Elsevier

Gait & Posture

Volume 40, Issue 4, September 2014, Pages 561-563
Gait & Posture

The effect of leg length discrepancy upon load distribution in the static phase (standing)

https://doi.org/10.1016/j.gaitpost.2014.06.020Get rights and content

Highlights

  • It is common as a further aim to alter leg length during hip arthroplasty to balance limb lengths.

  • Limb lengthening or shortening can cause adverse musculoskeletal effects.

  • A pedobarograph was used to measure limb loading when simulating a leg length discrepancy.

  • Weight distribution increased in the shorter limb when LLD was simulated.

  • Uneven weight distribution can explain why some patients with LLD have recognised poorer outcomes.

Abstract

Leg length discrepancy (LLD) is commonly recognised as a complication of total hip arthroplasty. Some patients with only minor LLD complain of major difficulties. The effect of LLD has been described in the dynamic phase, but not static phase. The aim of this project was to investigate the effect of leg length discrepancy on static limb loading (i.e. Standing). A pedobarograph was used to measure the limb loading of 20 normal volunteers whilst changing the height of the other foot thus simulating a LLD. With both feet at the same level, the left limb took 54% of the load. When the right foot was lower, (simulating a long left leg), the left leg took 39% of the load. When the right foot was higher, (simulating a long right leg), the left leg took 65% of the load. A paired t-test comparison of the simulation with the level load showed a significant difference with P = 0.002. Our results show that weight distribution increased in the shorter limb when LLD was simulated. This uneven distribution is likely to lead to premature fatigue when standing and may explain why some patients with LLD post hip arthroplasty have poorer outcomes.

Introduction

Leg length discrepancy (LLD) is a well recognised complication of total hip arthroplasty, and is perceived by up to 30% of patients post operatively [1]. Patients with LLD often develop compensatory mechanisms, which lead to a change in the kinematic pattern of lower limb joints [2], [3]. Two common compensatory mechanisms exist. One involves altering the pelvic tilt whilst flexing the hip and knee on the long side with plantar-flexion of the ankle on the short side [3]. The alternative method is by changing the obliquity of the pelvis and keeping both knees extended. The degree of compensation is varied depending on the anatomy of the patient, as well as the degree of lengthening. Pelvic obliquity is understood to compensate for LLD only up to 2.2 cm, particularly during the static phase (i.e. Standing), but greater degrees of discrepancy will require the addition of the previously described compensatory actions [2], [3].

Research has been conducted into dynamic load bearing by White et al. and Michaud et al., but there are no articles examining static function [4], [5]. The aim of this project was to investigate the effect of leg length discrepancy on static limb loading (standing), to further understanding with this field.

Section snippets

Method

Twenty healthy volunteers were selected for analysis. The volunteers had to have no history of lower limb pathology or surgery. They were aged between 19 and 60, with a mean of 38.85 years. 11 individuals were male, 9 were female. The weight of participants ranged from 50.8 to 90.0 kg (mean 71.14 kg) and height 152–190 cm (mean 172.76 cm). A pedobarograph was used to measure the limb loading of the volunteers. The pedobarograph utilised was the Musgrave™ Footprint pressure plate system. The system

Results

All selected participants completed the measurements and none were excluded prior to statistical analysis. No adjustments were made for age, gender, BMI or hip/pelvis condition.

Results showed that when both feet were at the same level, the left limb took 54% of the load. Once the right foot was lowered, simulating a long left leg, the left leg took 39% of the load when the knee was flexed, and 49% when extended (with pelvic tilt). A paired t-test of flexed knee loading compared with the level

Discussion

It is common as an additional aim to alter leg length during hip arthroplasty to balance limb lengths. However, leg length discrepancies (LLDs) of a minor degree are relatively common post arthroplasty, between 0.1  cm and 1.59 cm [6], [7]. LLD can lead to arthroplasty related complications and potentially reduce the effectiveness of the replacement over time [7]. It is also reported as a leading cause of patient dissatisfaction [8]. Discrepancy can thus adversely affect an otherwise excellent

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