Hip Displacement After Triradiate Cartilage Closure in Nonambulatory Cerebral Palsy

Abstract

Background:Recommendations with regard to the need for continued hip surveillance after skeletal maturity are based on expert opinion rather than evidence. This study aimed to determine the prevalence of and risk factors associated with progressive hip displacement in cerebral palsy (CP) after triradiate cartilage (TRC) closure.Methods:Patients who had spastic nonambulatory CP (Gross Motor Function Classification System IV to V) and hypertonic (spastic or mixed-type) motor type and follow-up of at least 2 years after TRC closure were included. The primary outcome variable was the hip migration percentage (MP). The secondary outcome variables included patient age at the time of TRC closure, prior preventative or reconstructive surgery, a prior intrathecal baclofen pump, history of scoliosis, history of epilepsy, a prior gastrostomy tube, a previous tracheostomy, and gender. An unsuccessful hip outcome was defined as a hip with an MP of ≥40% and/or requiring a reconstructive surgical procedure after TRC closure.Results:In this study, 163 patients met the inclusion criteria, with a mean follow-up of 4.8 years (95% confidence interval [CI], 4.4 to 5.1 years) after TRC closure at a mean patient age of 14.0 years (95% CI, 13.7 to 14.3 years). Of these hips, 22.1% (36 of 163) had an unsuccessful hip outcome. In multivariate analysis, the first MP at TRC closure (hazard ratio [HR] per degree, 1.04; p < 0.001) and pelvic obliquity (HR per degree, 1.06; p = 0.003) were independent risk factors for an unsuccessful hip outcome, but gender was not found to be significant (HR for male gender, 1.7 [95% CI, 0.8 to 3.58; p = 0.16]; female gender was the reference). However, the mean survival time for progression to an unsuccessful hip outcome was longer for female patients at 9.2 years [95% CI, 8.1 to 10.2 years]) compared with 6.2 years (95% CI, 5.6 to 6.9 years) for male patients (p = 0.02). There was also a significant improvement in survivorship for prior reconstructive surgical procedures (p = 0.002). The survivorship in patients who underwent reconstructive surgery performed at a patient age of ≥6 years was significantly higher compared with those who underwent surgery performed at <6 years of age (p < 0.05). A first MP at TRC closure of ≥35% was associated with an unsuccessful hip outcome, as determined by receiver operating characteristic (ROC) curve analysis (p < 0.001; area under the ROC curve of 0.891, sensitivity of 81%, and specificity of 94%).Conclusions:The risk factors for the progression of hip displacement after TRC closure in patients with CP included a higher MP and increased pelvic obliquity; there was decreased survivorship for male patients and patients with no prior reconstructive surgery. Patients with these risk factors and/or an MP of ≥35% at TRC closure should have continued radiographic surveillance to detect late hip displacement.Level of Evidence:Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Hip Surveillance and Management of Hip Displacement in Children with Cerebral Palsy: Clinical and Ethical Dilemmas

“…It has been assumed that the risk of progressive HD is negligible after triradiate cartilage (TRC) closure—a proxy for the onset of skeletal maturity—and thus HS could safely be discontinued after that point [ 9 ]. A recent large study, however, has demonstrated that there is a risk of further hip displacement in children with CP after closure of the TRC especially for those with risk factors including male gender, pelvic obliquity, high MP and no prior surgery [ 40 ]. For those youth at risk, the authors suggested that HS be continued up until age 18 years, with at least an x-ray every 2 years [ 40 ].…”

“…A recent large study, however, has demonstrated that there is a risk of further hip displacement in children with CP after closure of the TRC especially for those with risk factors including male gender, pelvic obliquity, high MP and no prior surgery [ 40 ]. For those youth at risk, the authors suggested that HS be continued up until age 18 years, with at least an x-ray every 2 years [ 40 ].…”

“…However, the success of bony reconstructive surgery is inversely related to the age at surgery [ 28 , 30 , 32 ]. Younger children have more years of growth ahead of them during which re-displacement may occur [ 33 , 40 ]. This is logical when it is remembered that the factors which contribute to hip displacement—such as adductor spasticity, weakness of the hip abductors and limited weight-bearing—remain present and largely unchanged after orthopaedic surgery [ 1 , 3 , 17 ].…”

“…This is logical when it is remembered that the factors which contribute to hip displacement—such as adductor spasticity, weakness of the hip abductors and limited weight-bearing—remain present and largely unchanged after orthopaedic surgery [ 1 , 3 , 17 ]. The risk period for recurrence is mainly, but not exclusively, related to the interval between bony reconstructive surgery and skeletal maturity [ 40 ].…”

“…A recent systematic review investigating the role of guided growth in children with CP (178 hips) also reported significant reductions in MP (35% to 26%), HSA (162° to 149°) and AI (22° to 18°), but the mean age at surgery was quite high at 7.2 years. The studies also included many ambulant children who are known to be at low risk of progressive hip displacement, and the mean follow-up was too short for strong recommendations [ 40 , 50 ].…”