent Validity and Responsiveness of PROMIS Health Domains Among Patients Presenting for Anterior Cervical Spine Surgery. Spine (Phila Pa 1976). 2017 Dec 1;42(23):E1357-e1365. Epub 2017/07/26.

8. Hung M, Hon SD, Franklin JD, Kendall RW, Lawrence BD, Neese A, et al. Psychometric properties of the PROMIS physical function item bank in patients with spinal disorders. Spine (Phila Pa 1976). 2014 Jan 15;39(2):158163. Epub 2013/11/01.

18. Purvis TE, Neuman BJ, Riley LH, 3rd, Skolasky RL. Discriminant Ability, Concurrent Validity, and Responsiveness of PROMIS Health Domains Among Patients With Lumbar Degenerative Disease Undergoing Decompression With or Without Arthrodesis. Spine (Phila Pa 1976). 2018 Nov 1;43(21):1512-1520. Epub

Vertebral Columns â&#x20AC;˘ Spring 2019

2018/04/06. 19. Raad M, Jain A, Huang M, Skolasky RL, Sciubba DM, Kebaish KM, et al. Validity and responsiveness of PROMIS in adult spinal deformity: The need for a self-image domain. Spine J. 2018 Jul 25. Epub 2018/07/28. 20. Sharma M, Ugiliweneza B, Beswick J, Boakye M. Concurrent Validity and Comparative Responsiveness of PROMIS-SF Versus Legacy Measures in the Cervical and Lumbar Spine Population: Longitudinal Analysis from Baseline to Postsurgery. World Neurosurg. 2018 Jul;115:e664-e675. Epub 2018/05/02.

Vertebral Columns â&#x20AC;˘ Spring 2019