Early-Stage Femoral Head Hypoperfusion Correlates with Femoral Head Deformity at Intermediate Follow-up in Legg-Calvé-Perthes Disease.

Background: Perfusion MRI (pMRI) can quantify femoral head hypoperfusion in early-stage Legg-Calvé-Perthes disease. We investigated whether the severity of hypoperfusion measured at the early stage correlates with femoral head deformity at intermediate-term follow-up.

Methods: Sixty-three patients who were 5 to 11 years of age at the diagnosis of Legg-Calvé-Perthes disease and who had pMRI performed at an early stage (Waldenström Stage 1 to 2a) were retrospectively reviewed. Twenty-eight patients were treated nonoperatively and 35 were treated with proximal femoral varus osteotomy (PFVO). The sphericity deviation score (SDS) was used as the primary outcome. Femoral head perfusion and SDS were measured by 2 observers. Models assessing the relationship between hypoperfusion and SDS were fitted without and with stratifications by age at diagnosis and treatment method.

Results: All 63 patients had a minimum of 4 years of follow-up (mean follow-up, 7.5 ± 2.6 years). All had reached the healed stage (Stage 4), and their mean age was 15.6 ± 2.8 years. The SDS outcome showed a significant positive correlation with the hypoperfusion % (p < 0.001). In the <50% hypoperfusion range, the SDS indicated no-to-low deformity, with narrow variability of outcome. However, the SDS became exponentially worse and had a wider variability of outcome at the ≥50% hypoperfusion range. Multivariable analyses revealed age at diagnosis, hypoperfusion %, and treatment method as significant prognostic factors for SDS (p = 0.007, <0.001, and 0.042, respectively). When treatment outcomes were stratified by age at diagnosis and hypoperfusion %, PFVO showed significantly better SDS outcome than nonoperative treatment in patients with an age at diagnosis of ≥8 years and low (<50%) and intermediate (50% to 80%) hypoperfusion ranges (p = 0.036 and 0.021, respectively).

Conclusions: Our study found a significant relationship between femoral head hypoperfusion measured in early-stage Legg-Calvé-Perthes disease and femoral head deformity at intermediate-term follow-up. This study provides new insight into the relationship between early-stage femoral head hypoperfusion and deformity.

Level of evidence: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.