Long Bone Biomechanics

Authors:
Rebecca J.Gilmour, Megan B.Brickley, ErikJurriaans, Tracy L.Prowse

Objective
This study uses biomechanical data from tibiae to investigate the functional consequences of lower limb fractures. Adults with malunited fractures are hypothesized to have experienced altered mobility, indicated by asymmetric tibial cross-sectional geometries (CSG).

Materials
Ninety-three adults from Roman (1st to 4th centuries CE) Ancaster, UK and Vagnari, Italy (Ancaster n = 16 adults with lower limb fracture:53 without fracture; Vagnari n = 5:19)

Methods
Biplanar radiographs were used to quantify and compare tibial CSG properties and asymmetries between individuals with and without fractures to femora, tibiae, and/or fibulae. The amount of angulation, rotation, and overlap, indicative of linear deformity, were measured for each fracture. Individuals who loaded their fractured leg differently than their opposite, uninjured leg were identified using outlying amounts of CSG asymmetry.

Results
Two Ancaster individuals had poorly aligned fractures. None of the Ancaster or Vagnari individuals with lower limb fractures had CSG properties or asymmetries outside the calculated normal ranges.

Conclusions
Regardless of how a fracture healed, individuals at Ancaster and Vagnari generally resumed mobility after trauma whenever possible.

Significance
This research contributes information about injury recovery and suggests that resilient behaviors and persistent mobility may have been valued or required responses to fracture in the study communities. This work advises that impairment should not be inferred based solely on the appearance of lesions.

Limitations
Site, sex, and age patterns in injury recovery are not evaluated due to sample size limitations.

Suggestions for further research
Biomechanical assessments of post-traumatic function in varied cultural contexts are advised in order to further characterize the impact that physical and social factors have on injury recovery.

Longitudinal rotation of the forearm (pronosupination) is an essential component of human manipulative tasks. The efficiency of this movement is dependent not only on the rotatory muscles but also on several morphological and structural features of the upper limb. In a recent study, we observed that the size and orientation of the humeral medial epicondyle played an important role in forearm rotatory ability. We further observed that the forearm muscular activity, specifically the motion of pronation, promotes radial curvature, which, in turn, enhances rotational efficiency. In this study, we aim to test whether the orientation of the medial epicondyle is an activity-dependent parameter or whether it is an invariable morphological feature characteristic of the human skeleton. We analysed the upper limb entheseal changes in 30 human skeletons and assessed the role of several functional groups in the anteroposterior and proximo-distal orientation of the medial epicondyle. Our results indicate that the orientation of the medial epicondyle is partially an activity-dependent feature basically determined by elbow flexor-extensors and hand and wrist flexors. The orientation of the medial epicondyle towards more posterior and proximal positions causes a gain of efficiency in the pronation range when the elbow is extended and in the supination range when the elbow is flexed. Therefore, we suggest that the medial epicondyle of the humerus is a structure involved in the manipulative capacities of the human upper limb, and its orientation presents a range of variation that may be associated with the functional enhancement of these abilities. Copyright © 2012 John Wiley & Sons, Ltd.