Reports of improved functional outcome of Metal on Metal Hip Resurfacing Arthroplasty (mHRA) to Total Hip Replacement needs to be balanced with concerns of metal ion release. By removing cobalt-chrome, cHRA reduces these risks. To the author's knowledge, there is no data available on functional outcomes of cHRA, therefore the aim of the study was to compare the function between cHRA patients and mHRA patients. 24 patients received a unilateral cHRA (H1, Embody) and was compared to 24 age and gender matched patients with a unilateral mHRA (BHR, Smith and Nephew). All patients completed the Oxford Hip Score (OHS)[T2] and underwent gait analysis on an instrumented treadmill before and at a mean of 74wks (+/− 10) for mHRA and 53wks (+/− 2) for cHRA post op. Walking trials started at 4km/h and increased in 0.5km/h increments until a top walking speed (TWS) was achieved. Vertical ground reaction forces (GRF) were recorded along with the symmetry index (SI). Spatiotemporal measures of gait were also recorded. Vertical GRF were captured for the entire normalised stance phase using statistical parametric mapping (SPM; CI = 95%). The gain in OHS was similar: H1 (25-46), BHR(27-47). TWS increased by 19% with H1 (6.02 – 8.0km/hr), and 20% with BHR (6.02 – 7.37km/hr). SPM of the entire gait cycle illustrated the restoration of symmetry in both groups with no difference in GRF across the stance phase between groups at 5km/hr pre-op and post-op. At faster speeds (6.5km/hr), H1 patients had a mid-support GRF slightly closer to normal compared to BHR. Both groups increased step length similar from pre to post op (H1:0.76 – 0.85cm, BHR:0.77-0.86cm). In this study, subjective and objective functional outcome measures suggest that short term functional outcomes of ceramic resurfacing is not inferior to metal resurfacing

Abstract. Introduction. In general the life expectancy of population is improving. This is causing to increase case load of peri-prosthesis fractures after joint replacements. We present our results of peri-prosthesis fracture around hip managed by revision arthroplasty. Methods. A retrospective analysis of 24 consecutive patients of periprosthetic hip fracture treated with a revision arthroplasty at Major Trauma Centre between February 2021 and January 2022. Results. 12 male and 12 female patients, average age 78 years. 3 fractures around BHR prosthesis, 2 type A, 15 type B and 3 of type C (Vancouver). The surgery was done in an average 6 days after injury (range 1–14). 6 patients died in follow up, 1 patient contracted infection, 2 developed LLD and 1 patient had multiple dislocations. 6 patients had revision using endo-prosthesis. Advanced age with peri-prosthesis fracture has increased risk of mortality (average age 84.5 years). Conclusion. Endo-prosthesis replacement had higher risk of dislocation, infection and mortality. Overall patients do well after a revision arthroplasty for periprosthetic hip fracture. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Metal on metal (MoM) bearings in hip surgery may result in increased blood levels of metal ions. The nature of the relationship between ion levels and failure is still not fully understood. We compared three cohorts of resurfacing patients, grouped for brand and diameter of femoral component. We measured the blood level of Cobalt and Chromium ions at an average of 4 years postoperatively. The results were grouped as follows: Birmingham Hip Resurfacing ≥50 mm diameter, Durom resurfacing ≥50 mm diameter and Durom resurfacing <50 mm diameter. 120 patients were included in each group. There were significant differences in Cobalt levels between the groups. The median cobalt level for the BHR group was 8 nmol/L higher than the Durom ≥50 mm group (P<0.005). The Durom <50 mm group recorded cobalt levels 8.5 nmol/L higher than the Durom ≥50 mm group (P=0.0004). Revision rates were equal in the Large BHR's and Large Durom HRA (both 3.3%) however the small Durom HRA had a revision rate of 8.3%. Elevated blood ion levels can indicate a failing MoM bearing. When similar ion levels were reported for BHR and small Durom the latter had significantly higher revision rates. The large BHR and large Durom HRA have similar revision rates yet the large Durom HRA had significantly lower metal ion levels. Only one of the patients having revision surgery (n=18) had metal ion levels above the MHRA threshold. This suggests ion levels do not absolutely predict the rate of HRA failure. Given similar revision rates with different ion levels between the large BHR and large Durom hips, mechanisms of failure leading to revision must be isolated from the release of metal ions. Therefore clinical and image based follow up are recommended in addition to ion level monitoring

The effects of the method of fixation and interface conditions on the biomechanics of the femoral component of the Birmingham hip resurfacing arthroplasty were examined using a highly detailed three-dimensional computer model of the hip. Stresses and strains in the proximal femur were compared for the natural femur and for the femur resurfaced with the Birmingham hip resurfacing. A comparison of cemented versus uncemented fixation showed no advantage of either with regard to bone loading. When the Birmingham hip resurfacing femoral component was fixed to bone, proximal femoral stresses and strains were non-physiological. Bone resorption was predicted in the inferomedial and superolateral bone within the Birmingham hip resurfacing shell. Resorption was limited to the superolateral region when the stem was not fixed. The increased bone strain observed adjacent to the distal stem should stimulate an increase in bone density at that location. The remodelling of bone seen during revision of failed Birmingham hip resurfacing implants appears to be consistent with the predictions of our finite element analysis.

A total of 20 pairs of fresh-frozen cadaver femurs were assigned to four alignment groups consisting of relative varus (10° and 20°) and relative valgus (10° and 20°), 75 composite femurs of two neck geometries were also used. In both the cadaver and the composite femurs, placing the component in 20° of valgus resulted in a significant increase in load to failure. Placing the component in 10° of valgus had no appreciable effect on increasing the load to failure except in the composite femurs with varus native femoral necks. Specimens in 10° of varus were significantly weaker than the neutrally-aligned specimens.

The results suggest that retention of the intact proximal femoral strength occurs at an implant angulation of ≥ 142°. However, the benefit of extreme valgus alignment may be outweighed in clinical practice by the risk of superior femoral neck notching, which was avoided in this study.

Hip simulators have been used for ten years to determine the tribological performance of large-head metal-on-metal devices using traditional test conditions. However, the hip simulator protocols were originally developed to test metal-on-polyethylene devices. We have used patient activity data to develop a more physiologically relevant test protocol for metal-on-metal devices. This includes stop/start motion, a more appropriate walking frequency, and alternating kinetic and kinematic profiles.

There has been considerable discussion about the effect of heat treatments on the wear of metal-on-metal cobalt chromium molybdenum (CoCrMo) devices. Clinical studies have shown a higher rate of wear, levels of metal ions and rates of failure for the heat-treated metal compared to the as-cast metal CoCrMo devices. However, hip simulator studies in vitro under traditional testing conditions have thus far not been able to demonstrate a difference between the wear performance of these implants.

Using a physiologically relevant test protocol, we have shown that heat treatment of metal-on-metal CoCrMo devices adversely affects their wear performance and generates significantly higher wear rates and levels of metal ions than in as-cast metal implants.