Musculoskeletal Parameter Variability Explains Variability in Elbow Flexion Strength Deficit Due to Long Head Biceps Tear: a Stochastic Model

Rupture of the Long Head of Biceps tendon (LHB) results in varying elbow flexion strength deficit (mean deficit: 8%, S.D. 12% of mean) (Mariani et al. 1988). This variability in strength is interesting because it is previously unexplained. Observations of musculoskeletal parameters also exhibit variability (Murray et al. 2000). We hypothesize that the variation in elbow flexion strength in healthy normals and in subjects with LHB rupture is explainable via variability in musculoskeletal parameters, specifically muscle physiologic cross sectional areas (PCSA), moment arms and optimal muscle lengths (OML) of elbow flexors. The purpose of this research was to use a stochastic model to predict the median and distribution of maximum isometric elbow flexor muscle forces when modeling PCSAs, moment arms, and OMLs as random variates.