BackgroundWhile leg stiffness during running has been shown to be lower in children with cerebral palsy compared to their typically developing peers, no studies have examined leg stiffness during running in adults with traumatic brain injury. The aim of this study was to compare leg stiffness during running in adults with traumatic brain injury to healthy controls. MethodsSixty-one adults with traumatic brain injury and 20 healthy controls were included. Participants ran overground while three-dimensional kinematic and kinetic data were recorded. Leg stiffness was calculated during the stance phase of running. Statistical analyses to compare leg stiffness between limbs and between groups were conducted using t-tests. FindingsThere was a large range of leg stiffness in adults with traumatic brain injury during running (affected leg median = 21.56 [range 11.07 to 57.44] kN/m; less affected leg =20.87 [9.38 to 54.72] kN/m) compared to healthy controls (20.94 [13.40 to 31.50] kN/m). However, there were no statistically significant differences in leg stiffness during running between the affected and less affected limbs (p = 0.59, effect size [ES] =0.08) nor between both traumatic brain injury limbs and healthy controls (affected limb; p = 0.44, ES =0.12; less affected limb; p = 0.47, ES =0.11). InterpretationAlthough no statistical significance was found on a group level, the results demonstrated high variability in leg stiffness in traumatic brain injury compared to healthy controls. Further research is needed to determine which factors influence leg stiffness during running and how this measure relates to clinical outcomes in traumatic brain injury.

BackgroundIndividuals with a recent anterior cruciate ligament reconstruction may demonstrate an altered movement strategy for protecting the knee and maintaining stability. Altered knee movement might lead to abnormal intra-articular load, potentially contributing to early knee osteoarthritis onset. A protective strategy may be particularly evident during active tasks that induce a pivot-shift manoeuvre, such as a step-down and cross-over task. In this study, we investigated whether knee joint mechanics and muscle activity differed between participants early (∼3 months) following reconstruction (n = 35) to uninjured controls (n = 35) during a step-down and cross-over task with a 45° change-of-direction. MethodsWe used motion capture, force plates and surface electromyography to compare time-normalised curves of sagittal and transverse-plane knee mechanics and muscle activity during the cross-over phase between groups using functional t-tests. We also compared knee mechanics between sides within the injured group and compared discrete outcomes describing the cross-over phase between groups. FindingsCompared to controls, the injured participants had greater knee flexion angle and moment, lower internal rotation moment, more preparatory foot rotation of the pivoting leg, a smaller cross-over angle, and a longer cross-over phase for both the injured and uninjured sides. The injured leg also had greater biceps femoris and vastus medialis muscle activity compared to controls and different knee mechanics than the uninjured leg. InterpretationIndividuals with anterior cruciate ligament reconstruction showed a knee-stabilising and pivot-shift avoidance strategy for both legs early in rehabilitation. These results may reflect an altered motor representation and motivate considerations early in rehabilitation.

BackgroundKnowing the mechanical properties of trabecular bone is critical for many branches of orthopaedic research. Trabecular bone is anisotropic and the principal trabecular direction is usually aligned with the load it transmits. It is therefore critical that the mechanical properties are measured as close as possible to this direction, which is often perpendicular to a curved articulating surface. Methods: This study presents a method to extract trabecular bone cores perpendicular to a curved articulating surface of the distal femur. Cutting guides were generated from computed tomography scans of 12 human distal femora and a series of cutting tools were used to release cylindrical bone cores from the femora. The bone cores were then measured to identify the angle between the bone core axis and the principal trabecular axis. FindingsThe method yielded an 83% success rate in core extraction over 10 core locations per distal femur specimen. In the condyles, 97% of extracted cores were aligned with the principal trabecular direction. InterpretationThis method is a reliable way of extracting trabecular bone specimens perpendicular to a curved articular surface and could be useful across the field of orthopaedic research.