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Justin S. Smith, Thomas J. Buell, Christopher I. Shaffrey, Han Jo Kim, Eric Klineberg, Themistocles Protopsaltis, Peter Passias, Gregory M. Mundis Jr., Robert Eastlack, Vedat Deviren, Michael P. Kelly, Alan H. Daniels, Jeffrey L. Gum, Alex Soroceanu, Munish Gupta, Doug Burton, Richard Hostin, Robert Hart, Virginie Lafage, Renaud Lafage, Frank J. Schwab, Shay Bess and Christopher P. Ames

OBJECTIVE

Although surgical treatment can provide significant improvement of symptomatic adult cervical spine deformity (ACSD), few reports have focused on the associated complications. The objective of this study was to assess complication rates at a minimum 1-year follow-up based on a prospective multicenter series of ACSD patients treated surgically.

METHODS

A prospective multicenter database of consecutive operative ACSD patients was reviewed for perioperative (< 30 days), early (30–90 days), and delayed (> 90 days) complications with a minimum 1-year follow-up. Enrollment required at least 1 of the following: cervical kyphosis > 10°, cervical scoliosis > 10°, C2–7 sagittal vertical axis > 4 cm, or chin-brow vertical angle > 25°.

RESULTS

Of 167 patients, 133 (80%, mean age 62 years, 62% women) had a minimum 1-year follow-up (mean 1.8 years). The most common diagnoses were degenerative (45%) and iatrogenic (17%) kyphosis. Almost 40% of patients were active or past smokers, 17% had osteoporosis, and 84% had at least 1 comorbidity. The mean baseline Neck Disability Index and modified Japanese Orthopaedic Association scores were 47 and 13.6, respectively. Surgical approaches were anterior-only (18%), posterior-only (47%), and combined (35%). A total of 132 complications were reported (54 minor and 78 major), and 74 (56%) patients had at least 1 complication. The most common complications included dysphagia (11%), distal junctional kyphosis (9%), respiratory failure (6%), deep wound infection (6%), new nerve root motor deficit (5%), and new sensory deficit (5%). A total of 4 deaths occurred that were potentially related to surgery, 2 prior to 1-year follow-up (1 cardiopulmonary and 1 due to obstructive sleep apnea and narcotic use) and 2 beyond 1-year follow-up (both cardiopulmonary and associated with revision procedures). Twenty-six reoperations were performed in 23 (17%) patients, with the most common indications of deep wound infection (n = 8), DJK (n = 7), and neurological deficit (n = 6). Although anterior-only procedures had a trend toward lower overall (42%) and major (21%) complications, rates were not significantly different from posterior-only (57% and 33%, respectively) or combined (61% and 37%, respectively) approaches (p = 0.29 and p = 0.38, respectively).

CONCLUSIONS

This report provides benchmark rates for ACSD surgery complications at a minimum 1-year (mean 1.8 years) follow-up. The marked health and functional impact of ACSD, the frail population it affects, and the high rates of surgical complications necessitate a careful risk-benefit assessment when contemplating surgery. Collectively, these findings provide benchmarks for complication rates and may prove useful for patient counseling and efforts to improve the safety of care.

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Alan H. Daniels, Daniel B. C. Reid, Wesley M. Durand, D. Kojo Hamilton, Peter G. Passias, Han Jo Kim, Themistocles S. Protopsaltis, Virginie Lafage, Justin S. Smith, Christopher I. Shaffrey, Munish Gupta, Eric Klineberg, Frank Schwab, Douglas Burton, Shay Bess, Christopher P. Ames, Robert A. Hart and the International Spine Study Group

OBJECTIVE

Optimal patient selection for upper-thoracic (UT) versus lower-thoracic (LT) fusion during adult spinal deformity (ASD) correction is challenging. Radiographic and clinical outcomes following UT versus LT fusion remain incompletely understood. The purposes of this study were: 1) to evaluate demographic, radiographic, and surgical characteristics associated with choice of UT versus LT fusion endpoint; and 2) to evaluate differences in radiographic, clinical, and health-related quality of life (HRQOL) outcomes following UT versus LT fusion for ASD.

METHODS

Retrospective review of a prospectively collected multicenter ASD database was performed. Patients with ASD who underwent fusion from the sacrum/ilium to the LT (T9–L1) or UT (T1–6) spine were compared for demographic, radiographic, and surgical characteristics. Outcomes including proximal junctional kyphosis (PJK), reoperation, rod fracture, pseudarthrosis, overall complications, 2-year change in alignment parameters, and 2-year HRQOL metrics (Lumbar Stiffness Disability Index, Scoliosis Research Society-22r questionnaire, Oswestry Disability Index) were compared after controlling for confounding factors via multivariate analysis.

RESULTS

Three hundred three patients (169 LT, 134 UT) were evaluated. Independent predictors of UT fusion included greater thoracic kyphosis (odds ratio [OR] 0.97 per degree, p = 0.0098), greater coronal Cobb angle (OR 1.06 per degree, p < 0.0001), and performance of a 3-column osteotomy (3-CO; OR 2.39, p = 0.0351). While associated with longer operative times (ratio 1.13, p < 0.0001) and greater estimated blood loss (ratio 1.31, p = 0.0018), UT fusions resulted in greater sagittal vertical axis improvement (−59.5 vs −41.0 mm, p = 0.0035) and lower PJK rates (OR 0.49, p = 0.0457). No significant differences in postoperative HRQOL measures, reoperation, or overall complication rates were detected between groups (all p > 0.1).

CONCLUSIONS

Greater deformity and need for 3-CO increased the likelihood of UT fusion. Despite longer operative times and greater blood loss, UT fusions resulted in better sagittal correction and lower 2-year PJK rates following surgery for ASD. While continued surveillance is necessary, this information may inform patient counseling and surgical decision-making.

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Dana L. Cruz, Ethan W. Ayres, Matthew A. Spiegel, Louis M. Day, Robert A. Hart, Christopher P. Ames, Douglas C. Burton, Justin S. Smith, Christopher I. Shaffrey, Frank J. Schwab, Thomas J. Errico, Shay Bess, Virginie Lafage and Themistocles S. Protopsaltis

OBJECTIVE

Neck and back pain are highly prevalent conditions that account for major disability. The Neck Disability Index (NDI) and Oswestry Disability Index (ODI) are the two most common functional status measures for neck and back pain. However, no single instrument exists to evaluate patients with concurrent neck and back pain. The recently developed Total Disability Index (TDI) combines overlapping elements from the ODI and NDI with the unique items from each. This study aimed to prospectively validate the TDI in patients with spinal deformity, back pain, and/or neck pain.

METHODS

This study is a retrospective review of prospectively collected data from a single center. The 14-item TDI, derived from ODI and NDI domains, was administered to consecutive patients presenting to a spine practice. Patients were assessed using the ODI, NDI, and EQ-5D. Validation of internal consistency, test-retest reproducibility, and validity of reconstructed NDI and ODI scores derived from TDI were assessed.

RESULTS

A total of 252 patients (mean age 55 years, 56% female) completed initial assessments (back pain, n = 115; neck pain, n = 52; back and neck pain, n = 55; spinal deformity, n = 55; and no pain/deformity, n = 29). Of these patients, 155 completed retests within 14 days. Patients represented a wide range of disability (mean ODI score: 36.3 ± 21.6; NDI score: 30.8 ± 21.8; and TDI score: 34.1 ± 20.0). TDI demonstrated excellent internal consistency (Cronbach’s alpha = 0.922) and test-retest reliability (intraclass correlation coefficient = 0.96). Differences between actual and reconstructed scores were not clinically significant. Subanalyses demonstrated TDI’s ability to quantify the degree of disability due to back or neck pain in patients complaining of pain in both regions.

CONCLUSIONS

The TDI is a valid and reliable disability measure in patients with back and/or neck pain and can capture each spine region’s contribution to total disability. The TDI could be a valuable method for total spine assessment in a clinical setting, and its completion is less time consuming than that for both the ODI and NDI.

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Samantha R. Horn, Peter G. Passias, Cheongeun Oh, Virginie Lafage, Renaud Lafage, Justin S. Smith, Breton Line, Neel Anand, Frank A. Segreto, Cole A. Bortz, Justin K. Scheer, Robert K. Eastlack, Vedat Deviren, Praveen V. Mummaneni, Alan H. Daniels, Paul Park, Pierce D. Nunley, Han Jo Kim, Eric O. Klineberg, Douglas C. Burton, Robert A. Hart, Frank J. Schwab, Shay Bess, Christopher I. Shaffrey, Christopher P. Ames and the International Spine Study Group

OBJECTIVE

Cervical deformity (CD) correction is clinically challenging. There is a high risk of developing complications with these highly complex procedures. The aim of this study was to use baseline demographic, clinical, and surgical factors to predict a poor outcome following CD surgery.

METHODS

The authors performed a retrospective review of a multicenter prospective CD database. CD was defined as at least one of the following: cervical kyphosis (C2–7 Cobb angle > 10°), cervical scoliosis (coronal Cobb angle > 10°), C2–7 sagittal vertical axis (cSVA) > 4 cm, or chin-brow vertical angle (CBVA) > 25°. Patients were categorized based on having an overall poor outcome or not. Health-related quality of life measures consisted of Neck Disability Index (NDI), EQ-5D, and modified Japanese Orthopaedic Association (mJOA) scale scores. A poor outcome was defined as having all 3 of the following categories met: 1) radiographic poor outcome: deterioration or severe radiographic malalignment 1 year postoperatively for cSVA or T1 slope–cervical lordosis mismatch (TS-CL); 2) clinical poor outcome: failing to meet the minimum clinically important difference (MCID) for NDI or having a severe mJOA Ames modifier; and 3) complications/reoperation poor outcome: major complication, death, or reoperation for a complication other than infection. Univariate logistic regression followed by multivariate regression models was performed, and internal validation was performed by calculating the area under the curve (AUC).

RESULTS

In total, 89 patients with CD were included (mean age 61.9 years, female sex 65.2%, BMI 29.2 kg/m2). By 1 year postoperatively, 18 (20.2%) patients were characterized as having an overall poor outcome. For radiographic poor outcomes, patients’ conditions either deteriorated or remained severe for TS-CL (73% of patients), cSVA (8%), horizontal gaze (34%), and global SVA (28%). For clinical poor outcomes, 80% and 60% of patients did not reach MCID for EQ-5D and NDI, respectively, and 24% of patients had severe symptoms (mJOA score 0–11). For the complications/reoperation poor outcome, 28 patients experienced a major complication, 11 underwent a reoperation, and 1 had a complication-related death. Of patients with a poor clinical outcome, 75% had a poor radiographic outcome; 35% of poor radiographic and 37% of poor clinical outcome patients had a major complication. A poor outcome was predicted by the following combination of factors: osteoporosis, baseline neurological status, use of a transition rod, number of posterior decompressions, baseline pelvic tilt, T2–12 kyphosis, TS-CL, C2–T3 SVA, C2–T1 pelvic angle (C2 slope), global SVA, and number of levels in maximum thoracic kyphosis. The final model predicting a poor outcome (AUC 86%) included the following: osteoporosis (OR 5.9, 95% CI 0.9–39), worse baseline neurological status (OR 11.4, 95% CI 1.8–70.8), baseline pelvic tilt > 20° (OR 0.92, 95% CI 0.85–0.98), > 9 levels in maximum thoracic kyphosis (OR 2.01, 95% CI 1.1–4.1), preoperative C2–T3 SVA > 5.4 cm (OR 1.01, 95% CI 0.9–1.1), and global SVA > 4 cm (OR 3.2, 95% CI 0.09–10.3).

CONCLUSIONS

Of all CD patients in this study, 20.2% had a poor overall outcome, defined by deterioration in radiographic and clinical outcomes, and a major complication. Additionally, 75% of patients with a poor clinical outcome also had a poor radiographic outcome. A poor overall outcome was most strongly predicted by severe baseline neurological deficit, global SVA > 4 cm, and including more of the thoracic maximal kyphosis in the construct.

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Darryl Lau, Cecilia L. Dalle Ore, Patrick Reid, Michael M. Safaee, Vedat Deviren, Justin S. Smith, Christopher I. Shaffrey and Christopher P. Ames

OBJECTIVE

The benefits and utility of routine neuromonitoring with motor and somatosensory evoked potentials during lumbar spine surgery remain unclear. This study assesses measures of performance and utility of transcranial motor evoked potentials (MEPs) during lumbar pedicle subtraction osteotomy (PSO).

METHODS

This is a retrospective study of a single-surgeon cohort of consecutive adult spinal deformity (ASD) patients who underwent lumbar PSO from 2006 to 2016. A blinded neurophysiologist reviewed individual cases for MEP changes. Multivariate analysis was performed to determine whether changes correlated with neurological deficits. Measures of performance were calculated.

RESULTS

A total of 242 lumbar PSO cases were included. MEP changes occurred in 38 (15.7%) cases; the changes were transient in 21 cases (55.3%) and permanent in 17 (44.7%). Of the patients with permanent changes, 9 (52.9%) had no recovery and 8 (47.1%) had partial recovery of MEP signals. Changes occurred at a mean time of 8.8 minutes following PSO closure (range: during closure to 55 minutes after closure). The mean percentage of MEP signal loss was 72.9%. The overall complication rate was 25.2%, and the incidence of new neurological deficits was 4.1%. On multivariate analysis, MEP signal loss of at least 50% was not associated with complication (p = 0.495) or able to predict postoperative neurological deficits (p = 0.429). Of the 38 cases in which MEP changes were observed, the observation represented a true-positive finding in only 3 cases. Postoperative neurological deficits without MEP changes occurred in 7 cases. Calculated measures of performance were as follows: sensitivity 30.0%, specificity 84.9%, positive predictive value 7.9%, and negative predictive value 96.6%. Regarding the specific characteristics of the MEP changes, only a signal loss of 80% or greater was significantly associated with a higher rate of neurological deficit (23.0% vs 0.0% for loss of less than 80%, p = 0.021); changes of less than 80% were not associated with postoperative deficits.

CONCLUSIONS

Neuromonitoring has a low positive predictive value and low sensitivity for detecting new neurological deficits. Even when neuromonitoring is unchanged, patients can still have new neurological deficits. The utility of transcranial MEP monitoring for lumbar PSO remains unclear but there may be advantages to its use.

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Justin S. Smith, Christopher I. Shaffrey, Christopher P. Ames and Lawrence G. Lenke

Care of the patient with adult spinal deformity (ASD) has evolved from being primarily supportive to now having the ability to directly treat and correct the spinal pathology. The focus of this narrative literature review is to briefly summarize the history of ASD treatment, discuss the current state of the art of ASD care with focus on surgical treatment and current challenges, and conclude with a discussion of potential developments related to ASD surgery.

In the past, care for ASD was primarily based on supportive measures, including braces and assistive devices, with few options for surgical treatments that were often deemed high risk and reserved for rare situations. Advances in anesthetic and critical care, surgical techniques, and instrumentation now enable almost routine surgery for many patients with ASD. Despite the advances, there are many remaining challenges currently impacting the care of ASD patients, including increasing numbers of elderly patients with greater comorbidities, high complication and reoperation rates, and high procedure cost without clearly demonstrated cost-effectiveness based on standard criteria. In addition, there remains considerable variability across multiple aspects of ASD surgery. For example, there is currently very limited ability to provide preoperative individualized counseling regarding optimal treatment approaches (e.g., operative vs nonoperative), complication risks with surgery, durability of surgery, and likelihood of achieving individualized patient goals and satisfaction. Despite the challenges associated with the current state-of-the-art ASD treatment, surgery continues to be a primary option, as multiple reports have demonstrated the potential for surgery to significantly improve pain and disability. The future of ASD care will likely include techniques and technologies to markedly reduce complication rates, including greater use of navigation and robotics, and a shift toward individualized medicine that enables improved counseling, preoperative planning, procedure safety, and patient satisfaction.

Advances in the care of ASD patients have been remarkable over the past few decades. The current state of the art enables almost routine surgical treatment for many types of ASD that have the potential to significantly improve pain and disability. However, significant challenges remain, including high complication rates, lack of demonstrated cost-effectiveness, and limited ability to meaningfully counsel patients preoperatively on an individual basis. The future of ASD surgery will require continued improvement of predictability, safety, and sustainability.

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Michael P. Kelly, Michael A. Kallen, Christopher I. Shaffrey, Justin S. Smith, Douglas C. Burton, Christopher P. Ames, Virginie Lafage, Frank J. Schwab, Han Jo Kim, Eric O. Klineberg, Shay Bess and the International Spine Study Group

OBJECTIVE

After using PROsetta Stone crosswalk tables to calculate Patient-Reported Outcomes Measurement Information System (PROMIS) Physical Function (PF) and Pain Interference (PI) scores, the authors sought to examine 1) correlations with Scoliosis Research Society–22r (SRS-22r) scores, 2) responsiveness to change, and 3) the relationship between baseline scores and 2-year follow-up scores in adult spinal deformity (ASD).

METHODS

PROsetta Stone crosswalk tables were used to converted SF-36 scores to PROMIS scores for pain and physical function in a cohort of ASD patients with 2-year follow-up. Spearman correlations were used to evaluate the relationship of PROMIS scores with SRS-22r scores. Effect size (ES) and adjusted standardized response mean (aSRM) were used to assess responsiveness to change. Linear regression was used to evaluate the association between baseline scores and 2-year follow-up scores.

RESULTS

In total, 425 (425/625, 68%) patients met inclusion criteria. Strong correlations (all |r| > 0.7, p < 0.001) were found between baseline and 2-year PROMIS values and corresponding SRS-22r domain scores. PROMIS-PI showed a large ES (1.09) and aSRM (0.88), indicating good responsiveness to change. PROMIS-PF showed a moderate ES (0.52) and moderate aSRM (0.69), indicating a moderate responsiveness to change. Patients with greater baseline pain complaints were associated with greater pain improvement at 2 years for both SRS-22r Pain (B = 0.39, p < 0.001) and PROMIS-PI (B = 0.45, p < 0.001). Higher functional scores at baseline were associated with greater average improvements in both SRS-22r Activity (B = 0.62, p < 0.001) and PROMIS-PF (B = 0.40, p < 0.001).

CONCLUSIONS

The authors found strong correlations between the SRS-22r Pain and Activity domains with corresponding PROMIS-PI and -PF scores. Pain measurements showed similar and strong ES and aSRM while the function measurements showed similar, moderate ES and aSRM at 2-year follow-up. These data support further exploration of the use of PROMIS–computer adaptive test instruments in ASD.

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Thomas J. Buell, Shay Bess, Ming Xu, Frank J. Schwab, Virginie Lafage, Christopher P. Ames, Christopher I. Shaffrey and Justin S. Smith

OBJECTIVE

Proximal junctional kyphosis (PJK) is, in part, due to altered segmental biomechanics at the junction of rigid instrumented spine and relatively hypermobile non-instrumented adjacent segments. Proper application of posteriorly anchored polyethylene tethers (i.e., optimal configuration and tension) may mitigate adjacent-segment stress and help prevent PJK. The purpose of this study was to investigate the impact of different tether configurations and tensioning (preloading) on junctional range-of-motion (ROM) and other biomechanical indices for PJK in long instrumented spine constructs.

METHODS

Using a validated finite element model of a T7–L5 spine segment, testing was performed on intact spine, a multilevel posterior screw-rod construct (PS construct; T11–L5) without tether, and 15 PS constructs with different tether configurations that varied according to 1) proximal tether fixation of upper instrumented vertebra +1 (UIV+1) and/or UIV+2; 2) distal tether fixation to UIV, to UIV−1, or to rods; and 3) use of a loop (single proximal fixation) or weave (UIV and/or UIV+1 fixation in addition to UIV+1 and/or UIV+2 proximal attachment) of the tether. Segmental ROM, intradiscal pressure (IDP), inter- and supraspinous ligament (ISL/SSL) forces, and screw loads were assessed under variable tether preload.

RESULTS

PS construct junctional ROM increased abruptly from 10% (T11–12) to 99% (T10–11) of baseline. After tethers were grouped by most cranial proximal fixation (UIV+1 vs UIV+2) and use of loop versus weave, UIV+2 Loop and/or Weave most effectively dampened junctional ROM and adjacent-segment stress. Different distal fixation and use of loop versus weave had minimal effect. The mean segmental ROM at T11–12, T10–11, and T9–10, respectively, was 6%, 40%, and 99% for UIV+1 Loop; 6%, 44%, and 99% for UIV+1 Weave; 5%, 23%, and 26% for UIV+2 Loop; and 5%, 24%, and 31% for UIV+2 Weave.

Tethers shared loads with posterior ligaments; consequently, increasing tether preload tension reduced ISL/SSL forces, but screw loads increased. Further attenuation of junctional ROM and IDP reversed above approximately 100 N tether preload, suggesting diminished benefit for biomechanical PJK prophylaxis at higher preload tensioning.

CONCLUSIONS

In this study, finite element analysis demonstrated UIV+2 Loop and/or Weave tether configurations most effectively mitigated adjacent-segment stress in long instrumented spine constructs. Tether preload dampened ligament forces at the expense of screw loads, and an inflection point (approximately 100 N) was demonstrated above which junctional ROM and IDP worsened (i.e., avoid over-tightening tethers). Results suggest tether configuration and tension influence PJK biomechanics and further clinical research is warranted.

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Justin K. Scheer, Taemin Oh, Justin S. Smith, Christopher I. Shaffrey, Alan H. Daniels, Daniel M. Sciubba, D. Kojo Hamilton, Themistocles S. Protopsaltis, Peter G. Passias, Robert A. Hart, Douglas C. Burton, Shay Bess, Renaud Lafage, Virginie Lafage, Frank Schwab, Eric O. Klineberg, Christopher P. Ames and the International Spine Study Group

OBJECTIVE

Pseudarthrosis can occur following adult spinal deformity (ASD) surgery and can lead to instrumentation failure, recurrent pain, and ultimately revision surgery. In addition, it is one of the most expensive complications of ASD surgery. Risk factors contributing to pseudarthrosis in ASD have been described; however, a preoperative model predicting the development of pseudarthrosis does not exist. The goal of this study was to create a preoperative predictive model for pseudarthrosis based on demographic, radiographic, and surgical factors.

METHODS

A retrospective review of a prospectively maintained, multicenter ASD database was conducted. Study inclusion criteria consisted of adult patients (age ≥ 18 years) with spinal deformity and surgery for the ASD. From among 82 variables assessed, 21 were used for model building after applying collinearity testing, redundancy, and univariable predictor importance ≥ 0.90. Variables included demographic data along with comorbidities, modifiable surgical variables, baseline coronal and sagittal radiographic parameters, and baseline scores for health-related quality of life measures. Patients groups were determined according to their Lenke radiographic fusion type at the 2-year follow-up: bilateral or unilateral fusion (union) or pseudarthrosis (nonunion). A decision tree was constructed, and internal validation was accomplished via bootstrapped training and testing data sets. Accuracy and the area under the receiver operating characteristic curve (AUC) were calculated to evaluate the model.

RESULTS

A total of 336 patients were included in the study (nonunion: 105, union: 231). The model was 91.3% accurate with an AUC of 0.94. From 82 initial variables, the top 21 covered a wide range of areas including preoperative alignment, comorbidities, patient demographics, and surgical use of graft material.

CONCLUSIONS

A model for predicting the development of pseudarthrosis at the 2-year follow-up was successfully created. This model is the first of its kind for complex predictive analytics in the development of pseudarthrosis for patients with ASD undergoing surgical correction and can aid in clinical decision-making for potential preventative strategies.

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Thomas J. Buell, Davis G. Taylor, Ching-Jen Chen, Christopher I. Shaffrey, Justin S. Smith and Shay Bess