Radiological Evaluation of Distal Trochanteric Transfer in Patients with Proximal Femoral Growth Disturbance

Objectives: Proximal femoral growth disturbance (PFGD), resulting from conditions such as Legg–Calvé–Perthes disease and developmental dysplasia of the hip, causes femoral head deformity and trochanteric overgrowth. This study evaluates the effectiveness of distal trochanteric transfer (DTT) in anatomical restoration using objective radiological parameters.
Methods: Patients with unilateral PFGD who presented with pain, abductor muscle weakness, and Trendelenburg gait and subsequently underwent DTT were retrospectively included in this study. All patients had skeletal growth potential, confirmed by the presence of open growth plates. Patients who had standard anteroposterior pelvic radiographs and anteroposterior and lateral hip radiographs were included, as these imaging modalities were required to evaluate the articular trochanteric distance (ATD), central trochanteric distance (CTD), trochanteric offset (TO), and lever arm ratio (LAR).
Results: The study cohort consisted of 13 patients (11 females, 2 males). The mean age at surgery was 10.54±2.11 years, and the mean follow-up period was 7.62±5.25 years. The intraclass correlation coefficient (ICC) was significant for 9 of the 12 total measurements, with three parameters demonstrating statistically non-significant values. Preoperatively, the pathological hips showed a significantly reduced mean ATD of −2.00±8.57 mm compared with the normal hips (17.38±5.58 mm; p=0.001). Postoperative ATD significantly improved to 15.62±6.36 mm (p=0.001). Similarly, the significantly reduced preoperative TO (18.69±6.84 mm) was restored to 24.85±7.03 mm postoperatively (p=0.008). Furthermore, the postoperative LAR (2.83±0.48) was significantly higher than both the preoperative value (2.21±0.46; p=0.012) and the normal hip value (p=0.001). No significant difference was observed for CTD.
Conclusion: DTT effectively achieves trochanteric distalization and lateralization, leading to restoration of the abductor muscle mechanism. Our analysis confirms that both ATD and TO are reliable radiographic parameters, as demonstrated by their strong ICC values, for evaluating immediate anatomical results. However, CTD is age-dependent, and both CTD and LAR are inherently influenced by the underlying femoral head anatomy. Future studies are needed to correlate these anatomical improvements with long-term clinical outcomes.

Keywords: Articular trochanteric distance, distal trochanteric transfer, greater trochanter, intraclass correlation coefficient, proximal femoral growth disturbance