Risk factors for proximal junctional kyphosis after SRS-Schwab grade 4 osteotomy in patients with spine kyphoscoliosis/kyphosis

English Keywords:Kyphoscoliosis/Kyphosis  SRS-Schwab grade 4 osteotomy  Proximal junctional kyphosis  Risk factors

English Abstract:

  【Abstract】 Objectives: To investigate the risk factors for proximal junctional kyphosis(PJK) in patients with kyphoscoliosis/kyphosis underwent SRS-Schwab grade 4 osteotomy. Methods: A retrospective review of 46 patients with spine kyphoscoliosis/kyphosis who underwent SRS-Schwab grade 4 osteotomy between May 2011 and December 2015 was performed, including 24 males and 22 females, with an average age of 23.1±19.7 years. Body mass index, fusion segment, upper instrumented vertebra(UIV) and implant density were recorded. The spine-pelvic parameters including thoracic kyphosis(TK), lumbar lordosis(LL), pelvic incidence(PI), segmental kyphosis(SK), main curve(MC), sagittal vertical axis(SVA) and proximal junctional angle(PJA) were measured pre- and post-operationally and at last follow up. Patients were divided into PJK group and non-PJK group. Comparison of clinical and radiographic data was conducted between the 2 groups by Student′s t-test and Chi-square test or Fisher′s exact test. Multivariate Logistic regression analysis was used to determine the risk factors of PJK. Results: The average follow-up period of 46 patients was 36.9±13.4 months, during which PJK occurred in 11 cases(23.8%). 8 patients developed PJK during the first six months after surgery and the most common type of PJK was type Ⅰ(8/11). There was no significant difference in gender, age, follow-up, body mass index, fusion segment, bone mineral density, implant density and UIV between two groups (all P>0.05). Compared with the non-PJK group, the PJK group showed higher rate of pre-operative TK>40° and SK improvement >30° (all P<0.05). No significant difference was detected between both groups in pre-operative PJA, LL, MC, PI, SVA, and TK, LL, MC, SK, PI, SVA changes after operation and at the last follow-up (all P>0.05). Logistic regression analysis showed that SK improvement >30° (OR=7.000, 95%CI=1.591-30.800, P=0.010) was independent risk factor associated with PJK. The average PJA increased from 7.5°±3.0° to 20.8°±4.1° at 3 months after surgery. At the final follow-up in PJK group, PJA averaged 22.0°±4.5° and no significant progression of PJA was observed. Conclusions: The incidence of PJK after SRS-Schwab grade 4 osteotomy in patients with spine kyphoscoliosis/kyphosis was 23.9%, which mainly occurred within 6 months, and over correction of kyphosis is one of the high risk factors.