Summary of - Does the Deformity Index Reliably Predict the Shape of the Femoral Head at Healing of Legg-Calvé-Perthes Disease?

Document Type

Article

Abstract

Background: The treatment goal for Legg-Calvé-Perthes disease (LCPD) is to maintain the spherical shape of the femoral head. The deformity index (DI) <0.3, measured two years after disease onset, serves as a surrogate measure predicting that the femoral head will be classified as Stulberg class I or II at skeletal maturity. No study has yet compared the predictive value of DI against a quantitative measure of the femoral head’s shape at disease healing. This study aims to assess the reproducibility of a new DI measurement method and determine if DI can predict the femoral head’s shape at disease healing.

Methods: DI was measured two years after disease onset, and the Sphericity Deviation Score (SDS) was measured at the healing of LCPD on radiographs of 43 children. The reproducibility of these measurements was tested. Each healed femoral head was classified as either spherical or aspherical based on subjective visual assessment. The DI values were then compared with the SDS values.

Results: The reproducibility of SDS measurements was excellent and superior to that of DI. The mean duration of the disease was 3.97±0.96 years. Only 17 out of 32 hips with DI values <0.3 at 2 years had spherical femoral heads at healing (SDS <10). Three hips with SDS values <10 had DI values >0.3. The positive and negative predictive values of a DI <0.3 in predicting a spherical femoral head (SDS <10) at disease healing were 53% and 73%, respectively.

Conclusion: Although DI can be measured reproducibly, its predictive value for accurately identifying hips likely to heal with spherical femoral heads (DI <0.3) is not sufficiently high to justify its use as an outcome measure.

Publication Date

2022

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