Heterotopic ossification (HO) is the formation of bone at extra-skeletal sites. Genetic diseases, traumatic injuries, or severe burns can induce this pathological condition and can lead to severe immobility. While the mechanisms by which the bony lesions arise are not completely understood, intense inflammation associated with musculoskeletal injury and/or highly invasive orthopaedic surgery is thought to induce HO. The incidence of HO has been reported between 3% and 90% following total hip arthroplasty. While the vast majority of these cases are asymptomatic, some patients will present decreased range of motion and painful swelling around the affected joints leading to severe immobility. In severe cases, ectopic bone formation may be involved in implant failure, leading to costly and painful revision surgery. The effects of surgical-related intraoperative risk factors for the formation of HO can also play a role.

Prophylactic radiation therapy, and anti-inflammatory and biphosphonates agents have shown some promise in preventing HO, but their effects are mild to moderate at best and can be complicated with adverse effects. Irradiation around surgery could decrease the incidence of HO. However, high costs and the risk of soft tissue sarcoma inhibit the use of irradiation. Increased trials have demonstrated that nonsteroidal anti-inflammatory drugs (NSAID) are effective for the prevention of HO. However, the risk of gastrointestinal side effects caused by NSAID has drawn the attention of surgeons. The effect of the selective COX-2 inhibitor, celecoxib, is associated with a significant reduction in the incidence of HO in patients undergoing THA. Bone morphogenetic proteins (BMP) such as BMP2 identified another novel druggable target, i.e., the remote application of apyrase (ATP hydrolyzing agent) in the burn site decreased HO formation and mitigated functional impairment later. The question is if apyrase can be safely administered through other, such as systematical, routes. While the systemic treatments have shown general efficacy and are used clinically, there may be great benefit obtained from more localised treatment or from more targeted inhibitors of osteogenesis or chondrogenesis.

In the surgical setting, prophylaxis for HO is regularly indicated due to the considerable risk of functional impairment. Heterotopic ossification is a well-known complication of total hip arthroplasty, especially when the direct lateral approach is used. Possible intraoperative risks are the size of incision, approach, duration of surgery and gender that can be associated with higher rates of HO or increase of the severity of HO. Like inflammation and tissue damage/ischemia are likely to be the key in the formation of HO, kindness to the soft tissues, tissue preserving surgery, pulse lavage to remove bone inducing factors and avoiding damage to all tissues should be erased as a comorbidity. Incision length, tissue dissection and subsequent localised trauma and ischemia, blood loss, anesthetic type and length of surgery may all contribute to the local inflammatory response. Data suggest that the surgeon may control the extent and nature of HO formation by limiting the incision length and if possible the length of the operation.

Currently resection of HO is generally suggested after complete maturation (between 14–18 months), since earlier intervention is thought to predispose to recurrence. Reliable indicators of maturation of HO are diminishing activity on serial bone scans and/or decreasing levels of alkaline phosphatase. Although usually asymptomatic, heterotopic bone formation can cause major disability consisting of pain and a decreased range of motion in up to 7% of patients undergoing THA. Patients benefit from early resection of the heterotopic ossification with a proper and reliable postoperative strategy to prevent recurrence of HO with clinical implications.

Since the market withdrawal of the ASR hip resurfacing in August 2010 because of a higher than expected revision rate as reported in the Australian Joint Replacement Registry (AOAJRR), metal-on-metal hip resurfacing arthroplasty (MoMHRA) has become a controversial procedure for hip replacement. Failures related to destructive adverse local tissue reactions (ALTR) to metal wear debris have further discredited MoMHRA. Longer term series from experienced resurfacing specialists, however, demonstrate good outcomes with excellent 10- to 15-year survivorship in young and active men. Besides, all hip replacement registries report significantly worse survivorship of total hip arthroplasty (THA) in patients under 50 compared to older ages. The triad of a well-designed device, implanted accurately, in the correct patient has never been more critical than with MoMHRA implants.

The surgical objectives of MoMHRA were to preserve bone stock, maintain normal anatomy and mechanics of the hip joint and to approximate the normal stress transmission to the supporting femoral bone. The functional objectives were better sports participation, less thigh pain and limp, less perception of a leg length difference and a greater perception of a normal hip. Cobb reported that patients with MoMHRA were able to walk faster and with more normal stride length than patients with well performing hip replacements. They also show that function following hip replacement is very good, with high satisfaction rates, but the use of a patient centered outcome measure (PCOM), and objective measures of function reveal substantial inferiority of THA over MoMHRA in two well-matched groups. When coupled with the very strong data regarding life expectancy and infection, this functional data makes a compelling case for the use of resurfacing in active adults.

Recent studies show a possible increase in life expectancy with MoMHRA. Compared with uncemented and cemented total hip replacements, Birmingham hip resurfacing has a significantly lower risk of death in men of all ages. McMinn's investigations additionally suggest a potentially higher mortality rate with cemented total hip replacements. These results have now been confirmed by other centers as well, and confirm that those undergoing MoMHRA have reduced mortality in the long term (up to 10 years) compared with those undergoing THA and that this difference persisted after extensive adjustment for confounding factors.

Early revisions were often due to fracture of the femoral neck while later revisions are associated with loosening and/or ALTR to wear debris. In some studies, revisions of MoMHRA with ALTR have been complicated by an increased risk of re-revision and poor outcome. Component malpositioning is the most common cause of MoMHRA failure. Metal ion measurements are an excellent tool to detect wear at an early stage. The revision analysis highlights the importance of surgical experience, indications and prosthesis design. Use of ion levels, big THA-heads and patient education/compliance were identified as factors improving outcome following MoMHRA revision.

Today's MoMHRA is conservative to the bone. It is the first implant that proves decrease of wear in time, disappearance of wear in longer term with a possible life time survival of the implant, this unrelated to the activity of the patient. If following an international consensus, the right implant is used, with a perfect technique in the right patient, all benefits exceed the problems described in the past.

Background

Reasons for revision of metal-on-metal hip resurfacing arthroplasty (MoMHRA) have evolved with improving surgical experience and techniques. Early revisions were often due to fracture of the femoral neck while later revisions are associated with loosening and/or adverse local tissue reactions (ALTR) to wear debris. In some studies, revisions of MoMHRA with ALTR have been complicated by an increased risk of rerevision and poor outcome. The purpose of this study was to investigate the causes of failure and to identify factors that improve outcome following revision of a failed HRA.

Background and aim

Arthroplasty registries and consecutive series indicate significantly worse results of conventional metal-on-polyethylene total hip arthroplasty (THA) in patients younger than 50 years compared to older patients, with inferior clinical outcomes and 10-year survivorship ranging between 70 and 90%. At our institution, patients under 50 needing a THA receive either a metal-on-metal hip resurfacing (MoMHRA) or a ceramic-on-ceramic (CoC)THA. In order to evaluate the outcome of these options at minimum 10 years, we conducted a retrospective review of all MoMHRA and CoCTHA with more than 10 years follow-up implanted in patients under 50.

Background and aim

Since the market withdrawal of the ASR hip resurfacing in August 2010 because of a higher than expected revision rate as reported in the Australian Joint Replacement Registry (AOAJRR), metal-on-metal hip resurfacing arthroplasty (MoMHRA) has become a controversial procedure for hip replacement. Failures related to destructive adverse local tissue reactions to metal wear debris have further discredited MoMHRA. Longer term series from experienced resurfacing specialists however, demonstrated good outcomes with excellent 10-to-15-year survivorship in young and active men. These results have recently been confirmed for some MoMHRA designs in the AOAJRR. Besides, all hip replacement registries report significantly worse survivorship of total hip arthroplasty (THA) in patients under 50 compared to older ages. The aim of this study was to review MoMHRA survivorship from the national registries reporting on hip resurfacing and determine the risk factors for revision in the different registries.

INTRODUCTION

Systemic levels of metal ions are surrogate markers of in-vivo wear of metal-on-metal hip resurfacings (MoMHRA). The wear-related generation of metal ions is associated with component size and positioning but also with design specific features such as coverage angle, clearance, metallurgy and surface technology.

Background:

Potential systemic toxicity of metal ions from metal-on-metal hip arthroplasties (MoMHA) is concerning. High blood cobalt (Co) levels have been associated with neurological, cardiac and thyroid dysfunctions.

Introduction

Metal-on-metal hip resurfacings (MoMHRAs) have a characteristic wear pattern initially characterised by a run-in period, followed by a lower-wear steady-state. The use of metal ions as surrogate markers of in-vivo wear is now recommended as a screening tool for the in-vivo performance of MoMHRAs. The aims of this retrospective study were to measure ion levels in MoMHRAs at different stages during the steady-state in order to study the evolution of wear at minimum 10 years postoperatively and describe factors that affect it.

A retrospective study was conducted to investigate the changes in metal ion levels in a consecutive series of Birmingham Hip Resurfacings (BHRs) at a minimum ten-year follow-up. We reviewed 250 BHRs implanted in 232 patients between 1998 and 2001. Implant survival, clinical outcome (Harris hip score), radiographs and serum chromium (Cr) and cobalt (Co) ion levels were assessed.

Of 232 patients, 18 were dead (five bilateral BHRs), 15 lost to follow-up and ten had been revised. The remaining 202 BHRs in 190 patients (136 men and 54 women; mean age at surgery 50.5 years (17 to 76)) were evaluated at a minimum follow-up of ten years (mean 10.8 years (10 to 13.6)). The overall implant survival at 13.2 years was 92.4% (95% confidence interval 90.8 to 94.0). The mean Harris hip score was 97.7 (median 100; 65 to 100). Median and mean ion levels were low for unilateral resurfacings (Cr: median 1.3 µg/l, mean 1.95 µg/l (< 0.5 to 16.2); Co: median 1.0 µg/l, mean 1.62 µg/l (< 0.5 to 17.3)) and bilateral resurfacings (Cr: median 3.2 µg/l, mean 3.46 µg/l (< 0.5 to 10.0); Co: median 2.3 µg/l, mean 2.66 µg/l (< 0.5 to 9.5)). In 80 unilateral BHRs with sequential ion measurements, Cr and Co levels were found to decrease significantly (p < 0.001) from the initial assessment at a median of six years (4 to 8) to the last assessment at a median of 11 years (9 to 13), with a mean reduction of 1.24 µg/l for Cr and 0.88 µg/l for Co. Three female patients had a > 2.5 µg/l increase of Co ions, associated with head sizes ≤ 50 mm, clinical symptoms and osteolysis. Overall, there was no significant difference in change of ion levels between genders (Cr, p = 0.845; Co, p = 0.310) or component sizes (Cr, p = 0.505; Co, p = 0.370). Higher acetabular component inclination angles correlated with greater change in ion levels (Cr, p = 0.013; Co, p = 0.002). Patients with increased ion levels had lower Harris hip scores (p = 0.038).

In conclusion, in well-functioning BHRs the metal ion levels decreased significantly at ten years. An increase > 2.5 µg/l was associated with poor function.

Cite this article: Bone Joint J 2013;95-B:1332–8.

INTRODUCTION

Metal-on-metal hip resurfacing (MoMHRA) requires a new standardized radiographic evaluation protocol. Evaluation of the acetabular component is similar to total hip arthroplasty but the femoral component requires different criteria since there is no component in the femoral canal and the metallic femoral implant overlies the junctions between bone-cement and cement-prosthesis. Lucencies around the metaphyseal HRA femoral stem can be described with the femoral zonal system into 3 peg-zones (Amstutz' et al) but this doesn't account for bony changes of the femoral neck away from the stem. This study proposes a new femoral zonal system for radiographic HRA assessment. We tested the efficacy of radiographs in identifying a problem by reviewing 711 radiographs of resurfaced hips and correlating radiographic features to outcome.

Introduction

Hip resurfacing (HRA) designer centres have reported survivorships between 88.5–96% at 12 years. Arthroplasty Registries (AR) reported less favourable results especially in females gender and small sizes. The aim of this study was to evaluate the minimum 10-year survival and outcome of the Birmingham Hip Resurfacing (BHR) from an independent specialist centre.

The surgical treatment of young adults with end-stage hip disease has been a challenge. Inferior THA survival in the young, perceived advantages of hip resurfacing versus THA and advancements in tribology, led to the introduction of 3rd generation Metal-on-Metal-Hip-Resurfacing-Arthroplasty (MoMHRA). To-date, thousands of such prostheses have been implanted worldwide in younger patients, yet little is known regarding long-term outcome. The only studies reporting greater than 10 year outcome come from designer centres with survivorship varying between 88.5–96% at 12 years. Arthroplasty Registries (AR) have reported less favourable survivorships with female gender and size having a negative effect on survival. In our independent hip resurfacing centre in Ghent, Belgium, a single surgeon has implanted more than 3500 HRA over more than 12 years. A cohort of 149 patients who received a Birmingham Hip Resurfacing (BHR) at a mean age of 50 years at surgery have now reached a minimum 10 years follow-up. The overall 12-year survival in these young adults is 93.1% (95% CI: 88.3–98.0), 99% in males and 87.3% in females. These survivorship data are superior to registry reported figures of THA amongst young patients and correspond well with previous reports from designer centres. The long-term survivorship and clinical outcome of the BHR are excellent in men, uninfluenced by preoperative diagnosis or age. However, survivorship in women is inferior and usually related to increased wear and reactions to metal debris.

Malpositioning of components with associated wear-induced soft tissue fluid collections is the most frequent factor leading to failure of a HRA. In our experience, mid-term outcome following revision is good and complication and re-revision rates can be low. Surgical experience, early intervention in cases of mal-positioned implants, clinical use of ion levels, implantation of larger ceramic-on-ceramic THA femoral heads and patient education are factors in improving outcome and reducing complication and re-revisions following HRA revision.

INTRODUCTION

Metal-on-metal hip resurfacing arthroplasty (MoMHRA) is a surgical option in the treatment of end-stage hip disease. The measurement of systemic levels of metal ions gives an insight into the wear occurring and is advocated by regulatory bodies as routine practice in the assessment of resurfaced hips. However, the acceptable upper levels of Chromium (Cr) and Cobalt (Co) ions concentration with clinical significance still have to be established. The aim of this study is to address this issue in unilateral and bilateral resurfaced hips.

Surface arthroplasty or resurfacing represents a significant development in the evolution of hip replacement. A hip resurfacing arthroplasty (HRA) is a bone conserving alternative to total hip arthroplasty (THA) that restores normal joint biomechanics and load transfer and ensures joint stability. Metal-on-metal (MoM) bearings have been preferred for these large diameter articulations because of their lower volumetric wear and smaller particulate debris compared to metal-on-poly-ethylene bearings. Of the many engineering factors which have contributed to the success of the MoM bearing, the metallurgy, diametral clearance, sphericity and surface finish were thought to be most important. More recently, adverse reactions to metal particles and ions generated by wear and corrosion of the metal surfaces have focused the attention on the importance of coverage angle and cup positioning. Currently, the scientific consensus is that cup coverage angle, diametral clearance and metallurgy have their importance in that order. Precise understanding of manufacturing variables is imperative in obtaining clinical consistency and safety in the patient. It is important to examine femoral fixation, bone remodelling, and wear of MoM implants. For the second and third generation MoM HRA various designs and biomaterials have been used. We have conducted a randomised, controlled trial comparing 9 different hip resurfacing prostheses. Clinical and radiographic outcome and whole blood, serum and urine metal ion levels are evaluated at 6 months, 1 year and 2 years in 180 patients with 9 different HRA designs and the differences are analyzed. Besides, the design quality of the 9 different metal-on-metal prostheses and their accessory instruments have been judged during the operation. The Durom with its Metasul history may claim a metallurgic advantage, and in combination with the highest coverage angle of all cups, it may be the best wear couple, as suggested by low ion measurements. However, as discussed above, an optimal bearing alone is not sufficient to achieve a successful hip resurfacing.

Introduction

Tribological studies have described a characteristic wear pattern of metal-on-metal hip resurfacings (MoMHRAs) with a run-in period followed by a ‘bedding-in’ phase minimising wear or by an increasing wear patch with edge loading. The use of metal ions as surrogate markers of in-vivo wear is now recommended as a screening tool for the performance of MoMHRAs. The aims of this retrospective, single-surgeon study were to measure ion levels in unilateral MoMHRAs at different stages during the steady-state in order to study the evolution of wear and factors affecting it.

Bearing diameter and acetabular component orientation have been shown to be important variables effecting blood metal ion levels following hip resurfacing arthroplasty. So far no studies on bilateral hip resurfacings have taken into account these variables.

We examined the serum ion results of patients under the care of two experienced hip resurfacing surgeons who carry out ion analysis as part of routine post operative care. Surgeon 1: Patients were implanted exclusively with a “third generation” resurfacing device. Surgeon 2: Patients were implanted with the same “third generation” device and also a low clearance “fourth generation” resurfacing device. Only ion results from patients who were 12 months post surgery were included. Bilateral patients were matched to unilateral patients according to the surgeon performing the operation; the resurfacing system implanted and cup inclination and anteversion angles. The ion data from each bilateral group was tested against the corresponding unilateral groups using the Mann Whitney U test for non parametric data. Significance was drawn at p<0.05.

Surgeon 1: There were 310 patients with unilateral joints and 50 with bilateral joints. There were no significant differences with regard to time to follow up, activity levels, joint sizes or cup orientations. Serum chromium (Cr) and cobalt (Co) concentrations were significantly greater in the bilateral group (p<0.001). Median ion levels were greater in the bilateral group by a factor of >2 in the smallest joint sizes and <2 in the largest joints. Surgeon 2: There were 11 patients with bilateral third generation resurfacing joints and 50 with unilateral joints of the same design. The same relationship as described above was identified. There was a notable difference in the fourth generation implant group (n=13 bilateral, n=100 unilateral). Median ion levels for patients receiving bilateral joints of sizes <47mm were ten times greater than in the corresponding unilateral group.

Bearing diameter and component design are critical factors in determining metal ion levels following bilateral hip resurfacings. Surgeons must consider the potential implications of gross increases in metal ion levels prior to performing bilateral hip resurfacings in smaller patients.

There have been many reports of metal ion levels measured in the bloodstream of patients after metal-on-metal hip replacement, and it is generally accepted that levels of cobalt (Co) and chromium (Cr) are elevated after these types of devices are implanted. However, it is not clear how to interpret these elevated levels; in particular what are the acceptable levels and what levels indicate that close monitoring of the patient is needed. Our aim was to establish the differences in metal ion levels between well functioning patients and those with clinical problems.

We measured serum Co and Cr levels (microgram’s per litre or μg/l) using inductively coupled plasma mass spectrometry with a well established collection protocol of all patients attending follow-up clinics. Our inclusion criteria for this study were all patients unilaterally implanted with a metal-on-metal hip resurfacing with no other metallic implant; patients were categorized as either A. Well Functioning or B. Clinically Problematic (pain, reduced function, reduced ROM, negative x-ray findings) and differences in ion levels between these two groups were examined. Well functioning patient data was only included if measurements were made more than 12 months post-operatively to avoid run-in wear levels. Abduction angle was also measured from x-rays of the pelvis, and the frontal plane coverage arc of each implanted cup calculated (De Haan JBJS[Br] 2008;90(10):1291–7). There were a total of 519 patients, with 358 in Group A and 161 in Group B; patients had a variety of devices with Birmingham Hip Resurfacing (64%) and Conserve Plus (29%) being the most commonly implanted. To establish a guideline upper ion level value for well functioning implants the upper 75th percentile values for Co and Cr levels for Group A patients having 15 mm or more coverage arc were calculated. The risk of having clinical problems was calculated as function of metal ion levels higher or lower than these upper limits.

The ion levels were significantly (Mann Whitney U p< 0.001) higher in Group B (mean [95% confidence intervals], Co 10.2 μg/l [5.9 to 14.5], Cr 10.3 μg/l [6.7 to 14.0]) compared to Group A (Co 2.3 μg/l [1.7 to 2.4], Cr 2.8 μg/l [2.3 to 3.4]). The well functioning upper limit for Co was 4.1 μg/l and for Cr was 5.2 μg/l. Metal ion levels greater than these upper limits were significantly (Chi-square p< 0.001) associated with the presence of clinical problems. The odds ratio for Co greater than 4.1 μg/l was 11.2 [95%CI 5.7 to 22.3] and that for Cr greater than 5.2 μg/l was 4.3 [95%CI 2.6 to 7.0].

There were significantly higher metal ion levels measured in patients with clinical problems after metal-on-metal hip resurfacing than those with well functioning hips. We have proposed upper acceptable limits for Co (4.1 μg/l) and Cr (5.2 μg/l) serum levels. Cobalt levels appear to be more reliable in predicting risk of clinical problems; levels greater than our proposed upper limit have 11 times the odds of developing clinical problems and patients with such levels should be followed closely.

Background: Definitive cup position for the reduction of blood metal ion levels has yet to be established.

Methods: Samples for serum metal ion analysis are taken routinely from patients under the care of the two senior authors of this paper. Both are high volume experienced hip resurfacing surgeons, one based in England, the other in Belgium. Metal ion results from two centres from patients with unilateral joints were correlated to size and orientation of femoral and acetabular components, UCLA activity score, age, time post surgery and post operative femoral head/neck ratios. EBRA software was used to assess cup inclination and anteversion on standing radiographs.

Cup orientation in vivo was compared to explant analysis of 60 retrieved resurfacing components using a coordinate measuring machine.

Results: Three resurfacing devices were studied. There were 620 results in total. Only femoral size and cup inclination/anteversion were found to have any effect on ion levels. In all devices, metal ion levels were inversely related to femoral size (p< 0.05). The device providing the smallest acetabular coverage arc was associated with the highest metal ion levels. Consistent throughout the implants, lowest ion levels were associated with cups with radiological inclination of 40–50° and anteversion 10–20°. Cup inclination angles lower than 40° were associated with posterior edge loading and likely sub-luxation of the femoral component.

Conclusion: The greater the coverage angle provided by the acetabular component, the greater the tolerance to suboptimal position. Lowest ion levels were found in well positioned lower clearance devices. Cup inclination/ante-version angles of 45/15+/−5° were associated with low ion levels in all three devices. We do not recommend cups to be placed with inclination angles below 40°.

Introduction: Avascular necrosis of the femoral head after resurfacing hip replacement is an important complication which may lead to fracture or failure. The surgical approach may affect the blood supply to the femoral head. We compared the changes in femoral head oxygenation resulting from the extended posterior approach to those resulting from the anterolateral approach, the trochanteric flip approach and a modified, soft tissue preserving posterior approach.

Methods: We recruited 48 patients who underwent hip resurfacing arthroplasty (HRA) to measure bone oxygen levels. A calibrated gas-sensitive electrode was inserted in the femoral head following division of the fascia lata. Intra-operative X-ray confirmed correct electrode placement. Base-line oxygen concentration levels were recorded immediately after electrode insertion and continuous measurements were then performed throughout surgery. All results were expressed relative to the baseline, which was considered as 100% relative oxygen concentration and changes during surgery through the posterior approach (n=10), the antero-lateral approach (n=12), the trochanteric flip approach (n=15) and the modified posterior approach (n=11) were compared.

Results: The relative oxygen concentration at the end of the procedure was significantly reduced when hip resurfacing was performed through the posterior (22%, SD 31%, p< 0.005) or a modified posterior (35%, SD 31%, p< 0.005) approach, but recovered in the anterolateral (123%, SD 99%, p=0.6) and trochanteric flip group (89%, SD 62%, p=0.5). Sub-group analysis of these two relatively blood preserving approaches showed that intra-operative oxygen concentration was significantly more consistent during surgery through the trochanteric flip approach (p< 0.02).

Discusssion and conclusion: This study has demonstrated that disruption of blood flow to the femoral head during HRA is dependent on the surgical approach. We therefore believe that blood supply preserving approaches (i.e. anterolateral, trochanteric flip) may be associated with a lower risk of avascular necrosis and femoral neck fracture.

We report the consensus of surgical opinions of an international faculty of expert metal-on-metal hip resurfacing surgeons, with a combined experience of over 18 000 cases, covering required experience, indications, surgical technique, rehabilitation and the management of problematic cases.

Introduction: A major concern with cemented hip resurfacing arthroplasty (HRA) femoral components is the thermal damage to femoral head during cement curing; this maybe linked to fracture (reported incidence ~2%) and early failure. We investigated the effect of a modifid surgical technique using pulse lavage, lesser trochanter suction and early reduction on the maximum temperature recorded in the femoral head during HRA, compared to manual lavage and reduction after cement curing.

Methods: Patients undergoing total hip replacement (THR) were given a dummy HRA procedure, during which a temperature probe was inserted into the femoral head and the measuring tip placed close to the reamed surface; the position of the probe was confirmed by inter-operative xray. Four subjects received a dummy HRA femoral component using manual lavage and Simplex cement. The implanted femur was kept dislocated until the cement cured. The implanted heads were then removed and sectioned to locate the temperature probes, the THR surgery was then performed. Five patients receiving a definitive HRA were also measured; for these subjects suction on the lesser trochanter was used, pulse lavage given for 30 seconds prior to cementing with Simplex, and pulse lavage of the femoral head for 2 minutes, applied 1 minute after cementing the femoral component. The implanted joint was then immediately reduced and a further two minutes of pulse lavage applied to the reduced joint. Temperatures were recorded until the cement finally cured. In every case the cement was hand mixed for 1 minute and the component implanted at 2 minutes 30 seconds after mixing began.

Results: Sectioning showed that probe tips were < 0.5mm from cement mantle. The maximum temperature recorded in the femoral head was significantly (p=0.014) greater for the manual technique, median value of 47.2°C (37.0 to 67.9°C), than for the pulse lavage technique, median value of 32.7°C (31.7 to 35.6°C).

Discussion: The results show that excessive bone temperatures can occur during hip resurfacing. Temperatures above 45°C kill bone cells, the manual technique may lead to substantial thermal necrosis. Technique modification, with the use of suction on the lesser trochanter, generous use of pulse-lavage and joint reduction prior to cement curing, significantly reduced the temperatures recorded. With the modified technique, the maximum temperatures were well below the threshold of thermal damage. This modified technique is recommended as the potential for thermal bone necrosis is significantly reduced.

We examined the relationships between the serum levels of chromium and cobalt ions and the inclination angle of the acetabular component and the level of activity in 214 patients implanted with a metal-on-metal resurfacing hip replacement. Each patient had a single resurfacing and no other metal in their body. All serum measurements were performed at a minimum of one year after operation. The inclination of the acetabular component was considered to be steep if the abduction angle was greater than 55°.

There were significantly higher levels of metal ions in patients with steeply-inclined components (p = 0.002 for chromium, p = 0.003 for cobalt), but no correlation was found between the level of activity and the concentration of metal ions. A highly significant (p < 0.001) correlation with the arc of cover was found. Arcs of cover of less than 10 mm were correlated with a greater risk of high concentrations of serum metal ions. The arc of coverage was also related to the design of the component and to size as well as to the abduction angle of the acetabular component. Steeply-inclined acetabular components, with abduction angles greater than 55°, combined with a small size of component are likely to give rise to higher serum levels of cobalt and chromium ions. This is probably due to a greater risk of edge-loading.

Dislocation rates after total hip arthroplasty vary from 1% to 8% and approximately 1% will require revision surgery to treat hip instability. From these revisions only 60% is successful with redislocation frequencies from 8.2% to 39%. A full-constrained acetabular cup can be used by hip surgeons as a measure of salvage. The purpose of this paper is to describe the complications the authors have encountered in a short postoperative period with the use of three different types of full-constrained acetabular cups.

Over a period of three years, between January 1999 and December 2001, 25 full-constrained acetabular components were implanted. Three different types of full-constrained prostheses were used: the Osteonics Bipolar Constrained Insert (Osteonics Corp., Allendale, NJ), the Ringloc Constrained Liner (Biomet Inc., Warsaw, IN) and the Trilogy Constrained Liner (Zimmer Inc., Warsaw, IN). In 14 cases the full-constrained cups were used in revision hip arthroplasty and in 4 cases as revision for failed full-constrained implants. Seven patients received a primary constrained acetabular prosthesis.

Of the 23 patients one woman died after a follow-up period of 25.5 months. The other 22 patients had an average clinical follow-up of 22.5 months, ranging from 16 to 47.5 months. In 8 prostheses 6 different postoperative problems were encounterd, resulting in a total of 32 % failures. Seven of the complications were different types of constrained acetabular cup disassembly and one complication was due to a failure at the interface between bone and the porous-metal surface. As alternative treatment option, the authors have used the Birmingham Hip Resurfacing (Midland Medical Technologies, Birmingham) Dysplasia cup with modular head in seven patients who sustained recurrent dislocations after multiple revision surgery, with only one failure (1/7 - recurrent dislocation) after a mean follow-up of two years.

In view of the high short-term complication rate (32%) in a follow-up period of three years, the authors strongly recommend judicious use of the constrained acetabular prosthesis. The component should only be applied as a salvage tool in selected patients in whom no other treatment options would be successful. In these cases the use of a constrained acetabular prosthesis might solve the problems encountered in the majority of patients, but it can never guarantee a problem-free course of this cup. Alternative options such as the use of large diameter femoral heads with a resurfacing cup, using a metal-on-metal friction couple should be considered as a worthwhile alternative in those cases.

Postoperative dislocations are known to be a big problem in revision surgery. In literature dislocation rates vary from 4.8% to 33% after previous surgery. In revision surgery, impingement of the implant components, the capsular and soft tissue release, muscular weakness and greater trochanter problems can give additional instability. The reason for revision is important, where instability, infection and tumour cases will lead to a higher percentage of dislocations. The use of big metal heads on polyethylene should be avoided because of the higher volumetric wear. With the new developments of metal-on-metal hip resurfacing and the production of big modular metal heads, the metal-on-metal bearing should guarantee a low-wear result without osteolysis.

Between November 2000 and December 2003 45 patients requiring a revision were treated with a Birmingham Hip Resurfacing cup (MMT, UK) and a big metal-on-metal modular head. All surgery was done with a posterolateral approach. Cup sizes range from 44 to 66 mm, head sizes range from 38 to 58 mm. The head sizes most often used were 58 mm, 54 mm and 50 mm. All patients were prospective followed using the Orthowave software (CRDA France).

In this series of 45 revisions (mean age 56.17) with large modular heads we encountered 2 dislocations, which give us a dislocation rate of 4.4%. One of these dislocations became recurrent and was revised to a full-constrained acetabular component.

Our own dislocation rate in revision hip surgery is 13% (21/159) in the anterolateral approach. Dislocations using the posterolateral approach increased this percentage to 14.8% (21/141). Taking in account that 31% of the causes of revision were infection and recurrent dislocation, this trial demonstrates that large diameter ball heads give beside a better range of movement also a statistically proven reduction in the dislocation rate in revision hip surgery.

The difference in outcome after uncemented ceramic-on-ceramic total hip and metal-on-metal resurfacing is looked at in comparable patient groups. Theoretical advantages in resurfacing are less bone resection, normal femoral loading, avoidance of stress shielding and restoration of normal anatomy. In addition, reduced risk of dislocation, less leg lengthening and easier revision should convince us to perform metal-on-metal resurfacing. These advantages of resurfacing, the subjective “better feeling” and having a more “normal” joint is illustrated by objective proof with functional scores and activity.

The first 250 cases of 1067 (September 1998 –March 2004) performed Birmingham Hip resurfacings (MMT, UK) (follow up 2–5 years, mean age 49.54) were scored clinically and functionally. In the same period (July 1996 – September 2003) 164 ceramic-on-ceramic Ancafit total uncemented prostheses (Wright Medical, US) were implanted inthe same age and activity group as the resurfacings. The first group of 126 patients (follow up 2 – 6 years, mean age 46.76) was compared with the resurfacing group. All the data were collected intra operatively and postoperatively, mostly in a prospective way.

At the most recent follow-up there was a significant statistical difference in Harris Hip Scores (global and total), and activity function between the 2 types of pros-theses. Resurfacing scored a Harris Hip Total of 97.9 (ceramic THA 92.1). Of the resurfacing patients 60.71 had a strenuous activity (ceramic THA 30.43). Dislocation rate in resurfacing group was 0.4% (ceramic THA 3%).

The early clinical results in the group of metal-on-metal resurfacing are very satisfactory with Harris and PMA scores indicating early clinical success. The high percentage of strenuous activity in this young patient group satisfies the expectations of the resurfacing. The difference with a normal uncemented hip is stated with a better outcome in Harris Hip Scores and a better activity level.

A prospective study of serum and urinary ion levels was undertaken in a triathlete who had undergone a metal-on-metal resurfacing arthroplasty of the hip four years previously. The one month study period included the final two weeks of training, the day of the triathlon, and the two weeks immediately post-race. Serum cobalt and chromium levels did not vary significantly throughout this period, including levels recorded on the day after the 11-hour triathlon. Urinary excretion of chromium increased immediately after the race and had returned to pre-race levels six days later. The clinical implications are discussed.

Introduction: The purpose of this retrospective study is to compare long-term whole blood metal ion concentrations (Co, Cr, Ni, Mo) between two different metal-on-metal total hip arthroplasties and a metal-on-polyethylene control group, in relationship with physical activity.

Materials and methods: Between 1996 and 2000, different conventional prosthetic designs were implanted at our hospital. For this study, three groups were chosen according to the bearing surfaces used. Patients who had undergone other surgical interventions with implantation of potential sources of Cr/Co were excluded. Patients taking medication or dietary supplements containing Cr/Co were also excluded. In group 1, 17 patients with a 28 mm metal-on-metal bearing, type Metasul (Zimmer), were included. Group 2 comprised 11 patients with a 28 mm metal-on-metal bearing, type M2a (Biomet). The control group consisted of 9 patients with a 28 mm metal-on-polyethylene bearing in combination with a cemented CoCr stem. The three groups were demographically comparable. The postoperative clinical performance was evaluated using the Harris hip score and the Merle-dAubigne score. The activity level was measured using the Baecke questionnaire. Whole blood samples were taken in a standardized way and analysed by high resolution inductively coupled plasma mass spectrometer analysis.

Results: At an average follow-up of 4 years, the mean Harris Hip Score was 88.35 in group 1, 82.64 in group 2 and 90.89 in the control group. The mean Baecke Activity Score was 7.32 in group 1, 5.51 in group 2 and 6.49 in the control group. The mean Cr level was 0.27 in group 1, 0.63 in group 2 and 0.19 in the control group. The mean Co level was 0.63 in group 1, 1.06 in group 2 and 0.51 in the control group. The mean Ni level was 1.11 in group 1, 1.10 in group 2 and 1.31 in the control group. The mean Mo level was 0.65 in group 1, 0.77 in group 2 and 0.56 in the control group.

Conclusions: At a minimum follow-up of 4 years, no statistically significant differences were seen in clinical outcomes among the three groups. The only statistically significant difference in metal ion concentration among the three groups was observed for the Cr concentration between the M2a group and the metal-on-polyethylene group. There is also a positive correlation between the ion concentrations (Cr and Co) on the one hand and the activity level and Body Mass Index on the other.

We present the results of our initial experience with the use of the Birmingham metal-on-metal Hip Resurfacing. The Birmingham Hip Resurfacing(BHR) consists of a high carbon chrome cobalt uncemented hydroxyapatite cupand a cemented femoral component. For patients with severe dysplasia adysplasia cup with screws was used. We utilise this kind of prosthesis for the younger patients (< 65 year). Excellent clinical results are encountered; none of the early problems aswith the old Wagner resurfacing (metal-on-poly) are seen. Our early results are similar to the encouraging results of the series of D.McMinn/R.Treacy.

From September 1998 through April 2001, 185 BHR arthroplasties were performed. The mean age was 49.7 year (16–75). More male patients were operated with this method than female patients (64%–36%). The aetiology was osteoarthritis (81%), necrosis (9%), dysplasia (CDH) (6.6%).

Results: The last 115 patients were reviewed with a follow up from 1 month to 2.5year. Only two patients were lost for follow-up because of death. There was no pain in 92.3% of the cases. The total Harris Hip Score had a mean of97.91, a median score of 100 (71–100). Merle d’Aubigné total Score was 17.36 (12–18). There was a strenuous activity in 70.2% of the patients.

The mean length of stay in hospital was six days (range: 2–26). Complications were: One fractured neck of femur, one ischial nerve palsy and one guide pin was left in the femur. All patients were followed on regular basis and the X-rays were studied for angle of preoperative neck of femur, postoperative angle of the femoral component, angle of cup placement and the parallelism of both components.

Conclusion: Performing only alternate bearings in patients under the age of 75, the metal-on-metal Birmingham Hip Resurfacing looks a good alternative in young active patients and the results are promising.