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1.  Total hip arthroplasty versus resurfacing arthroplasty in the treatment of patients with arthritis of the hip joint: single centre, parallel group, assessor blinded, randomised controlled trial 
Objectives To compare the clinical and cost effectiveness of total hip arthroplasty with resurfacing arthroplasty in patients with severe arthritis of the hip.
Design Single centre, two arm, parallel group, assessor blinded, randomised controlled trial with 1:1 treatment allocation.
Setting One large teaching hospital in the United Kingdom.
Participants 126 patients older than 18 years with severe arthritis of the hip joint, suitable for resurfacing arthroplasty of the hip. Patients were excluded if they were considered to be unable to adhere to trial procedures or complete questionnaires.
Interventions Total hip arthroplasty (replacement of entire femoral head and neck); hip resurfacing arthroplasty (replacement of the articular surface of femoral head only, femoral neck remains intact). Both procedures replaced the articular surface of the acetabulum.
Main outcome measures Hip function at 12 months after surgery, assessed using the Oxford hip score and Harris hip score. Secondary outcomes were quality of life, disability rating, physical activity level, complications, and cost effectiveness.
Results 60 patients were randomly assigned to hip resurfacing arthroplasty and 66 to total hip arthroplasty. Intention to treat analysis showed no evidence for a difference in hip function between treatment groups at 12 months (t test, P=0.242 and P=0.070 for Oxford hip score and Harris hip score, respectively); 95% of follow-up data was available for analysis. Mean Oxford hip score was 40.4 (95% confidence interval 37.9 to 42.9) in the resurfacing group and 38.2 (35.3 to 41.0) in the total arthroplasty group (estimated treatment effect size 2.23 (−1.52 to 5.98)). Mean Harris hip score was 88.4 (84.4 to 92.4) in the resurfacing group and 82.3 (77.2 to 87.5) in the total arthroplasty group (6.04 (−0.51 to 12.58)). Although we saw no evidence of a difference, we cannot definitively exclude clinically meaningful differences in hip function in the short term. Overall complication rates did not differ between treatment groups (P=0.291). However, we saw more wound complications in the total arthroplasty group (P=0.056) and more thromboembolic events in the resurfacing group (P=0.049).
Conclusions No evidence of a difference in hip function was seen in patients with severe arthritis of the hip, one year after receiving a total hip arthroplasty versus resurfacing arthroplasty. The long term effects of these interventions remain uncertain.
Trial registration Current Controlled Trials ISRCTN33354155, UKCRN 4093.
PMCID: PMC3330050  PMID: 22517930
2.  A randomised controlled trial of total hip arthroplasty versus resurfacing arthroplasty in the treatment of young patients with arthritis of the hip joint 
Hip replacement (arthroplasty) surgery is a highly successful treatment for patients with severe symptomatic arthritis of the hip joint. For older patients, several designs of Total Hip Arthroplasty have shown excellent results in terms of both function and value for money. However, in younger more active patients, there is approximately a 50% failure rate at 25 years for traditional implants. Hip resurfacing is a relatively new arthroplasty technique. In a recent review of the literature on resurfacing arthroplasty it was concluded that the short-term functional results appear promising but some potential early disadvantages were identified, including the risk of femoral neck fracture and collapse of the head of the femur. The aim of the current study is to assess whether there is a difference in functional hip scores at one year post-operation between Total Hip Arthroplasty and Resurfacing Arthroplasty. Secondary aims include assessment of complication rates for both procedures as well cost effectiveness.
All patients medically fit for surgery and deemed suitable for a resurfacing arthroplasty are eligible to take part in this study. A randomisation sequence will be produced and administered independently. After consenting, all patients will be clinically reviewed and hip function, quality of life and physical activity level will be assessed through questionnaires. The allocated surgery will then be performed with the preferred technique of the surgeon. Six weeks post-operation hip function will be assessed and complications recorded. Three, six and 12 months post-operation hip function, quality of life and physical activity level will be assessed. Additional information about patients' out-of-pocket expenses will also be collected.
Trial registration
Current Controlled Trials ISRCTN33354155
UKCLRN portfolio ID 4093
PMCID: PMC2826290  PMID: 20074324
3.  Is Resurfacing Arthroplasty Appropriate for Posttraumatic Osteoarthritis? 
High survival has been reported for resurfacing arthroplasty in patients with femoral deformities. Also, hardware removal may not always be necessary with resurfacing arthroplasty and may eliminate some of the difficulties performing total hip arthroplasty (THA) in patients with posttraumatic osteoarthritis.
We therefore asked: (1) are survivorship higher in patients who underwent resurfacing arthroplasty compared with patients with nontraumatic osteoarthritis; and (2) are those higher compared with all patients who have resurfacing?
We identified 29 patients (29 hips) who had hip resurfacing for posttraumatic arthritis. These were compared with a matched cohort who had hip resurfacings for nontraumatic osteoarthritis and to all patients who underwent hip resurfacing for osteoarthritis during this time. The mean age was 47 years and mean body mass index was 27 kg/m2. Survivorship and Harris hip scores were compared. Radiographs were evaluated for signs of radiolucencies, penciling, or osteolysis. The mean followup was 39 months (range, 24–99 months).
The 5-year survivorship was 90% in the posttraumatic group, 93% in the matched osteoarthritis group, and 97% in the entire osteoarthritis cohort. The mean Harris hip score for the posttraumatic group at last followup was 90 points. Other than the patients who underwent revision, we observed no radiographic radiolucencies or loosening in any of the groups.
The survival of resurfacing arthroplasty appears comparable to THA in posttraumatic osteoarthritis and for resurfacing in patients with osteoarthritis. Therefore, resurfacing may present an alternative treatment to THA in these patients.
Level of Evidence
Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
PMCID: PMC3094605  PMID: 21132415
4.  Revision rate of Birmingham Hip Resurfacing arthroplasty: comparison of published literature and arthroplasty register data 
International Orthopaedics  2012;36(7):1349-1354.
Hip resurfacing arthroplasty has gained popularity for treating young and active patients who have arthritis. There are two major data sources for assessing outcome and revision rate after total joint arthroplasty: sample-based clinical trials and national arthroplasty registers. The purpose of this study was to evaluate the outcome of the Birmingham Hip Resurfacing (BHR) arthroplasty in terms of revision rate as reported in clinical studies and recorded by national arthroplasty registers.
A comprehensive literature research was performed from English-language, peer-reviewed journals and annual reports from national joint arthroplasty registers worldwide. Only publications from MEDLINE-listed journals were included. The revision rate was used as the primary outcome parameter. In order to allow for direct comparison of different data sets, calculation was based on revisions per 100 observed component years. For statistical analysis, confidence intervals (CI) were calculated.
A total of 18,708 implants, equivalent to 106,565 observed component years, were analysed in the follow-up studies. The register reports contained 9,806 primary cases corresponding to 44,294 observed component years. Statistical analysis revealed a significant difference in revisions per 100 observed component years between the development team (0.27; CI: 0.14–0.40) and register data (0.74; CI: 0.72–0.76).
The BHR arthroplasty device shows good results in terms of revision rate in register data as well as in clinical studies. However, the excellent results reported by the development team are not reproducible by other surgeons. Based on the results of our study, we believe that comprehensive national arthroplasty registers are the most suitable tool for assessing hip arthroplasty revision rate.
PMCID: PMC3385890  PMID: 22350138
5.  Hip resurfacing arthroplasty 
Acta Orthopaedica  2010;81(6):680-683.
Background and purpose
Hip resurfacing arthroplasty is claimed to allow higher activity levels and to give better quality of life than total hip arthroplasty. In this literature review, we assessed the therapeutic value of hip resurfacing arthroplasty as measured by functional outcome.
An extensive literature search was performed using the PubMed, Embase, and Cochrane databases.
9 patient series, 1 case-control study, and 1 randomized controlled trial (RCT) were included. Clinically and statistically significant improvement in sporting activity and hip scores were found in 10 studies.
Studies with low levels of evidence have shown improvement in various different hip scores and one RCT showed better outcomes with hip resurfacing arthroplasty. There is no high-level evidence to prove that there is improved clinical outcome using hip resurfacing arthroplasty. More randomized research needs to be done.
PMCID: PMC3216077  PMID: 20860440
6.  The John Charnley Award: Metal-on-Metal Hip Resurfacing versus Large-diameter Head Metal-on-Metal Total Hip Arthroplasty: A Randomized Clinical Trial 
Resurfacing arthroplasty has become an attractive option for young patients who want to maintain a high activity level. One recent study reported modestly increased activity levels for patients with resurfacing compared to standard total hip arthroplasty (THA). We conducted a prospective randomized clinical trial to compare clinical outcomes of resurfacing versus large-head metal-on-metal total hip arthroplasty. We randomized 107 patients deemed eligible for resurfacing arthroplasty to have either resurfacing or standard THA. Patients were assessed for quality-of-life outcomes using the PAT-5D index, WOMAC, SF-36, and UCLA activity score. The minimum followup was 0.8 years (mean, 1.1 years; range, 0.8–2.2 years). Of the 73 patients followed at least one year, both groups reported improvement in quality of life on all outcome measures. There was no difference in quality of life between the two arms in the study. Serum levels of cobalt and chromium were measured in a subset of 30 patients. In both groups cobalt and chromium was elevated compared to baseline. Patients receiving a large-head metal-on-metal total hip had elevated ion levels compared to the resurfacing arm of the study. At 1 year, the median serum cobalt increased 46-fold from baseline in patients in the large-head total hip group, while the median serum chromium increased 10-fold. At 1 year, serum cobalt was 10-fold higher and serum chromium 2.6-fold higher than in the resurfacing arm. Due to these excessively high metal ion levels, the authors recommend against further use of this particular large-head total hip arthroplasty.
Level of Evidence: Level I, randomized clinical trial. See Guidelines for Authors for a complete description of levels of evidence.
PMCID: PMC2806981  PMID: 19697090
7.  Intraoperative Radiographs for Placing Acetabular Components in Hip Resurfacing Arthroplasty 
Various clinical and biomechanical studies suggest certain acetabular positions may be associated with higher wear and failure rates in modern metal-on-metal hip resurfacing arthroplasties. However, there are no widely available, reliable, and cost-effective surgical techniques that ensure surgeons are able to place an acetabular component within the safe range of inclination angles after hip resurfacing surgeries.
We investigated the accuracy of intraoperative radiographs to determine the acetabular inclination angle in resurfacing arthroplasty procedures.
Patients and Methods
The study group included the first 100 resurfacing arthroplasties performed after we started routinely checking the intraoperative acetabular inclination angles. The acetabular component was repositioned if the intraoperative acetabular inclination angle was out of the target range of 30° to 50°. The control group included the previous 100 resurfacing arthroplasties performed without the benefit of intraoperative radiographs. A posterior minimally invasive surgical approach was used in both groups. Demographics and diagnoses were similar in both groups.
The average (± SD) difference between the intraoperative and 6-week radiographs was 2.7° ± 2.5°. The acetabular inclination angles at 6-week followup were within the targeted range more frequently in the study group than in the control group (outliers: 4% versus 29%).
These data suggest a single intraoperative radiograph is a quick, reliable, and cost-effective method for ensuring the acetabular inclination angle is within the targeted range.
Level of Evidence
Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
PMCID: PMC3094643  PMID: 21108028
8.  Metal-on-Metal Total Hip Resurfacing Arthroplasty 
Executive Summary
The objective of this review was to assess the safety and effectiveness of metal on metal (MOM) hip resurfacing arthroplasty for young patients compared with that of total hip replacement (THR) in the same population.
Clinical Need
Total hip replacement has proved to be very effective for late middle-aged and elderly patients with severe degenerative diseases of the hips. As indications for THR began to include younger patients and those with a more active life style, the longevity of the implant became a concern. Evidence suggests that these patients experience relatively higher rates of early implant failure and the need for revision. The Swedish hip registry, for example, has demonstrated a survival rate in excess of 80% at 20 years for those aged over 65 years, whereas this figure was 33% by 16 years in those aged under 55 years.
Hip resurfacing arthroplasty is a bone-conserving alternative to THR that restores normal joint biomechanics and load transfer. The technique has been used around the world for more than 10 years, specifically in the United Kingdom and other European countries.
The Technology
Metal-on-metal hip resurfacing arthroplasty is an alternative procedure to conventional THR in younger patients. Hip resurfacing arthroplasty is less invasive than THR and addresses the problem of preserving femoral bone stock at the initial operation. This means that future hip revisions are possible with THR if the initial MOM arthroplasty becomes less effective with time in these younger patients. The procedure involves the removal and replacement of the surface of the femoral head with a hollow metal hemisphere, which fits into a metal acetabular cup.
Hip resurfacing arthroplasty is a technically more demanding procedure than is conventional THR. In hip resurfacing, the femoral head is retained, which makes it much more difficult to access the acetabular cup. However, hip resurfacing arthroplasty has several advantages over a conventional THR with a small (28 mm) ball. First, the large femoral head reduces the chance of dislocation, so that rates of dislocation are less than those with conventional THR. Second, the range of motion with hip resurfacing arthroplasty is higher than that achieved with conventional THR.
A variety of MOM hip resurfacing implants are used in clinical practice. Six MOM hip resurfacing implants have been issued licences in Canada.
Review Strategy
A search of electronic bibliographies (OVID Medline, Medline In-Process and Other Non-Indexed Citations, Embase, Cochrane CENTRAL and DSR, INAHTA) was undertaken to identify evidence published from Jan 1, 1997 to October 27, 2005. The search was limited to English-language articles and human studies. The literature search yielded 245 citations. Of these, 11 met inclusion criteria (9 for effectiveness, 2 for safety).
The result of the only reported randomized controlled trial on MOM hip resurfacing arthroplasty could not be included in this assessment, because it used a cemented acetabular component, whereas in the new generation of implants, a cementless acetabular component is used. After omitting this publication, only case series remained.
Summary of Findings
Health Outcomes
The Harris hip score and SF-12 are 2 measures commonly used to report health outcomes in MOM hip resurfacing arthroplasty studies. Other scales used are the Oxford hip score and the University of California Los Angeles hip score.
The case series showed that the mean revision rate of MOM hip resurfacing arthroplasty is 1.5% and the incidence of femoral neck fracture is 0.67%. Across all studies, 2 cases of osteonecrosis were reported. Four studies reported improvement in Harris hip scores. However, only 1 study reported a statistically significant improvement. Three studies reported improvement in SF-12 scores, of which 2 reported a significant improvement. One study reported significant improvement in UCLA hip score. Two studies reported postoperative Oxford hip scores, but no preoperative values were reported.
None of the reviewed studies reported procedure-related deaths. Four studies reported implant survival rates ranging from 94.4% to 99.7% for a follow-up period of 2.8 to 3.5 years. Three studies reported on the range of motion. One reported improvement in all motions including flexion, extension, abduction-adduction, and rotation, and another reported improvement in flexion. Yet another reported improvement in range of motion for flexion abduction-adduction and rotation arc. However, the author reported a decrease in the range of motion in the arc of flexion in patients with Brooker class III or IV heterotopic bone (all patients were men).
Safety of Metal-on-Metal Hip Resurfacing Arthroplasty
There is a concern about metal wear debris and its systemic distribution throughout the body. Detectable metal concentrations in the serum and urine of patients with metal hip implants have been described as early as the 1970s, and this issue is still controversial after 35 years.
Several studies have reported high concentration of cobalt and chromium in serum and/or urine of the patients with metal hip implants. Potential toxicological effects of the elevated metal ions have heightened concerns about safety of MOM bearings. This is of particular concern in young and active patients in whom life expectancy after implantation is long.
Since 1997, 15 studies, including 1 randomized clinical trial, have reported high levels of metal ions after THR with metal implants. Some of these studies have reported higher metal levels in patients with loose implants.
Adverse Biological Effects of Cobalt and Chromium
Because patients who receive a MOM hip arthroplasty are shown to be exposed to high concentrations of metallic ions, the Medical Advisory Secretariat searched the literature for reports of adverse biological effects of cobalt and chromium. Cobalt and chromium make up the major part of the metal articulations; therefore, they are a focus of concern.
Risk of Cancer
To date, only one study has examined the incidence of cancer after MOM and polyethylene on metal total hip arthroplasties. The results were compared to that of general population in Finland. The mean duration of follow-up for MOM arthroplasty was 15.7 years; for polyethylene arthroplasty, it was 12.5 years. The standardized incidence ratio for all cancers in the MOM group was 0.95 (95% CI, 0.79–1.13). In the polyethylene on metal group it was 0.76 (95% CI, 0.68–0.86). The combined standardized incidence ratio for lymphoma and leukemia in the patients who had MOM THR was 1.59 (95% CI, 0.82–2.77). It was 0.59 (95% CI, 0.29–1.05) for the patients who had polyethylene on metal THR. Patients with MOM THR had a significantly higher risk of leukemia. All patients who had leukemia were aged over than 60 years.
Cobalt Cardiotoxicity
Epidemiological Studies of Myocardiopathy of Beer Drinkers
An unusual type of myocardiopathy, characterized by pericardial effusion, elevated hemoglobin concentrations, and congestive heart failure, occurred as an epidemic affecting 48 habitual beer drinkers in Quebec City between 1965 and 1966. This epidemic was directly related the consumption of a popular beer containing cobalt sulfate. The epidemic appeared 1 month after cobalt sulfate was added to the specific brewery, and no further cases were seen a month after this specific chemical was no longer used in making this beer. A beer of the same name is made in Montreal, and the only difference at that time was that the Quebec brand of beer contained about 10 times more cobalt sulphate. Cobalt has been added to some Canadian beers since 1965 to improve the stability of the foam but it has been added in larger breweries only to draught beer. However, in small breweries, such as those in Quebec City, separate batches were not brewed for bottle and draught beer; therefore, cobalt was added to all of the beer processed in this brewery.
In March 1966, a committee was appointed under the chairmanship of the Deputy Minister of Health for Quebec that included members of the department of forensic medicine of Quebec’s Ministry of Justice, epidemiologists, members of Food and Drug Directorate of Ottawa, toxicologists, biomedical researchers, pathologists, and members of provincial police. Epidemiological studies were carried out by the Provincial Ministry of Health and the Quebec City Health Department.
The association between the development of myocardiopathy and the consumption of the particular brand of beer was proven. The mortality rate of this epidemic was 46.1% and those who survived were desperately ill, and recovered only after a struggle for their lives.
Similar cases were seen in Omaha (Nebraska). The epidemic started after a cobalt additive was used in 1 of the beers marketed in Nebraska. Sixty-four patients with the clinical diagnosis of alcoholic myocardiopathy were seen during an 18-month period (1964–1965). Thirty of these patients died. The first patient became ill within 1 month after cobalt was added to the beer, and the last patient was seen within 1 month of withdrawal of cobalt.
A similar epidemic occurred in Minneapolis, Minnesota. Between 1964 and 1967, 42 patients with acute heart failure were admitted to a hospital in Minneapolis, Minnesota. Twenty of these patients were drinking 6 to 30 bottles per day of a particular brand of beer exclusively. The other 14 patients also drank the same brand of beer, but not exclusively. The mortality rate from the acute illness was 18%, but late deaths accounted for a total mortality rate of 43%. Examination of the tissue from these patients revealed markedly abnormal changes in myofibrils (heart muscles), mitochondria, and sarcoplasmic reticulum.
In Belgium, a similar epidemic was reported in 1966, in which, cobalt was used in some Belgian beers. There was a difference in mortality between the Canadian or American epidemic and this series. Only 1 of 24 patients died, 1.5 years after the diagnosis. In March 1965, at an international meeting in Brussels, a new heart disease in chronic beer drinkers was described. This disease consists of massive pericardial effusion, low cardiac output, raised venous pressure, and polycythemia in some cases. This syndrome was thought to be different from the 2 other forms of alcoholic heart disease (beriberi and a form characterized by myocardial fibrosis).
The mystery of the above epidemics as stated by investigators is that the amount of cobalt added to the beer was below the therapeutic doses used for anemia. For example, 24 pints of Quebec brand of beer in Quebec would contain 8 mg of cobalt chloride, whereas an intake of 50 to 100 mg of cobalt as an antianemic agent has been well tolerated. Thus, greater cobalt intake alone does not explain the occurrence of myocardiopathy. It seems that there are individual differences in cobalt toxicity. Other features, like subclinical alcoholic heart disease, deficient diet, and electrolyte imbalance could have been precipitating factors that made these patients susceptible to cobalt’s toxic effects.
In the Omaha epidemic, 60% of the patients had weight loss, anorexia, and occasional vomiting and diarrhea 2 to 6 months before the onset of cardiac symptoms. In the Quebec epidemic, patients lost their appetite 3 to 6 months before the diagnosis of myocardiopathy and developed nausea in the weeks before hospital admission. In the Belgium epidemic, anorexia was one of the most predominant symptoms at the time of diagnosis, and the quality and quantity of food intake was poor. Alcohol has been shown to increase the uptake of intracoronary injected cobalt by 47%. When cobalt enters the cells, calcium exits; this shifts the cobalt to calcium ratio. The increased uptake of cobalt in alcoholic patients may explain the high incidence of cardiomyopathies in beer drinkers’ epidemics.
As all of the above suggest, it may be that prior chronic exposure to alcohol and/or a nutritionally deficient diet may have a marked synergistic effect with the cardiotoxicity of cobalt.
MOM hip resurfacing arthroplasty has been shown to be an effective arthroplasty procedure as tested in younger patients.
However, evidence for effectiveness is based only on 7 case series with short duration of follow-up (2.8–3.5 years). There are no RCTs or other well-controlled studies that compare MOM hip resurfacing with THR.
Revision rates reported in the MOM studies using implants currently licensed in Canada (hybrid systems, uncemented acetabular, and cemented femoral) range from 0.3% to 3.6% for a mean follow-up ranging from 2.8 to 3.5 years.
Fracture of femoral neck is not very common; it occurs in 0.4% to 2.2% of cases (as observed in a short follow-up period).
All the studies that measured health outcomes have reported improvement in Harris Hip and SF-12 scores; 1 study reported significant reduction in pain and improvement in function, and 2 studies reported significant improvement in SF-12 scores. One study reported significant improvement in UCLA Hip scores.
Concerns remain on the potential adverse effects of metal ions. Longer-term follow-up data will help to resolve the inconsistency of findings on adverse effects, including toxicity and carcinogenicity.
Ontario-Based Economic Analysis
The device cost for MOM ranges from $4,300 to $6,000 (Cdn). Traditional hip replacement devices cost about $2,000 (Cdn). Using Ontario Case Costing Initiative data, the total estimated costs for hip resurfacing surgery including physician fees, device fees, follow-up consultation, and postsurgery rehabilitation is about $15,000 (Cdn).
Cost of Total Hip Replacement Surgery in Ontario
MOM hip arthroplasty is generally recommended for patients aged under 55 years because its bone-conserving advantage enables patients to “buy time” and hence helps THRs to last over the lifetime of the patient. In 2004/2005, 15.9% of patients who received THRs were aged 55 years and younger. It is estimated that there are from 600 to 1,000 annual MOM hip arthroplasty surgeries in Canada with an estimated 100 to 150 surgeries in Ontario. Given the increased public awareness of this device, it is forecasted that demand for MOM hip arthroplasty will steadily increase with a conservative estimate of demand rising to 1,400 cases by 2010 (Figure 10). The net budget impact over a 5-year period could be $500,000 to $4.7 million, mainly because of the increasing cost of the device.
Projected Number of Metal-on-Metal Hip Arthroplasty Surgeries in Ontario: to 2010
PMCID: PMC3379532  PMID: 23074495
9.  Hip Resurfacing Results for Osteonecrosis Are as Good as for Other Etiologies at 2 to 12 Years 
A bone-conserving prosthetic solution, such as hip resurfacing arthroplasty, is desirable for patients with osteonecrosis (ON) of the femoral head because of their young age. However, many surgeons are reluctant to perform hip resurfacing for ON because of large femoral head defects. To ascertain whether this reluctance is warranted, we determined the mid- to long-term effects of ON on the survivorship, radiographic implant fixation, and disease-specific and quality-of-life scores of hip resurfacing. We compared the results of metal-on-metal resurfacing performed for ON of the hip (including large lesions) with those of resurfacing performed for other causes. The ON group had 70 patients (85 hips) and the control group 768 patients (915 hips) including all other etiologies operated on during the same period. The ON group was younger and had a greater incidence of femoral defects, a smaller component size, and a lower body mass index, three variables previously shown to reduce survivorship in hip resurfacing. We observed no difference in survivorship between the ON group and the control group even after adjusting for head size, body mass index, and defect size. Pain relief, walking, and function scores were comparable postoperatively. The activity level was lower in the ON group. Our data suggest ON is not a contraindication for resurfacing even with large femoral head defects.
Level of Evidence: Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
PMCID: PMC2806980  PMID: 19756906
10.  A comparison of leg length and femoral offset discrepancies in hip resurfacing, large head metal-on- metal and conventional total hip replacement: a case series 
A discrepancy in leg length and femoral offset restoration is the leading cause of patient dissatisfaction in hip replacement surgery and has profound implications on patient quality of life. The aim of this study is to compare biomechanical hip reconstruction in hip resurfacing, large-diameter femoral head hip arthroplasty and conventional total hip replacement.
Sixty patient's post-operative radiographs were reviewed; 20 patients had a hip resurfacing (HR), 20 patients had a Large Head Metal-on-metal (LHM) hip replacement and 20 patients had a conventional small head Total Hip Replacement (THR). The leg length and femoral offset of the operated and unoperated hips were measured and compared.
Hip resurfacing accurately restored hip biomechanics with no statistical difference in leg length (P = 0.07) or femoral offset (P = 0.95) between the operated and non-operative hips. Overall HR was superior for reducing femoral offset discrepancies where it had the smallest bilateral difference (-0.2%, P = 0.9). The traditional total hip replacement was least effective at restoring the hip anatomy.
The use of a larger-diameter femoral head in hip resurfacing does not fully account for the superior biomechanical restoration, as LHM did not restore femoral offset as accurately. We conclude that restoration of normal hip biomechanics is best achieved with hip resurfacing.
PMCID: PMC3298517  PMID: 22206621
Hip resurfacing; total hip replacement; leg length; femoral offset
11.  Sex differences in the morphological failure patterns following hip resurfacing arthroplasty 
BMC Medicine  2011;9:113.
Metal-on-metal hybrid hip resurfacing arthroplasty (with a cementless acetabular component and a cemented femoral component) is offered as an alternative to traditional total hip arthroplasty for the young and active adult with advanced osteoarthritis. Although it has been suggested that women are less appropriate candidates for metal-on-metal arthroplasty, the mechanisms of prosthesis failure has not been fully explained. While specific failure patterns, particularly osteonecrosis and delayed type hypersensitivity reactions have been suggested to be specifically linked to the sex of the patient, we wished to examine the potential influence of sex, clinical diagnosis, age of the patient and the size of the femoral component on morphological failure patterns in a large cohort of retrieved specimens following aseptic failure of hip resurfacing arthroplasty.
Femoral remnants retrieved from 173 hips with known patient's sex were morphologically analyzed for the cause of failure. The results were compared with the control group of the remaining 31 failures from patients of unknown sex. The odds ratios (OR) and 95% confidence intervals (CI) of the following morphologically defined variables were calculated using logistic regression analysis: periprosthetic fractures (n = 133), osteonecrosis (n = 151), the presence of excessive intraosseous lymphocyte infiltration (n = 11), and interface hyperosteoidosis (n = 30). Logistic regression analysis was performed both unadjusted and after adjustment for sex, age, the size of the femoral component, and preoperative clinical diagnosis.
Femoral remnants from female patients had a smaller OR for fracture (adjusted OR: 0.29, 95% CI 0.11, 0.80, P for difference = 0.02) and for the presence of osteonecrosis (adjusted OR: 0.16, 95% CI 0.04, 0.63, P for difference = 0.01). However, women had a higher OR for both the presence of excessive intraosseous lymphocyte infiltration (adjusted OR: 10.22, 95% CI 0.79, 132.57, P for difference = 0.08) and interface hyperosteoidosis (adjusted OR: 4.19, 95% CI 1.14, 15.38, P for difference = 0.03).
Within the limitations of this study, we demonstrated substantial sex differences in distinct failure patterns of metal-on-metal hip resurfacing. Recognition of pathogenically distinct failure modes will enable further stratification of risk factors for certain failure mechanisms and thus affect future therapeutic options for selected patient groups.
PMCID: PMC3204242  PMID: 21992554
12.  Poor outcome of revised resurfacing hip arthroplasty 
Acta Orthopaedica  2010;81(1):72-76.
Background and purpose
Recent years have seen a rapid increase in the use of resurfacing hip arthroplasty despite the lack of literature on the long-term outcome. In particular, there is little evidence regarding the outcome of revisions of primary resurfacing. The purpose of this analysis was to examine the survivorship of primary resurfacing hip arthroplasties that have been revised.
Patients and methods
Over 12,000 primary resurfacing hip arthroplasties were recorded by the Australian Orthopaedic Association National Joint Replacement Registry between September 1, 1999 and December 31, 2008. During this time, 397 revisions for reasons other than infection were reported for these primary resurfacings and classified as acetabular, femoral, or both acetabular and femoral revisions. The survivorship of the different types of revisions was estimated using the Kaplan-Meier method and compared using proportional hazard models. Additionally, the outcome of a femoral-only revision was compared to that of primary conventional total hip arthroplasty.
Acetabular-only revision had a high risk of re-revision compared to femoral-only and both acetabular and femoral revision (5-year cumulative per cent revision of 20%, 7%, and 5% respectively). Femoral-only revision had a risk of re-revision similar to that of revision of both the acetabular and femoral components. Femoral-only revision had over twice the risk of revision of primary conventional total hip arthroplasty.
Revision of a primary resurfacing arthroplasty is associated with a major risk of re-revision. The best outcome is achieved when either the femoral-only or both the acetabular and femoral components are revised. Technically straightforward femoral-only revisions generally have a worse outcome than a primary conventional total hip arthroplasty.
PMCID: PMC2856207  PMID: 20170416
13.  Femoral Resurfacing in Young Patients with Hematologic Cancer and Osteonecrosis 
Resurfacing hemiarthroplasties were performed to treat advanced osteonecrosis of 20 femoral heads in 14 patients (median age, 19.8 years; range, 15.1–27.4 years), treated for hematologic cancer in childhood or adolescence. Seven hips in five patients were revised to total hip arthroplasties (THA) because of pain; three of these showed radiographic loosening of the femoral head resurfacing component. The median time from resurfacing to revision was 2.4 years (range, 0.9–4.8 years). Marginal Cox-regression analysis, adjusting for correlations owing to bilateral involvement, showed positive association of revision-free survival of the prosthesis with patient’s age; time from resurfacing to the end of anticancer therapy, end of glucocorticosteroid therapy; percentage of joint space at the last radiograph; and size of the lesion has a negative association with revision-free survival. Because of this study’s exploratory nature, p values were not adjusted for the number of statistical comparisons. Among 14 patients, the probability of not requiring resurfacing prosthesis revision was 66% (SE, ±15%; 95% CI, 44%–100%) at 3 years. Osteonecrosis of the femoral head in young patients treated for hematologic cancer in childhood or adolescence poses a serious challenge to the orthopaedic surgeon. The data of this preliminary study suggest that in selected patients resurfacing hemiarthroplasty may delay the need for THA for 3–7 years.
Level of Evidence: Level II, prognostic study. See the Guidelines for Authors for a complete description of levels of evidence.
PMCID: PMC2628217  PMID: 18679763
14.  Do the Potential Benefits of Metal-on-Metal Hip Resurfacing Justify the Increased Cost and Risk of Complications? 
Metal-on-metal hip resurfacing arthroplasty (MoM HRA) may offer potential advantages over total hip arthroplasty (THA) for certain patients with advanced osteoarthritis of the hip. However, the cost effectiveness of MoM HRA compared with THA is unclear.
The purpose of this study was to compare the clinical effectiveness and cost-effectiveness of MoM HRA to THA.
A Markov decision model was constructed to compare the quality-adjusted life-years (QALYs) and costs associated with HRA versus THA from the healthcare system perspective over a 30-year time horizon. We performed sensitivity analyses to evaluate the impact of patient characteristics, clinical outcome probabilities, quality of life and costs on the discounted incremental costs, incremental clinical effectiveness, and the incremental cost-effectiveness ratio (ICER) of HRA compared to THA.
MoM HRA was associated with modest improvements in QALYs at a small incremental cost, and had an ICER less than $50,000 per QALY gained for men younger than 65 and for women younger than 55. MoM HRA and THA failure rates, device costs, and the difference in quality of life after conversion from HRA to THA compared to primary THA had the largest impact on costs and quality of life.
MoM HRA could be clinically advantageous and cost-effective in younger men and women. Further research on the comparative effectiveness of MoM HRA versus THA should include assessments of the quality of life and resource use in addition to the clinical outcomes associated with both procedures.
Level of Evidence
Level I, economic and decision analysis. See Guidelines for Authors for a complete description of levels of evidence.
PMCID: PMC2914258  PMID: 20232182
15.  Do the Potential Benefits of Metal-on-Metal Hip Resurfacing Justify the Increased Cost and Risk of Complications? 
Metal-on-metal hip resurfacing arthroplasty (MoM HRA) may offer potential advantages over total hip arthroplasty (THA) for certain patients with advanced osteoarthritis of the hip. However, the cost effectiveness of MoM HRA compared with THA is unclear.
The purpose of this study was to compare the clinical effectiveness and cost-effectiveness of MoM HRA to THA.
A Markov decision model was constructed to compare the quality-adjusted life-years (QALYs) and costs associated with HRA versus THA from the healthcare system perspective over a 30-year time horizon. We performed sensitivity analyses to evaluate the impact of patient characteristics, clinical outcome probabilities, quality of life and costs on the discounted incremental costs, incremental clinical effectiveness, and the incremental cost-effectiveness ratio (ICER) of HRA compared to THA.
MoM HRA was associated with modest improvements in QALYs at a small incremental cost, and had an ICER less than $50,000 per QALY gained for men younger than 65 and for women younger than 55. MoM HRA and THA failure rates, device costs, and the difference in quality of life after conversion from HRA to THA compared to primary THA had the largest impact on costs and quality of life.
MoM HRA could be clinically advantageous and cost-effective in younger men and women. Further research on the comparative effectiveness of MoM HRA versus THA should include assessments of the quality of life and resource use in addition to the clinical outcomes associated with both procedures.
Level of Evidence
Level I, economic and decision analysis. See Guidelines for Authors for a complete description of levels of evidence.
PMCID: PMC2914258  PMID: 20232182
16.  A Cost-effectiveness Analysis of the Arthroplasty Options for Displaced Femoral Neck Fractures in the Active, Healthy, Elderly Population 
The Journal of arthroplasty  2008;24(6):854-860.
This study was performed to explore the cost-effectiveness of total hip replacement compared with hemiarthroplasty in the treatment of displaced femoral neck fractures in active otherwise healthy older patients in whom the optimum treatment is believed to be an arthroplasty procedure.
A Markov decision model was used to determine whether total hip arthroplasty or hemiarthroplasty was most cost-effective for the management of a displaced femoral neck fracture in this patient population.
Total hip arthroplasty was associated with an average cost $3,000 more than hemiarthroplasty, and the average quality-adjusted life year gain was 1.53. The incremental cost-effectiveness ratio associated with the total hip replacement treatment strategy is $1960 per quality-adjusted life-year.
Currently available data support the use of total hip arthroplasty as the more cost-effective treatment strategy in this specific population. The increased upfront cost appears to be offset by the improved functional results when compared with hemiarthroplasty in this select patient group.
PMCID: PMC2876817  PMID: 18701245
17.  Hip resurfacing in patients under thirty years old: an attractive option for young and active patients 
International Orthopaedics  2012;36(9):1789-1794.
Metal-on-metal hip resurfacing is offered as an alternative to traditional hip arthroplasty for young, active adults with advanced osteoarthritis. The concept of hip resurfacing is considered very attractive for this specific population (hard-on-hard bearing component with a large femoral head limiting the risk of dislocation, and allowing femoral bone stock preservation).
A prospective clinical trial was designed to investigate the outcome of hip resurfacing in young patients (under 30 years old). We studied 24 hips in 22 patients. Mean age at operation was 24.9 years (range 17.1–29.9). No patient was lost to follow-up.
There was no revision at average follow-up of 50.6 months (44–59). Mean UCLA activity score improved from 5.5 (1–9) pre-operatively to 7.6 (1–10) postoperatively (p < 0.001). Mean Harris hip score increased from 43.9 (19–67) to 89.3 (55–100) (p < 0.001). Radiological analysis discerned no osteolysis and no implant migration.
The absence of short-term complications, such as mechanical failure or dislocation, is encouraging and leads us to think that mid-term results will be satisfactory. Moreover, the specific advantages of hip resurfacing (bone stock preservation, excellent stability, low risk of dislocation, large-diameter head) make the procedure a very attractive option for young subjects.
PMCID: PMC3427443  PMID: 22576079
18.  Prospective Study Comparing Functional Outcomes and Revision Rates Between Hip Resurfacing and Total Hip Arthroplasty: Preliminary Results for 2 Years 
Orthopedic Reviews  2013;5(3):e20.
There is a need of independent prospective studies about modern generation of hip resurfacing implants. The aim of this propective observational study was to compare the functional outcomes and revision rates with hip resurfacing arthroplasty and total hip arthroplasty and to present the preliminary results at 2 years. Patients included were recruited prospectively in the Partial Pelvic Replacement Hip Project by a single surgeon between January 2007 and January 2010. Patients were assessed with the Harris Hip Score (HHS) and Postel-Merle d’Aubigné (MDA) score and Devane Score. The end point of the study was reoperation for any cause related to the prosthesis. At a mean follow up of 38.6 months there were a total of 142 patients with hip resurfacing (group 1) [100 Durom® (Zimmer Inc., Warsaw, IN, USA) and 42 Birmingham Hip Resurfacing® (Smith & Nephew, Memphis, TN, USA)] and 278 patients with total hip arthroplasty (group 2). The results showed significantly greater gain of HHS, MDA and Devane score with hip resurfacing procedures. However, considering all the complications, the rate was significantly higher in group 16.4% vs 1.79% in group 2 (P<0.0001). In group 1 we observed 6 complications only concerned males with Durom® implants. The follow up of this cohort is still on going and may deliver more information on the evolution of these results in time.
PMCID: PMC3808795  PMID: 24191180
hip resurfacing; total hip arthroplasty; outcomes
19.  Bone mineral density in the femoral neck increases after hip resurfacing: a cohort with five-year follow-up 
International Orthopaedics  2010;35(9):1303-1307.
Hip resurfacing is an effective treatment modality for arthritis of the hip in carefully selected patients; however, its use remains controversial due to its higher revision rates compared with conventional total hip replacement surgery. The most frequent reason for revision is femoral neck fracture, and preoperative bone mineral density is an important factor when considering the option of hip resurfacing. Whilst reduction in bone mineral density following total hip replacement is well documented, little is known about the long-term changes in femoral neck bone mineral density after hip resurfacing. We followed 15 patients (ten male and five female) who underwent unilateral hip resurfacing for osteoarthritis with standardised dual energy X-ray absorbiometry scans at two weeks, three months, one year, two years and five years postoperatively to determine changes in the femoral neck bone mineral density. Both males and females initially had decreases in bone mineral density at three months postoperatively, but had gradual mean increases to 119% of their initial measurements by five years. This study demonstrates that femoral neck bone mineral density increases after hip resurfacing and that this increase continues for at least five years.
PMCID: PMC3167457  PMID: 20730585
20.  Surface Replacement of the Hip Can Result in Decreased Acetabular Bone Stock 
The recent interest in hip resurfacing arthroplasty is motivated by its potential advantages over THA. One advantage of hip resurfacing arthroplasty is that it conserves bone on the femoral side; however, it is unclear whether it does so on the acetabular side.
We determined whether the amount of acetabular reaming and acetabular bone removal required for hip resurfacing arthroplasty is equal to, less than, or greater than that for THA.
Patients and Methods
We prospectively evaluated the femoral neck size of 180 hips at the time of primary THA in an identical manner to when carrying out a hip resurfacing arthroplasty. Based on the femoral neck measurement, we determined the minimum cup size that would be used and reamer size required if the hip was undergoing a resurfacing. We compared this to the reamer size actually required to prepare the acetabulum for the THA cup. We calculated the difference between the predicted reaming size for resurfacing and the actual reaming size to determine the effect of resurfacing on acetabular bone stock.
Overall, 71%, 57%, and 41% of THAs would have had extra acetabular bone removed to implant a hip resurfacing arthroplasty cup with a line-to-line (0-mm), 1-mm, or 2-mm press fit, respectively.
When compared to THA, hip resurfacing arthroplasty commonly results in additional acetabular bone resection.
PMCID: PMC3254745  PMID: 21858642
21.  The Prevalence of Groin Pain After Metal-on-Metal Total Hip Arthroplasty and Total Hip Resurfacing 
Groin pain after total hip arthroplasty (THA) or total hip resurfacing arthroplasty can be troubling for patients and surgeons. Potential sources of pain include infection, loosening, metal hypersensitivity, or impingement of bony structures or the iliopsoas tendon.
We compared the rate of groin pain after THA or hip resurfacing using metal-on-metal to those of other bearing surfaces.
We identified 347 (334 patients) primary total hip (n = 301) or resurfacing (n = 46) arthroplasties. Complete preoperative, operative, and postoperative data were available for 282 hips. We retrospectively reviewed the charts for the presence or absence of groin pain at a minimum of 1 year after surgery with a specific focus on etiologic factors. The minimum followup was 12 months (mean, 14 months; range 12 to 24 months).
The rate of groin pain was 7% (15 of 217 patients) after THA with conventional bearing surfaces, 15% (4 of 26 patients) with metal-on-metal THA and 18% (7 of 39 patients) with total hip resurfacing. Younger patients were more likely to report groin pain postoperatively and more likely to have metal-on-metal bearing surfaces.
Our data at short-term followup suggest increased rates of groin pain after metal-on-metal THA or resurfacing arthroplasty versus THA using polyethylene or ceramic bearing surfaces. The reasons are not clear but they appear to be associated with younger age. Potential factors include impingement, activity level and possibly higher expectations for patients receiving metal-on-metal bearing surfaces that may make those patients more likely to report postoperative pain.
Level of Evidence
Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
PMCID: PMC2919872  PMID: 20425538
22.  Two-year migration results of the ReCap hip resurfacing system—a radiostereometric follow-up study of 23 hips 
International Orthopaedics  2010;35(4):497-502.
There has been renewed interest for metal-on-metal hip resurfacing due to improved design and manufacturing of implants, better materials, and enhanced implant fixation. In contrast to conventional total hip replacements, only a few clinical hip resurfacing trials using radiostereometry (RSA) have been reported, and solely for the Birmingham hip resurfacing arthroplasty. The purpose of this RSA trial was to describe the migration pattern of a new hip resurfacing system (ReCap) within the first two years after primary surgery. Twenty-six patients underwent total hip replacement. The patients were followed-up for up to 24 months and were evaluated with the use of radiostereometric measurements. The prosthesis showed mean translations and rotation close to zero. Maximum translation was seen along the transverse axis in the medial direction (0.13 mm). No statistically significant translation or rotation was seen at two-years follow-up, (t-test, p <0.05, translation or rotation).
PMCID: PMC3066327  PMID: 20195597
23.  Patient characteristics affecting the prognosis of total hip and knee joint arthroplasty: a systematic review 
Canadian Journal of Surgery  2008;51(6):428-436.
Total joint arthroplasty is a highly efficacious and cost-effective procedure for moderate to severe arthritis in the hip and knee. Although patient characteristics are considered to be important determinants of who receives total joint arthroplasty, no systematic review has addressed how they affect the outcomes of total joint arthroplasty. This study addresses how patient characteristics influence the outcomes of hip and knee arthroplasty in patients with osteoarthritis.
We searched 4 bibliographic databases (MEDLINE 1980–2001, CINAHL 1982–2001, EMBASE 1980–2001, HealthStar 1998–1999) for studies involving more than 500 patients with osteoarthritis and 1 or more of the following outcomes after total joint arthroplasty: pain, physical function, postoperative complications (short-and long-term) and time to revision. Prognostic patient characteristics of interest included age, sex, race, body weight, socioeconomic status and work status.
Sixty-four of 14 276 studies were eligible for inclusion and had extractable data. Younger age (variably defined) and male sex increased the risk of revision 3-fold to 5-fold for hip and knee arthroplasty. The influence of weight on the risk of revision was contradictory. Mortality was greatest in the oldest age group and among men. Function for older patients was worse after hip arthroplasty (particularly in women). Function after knee arthroplasty was worse for obese patients.
Although further research is required, our findings suggest that, after total joint arthroplasty, younger age and male sex are associated with increased risk of revision, older age and male sex are associated with increased risk of mortality, older age is related to worse function (particularly among women), and age and sex do not influence the outcome of pain. Despite these findings, all subgroups derived benefit from total joint arthroplasty, suggesting that surgeons should not restrict access to these procedures based on patient characteristics. In addition, future research needs to provide standardized measures of outcomes.
PMCID: PMC2592576  PMID: 19057730
24.  Metal on metal hip resurfacing versus uncemented custom total hip replacement - early results 
There is no current consensus on the most appropriate prosthesis for treating symptomatic osteoarthritis (OA) of the hip in young, active patients. Modern metal on metal hip resurfacing arthroplasty (HR) has gained popularity as it is theoretically more stable, bone conserving and easier to revise than total hip arthroplasty. Early results of metal on metal resurfacing have been encouraging. We have compared two well matched cohorts of patients with regard to function, pain relief and patient satisfaction.
This prospective study compares 2 cohorts of young, active patients treated with hip resurfacing (137 patients, 141 hips) and custom uncemented (CADCAM) stems (134 patients, 141 hips). All procedures were performed by a single surgeon. Outcome measures included Oxford, WOMAC and Harris hip scores as well as an activity score. Statistical analysis was performed using the unpaired student's t-test.
One hundred and thirty four and 137 patients were included in the hip replacement and resurfacing groups respectively. The mean age of these patients was 54.6 years. The mean duration of follow up for the hip resurfacing group was 19.2 months compared to 13.4 months for the total hip replacement group.
Pre operative oxford, Harris and WOMAC scores in the THA group were 41.1, 46.4 and 50.9 respectively while the post operative scores were 14.8, 95.8 and 5.0. In the HR group, pre- operative scores were 37.0, 54.1 and 45.9 respectively compared to 15.0, 96.8 and 6.1 post operatively. The degree of improvement was similar in both groups.
There was no significant clinical difference between the patients treated with hip resurfacing and total hip arthroplasty in the short term.
PMCID: PMC2831868  PMID: 20167056
25.  Patients Report Improvement in Quality of Life and Satisfaction After Hip Resurfacing Arthroplasty 
A number of reconstructive procedures are available for the management of hip osteoarthritis. Hip resurfacing arthroplasty is now an accepted procedure, with implant survivorship comparable to THA at up to 10 years’ followup in certain series. Most reports focus on implant survivorship, surgeon-derived results, or complications. Fewer data pertain to patient-reported results, including validated measures of quality of life (QoL) and satisfaction and baseline measures from which to determine magnitude of improvement. Validated patient-reported results are essential to guide patients and surgeons in the current era of informed and shared decision making.
We determined whether patients reported improvement in disease-specific, joint-specific, and generic QoL after hip resurfacing arthroplasty; whether patients were satisfied with the results of the procedure; and latest activity level and return to sport.
We retrospectively reviewed 127 patients (100 men, 27 women) who underwent 143 hip resurfacing procedures between 2002 and 2006. Mean patient age was 52 years. Patients completed the WOMAC, Oxford Hip Score, and SF-12 at baseline and again at minimum 2-year followup (mean, 2.5 years; range, 2–6 years). At latest followup, patients completed a validated satisfaction questionnaire and UCLA activity score.
All QoL scores improved (normalized to a 0–100 scale, where 100 = best health state). WOMAC improved from 46 to 95, Oxford Hip Score from 42 to 95, SF-12 (physical) from 34 to 54, and SF-12 (mental) from 46 to 56. Patient satisfaction score was 96. UCLA activity score was 8.
The majority of patients reported improvement in QoL, were very satisfied with their outcome, and returned to a high level of activity after hip resurfacing arthroplasty.
Level of Evidence
Level IV, therapeutic study. See the Instructions for Authors for a complete description of levels of evidence.
PMCID: PMC3549167  PMID: 23076552

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