Finite element analysis of the rotator cuff: A systematic review

Effect of geometrical design variables on implantation configuration and fixation stiffness of titling bone anchors: A parametric finite element study

The mechanical interaction of a tilting anchor and cancellous bones of various densities was simulated using finite element modeling. The model enjoyed a sophisticated representation of the bone, as an elasto-plastic material with large deformation capability. The anchor's tilting action during implantation phase, as well as its fixation stiffness during pull-out test, were predicted by the model and a parametric study was performed to investigate the effects of the anchor's distal width and corner fillet radius, on these measures. The model predictions were validated against the results of an experimental test on ovine humerus specimens. The model could reasonably reproduce the tilting action of the anchor during the implantation phase. Comparison of the model predictions with the experimental results revealed similar trends during both the implantation and the pull-out phases, but smaller displacement magnitudes (end points: 1.4 vs. 2.1 mm and 4.6 vs. 5.2 mm, respectively). The results of the parametric study indicated substantial increase in the fixation stiffness with increasing bone density. Reducing the distal width and increasing the fillet radius improved the anchor's implantation configuration and fixation stiffness in low-density bones. For high-density bone applications, however, a larger distal width was favored for improving the fixation stiffness.

Moving forward: A review of continuous kinetics and kinematics during handcycling propulsion

Wheelchair users (WCUs) face high rates of shoulder overuse injuries. As exercise is recommended to reduce cardiovascular disease prevalent among WCUs, it is becoming increasingly important to understand the mechanisms behind shoulder soft-tissue injury in WCUs. Understanding the kinetics and kinematics during upper-limb propulsion is the first step toward evaluating soft-tissue injury risk in WCUs. This paper examines continuous kinetic and kinematic data available in the literature. Attach-unit and recumbent handcycling are examined and compared. Athletic modes of propulsion such as recumbent handcycling are important considering the higher contact forces, speed, and power outputs experienced during these activities that could put users at increased risk of injury. Understanding the underlying kinetics and kinematics during various propulsion modes can lend insight into shoulder loading, and therefore injury risk, during these activities and inform future exercise guidelines for WCUs.

A Validated Three-Dimensional, Heterogenous Finite Element Model of the Rotator Cuff and The Effects of Collagen Orientation

Continuum mechanics-based finite element models of the shoulder aim to quantify the mechanical environment of the joint to aid in clinical decision-making for rotator cuff injury and disease. These models allow for the evaluation of the internal loading of the shoulder, which cannot be measured in-vivo. This study uses human cadaveric rotator cuff samples with surface tendon strain estimates, to validate a heterogeneous finite element model of the supraspinatus-infraspinatus complex during various load configurations. The computational model was considered validated when the absolute difference in average maximum principal strain for the articular and bursal sides for each load condition estimated by the model was no greater than 3% compared to that measured in the biomechanical study. The model can predict the strains for varying infraspinatus loads allowing for the study of load sharing between these two tightly coordinated tendons. The future goal is to use the modularity of this validated model to study the initiation and propagation of rotator cuff tear and other rotator cuff pathologies to ultimately improve care for rotator cuff tear patients.