Broken rods in spinal deformity surgery: an analysis of clinical experience and a literature review

Backgrоund. Rod fractures are one of the specific complications of spinal deformity surgery. The number of publications on this topic is small, and the conclusions are often contradictory. Aim. The aim of this study is to analyze the current situation concerning the problem of fractures of the rods in spinal deformities of various etiologies in terms of frequency and risk factors for this complication. Materials and methods. The study included 3,833 patients who underwent operations between 1996 and 2018. The inclusion criteria of being over 10 years of age with no history of spinal surgery were applied. Results. Fractures of metal implant rods were detected in 85 patients out of a total of 3,833 (2.2%). There was a significant difference between the groups of idiopathic and congenital scoliosis patients. A rod fracture in 62 of the 85 patients was the reason for reintervention to restore integrity with a connector or a full replacement. An increase in BMI by one raised the chance of a fracture by 1.07 times (p = 0.019). Increasing the age by one year increased the possibility of a fracture by 1.03 times (p = 0.039). A statistically significant association of the ventral stage of surgical treatment (discectomy and interbody fusion with autologous bone) where no fracture was detected (p = 0.403) was revealed. Being over 15 years old a statistically significant predictor was in the group under 20 years of age (p = 0.048). For BMI, there was no statistically significant threshold for fracture probability in the group under 20 years of age. It was confirmed that a hybrid fixation system produced a significantly lower percentage of complications than a hook system. A systematic literature review of sources on this topic included international databases (Scopus, Medline, and Google Scholar) as well as investigating the publications contained in the reference list. Conclusions. Rod fractures during surgery for spinal deformities of various etiologies are one of the typical complications. Fracture frequency in large study groups is small. The risk of developing this complication rises with both increasing BMI and patient age, although there is no statistically significant threshold for BMI relative to the chances of fracture in the group up to 20 years of age. Modern reticular systems of attachment of the endocorrector to the vertebral structures can dramatically reduce the risk of rod fracture during the postoperative period.