Is VDRO Alone Appropriate Treatment for Hip Dysplasia in Cerebral Palsy?
A new study shows that patient age and level of gross motor function are important factors in the effectiveness of varus derotational shortening osteotomy alone or with concomitant acetabular osteotomy.
Olga Solovyova, MD
Chang FM, Ma J, Pan Z, Ingram JD, Novais EN.
Acetabular remodeling after a varus derotational osteotomy in children with cerebral palsy. J Pediatr Orthop. 2016 Mar;36(2):198-204.
Chang et al investigated acetabular remodeling after isolated proximal femoral varus derotational shortening osteotomy (VDRO) and factors predictive of remodeling in children with cerebral palsy (CP), as well as acetabular development in children without CP.
This retrospective study included a cohort of 100 consecutive patients who underwent VDRO without a pelvic osteotomy procedure. Indications for surgery were a migration index (MI) >30% or a rapid increase in MI. Most patients had a concurrent iliopsoas release and were placed in a spica cast for 3 to 6 weeks.
Acetabular remodeling was evaluated using the acetabular depth ratio (ADR). Patients who had follow-up of more than 1 year (mean 5.1 years) were included in the analysis, for a total of 87 patients (174 hips). A control group of 917 patients (1834 hips) with normal AP pelvis radiographs was created by the authors from their database. In the control group:
- ADR was shown to increase with patient age, and then level off at skeletal maturity.
- Children at Gross Motor Function Classification System (GMFCS) level II had a greater increase in ADR with age than those at GMFCS level III.
- Children at GMFCS level IV-V had a small decrease in ADR as they got older.
- Female patients had larger ADR values than male patients.
In the operative group:
- The mean postoperative increase in ADR was 3.4 ± 4.4.
- GMFCS level I-III correlated with greater improvement in ADR postoperatively than GMFCS level IV-V (5.1 ± 4 vs. 2.6 ± 4.4).
- Female gender and lower intraoperative neck shaft angle (NSA) also correlated with greater improvement in ADR after surgery.
- Older children were found to have a smaller increase in ADR postoperatively, although this trend was not statistically significant.
The efficacy of isolated VDRO has been debated for some time. There is conflicting evidence in the literature as to whether isolated VDRO is adequate or whether pelvic osteotomy is required in patients with hip dysplasia related to cerebral palsy.
The results of this study indicate that the change in position of the femoral head alone affects acetabular remodeling, further demonstrated by the fact that the NSA was negatively correlated with ADR.
This – in combination with the discrepancy in improvement seen between the GMFCS I-III and the GMFCS IV-V groups – suggests that the amount of abnormal tone influences the evolution of acetabular dysplasia preoperatively and remodeling postoperatively.
The limitations of this study include its retrospective nature and the absence of clinical outcomes. Additionally, excluding patients who had concomitant osteotomies likely created a cohort of CP patients with hip dysplasia that was less severe than in the general population of children with CP.
A comparison of the pre- and postoperative NSA would have been helpful to elucidate which better correlated with acetabular remodeling, the change in NSA or the absolute final value.
Finally, commentary on patients who required subsequent surgical procedures on the hip would have been valuable in assessing the long-term success of the procedure.
The results of this study indicate that VDRO without concomitant acetabular osteotomy is an effective treatment strategy, particularly in younger CP patients with GMFCS levels I-III who have higher remodeling potential.
In older patients with higher levels of spasticity, it may be beneficial to consider additional procedures. However, as children with GMFCS levels IV and V were found to have decreasing ADR with age, they are the patients who would most benefit from surgical intervention.
Olga Solovyova, MD is a resident at NYU Langone Medical Center – Hospital for Joint Diseases, New York, New York.