Avascular necrosis in children with cerebral palsy after reconstructive hip surgery

Abstract

Purpose Progressive hip displacement is one of the most com­mon orthopaedic pathologies in children with cerebral palsy (CP). Reconstructive hip surgery has become the standard treat­ment of care. Reported avascular necrosis (AVN) rates for hip reconstructive surgery in these patients vary widely in the liter­ature. The purpose of this study is to identify the frequency and associated risk factors of AVN for reconstructive hip procedures. Methods A retrospective analysis was performed of 70 cases of reconstructive hip surgery in 47 children with CP, between 2009 and 2013. All 70 cases involved varus derotation oste­otomy (VDRO), with 60% having combined VDRO and pelvic osteotomies (PO), and 21% requiring open reductions. Mean age at time of surgery was 8.82 years and 90% of patients were Gross Motor Function Classification System (GMFCS) 4 and 5. Radiographic dysplasia parameters were analysed at selected intervals, to a minimum of one year post-operatively. Severity of AVN was classified by Kruczynski’s method. Bivar­iate statistical analysis was conducted using Chi-square test and Student’s t-test. Results There were 19 (27%) noted cases of AVN, all radio­graphically identifiable within the first post-operative year. The majority of AVN cases (63%) were mild to moderate in se­verity. Pre-operative migration percentage (MP) (p = 0.0009) and post-operative change in MP (p = 0.002) were the most significant predictors of AVN. Other risk factors were: GMFCS level (p = 0.031), post-operative change in NSA (p = 0.02) and concomitant adductor tenotomy (0.028). Conclusion AVN was observed in 27% of patients. Severity of displacement correlates directly with AVN risk and we sug­gest that hip reconstruction, specifically VDRO, be performed early in the ‘hip at risk’ group to avoid this complication.