The association between the degeneration of the paraspinal muscles in patients with degenerative lumbar scoliosis and the postoperative proximal junctional kyphosis(PJK)

English Keywords:Degenerative lumbar scoliosis  Degeneration of the paraspinal muscles  Proximal junctional kyphosis

English Abstract:

  【Abstract】 Objectives: To investigate the relationship between the degeneration of preoperative lumbar paravertebral muscles and the incidence of proximal junctional kyphosis(PJK) in degenerative lumbar scoliosis(DLS) patients after posterior long instrumented spinal fusion. Methods: Fifty-two patients diagnosed with DLS were included. According to the occurrence of PJK at final follow-up, patients were divided into two groups: PJK group(10 cases) and non-PJK group(42 cases). Radiographic assessment included pelvic parameters, lumbar muscularity(the ratio between the cross-sectional area of the muscle and the intervertebral disk/vertebral body) and the muscle-fat index(the ratio between the mean signal intensity of the muscle and that of the subcutaneous fat within regions of interest. Logistic regression analysis was used to explore the risk factors of PJK. Preoperative and follow-up health related quality of life scores were compared between PJK group and non-PJK group. Results: The prevalence of PJK was 19.23%. Age at surgery, gender, BMI, duration of disease, diabetes mellitus, osteotomy, fused levels, fixation levels, decompression levels, UIV level, LIV level and T-score were not significantly different between PJK and non-PJK group. Preoperative lower bone mineral density(BMD), preoperative smaller SS, larger preoperative TLK angle, larger TK correction and changes of proximal junctional angle(PJA) during operation, UIV at T12-L1, larger PJA immediately after surgery, and lower lumbar muscularity and higher fatty degeneration might lead to PJK after long instrumented spinal fusion for degenerative lumbar scoliosis. Patients with PJK had worse back pain VAS score and SRS-22 activity score. When included in a multivariate logistic regression model, preoperative SS＜25°(OR=12.902, P=0.046), immediate postoperative PJA increase ≥3.6°(OR=21.940, P=0.015) and lean muscle-fat index of paraspinal extensor muscle >27.65(OR=11.749, P=0.019) were independent risk factors for PJK. Conclusions: DLS patients with PJK have lower lumbar muscularity and higher fatty degeneration before surgery than patients without PJK. Preoperative SS＜25°, immediate postoperative PJA increase ≥3.6° and lean muscle-fat index of paraspinal extensor muscle >27.65 are independent risk factors for PJK.