Metal ion concentrations following metal on metal hip resurfacing arthroplasty remain a concern. Variables associated with increased metal ion concentrations need to be established. This study provides metal ion data from a consecutive cohort of the first 76 patients implanted with a fourth generation hip resurfacing prosthesis.

All patients agreed to post-operative blood metal ion sampling at a minimum of one year. Post-operative radiographic measurements of cup inclination and anteversion were obtained using the EBRA software. Mean whole blood chromium (Cr) and cobalt (Co) concentrations in patients receiving the smallest femoral implants (Ł51mm) were greater than in the patients implanted with the largest prostheses (ł53mm) by a factor of 3 and 9 respectively. Ion concentrations in the small femoral group were significantly related to acetabular inclination (R=0.439, P< 0.001 for Cr, R=0.372, P=0.004 for Co) and anteversion (R=0.330, P=0.010 for Cr, R=0.338, P=0.008 for Co). This relationship was not significant in the large implant group. Mean Cr and Co concentrations in patients with accurately orientated cups (inclination < 45°, anteversion < 20°) were 3.7μg/l and 1.8 μg/l respectively, compared to 9.1μg/l and 17.5μg/l in malaligned cups.

A reduced surface contact area caused by cup malalignment may increase contact stresses, resulting in a high wear rate if fluid film lubrication is inadequate. Improved fluid film lubrication has previously been found in larger heads in vitro. Accurate acetabular component positioning is essential in order to reduce metal ion concentrations following hip resurfacing.

National Institute for Clinical Excellence (NICE) guidelines on venous thromboembolic (VTE) prophylaxis for patients undergoing orthopaedic surgery recommend that all inpatients be offered a low molecular weight heparin (LMWH).

Linked hospital episode statistics of 219602 patients were examined to determine the rates of complications following lower limb arthroplasty for the 12-month periods prior to and following the publication of these guidelines. This was compared with data from the National Joint Register (England and Wales) regarding LMWH usage during the same periods.

There was a significant increase in the reported use of LMWH (59.5 to 67.6%, p< 0.01) between the two periods. However, 90-day VTE events increased following both total hip (THR, 1.67% to 1.84%, p=0.06) and knee replacement (TKR, 1.99% to 2.04%, p=0.60). 30-day return to theatre rate for infection fell following TKR, but increased after THR. In addition, there were increases in rates of thrombocytopenia, which was significant following THR (p=0.03).

Recommendations from NICE are based on predicted reductions in VTE events, reducing morbidity, mortality and costs to the National Health Service. Early results in orthopaedic patients are unable to support these predictions.

Background: Calcaneal osteotomy is performed commonly as an adjunct to many corrective procedures of the abnormal hindfoot. Preservation of the hindfoot joints restores the normal biomechanics and can potentially delay arthritic changes in adjacent joints. Calcaneal osteotomy improves the weight bearing alignment of the foot by reducing varus or valgus deformity without impairing subtalar or mid-tarsal joint function. We are unaware of any studies documenting the complication rates associated with this procedure.

Methods: 36 calcaneal osteotomies (medial and lateral displacement, and Dwyer) were performed on 35 patients between April 2005 and October 2007 by the senior surgeon. Data was collected retrospectively by review of casenotes and assessment of radiographs. Average age was 54 years (range 18 to 81) and mean time of follow-up was 22 months (6 to 36). Indications were varus OA deformity (40%), Posterior tibialis tendon deficiency (30%), Charcot-Marie-Tooth (12%) and pes cavus (17%).

Results: All case notes and radiographs were available for analysis. Eight patients (22%) developed a complication. One patients (5%) had failed to fuse at 6 weeks following surgery. This patients developed a non-union and required re-fusion with bone grafting. Two patients (10%) had sural nerve damage, which persisted and required specialist pain team involvement. Two patients developed symptoms relating to prominent screws. A further two patients had wound breakdown and one had a superficial infection. In total, there were five further procedures (14%) – two directly related to problems with the calcaneal osteotomy. All osteotomies united within a translation distance of 10% in the sagittal plane.

Discussion: Calcaneal osteotomy is a useful adjunct procedure for correcting anatomical malalignment of the hindfoot in several conditions, with an acceptable complication rate and a low re-operation rate.

Background: There are no large comparative metal ion studies of commercially available hip resurfacing devices which have taken into account the effects of femoral size and cup inclination and anteversion.

Patients and methods: Metal ion analysis is carried out routinely at our independent centre. We present the metal ion results of 95 unilateral ASR patients and 70 unilateral BHR patients. For all patients, acetabular cup orientation was assessed using EBRA software. Patients with other metallic implants and those within 12 months of surgery were excluded.

Results: Whole blood/serum chromium (Cr) and cobalt (Co) concentrations were inversely related to femoral component size in both the ASR and BHR group (p< 0.05). Cr and Co levels were only seen to increase in the BHR group when the cup was implanted with an inclination greater than 55°. A significant relationship was identifed between the anteversion of the BHR cup and Cr and Co (p< 0.05 for Co, Spearman Rank correlation), with an increase in ions observed at anteversion angles > 17°. Cr and Co were more strongly influenced by cup position in the case of the ASR, with an increase in metal ions observed at inclinations greater than 45° and anteversion angles of < 10° and > 20°.

Discussion: The increased tolerance of the BHR cup to inclinations between 45–55° is likely due to the larger BHR cup providing greater protection against edge loading. When the cohort was divided by gender, the median Cr concentrations of the male ASR patients were significantly lower than those of the BHR males (p< 0.001). This suggests that in larger components positioned at more satisfactory angles of inclination and anteversion, the lower clearance of the ASR proves more significant than the extra coverage provided by the BHR cup. The BHR appears to be more sensitive to changes in anteversion than inclination.

Background: There is a paucity of published literature with regard to metal ion levels following bilateral hip resurfacings.

Method: Recent research has identified femoral component size and acetabular cup anteversion and inclination as important variables involved in metal ion release into the blood. We compared 13 patients with bilateral joints resurfaced using the ASR and 11 patients with bilateral BHRs to those with unilateral joints of similar size and cup inclinations/anteversions. Patients were excluded if the last procedure was within 12 months of blood sampling and if they had other metallic implants. Analysis of standing radiographs to determine cup orientation was carried out using EBRA software. Blood samples were analysed using ICPMS.

Results: Median whole blood Cr and Co values were higher in the BHR bilateral group when compared to the unilateral BHR group by a factor of 1.12 and 1.24 respectively. (5.17 vs 4.59 for Cr, 2.40 vs 1.93 for Co). The difference was significant for Co (p=0.030) but not for Cr (p=0.136). For the large ASR joints (53mm), median Cr and Co values were higher in the bilateral group by a factor of 1.5 and 1.85 respectively. (4.55 vs 2.97 (Cr) 2.83 vs 1.53 (Co)). The difference was significant for both Cr (p=0.001) and Co (p=0.022). For the small ASR joints (< 53mm), median Cr Co values were higher in the bilateral group by a factor of 1.95 and 2.30 respectively. (8.29 vs 4.25 (Cr), 6.78 vs 2.94 (Co)) (p=0.019 Co) (p=0.007 Co).

Conclusion: Metal ion concentrations are significantly greater in patients with bilateral resurfacings. The Cr Co concentrations observed in our patients with bilateral small ASR joints are double those in the published literature on bilateral 28mm metal on metal(MoM) joints implying that the lubrication achieved by small ASRs is sub optimal.

In our independent centre, in the period from January 2003 to august 2008, over 1100 36mm MoM THRs have been implanted as well as 155 Birmingham Hip Resurfacing procedures, 402 ASR resurfacings and 75 THRs using ASR XL heads on SROM stems.

During this period we have experienced a number of failures with patients complaining of worsening groin pain at varying lengths of time post operatively. Aspiration of the hip joints yielded a large sterile effusion on each occasion. At revision, there were copious amounts of green grey fluid with varying degrees of necrosis. There were 11 failures of this nature in patients with ASR implants (10 females) and 2 in the 36 MoM THR group (one male one female).

Tissue specimens from revision surgery showed varying degrees of ‘ALVAL’ as well as consistently high numbers of histiocytes. Metal debris was also a common finding.

A fuller examination of our ASR cohort as a whole has shown that smaller components placed with inclinations > 45° and anteversions < 10 or > 20° are associated with increased metal ion levels. The 11 ASR failed joints were all sub optimally positioned (by the above definition), small components.

Explant analysis using a coordinate measuring machine and out of roundness device confirmed greater than expected wear of each component. The lower number of failures in the 36mm MoM group, as well as the equal sex incidence, suggests that the majority of these failures are due to the instigation of an immune reaction by large amounts of wear debris rather than adverse reactions to well functioning joints. It is likely that small malpositioned ASRs function in mixed to boundary lubrication, and this, combined with the larger radius of these joints compared to the 36mm MoM joints, results in more rapid wear.

Introduction: Excellent medium term results have been reported with the BHR hip resurfacing implant. A number of modifications have been made to the latest designs in an attempt to preserve acetabular bone stock, improve function and prolong survival. We present the clinical and radiological results from the first independent series of ASR resurfacings.

Methods: The first consecutive series of 214 ASR hip resurfacings (192 patients) were followed up prospectively. No patients were lost to follow-up. The mean age of patients at implantation was 56 years and 40% were female. All patients had pre- and 2-year post-operative Harris Hip Scores (HHS) and UCLA activity scores. Radiographic and implant survival analysis was performed at 24–54 months following implantation.

Results: One hundred and seventy-three hips (87%) had an excellent Harris Hip Score (90 or above). Mean postoperative UCLA activity score was 7 and 92% were highly satisfied with the outcome. There were eleven revisions (5.1%). Four (1.9%) had femoral neck fractures (three had a femoral neck notch), two (0.9%) collapsed secondary to avascular necrosis and five (2.3%) were revised because of ongoing pain, as a result of metal wear debris.

Discussion: Although the fracture rate is similar to reports in the literature, the overall revision rate was higher. Rates of wear debris-related failure is concerning. Further investigation of specific implant failure is necessary.

Introduction: There are ongoing concerns regarding metal wear debris following the use of metal-on-metal (MonM) bearings for hip surface and total arthroplasty. A Type IV Hypersensitivity reaction to MonM articulations has previously been identified (aseptic lymphocyte dominated vasculitis associated lesion, ALVAL) but little is known of its incidence, diagnosis or management. Persisting groin pain in MonM patients may be undiagnosed ALVAL. At our single centre we have reviewed and compared three types of MonM articulations to examine the incidence of ALVAL and to identify trends.

Methods: The resurfacing group comprised 250 patients with the ASR prosthesis. In the resurfacing hybrid total hip replacement (THR) group there were 86 patients implanted with an ASR head on a stem. The final group comprised of 625 patients with a MonM THR using a 36mm Pinnacle head. Both the S-ROM and the Corail stems were used in the THR groups. Patients with persisting and activity-restricting groin pain had tests for infection. Patients were counselled and revision was offered if ALVAL was suspected from the clinical picture, blood results and the aspiration result. Specimens for microbiological and histological analysis were taken at the time of revision.

Results: We found 5 cases of histologically proven ALVAL in the absence of infection in 961 patients. The incidence was: 1.2% in the resurfacing group, 2.3% of Resurfacing Hybrid THR group and 0 in the 36 mm THR group. All 5 cases were in female patients. Only 1 case had any radiological abnormality. One patient was initially revised from a resurfacing to a 36mm MonM THR without clinical success. All patients have now been revised to ceramic-on-ceramic bearings with improvements in outcome.

Discussion: ALVAL may be under-diagnosed. The 5 patients we describe showed good clinical recovery following their primary procedure. However, activity levels decreased and pain increased at 6–12 months post-op. All described non-specific systemic symptoms. On examination, a painful straight leg raise was a characteristic finding. This may result from the significant effusion found around the hip at each revision. Fluid aspirated from these hips was of a characteristic colour (green grey) and viscosity. The failure of the revision of a resurfacing to a smaller MonM bearing highlights the problem of sensitisation to the metal debris. Any subsequent revision to a MonM bearing is unlikely to improve clinical outcome. This finding is consistent with previous reports in the literature. Our results suggest the incidence of ALVAL may be higher that previously thought. We suggest all patients with significant groin pain should have inflammatory markers tests and a hip aspiration performed. In the absence of infection, revision to an alternative bearing surface may be indicated.

Introduction: Potential problems resulting from metal-on-metal hip wear debris are well known. Previous studies have shown an association between high cup angles and raised metal ion levels, but a link to clinical outcome has yet to be established. We aim to show the relationship between high cup angles, raised metal ion levels and pain following hip resurfacing.

Methods: This analysis comprised the first 250 Depuy ASR hip resurfacings performed by a single surgeon (senior author) over a 3 yr period at an independent centre. Patients were followed up, examined and x-rayed at regular intervals. We measured Harris Hip Score (HHS) and pain. The acetabular cup inclination angles were measured from standardised pelvic radiographs. A subgroup of 80 patients had serum and whole blood chromium and cobalt measurements performed. This subgroup comprised patients with a similar sex split, age, activity level, follow-up and cup angle profile to the parent group.

Results: HHS improved from 51.6 pre-operatively to 94.6 post-operatively. Males had a significantly higher post-op HHS (97.1) compared with the females (91.0). 2.1% of male patients had pain compared with 8.7% of females. High cup angles were associated with pain in females. This relationship did not occur in males. In patients with cup angles of 48° and above there were no males with pain compared to 15.4% of females. Females under 48° had a HHS of 93.7 compared to 88.0 for those over 48°. When we analysed metal ion levels there was a similar relationship. Patients with cup angles of 48° and above had significantly higher serum and whole blood chromium and cobalt levels compared with lower cup angles. Three patients with cup angles over 50° developed ALVAL (aseptic lymphocyte dominated vasculitis associated lesion) based on histological findings. All were female.

Discussion: High cup angles are associated with increased pain and elevated metal ion levels. Women seem to be more intolerant of an higher cup angle than men. This may be a consequence of the smaller prostheses in females. Cups implanted lower than 48° had a better clinical outcome and less metal ion wear. Like other 4th generation designs, the ASR cup is not a complete hemisphere (unlike the BHR) and may be susceptible to edge loading at lower inclination angles than previously thought. We believe the current recommendation of 45° +/−5° is too high based on our findings. We recommend an inclination angle that does not exceed 48°.

Optimal cup orientation for metal-on-metal hip resurfacing has yet to be established. Guidance is based on hip replacement data and in vitro studies. We sought to determine the influence of component size and positioning on early clinical outcome.

This study comprises a consecutive series of 200 hip resurfacings. All had Harris Hip Scores (HHS) at one-year review. Acetabular inclination angles were measured on pre-operative radiographs, and cup inclination/anteversion angles on 3-month post-operative films using EBRA. Restoration of anatomy was defined as placement of the cup within +/−5 degrees of pre-operative inclination. The difference between pre-operative acetabular and post-operative cup inclination was termed cup-angle difference (CAD).

HHS inversely correlated with CAD (P=0.023) and anteversion (P=0.003), and directly correlated with femoral head size (P< 0.001). In patients with restoration of inclination anatomy mean HHS at one year was significantly higher at 98.7 compared with cups placed outside the normal anatomy restoration limits (93.8, P=0.003). Patients with anteversion > 20 degrees had a significantly lower HHS (P=0.010) compared with cups anteverted < 20 degrees. 96% of patients with HHS < 90 had malaligned cups (inclination over 45 degrees, anteversion over 20 degrees).

Restoring pre-operative cup inclination, anteverting the cup < 20 degrees and using large femoral heads improves early clinical outcome following MonM hip resurfacing. We recommend accurate pre-operative planning and meticulous attention to intra-operative cup positioning with these results in mind.

Resurfacing metal-on-metal hip arthroplasty is currently showing promising clinical results. However there are concerns related to such implants, including the elevated levels of metal ions typically seen in patients. Valuable data can be obtained from explanted prostheses but due to their recent introduction few retrieval studies on resurfacing hip prostheses have been published.

Five ASR hip resurfacing prostheses were revised due to pain. From two patients, head and cup were available for independent explant analysis. In the other three cases only femoral components were available. All were removed from female patients and all were revised to ceramic-on-ceramic hip prostheses. Post-operative radiographic measurements of cup inclination and ante-version were obtained using the EBRA software. The surface roughness values of the articulating surfaces of the explants were measured using a non-contacting profilometer. A co-ordinate measuring machine was used to measure the diameter of the head and the cup and thus the diametral clearance. The same measurements were then taken from a new unused ASR prosthesis and compared. Using elastohydrodynamic theory the minimum effective film thickness of the implant was calculated. In turn this allowed the lubrication regime to be determined.

The average roughness values of the head and the cup of one implant were found to be 0.135microns and 0.058microns respectively, with a diametral clearance of 110microns. These results indicated that, at the time of removal, the prosthesis would have operated in the boundary lubrication regime. Other explants showed evidence of localised contact between the head and the rim of the acetabular cup, and these showed articulating surfaces with typical roughness values of between 0.025microns and 0.050microns. The new ASR had head and cup surface roughness values of 0.010microns and 0.012microns respectively and a diametral clearance of 87microns, implying that a new implant would operate under fluid film lubrication. All cups five were implanted with inclination angles over 45 degrees and anteversion over 25 degrees.

These results suggest that components with high inclination and anteversion angles display greater than expected wear and may operate in boundary rather than fluid film lubrication which may eventually lead to early failure.

Introduction: Patient selection has been critical to the excellent medium-term clinical results following hip resurfacing. Hypersensivity to metal ion debris has been described in previous generations of metal-on-metal bearings. This may also be a problem that affects modern designs. Characteristic histological changes have been identified (ALVAL). There are few studies that include large female numbers, and show separate outcome and implant survival.

Methods: Eighty-one female hips at a mean of 23 months (11–43) had an ASR hip resurfacing procedure at a single-surgeon independent centre. Mean age was 55 years (28–69). Harris Hip Scores (HHS) were recorded at one-year follow-up. Failures were analysed.

Results: HHS improved from 46.4 (11–77) to 90.2 (27–100). Overall, there was a 7.4 % revision rate. There were 3 femoral neck fractures. In the entire series of 98 female patients there were 3 cases of severe pain requiring revision (3.1%). All three patients had HHS < 50 at one year follow-up. Patients had groin pain, reduced flexion and a painful straight leg raise. Blood results were not suggestive of infection. Aspiration of the hip joint in each case revealed copious amounts of milky green grey aseptic fluid. All had similar macroscopic changes at revision. There were characteristic histological changes in keeping with ALVAL. All 3 patients were revised to THRs with ceramic bearings.

Discussion: The failure rate of 7.4% in the older female group is poor at this early stage following hip resurfacing. The incidence of metal hypersensitivity in our series suggests this complication may be more common than previously thought. Patients with persisting pain of unknown aetiology following resurfacing at other centres may have metal hypersensitivity.

Introduction: Hip resurfacing is a successful pain-relieving procedure which restores function in young patients. However, some patients have persisting pain. We suggest that load characteristics in relation to position of the cup may influence these symptoms. We aimed to determine the effect of acetabular cup inclination angle on pain following hip resurfacing.

Methods: 92 consecutive hips in 81 patients were resurfaced with the ASR prosthesis. The average age was 56.5 years (35–72). 33 were female hips. Harris Hip Scores (HHS) and UCLA activity scores were recorded pre-operatively and at last follow-up. Patient satisfaction was recorded. Acetabular cup inclination angle was measured. An acceptable angle for hip replacement is 45 degrees +/− 5 degrees. We therefore grouped cups into those above 50 degrees and those below. Average follow-up was 17.9 months (8–31). There were 39 hips with an angle less than 50 degrees (A), and 53 greater than 50 (B). Patients in each group were comparable for age, sex, follow-up and BMI.

Results: In group A HHS improved from 53.4 to 98.7 and UCLA activity score improved from 4.2 to 7.5. All patients were extremely or very pleased. In group B HHS improved from 49.0 to 94.0 and UCLA activity score improved from 3.9 to 7.1. 48 of 53 patients were extremely or very pleased. At follow up 37 of 39 (95%) of patients in group A had no pain. In group B 35 of 53 had no pain (66%). This is a statistically significant difference when analysed with Fisher’s exact test (p< 0.05).

Discussion: This study shows that an excessively open acetabular cup may contribute to persisting pain and patient dissatisfaction. This may be a result of excessive eccentric wear and metal ion deposition, and may lead to early failure of the prosthesis.

Introduction: Traditionally, hip resurfacing has been performed in younger patients. We compared the early results of a single surgeon series of ASR resurfacings performed in male patients in this age group with men over 60 years old.

Methods: 114 consecutive procedures were performed in male patients. Group 1 consisted of 48 hips in 43 patients aged 60 years and over (average age 64.2, range 60 to 73). Group 2 consisted of 66 hips in 59 male patients aged below 60 years (average age 50.4, range 31–59). Patients were followed up at a mean of 17.1 months in group 1 and 19.4 in group 2. BMI, ASA grade and proportion of Charnley walking grade A patients was similar.

Results: In group 1, average HHS improved from 56.4 to 98.6 and in group 2 from 54.2 to 96.7. Average UCLA activity score improved from 4.3 to 7.2 in group 1 and 4.1 to 7.7 in group 2. There has been 1 revision for neck fracture in group 1 (neck notched at time of primary procedure). There were no revisions in group 2. All of the patients in group 1, and 57 of 59 patients in group 2, give a high satisfaction rating. In group 1, one radiograph demonstrates lucency surrounding the ace-tabular component. This patient is asymptomatic with a HHS of 100 and a UCLA activity score of 10. There are areas of incomplete lucency around the components of a further 8 hips in group 1 and 10 in group 2. There has been no migration of components in either group.

Discussion: Functional outcome in patients over 60 years appears to be similar to younger patients. The early results are encouraging; we will continue to offer this procedure to active patients over 60. The areas of lucency on the radiographs will need careful follow-up to determine the long-term significance of these changes.

This paper considers the new financial infrastructure of the National Health Service and provides a resource for orthopaedic surgeons. We describe the importance of accurate documentation and data collection for National Health Service hospital Trust finances and league tables, and support our discussion with examples drawn from our local audit work.

Introduction Smaller skin incisions during a minimally invasive approach to total hip arthroplasty may accelerate rehabilitation and reduce inpatient stay. Cutaneous nerve injury from a standard 20cm lateral approach was compared with a new, oblique minimally invasive 10cm incision.

Method The two surgical approaches were defined on fifteen cadaveric thighs. Cutaneous nerves lying deep to the incisions were dissected out. Projected nerve injury resulting from each approach was recorded.

Results The mean number of nerves divided by a standard approach was 5.0 compared with 4.1 in the minimally invasive approach (mean difference 0.87, 95% confidence interval 0.03 to 1.7, P=0.043). However, the mean number of nerves per cm divided by the standard approach was 0.25 compared with 0.41 by the minimally invasive (mean difference −0.163, 95% confidence interval −0.09 to −0.24, P< 0.001).

Discussion The oblique incision ran perpendicular to the underlying cutaneous nerves; therefore, more cutaneous nerves were divided per cm than a standard approach. A 10cm oblique incision divides as many nerves as a 16cm standard approach.