Aim: When a leg-length discrepancy (LLD) is severe enough, it can result in lumbar scoliosis and other postural defects. To our knowledge, no study has demonstrated associations between LLD and lumbar curvature using full-length standing radiographs of the lower limbs and lumbar spine. This study aimed to examine the correlations between LLD and lateral curvature of the lumbar spine using standing radiographs.
Materials and methods: Full-length standing radiographs of the lower limbs and spinal column of 113 participants (age range: 10–65 years) obtained between November 2006 and September 2019 were reviewed. Leg length was measured as the linear distance from the centre of the femoral head to the centre of the tibial plafond and converted to millimetres using a radiographic ruler captured in the images. Leg-length discrepancy was analysed as the absolute difference (mm) between the left and right leg lengths. Inequality was also evaluated as leg-length discrepancy ratio (LLDR), calculated as leg-length discrepancy/length of the unaffected (longer) leg × 100 (%). Lateral lumbar curvature was evaluated with the Cobb angle (°). The association between LLD or LLDR and lumbar Cobb angle was analysed by correlation analysis. Statistical analysis was performed by simple regression in SPSS.
Results: Both LLD and LLDR exhibited a robust and positive correlation with lumbar Cobb angle (γ = 0.53, γ = 0.62), as illustrated by the following regression equations: lumbar Cobb angle (°) = 0.316 × leg-length discrepancy (mm) + 2.83 and lumbar Cobb angle (°) = 2.19 × leg-length discrepancy ratio (%) + 3.0.
Conclusion: Using objective imaging data, we found that the lumbar Cobb angle tends to be >10° if the difference in leg lengths is >20 mm.
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