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.

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.

Mechanical revision following pedicle subtraction osteotomy: a competing risk survival analysis in 171 consecutive adult spinal deformity patients.

STUDY DESIGN: Retrospective study. OBJECTIVE: To report the incidence of revision surgery due to mechanical failure following pedicle subtraction osteotomy (PSO) in adult spinal deformity (ASD) patients. PSO allow major surgical correction of ASD, although; the risk of mechanical complications remains considerable. Previous reports have been based on smaller cohorts or multicenter databases and none have utilized competing risk (CR) survival analysis. METHODS: All ASD patients undergoing PSO surgery from 2010 to 2015 at a single, tertiary institution were included. Demographics, long standing radiographs as well as intra- and postoperative complications were registered for all. A CR-model was used to estimate the incidence of revision surgery due to mechanical failure and two predefined multivariable models were used to assess radiographic prediction of failure and reported as odds ratios (OR) with 95% confidence intervals (95% CI). RESULTS: A total of 171 patients were included with 2-year follow-up available for 91% (mean [IQR]: 35 [24-50] months). Mechanical failure occurred in 111 cases (65%) at any time in follow-up, the most frequent being rod breakage affecting 81 patients (47%). Cumulative incidence of revision surgery due to mechanical failure was estimated to 34% at 2 years and 58% at 5 years. A multivariable proportional odds model with death as competing risk showed significantly increased odds of revision with fusion to the sacrum (OR: 5.42; 95% CI 1.89-15.49) and preoperative pelvic tilt (PT) > 20° (OR: 2.41; 95% CI 1.13-5.16). History of previous surgery, number of instrumented vertebra, as well as postoperative SRS-Schwab modifiers and Global Alignment and Proportion score were not associated with significant effects on odds of revision. CONCLUSIONS: In a consecutive single-center cohort of patients undergoing PSO for ASD, we found an estimated incidence of revision surgery due to mechanical failure of 34% 2 years postoperatively. Fusion to the sacrum and preoperative PT > 20° were associated with elevated risks of revision. LEVEL OF EVIDENCE: Prognostic III.

Minimal Access vs. Open Spine Surgery in Patients With Metastatic Spinal Cord Compression - A One-Center Randomized Controlled Trial.

BACKGROUND/AIM: We conducted a randomized controlled trial to investigate whether minimally access spine surgery (MASS) is less morbid than open surgery (OS) in patients with metastatic spinal cord compression (MSCC). PATIENTS AND METHODS: A total of 49 MSCC patients were included in the trial. The outcome measures were bleeding (L), operation time (min), re-operations and prolonged wound healing. RESULTS: The median age was 67 years (range=42-85 years) and 40% were men. The peri-operative blood loss in the MASS-group was significantly lower than that in the OS-group; 0.175L vs. 0.500L, (p=0.002). The median operation time for MASS was 142 min (range=72-203 min) vs. 103 (range=59-435 min) for OS (p=0.001). There was no significant difference between the two groups concerning revision surgery or delayed wound healing. CONCLUSION: The MASS technique in MSCC patients is associated with less blood loss, but a longer operation time when compared to the OS technique.

Surgical correction of Adult Spinal Deformity in accordance to the Roussouly classification: effect on postoperative mechanical complications.

STUDY DESIGN: Single-center, retrospective. OBJECTIVES: To assess the restoration of ideal sagittal spine shape in accordance to the Roussouly classification and the effect on postoperative mechanical complications. Surgical correction of Adult Spinal Deformity is both challenging and complex. The risk of postoperative complications is considerable, especially mechanical complications requiring revision surgery. Attention has been directed toward defining alignment targets in attempts to minimize these risks, and the Roussouly classification has been proposed as a potential surgical aim. METHODS: All patients undergoing ASD surgery from 2013-2016 were included at a single, quaternary institute. Successful restoration of Roussouly spine shape was retrospectively assessed, and patients were classified as either "restored" or "non-restored". Cumulative incidence of revision surgery due to mechanical failure was estimated using the Aalen-Johansen estimator, with death as the competing risk. A multivariable proportional odds model was used to estimate the effect of the Roussouly algorithm on revision surgery due to mechanical failure. RESULTS: We identified a complete and consecutive cohort of 233 patients who were followed for a mean period of 36 (± 14) months. The 2-year cumulative incidence of revision surgery was 28%. Comparing the "restored" to the "non-restored" group, the overall revision rates were high in both groups. However, when adjusting for known cofounders in a multivariable proportional odds analysis, there was an almost fivefold increased odds of revision due to mechanical failure in the "non-restored" group (p = 0.036). CONCLUSION: Surgical correction of ASD in accordance to the ideal Roussouly spine shape was correlated to a marked and significant decrease in risk of revision surgery due to mechanical failure. Nonetheless, the overall revision risk was elevated in both groups. LEVEL OF EVIDENCE: Therapeutic III.

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.

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.

A Comprehensive Analysis of the SRS-Schwab Adult Spinal Deformity Classification and Confounding Variables: A Prospective, Non-US Cross-sectional Study in 292 Patients.

STUDY DESIGN: Cross-sectional analyses on a consecutive, prospective cohort. OBJECTIVE: To evaluate the ability of the Scoliosis Research Society (SRS)-Schwab Adult Spinal Deformity Classification to group patients by widely used health-related quality-of-life (HRQOL) scores and examine possible confounding variables. SUMMARY OF BACKGROUND DATA: The SRS-Schwab Adult Spinal Deformity Classification includes sagittal modifiers considered important for HRQOL and the clinical impact of the classification has been validated in patients from the International Spine Study Group database; however, equivocal results were reported for the Pelvic Tilt modifier and potential confounding variables were not evaluated. METHODS: Between March 2013 and May 2014, all adult spinal deformity patients from our outpatient clinic with sufficient radiographs were prospectively enrolled. Analyses of HRQOL variance and post hoc analyses were performed for each SRS-Schwab modifier. Age, history of spine surgery, and aetiology of spinal deformity were considered potential confounders and their influence on the association between SRS-Schwab modifiers and aggregated Oswestry Disability Index (ODI) scores was evaluated with multivariate proportional odds regressions. P values were adjusted for multiple testing. RESULTS: Two hundred ninety-two of 460 eligible patients were included for analyses. The SRS-Schwab Classification significantly discriminated HRQOL scores between normal and abnormal sagittal modifier classifications. Individual grade comparisons showed equivocal results; however, Pelvic Tilt grade + versus +  + did not discriminate patients according to any HRQOL score. All modifiers showed significant proportional odds for worse aggregated ODI scores with increasing grade levels and the effects were robust to confounding. However, age group and aetiology had individual significant effects. CONCLUSION: The SRS-Schwab sagittal modifiers reliably grouped patients graded 0 versus + / +  + according to the most widely used HRQOL scores and the effects of increasing grade level on odds for worse ODI scores remained significant after adjusting for potential confounders. However, effects of age group and aetiology should not be neglected. LEVEL OF EVIDENCE: 3.