Hip Resurfacing Arthroplasty Research Articles

Hip Resurfacing Versus Large-Diameter Head Total Hip Arthroplasty. A Prospective Comparative Cohort Study on Early Functional Outcomes

Objective: There is no consensus whether hip resurfacing arthroplasty (HRA) performs better than a stem-type total hip arthroplasty (THA). Therefore, the aim of this prospective comparative matched-cohort study was to answer the following questions: 1) Do gait parameters differ between HRA and THA patients at 3, 6, and 12 months after surgery? 2) Are there differences in lower extremity muscle strength at the same time points? 3) Does the selfreported outcome using validated instruments improve similarly in both groups? Methods: One experienced senior surgeon implanted either Durom HRA or CLS Spotorno THA in 34 male patients matched for anthropometric characteristics, preoperative scores and comorbidities. Preoperatively and at 3, 6, and 12 months, gait parameters, hip and knee muscle strength, clinical data and standardized outcome scores were assessed and compared between the two groups. Results: No significant group differences were found for all gait and strength variables. Passive range of motion and mean scores for the SF-36, Harris Hip Score and UCLA activity scale improved significantly over time without differences between groups. At 12 months, more HRA than THA patients were reporting groin pain on impingement testing (20% versus 0%; P<0.05). Conclusions: Excellent early outcomes were achieved by both HRA and THA in terms of score values, lower extremity muscle strength and gait parameters. No clinically relevant differences could be observed between HRA and THA patients. Groin pain after HRA remains a concern that warrants future investigation.

Hip resurfacing arthroplasty at a non-specialist centre

INTRODUCTIONFew studies have reported the outcome of hip resurfacing arthroplasty (HRA) with respect to implant characteristics from non-specialist centres. We report the survival, clinical and radiological outcomes of a single surgeon series of HRA with an average follow-up duration of five years.METHODSAll consecutive HRAs performed by a single surgeon between 2003 and 2011 at a district general hospital were retrospectively examined clinically and radiologically.RESULTSA total of 85 patients underwent 109 HRAs (58 male [53.2%] and 51 female patients [46.8%]) with a mean follow-up period of 62 months (range: 12–102 months). The median age was 57 years (range: 25–75 years). The mean acetabular and femoral head component sizes were 54mm (range: 48–64mm) and 48mm (range: 42–58mm) respectively with a mean acetabular inclination angle of 42.9º (range: 20–75º).The survival rate was 95% with five revisions due to aseptic loosening (n=3) and fracture (n=2): these were predominantly for female patients (n=4), with significantly smaller mean acetabular (51mm, p=0.04) and femoral (44mm, p=0.02) implant sizes. Furthermore, they had a higher mean acetabular inclination angle of 48.1º (p=0.74). The mean Oxford hip score was 43.8 (range: 25–48) and the mean University of California Los Angeles (UCLA) activity score was 6.8 (range: 3–10). Radiological findings included heterotopic ossification in 13 (11.9%), radiolucent lines in 6 (5.5%), femoral neck thinning in 2 (1.8%) and femoral neck notching in 5 patients (4.6%).CONCLUSIONSWe have shown that HRA at a non-specialist centre has short to medium-term outcomes comparable with those at specialist centres. HRA therefore remains a viable option although vigilance is required in case selection and follow-up according to national guidance.

Hip resurfacing arthroplasty and perioperative blood testing.

It is standard practice in many institutions to routinely perform preoperative and postoperative haemoglobin level testing in association with hip joint arthroplasty procedures. It is our observation, however, that blood transfusion after uncomplicated primary hip arthroplasty in healthy patients is uncommon and that the decision to proceed with blood transfusion is typically made on clinical grounds. We therefore question the necessity and clinical value of routine perioperative blood testing about the time of hip resurfacing arthroplasty. We present analysis of perioperative blood tests and transfusion rates in 107 patients undertaking unilateral hybrid hip resurfacing arthroplasty by the senior author at a single institution over a three-year period. We conclude that routine perioperative testing of haemoglobin levels for hip resurfacing arthroplasty procedures does not assist in clinical management. We recommend that postoperative blood testing only be considered should the patient demonstrate clinical signs of symptomatic anaemia or if particular clinical circumstances necessitate.

Asymmetrical hip loading correlates with metal ion levels in patients with metal-on-metal hip resurfacing during sit-to-stand

The occurrence of pseudotumours following metal-on-metal hip resurfacing arthroplasty (MoMHRA) has been associated with high serum metal ion levels and consequently higher than normal bearing wear. Measuring ground reaction force is a simple method of collecting information on joint loading during a sit-to-stand (STS). We investigated vertical ground reaction force (VGRF) asymmetry during sit-to-stand for 12 MoMHRA patients with known serum metal ion levels. Asymmetry was assessed using two methods: a ratio of VGRF for implanted/unimplanted side and an absolute symmetry index (ASI). It was found that subjects with high serum metal ion levels preferentially loaded their implanted sides. The difference between the two groups was most apparent during the first 22% of STS. VGRF ratio showed significant and strong correlation with serum metal ion levels (Spearman's rho = 0.8, p = 0.003). These results suggest that individual activity patterns play a role in the wear of MoMHRA and preferential loading of an implanted limb during the initiation of motion may increase the wear of metal-on-metal hip replacements.

Outcome of hip resurfacing arthroplasty in patients with coxarthrosis secondary to Crowe′s types I and II developmental hip dysplasia

BackgroundArthritis secondary to developmental hip dysplasia is a surgical challenge because of the anatomic abnormalities, which increase the complexity of any hip arthroplasty. Hip resurfacing has many theoretical advantages compared with conventional hip arthroplasty, especially for young and active patients. These advantages include minimal bone resection, normal femoral loading, avoidance of stress shielding, maximum proprioceptive feedback, reduced risk of dislocation, easy revision, and reconstruction of normal anatomy.Patients and methodsTwenty-six consecutive patients (33 hips) with osteoarthritis secondary to developmental dysplasia of the hip of Crowe types I and II underwent metal-on-metal hip resurfacing through a modified lateral approach of Hardinge, taking care to protect the medial femoral circumflex artery and its retinacular branches over the femoral neck. The average age of the patients at the time of surgery was 62.8 years (range 30-73 years). Five (19%) patients were men and 21 (81%) were women. The mean follow-up was 4.8 years, range 1.8-10.3 years.ResultsFour patients developed heterotrophic ossification, which required excision because of persistent pain in one patient. Three patients had painful trochanteric bursitis; all responded well to local steroid injections. The Harris hip score improved from a mean of 52.2-97.4. There were no major complications, for example, dislocation, fractured neck of femur, loosening, infection, or symptomatic deep venous thrombosis.ConclusionDespite safety warnings, hip resurfacing remains an effective option in certain subgroups of hip dysplasia when it is performed with special precautions.

Hip resurfacing arthroplasty versus large-diameter head metal-on-metal total hip arthroplasty: comparison of three Designs from the Finnish Arthroplasty Register

Large headed metal-on-metal total hip arthroplasty may produce more metal ions than hip resurfacing arthroplasty. Increased metal-ion levels may be associated with higher revision rates due to adverse reaction to metal debris. The purpose of our study was to compare the survivorship of three hip resurfacing arthroplasty designs with their analogous cementless large-diameter head metal-on-metal total hip arthroplasties. Based on data obtained from the Finnish Arthroplasty Register, the revision risks of three metal-on-metal hip resurfacing arthroplasty/total hip arthroplasty design couples performed during 2001-2011 were analyzed using the Cox regression model. In the Cox regression analysis for compared design pairs adjusted for age, gender, operated side, head size, diagnosis, and implant, there was no statistically significant difference in revision risk between ReCap hip resurfacing arthroplasty and Bimetric/ReCap total hip arthroplasty (risk ratio = 1.43, confidence interval = 0.95-2.14, p = 0.09) or between Birmingham hip resurfacing arthroplasty and Synergy/Birmingham hip resurfacing total hip arthroplasty (risk ratio = 1.35, confidence interval = 0.75-2.43, p = 0.31). However, the revision risk of Corail and Summit/articular surface replacement total hip arthroplasty (ASR HRA) was significantly increased compared to ASR HRA. (risk ratio = 0.73, confidence interval = 0.54-0.98, p = 0.04). We conclude that the short-term revision risk of large headed metal-on-metal total hip arthroplasties was not increased compared to analogous hip resurfacing arthroplasties in two out of three devices studied at a nationwide level. There may be implant-related factors having an effect on the success of single manufacturer devices. However, more information on the incidence of adverse soft-tissue reactions in these patient cohorts is needed.

Hip resurfacing versus traditional total hip arthroplasty for osteoarthritis and other non-traumatic diseases of the hip

Hip resurfacing versus traditional total hip arthroplasty for osteoarthritis and other non-traumatic diseases of the hip

Editorial

Women do not benefit from medical research as much as men do [2, 5]. This problem stems both from research design (which scientists largely control), and from scientific reporting in journals (which editors can influence). Starting with the latter, we first must learn to talk about sex. Sex (female or male) refers to the genotype, while gender (woman or girl, man or boy) refers to the social constructs that overlie the genotype. Gender tends to be culturally laden, and as such, separating sex from gender in certain kinds of research is nearly impossible. Do women as a cultural norm have less pain after knee replacement, or is it a condition innate to the biology of the female sex? If the former, might this be driven by women reporting pain differently on standardized scoring instruments (or to their surgeons, who are more likely to be men)? Or are there important physiological differences in pain signaling between males and females? Other explanations are possible — for example, it is likely that women’s responses are interpreted differently by surgeons of either gender — and it is not always possible to know whether sex, gender, or both account for the observed effect. But when possible, we will seek clarity in authors’ explanations: Are the differences gender-driven, sex-driven, or is it not possible to tell? This is not just a semantic issue. It is a health issue, both for women and men. Women have been underrepresented in medical research, and therefore the evidence that drives their care is less robust [2, 5]. Pharmacokinetics and responses to important therapeutic interventions differ between men and women [3], and women are more likely to experience adverse drug reactions [6]. Surgeons may believe this is a “medical thing” and not a problem in orthopaedic surgery. That is wrong. Women consume approximately 85% of the Cox-II-specific NSAIDs that are prescribed and the side effect profiles of these drugs — including important, life-threatening side effects — differ between men and women [6]. Yet, the treatment of women with NSAIDs is based on Cox-II trials consisting disproportionately of men [1]. We learned only belatedly that women are at much greater risk of complications and failure after total hip resurfacing arthroplasty [4], and the result suggests that clearer scientific reporting would have prevented harm to many women. We probably do not know the full extent of the harm we may be causing because the reporting of results by gender is so inconsistently performed in medical and surgical trials in our specialty. This must change. Accordingly, we recommend that investigators writing for CORR®: Design studies that are sufficiently powered to answer research questions both for males and females (or men and women) if the health condition being studied occurs in both sexes/genders. Provide sex- and/or gender-specific data where relevant in all clinical, basic science, and epidemiological studies. Analyze the influence (or association) of sex or gender on the results of the study, or indicate in the Patients and Methods section why such analyses were not performed, and consider this topic as a limitation to cover in the Discussion section. Readers need to know whether the results generalize to both sexes/genders. Indicate (if sex or gender analyses were performed post-hoc) that these analyses should be interpreted cautiously because they may be underpowered (leading to a false conclusion of no difference). If there are many such analyses, indicate that they may lead to spurious significance, and an erroneous conclusion of a sex- or gender-related difference. We present these as recommendations, rather than requirements for publication because the topic is relatively new to the collective consciousness of our specialty. Our editorial board will continue to evaluate whether and when guidelines like these should become requirements. For now, we will consider the scientific reporting of sex- and gender-related findings an important element of the papers we consider for publication. Our research needs to reflect that we treat both men and women, and that both are equally entitled to the benefits of care based on good, applicable evidence.

Impact of implant size on cement filling in hip resurfacing arthroplasty

Larger proportions of cement within femoral resurfacing implants might result in thermal bone necrosis. We postulate that smaller components are filled with proportionally more cement, causing an elevated failure rate. A total of 19 femoral heads were fitted with polymeric replicas of ReCap (Biomet) resurfacing components fixed with low-viscosity cement. Two specimens were used for each even size between 40 and 56 mm and one for size 58 mm. All specimens were imaged with computed tomography, and the cement thickness and bone density were analyzed. The average cement mantle thickness was 2.63 mm and was not correlated with the implant size. However, specimen with low bone density had thicker cement mantles regardless of size. The average filling index was 36.65% and was correlated to both implant size and bone density. Smaller implants and specimens with lower bone density contained proportionally more cement than larger implants. According to a linear regression model, bone density but not implant size influenced cement thickness. However, both implant size and bone density had a significant impact on the filling index. Large proportions of cement within the resurfacing head have the potential to generate thermal bone necrosis and implant failure. When considering hip resurfacing in patients with a small femoral head and/or osteoporotic bone, extra care should be taken to avoid thermal bone necrosis, and alternative cementing techniques or even cementless implants should be considered. This study should help delimiting the indications for hip resurfacing and to choose an optimal cementing technique taking implant size into account.

Jogging After Total Hip Arthroplasty

Background: Jogging has been classified as a high-impact sport, and jogging after total hip arthroplasty (THA) has not been well documented. Purpose: To investigate the participation rate for postoperative jogging as well as jogging parameters and the influence of jogging on implant stability and bearing wear. Study Design: Case-control study; Level of evidence, 3. Methods: Included in this study were 804 hips in 608 patients (85 men, 523 women) who underwent THA between 2005 and 2011 with follow-up longer than 1 year. The mean patient age was 62 years (range, 26-98 years), and mean follow-up duration was 4.8 years (range, 2.3-7.8 years). Hip resurfacing arthroplasty (HRA) was performed in 81 patients and conventional THA in 527 patients. During routine postsurgical visits, patients were given a questionnaire concerning preoperative and postoperative jogging routines. For joggers, frequency, distance, duration, and velocity of jogging were recorded. Patients who did not jog postoperatively were asked to provide reasons for not jogging. Radiographs concerning implant migration and polyethylene wear were evaluated with specialized software, and serum cobalt and chromium ion concentrations were investigated for patients with metal-on-metal articulation. Results: A total of 33 patients (5.4%) performed jogging preoperatively, and 23 patients (3.8%) performed jogging postoperatively. Of the 23 who jogged postoperatively, conventional THA was performed in 13 patients and HRA in 10 patients. Postoperatively, joggers trained a mean of 4 times (range, 1-7 times) per week, covering a mean distance of 3.6 km (range, 0.5-15 km) in a mean time of 29 minutes (range, 5-90 minutes) per session and at a mean speed of 7.7 km/h (range, 3-18 km/h). No patient complained of pain or showed serum cobalt and chromium ion elevation greater than 7 ppb. No hip showed loosening, abnormal component migration, or excessive wear at a mean 5-year follow-up. There were 74 postoperative non-joggers with an interest in jogging. The reasons given for avoiding jogging included anxiety (45 patients; 61%); impossible because of several reasons, including pain, decreased range of motion, and muscle weakness (18 patients; 24%); and lumbar or knee pain (11 patients; 15%). Multivariate analysis revealed that male sex and a history of preoperative jogging demonstrated significant relationships with postoperative jogging. Conclusion: A total of 3.8% of THA patients participated in postoperative jogging. Short-term postoperative follow-up did not identify any negative influence of jogging on implant survival.

Increased post-operative ischemia in the femoral head found by microdialysis by the posterior surgical approach: a randomized clinical trial comparing surgical approaches in hip resurfacing arthroplasty

Hip resurfacing arthroplasty (HRA) is associated with osteonecrosis of the femoral head and femoral neck fracture, which may be caused by a decrease in the perfusion of the bone initiated at surgery. Several studies have demonstrated a decreased blood flow during surgery depending on the choice of surgical approach. We investigated the effect of the surgical approach on the blood flow and metabolism in the femoral head and neck in HRA by Laser Doppler flowmetry (LDF) and microdialysis. We conducted a randomized clinical trial on 38 patients, allocated to HRA by either the posterior (Post) or the antero-lateral (AntLat) surgical approach. LDF was performed during surgery and microdialysis after surgery to assess the concentration of the following metabolic markers: glucose, lactate, pyruvate and glycerol. At 44-50 h after surgery, the mean lactate/pyruvate (L/P) and lactate/glucose (L/G) ratio was higher in the Post group compared to the AntLat group; L/P 195.3 (SEM 123) in Post and 128.5 (108.0) in AntLat; L/G 16.9 (6.5) in Post and 8.9 (3.7) in AntLat (p L/P = 0.02 and p L/G = 0.03). There was no difference in the LDF measurements (p = 0.74). HRA in the posterior approach results in increased post-operative ischemia in the femoral head and neck although during surgery, no difference in the blood flow was found. Still, the antero-lateral approach also causes considerable ischemia and other possible explanations, such as damage to the retinacular vessels during surgery or altered microcirculation because of heating from the cementation process, needs to be investigated.

Marker-based or model-based RSA for evaluation of hip resurfacing arthroplasty? A clinical validation and 5-year follow-up

The stability of implants is vital to ensure a long-term survival. RSA determines micro-motions of implants as a predictor of early implant failure. RSA can be performed as a marker- or model-based analysis. So far, CAD and RE model-based RSA have not been validated for use in hip resurfacing arthroplasty (HRA). A phantom study determined the precision of marker-based and CAD and RE model-based RSA on a HRA implant. In a clinical study, 19 patients were followed with stereoradiographs until 5 years after surgery. Analysis of double-examination migration results determined the clinical precision of marker-based and CAD model-based RSA, and at the 5-year follow-up, results of the total translation (TT) and the total rotation (TR) for marker- and CAD model-based RSA were compared. The phantom study showed that comparison of the precision (SDdiff) in marker-based RSA analysis was more precise than model-based RSA analysis in TT (p CAD < 0.001; p RE = 0.04) and TR (p CAD = 0.01; p RE < 0.001). The clinical precision (double examination in 8 patients) comparing the precision SDdiff was better evaluating the TT using the marker-based RSA analysis (p = 0.002), but showed no difference between the marker- and CAD model-based RSA analysis regarding the TR (p = 0.91). Comparing the mean signed values regarding the TT and the TR at the 5-year follow-up in 13 patients, the TT was lower (p = 0.03) and the TR higher (p = 0.04) in the marker-based RSA compared to CAD model-based RSA. The precision of marker-based RSA was significantly better than model-based RSA. However, problems with occluded markers lead to exclusion of many patients which was not a problem with model-based RSA. HRA were stable at the 5-year follow-up. The detection limit was 0.2 mm TT and 1° TR for marker-based and 0.5 mm TT and 1° TR for CAD model-based RSA for HRA.

Revision of Hip Resurfacing Arthroplasty with a Bone-conserving Short-stem Implant

The good clinical results in hip arthroplasty have led to an increasing number of joint replacements in younger patients. Regardless, it is well known that this patient group faces an increased risk of early implant failure, [1] which is probably related to their higher activity level. Revision surgeries often go along with loss of bone substance, [2] resulting in more difficult procedures and an impaired functional outcome. [3] To facilitate potential revision surgeries, bone-preserving implants, such as hip resurfacing arthroplasty (HRA) and short-stem arthroplasty (SHA) implants, have been developed and recently have gained increasing popularity.However, data are lacking on how much bone stock is conserved – and whether revision procedures are actually facilitated by the use of bone-preserving implants. So far, only a few studies have reported on the revision of failed HRA implants, and all revisions have exclusively been performed by the use of a conventional stem. [4,5]In this report, we describe a woman with early failure of HRA. Revision was performed with a bone-conserving short-stem hip implant, which minimizes the bone loss on the femoral side in order to facilitate potential revision surgery.

The thermal effects of lavage on 57 ox femoral heads prepared for hip resurfacing arthroplasty

Background and purpose Previously, we have documented surface temperatures recorded by thermography great enough to cause osteonecrosis of the femoral head during hip resurfacing. We now performed an in vitro investigation with 3 questions: (1) whether water irrigation reduced bone surface temperature, (2) whether external bone temperatures were similar to core temperatures, and (3) whether blunting of the reamer affected temperature generation.Methods Using an ox-bone model, 57 femoral heads were peripherally reamed. The surface temperatures of bone were measured using a thermal camera and internal bone temperatures were measured using 2 theromocouples. We measured the effects of cooling with water at room temperature and with ice-cooled water. Progressive blunting of reamers was assessed over the 57 experiments.Results Mean and maximum temperatures generated during peripheral reaming were greater when no irrigation was used. Ice-cold saline protected femoral heads from thermal damage. External bone temperatures were much greater than internal temperatures, which were not sufficiently elevated to cause osteonecrosis regardless of lavage. Blunting of the reamer was not found to have a statistically significant effect in this study.Interpretation Cooling with ice-cooled water is recommended. Internal bone temperatures are not elevated despite the high surface temperatures reached during femoral head resurfacing.

Reducing the risk of early femoral failure after metal-on-metal hip resurfacing arthroplasty

This study included 96 consecutive cases with a dual-energy X-ray absorptiometry scan T score lower than −1.5 who were operated on between September 2006 and December 2009. The control group, without treatment of alendronate, included consecutive 42 cases. The study group, treated with alendronate (for 1 year) as well as a “slowed down” weight-bearing protocol, included the consecutive 54 cases. Otherwise, treatment was the same for both groups. There were four early femoral failures in the control group: two due to femoral neck factures and two due to early femoral head collapse. There were no early femoral failures in the study group. This study demonstrates that treating high-risk patients who have a low bone density with a 1-year regimen of alendronate and a slowed down weight-bearing protocol can significantly reduce the risk of early femoral failure in hip resurfacing.

Cost-Utility of Metal-on-Metal Hip Resurfacing Compared to Conventional Total Hip Replacement in Young Active Patients with Osteoarthritis

BackgroundMetal-on-metal hip resurfacing arthroplasty (MoM HRA) has emerged as an alternative to total hip arthroplasty (THA) for younger active patients with osteoarthritis (OA). Birmingham hip resurfacing is the most common MoM HRA in Alberta, and is therefore compared with conventional THA. ObjectiveThe objective of this study was to estimate the expected cost-utility of MoM HRA versus THA, in younger patients with OA, using a decision analytic model with a 15-year time horizon. MethodsA probabilistic Markov decision analytic model was constructed to estimate the expected cost per quality-adjusted life-year (QALY) of MoM HRA versus THA from a health care payer perspective. The base case considered patients with OA aged 50 years; men comprised 65.9% of the cohort. Sensitivity analyses evaluated cohort age, utility values, failure probabilities, and treatment costs. Data were derived from the Hip Improvement Project and the Hip and Knee Replacement Pilot databases in Alberta, the 2010 National Joint Replacement Registry of the Australian Orthopaedic Association, and the literature. ResultsIn the base case, THA was dominated by MoM HRA (incremental mean costs of −$583 and incremental mean QALYs of 0.079). In subgroup analyses, THA remained dominated when cohort age was 40 years instead of 50 years or when only men were assessed. THA dominated when the cohort age was 60 years or when only women were assessed. Results were sensitive to utilities, surgery costs, and MoM HRA revision and conversion probabilities. At a willingness-to-pay of Can $50,000/QALY, there was a 58% probability that MoM HRA is cost-effective. ConclusionsThe results show that, on average, MoM HRA was preferred to THA for younger and male patients, but THA is still a reasonable option if the patient or clinician prefers given the small absolute differences between the options and the confidence ellipses around the cost-effectiveness estimates.

Resurfacing hip arthroplasty in neuromuscular hip disorders – A retrospective case series

BackgroundManagement of the degenerate hip in patients with neuromuscular conditions should be aimed at improving quality of life and ease of nursing care. Arthroplasty poses a significant challenge with predisposition to dislocation and loosening due to anatomical abnormalities, soft tissue contractures and impaired muscle tone. MethodsWe present a series of 11 hips (9 patients) following total hip resurfacing arthroplasty for painful osteoarthritis in patients with differing neuromuscular conditions. Patients were assessed clinically and radiographically and also for satisfaction of their carers due to improved ability to provide nursing care.Mean patient age was 33.1 years (range 13–49 years) with mean follow up at publication 63.7 months (41–89 months). All patients were operated by a single surgeon (AHN) and received the required post operative care and physiotherapy. Soft tissue releases were performed when necessary. All hips were assessed clinically and radiographically at 6 weeks and 6 months and 1 year post-operatively. Six month follow-up also included a questionnaire with scoring of care-provider satisfaction. ResultsTen hips had good clinical results with improvement in pain and function and radiologically showed no signs of loosening. One hip required revision to proximal femoral excision due to dislocation and loose acetabular component with severe pain. None of the other hips dislocated.Analysis of care provider satisfaction assessing ability to provide personal care, positioning and transferring, comfort, interaction and communication scored excellent to good in 10 patients and satisfactory in one. ConclusionWe believe hip resurfacing arthroplasty to be a viable option in the treatment of the complex problem of osteoarthritis in the hips of patients with neuromuscular disease. The improved biomechanics confer greater stability when compared to conventional total hip arthroplasty. Although technically demanding, a successful result has been shown to improve patient pain, function and ease of nursing care. Level of evidenceLevel IV.

Metal ion concentrations in body fluids after implantation of hip replacements with metal-on-metal bearing--systematic review of clinical and epidemiological studies.

IntroductionThe use of metal-on-metal (MoM) total hip arthroplasty (THA) increased in the last decades. A release of metal products (i.e. particles, ions, metallo-organic compounds) in these implants may cause local and/or systemic adverse reactions. Metal ion concentrations in body fluids are surrogate measures of metal exposure.ObjectiveTo systematically summarize and critically appraise published studies concerning metal ion concentrations after MoM THA.MethodsSystematic review of clinical trials (RCTs) and epidemiological studies with assessment of metal ion levels (cobalt, chromium, titanium, nickel, molybdenum) in body fluids after implantation of metalliferous hip replacements. Systematic search in PubMed and Embase in January 2012 supplemented by hand search. Standardized abstraction of pre- and postoperative metal ion concentrations stratified by type of bearing (primary explanatory factor), patient characteristics as well as study quality characteristics (secondary explanatory factors).ResultsOverall, 104 studies (11 RCTs, 93 epidemiological studies) totaling 9.957 patients with measurement of metal ions in body fluids were identified and analyzed. Consistently, median metal ion concentrations were persistently elevated after implantation of MoM-bearings in all investigated mediums (whole blood, serum, plasma, erythrocytes, urine) irrespective of patient characteristics and study characteristics. In several studies very high serum cobalt concentrations above 50 µg/L were measured (detection limit typically 0.3 µg/L). Highest metal ion concentrations were observed after treatment with stemmed large-head MoM-implants and hip resurfacing arthroplasty.DiscussionDue to the risk of local and systemic accumulation of metallic products after treatment with MoM-bearing, risk and benefits should be carefully balanced preoperatively. The authors support a proposed „time out“ for stemmed large-head MoM-THA and recommend a restricted indication for hip resurfacing arthroplasty. Patients with implanted MoM-bearing should receive regular and standardized monitoring of metal ion concentrations. Further research is indicated especially with regard to potential systemic reactions due to accumulation of metal products.

Adjustment of Overestimated CT-Based Attenuation Correction on Bone SPECT/CT After Hip-Resurfacing Arthroplasty

SPECT/CT has made it possible to perform attenuation correction easily. However, CT-based attenuation correction (CTAC) is overestimated when metal is inside the body. The aim of this investigation was to create and test a new attenuation correction formula for CTAC that decreases the overestimation caused by an artificial femoral head and hip joint. We tested the usefulness of the new formula in a phantom study. The phantom contained "bones" made from gypsum. The components were placed in the phantom, the point source was placed both near metal and away from metal, and the counts were compared to verify the usefulness of the new attenuation correction formula. The new formula included use of thresholds to prevent the overestimation caused by proximity to metal. With the standard formula, the maximum overestimation was 18% for a 22-cm artificial hip joint placed in the acetabular roof. With the new formula, using 2 thresholds, the overestimation decreased to 4%. The new attenuation correction formula helps provide more correct data in SPECT/CT examinations of patients with metallic implants.

The Canadian Arthroplasty Society’s experience with hip resurfacing arthroplasty

The purpose of this study was twofold: first, to determine whether the five-year results of hip resurfacing arthroplasty (HRA) in Canada justified the continued use of HRA; and second, to identify whether greater refinement of patient selection was warranted. This was a retrospective cohort study that involved a review of 2773 HRAs performed between January 2001 and December 2008 at 11 Canadian centres. Cox's proportional hazards models were used to analyse the predictors of failure of HRA. Kaplan-Meier survival analysis was performed to predict the cumulative survival rate at five years. The factors analysed included age, gender, body mass index, pre-operative hip pathology, surgeon's experience, surgical approach, implant sizes and implant types. The most common modes of failure were also analysed. The 2773 HRAs were undertaken in 2450 patients: 2127 in men and 646 in women. The mean age at operation was 50.5 years (sd 8.72; 18 to 82) and mean follow-up was 3.4 years (sd 2.1; 2.0 to 10.1). At the last follow-up a total of 101 HRAs (3.6%) required revision. Using revision for all causes of failure as the endpoint, Kaplan-Meier survival analysis showed a cumulative survival of 96.4% (95% confidence interval (CI) 96.1 to 96.9) at five years. With regard to gender, the five-year overall survival was 97.4% in men (95% CI 97.1 to 97.7) and 93.6% in women (95% CI 92.6 to 94.6). Female gender, smaller femoral components, specific implant types and a diagnosis of childhood hip problems were associated with higher rates of failure. The most common cause of failure was fracture of the femoral neck, followed by loosening of the femoral component. The failure rates of HRA at five years justify the ongoing use of this technique in men. Female gender is an independent predictor of failure, and a higher failure rate at five years in women leads the authors to recommend this technique only in exceptional circumstances for women.