Risk factors for rod fracture after correction and internal fixation for adult spinal deformity and treatment strategy

English Keywords:Adult spinal deformity  Corrective surgery  Internal fixation  Pseudoarthrosis

English Abstract:

  【Abstract】 Objectives: To investigate the incidence, relative risk factors and treatment strategies of rod breakage after correction and internal fixation of adult spinal deformity(ASD). Methods: The clinical data of ASD patients treated with posterior corrective operation and internal fixation in the Department of Orthopedics of Xinqiao Hospital between January 2015 and December 2019 were analyzed retrospectively. A total of 79 patients aged 45-75 years(62.1±7.7 years) were included. The follow-up period was 24-59 months(30.6±9.2 months). According to whether the rod was broken during the follow-up period, the patients were divided into rod fracture group(RF group) and rod non-fracture group(NRF group). The sex, age, body mass index(BMI), bone mineral density(BMD) T value, complications and follow-up time of the two groups were recorded. The sagittal vertical axis(SVA), pelvic incidence(PI), pelvic tilt(PT), sacral slope(SS), thoracic kyphosis(TK), lumbar lordosis(LL), LL-TK value, PI-LL value, and coronal Cobb angle were measured before and after operation. The operation-related information of the two groups was collected, including operative time, intraoperative blood loss, the number of fixed fusion segments, whether three-column osteotomy, whether the lower fixed vertebrae involved the sacrum or pelvis, and whether there was interbody fusion. The position, time and revision operation of the broken rod in the RF group were recorded. The data of the two groups were compared and analyzed by Spearman test, and the positive parameters were further analyzed by multivariate logistic regression to find potential risk factors for rod fractures. Odds ratio(OR) and 95% confidence interval(CI) were calculated. Results: Among the 79 patients, rod fracture occurred in 14 patients(17.7%), with bilateral fracture in 11 cases and unilateral fractures in 3 cases. The time of rod fracture occurred at 6-31 months after operation(averaged 16 months), which occurred at the early stage after operation(within 24 months) in 10 patients(71.4%) and at 24 months after operation in 4 patients(28.6%). The rod fracture occurred at the osteotomy site in 11 cases and at T10-12 level in 3 cases. Spearman test showed that younger age(P=0.038), more levels of fusion(P<0.001), 3-column osteotomy(P<0.001) and bigger preoperative SVA(P＜0.001) were correlated with rod breakage. Multivariate logistic regression analysis showed that more levels of fusion (P=0.037, OR=2.043, 95%CI=1.046-3.992), 3-column osteotomy(P=0.044, OR=0.113, 95%CI=0.014-0.941), and bigger preoperative SVA(P=0.006, OR=1.119, 95%CI=1.032-1.212) were the risk factors of rod breakage after corrective surgery for ASD patients. 11 patients(78.6%) underwent revision surgery because of intractable low back pain or progression of spinal deformities, and were replaced the broken rods through posterior primary incision approach, combined with satellite rod technique; And meanwhile, out of which, 5 patients underwent one-stage retroperitoneal approach for anterior iliac bone graft fusion and received satisfactory results during follow-up. Conclusions: The incidence of rod breakage after correction and internal fixation in ASD patients is high. More levels of fusion, 3-column osteotomy, and greater preoperative SVA were significantly associated with rod fracture. The "Multi-rod technique" and anterior bone graft fusion technique can be used in the revision operation of rod fracture.