Comparative anthropometry and biomechanics of locomotion in runners with and without structural leg length discrepancy

Author(s)

Carla Sonsino Pereira

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina (FM/SBD)
• Defense date: 2006-09-25

Examining board members

Isabel de Camargo Neves Sacco; Paula Hentschel Lobo da Costa; Silvia Maria Amado João

• Advisor: Isabel de Camargo Neves Sacco

Abstract

There is a high incidence of leg length discrepancy (LLD) in general population, which could be structural, when the difference occurs in bone structures, or functional, as a result of mechanical changes at the lower limbs. The discrepancy can also be classified by its magnitude, being mild, intermediate, or severe. Many anthropometric methods are used to evaluate discrepancy, however the most common are clinical methods, which use a tape to measure the distance between two bone landmarks. Radiographic methods can also be used, although they are characterized by high cost and radiation exposure. Mild LLD has been associated with stress fractures, lower back pain and osteoarthritis. When the discrepancy occurs in subjects whose mechanical loads are increased by their professional, daily or recreational activities, these disorders might appear early and severely. The aim of this study was to compare several anthropometric measurements of LLD used in clinical practice with the scanogram in runners, and to study the ground reaction forces during gait and running in runners with mild and structural LLD. Results demonstrated an association between LLD and higher incidence of symptoms in runners\' hips and knees. Clinical measures ASIS/MM (R=0.96; p=0.000), ASIS/LM (R=0.97; p=0.000), Crest/MM (R=0.95; p=0.000) and Umbilicus/MM (R=0.92; p=0.000) presented high correlation with scanogram. Although, only the clinical measurement Umbilicus/MM (0.8 ± 0.6 cm; 0.8 ± 0.5%) detected absolute and relative discrepancy between lower limbs similar to that detected with scanogram (0.6 ± 0.5 cm; 0.8 ± 0.6%). Results also showed that increasing discrepancy leads to overloads in both lower limbs, which may lead to orthopedic disorders after extended periods. Subjects with mild LLD of 0.5 to 2.0 cm presented higher values of Fzmin (0.56 ± 0.08 BW) at the shorter limb during gait, and higher values of Fz2 and PO at the shorter limb (2.48 ± 0.22 BW; 17.18 ± 3.35 BW/s) during running. Subjects with mild discrepancy of 1.0 to 2.2 cm presented a smaller rate of load 1 (9.19 ± 1.49 BW/s) at the longer limb during gait in comparison to control subjects (10.44 ± 1.72 BW/s), and higher values of Fz1 at the longer limb during running (1.70 ± 0,17BW ) relative to control subjects (1.57 ± 0.16PC). Subjects with mild discrepancy also showed higher values of Fz2 and PO at the shorter limb (2.55 ± 0.22 BW; 17.07 ± 3.31 BW/s). Nevertheless, subjects with mild LLD displayed symmetrical gait and running according to values obtained by Absolute Symmetric Index of vertical and horizontal GRF variables. (AU)