THE EFFECT OF STANCE ON STATIC LOADING WITH LEG LENGTH DISCREPANCY

Leg length discrepancy (LLD) is a recognised complication of total hip arthroplasty. LLDs can cause abnormal weight bearing, leading to increased wear, aseptic loosening of replacement hips and pain. To compensate for LLDs the patient can either flex the knee of the long leg or tilt their pelvis. The aim of this project was to investigate how stance affects static limb loading of patients with leg length discrepancy. A pedobarograph was used to measure the limb loading of 20 normal volunteers aged 19 to 60. A 2 second recording with both feet on was taken to establish their body weight. Readings were taken of the left foot with the right level, 3.5cm lower (simulating a long left leg) and 3.5cm higher. In each case three readings were taken with the knee flexed and three readings with the knee extended. When both feet were at the same level, the left limb took 54% of the load. When the right foot was lower and the left knee flexed, the left leg took 39 % of the load (P With the right foot higher and right knee flexed, the left leg took 65 % of the load (P These results show that weight distribution is increased in the simulated shorter limb. Loading is greater when the longer limb is flexed. Tilting the pelvis reduced the load. However this may cause pelvic and spinal problems. Uneven load distribution is likely to lead to early fatigue when standing and may explain why some post arthroplasty patients with limb length discrepancy have poor outcomes.