Biomechanical Evaluation and Comparison of Clinically Relevant versus Non-relevant Leg Length Inequalities

Abstract BackgroundLeg length inequalities (LLIs) are a frequent condition in every population. It is common clinical practice to consider LLIs of 2cm and more as relevant and to treat those. However, the amount of LLIs that need treatment is not clearly defined in literature and the effect of real LLIs on the musculoskeletal system above and below 2cm have not been studied biomechanically before.Research question: Are the spine and pelvis affected differently in patients with LLIs <2cm and ≥2cm.MethodsBy using surface topography, we evaluated 32 patients (10 females, 22 male) with real LLIs of ≥2cm (mean: 2.72cm; n=10) and compared their pelvic position and spinal posture to patients with LLIs <2cm (mean: 1.24cm; n=22) while standing and walking. All patients were measured with a surface topography system during standing and while walking on a treadmill. To compare patient groups, we used Student t-tests for independent samples.ResultsPelvic obliquity was significantly higher in patients with LLI ≥2cm during the standing trial (p=0.045) and during the midstance phase of the longer leg (p=0.023) while walking. Further measurements did not reveal any significant differences (p=0.06-0.706).ConclusionThe results of our study suggest that relevant LLIs of ≥2cm mostly affect pelvic obliquity and do not lead to significant alterations in the spinal posture during a standing trial. Additionally, we demonstrated that LLIs are better compensated when walking, showing almost no significant differences in pelvic and spinal posture between patients with LLIs smaller and greater than 2 cm. This study shows that LLIs ≥2cm can still be compensated; however, we do not know if the compensation mechanisms may lead to long-term clinical pathologies.