A randomised study comparing resection of acetabular bone at resurfacing and total hip replacement

A systematic review of modern metal-on-metal total hip resurfacing vs standard total hip arthroplasty in active young patients

This systematic review compared 2 treatments for hip disease in active young patients: modern metal-on-metal total hip resurfacing and standard total hip arthroplasty. We conducted a literature search to identify relevant randomized and clinical controlled trials and included 968 patients from 4 trials in our analysis. Our results indicated increased rates of revision, femoral neck fractures, and component loosening among patients who received modern metal-on-metal hip resurfacing. No significant differences in the rates of mortality, dislocation, or deep hip joint infection were found between treatment groups. Hip function scores were similar between the 2 groups, but the resurfacing group showed higher activity levels. These results have provided insufficient evidence to determine whether modern metal-on-metal total hip resurfacing offers clinical advantages over standard total hip arthroplasty.

Risk factors for revision of hip arthroplasties in patients younger than 30 years

BACKGROUND

Numerous reports of THAs in patients younger than 30 years indicate a high risk of revision. Although risk factors for revision have been reported for older patients, it is unclear whether these risk factors are the same as those for patients younger than 30 years.

QUESTIONS/PURPOSES

We therefore (1) determined function and survivorship of revision THAs performed in patients younger than 30 years, and (2) assessed the risk factors for revision THAs in this younger population by comparison with a group of patients younger than 30 years who did not undergo revision.

PATIENTS AND METHODS

We retrospectively reviewed the clinical records and radiographs of 55 patients younger than 30 years (average age at revision, 24.3 years; range, 14-30 years) who underwent 77 hip revisions. Revision was performed, on average, 4.6 years (range, 0.4-12 years) after the primary THA. The results for these 55 patients (77 revision THAs) were compared with results for a nonrevised group, including 819 THAs in patients younger than 30 years. Minimum followup of the revision group was 1 year (mean, 6.2 years; range, 1-15 years).

RESULTS

At followup after the revision, the Merle d'Aubigné-Postel score improved from 12.2 to 14.6. The rates of dislocation, neurologic lesions, and fractures were 15%, 7.8%, and 14%, respectively. The 10-year survival rate was 36% (95% confidence interval [CI], 21%-51%). Compared with the nonrevised group, the independent revision risk factors were young age at primary THA (OR 1.14 [1.07-1.19]), high number of previous surgeries (OR 5.41 [2.67-10.98]), and occurrence of at least one dislocation (OR 3.98 [1.74-9.07]). Hard-on-soft bearings had a higher risk (OR 3.42 [1.91-6.1]) of revision compared with hard-on-hard bearings.

CONCLUSIONS

Revision THAs are likely in patients younger than 30 years, and the complication rate is high. The survivorship of hip revision in this population is low and alternative solutions should be advocated whenever possible.

LEVEL OF EVIDENCE

Level III, therapeutic study, case control study. See the Guidelines for Authors for a complete description of levels of evidence.

Complications after metal-on-metal hip resurfacing arthroplasty

This article determines the incidence and cause of the complications commonly associated with metal-on-metal hip resurfacing implants and the proposed methods to prevent these complications. The literature available in PubMed was reviewed. Complication rates after hip resurfacing are low, and the procedure has shown both safety and efficacy in the hands of surgeons trained in specialized centers. Proper surgical technique can further reduce the incidence of femoral neck fracture, component loosening, and abnormal wear of the prosthesis. A more systematic detection of adverse local tissue reactions is needed to provide accurate assessments of their prevalence.

Range of motion of large head total hip arthroplasty is greater than 28 mm total hip arthroplasty or hip resurfacing

BACKGROUND

Reduced range of motion of the hip has a detrimental influence on lower limb function. Large diameter head total hip arthroplasty may theoretically have a greater potential for restoring normal hip range of motion due to greater head-neck diameter ratio, and hence provide better function compared to conventional or hip resurfacing arthroplasty.

METHOD

At minimum one year follow-up, range of motion of the operated and contra lateral hips was clinically assessed using digital photographs and bony landmarks in a clinical comparative study. We assessed if 1) large diameter head total hip arthroplasty (55 patients) restores better hip range of motion compared to 28 mm total hip arthroplasty (50 patients) or hip resurfacing (60 patients) 2) large diameter head total hip arthroplasty achieves same hip range of motion as contra lateral normal hips and 3) hip range of motion correlates with the WOMAC score.

FINDINGS

The large diameter head total hip arthroplasty group had significantly greater total arcs of motion (approximately 20°), mostly due to an increase of hip flexion and external rotation, but did not reach normal hip motion. The hip range of motion showed significant correlation with the WOMAC score, especially the flexion arc.

INTERPRETATION

The better hip range of motion of large diameter head total hip arthroplasty is likely due to the greater head to neck diameter ratio and hence seems to be the best option to optimize range of hip motion and improve function after hip arthroplasty.

Birmingham hip resurfacing: a minimum follow-up of ten years

We report the survival, radiological and functional outcomes of a single surgeon series of his first 144 consecutive Birmingham hip resurfacing procedures (130 patients) at a minimum of ten years. There were ten revisions during this time. Although no patients were lost to follow-up some did not complete the scoring assessment or undergo radiological assessment at ten years. The ten-year survival for male patients was 98.0% (95% confidence interval 95.2 to 100). The ten-year survival for the total cohort with aseptic revision as the endpoint was 95.5% (95% confidence interval 91.8 to 99.0) and including revisions for sepsis was 93.5% (95% confidence interval 89.2 to 97.6). The median modified Oxford hip score at ten years was 4.2% (interquartile range 0 to 19) and the median University of California, Los Angeles score was 7.0 (interquartile range 5.0 to 8.0). This study confirms the midterm reports that metal-on-metal hip resurfacing using the Birmingham Hip provides a durable alternative to total hip replacement, particularly in younger male patients wishing to maintain a high level of function, with low risk of revision for at least ten years.

Metal-on-metal hip resurfacing: a critical review

In this article, a concise review of the current literature on metal-on-metal hip resurfacing (MoMHR) is given. In contrast to conventional total hip arthroplasty, older age, female sex and small femoral head sizes predispose to failure. Neck fracture and metal wear-related complications account for the most frequent reasons for re-operations. Although the long-term consequences of metal ion release remain unknown, the increasing prevalence of soft tissue related problems with potentially devastating functional consequences in this younger patient group are of concern. Outcome after revision for metal wear related failure of MoMHR is poor. In our opinion, patients with this device should be managed in dedicated centers with facilities for data collection and monitoring. The majority of proposed advantages of MoMHR cannot be supported by the published evidence.

Resurfacing registers concern

We review the history and literature of hip resurfacing arthroplasty. Resurfacing and the science behind it continues to evolve. Recent results, particularly from the national arthroplasty registers, have spread disquiet among both surgeons and patients. A hip resurfacing arthroplasty is not a total hip replacement, but should perhaps be seen as a means of delaying it. The time when hip resurfacing is offered to a patient may be different from that for a total hip replacement. The same logic can apply to the timing of revision surgery. Consequently, the comparison of resurfacing with total hip replacement may be a false one. Nevertheless, the need for innovative solutions for young arthroplasty patients is clear. Total hip replacement can be usefully delayed in many of these patients by the use of hip resurfacing arthroplasty.

The clinical and radiological outcomes of hip resurfacing versus total hip arthroplasty: a meta-analysis and systematic review

BACKGROUND AND PURPOSE

Hip resurfacing (HRS) procedures have gained increasing popularity for younger, higher-demand patients with degenerative hip pathologies. However, with concerns regarding revision rates and possible adverse metal hypersensitivity reactions with metal-on-metal articulations, some authors have questioned the hypothesized superiority of hip resurfacing over total hip arthroplasty (THA). In this meta-analysis, we compared the clinical and radiological outcomes and complication rates of these 2 procedures.

METHODS

A systematic review was undertaken of all published (Medline, CINAHL, AMED, EMBASE) and unpublished or gray literature research databases up to January 2010. Clinical and radiological outcomes as well as complications of HRS were compared to those of THA using risk ratio, mean difference, and standardized mean difference statistics. Studies were critically appraised using the CASP appraisal tool.

RESULTS

46 studies were identified from 1,124 citations. These included 3,799 HRSs and 3,282 THAs. On meta-analysis, functional outcomes for subjects following HRS were better than or the same as for subjects with a THA, but there were statistically significantly greater incidences of heterotopic ossification, aseptic loosening, and revision surgery with HRS compared to THA. The evidence base showed a number of methodological inadequacies such as the limited use of power calculations and poor or absent blinding of both patients and assessors, possibly giving rise to assessor bias.

INTERPRETATION

On the basis of the current evidence base, HRS may have better functional outcomes than THA, but the increased risks of heterotopic ossification, aseptic loosening, and revision surgery following HRS indicate that THA is superior in terms of implant survival.

Femoral-head vascularity after hip surface arthroplasty

BACKGROUND

iatrogenic devascularization of the femoral head is as an area of concern following hip resurfacing arthroplasty, with probable implications on short-term failure and long-term survival of the implant.

MATERIALS AND METHODS

we assessed the vascularity of 25 resurfaced femoral heads in 20 patients by comparison with preoperative and postoperative Tc-99m methylene diphosphonate (MDP) bone scintigraphy images, the postoperative scans being done 9 months after the surgery.

RESULTS

eight out of 25 hips (32%) showed <55% of their preoperative uptake at a mean of 9 months after surgery and were categorized as showing reduced vascularity.

CONCLUSION

our study reveals reduction in vascularity of the femoral-head remnant as a frequent occurrence after hip resurfacing. Our study also highlights the role of bone scintigraphy as tool in assessing the vascularity of resurfaced femoral heads.

Cortical strut allograft as an adjunct to plate fixation for periprosthetic fractures of the femur

The use of cortical strut allografts in the treatment of periprosthetic femoral fractures remain controversial. Complications such as infection and the potential transmission of disease remain concerns. A retrospective review at a tertiary-care hospital was completed of 21 patients who had sustained a periprosthetic femoral fracture and who were treated using a plate and a deep-frozen cortical strut allograft, between 1996 and 2007. The average age at the time of surgery was 80.3 years old and included 16 women and 5 men. Three patients were lost to follow-up and four died within a few weeks of discharge. The remaining 14 patients were evaluated clinically and radiographically with a mean follow-up of 3.2 years. Fracture union was observed in 13 patients, and integration of the graft occurred in 12 patients. One of the 14 patients developed a deep infection with Coagulase-Negative Staphylococcus, with a satisfactory outcome after surgical debridement and antibiotic treatment. There were no cases of fixation failure or plate rupture. At the final evaluation, the mean EQ-5D VAS score was 64 (ranging from 40-90 points) and the mean EQ-5D health state index adapted to Spanish value sets was 0.57. The mean Oxford Hip Score was 31.2. The results support the use of cortical allograft for these fractures to increase the likelihood of fracture healing and to improve the bone stock. We consider that cortical strut grafting is specially indicated for B1 and C fractures in which decreased bone density is present.

A comparison of clinical results of hip resurfacing arthroplasty and 28 mm metal on metal total hip arthroplasty: a randomised trial with 3-6 years follow-up

Two hundred and nine hips were randomised to receive either a 28 mm total hip athroplasty (THA, 100 hips) or hybrid hip resurfacing (HR, 109 hips). At 1 and 2 years post-operatively, patients with HR achieved statistically significantly better WOMAC functional scores. However, differences in scores were of slight clinical relevance with a difference of 2.2/100 and 3.3/100, at 1 and 2 years respectively (p=0.007). After an average follow-up of 56 months (range 36-72) there were similar re-operation rates 7/100 THA and 6/109 HR (p=0.655) and revision rates 2/100 THA and 4/109 HR (p=0.470). However, the types of complications were different. Higher early aseptic loosening rate was found in HR and long-term survival analysis of both patient cohorts is necessary to determine whether the potential bone preservation advantage offers by HR will overcome its earlier higher failure rate.

Assessment of accuracy and reliability in preoperative templating for hip resurfacing arthroplasty

The current study investigated the accuracy and reliability of hip resurfacing component selection based on digital preoperative templating. Four surgeons made a template of preoperative radiographs on 2 occasions for acetabular and femoral components in 50 randomly selected hip resurfacing patients. Component selection reliability was variable among surgeons (kappa = 0.16-0.73) and fair between surgeons (kappa = 0.23-0.32). The average percentage of agreement for the acetabular component was 47% (range, 32%-64%) and for the femoral component was 54% (range, 38%-70%). Surgeons tended to underestimate implant size if the correct implant was not chosen (acetabular, 29%; femoral, 32%). Selection of an undersized femoral component may lead to femoral neck notching or varus implant alignment. This study emphasizes the need for intraoperative verification of preoperative templating results to ensure optimal implant selection in hip resurfacing.

Hip resurfacing arthroplasty: a review of the evidence for surgical technique, outcome, and complications

Hip resurfacing arthroplasty has reemerged as a valid reconstruction option for the osteoarthritic hip. Patient selection is critical for excellent surgical outcomes, especially when compared with total hip arthroplasty. However, concerns regarding surgical technique and postsurgical complications persist. The authors review the evidence for surgical technique, outcomes, and complications related to modern metal-on-metal hip resurfacing arthroplasty.

Radiographic assessment of biomechanical parameters following hip resurfacing and cemented total hip arthroplasty

Resurfacing hip arthroplasty and total hip replacement both aim to restore anatomical parameters.Leg length and offset discrepancy can result in altered joint reaction forces, and are associated with increased wear, dislocation, and decreased patient satisfaction. This study assesses the accuracy of leg length and offset restoration after either a Birmingham Hip Resurfacing (BHR) or a cemented total hip replacement (THR).Standardised antero-posterior radiography was performed on two groups of 30 patients with unilateral primary osteoarthritis undergoing either a cemented total hip or resurfacing. The normal contra-lateral hip was used as the control. Leg length and offset were measured pre-operatively with no significant difference between the two groups.Cup offset, femoral offset, total offset and leg length of the prosthesis and normal side were measured by two observers and mean measurements were analysed by a paired t test.Leg lengths in each group did not differ significantly from the normal side, THR 0.53 mm (95% CI -2.4 to 3.4 mm) but BHR implantation did result in mean leg shortening of -1.9 mm (95% CI -4.5 mm to 0.6mm). Cup offset differed significantly from normal anatomy in both groups, as did femoral and total offset for the total hip replacement group. However, femoral offset was restored in the Birmingham resurfacing group. When the THR group was compared against the BHR group we found no difference between restoration of leg lengths (p = 0.21) and cup offset (p = 0.30) but femoral (p = 0.0063) and total offset (p = 0.03) were restored more accurately with a BHR.

Resurfacing and uncemented arthroplasty for young hip arthritis: functional outcomes at 5 years

The management of osteoarthritis of the hip in young active patients is challenging. We compared the functional outcomes and activity levels following hip resurfacing and uncemented THA in young active patients matched for age, gender and activity levels. Mean follow-up period was five years (4-7 years). Within each group there was a statistically significant improvement in the mean University of California at Los Angeles (UCLA) and Oxford Hip Score (OHS) scores following surgery. This study found no statistically significant difference in the levels of function (p= 0.82) or activity pursued (p= 0.60) after surgery between uncemented THA and hip resurfacing. The potential complications unique to hip resurfacing may be avoided by the use of uncemented THA which in itself has longer follow-up compared to resurfacing.

Comparison of bone removed during total hip arthroplasty with a resurfacing or conventional femoral component: a cadaveric study

We sought to examine the amount of bone removed during total hip arthroplasty with a resurfacing femoral component, compared to with a conventional, stemmed femoral component, by using 6 male and 4 female cadaveric pelves with attached bilateral proximal femora. Using randomized assignment and order, a total hip arthroplasty with a resurfacing femoral implant was performed on one side, and total hip arthroplasty with a cementless, stemmed femoral implant was performed on the contralateral side. The relationship between native femoral head diameter and the implanted acetabular socket was on average within 2 mm for both procedures. No significant difference was observed in the amount of acetabular bone removed (9.8 g for hip resurfacing vs 8.8 g). However, a resurfacing component resulted in approximated 3 x less bone removal from the femur (25.8 g vs 75.1 g). This study shows that the preservation of femoral bone with a resurfacing femoral component does not result in an increased removal of acetabular bone when compared to the use of a conventional, stemmed femoral component.

The John Charnley Award: The functional outcome of hip resurfacing and large-head THA is the same: a randomized, double-blind study

Better functional outcome is believed by some to occur after hip resurfacing (HR) than conventional 28-mm total hip arthroplasty (THA) in young and active patients with hip osteoarthritis. However, the postulated superior outcome of HR over THA may simply be the result of a bias in patient selection or the use of a larger femoral head. We therefore asked whether HR would demonstrate superior functional outcome when compared with a THA with a large-diameter femoral head in a randomized, double-blind study. Gait speed and postural balance evaluations, functional tests, and clinical data were analyzed preoperatively and at 3, 6, and 12 months after surgery. Gait speed was used as the primary outcome measure. Forty-eight patients were randomized in the study and a third group of 14 healthy subjects served as controls. The gait speed and postural balance evaluations, the performance at most functional tests, and clinical scores were similar in HR and large-head THA groups at each followup period. The operated patients reached most control group values at 3 months postoperatively. By these measures, HR did not provide better clinical function over large-head THA.

LEVEL OF EVIDENCE

Level I, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Metal ion release from bearing wear and corrosion with 28 mm and large-diameter metal-on-metal bearing articulations: a follow-up study

We have updated our previous randomised controlled trial comparing release of chromium (Cr) and cobalt (Co) ions and included levels of titanium (Ti) ions. We have compared the findings from 28 mm metal-on-metal total hip replacement, performed using titanium CLS/Spotorno femoral components and titanium AlloFit acetabular components with Metasul bearings, with Durom hip resurfacing using a Metasul articulation or bearing and a titanium plasma-sprayed coating for fixation of the acetabular component. Although significantly higher blood ion levels of Cr and Co were observed at three months in the resurfaced group than in total hip replacement, no significant difference was found at two years post-operatively for Cr, 1.58 microg/L and 1.62 microg/L respectively (p = 0.819) and for Co, 0.67 microg/L and 0.94 microg/L respectively (p = 0.207). A steady state was reached at one year in the resurfaced group and after three months in the total hip replacement group. Interestingly, Ti, which is not part of the bearing surfaces with its release resulting from metal corrosion, had significantly elevated ion levels after implantation in both groups. The hip resurfacing group had significantly higher Ti levels than the total hip replacement group for all periods of follow-up. At two years the mean blood levels of Ti ions were 1.87 microg/L in hip resurfacing and and 1.30 microg/L in total hip replacement (p = 0.001). The study confirms even with different bearing diameters and clearances, hip replacement and 28 mm metal-on-metal total hip replacement produced similar Cr and Co metal ion levels in this randomised controlled trial study design, but apart from wear on bearing surfaces, passive corrosion of exposed metallic surfaces is a factor which influences ion concentrations. Ti plasma spray coating the acetabular components for hip resurfacing produces significantly higher release of Ti than Ti grit-blasted surfaces in total hip replacement.

A randomised controlled trial of total hip arthroplasty versus resurfacing arthroplasty in the treatment of young patients with arthritis of the hip joint

Background

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.

Methods/design

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

Sports after knee arthroplasty: partial versus total knee arthroplasty

Osteoarthritis becomes more prevalent with increasing age, and currently is occurring more frequently in the "baby boomer" generation (ages 44-66 years). However, many individuals may be reluctant to undergo arthroplasty procedures because potential activity limitations. Thus, physicians must consider each patient's history and desired activity level after treatment. Osteoarthritis treatments include nonoperative measures such as weight reduction, injections, and nonsteroidal anti-inflammatory drugs, as well as operative options, including partial and total knee arthroplasty. Each treatment type will vary in its impact on activity levels. If arthroplasty is required, patients must be cautioned to minimize component overload, which may result in polyethylene wear and loosening; however, cardiopulmonary fitness and general conditioning benefits of activity can be maintained.

Risk factors for inflammatory pseudotumour formation following hip resurfacing

Metal-on-metal hip resurfacing is commonly performed for osteoarthritis in young active patients. We have observed cystic or solid masses, which we have called inflammatory pseudotumours, arising around these devices. They may cause soft-tissue destruction with severe symptoms and a poor outcome after revision surgery. The aim of this study was to determine the incidence of and risk factors for pseudotumours that are serious enough to require revision surgery.

Since 1999, 1419 metal-on-metal hip resurfacings have been implanted by our group in 1224 patients; 1.8% of the patients had a revision for pseudotumour. In this series the Kaplan-Meier cumulative revision rate for pseudotumour increased progressively with time. At eight years, in all patients, it was 4% (95% confidence interval (CI) 2.2 to 5.8). Factors significantly associated with an increase in revision rate were female gender (p < 0.001), age under 40 (p = 0.003), small components (p = 0.003), and dysplasia (p = 0.019), whereas implant type was not (p = 0.156). These factors were inter-related, however, and on fitting a Cox proportional hazard model only gender (p = 0.002) and age (p = 0.024) had a significant independent influence on revision rate; size nearly reached significance (p = 0.08). Subdividing the cohort according to significant factors, we found that the revision rate for pseudotumours in men was 0.5% (95% CI 0 to 1.1) at eight years wheras in women over 40 years old it was 6% (95% CI 2.3 to 10.1) at eight years and in women under 40 years it was 13.1% at six years (95% CI 0 to 27) (p < 0.001).

We recommend that resurfacings are undertaken with caution in women, particularly those under 40 years of age but they remain a good option in young men. Further work is required to understand the aetiology of pseudotumours so that this complication can be avoided.

Digital templating and preoperative deformity analysis with standard imaging software

Analysis of deformity and subsequent correction are the basis for many orthopaedic surgical procedures. In advanced cases of joint degeneration, arthroplasty may be the only available treatment option. Until recently, these analyses and preoperative surgical plans have been performed using standard radiographs, tracing paper, and/or plastic overlays. Numerous customized, commercially available, computer-based preoperative planning software programs have been introduced. The purposes of this study were to describe (1) the techniques used in deformity analysis and preoperative surgical planning using standard radiographs for joint arthroplasty and corrective osteotomies of the extremities, (2) the use of computed tomography (CT) scans to analyze rotational deformities in the presence and absence of joint prostheses and in planning corrective rotational osteotomies or revision joint replacement, and (3) the techniques for analyzing angular deformities of the spine. All these applications were performed with a widely available image analysis software.

Comparison of acetabular reamings during hip resurfacing versus uncemented total hip arthroplasty

PURPOSE

To compare the quantity of bone removed from the acetabulum during resurfacing hip arthroplasty versus uncemented total hip arthroplasty (THA).

METHODS

62 consecutive patients with osteoarthritis of the hip were prospectively studied. 24 men and 7 women aged 40 to 86 (mean, 59) years underwent Birmingham hip resurfacing. 13 men and 18 women aged 34 to 88 (mean, 61) years underwent uncemented THA using the trident acetabular cup. Obese elderly women at risk of femoral neck fracture and patients with large subchondral pseudocysts or a history of avascular necrosis of the femoral head were assigned to uncemented THA. Acetabular reamings were collected; marginal osteophytes were not included. The reamings were dehydrated, defatted, and weighed.

RESULTS

The mean weight of acetabular reamings was not significantly different between patients undergoing hip resurfacing and uncemented THA (p=0.57).

CONCLUSION

In hip resurfacing, the use of an appropriately small femoral component avoids oversizing the acetabular component and removal of excessive bone stock.

Does hip resurfacing require larger acetabular cups than conventional THA?

Hip resurfacing is femoral bone preserving, but there is controversy regarding the amount of bone removed at the acetabular side. We therefore compared the implanted acetabular cup sizes in primary THAs between two resurfacing devices and a conventional press-fit cup using a series of 2134 THAs (Allofit cup 1643 hips, Durom Hip Resurfacing 249 hips, and Birmingham Hip Resurfacing 242 hips). The effects of patient demographics and cup position in the horizontal plane also were assessed. After controlling for gender, patients were matched for height, weight, body mass index, and age. The mean size for Allofit cups was smaller than the sizes for Durom and Birmingham Hip Resurfacing cups in women (49.9 mm, 51.6 mm, 52.3 mm, respectively) and men (55.1 mm, 56.7 mm, 57.8 mm; respectively). Although patient height was associated with the implanted cup size, the cup position in the horizontal plane had no effect on the size used. Larger cups were used with hip resurfacing than for THA with a conventional press-fit cup. However, additional studies are needed to determine whether these small differences have any clinical implications in the long term. The association of cup size and patient height should be considered in future studies comparing component sizes among different implants.

LEVEL OF EVIDENCE

Level III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Heterotopic ossification after surface replacement arthroplasty and total hip arthroplasty: a randomized study

With a randomized clinical trial, we compared the incidence and severity of heterotopic ossification in cohorts of patients who have undergone either surface replacement arthroplasty or total hip arthroplasty at a minimum follow-up of 1 year. Surface replacement arthroplasty group had a significantly higher rate of severe heterotopic ossification (Brooker grades 3-4) than the total hip arthroplasty group, 12.6% (13/103) vs 2.1% (2/97) respectively (P = .02). Grade 4 heterotopic ossification was observed (4.9%, 5/103) exclusively in the surface replacement arthroplasty group. Patients with severe heterotopic ossification had significantly inferior functional outcome scores. Surgeons offering surface replacement must be aware of this risk and use meticulous surgical technique and consider routine prophylaxis against heterotopic ossification.

Metal-on-metal hip resurfacing: the effect of cup position and component size on range of motion to impingement

The aim of this dry bone study was to determine the range of hip motion to impingement for different hip resurfacing cup positions and component sizes. The maximum angles of hip flexion, extension, abduction, and adduction were calculated from 3-dimensional coordinates for: 1. Cup inclination of 30 degrees , 40 degrees , 50 degrees , 60 degrees , and 70 degrees with fixed anteversion; 2. Cup anteversion of 0 degrees , 10 degrees , 25 degrees , 35 degrees , and 45 degrees with fixed inclination; and 3. 3 different component sizes on the same size dry bones. An acetabular component inclination of 50 degrees and an anteversion of 25 degrees allowed the most physiologic range of hip motion. A larger-diameter femoral component relative to the native femoral neck diameter resulted in a greater range of hip motion to impingement.

Metal-on-metal hip resurfacing: advantages and disadvantages

Modern metal-on-metal resurfacing has recently gained popularity as an alternative to standard stemmed total hip arthroplasty. This study analyzed, from a literature review, the purported advantages and disadvantages of resurfacing with a comparison to standard hip arthroplasty. Advantages may include bone conservation on the femoral side with possible lower dislocation rates, more range-of-motion, more normal gait pattern, increased activity levels, increased ease of insertion with proximal femoral deformities or retained hardware, and straightforward revision. Possible disadvantages of resurfacing are increased difficulty to perform the procedure, increased acetabular bone stock loss, femoral neck fractures, and concerns about the effects of metal ions. Many of these issues will need further clarification by well-planned prospective studies and evaluation of longer-term outcomes.

[Hip resurfacing: current state of knowledge]

SUMMARY

The tribologic quality of metal-on-metal bearings has enabled a second generation of hip resurfacing techniques. Compared with a conventional hip prosthesis, this type of arthroplasty has many advantages: sparing femoral (and acetabular) bone stock, preservation of hip joint biomechanics (femoral offset, leg length), better recovery for high-level sports activities, easier revision, less risk of dislocation, less risk of extension to the shaft in the event of osteolysis. Hip resurfacing can thus be considered as true "minimally invasive bone surgery". There are however specific complications of resurfacing, including femoral neck fracture and collapse of the femoral head. All of the conventional approaches can be used for hip resurfacing procedures, but a precise operative technique is mandatory. The key to success is a proper position of the femoral piece. Certain biomechanical rules for implantation are required in order to limit the cam effect, spare femoral bone, and maintain harmonious loading. Hip resurfacing can be indicated for young and/or active subjects for whom restoration of hip biomechanics offers a real advantage over conventional hip arthroplasty. The mid-term results have been encouraging, both clinically and radiographically.

Metal-on-metal hip resurfacing: a skeptic's view

Contemporary metal-on-metal hip resurfacing is the third attempt by its proponents to eliminate a diaphyseal femoral component. I have multiple objections with the resurfacing concept and believe even the premises for the use of resurfacing invalid. There is a high rate of success with circumferential bead or mesh-coated uncemented stemmed femoral components at 10 to 20 years and there have been no long-term adverse consequences of femoral stress shielding with a diaphyseal component. More acetabular bone may be removed with resurfacing, negating its "conservative" premise. One computer simulation suggested the range of hip motion might be considerably less with resurfacing compared with conventional hip arthroplasty. There are a very limited number of patients for whom hip resurfacing is truly indicated, and the femoral head may be unsuitable for resurfacing in 40% of selected patients. Resurfacing is technically more difficult than conventional hip arthroplasty. Early complications and revision for femoral neck fractures are more likely with resurfacing. Blood and urine metal ion levels, capsular lymphocytic aggregation, and hypersensitivity are concerns with metal-on-metal articulation. Metal-on-metal hip resurfacing should only be used by a limited number of hip surgeons. The risks and complications of metal-on-metal hip resurfacing outweigh any possible advantages.

Factors affecting hip range of motion in surface replacement arthroplasty

BACKGROUND

Surface replacement arthroplasty aims to re-create normal hip biomechanics; however the pathoanathomy of the hip, prosthetic component design, surgical technique and other factors may have a significant impact on the range of motion restoration attained following surface replacement arthroplasty. However, there is paucity of information on the effect of such factors.

METHODS

A computerized three-dimensional hip model was created from preoperative computerized tomography images of a patient who was scheduled for a surface replacement arthroplasty. The effects of the femoral component size, translation and orientation on the range of motion were analysed as was the effect of increasing the seating depth and modification of the version of the acetabular component.

FINDINGS

Increasing the femoral component size led to global improvement in range of motion while translation increased range of motion in one direction but reduced it in the opposite direction. Change in the femoral component orientation had minimal effects on range of motion in comparison to the effect of changes in the version of the acetabular component. Increasing the seating depth of the acetabulum only caused reduced range of motion in internal rotation in 90 degrees flexion.

INTERPRETATION

To restore hip range of motion, surgeons performing surface replacement arthroplasty should aim to reproduce the natural femoral head-neck offset. Although increasing the femoral component size may achieve this, more acetabular bone will be resected. Knowing the specific zones of impingement of each arc of movement, selective translation of the femoral component or femoral neck osteoplasty can restore femoral neck offset in more critical areas without affecting acetabular bone stock. Over deepening of the acetabulum or leaving rim osteophytes should also be avoided to prevent impingement.

Chromium and cobalt ion release following the Durom high carbon content, forged metal-on-metal surface replacement of the hip

We evaluated the concentrations of chromium and cobalt ions in blood after metal-on-metal surface replacement arthroplasty using a wrought-forged, high carbon content chromium-cobalt alloy implant in 64 patients. At one year, mean whole blood ion levels were 1.61 μg/L (0.4 to 5.5) for chromium and 0.67 μg/L (0.23 to 2.09) for cobalt. The pre-operative ion levels, component size, female gender and the inclination of the acetabular component were inversely proportional to the values of chromium and/or cobalt ions at one year postoperatively. Other factors, such as age and level of activity, did not correlate with the levels of metal ions. We found that the levels of the ions in the serum were 1.39 and 1.37 times higher for chromium and cobalt respectively than those in the whole blood.

The levels of metal ions obtained may be specific to the hip resurfacing implant and reflect its manufacturing process.

A prospective randomized clinical trial comparing metal-on-metal total hip arthroplasty and metal-on-metal total hip resurfacing in patients less than 65 years old

The purpose of this prospective randomised study is to compare the early clinical results of the metal-on-metal hip resurfacing to metal-on-metal THA. Two hundred and ten hips were randomised between August 2003 and January 2006 (191 subjects). One hundred and two hips were implanted with an uncemented titanium tapered stem, and an uncemented titanium acetabular component and 28 mm metal-on-metal bearing (THA group) and 103 hips received a hybrid metal-on-metal surface replacement arthroplasty (SRA group). No significant difference was found with the WOMAC or Merle dAubign-Postel scales. However, a significantly higher activity level was found in the SRA group (UCLA score 6.3 versus 7.1, p= 0.037) and a greater percentage of the SRA patients returned to heavy or moderate activities at one - year postoperatively (72% versus 39%, p=0.007). No patient in either group presented with thigh pain one year after surgery. Both techniques present similar complication rates (0.15). This study supports the theory of better functional recovery in the short-term favouring the SRA when compared to THA. The clear benefit of surface replacement arthroplasty over THA is proximal femoral bone preservation. However, the long term survivorship of the SRA will determine the real value of the theoretical advantage.