Assessing leg length discrepancy after femoral fracture: clinical examination or computed tomography?

INTRODUCTION: Femoral shaft fractures treated with intramedullary nailing often heal with a leg length discrepancy (LLD). LLD is commonly evaluated by clinical examination and computed tomography (CT) scanogram. We assessed the correlation between these two techniques of calculating LLD.
METHODS: We reviewed 35 skeletally mature patients who sustained a femoral shaft fracture between January 1997 and December 1999. Leg length was measured clinically with direct measurement and a block test. Each patient was asked whether they felt they walked with a limp and whether they felt they had a leg length discrepancy. Each patient underwent a CT scanogram to measure femoral and total leg length. The correlation between clinical examination and scanogram was analysed using the Pearson Product Moment Correlation.
RESULTS: Of the 35 patients, 15 patients (43%) had a measurable LLD. There was a positive correlation between direct leg length measurement and the block test (P = 0.003), and between the block test and patient perception of limp and LLD. CT scanogram was performed on 29/35 patients. There was no correlation between CT scanogram and clinical measurement of leg length or between CT scanogram and patient perception of LLD or limp. DISCUSSION: Leg length discrepancy commonly occurs following treatment of femoral shaft fractures. We found that there was a strong correlation between direct leg length measurement and the block test, and between both methods of clinical leg length measurement and patient perception of a limp or LLD. Our study found no correlation between CT scanogram and clinical leg length measurement or patient perception of limp or LLD.
CONCLUSION: Our study shows that physical examination (direct measurement and the block test) is more reliable and clinically relevant than CT scanogram measurement in the assessment of LLD after femoral fracture.