Malposition of the glenoid component in total shoulder arthroplasty (TSA) is associated with higher strain patterns and can result in component loosening. Glenoid hardware placement and optimal size remain challenging due to the difficult joint exposure and visualization of anatomical reference landmarks during the procedure. Therefore, understanding both normal and variant patterns of glenoid anatomy is imperative for success in TSA. To better understand individual variations in glenoid morphology, this study aimed to compare the glenoid anatomy in a cohort of male and female patients from the United States (US) and Australia (AUS). Computed tomography (CT) data were analyzed from 41 male and 35 female shoulders; 39 of which were from a US population and 37 from an AUS population. These data were used to create statistical shape models (SSM) representing the average and ±1 standard deviations of the first mode of variation of each group (Materialise, Leuven, Belgium). All measurements were performed with 3-matic computer assisted design software (Materialise, Leuven, Belgium). On each model, glenoid height was measured as the distance from the most superior to the most inferior point on the glenoid face. Glenoid width was measured as the distance from the most anterior to the most posterior point on the glenoid face. Surface area was measured as the concave surface of the glenoid face (Figure 1). Glenoid vault depth was measured in the midsection of the glenoid face.Background
Methods
Reverse Shoulder Arthroplasty (RSA) improves the mechanics of rotator cuff deficient shoulders. To optimize functional outcomes and minimize failures of the RSA manufacturers have recently made innovative design modifications with lateralized components. However, these innovations have their own set of biomechanical trade-offs, such as increased shear forces along the glenoid bone interface. The objective of this study was to develop an efficient musculoskeletal model to evaluate and compare both the muscle forces and joint reactive force of a normal shoulder to those implanted with varied RSA implant designs. We believe these findings will provide valuable insight into possible advantages or shortcomings of this new RSA design. A kinematic model of a normal shoulder joint was adapted from publically available musculoskeletal modeling software. Static optimizations then allowed for calculation of the individual muscle forces, moment arms and joint reactive forces relative to net joint moments. An accurate 3D computer models of humeral lateralized design (HLD) (Equinoxe, Exactech, Gainesville FL, USA), glenoid lateral design (GLD) (Encore, DJO Global, Vista CA, USA), and Grammont design (GD) (Aequalis, Tornier, Amsterdam, NV) reverse shoulder prostheses was also developed and parametric studies were performed based on the numerical simulation platform.Introduction
Methods
The aim of this study was to characterize the effect of ligament water content on the accumulation of damage Ligament water content may be altered MCLs of the rabbit knee were subjected to a constant cyclic stress (28 MPa) in this After twenty-four hours of loading, ligaments cycled in hypotonic solution at 0.1 Hz had statistically significant reductions in both failure stress and failure strain. This group also demonstrated significantly more cyclic strain during loading than MCLs cycled in isotonic solution. Surprisingly, a significant difference in cyclic modulus was not detected between groups. This study has demonstrated that elevated tissue water content influences the accumulation of damage in ligaments subjected to repetitive loading
Thirty-five patients who had been surgically treated for major symptomatic isolated chronic anterior cruciate ligament deficiency by lateral extra-articular reconstruction alone were reviewed at an average of five years after operation. Seventy-seven per cent of patients reviewed were improved subjectively, and 83% of patients who were examined had objective evidence of only minor instability or none at follow-up. However, only a few patients had "normal" knees and many continued to have minor symptoms of instability with some restriction of activity. Most of the unsatisfactory results were in patients with significant chondral pathology at the time of reconstruction. While an extra-articular pivot-shift repair did not correct all the symptoms and signs completely, most patients were improved subjectively and objectively, and there were few complications.
