Which Global Sagittal Parameter Could Most Effectively Predict the Surgical Outcome for Patients With Adult Degenerative Scoliosis?

Study design Retrospective study. Objective To evaluate the predictive effect of the 3 global sagittal parameters (Sagittal Vertical Axis [SVA], T1 Pelvic Angle [TPA], and relative TPA [rTPA]) in the surgical outcome of patients with adult degenerative scoliosis (ADS), then to define the optimum corrective goal based on the best of them. Methods 117 ADS patients were included in this study and followed-up for an average of 3 years. Functional evaluation and radiographs were assessed preoperatively and postoperatively. The predictive accuracy of SVA, TPA, and relative TPA was analyzed through receiver operating characteristic (ROC) curve. The cutoff value of TPA was obtained at the maximal Youden index from ROC curve. Results TPA most highly correlated with postoperative oswestry disability index (ODI). The best cutoff value of TPA was set at 19.3° (area under curve =0.701). TPA >19.3° was the highest risk factor in multivariate logistic regression analysis (OR = 7.124, P = 0.022). Patients with TPA <19.3° at 3 months after operation showed a better ODI than those with TPA >19.3°. Correcting TPA less than 19.3° for patients with preoperative TPA >19.3° attributed to a better health related quality of life (HRQOL) and sagittal balance at last follow-up. The formula “Postoperative TPA = 0.923 × PI - 0.241 × postoperative LL - 0.593 × postoperative SS - 2.471 ( r = 0.914, r2 = 0.836, P < .001)” described the relation between SS, LL, PI, and TPA. Conclusion TPA was a useful global parameter for the prediction of postoperative HRQOL for patients with ADS. Keeping TPA <19.3° could improve the postoperative HRQOL for ADS patients with preoperative TPA >19.3°, and TPA <19.3° could be an optimum correction target for patients with ADS.

Which sagittal evaluation system can effectively predict mechanical complications in the treatment of elderly patients with adult degenerative scoliosis? Roussouly classification or Global Alignment and Proportion (GAP) Score

Background To achieve the proper sagittal alignment, previous studies have developed different assessment systems for adult degenerative scoliosis (ADS) which could help the spine surgeon in making treatment strategies. The purpose of our study is to evaluate whether Roussouly classification or global alignment and proportion (GAP) score is more appropriate in the prediction of mechanical complications after surgical treatment of ADS. Methods ADS patients who received long segmental fusion in the treatment during the period from December 2016 to December 2018 were evaluated in this study. Basic information and radiologic measurements were collected for analysis. Patients were divided into two groups according to occurrence or absence of mechanical complications for comparison. Mechanical complications included proximal junctional kyphosis (PJK), proximal junctional failure (PJF). GAP categories divided GAP score into proportioned spinopelvic position, moderately disproportioned position, and severely disproportioned position according to the cut-off values. The correlation between evaluation systems and mechanical complications was analyzed through a logistic regression model via stepwise backward elimination based on the Wald statistics. Receiver operator characteristic (ROC) curve was used to determine the predictability of the evaluation systems in the occurrence of mechanical complications and calculate their cut-off value. Area under the curve (AUC) was used to evaluate the validity of the thresholds. Results A total of 80 patients were included in this study. There were 41 patients in mechanical complication group and 39 patients in no mechanical complication group. GAP score (P = 0.008) and GAP categories (P = 0.007) were positively correlated with mechanical complications; Roussouly score was negatively correlated with mechanical complications (P = 0.034); GAP score was positively correlated with PJK (P = 0.021); Roussouly score was negatively correlated with implant-related complications (P = 0.018); GAP categories were correlated with implant loosening (P = 0.023). Results of ROC showed that GAP score was more effective in predicting PJK (AUC = 0.863) and PJF (AUC = 0.724) than Roussouly score; GAP categories (AUC = 0.561) was more effective than GAP score (AUC = 0.555) in predicting implant-related complications. Conclusions Roussouly classification could only be a rough estimate of optimal spinopelvic alignment. Quantitative parameters in GAP score made it more effective in predicting mechanical complications, PJK and PJF than Roussouly classification.

Robotic Sacroiliac Fixation Technique for Triangular Titanium Implant in Adult Degenerative Scoliosis Surgery: 2-Dimensional Operative Video

Corrective surgery remains a definitive treatment for adult spinal deformity, improving pain and disability. With these cases, instrumentation to the pelvis with iliac fixation is recommended. Whether iliac or S2-Alar-Iliac (S2AI) trajectories are used, sacroiliac joint pain and long-term sacroilitis can be common after long-fusion constructs.1-3 Sacroiliac fusion with triangular titanium implants during fusion can reduce back pain associated with sacroiliac joint degeneration,3 provides reduction in sacroiliac joint motion and stress when added to S2AI screws, and potentially enhances mechanical stability of fusion constructs.4 Here, we present a technique for placing triangular titanium sacroiliac implants (iFuse BedrockTM; SI-BONE Inc, Santa Clara, California) alongside S2AI screws using a robotic platform (Mazor X; Medtronic Sofamor Danek, Medtronic Inc, Dublin, Ireland). Navigated robotics allows reduction in human error with implant placement, and potentially decreased operative time/fluoroscopy.5-7 Key surgical steps include placement of K wires for S2AI and bilateral SI-implants, tapping, replacing SI-implant K wires with guide pins, placing S2AI screws, and finally placing the SI-implant. Final placement is verified with intraoperative fluoroscopy. The patient described is a 61-yr-old woman with worsening adult degenerative scoliosis, lower back pain, left leg radicular pain, and mild right leg pain who failed conservative treatment. Examination revealed diminished strength in both legs. Imaging was significant for moderate sigmoid scoliosis, discogenic disease, and osteoarthritis at all levels. She consented to undergo corrective surgery. Postoperatively, the patient experienced resolution of her leg weakness and pain. Imaging demonstrated appropriate positioning of hardware. Prospective studies on the efficacy of the SI-implant are underway.

Minimally Invasive Interlaminar Decompression with a 10-mm Endoscope and Microscope in Cases of Adult Degenerative Scoliosis

BACKGROUND: Adult degenerative (de novo) scoliosis (ADS) usually occurs due to degenerative changes and is accompanied by progressive low-back pain and/or symptomatic lumbar stenosis. Interlaminar decompression is considered an effective treatment of lumbar stenosis, but some surgical contraindications to traditional open surgery limit its application in elderly patients with many disorders. A 10-mm endoscope has been used in the treatment of stenosis in individuals with ADS and its safety and efficacy should be assessed. OBJECTIVE: The objective was to conduct a retrospective analysis to compare interlaminar decompression with a 10-mm endoscope versus a microscope. STUDY DESIGN: Retrospective study. SETTING: This study took place at the First Affiliated Hospital of Harbin Medical University. METHODS: The data of 34 ADS patients treated in our hospital from January 2018 to December 2019, who underwent decompression with a 10-mm endoscope (ES group, 19 patients) or microscope (MS group, 15 patients) were retrospectively reviewed. The two methods were compared using the visual analog scale (VAS), Japanese orthopedic association (JOA) scale, and Oswestry disability index (ODI). Lumbar stability was also evaluated by the progression of scoliosis. RESULTS: There were no significant differences between the 2 groups in demographic or clinical characteristics. The mean preoperative Cobb angle of all patients was 23.34° ± 6.44°, which indicated degenerative scoliosis. The mean JOA and ODI scores were 8.09 ± 1.44 and 55.47 ± 11.91. The mean preoperative pelvic incidence (PI) and lumbar lordosis (LL) angles were 51.02° ± 7.21 and 38.26° ± 6.98 and the mean PI-LL mismatch was 12.76° ± 5.63. There was no significant difference in the VAS scores for back/leg pain between the groups at 1 week after the operation, but the scores of the ES group were significantly higher than those of the MS group at 3 months and 12 months. There were no significant differences of mean JOA and ODI between the ES and MS groups preoperatively, at 3 months, or at 12 months, but the JOA and ODI scores of the ES group were significantly higher than those of the MS group 1 week after the operation. LIMITATIONS: The study showed that a novel method for the minimally invasive treatment of ADS is feasible; the safety and outcomes of this method should be verified with more cases. CONCLUSIONS: Minimally invasive decompression with a 10-mm endoscope was suggested to be a safe and effective method, as expected, for the treatment of lumbar stenosis in ADS patients. KEY WORDS: Adult degenerative scoliosis, endoscope, lumbar stability, microscopic decompression, minimally invasive

The role of sagittal pelvic morphology in the development of adult degenerative scoliosis

Purpose Pelvic morphology dictates the alignment and biomechanics of the spine. Recent observations in different types of adolescent idiopathic scoliosis indicate that individual pelvic morphology is related to the spinal levels in which scoliosis develops: primary lumbar adolescent scoliosis is associated with a higher pelvic incidence (PI) than thoracic scoliosis and non-scoliotic controls. We hypothesize that adult degenerative scoliosis (ADS) of the lumbar spine follows the same mechanical principles and is associated with a high PI. Methods This study used an existing CT-scan database, 101 ADS patients were sex and age matched to 101 controls. The PI was measured by two observers with multi-planar reconstruction, perpendicular to the hip-axis according to a previously validated technique. Results The PI was 54.1° ± 10.8° in ADS patients and 47.7° ± 10.8° in non-scoliotic controls (p < 0.001). The median ADS curve apex was the disc L2-3 and median curve length was 4 vertebral levels. The mean supine Cobb angle was 21° ± 8° (ranged 10°–47°). There was no significant correlation between PI and the apex level (p = 0.883), the curve length (p = 0.418) or the Cobb angle (p = 0.518). Conclusions ADS normally develops de novo in the lumbar spine of patients with a higher PI than controls, similar to primary lumbar adolescent idiopathic scoliosis. This suggests a shared mechanical basis of both deformities. Pelvic morphology dictates spinal sagittal alignment, which determines the segments of the spine that are prone to develop scoliosis.

Risk factors for screw loosening in patients with adult degenerative scoliosis: the importance of paraspinal muscle degeneration

Background Paraspinal muscle is an important component to maintain spinal stability. But the relationship between the degeneration of paraspinal muscle and postoperative screw loosening in patients with adult degenerative scoliosis has not been studied. The objective of this study was to investigate risk factors for screw loosening in patients with adult degenerative scoliosis, including paraspinal muscle degeneration. Methods We investigated 93 patients with adult degenerative scoliosis who underwent spinal interbody fusion and pedicle screw fixation surgery. The lateral curvature was located in the lumbar spine and the follow-up time was ≥ 2 years. The patients were divided into loosening and non-loosening groups. Screw loosening was defined as a 1-mm or wider circumferential radiolucent line around the pedicle screw. We checked the cross-sectional area of paraspinal muscles, spinopelvic parameters, bone mineral density, number of fusion segment, and other factors. The potential risk factors for screw loosening were investigated by using binary logistical regression analysis. Results Fifty-seven patients showed screw loosening, which is 63.4% of total. Compared with patients in the non-loosening group, the cross-sectional area of erector spinae and psoas major muscle at L5 level were significantly smaller in patients with screw loosening (P < 0.05). Among these factors, the number of fused segments and relative erector spinae total cross-sectional area were independent risk factors for screw loosening. Conclusions The degeneration of paraspinal muscle and the increase of fusion segment were independent factors for screw loosening in patients with adult degenerative scoliosis.