The risk factors of rod fracture after correction surgery with satellite rod in severe spinal deformity / 中华骨科杂志

ABSTRACT

Objective To investigate the incidence and risk factors for rod fracture after correction surgery with satellite rod in severe spinal deformity.Methods A retrospective analysis was made including 234 cases who underwent correction surgery using satellite rod technique for severe spinal deformity in our hospital from July 2012 to June 2017.At the last follow-up,a total of 6 patients were found to have rod fracture.All the patients had complete clinical and imaging data at the time of preoperation,postoperation,rod fracture occurring,post-revision and the last follow-up.The Cobb angle,the Global kyphosis (GK),the coronal balance (distance between C7 plumb line and center sacral vertical line,C7PL-CSVL) and the sagittal vertical axis (SVA) were measured respectively in the 6 patients with rod fracture during the follow-up process.The time,incidence and position of the broken rod were recorded,and the reasons of rod fracture were analyzed for each patient.Results The incidence of rod fracture was 2.6％ (6/234) in the current study.The 6 patients included 3 males and 3 females with an average age of 34.5±15.4 years at initial surgery.The mean time of rod fracture was 24.0±17.7 months,of which 3 cases (50％) occurred within 1 years after operation.A total of 7 rods were broken,including 4 (57％) rods located at the single-rod-fixed side with stress concentration and 3 (50％) rods at the adjacent segment of the satellite rod.The average loss of correction was 20.8°±29.4° for Cobb angle and 34.0°±21.4° for GK.The potential reasons for rod fracture were listed as follows3 cases for residual kyphosis;2 cases for pseudarthrosis;3 cases for long fusion construct crossing lumbosacral junction;1 case for trauma.Of the 6 patients with rod fracture,3 (43％) patients underwent revision surgery by replacing the broken rods,adding satellite rod at the opposite side of pre-existing satellite rod and bone graft at the rod-breakage area.The other 3 patients underwent observation and no deterioration was found during follow-up.Conclusion The incidence of rod fracture after correction for severe spinal deformity with satellite rod is 2.6％.The broken rods are mainly located at the single-rod-fixed side with stress concentration or the adjacent segment of the satellite rod.Residual kyphosis,pseudarthrosis,long fusion construct crossing lumbosacral junction and trauma are the significant risk factors of rod fracture.