Treatment of ankylosing spondylitis complicated with a thoracolumbar Andersson lesion by posterior closed osteotomy, debridement and fusion through the fracture line

BACKGROUND: An Andersson lesion (AL) is a fatigue fracture occurring across three columns in ankylosing spondylitis (AS), resulting in spinal pseudarthrosis (SP) formation, most commonly in the thoracolumbar segment. However, there is still great controversy and few reports on the best surgical method for the treatment of AS combined with thoracolumbar AL. The purpose of this study was to investigate the efficacy of posterior closed osteotomy, debridement and fusion through the fracture line for the treatment of this disease. METHODS: The clinical data of 13 patients (male 8, female 5, mean age 50.6 years) with AS combined with thoracolumbar AL treated with posterior closed osteotomy, debridement and fusion through the fracture line were retrospectively analysed. The following parameters of the full-length lateral spine radiographs were measured preoperatively and at the last follow-up: cervical 7 tilt (C(7)T), global kyphosis (GK), thoracic kyphosis (TK), thoracolumbar kyphosis (TLK), local kyphosis (LK), angle of the fusion levels (AFL), lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS) and sagittal vertical axis (SVA). The visual analog scale (VAS), Oswestry disability index (ODI) and Scoliosis Research Society-22 (SRS-22) scores were recorded preoperatively and at the last follow-up. RESULTS: The mean operation time was 345 min, the mean blood loss was 673 mL, and the mean follow-up time was 21.9 months. Compared with the preoperative values, the C(7)T, GK, TK, TLK, LK, AFL, PT, SS and SVA values of all patients were significantly improved at the last follow-up (P < 0.05); GK improved from 81.62 ± 16.11 to 50.15 ± 8.55, with an average of 31° of correction (F = 75.945, P<0.001). The VAS, ODI and SRS-22 scores also significantly improved (P < 0.05). At the last follow-up, bone fusion was found in all fracture ends. One patient developed numbness in the lower limbs after surgery and recovered after 3 months of rehabilitation; none of the remaining patients experienced postoperative complications. CONCLUSIONS: Posterior closed osteotomy, debridement and fusion through the fracture line completely removes the necrotic tissue around the SP, relieves symptoms, and corrects kyphosis simultaneously. It reduces the tension behind the fracture line or changes the tension into compressive stress, enabling stable repair of the fracture and avoiding anterior surgery. It is a safe and effective operation. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12891-022-05770-3.