Abstract
Introduction: Leg length discrepancy (LLD) following hip arthroplasty can produce abnormal loading leading to pain, increased wear and loosening of implants. The aim of this study was to investigate the relationship between LLD and static limb loading.
Methods: A pedobarograph was used to measure the limb loading of 19 normal volunteers aged 18 to 58. Each volunteer was asked to stand on the Pedobarograph with both feet so that their weight could be recorded. The load through the left leg was then recorded with the right leg on a platform level beside it. The platform was then raised in 1 cm increments to 6 cm, to simulate different levels of LLD. In each position 3 readings were taken with the right knee flexed (pelvis level), and straight (pelvis tilted).
Results: When the feet were level the left leg took 53 % of the load. As the height of the right foot was increased the load through the left leg increased in a non-linear fashion.
With the knee flexed, a 1 cm difference produced a 3 % increase in loading. This was significant (P< 0.05). All subsequent increases were also significant. The largest increase in load was observed between 1 cm & 2 cm (+5 %). At 6cm the left leg load was 70.9 %.
With the pelvis tilted, there were smaller increases in loading. These did not become significant until a difference of 5 cm. The maximum load was 62.1 % at 6 cm.
Discussion: The length-loading relationship was non-linear. The pelvis tilted stance produced less loading asymmetry, but more discomfort than the flexed knee stance.
Correspondence should be addressed to BHS c/o BOA, at the Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London, WC2A 3PE, England.
