Association between Lumbar Scoliosis and Leg Length Discrepancy in Unilateral Hip Osteoarthritis

Abstract

INTRODUCTION: The leg length discrepancy (LLD) on unilateral hip osteoarthritis patients (HOA) might cause the occurrence of compensatory lumbar scoliosis (LS) toward the shorter leg (HOA side). However, few papers have investigated the relationship between LS and LLD on HOA. The objective of this study was to analyze the correlation between LS and LLD on unilateral HOA. METHODS: The subjects consisted of 437 patients (40-82 years) treated by total hip arthroplasty due to unilateral HOA. We investigated the LLD and the Cobb angle (maximum or L1-L5) on the erect posture radiographs and assessed the frequency of LS (Cobb angle of more than 5 degrees) (LS rate) and that of the convexity of LS occurring on the HOA side (□rate). The patients were classified into four groups according to the degree of LLD: including the under 1cm group (199 patients), 1 cm group (143 patients, over 1 cm and under 2cm), 2 cm group (65 patients, over 2 cm and under 3 cm), over 3 cm group (30 patients). We used the stratum specific likelihood ratio (SSLR) to define the strata with an optimal discriminating power. RESULTS: The LS rate and □rate were 40%,26% in all cases. For each stratum, the LS rate was as follows; under 1cm group: 1cm group: 2 cm group: over 3 cm group =35%:40%:43%:70%. In contrast, the□rates were as follows; 20%:24%:32%:63%.The frequency of both in the over 3 cm group was significantly higher than that in other groups (P<0.01). SSLR was 0.8 (95%CI:0.65-1.0),0.98 (0.75-1.29), 1.12 (0.72-1.76), 3.46 (1.65-7.25) for LS rate, and 0.7□0.54-0.92□,0.91□0.66-1.24□, 1.34□0.84-2.14□,4.84□2.41- 9.71□for□rate. DISCUSSION: Based on the fact that a 3 cm LLD was found to be a significant factor influencing LS rate and □rate, compensating for LS might therefore help to successfully maintain the body balance in unilateral HOA.