Abstract
Introduction
Limb length discrepancy (LLD) is one of the major reasons of dissatisfaction after total hip arthroplasty(THR) and limb equalization after THR in unilateral developmental dysplasia of the hip (DDH) is very important. study designed to measure the difference of adult femoral length between normal and dislocated hip in unilateral DDH.
Method
Sixty patients with unilateral high riding DDH (crow type 3,4) who were underwent THR included. All the cases had digital lower limb scanograms. Exclusion criteria was any previous hip or femur surgery, any rheumatoid disease, history of any disease that affect the growth. All the scanograms measured by one fellowship of adult reconstruction and one radiologist specialized in musculoskeletal imaging. Each one repeated the measurements two months later blindly and inter observer and intra observer reliability checked. Each one measured femoral length in both sides from greater trochanter(GT), to the distal surface of the femoral condyles.
Results
59 female and one males included. Average age was 27.5 years (19–50 years). Inter observer reliability index were excellent (ICC 98%). Only 6 cases (10%) had exactly equal femoral length, 31(52%) cases were longer on the dislocated side and 23 (38%) cases were shorter. Average overgrowth was 6.1 mm (Range: 1–22) and average undergrowth was 10.7 (Range 1–21). 35 cases (58.3%) cases had 5 mm or more differences and 30% had 5–10 mm .17 cases (28.3%) had at least 10 mm difference that 8 cases (13%) had shorter and 9 cases (15%) had longer femur on dislocated side. Maximum difference was 22 mm over length on dislocated side.
Conclusions
More than half of patients with unilateral high riding DDH have longer femur on the dislocated side and 15% of them are longer than 10 mm. we recommend to get the scanograms in all the unilateral DDH cases to avoid post-operative limb discrepancy and detecting the amount of shortening in cases that need femoral shortening.
