Can Posterior Intervertebral Release Enhance the Correction Efficiency of Severe and Rigid Adult Idiopathic Scoliosis? A Multicenter Study With a Minimum 2-year Follow-up

BACKGROUND: Although posterior intervertebral release (PIVR) has been reported for rigid scoliosis, its clinical efficacy and specific contribution to the management of severe and rigid adult idiopathic scoliosis remain unclear. QUESTIONS/PURPOSES: (1) Is the addition of convex PIVR to Scoliosis Research Society (SRS) Grade 2 osteotomy associated with improved radiographic correction of severe rigid adult idiopathic scoliosis, specifically in terms of the main coronal curve correction rate, apical vertebral rotation, and rib hump reduction? (2) Is the combined PIVR and SRS Grade 2 osteotomy procedure associated with superior patient-reported outcomes in the domains of self-image and mental health compared with SRS Grade 2 osteotomy alone? (3) Is the PIVR procedure associated with a higher risk of complications, particularly neurologic deficits? METHODS: Between 2018 and 2021, a total of 210 patients with severe rigid spinal deformity were assessed. After excluding 15 patients preoperatively, 195 with adult idiopathic scoliosis (major coronal curve > 80°, flexibility < 25%) underwent surgery. Based on a standardized intraoperative algorithm, 195 patients with severe rigid adult idiopathic scoliosis were allocated to treatment: all patients initially underwent SRS Grade 2 osteotomies; PIVR was added only if the senior surgeon deemed that persistent rigidity compromised adequate correction after posterior release. This algorithm allocated 48% (93 of 195) of patients to the PIVR-augmented group and 52% (102) to the SRS Grade 2 osteotomy alone group. After accounting for loss to follow-up (n = 19), the final analysis included 176 patients with complete 2-year data (PIVR, n = 84; SRS Grade 2 osteotomy, n = 92). The median (IQR) follow-up duration was 27 months (27 to 28) for the PIVR group and 28 months (27 to 28) for the SRS Grade 2 osteotomy alone group. The two groups were comparable at baseline, with no differences in demographic characteristics (age, sex), patient-reported outcomes (SRS-22r questionnaire and SF-36 scores), or radiographic parameters (including the magnitude of the major coronal curve, thoracic kyphosis, apical vertebral rotation, apical vertebral translation, and rib hump) (all p > 0.05). Radiographic parameters and health-related quality of life scores were compared between the groups to evaluate radiographic correction and clinical effectiveness. The minimum clinically important difference (MCID) thresholds were defined according to published values as follows: SRS-22r domains (function = 0.90, pain= 0.85, self-image= 1.05, mental health = 0.70) and SF-36 summary scores (physical component summary = 7.83, mental component summary [MCS] = 5.14). RESULTS: The addition of convex PIVR to SRS Grade 2 osteotomy was associated with a larger mean ± SD correction of the major coronal curve (70% ± 2% versus 56% ± 2% at 1 month and 67% ± 2% versus 53% ± 2% at final follow-up; p < 0.001), resulting in a smaller residual curve (26° ± 2° versus 38° ± 2° at 1 month and 29° ± 2° versus 41° ± 2° at final follow-up). The absolute mean difference in correction was 14% (95% confidence interval [CI] 13.5% to 14.5%; p < 0.001) at both time points. A larger change was also demonstrated for thoracic kyphosis (52% versus 42%; p < 0.001) and apical vertebral rotation (53% versus 38%; p < 0.001). Despite the additional maneuver, PIVR was not associated with increased operative time or estimated blood loss. Patients undergoing combined PIVR and the SRS Grade 2 osteotomy procedure reported larger improvements in SRS-22r self-image (median [IQR] change 1.2 [1.1 to 1.3] versus 0.9 [0.8 to 1.0]; p < 0.001), mental health (0.8 [0.7 to 0.9] versus 0.6 [0.5 to 0.7]; p < 0.001), and SF-36 MCS scores (6.9 [6.5 to 7.3] versus 5.3 [4.9 to 5.8]; p < 0.001). A higher proportion of patients in the PIVR group achieved the MCID for self-image (76% versus 48%, OR 3.0 [95% CI 1.6 to 5.8]; p < 0.001), mental health (67% versus 39%, OR 2.7 [95% CI 1.4 to 5.1]; p = 0.002), and SF-36 MCS (71% versus 43%, OR 2.5 [95% CI 1.3 to 4.7]; p = 0.005). With the numbers available, there was no difference between the groups in the percentage of patients experiencing neurologic deficits after surgery (2.4% [2 of 84] in the PIVR-augmented group versus 0% [0 of 92] in the SRS Grade 2 osteotomy alone group, OR 4.4 [95% CI 0.2 to 93.1]; p = 0.50). CONCLUSION: In this retrospective, comparative, multicenter study, adding PIVR on the convex side of the apical region to SRS Grade 2 osteotomy was associated with greater radiographic correction and improved clinical outcomes for severe and rigid adult idiopathic scoliosis. This was achieved without increasing operative time, blood loss, or complications, representing a surgical strategy with a high benefit-to-risk ratio. A randomized controlled trial would be the logical next step to conclusively establish the efficacy of this technique. LEVEL OF EVIDENCE: Level III, therapeutic study.