Hip dislocations remain one of the most common complications of total-hip-arthroplasty (Zahar et al.,2013). There is contradicting evidence whether the surgical approach affects dislocation rates (Sheth et al., 2015; Maratt, 2018). The aim of this study was to develop instrumentation to measure hip forces during simulated range-of-motion tests where the hip was forced to dislocate in cadaveric specimen. A total-hip-replacement was completed on both hips of a single cadaveric specimen by a trained orthopaedic surgeon during a lab initiated by DePuy. A direct-anterior surgical approach was performed on the right leg and a posterior approach was performed on the left. Before final implantation of the femoral component, a trial reduction with a femoral neck trial was performed. The neck trial was modified with strain gauges placed around the shaft which were designed to measure resultant hip forces throughout the range-of-motion assessment. A force-calibration was performed using a calibration-block to convert strain to force values.Abstract
OBJECTIVES
METHODS
The mechanical properties of porcine tibial plateau (TP) cartilage are shown to vary topographically. Low Elastic moduli (Em) were found in the positions where unicompartimental knee osteoarthritis (OA) lesions are typically expected to develop. These results suggest that there is a different response to load in these areas. OA is one of the ten most disabling diseases in developed countries. OA of the knee, in particular, is a major cause of mobility impairment; up to 40% of the population over the age of 70 suffers from OA of the knee. It has been observed that unicompartmental knee OA occurs with very distinct and repeatable lesion patterns. It is hypothesised that these patterns are the result of differences in the material properties throughout articular cartilage. The aim of this study was to measure the mechanical properties of porcine cartilage in a whole undamaged TP.Summary
Introduction
Nanometre-sized particles of ultra-high molecular weight polyethylene have been identified in the lubricants retrieved from hip simulators. Tissue samples were taken from seven failed Charnley total hip replacements, digested using strong alkali and analysed using high-resolution field emission gun-scanning electron microscopy to determine whether nanometre-sized particles of polyethylene debris were generated We isolated nanometre-sized particles from the retrieved tissue samples. The smallest identified was 30 nm and the majority were in the 0.1 μm to 0.99 μm size range. Particles in the 1.0 μm to 9.99 μm size range represented the highest proportion of the wear volume of the tissue samples, with 35% to 98% of the total wear volume comprised of particles of this size. The number of nanometre-sized particles isolated from the tissues accounted for only a small proportion of the total wear volume. Further work is required to assess the biological response to nanometre-sized polyethylene particles.
