Dislocation Height Performs Well in Predicting the Use of Subtrochanteric Osteotomy in Crowe Type IV Hips

The purpose of this study was to determine whether dislocation height can predict the use of subtrochanteric osteotomy in patients with Crowe type IV hip dysplasia.

We retrospectively included 102 patients affected by unilateral Crowe type IV developmental dysplasia who underwent primary total hip arthroplasty with modular cementless stem from April 2008 to May 2019 in our institution. Based on radiographs and operative notes, we found 62 hip arthroplasties were performed with subtrochanteric osteotomy and 40 without subtrochanteric osteotomy, which were named as the (subtrochanteric osteotomy) STO group and non-STO group, respectively. The predictive values of height of greater trochanter, height of femoral head/neck junction, and distalization of greater trochanter were analyzed using receiver operating characteristic (ROC) curves.

The ROC curves showed that distalization of greater ntrochanter had the highest areas under the ROC curve (AUC), at 0.998. This was followed by height of greater trochanter and height of head/neck junction, which had AUCs of 0.937 and 0.935, respectively. The optimal thresholds of these three indicators were 4.84 cm, 6.05 cm, and 4.26 cm. At the last follow-up, six dislocations occurred (five in the STO group and one in the non-STO group). Four hips were treated by closed reduction and two by open reduction. Three patients (all in STO group) developed femoral nerve palsy with skin numbness on the frontal thigh or tibia and all recovered in a year. At outpatient visit, the limb length was measured. LLD was <1 cm in 83/102, 1-2 cm in 18/102, and >2 cm in 1/102.

This study reveals that indicators of dislocation height are useful in predicting the use of subtrochanteric osteotomy during total hip arthroplasty for Crowe type IV hip dysplasia. However, a comprehensive, multivariate analysis may be required to validate these results.