Femoral Head Deformity Associated With Hip Displacement in Nonambulatory Cerebral Palsy: Results at Skeletal Maturity

Abstract

Background: Maintaining femoral head shape (FHS) and acetabular sphericity are important goals in preventing long-term osteoarthritis in hips in children with cerebral palsy (CP). As acetabular morphology has been widely studied, our objective was to determine FHS in CP after triradiate cartilage (TRC) closure, a proxy for skeletal maturity, and the risk factors associated with residual deformity and osteoarthritis. Methods: In this retrospective cohort study, patients with CP [Gross Motor Function Classification System (GMFCS) IV to V], minimum 4 yearly hip radiographs after age 10 years, and at least 1 radiograph after age 16 years, were included. Primary outcome was FHS (Rutz), stratified as “less severe” (Rutz A to B) and “more severe” (Rutz C to D). Secondary outcomes included migration percentage (MP), age at TRC closure, previous reconstructive (femoral with/without pelvic osteotomies) surgery, previous intrathecal baclofen, Tönnis osteoarthritis grade, and GMFCS level. Statistical analyses included χ2 analysis and multiple logistic regression. Results: One hundred sixty-three patients (326 hips) met the inclusion criteria, with TRC closure at age 14.0 (SD: 1.8) years. At final follow-up of 4.4 (SD: 2.4) years after TRC closure, 17% (55 hips), had a “more severe” FHS. From TRC closure to final follow-up, the frequencies of “less severe” hips decreased (−10%, P<0.001), while “more severe” increased (+115%, P<0.001). In multiple regression analysis, MP at TRC closure was the only significant risk factor associated with a “more severe” FHS at final follow-up (P=0.03). Receiver operating characteristic curve analysis determined MP≥30.5% to be associated with a “more severe” FHS at final follow-up (P<0.009). The FHS was not affected by reconstructive surgery, sex, GMFCS level, or intrathecal baclofen use. “Less severe” hips had lower Tönnis grades (0 to 1) compared with “more severe” hips (Tönnis grades 2 to 3) at final follow-up (P<0.001). Conclusions: FHS at skeletal maturity was not influenced by prior reconstructive surgery but was negatively affected when MP≥30.5% at the time of TRC closure. The extent of residual femoral head deformity correlated with the severity of osteoarthritis at final follow-up. Level of Evidence: Level III.

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

“…A recent study of non-ambulant children with CP investigated the status of femoral head deformity at skeletal maturity, finding an MP > 30% at triradiate cartilage closure was associated with a ‘more severe’ outcome at final follow-up [ 76 ]. This more severe head shape was also associated with a higher risk of worse osteoarthritis by Tönnis grading.…”

“…Interestingly, the authors found that prior reconstructive surgery had no impact on head shape at skeletal maturity which they felt was likely due to a lack of complete containment of the femoral epiphysis. Additional work is required to precisely define the degree of femoral head deformity which is amendable to reconstructive surgery versus the degree of deformity which would be better managed by a salvage surgical option [ 45 , 76 ].…”

What’s New in Pediatric Orthopaedics

“…These patients merit continued surveillance after closure of the triradiate cartilage. In a similar study, the shape of the femoral head at skeletal maturity was found to be negatively affected when the migration percentage was ‡30.5% at the time of triradiate cartilage closure 25 . This was associated with worse osteoarthritis radiographically, although pain scores were not collected in this study.…”

Reliability of assessing proximal femur geometry with Rutz classification schema in patients with cerebral palsy

“…Although we have included information on the possible use of the classification in skeletally immature patients, the obtained results do not fully meet the expectations. Ulusaloglu et al [21] showed an increase in the number of type C and D femoral head shapes in older children with CP close to skeletal maturity. Observed changes can even progress after skeletal maturity.…”