A Novel Classification Method for Developmental Dysplasia of the Hip Based on the Greater Trochanter of the Femur.

Abstract

The change of designation from congenital dysplasia of the hip to developmental dysplasia of the hip (DDH) indicates that the disease spectrum of hip dysplasia has changed. However, the wide-used Crowe classification existed before the DDH definition was proposed. Thus, the Crowe classification does not effectively identify DDH patients who have concurrent femoral neck deformities, resulting in these cases being overlooked. A total of 473 DDH patients (574 hips) who had undergone total hip arthroplasty from January 2016 to September 2023 were recruited into this study. The follow-up time was a mean 30.4 ± 22.0 months. Antero-posterior X-rays of the pelvis were obtained preoperatively, postoperatively, and during follow-up. Data on demographic information, preoperative functional scores, intraoperative information, postoperative functional scores, hospitalization costs, and postoperative complications were collected. Then stratified analysis according to the two classifications separately was performed to evaluate the reliability, repeatability, and popularization cost of the new system. In Crowe I and II DDH patients, those who had concomitant femoral neck shortening deformities represented 16.4%, but their intraoperative complications and postoperative functions were significantly worse than traditional Crowe I and II DDH patients. The new classification system based on the dislocation height of the greater trochanter of the femur could accurately identify various types of femoral neck shortening deformities. The subtypes of new classification correlate well with surgical difficulty and clinical outcomes, thereby guiding prosthesis selection and surgical anticipation. Compared to the Crowe classification, the new classification is easier to calculate, exhibits good repeatability, and has a lower learning curve. The greater trochanter classification system based on the anatomy and biomechanic could distinguish various types of DDH and aid in making surgical strategies. Furthermore, this new classification is stable and easy to learn compared to the Crowe classification.