Local and systemic concentrations of cobalt (Co) and chromium (Cr) ions may be elevated in patients with accelerated tribo-corrosion at prosthesis bearing surfaces and modular taper junctions. Previous studies by us and others have shown that exposure to these metals negatively affect the viability and function of osteoblasts and osteoclasts in vitro, with implications for bone health. More recently, we have observed an increase in total bone mineral density and reduced bone turnover (TRAP5b and osteocalcin) in patients with well-functioning metal-on-metal hip resurfacing (MOMHR). Here, we provide data to support the hypothesis that osteoclast differentiation and function is altered in this patient population, and that this effect is transferrable through their serum.

Patients with well-functioning MOMHR (n=18) at median follow-up of 8 years were individually matched for gender, age and time-since-surgery to a low-exposure group consisting of patients with metal-on-polyethylene total hip arthroplasty (THA). The median circulating concentrations of Co and Cr for the MOMHR group were 2.53µg/L and 2.5µg/L respectively, compared to 0.02µg/L and 0.03µg/L for the THA group. Monocyte fraction of peripheral blood was isolated from these patients, seeded onto dentine wafers and differentiated into osteoclasts using media supplemented with RANKL and M-CSF (osteoclastogenic media, OM). Cultures were monitored for the onset of resorption, following which they were treated with OM, autologous serum or serum from the other individual within the matched MOMHR - THA pair, all supplemented with RANKL and M-CSF. At the end of the culture, cells were TRAP stained and quantified for total osteoclast number, number of resorbing osteoclasts and percentage resorption using the CellD Software Package (Olympus, Southend-on-Sea, U.K.).

For cells differentiated in osteoclastogenic media, the resorbing ability of osteoclasts derived from MOMHR patients was reduced by 30% (P=0.046) compared to THA. Correlation analyses showed that chronic exposure to Co and Cr trends towards negative association with resorption ability of these osteoclasts (r = −0.3, P=0.06). Furthermore, the resorbing ability of osteoclasts generated from MOMHR patients and differentiated in autologous serum was reduced 33% (p < 0 .0001), whilst matched THA serum caused a smaller reduction of 14% (p < 0 .01). When cells derived from THA patients were differentiated in autologous serum, the resorbing ability of osteoclasts was similarly reduced by 35% (p < 0 .0001), whilst the matched MOMHR serum also caused a reduction of 21% (p < 0 .0001).

Reduced osteoclastogenic response of precursor cells from patients with higher circulating Co and Cr suggests an inherent change in their potential to differentiate into functional osteoclasts. The data also suggests that functional response of mature osteoclasts generated from patient precursor cells are dependent on the prior systemic metal concentrations and the presence of higher circulating CoCr in patients with MOMHR. These effects are modest, but may explain the subtle increase in systemic bone mineral density and decreased bone turnover observed in patients after 8 years exposure compared to age, sex, and exposure-time matched patients who received a conventional THA.

Objectives

To evaluate management, direct-medical-costs and clinical outcome profile of a large trauma unit with respect to simple elbow dislocations.

Purpose: The purpose of this study was to investigate the outcome of acetabular fractures treated in our institution with marginal impaction.

Patients & Methods: Over a 5 year period consecutive acetabular cases treated in our institution with marginal impaction were eligible for inclusion in this study. Exclusion criteria were patients lost to follow up and pathological fractures. A retrospective analysis of prospectively documented data was performed. Demographics, fracture types according to the Judet-Letournel classification, radiological criteria of intra-operative reduction (Matta) and secondary collapse, complication rates, and the Euro-Qol-5D questionnaire were documented over a median period of follow-up of 40months (12–206).

Results: Out of 400 cases, eighty-eight acetabular fractures met the inclusion criteria. The majority (93.2%) involved males with a median age of 40.5years (16–80). Half of them were posterior-wall fractures, 21.6% both column, 14.7% posterior-wall and posterior-column, 6.8% transverse, 5.7% anterior-column, 1.1% anterior-column posterior hemi-transverse. In 75% of the cases anatomical intraoperative reduction was achieved. Structural-bone-graft was used in 73.9%, and two-level reconstruction in 61%. At final follow-up, the originally achieved anatomical reduction was lost in 17/66 (25.8%), (10 PW, 4 PC+PW, 1 PC, 1 Transverse, 1 Bicolumn fracture). Avascular necrosis developed in 9.1% and heterotopic ossification in 19.3%. Full return to previous activities was documented in 48.9% of cases, the EuroQol general heath state score had a median of 80% (30–95%), full recovery was recorded as to the patients’ mobility in 51.1%, as to pain in 47.7%, as to self-care in 70.5%, as to work-related activities in 55.7%, and as to emotional parameters in 65.9%. Reoperation (heterotopic-ossification excision, total-hip-arthroplasty, removal of metalwork) was necessary in 19.2% of cases.

Discussion/Conclusion: Utilising different techniques of elevation of the articular joint impaction leads to joint preservation with satisfactory overall functional results. Secondary collapse was noted in 25.8% of the patients predisposing to a poorer outcome.