Impacts of Stifle Joint Remodeling on Vertical Ground Reaction Forces Following MCL Transection and Medial Meniscectomy

Functional demands placed on the human knee’s anterior cruciate ligament (ACL) vary with activity but remain impossible to measure directly in-vivo. Our lab is characterizing these demands in the sheep model by recording in vivo knee kinematics and ACL transducer voltages during activities of daily living (ADLs), reproducing these motions using the instrumented limb, and measuring the 3D forces in the ligament. However, up to 13% of patients sustaining ACL injuries will also sustain dual medial meniscus (MM) injuries and up to 10% will sustain dual medial collateral ligament (MCL) injuries. These structures are frequently left unrepaired, which may alter the ACL’s functional demands, resulting in inadequate ACL reconstruction outcomes for patients with dual injuries. Although these structures have been shown to alter ACL loading in cadaveric studies, the extent to which they impact ACL functionality during in vivo ADLs remains unknown. Moreover, changes in ACL functionality over time due to joint healing and remodeling have yet to be investigated. In this study, we aimed to track stifle joint remodeling in response to surgically imposed MCL transections and medial meniscectomies through monitoring vertical ground reaction forces (VGRFs) for three ADLs over 12 weeks. Results of this study may then be used in conjunction with future robotic studies as a tool to estimate in vivo load requirements for ACL reconstructions in patients with dual injuries.

Listed In: Biomechanical Engineering, Biomechanics, Gait, Orthopedic Research

Accelerometry for outdoor effort quantification

Assessing the lower limb properties in-situ is of a major interest for analyzing the athletic performance. From a physical point of view, the lower limb could be modeled as single linear spring which supports the whole body mass. The main mechanical parameter studied when using this spring-mass-model is the leg-spring stiffness (k). In laboratory conditions, the movements are assessed using a force plate (Meth1) which measures the ground reaction force (GRF), and a motion capture system which could estimate the displacement of the centre of mass (CoM). In this way, k is calculated as shown in equation (2).More recent methods allow to calculate k in field conditions by using either foot switches (Meth2) or accelerometry-based instruments (Meth3) which are both wireless devices. The associated calculated methods assume that force-time signal is a sine wave, described by the equation (3) with equation (4) (CT: contact time; FT: flight time). In these cases, the kinematic measurement (CoM) could be calculated either by a mathematical approach (Eq.(5)) (meth2), or by double integrating the acceleration (meth3) in order to calculate k.Thanks to their transportability, the methods 2 and 3 offer not only the possibility to assess the lower limb movements, but also, to objectively follow up the athletic abilities (performance, reactivity, force and power, stiffness) in-situ.

Listed In: Biomechanical Engineering, Biomechanics, Sports Science