Objectives

We investigated the reliability of the cobalt-chromium (CoCr) synovial joint fluid ratio (JFR) in identifying the presence of a severe aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL) response and/or suboptimal taper performance (SOTP) following metal-on-metal (MoM) hip arthroplasty. We then examined the possibility that the CoCr JFR may influence the serum partitioning of Co and Cr.

Objectives

We have encountered patients who developed large joint fluid collections with massive elevations in chromium (Cr) and cobalt (Co) concentrations following metal-on-metal (MoM) hip arthroplasties. In some cases, retrieval analysis determined that these ion concentrations could not be explained simply by the wear rates of the components. We hypothesized that these effects may be associated with aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL).

Objectives

Wear debris released from bearing surfaces has been shown to provoke negative immune responses in the recipient. Excessive wear has been linked to early failure of prostheses. Analysis using coordinate measuring machines (CMMs) can provide estimates of total volumetric material loss of explanted prostheses and can help to understand device failure. The accuracy of volumetric testing has been debated, with some investigators stating that only protocols involving hundreds of thousands of measurement points are sufficient. We looked to examine this assumption and to apply the findings to the clinical arena.

Objectives

The aims of this piece of work were to: 1) record the background concentrations of blood chromium (Cr) and cobalt (Co) concentrations in a large group of subjects; 2) to compare blood/serum Cr and Co concentrations with retrieved metal-on-metal (MoM) hip resurfacings; 3) to examine the distribution of Co and Cr in the serum and whole blood of patients with MoM hip arthroplasties; and 4) to further understand the partitioning of metal ions between the serum and whole blood fractions.

Objectives

An ongoing prospective study to investigate failing metal-on-metal hip prostheses was commenced at our centre in 2008. We report on the results of the analysis of the first consecutive 126 failed mated total hip prostheses from a single manufacturer.

Introduction: One of the latest groups of replacement hip joints are known as hip resurfacings and they consist of a relatively large diameter femoral head articulating within a thin acetabular cup. Many of these devices show good short to medium term clinical results. However there are concerns over such implants including fracture of the femur and possible wear debris related reactions. Much valuable data can be learnt from explanted prostheses which have ‘failed’ and then been removed from patients. As hip resurfacing prostheses have only recently been introduced, there are relatively few such retrieval studies.

Methods and materials: Nineteen femoral and acetabular components from metal-on-metal hip resurfacing prostheses were obtained at revision operations. There were eight patients who had femoral fractures and the remainder experienced worsening groin pain and a characteristic sterile effusion. There were eleven head components and four pairs of matching heads and cups. Each of these was examined using a Zeiss TSK Rond-com60A roundness measuring machine and a Mitutoyo LEGEX co-ordinate measuring machine (CMM). Out of roundness measurements were taken on three planes for each acetabular and femoral component. The CMM was used to obtain 12 traces at 30° intervals for each acetabular and femoral component, allowing areas of localised wear to be identified and the maximum wear depth to be quantified.

Results: The maximum out of roundness values for the nineteen components ranged from 1.8 to 91.8 microns. A similar range of values was obtained from the CMM results. From the paired components, out of roundness was greater in the head than in the cup. All eight femoral heads which were retrieved after fracture of the femur showed out of roundness of less than 5 microns.

Discussion: Both out of roundness measurements and those from the CMM provided information about the wear of the implants. For a new component, a typical out of roundness value would be no greater than 5 microns. Therefore, from the out of roundness values it was seen that the eight ‘fracture’ components showed minimal distortion or wear after removal. In contrast the remaining components, which had a minimum out of roundness of 15 microns, showed much greater wear, thus suggesting that the groin pain was associated with relatively large volumes of wear debris. CMM scans helped to identify localised areas of wear and maximum wear depths. Values in the range of < 2 microns to 164 microns have been reported previously and show good agreement with the findings of this study. Retrieved components which had been implanted at high angles of inclination and anteversion tended to show the greatest wear, implying that correct positioning in vivo is crucial to the longevity of hip resurfacing prostheses.

Introduction: The return of haemoglobin (Hb) to preoperative levels at 1–6 months following elective lower limb joint arthroplasty is well documented. Previous reports have suggested in healthy, elective patients there is no significant improvement in Hb levels following iron supplementation compared with placebo. There may also be unpleasant side effects. However, there is little published on this topic in the elderly population who suffer a femoral neck fracture and undergo emergency surgery, and often have poorer iron reserves.

Methods: We examined the blood results and discharge prescriptions of consecutive patients who underwent femoral neck fracture surgery at our institute in a 12 month period. Patients who had received a blood transfusion were excluded. 82 patients remained. Normal Hb levels at the time of surgery and 1–6 months post-operatively (late Hb) were collected.

Results: Thirteen patients (16%) were prescribed iron supplementation on discharge. No patients who went on to receive iron had a normal Hb (11.5 – 15.5g/dL in females, 13– 8g/dL in males) immediately following surgery (mean Hb 9.17g/dL) compared with 26% (mean Hb 10.41g/dL) in those who received no iron. At 115.2 days (range 28–284) following surgery 88.9% of patients prescribed iron had a normal Hb compared with only 48.1% of those who received no treatment (P=0.0167).

Discussion: The low level of iron prescribing was surprising, and may be the result of published evidence in elective patients. Our numbers are small, but we show a statistically significant difference which warrants further investigation. We suggest that, unlike the younger, healthier elective arthroplasty patients, femoral neck fracture patients may benefit from dietary iron supplement.

Introduction: Payment by results was introduced into the NHS in an effort to finance Trusts fairly and reward good performance. Tariffs for a single patient episode are derived from diagnosis and procedure codes, comorbidities, patient age, and length of stay. Poor data collection can result in a lower tariff with subsequent under billing of the Primary Care Trust (PCT). In addition, an individual surgeon’s performance in future comparison league tables will rely on the accuracy of this data. Methods of documentation and data collection vary in different units. We evaluated the methods and the resulting tariffs in 2 units in the Northern Deanery.

Methods: Case notes were examined for 20 consecutive orthopaedic patients discharged from unit A, and 20 from unit B. The case mix in the two groups was similar. A correct tariff based on case notes was compared with the actual tariff used to bill the PCT for each patient. The coding department derived actual tariffs from data in electronic discharge summaries created by ward based junior medical staff in unit A. Accurately completed typed case notes were available to coders in unit B.

Results: Only 3 of the 20 tariffs (15%) were correct for unit A patients. This represented a total financial loss to the trust of £14892 (25% of total revenue). In unit B, 19 of 20 (95%) tariffs were correct. An error in the coding for one procedure resulted in a higher tariff being assigned to a patient (total gain of £486, < 1%).

Discussion: Orthopaedic departments create large Trust revenue. Accurate documentation and information transfer for coding is essential for payment by results to function correctly. Trusts which fail to do this will be financially penalised and surgeon league tables may not adequately reflect individual case complexity. We recommend all Trusts use the model established in unit B.