Spino-Pelvic Thresholds For Prevention Of Proximal Junctional Kyphosis Following Combined Anterior Column Realignment and Short Posterior Spinal Fusion In Degenerative Lumbar Kyphosis

Objective: To analyze ideal indication for combined anterior column realignment (ACR) with short posterior spinal fusion (PSF) and posterior column osteotomy (PCO) for preventing proximal junctional kyphosis (PJK) in adult spinal deformity (ASD) patients with lower lumbar kyphosis and compensatory thoracolumbar lordosis.

Methods: A retrospective study was conducted. This study included 27 ASD patients (average age of 66.6 years; one male and 26 females) with lower lumbar kyphosis and compensated thoracolumbar lordosis who underwent short PSF with PCO following ACR from 2006 to 2010. The minimum follow-up period was 5 years. The patients were divided into two groups based on the sagittal vertical axis (SVA) of the last follow-up radiographs, and a comparative analysis was performed evaluating spino-pelvic parameters and clinical outcomes including the Oswestry Disability Index (ODI), Visual Analog Scale (VAS), and complications.

Results: The mean follow-up time of included patients was 109.7 months, and the mean number of fused segments was 3.7. The uppermost instrumented vertebra was L in 18 patients or L in nine patients, and lowermost instrumented vertebra was sacrum in all patients. The mean lumbar lordosis (LL) values in the optimal SVA and suboptimal SVA groups were 4.4° and 4.2° preoperatively (P = 0.639), -48.1° and -35° postoperatively (P = 0.007), and -45.2° and -20.7° at the last follow-up (P < 0.05). Overcorrection was seen in seven patients in the optimal SVA group, whereas all of the patients of the suboptimal SVA group were in the category of undercorrection (P = 0.021). Pelvic incidence (PI) of optimal SVA group (<50 mm, n = 16) and suboptimal SVA group (≥50 mm, n = 11) was 44.1° and 53.8° (P = 0.009). The prevalence of PJK was significantly higher in the suboptimal SVA group (P = 0.008), and last follow-up VAS for back pain (P < 0.05), and postoperative and last follow-up ODI (P = 0.002 and P < 0.05) were statistically larger for the suboptimal group than the optimal group.

Conclusions: Combined ACR with short PSF and PCO could effectively prevent sagittal decompensation of PJK and help achieve sagittal balance in the treatment of ASD patients with lower lumbar kyphosis, compensatory thoracolumbar lordosis, and especially low PI (<50°).