Experimental disruption of the labrum has been shown to compromise its sealing function and alter cartilage lubrication. However, it is not known whether pathological changes to the labrum secondary to femoro-acetabular impingement (FAI) have a similar impact on labral function. This study was performed to determine the effect of natural labral damage secondary to abnormal femoral morphology on the labral seal. Ten intact hip specimens were obtained from male donors (47.8 ± 1.5 yrs) for use in this study. CT reconstructions demonstrated that 6 specimens were of normal morphology, while 4 displayed morphology typical of cam-FAI. Specimens were dissected free of the overlying soft tissue, leaving the capsule and labrum intact. Each specimen was potted and placed in a loading apparatus (0.5 BW). Pressures developed within the central and peripheral compartments were monitored with miniature pressure transducers. The sealing capacity of the labrum was measured by introducing fluid into the central compartment at a constant rate until transport was detected from the central to the peripheral compartment. These measurements were performed in 10 functional positions simulating sequential stages of gait, stooping, and pivoting. During testing, the 3D motion of the femoral head in the acetabulum was measured with motion analysis combined with computer visualization. Peak pressures were compared between specimens with and without labral damage for each of the three activities (p < 0.05).Objectives:
Methods:
Despite the suggestion by Virchow in 1856 that thrombosis was the result of venous stasis, endothelial dysfunction and hypercoagulability there are some fundamental questions which remain to be answered. The published studies fail to provide specific details such as cast type and anatomical location of the thrombosis, but instead focus on the incidence of VTE and which chemical thromboprophylaxis is most effective. Previous studies of VTE in trauma patients have involved small numbers of patients and have not look at the risk medium to long term risk. Most importantly they have not looked at the site of the VTE. This makes interpretation of the link between cast and VTE even more complex. We analysed 1479 consecutive trauma cast applications and the incidence of symptomatic VTE in the six months following the injury. The diagonosis, cast type and site of the VTE was recorded.Background
Methodology
There is mounting evidence to suggest a vascular insult is responsible for Perthes' disease, and it is suggested that this may have long-term implications for the vascular health of affected individuals. This study sought to use ultrasound measures to investigate vascular structure and function in children affected by Perthes' disease. This case control study encompassed 149 cases and 146 controls, frequency matched for age and sex. Endothelial function was measured using the technique of flow-mediated dilatation of the brachial artery, and alterations in arterial flow were recorded in response to an ischaemic stimulus.Objective
Material and Methods
It has been speculated that impact deformation of thin 1-piece cups used for modern metal-on-metal hip replacement may contribute to early failure. The purpose of this study was to reproduce typical impact deformation and quantify the effect of this on the frictional torque generated at the hip. We tested nine hip couples of three designs (the ASR, BHR and Durom) and three sizes (42mm, 46mm and 50mm). A custom compression device was designed to replicate the in vivo forces and impact deformation of 1-piece metal cups reported in the literature. Each cup was mounted in the device, which itself was mounted on a mechanical testing machine. The cups were compressed with incremental loads up to a maximum of 2000N. At each increment we measured cup deformation, and then the head component was seated into the cup. The hip was lubricated and the head component rotated 60 degrees axially within the cup and the axial torque was measured.Introduction
Methods
The muscles of the leg collectively comprise the calf pump, however the action of each muscle group on calf pump function is not known. Patients with foot or ankle injury or surgery are often advised to perform foot and ankle movements to help prevent deep venous thrombosis. Our aim was to determine which foot and ankle movements were most effective in stimulating the calf pump. Method: Nine healthy participants were enrolled in this research and ethics approved prospective study. Participants with a previous history of peripheral vascular disease, varicose veins, deep venous thrombosis or previous foot and ankle surgery were excluded. Each participant followed a standardized protocol of foot and ankle movements, starting with foot in neutral position and the baseline and movement peak systolic velocity within the popliteal vein was measured during each movement. The movements tested were toe dorsiflexion, toe plantar flexion, ankle dorsiflexion, ankle plantar flexion. The mean patient age was 34 years (range 28–58), the majority were female (n = 6). All movements resulted in statistically significant changes in peak systolic velocity (p = <0.05). In order of decreasing peak velocity the exercises which had greatest effect on calf pump function were: Ankle dorsiflexion (101cm/s), Ankle plantarflexion (84cm/s), Toe dorsiflexion (63cm/s), Toe plantarflexion (59cm/s). We have shown that all four exercises significantly increased calf pump function. The greatest effect was seen with ankle movements.Introduction
Results
Knee prostheses retrieved at revision often show patterns and severity of damage neither seen nor predicted from standard wear simulator testing. We hypothesized that this is because these implants are exposed to combinations of loads and motions that are more damaging than the simple loading profiles utilized in laboratory testing. We examined the magnitude, direction, and combination of forces and moments acting on the knee during various activities in order to guide the future development and testing of high-performance knee replacements. In vivo data from five patients with instrumented tibial implants were obtained from an open database (www.orthoload.com). We determined the direction and magnitude of forces and moments that the knee experiences during the following common physiologic activities: stair descent, stair ascent, deep knee bend, one leg stance, and walking. In order to capture the loading pattern, we investigated the three component forces and moments acting on the knee at several high demand points for each of these activities. The e-tibia data were compared to the loading profiles used in conventional laboratory testing (ISO 14243-1).Introduction
Methods
The ‘first generation’ Metal on Metal bearing devices was typically produced from cast, high carbon CoCrMo alloy and was in the as-cast condition. They exhibited course, hard primary, and block carbides supported by a softer matrix material. This bi-phasic condition has been verified through reported literature and forensic scientific studies of ‘long-term survived’ retrieved ‘first generation’ devices. The as-cast microstructure of CoCrMo alloys possesses superior wear resistance to the microstructures formed following post cast thermal treatments. It has been well reported that the improvement of mechanical properties, such as tensile or fatigue strength, can be achieved through the thermal treatment of this alloy. Thermal treatments of this alloy have been found to alter its’ microstructure with a significant modification to the carbide phase morphology. The modifications vary with a tendency for a refinement of the carbide size through dissolution of the chromium and molybdenum through solid state solution. Through the examination of the wear patterns of retrieved devices and wear testing of this material in its’ various microstructural conditions, it has been shown that modifications to the carbide morphology, to achieve improved mechanical properties, reduces its’ bio-tribological properties/performance leading to a lower wear resistance. The as-cast carbide morphology is the most mechanically stable condition and with its’ volume fraction, reduces the potential for adhesive wear of the matrix through ‘matrix to matrix’ contact of the two opposing bearing surfaces. It has been reported that abrasive wear is the typical mechanism for metal on metal bearings due to the generation of ‘third body’ particles from carbide asperity tips fracturing during the initial ‘running-in’ period [typically 500k to 1M cycles]. After this stage the carbides become almost level with the surrounding softer matrix material with ‘third body’ scratches dominating the surface topography. Evidence of surface pitting on ‘first generation’ devices [McKee Farrar and Muller] and modern high carbon wrought devices [Metasul] has been attributed to adhesive/fatigue wear following surface-to-surface contact. Therefore, in microstructural conditions, where there is a reduced carbide volume fraction, or no carbides present, wear resistance is reduced. To test this hypothesis two wear tests have been carried out on CoCrMo samples produced from the same chemistry alloy, with varying microstructures, using Calowear [abrasive] and Pin on Dist [adhesive] tests. The as-cast microstructural condition was determined to have the lowest wear coefficient [k=mm3/Nm] in both tests, however statistical significance at 90% confidence interval was only confirmed in the Calowear Test. Examination of wear scars confirmed the mechanical stability of the as-cast carbide phase. It is noted, however that there are papers which have been published offering a divergence of opinion to this hypothesis and which have been considered by this author.
In 1997 the “step-less” SL Plus (Endoprothetik, Rotkreuz, Switzerland) cementless total hip arthroplasty was introduced to our unit. During the passed 12 months, a retrospective study has been performed in order to evaluate the clinical and radiographic results of this arthroplasty. The preliminary results of the first 50 patients to have completed the clinical and radiographic follow-up have been evaluated. Of the 50 patients, 56 primary total hip arthroplasties were performed, in all cases the SL Plus stem was used. In 52 cases the cementless Doetz acetabular cup, made by the same manufacturer, was used. The other 4 acetabular components were: 2 long stemmed cementless components for developmental dysplasia, 1 standard cementless cup and 1 cemented cup, made by other manufacturers. All patients were reviewed clinically and radiographically. The mean follow-up time was 3 years, range 2 – 5 years. The mean Harris Hip Score was 90 (37 – 100). Patient satisfaction was: 98% satisfied, 2% dissatisfied (p <
0.001). Radiographic assessment demonstrated that all 52 (100%) Doetz acetabular cups osseointegrated, with 53 (95%) acetabular cups osseointegrating in total (p <
0.002). Of the SL Plus stems, 44 (79%) osseointegrated (p <
0.002). The following post-operative complications were observed: 2 dislocations, 2 superficial wound infections, 1 myocardial infarction, 1 sciatic nerve palsy and 1 deep vein thrombosis. The overall complication rate is high at 13%, but with no implant related failures. Nevertheless, the preliminary clinical and radiographic results of the SL Plus stem and Doetz acetabu-lar cup total hip arthroplasty are encouraging.
