Postoperative lordosis distribution index, patient reported outcome measures, and revision surgery following transforaminal lumbar interbody fusion

Objective

Lordosis Distribution Index (LDI) is a new radiographic parameter associated with postoperative residual symptoms in patients undergoing Transforaminal Lumbar Interbody Fusion (TLIF). Recently, it has been applied on patients undergoing instrumented spine surgery, however not correlated to Patient Related Outcome Measures (PROMs). This study investigates whether the obtained the postoperative LDI after TLIF surgery correlates with the clinical outcome measured with PROMs.

Methods

This study was based on prospectively obtained data in patients undergoing TLIF throughout 2017 at a Danish university hospital. Medical records and the DaneSpine Database were accessed to obtain preoperative, operative and follow-up data. Primary outcome was Oswestry Disability Index (ODI) 12 months postoperatively. Secondary outcomes included revision rate and additional PROMs.

Results

126 patients were included. 70 patients were classified with normolordosis (56 %), 42 hypolordosis (33 %) and 14 hyperlordosis (11 %). All groups experienced significant radiological changes undergoing surgery. Average reduction in ODI at 12 months postoperatively was -15.3 (±20.0). Minimally clinical important difference was achieved in 68 patients (54.0 %). No significant difference in PROMs between LDI-groups was observed in unadjusted or adjusted analyses. Revision surgery was performed in 8 patients with normolordosis (11.4 %), 7 hypolordosis (16.7 %) and 4 hyperlordosis (28.6 %).

Conclusions

We found no significant correlation between postoperative LDI subgroups of normolordotic, hypo- or hyperlordotic patients and the clinical outcome of posterolateral fusion and TLIF surgery. A trend towards lower rate of revision surgery in the normolordotic group compared to the hypo- and hyperlordotic group was observed.

30-and 90-day readmissions in lumbar spine surgery. Differences in prevalence and causes

BACKGROUND

The morbidity associated with surgical treatment of lumbar degenerative conditions has attracted increasing interest due to the economic impact on society, especially postoperative readmission. Limited studies have assessed this risk in a prospective, single-center consecutive fashion.

OBJECTIVE

To assess the incidence and causes of 30- and 90-day unplanned readmission and revision surgery following surgical treatment for lumbar degenerative spine conditions at a tertiary treatment center.

STUDY DESIGN

Prospective, single-center cohort study.

METHODS

All patients undergoing degenerative lumbar spine surgery in a 1-year period from February 1st, 2016, were prospectively included. Patient characteristics, surgical information and information regarding postoperative complications, including readmission (30- and 90-days) and revision surgery were recorded. Readmissions were classified according to whether they were due to the surgical intervention specifically, or a medical complication.

RESULTS

A total of 1399 patients underwent surgery for various lumbar degenerative pathologies in the study period and all were included. Of these, 9.4% (n = 132) were readmitted within 30 days of surgery and in some cases, multiple readmissions occurred (up to 3). The total 90-day readmission rate was 17.6%. Of these, 15% were related to the surgical procedure. The predominant medical related causes were systemic infection (30-day: 14.4%, 90-day: 10.7%), neurological symptoms (30-day: 6.3%, 90-day: 5.0%) and cardiovascular events (30-day: 8.1%, 90-day: 12.9%). The surgical related causes for readmission were pain (30-day: 13.1%, 90-day: 2.9%), wound complications (30-day: 11.3%, 90-day: 5.0% and re-herniation (30-day: 13.1%, 90-day: 2.9%). Age was the only factor with significant influence on readmission.

CONCLUSION

The incidence of medical conditions causing unplanned 30-day readmissions following surgery for lumbar degenerative conditions, is significantly higher compared to readmissions related specifically to the surgical procedure. Examples of medical treatment included antibiotics, analgesics, laxatives, anticoagulants and beta blockers. The difference is even more pronounced for the 90-day readmissions. The predominant medical causes were systemic infections, neurological and cardiovascular events. Predominant causes related to the surgery were pain, wound complications and re-herniations. Readmissions may be reduced by optimizing the medical treatment and the pain management before discharge of the patient.

The Collateral Effect of Enhanced Recovery After Surgery Protocols on Spine Patients With Neuromuscular Scoliosis

INTRODUCTION

Enhanced recovery after surgery (ERAS) protocols are often specific to a specific type of surgery without assessing the overall effect on the ward. Previous studies have demonstrated reduced length of stay (LOS) with ERAS protocols in patients with adolescent idiopathic scoliosis (AIS), although the patients are often healthy and with few or no comorbidities. In 2018, we used ERAS principles for patients undergoing AIS surgery with a subsequent 40% reduced LOS. The current study aims to assess the potential collateral effect of LOS in patients surgically treated for neuromuscular scoliosis admitted to the same ward and treated by the same staff but without a standardized ERAS protocol.

METHODS

All patients undergoing neuromuscular surgery 2 years before and after ERAS introduction (AIS patients) with a gross motor function classification score of 4 to 5 were included. LOS, intensive care stay, and postoperative complications were recorded. After discharge, all complications leading to readmission and mortality were noted with a minimum of 2 years of follow-up using a nationwide registry.

RESULTS

Forty-six patients were included; 20 pre-ERAS and 26 post-ERAS. Cross groups, there were no differences in diagnosis, preoperative curve size, pulmonary or cardiac comorbidities, weight, sex, or age. Postoperative care in the intensive care unit was unchanged between the two groups (1.2 vs 1.1; P = 0.298). When comparing LOS, we found a 41% reduction in the post-ERAS group (11 vs 6.5; P < 0.001) whereas the 90-day readmission rates were without any significant difference (45% vs 34% P = 0.22) We found no difference in the 2-year mortality in either group.

CONCLUSION

The employment of ERAS principles in a relatively uncomplicated patient group had a positive, collateral effect on more complex patients treated in the same ward. We believe that training involving the caregiving staff is equally important as pharmacological protocols.

Demineralized cortical fibers are associated with a low pseudarthrosis rate in patients undergoing surgery for adult spinal deformity without three-column osteotomy

Introduction

Following surgical treatment for adult spinal deformity (ASD) there is an increased risk of revision surgery due to mechanical failure or pseudarthrosis. Demineralized cortical fibers (DCF) were introduced at our institution aiming to reduce the risk of pseudarthrosis after ASD surgery.

Research question

We wanted to investigate the effect of DCF on postoperative pseudarthrosis compared with allogenic bone graft in ASD surgery without three-column osteotomies (3CO).

Materials & Methods

All patients undergoing ASD surgery between January 1, 2010 to June 31, 2020 were included in this interventional study with historical controls. Patients with current or previous 3CO were excluded. Before February 1, 2017, patients undergoing surgery received auto- and allogenic bone graft (non-DCF group) whilst patients after received DCF in addition to autologous bone graft (DCF group). Patients were followed for at least two years. The primary outcome was radiographic or CT-verified postoperative pseudarthrosis requiring revision surgery.

Results

We included 50 patients in the DCF group and 85 patients in the non-DCF group for final analysis. Pseudarthrosis requiring revision surgery at two-year follow-up occurred in seven (14%) patients in the DCF group compared with 28 (33%) patients in the non-DCF group (p ​= ​0.016). The difference was statistically significant, corresponding to a relative risk of 0.43 (95%CI: 0.21-0.94) in favor of the DCF group.

Conclusion

We assessed the use of DCF in patients undergoing ASD surgery without 3CO. Our results suggest that the use of DCF was associated with a considerable decreased risk of postoperative pseudarthrosis requiring revision surgery.

Is preoperative S-albumin associated to postoperative complications and readmission in patients with adult spinal deformity: a prospective analysis of 128 patients using the Spine AdVerse Event Severity (SAVES) system

PURPOSE

To assess the association between preoperative S-albumin and postoperative outcome following adult spinal deformity (ASD) surgery.

METHODS

All patients undergoing ASD surgery from February 1, 2017 and January 31, 2018 at a single quaternary referral center were prospectively included. Adverse events (AE) during admission were assessed using the Spine AdVerse Events Severity (SAVES) system. Based on preoperative S-albumin, patients were categorized as "normal" or "abnormal" and compared regarding postoperative outcome, adverse events (AEs), 30- and 90-day readmission, revision surgery, and mortality.

RESULTS

A total of 128 patients aged ≥ 18 years were included, and S-albumin was available in 88%. Of these, 73% (n = 93) were classified as "normal", 16% (n = 20) as "abnormal", and 12% (n = 15) as "missing". The "normal" albumin group had less comorbidity burden [ASA score 2 (2, 3) vs 3 (2, 3), p = 0.011], higher hemoglobin levels (8.4 (± 0.9) mmol/L vs 7.4 (± 1.1) mmol/L, p < 0.001), and higher S-albumin (38.9 (± 2.7) g/L vs 31.9 (± 4.4) g/L, < 0.001). The rate of 90-day readmission was significantly increased in the "abnormal" group (65% vs 36%), corresponding to a relative risk increase of 1.25 (95% CI 1.02-1.52, p = 0.029). Similar increased risks were found in subsequent logistic regression analyses, although results were not significant in multivariable analysis (p = 0.102). Comparing remaining outcome parameters, point estimates revealed increased AEs, 30-day readmission, and revision in the "abnormal" albumin group, although effects did not reach statistical significance.

CONCLUSIONS

In a prospective, consecutive, single-center cohort of 128 patients undergoing ASD surgery, we found a significant association between "abnormal" preoperative S-albumin and increased 90-day readmission. Furthermore, although the findings were not statistically significant, we did find that AEs, 30-day readmission, and revision were numerically more frequent in the "abnormal" group, suggesting an expected tendency that should be further investigated. We conclude that nutritional status prior to ASD surgery could be important to consider and suggest validation in larger prospective cohorts.

LEVEL OF EVIDENCE

Prognostic II.

Use of demineralized cortical fibers is associated with reduced risk of pseudarthrosis after pedicle subtraction osteotomy for adult spinal deformity

PURPOSE

To assess the effect of demineralized cortical fibers (DCF) on postoperative pseudarthrosis requiring revision surgery in patients undergoing pedicle subtraction osteotomy (PSO) for adult spinal deformity (ASD).

METHODS

The use of DCF was introduced across all procedures in 2017 and subsequent patients undergoing PSO surgery were prospectively and consecutively registered. Following sample-size estimation, a retrospective cohort was also registered undergoing the same procedure immediately prior to the implementation of DCF. The non-DCF group underwent surgery with ABG. Minimum follow-up was 2 years in both groups. The main outcome was postoperative pseudarthrosis, either CT-verified or verified intraoperatively during revision surgery due to rod breakage and assessed using Kaplan-Meier survival analyses.

RESULTS

A total of 48 patients were included in the DCF group and 76 in the non-DCF group. The DCF group had more frequently undergone previous spine surgery (60% vs 36%) and had shorter follow-up (32 ± 2 vs 40 ± 7 months). Pseudarthrosis occurred in 7 (15%) patients in the DCF group and 31 (41%) in the non-DCF group, corresponding to a relative risk increase of 2.6 (95%CI 1.3-2.4, P < 0.01). 1-KM survival analyses, taking time to event into account and thus the difference in follow-up, also showed increased pseudarthrosis in the non-DCF group (log-rank P = 0.022). Similarly, multivariate logistic regression adjusted for age, instrumented levels and sacral fusion was also with significantly increased odds of pseudarthrosis in the non-DCF group (OR: 4.3, 95%CI: 1.7-11.3, P < 0.01).

CONCLUSION

We found considerable and significant reductions in pseudarthrosis following PSO surgery with DCF compared to non-DCF.

LEVEL OF EVIDENCE

III.

Rapid discharge protocol reduces length of stay and eliminates postoperative nausea and vomiting after surgery for adolescent idiopathic scoliosis

BACKGROUND

Implementing standardized pathways following adolescent idiopathic scoliosis surgery have been shown to reduce length of stay (LOS). However, controversies still exist. This applies especially to the transition to solid foods, postoperative pruritus and postoperative nausea and vomiting (PONV). The aim of this proposed protocol is to present an option to reduce these factors while reducing the LOS.

METHODS

The protocol was designed with reduction of morphine. One-hundred-eight patients were included in this study, including sixty-six controls prior to intervention. All underwent posterior scoliosis surgery. All patients were scored daily using a Numeric rating scale (NRS) and noted if any nausea, vomiting or pruritus was present. All medications were recorded. For every twenty patients included the steering committee met to identify any implementation issues.

RESULTS

LOS was reduced from 6.3 to 3.6 days (43% reduction, P=0.003). PONV was reduced from affecting 82% to 9% of patients (P<0.0001). Patients experiencing postoperative pruritus were reduced from 40% to 2%. (P<0.001). Time spent in postoperative recovery was reduced from 278[117-470] mins to 199[128-643], P<0.001. Patient´s pain scores remained unchanged compared to controls (mean 4[3-8]). We found no adverse effects of solid food intake from postoperative day 0 CONCLUSION: We found a significant reduction in length of stay, postoperative nausea and vomiting and pruritus after implementation of the protocol. This allowed for no restrictions in regards to solid food intake postoperatively.

Lordosis Distribution Index in Short-Segment Lumbar Spine Fusion - Can Ideal Lordosis Reduce Revision Surgery and Iatrogenic Deformity?

OBJECTIVE

The demand for spinal fusion is increasing, with concurrent reports of iatrogenic adult spinal deformity (flatback deformity) possibly due to inappropriate lordosis distribution. This distribution is assessed using the lordosis distribution index (LDI) which describes the upper and lower arc lordosis ratio. Maldistributed LDI has been associated to adjacent segment disease following interbody fusion, although correlation to later-stage deformity is yet to be assessed. We therefore aimed to investigate if hypolordotic lordosis maldistribution was associated to radiographic deformity-surrogates or revision surgery following instrumented lumbar fusion.

METHODS

All patients undergoing fusion surgery ( ≤ 4 vertebra) for degenerative lumbar diseases were retrospectively included at a single center. Patients were categorized according to their postoperative LDI as: "normal" (LDI 50-80), "hypolordotic" (LDI < 50), or "hyperlordotic" (LDI > 80).

RESULTS

We included 149 patients who were followed for 21 ± 14 months. Most attained a normally distributed lordosis (62%). The hypolordotic group had increased postoperative pelvic tilt (PT) (p < 0.001), pelvic incidence minus lumbar lordosis (PI-LL) mismatch (p < 0.001) and decreased global lordosis (p = 0.007) compared to the normal group. Survival analyses revealed a significant difference in revision surgery (p = 0.03), and subsequent multivariable logistic regression showed increased odds of 1-year revision in the hypolordotic group (p = 0.04). There was also a negative, linear correlation between preoperative pelvic incidence (PI) and postoperative LDI (p < 0.001).

CONCLUSION

In patients undergoing instrumented lumbar fusion surgery, hypolordotic lordosis maldistribution (LDI < 50) was associated to increased risk of revision surgery, increased postoperative PT and PI-LL mismatch. Lordosis distribution should be considered prior to spinal fusion, especially in high PI patients.

Reducing revision rates following Pedicle Subtraction Osteotomy surgery: a single-center experience of trends over 7 years in patients with Adult Spinal Deformity

STUDY DESIGN

This is a single-center, retrospective study.

OBJECTIVE

To assess if implemented changes to clinical practice have reduced mechanical complications following pedicle subtraction osteotomy (PSO) surgery. Adult spinal deformity (ASD) is increasing in prevalence with concurrent increasing demands for surgical treatment. The most extensive technique, PSO, allows for major correction of rigid deformities. However, surgery-related complications have been reported in rates up to 77% and especially mechanical complications occur at unsatisfactory frequencies.

METHODS

We retrospectively included all patients undergoing PSO for ASD between 2010 and 2016. Changes to clinical practice were introduced continuously in the study period, including rigorous patient selection; inter-disciplinary conferences; implant-material; number of surgeons; surgeon experience; and perioperative standardized protocols for pain, neuromonitoring and blood-loss management. Postoperative complications were recorded in the 2-year follow-up period. Competing risk survival analysis was used to assess cumulative incidence of revision surgery due to mechanical complications. The Mann-Kendall test was used for analysis of trends.

RESULTS

We included 185 patients undergoing PSO. The level of PSO changed over the study period (P < 0.01) with L3 being the most common level in 2010 compared to L4 in 2016. Both preoperative and surgical corrections of sagittal vertical axis were larger towards the end of the study period. The 2-year revision rate due to mechanical failure steadily declined over the study period from 52% in 2010 to 14% for patients treated in 2016, although without statistically significant trend (P = 0.072). In addition, rates of mechanical complications steadily declined over the study period and significant decreasing trends were observed in time trend analyses of overall complications, major complications and rod breakage.

CONCLUSIONS

We observed decreased risks of revision surgery due to mechanical complications following PSO in patients with ASD over a 7-year period. We attribute these improvements to advancements in patient selection, surgical planning and techniques, surgeon experience and more standardized perioperative care.

LEVEL OF EVIDENCE

III.

A Comparison of Mortality and Morbidity Between Complex and Degenerative Spine Surgery in Prospectively Collected Data From 2280 Procedures

Objective

The reported incidence of complications and/or adverse events (AEs) following spine surgery varies greatly. A validated, systematic, reproducible reporting system to quantify AEs was used in 2 prospective cohorts, from 2 spine surgery centers, conducting either complex or purely degenerative spine surgery; in a comparative fashion. The aim was to highlight the differences between 2 distinctly different prospective cohorts with patients from the same background population.

Methods

AEs were registered according to the predefined AE variables in the SAVES (Spine AdVerse Events Severity) system which was used to record all intra- and perioperative AEs. Additional outcomes, including mortality, length of stay, wound infection requiring revision, readmission, and unplanned revision surgery during the index admission, were also registered.

Results

A total of 593 complex and 1,687 degenerative procedures were consecutively included with 100% data completion. There was a significant difference in morbidity when comparing the total number of AEs between the 2 groups (p < 0.001): with a mean number of 1.42 AEs per patient (n = 845) in the complex cohort, and 0.97 AEs per patient (n = 1,630) in the degenerative cohort.

Conclusion

In this prospective study comparing 2 cohorts, we report the rates of AEs related to spine surgery using a validated reproducible grading system for registration. The rates of morbidity and mortality were significantly higher following complex spine surgery compared to surgery for degenerative spine disease.

Morbidity and mortality following degenerative spine surgery in a prospective cohort of 1687 consecutive surgical procedures

STUDY DESIGN

Prospective, observational cohort study.

OBJECTIVE

To determine the true incidence of adverse events (AEs) in European adults undergoing surgery for degenerative spine diseases. The majority of surgeries performed for degenerative spinal diseases are elective, and the need for adequate estimation of risk-benefit of the intended surgery is imperative. A cumbersome obstacle for adequate estimation of surgery-related risks is that the true incidence of complications or adverse events (AEs) remains unclear.

METHODS

All adult patients (≥ 18 years) undergoing spine surgery at a single center from February 1, 2016, to January 31, 2017, were prospectively and consecutively included. Morbidity and mortality were determined using the Spine AdVerse Events Severity (SAVES) system. Additionally, the correlation between the AEs and length of stay (LOS) and mortality was assessed.

RESULTS

A total of 1687 procedures were performed in the study period, and all were included for analysis. Of these, 1399 (83%) were lumbar procedures and 288 (17%) were cervical. The overall incidence of AEs was 47.4%, with a minor AE incidence of 43.2% and a major of 14.5%. Female sex (OR 1.5 [95% CI 1.2-1.9), p < 0.001) and age > 65 years (OR 1.5 [95% CI 1.1-1.7], p = 0.012) were significantly associated with increased odds of having an AE.

CONCLUSION

Based on prospectively registered AEs in this single-center study, we validated the use of the SAVES system in a European population undergoing spine surgery due to degenerative spine disease. We found a higher incidence of AEs than previously reported in retrospective studies. The major AEs registered occurred significantly more often perioperatively and in patients > 65 years.

Revision surgery and mortality following complex spine surgery: 2-year follow-up in a prospective cohort of 679 patients using the Spine AdVerse Event Severity (SAVES) system

STUDY DESIGN

Prospective study.

OBJECTIVE

To determine the 2-year risk of revision surgery and all-cause mortality after complex spine surgery, and to assess if prospectively registered adverse events (AE) could predict either outcome. Revision surgery and mortality are serious complications to spine surgery. Previous studies of frequency have mainly been retrospective and few studies have employed competing risk survival analyses. In addition, assessment of predictors has focused on preoperative patient characteristics. The effect of perioperative AEs on revision and all-cause mortality risks are not fully understood.

METHODS

Between January 1 and December 31, 2013, we prospectively included all patients undergoing complex spine surgery at a single, tertiary institution. Complex spine surgery was defined as conditions deemed too complicated for surgery at a secondary institute, or patients with severe comorbidities requiring multidisciplinary observation and treatment. AEs were registered using the Spine Adverse Event Severity system and patients were followed for minimum 2 years regarding revision surgery and all-cause mortality. Incidences were estimated using competing risk survival analyses and correlation between AEs and either outcome was assessed using proportional odds models.

RESULTS

We included a complete and consecutive cohort of 679 adult and pediatric patients. Demographics, surgical data, AEs, and events of revision or all-cause mortality were registered. The cumulative incidence of 2-year all-cause revision was 19% (16-22%) and all-cause mortality was 15% (12-18%). Deformity surgery was the surgical category with highest incidence of revision and the highest incidence of all-cause mortality was seen in the tumor group. Across surgical categories, cumulative incidences of 2-year revision ranged between 11% (tumor) and 33% (deformity), whilst 2-year all-cause mortality ranged between 3% (deformity) and 33% (tumor). We found that major intraoperative AEs were associated to increased odds of revision. Deep wound infection was associated to increased odds of all-cause mortality.

CONCLUSIONS

We report the cumulative incidences of revision surgery and all-cause mortality following complex spine surgery. We found higher incidences of revision compared to previous retrospective studies. Prospectively registered AEs were correlated to increased odds of revision surgery and all-cause mortality. These results may serve as reference for future interventional studies and aid in identifying at-risk patients.

LEVEL OF EVIDENCE

I.

Spinopelvic Parameters Depending on the Angulation of the Sacral End Plate Are Less Reproducible Than Other Spinopelvic Parameters in Adult Spinal Deformity Patients

STUDY DESIGN

Reproducibility study.

OBJECTIVES

To report the agreement and reliability for commonly used sagittal plane measurements.

SUMMARY OF BACKGROUND DATA

Spinopelvic parameters and sagittal vertical axis (SVA) are commonly used parameters for preoperative planning and postoperative evaluation of patients with adult spinal deformity (ASD). Previous reproducibility studies have focused on describing the reliability using intraclass correlation coefficients (ICCs), thus quantifying the methods' ability to distinguish between individuals. To our knowledge, no previous study in patients with ASD has reported the measurement error in terms of limits of agreement. The current study aimed to report the agreement and reliability for measurements of pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), and SVA in ASD patients.

METHODS

In a consecutive, one-center cohort of 64 patients referred for ASD evaluation, a blinded test-retest study was performed. Reliability was assessed using ICCs, whereas 95% limits of agreement (LOAs) were used to quantify agreement.

RESULTS

We found "excellent" (ICC > 0.9) results in all analyses of reliability except for interrater PI, which was classified as "good" (ICC = 0.89). However, considerable interrater measurement error was observed for parameters depending on the angulation of the sacral end plate (95% LOA of ±11° and ±14° for SS and PI, respectively) compared with ±5° for PT and ±7 mm for SVA, which depends on the location of the sacral end plate. Intrarater agreement was only slightly better.

CONCLUSION

These are to our knowledge the first estimates of measurement error for sagittal spinopelvic parameters in ASD patients. Despite near excellent ICCs, we found considerable measurement error for parameters depending on the angulation rather than the location of the sacral end plate.

LEVEL OF EVIDENCE

Level II.

Ability of the Global Alignment and Proportion Score to Predict Mechanical Failure Following Adult Spinal Deformity Surgery-Validation in 149 Patients With Two-Year Follow-up

STUDY DESIGN

Retrospective analysis of prospectively collected data.

OBJECTIVES

To validate the Global Alignment and Proportion (GAP) score in a single-center cohort of adult spinal deformity (ASD) patients.

SUMMARY OF BACKGROUND DATA

Surgical treatment for ASD is associated with a high risk of mechanical failure and consequent revision surgery. To improve prediction of mechanical complications, the GAP score was developed with promising results. Development was based on the assumption that not all patients would benefit from the same fixed radiographic targets as pelvic incidence is an individual, morphological parameter that greatly influences the sagittal curves of the spine.

METHODS

In a validation study of the GAP score, patients undergoing ASD surgery with four or more levels of instrumentation were consecutively included at a tertiary spine unit. Patients were followed for a minimum of two years. Pre- and postoperative GAP score and categories were calculated for all patients, and the association with mechanical failure and revision surgery was analyzed.

RESULTS

A total of 149 patients with a mean age of 57.4 years were included. Overall, the rates of mechanical failure and revision surgery were 51% and 35% respectively. The area under the curve (AUC) using receiver operating characteristic was classified as "no or low discriminatory power" for the GAP score in predicting either outcome (AUC = 0.50 and 0.49, respectively). Similarly, there were no significant associations between GAP categories and the occurrence of mechanical failure or revision surgery when using Cochran-Armitage test of trend (p = .28 for mechanical failure and p = .58 for revision surgery).

CONCLUSIONS

In a consecutive series of surgically treated ASD patients, we found no significant association between postoperative GAP score and mechanical failure or revision surgery. Despite minor limitations in similarities to the original study cohort, further validation studies or adjustments to the original scoring system are proposed.

LEVEL OF EVIDENCE

Level II.

Moderate Interrater and Substantial Intrarater Reproducibility of the Roussouly Classification System in Patients With Adult Spinal Deformity

STUDY DESIGN

Reproducibility study of a classification system.

OBJECTIVES

To provide the inter- and intrarater reproducibility of the Roussouly Classification System in a single-center prospective cohort of patients referred for Adult Spinal Deformity.

SUMMARY OF BACKGROUND DATA

The Roussouly Classification System was developed to describe the variation in sagittal spine shape in normal individuals. A recent study suggests that patients' spine types could influence the outcome following spinal surgery. The utility of a classification system depends largely on its reproducibility.

METHODS

Sixty-four consecutive patients were included in a blinded test-retest setting using digital radiographs. All ratings were performed by four spine surgeons with different levels of experience. There was a 14-day interval between the two reading sessions. Inter- and intrarater reproducibility was calculated using Fleiss Kappa and crude agreement percentages.

RESULTS

We found moderate interrater (κ = 0.60) and substantial intrarater (κ = 0.68) reproducibility. All 4 raters agreed on the Roussouly type in 47% of the cases. The most experienced rater had significantly higher intrarater reliability compared to the least experienced rater (κ = 0.57 vs 0.78). The two most experienced raters also had the highest crude agreement percentage (75%); however, they also had a significant difference in distribution of spine types.

CONCLUSION

The current study presents moderate interrater and substantial intrarater reliability of the Roussouly Classification System. These findings are acceptable and comparable to previous results of reproducibility for a classification system in patients with Adult Spinal Deformity. Additional studies are requested to validate these findings as well as to further investigate the impact of the classification system on outcome following surgery.