Resurfacing is Comparable to Total Hip Arthroplasty at Short-term Followup Causes of early failure in a multicenter clinical trial of hip resurfacing. A comparison of total hip resurfacing and total hip arthroplasty - patients and outcomes. Changes in bone mineral density and femoral neck narrowing in the proximal femur three to five years after hip resurfacing versus conventional total hip arthroplasty. A randomised controlled trial of the clinical effectiveness and cost-effectiveness of different knee prostheses: the Knee Arthroplasty Trial (KAT). Cobalt and chromium levels in blood and urine following hip resurfacing arthroplasty with the Conserve Plus implant. Ceramic-on-ceramic total hip arthroplasty: update. The dual-mobility POLARCUP: first results from a multicenter study. Survival of Hip Replacements: A Comparison of a Randomized Trial and a Registry Two-year migration results of the ReCap hip resurfacing system—a radiostereometric follow-up study of 23 hips The Charnley versus the Spectron hip prosthesis: radiographic evaluation of a randomized, prospective study of 2 different hip implants. The Effect of Femoral Head Size on Functional Outcome in Primary Total Hip Arthroplasty: A Single-Blinded Randomised Controlled Trial The Charnley versus the Spectron hip prosthesis: clinical evaluation of a randomized, prospective study of 2 different hip implants. Excellent results with cementless total hip arthroplasty and alumina-on-alumina pairing: minimum ten-year follow-up The squeaking hip: a phenomenon of ceramic-on-ceramic total hip arthroplasty. A Randomized controlled trial comparing patellar retention versus patellar resurfacing in primary total knee arthroplasty: 5–10 year follow-up The Knee Arthroplasty Trial (KAT) design features, baseline characteristics, and two-year functional outcomes after alternative approaches to knee replacement. Cementless dual-mobility cup in total hip arthroplasty revision Comparison of total hip replacement with and without cement in patients younger than 50 years of age: the results at 18 years. Highly Crosslinked Polyethylene Does Not Reduce Aseptic Loosening in Cemented THA 10-year Findings of a Randomized Study What Works Best, a Cemented or Cementless Primary Total Hip Arthroplasty?: Minimum 17-year Followup of a Randomized Controlled Trial Resurfacing hip prostheses revisited: failure analysis during a 16-year follow-up. Problems With Cementless Total Knee Arthroplasty at 11 Years Followup Prostaglandin E2 level in tissue surrounding aseptic failed total hips Large femoral heads decrease the incidence of dislocation after total hip arthroplasty: a randomized controlled trial. Birmingham Hip Resurfacing in Patients who are Seventy Years of Age or Older The John Charnley Award: The Functional Outcome of Hip Resurfacing and Large-head THA Is the Same: A Randomized, Double-blind Study THA With Delta Ceramic on Ceramic: Results of a Multicenter Investigational Device Exemption Trial A randomized trial of ceramic-on-ceramic bearing versus ceramic-on-crossfire-polyethylene bearing in total hip arthroplasty: five-year outcomes. Early experience with dual mobility acetabular systems featuring highly cross-linked polyethylene liners for primary hip arthroplasty in patients under fifty five years of age: an international multi-centre preliminary study Custom stems for femoral deformity in patients less than 40 years of age Patellar resurfacing compared with nonresurfacing in total knee arthroplasty. A concise follow-up of a randomized trial. 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
Abstract Metal-on-metal total hip resurfacing arthroplasty has had excellent reported results at early to midterm followup , and some studies suggest that outcomes are comparable to conventional THA . We compared the clinical and radiographic outcomes of two closely matched groups of 54 patients who underwent resurfacing and conventional THA , respectively . Each group consisted of 36 men and 18 women who had a mean age of 52 years and a mean body mass index of 29 kg/m2 . At a minimum followup of 24 months ( mean , 40 months ; range , 24–60 months ) , the mean Harris hip scores increased similarly in both groups ( from 52 to 90 points and from 50 to 91 points for the resurfacing and conventional groups , respectively ) . Radiographic outcomes , revision rates , complications , pain scores , and satisfaction ratings of the two groups were similar . The patients who underwent resurfacing had higher postoperative weighted activity scores than the patients who underwent conventional THA , although they had higher preoperative weighted activity scores as well . The early outcomes of resurfacing are comparable to those of conventional THA . Level of Evidence : Level III , therapeutic study . See the Guidelines for Authors for a complete description of levels of evidence The purpose of this study was to evaluate the clinical outcomes and possible causes of early failure in a multicenter trial of metal-on-metal hip resurfacing . Two hundred patients were prospect ively enrolled and followed for an average of 31.2 months ( range , 12 - 54 months ) . Of 200 patients , 14 ( 7.0 % ) required revision surgery at a mean time of 19.5 months ( range , 3 - 47 months ) . Patients with failures were significantly younger and heavier than the nonfailures , and all were male . Patients who were revised did not differ from those who were not revised in terms of radiographic outcomes , but they did report lower functional outcome scores at all preoperative and postoperative testing intervals . Most failures ( 10/14 ) were related to early acetabular loosening . The learning curve was likely a factor in these cup failures . This report highlights the importance of patient selection and surgical technique in hip resurfacing arthroplasty . It is anticipated that further surgical experience will lead to a reduction in this high early failure rate A comparison of pertinent preoperative and postoperative data relative to total hip resurfacing versus total hip arthroplasty ( THA ) would assist in evaluating current perceptions in outcome . We compared 50 consecutive metal-metal resurfacing replacements in 50 patients with 44 consecutive conventional total hip arthroplasties in 35 patients , who were implanted during the same time period , by the same surgeon , and followed prospect ively for 2 to 4 years . The patients undergoing hip resurfacing were 62 % male , 9 years younger , and 3.2 inches taller , with a lower mean body mass index and American Society of Anesthesiologists ( ASA ) grade than patients undergoing total hip arthroplasty .  Preoperatively , patients undergoing resurfacing had a lower Harris hip score ( 46 vs 52 points ) , more pain , higher UCLA ( University of California at Los Angeles ) activity scores ( 4.2 vs 3.6 ) , and better range of motion . Surgical time for resurfacing was 18 % longer , but there was less total blood loss and fewer transfusions . Postoperatively , there was no difference in Harris hip score ( 97 vs 96 ) . Patients undergoing resurfacing had higher function , Short Form-12 physical activity scores , and UCLA activity scores , but also a higher incidence of slight or mild pain . There were no differences in postoperative range of motion or dislocation ( one each ) . The preoperative characteristics and general health status of the average patient undergoing resurfacing are more favorable than that of the average patient undergoing conventional total hip arthroplasty . Caution should be applied in attributing differences in outcomes directly to the arthroplasty technology We studied whether bone mineral density ( BMD ) is preserved without significant femoral neck narrowing ( FNN ) after hip resurfacing ( RHA ) ( n=42 ) versus small diameter metal-on-metal total hip arthroplasty ( MoM THA ) ( n=40 ) . In this three to five year r and omized trial BMD was measured in the calcar with dual energy absorptiometry ( DXA ) preoperatively , at three and six months , one , two , three and five years postoperatively . Four additional BMD regions of interest ( ROIs ) and femoral neck narrowing ( FNN ) were measured after RHA .  BMD in the calcar increased to 107 % ( P<0.001 ) at one year and remained stable . Additional ROIs in the femoral neck and trochanter-area BMD changes fluctuated between 99.9 % and 104.1 % . FNN was minimal with a mean of 1.3 % at three years . After THA BMD decreased in the calcar to 80 % at one year ( P<0.001 ) and stabilized . This bone stock preserving nature of RHA must be weighed against potential disadvantages caused by specific metal-on-metal bearing problems BACKGROUND In the late 1990s , new developments in knee replacement were identified as a priority for research within the NHS . The newer forms of arthroplasty were more expensive and information was needed on their safety and cost-effectiveness . OBJECTIVES The Knee Arthroplasty Trial examined the clinical effectiveness and cost-effectiveness of four aspects of knee replacement surgery : patellar resurfacing , mobile bearings , all-polyethylene tibial components and unicompartmental replacement . DESIGN This study comprised a partial factorial , pragmatic , multicentre r and omised controlled trial with a trial-based cost-utility analysis which was conducted from the perspective of the NHS and the patients treated . Allocation was computer generated in a 1 : 1 ratio using a central system , stratified by eligible comparisons and surgeon , minimised by participant age , gender and site of disease . Surgeons were not blinded to allocated procedures . Participants were unblinded if they requested to know the prosthesis they received . SETTING The setting for the trial was UK secondary care . PARTICIPANTS Patients were eligible for inclusion if a decision had been made for them to have primary knee replacement surgery . Patients were recruited to comparisons for which the surgeon was in equipoise about which type of operation was most suitable . INTERVENTIONS Patients were r and omised to receive a knee replacement  with the following : patellar resurfacing or no patellar resurfacing irrespective of the design of the prosthesis used ; a mobile bearing between the tibial and femoral components or a bearing fixed to the tibial component ; a tibial component made of either only high-density polyethylene ( ' all polyethylene ' ) or a polyethylene bearing fixed to a metal backing plate with attached stem ; or unicompartmental or total knee replacement . MAIN OUTCOME MEASURES The primary outcome was the Oxford Knee Score ( OKS ) . Other outcomes were Short Form 12 ; EuroQol 5D ; intraoperative and postoperative complications ; additional surgery ; cost ; and cost-effectiveness . Patients were followed up for a median of 10 years ; the economic evaluation took a 10-year time horizon , discounting costs and quality -adjusted life-years ( QALYs ) at 3.5 % per annum . RESULTS A total of 116 surgeons in 34 centres participated and 2352 participants were r and omised : 1715 in patellar resurfacing ; 539 in mobile bearing ; 409 in all-polyethylene tibial component ; and 34 in the unicompartmental comparisons . Of those r and omised , 345 were r and omised to two comparisons . We can be more than 95 % confident that patellar resurfacing is cost-effective , despite there being no significant difference in clinical outcomes , because of increased QALYs [ 0.187 ; 95 % confidence interval ( CI ) -0.025 to 0.399 ] and reduced costs ( -£104 ; 95 % CI -£630 to £ 423 ) . We found no definite advantage or disadvantage of mobile bearings in OKS , quality of life , reoperation and revision rates or cost-effectiveness . We found improved functional results for metal-backed tibias : complication , reoperation and revision rates were similar . The metal-backed tibia was cost-effective ( particularly in the elderly ) , costing £ 35 per QALY gained . CONCLUSIONS The results provide evidence to support the routine resurfacing of the patella and the use of metal-backed tibial components even in the elderly . Further follow-up is required to assess the stability of these findings over time and to inform the decision between mobile and fixed bearings . TRIAL REGISTRATION Current Controlled Trials IS RCT N45837371 . FUNDING This project was funded by the NIHR Health Technology Assessment programme and the orthopaedic industry . It will be published in full in Health Technology Assessment ; Vol . 18 , No. 19 . See the NIHR Journals Library website for further project information BACKGROUND The purpose of the present study was to determine cobalt and chromium ion levels in the blood and urine of patients in whom a modern-generation metal-on-metal hip resurfacing device had been implanted . METHODS A total of ninety-seven patients with a Conserve Plus metal-on-metal hip resurfacing implant  were followed prospect ively for two years . Cobalt and chromium levels in erythrocytes , serum , and urine were measured preoperatively as well as three , six , twelve , and twenty-four months postoperatively . RESULTS The median serum cobalt and chromium ion levels were 1.04 μg/L ( range , 0.31 to 7.42 μg/L ) and 2.00 μg/L ( range , 0.28 to 10.49 μg/L ) , respectively , at one year after surgery and 1.08 μg/L ( range , 0.44 to 7.13 μg/L ) and 1.64 μg/L ( range , 0.47 to 10.95 μg/L ) , respectively , at two years after surgery . The corresponding mean levels ( and st and ard deviations ) of serum cobalt and chromium were 1.68 ± 1.66 μg/L and 2.70 ± 2.22 μg/L , respectively , at one year after surgery and 1.79 ± 1.66 μg/L and 2.70 ± 2.37 μg/L , respectively , at two years after surgery . CONCLUSIONS These levels compare favorably with other published ion results for metal-on-metal hip resurfacing and replacement implants . No pseudotumors or other adverse soft-tissue reactions were encountered in our study population . Further research is needed to determine the clinical importance of increased cobalt and chromium ion levels in serum and urine following metal-on-metal hip resurfacing This prospect i ve , r and omized , multicenter study of alumina ceramic-on-alumina ceramic bearing couples includes 452 patients ( 475 hips ) . Their average age was 53 years with approximately two thirds men and 82 % with osteoarthritis . At an average 8-year follow-up , clinical results were excellent and cortical erosions significantly less than in the conventional polyethylene-on-metal bearing group . Nine hips have undergone revision of one or both components for any reason . Of the 380 ceramic liners , 2 ( 0.5 % ) have fractured requiring reoperation , and 3 ( 0.8 % ) ceramic patients reported a transient squeaking sound , one of which had a head and liner change due to groin pain secondary to psoas tendinitis at 5 years . With no revisions for aseptic loosening and minimal cortical erosions , alumina-ceramic bearing couples are performing in a manner superior to the polyethylene-on-metal bearing in this young , active patient population Dislocation is a leading cause of revision after  total hip arthroplasty ( THA ) . To address this risk , dual-mobility technology was developed , which features a mobile polyethylene liner locked onto a femoral head and articulating in a metallic acetabular shell . This study reports clinical outcome data after implantation of the third-generation POLARCUP Dual-Mobility System ( Smith & Nephew Orthopaedics AG , Rotkreuz , Switzerl and ) .  Primary THA procedures were performed in 150 patients . At 7.1 years , cumulative cup survival according to Kaplan-Meier was 97.4 % . The mean Postel-Merle d'Aubigne score improved from 8.9 to 17.1 during the investigation . Two cups were revised at 5.4 and 6.4 years because of aseptic loosening . No dislocations were observed during follow-up . The current results confirm excellent early to midterm clinical outcomes for the POLARCUP Dual-Mobility System At the authors ' hospital , 410 primary total hip replacements were performed on 372 patients between September 1 , 1985 , and May 31 , 1989 . All hips were assigned r and omly to receive a Charnley prosthesis with an ogee flanged cup or a Spectron prosthesis with a metal backed cup .  Eleven-year survivor analysis , using revision as the end point definition of failure , revealed a survival rate of 93.2 % ± 5.8 % for the Charnley replacement and 95.9 % ± 3.0 % for the Spectron . If each component of the systems was analyzed ( concerning aseptic loosening ) , the ogee cup and the Spectron stem had 100 % survival . The survivorship for all 410 hips was 94.5 % ± 3.4 % . If the end point definition of failure was exp and ed to include patient dissatisfaction , the survival rate decreased to 86.3 % ± 4.9 % . These survival rates were compared with the rates obtained by the Swedish National Hip Registry . The national cohort included all patients in Sweden who were treated surgically with a Charnley ( 14,053 patients ) or Spectron ( metal backed cup ) prosthesis ( 726 patients ) between September 1 , 1985 , and May 31 , 1989 .  Eleven-year survivor analysis revealed a national survival rate of 92.1 % ± 0.7 % for the Charnley replacement and 88.6 % ± 6.1 % for the Spectron . The analyses from the Swedish Registry are based on more than 160,000 primary operations and 11,500 revisions . Despite the enormous amount of data , there are drawbacks , and registries never can replace the prospect i ve , r and omized trial . One reason is the Swedish National Registry is unable to discriminate between the individual cup and stem components when analyzing the cause of revision , and no clinical or radiographic information is collected . A potential drawback for the r and omized trial is performance bias because surgeons from specialized centers might perform better than the general orthopaedic surgeon There has been renewed interest for metal-on-metal hip resurfacing due to improved design and manufacturing of implants , better material s , 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 ) A total of 410 hips were r and omized to treatment with either a Charnley ( 206 hips ) or a Spectron ( 204 hips ) total hip arthroplasty .  The patients were operated on by a st and ardized procedure using a contemporary cementing technique and were followed after 1 , 3 , 5 to 6 , and 10 years . The postoperative radiographs showed a significantly increased rate of malalignment and consequently low grade of cement mantle quality of the Charnley stem compared to the Spectron . No differences concerning cement mantle quality or positioning were found between the Charnley ogee cup and the metal-backed Spectron . Evaluation of the follow-up radiographs revealed 10 loose Charnley stems and 1 loose Spectron stem and 4 loose Charnley ogee cups and 23 loose Spectron metal-backed cups . The differences of revision rate for the femoral and acetabular components of the 2 prostheses were significant ( P = .03 , Charnley femoral component more frequent ; P = .03 , Spectron acetabular component more frequent ) . The radiographic evaluation strengthened this disparity . Poor wear characteristics of the metal-backed Spectron cup are perhaps the main reason for the highly significant difference in mechanical failure rate between the 2 cups . We therefore propose that metal-backing of cemented cups should be avoided , at least when combined with larger femoral heads . The difficulty in positioning the Charnley stem with an adequate cement mantle , especially in the absence of trochanteric osteotomy , might explain the inferior Charnley stem longevity in this study We conducted a prospect i ve single-blinded r and omised controlled trial to compare the functional and quality of life outcomes in two groups of patients between 60 and 80 years of age undergoing THR ; the first receiving a small head ( 28–32 mm ) metal on polyethylene ( MoP ) articulation , and the second receiving a large head ( 44–54 mm ) metal on metal ( MoM ) articulation .  We recruited 49 patients and r and omised them into one of the two groups ( 22 MoP and 27 MoM ) . The results demonstrated no statistical difference in any of the assessed functional outcomes at any follow-up point ( p>0.05 ) . There were no dislocations or revisions in either group . Although it has been suggested that large head MoM articulations in THA offer superior stability and function , our results suggest that small head MoP articulations can achieve comparable ROM , function and quality of life at short-term follow-up Prospect i ve , r and omized studies must be performed when new surgical techniques or implants are evaluated . In this study , a new implant system was compared with the Charnley prosthesis , which over the years has been the most used hip implant in Sweden . Between 1985 and 1989 , 410 hips were r and omized to treatment with a Charnley or a Spectron total hip arthroplasty : 206 Charnley and 204 Spectron prostheses were implanted . The patients were operated on by a st and ardized procedure using a contemporary cementing technique . The patients were followed prospect ively by an independent observer after 1 , 3 , 5 to 6 , and 10 years . Harris Hip Score and patient satisfaction were recorded in the outcome evaluation . A total of 144 patients with 164 hips were deceased , and 15 patients ( 8 Charnley and 7 Spectron ) have required a revision . Nine hips were revised because of aseptic loosening ( 5 Charnley stems and 4 Spectron metal-backed cups ) . The Charnley stem as well as the metal-backed Spectron cup had a higher risk for revision because of aseptic loosening . The Charnley ogee cup and the Spectron stem have performed remarkably well with no revision of these components . Seven Charnley prostheses dislocated , but no dislocation was recorded in the Spectron group . Survivorship calculations with a mean follow-up of 10 years revealed an overall 11-year survivorship of 94.5 % + /- 3.4 % ( Charnley , 93.2 % + /- 5.8 % ; Spectron , 95.9 % + /- 3.0 % ) . The clinical outcome did not differ between the 2 systems . The overall results in this old population , using a contemporary surgical technique , illustrate that cemented hip arthroplasty is an excellent treatment alternative for elderly patients Ceramic-on-ceramic coupling is thought to be a durable alternative to metal- or alumina-on-polyethylene pairing . No evidence exists suggesting superior clinical and radiological results for hydroxyapatite-coated stems versus uncoated stems . The aim of this study is to report the performance of an alumina-on-alumina bearing  cementless total hip arthroplasty and to compare stems with a tapered design with and without hydroxyapatite coating . We prospect ively analysed the results of  cementless tapered femoral stems ( 40 hydroxyapatite-coated versus 22 uncoated stems ) , a metal-backed fibre mesh hydroxyapatite-coated socket and alumina-on-alumina pairing .  Of 75 hips studied , 62 were available for follow-up ( mean of 10.5 years after surgery ) . The average Harris hip score was 90 . Only one hydroxyapatite-coated stem was revised for aseptic loosening . One instance of non-progressive osteolysis was detected around a screw of a cup . All other components showed radiographic signs of stable ingrowth .  Hydroxyapatite coating of the stem had no significant impact on the clinical or radiological results . Total hip arthroplasty with the presented implant and pairing provides a durable st and ard for all patients requiring hip joint replacement against which all newer generations of cementless implants should be judged BACKGROUND Early reports on modern  ceramic-on-ceramic total hip replacements  have demonstrated excellent clinical and radiographic results with few cases of catastrophic failure , which , in the case of earlier design s , often had been caused by implant fracture . Several reports , however , have noted the presence of audible squeaking . The purpose of the present study was to determine the incidence of squeaking in association with the use of this bearing couple . METHODS During the period from March 2003 to May 2005 , three surgeons performed 159 total hip arthroplasties in 143 patients with use of a ceramic-on-ceramic bearing . One hundred and forty-nine hips ( 131 patients ) were available for review after at least one year of follow-up . These patients were followed prospect ively with use of the modified Hospital for Special Surgery hip score and a patient-administered question naire . Additionally , a control group of sixty hips ( forty-eight patients ) with a metal-on-polyethylene bearing  was matched to the ceramic group on the basis of age , sex , and body mass index to compare the incidence of squeaking and other noises . Radiographic evaluations were performed according to previously established criteria . RESULTS Fourteen ( 10.7 % ) of 131 patients described an audible squeak during normal activities . However , squeaking was reproducible clinical ly in only four patients , and only one patient complained of squeaking before being presented with the question naire . The average Hospital for Special Surgery score improved from 19.8 preoperatively to 38.4 at the time of the latest follow-up , indicating excellent clinical results . Ninety-five percent of the patients had a satisfaction score of > or = 8 of 10 . Three hips dislocated . One of those three hips squeaked and was revised because of recurrent dislocations . One patient was considering revision because of squeaking . In the matched metal-on-polyethylene cohort , there were no cases of squeaking . CONCLUSIONS The squeaking hip is a phenomenon that is unique to total hip replacements with hard-on-hard bearings . The incidence of squeaking in association with ceramic-on-ceramic bearings may be higher than previously reported as < 1 % of the patients in the present study reported this finding before being queried . The causes and implication s of squeaking are yet to be determined . The use of hard-on-hard bearings offers many advantages in terms of wear reduction , especially for young and active patients . Nonetheless , patients considering ceramic-on-ceramic bearings should be counseled with regard to this phenomenon Background The primary purpose of this r and omized controlled trial ( RCT ) was to compare knee-specific outcomes ( stiffness , pain , function ) between patellar retention and resurfacing up to 10 years after primary total knee arthroplasty ( TKA ) . Secondarily , we compared re-operation rates . Methods 38 subjects with non-inflammatory arthritis were r and omized at primary TKA surgery to receive patellar resurfacing ( n = 21 ; Resurfaced group ) or to retain their native patella ( n = 17 ; Non-resurfaced group ) . Evaluations were performed preoperatively , one , five and 10 years postoperatively by an evaluator who was blinded to group allocation . Self-reported knee-specific stiffness , pain and function , the primary outcomes , were measured by the Western Ontario McMaster Osteoarthritis Index ( WOMAC ) . Revision rate was determined at each evaluation and through hospital record review . Results 30 ( 88 % ) and 23 ( 72 % ) of available subjects completed the five and 10-year review respectively . Knee-specific scores continued to improve for both groups over the 10-years , despite diminishing overall health with no significant group differences seen . All revisions occurred within five years of surgery ( three Non-resurfaced subjects ; one Resurfaced subject ) ( p = 0.31 ) . Two revisions in the Non-resurfaced group were due to persistent anterior knee pain . Conclusions We found no differences in knee-specific results between groups at 5–10 years postoperatively . The Non-resurfaced group had two revisions due to anterior knee pain similar to rates reported in other studies . Knee-specific results provide useful postoperative information and should be used in future studies comparing patellar management strategies . Clinical Trials.gov BACKGROUND The aim of continued development of total knee replacement systems has been the further improvement of the quality of life and increasing the duration of prosthetic survival . Our goal was to evaluate the effects of several design features , including metal backing of the tibial component , patellar resurfacing , and a mobile bearing between the tibial and femoral components , on the function and survival of the implant . METHODS A pragmatic , multicenter , r and omized , controlled trial involving 116 surgeons in thirty-four centers in the United Kingdom was performed ; 2352 participants were r and omly allocated to be treated  with or without a metal backing of the tibial component ( 409 ) , with or without patellar resurfacing ( 1715 ) , and /or with or without a mobile bearing ( 539 ) . R and omization to more than one comparison was allowed . The primary outcome measures were the Oxford Knee Score ( OKS ) , Short Form-12 , EuroQol-5D , and the need for additional surgery . The results up to two years postoperatively are reported . RESULTS Functional status and quality -of-life scores were low at baseline but improved markedly across all trial groups following knee replacement ( mean overall OKS , 17.98 points at baseline and 34.82 points at two years ) . Most of the change was observed at three months after the surgery . Six percent of the patients had additional knee surgery within two years . There was no evidence of differences in clinical , functional , or quality -of-life measures between the r and omized groups at two years . CONCLUSIONS Patients have substantial improvement following total knee replacement . This is the first adequately powered r and omized controlled trial , of which we are aware , in which the effects of metal backing , patellar resurfacing , and a mobile bearing were investigated . We found no evidence of an effect of these variants on the rate of early complications or on functional recovery up to two years after total knee replacement Purpose Dislocation is a frequent complication in total hip arthroplasty ( THA ) revision . Cup fixation is the second concern . In order to know outcomes at two years , we prospect ively followed a continuous series of 78 patients to demonstrate that  cementless dual-mobility cup ( DMC ) used in revision THA  is safe as regards dislocation risk and bone fixation . Method We enrolled 78 consecutive patients ( 79 cases ) in a prospect i ve study . Mean interval between index surgery and revision was 12.9 years . Mean age at revision was 75.5 years . Two types of cementless DMC were used : a st and ard DMC in 68 cases with low- grade bone defect ( Paprosky grade 1 and 2 ) , and a specific design reconstruction DMC in 11 cases with severe bone loss ( Paprosky grade 3 ) . Results At two years of follow-up , 68 patients were review ed ; four were lost to follow-up . , and six patients were deceased . We identified three types of situations at risk : st and ard risk ( 33 cases ) , Paprosky grade 1 or 2 ; medium risk ( 37 cases ) , revision for recurrent instability ( 21 ) , periprosthetic fractures ( 14 ) or severe loosening Paprosky grade 3 without femorotomy ( 2 ) ; high risk ( nine cases ) , revision for severe loosening with a femorotomy . One ( 1.3 % ) patient dislocated her hip at one month without recurrence . Revision rate for dislocation was 0 % ; two ( 2.7 % ) early mechanical failures occurred . Conclusion Considering outcomes of this series , cementless DMC can be suggested in THA revision surgery There have been comparatively few studies of the incidence of osteolysis and the survival of hybrid and cementless total hip replacements ( THRs ) in patients younger than 50 years of age . We prospect ively review ed 78 patients ( 109 hips ) with a hybrid THR having a mean age of 43.4 years ( 21 to 50 ) and 79 patients ( 110 hips ) with a cementless THR with a mean age of 46.8 years ( 21 to 49 ) . The patients were evaluated clinical ly using the Harris hip score , the Western Ontario and McMaster Universities ( WOMAC ) osteoarthritis score and the University of California , Los Angeles ( UCLA ) activity score .  Radiographs and CT scans were assessed for loosening and osteolysis . The mean follow-up was for 18.4 years ( 16 to 19 ) in both groups . The mean post-operative Harris hip scores ( 91 points versus 90 points ) , the mean WOMAC scores ( 11 points versus 13 points ) and UCLA activity scores ( 6.9 points versus 7.1 points ) were similar in both groups . The revision rates of the acetabular component ( 13 % versus 16 % ) and the femoral component ( 3 % versus 4 % ) , and the survival of the acetabular component ( 87 % versus 84 % ) and the femoral component ( 97 % versus 96 % ) were similar in both groups . Although the long-term fixation of the acetabular metallic shell and the cemented and cementless femoral components was outst and ing , wear and peri-acetabular osteolysis constitute the major challenges of THR in young patients Background Polyethylene ( PE ) wear particles are believed to cause aseptic loosening and thereby impair function in hip arthroplasty .  Highly crosslinked polyethylene ( XLPE ) has low short- and medium-term wear rates . However , the long-term wear characteristics are unknown and it is unclear whether reduced wear particle burden improves function and survival of cemented hip arthroplasty . Questions / purpose sWe asked whether XLPE wear rates remain low up to 10 years and whether this leads to improved implant fixation , periprosthetic bone quality , and clinical function compared to conventional PE . Methods We r and omized 60 patients ( 61 hips ) to receive either PE or XLPE cemented cups combined with a cemented stem .  At 10 years postoperatively , 51 patients ( 52 hips ) were evaluated for polyethylene wear and component migration estimation by radiostereometry , for radiolucent lines , bone densitometry , and Harris hip and pain scores . Revisions were recorded . Results XLPE cups had a lower mean three-dimensional wear rate between 2 and 10 years compared to conventional PE hips : 0.005 mm/year versus 0.056 mm/year . We found no differences in cup migration , bone mineral density , radiolucencies , functional scores , and revision rate . There was a trend toward improved stem fixation in the XLPE group . The overall stem failure rate was comparably high , without influencing wear rate in XLPE hips . Conclusions XLPE displayed a low wear rate up to 10 years when used in cemented THA , but we found no clear benefits in any other parameters . Further research is needed to determine whether cemented THA design s with XLPE are less prone to stem loosening . Level of Evidence Level I , therapeutic study . See the Instructions for Authors for a complete description of levels of evidence Background  Total hip arthroplasty ( THA )  has been associated with high survival rates , but debate remains concerning the best fixation mode of THA . Questions / purpose sWe conducted a r and omized controlled trial ( RCT ) with 250 patients with a mean age of 64 years between October 1987 and January 1992 to compare the results of cementless and cemented fixation . Patients and Methods Patients were evaluated for revision of either of the components . One hundred twenty-seven patients had died ( 51 % ) and 12 ( 4.8 % ) were lost to followup . The minimum 17-year followup data ( mean , 20 years ; range , 17–21 years ) for 52 patients of the cementless group and 41 patients of the cemented group were available for evaluation . Results Kaplan-Meier survivorship analysis at 20 years revealed lower survival rates of cemented compared with cementless THA . The cementless tapered stem was associated with a survivorship of 99 % . Age younger than 65 years and male gender were predictors of revision surgery . Conclusions The efficacy of future RCTs can be enhanced by r and omizing patients in specific patient cohorts stratified to age and gender in multicenter RCTs . Including only younger patients might improve the efficacy of a future RCT with smaller sample sizes being required . A minimum 10-year followup should be anticipated , but this can be expected to be longer if the difference in level of quality between the compared implants is smaller . Level of Evidence Level I , therapeutic study . See Guidelines for Authors for a complete description of levels of evidence We conducted a prospect i ve study of the clinical and radiographic variables related to the survival of 114 cementless resurfacing double-cup hip replacements ( RHR ) with a mean follow-up of 9 ( range : 1 - -16 ) years . Three patients died , and 22 were unavailable for the final review in 2003 . Sixty-one RHRs had to be revised to a total hip replacement . Failure analysis of these revised RHRs showed femoral head and neck resorption under the prosthesis in 33 , acetabular protrusion in seven , both femoral and acetabular resorption in 14 and a femoral-neck fracture in three . One hip had dislocated , and there were three hips with unexplained pain . The Kaplan-Meier 5-year mean survival was 92 % , the 10-year survival was 47 % ( 95 % CI 37 - -57 % ) and the 15-year survival was 30 % ( 95 % CI 20 - -40 % ) . Pre-operative joint destruction ( grade 1 ) , a high degree of radiological osteoporosis , a body mass index > 25 and prosthesis mismatch were significantly related to failure of the RHR . We believe that in young , non-obese patients with pre-operative radiological central destruction but without severe proximal femoral osteoporosis , a resurfacing arthroplasty may have some value . Our failures were mainly due to femoral resorption under the prosthetic femoral component One hundred two patients with 131 consecutive cementless total knee arthroplasties that retained the posterior cruciate ligament were followed up prospect ively . The average age of the patients was 58 years ( range , 32–75 years ) . The mean followup on the surviving knee arthroplasties was 11 years ( range , 7–16 years ) . The patellar component was metal-backed in the first 112 ( 85 % ) knees , cementless all-polyethylene in the last 17 ( 13 % ) knees , and two knees had a prior patellectomy . Forty-four metal-backed patellar components ( 48 % ) were revised ; nine were loose , and 35 had polyethylene wear through . Thirteen femoral components ( 12 % ) were revised because of femoral abrasion from a failed metal-backed patellar component . No other femoral component was revised , loose , or had osteolysis develop . Nine ( 8 % ) tibial components had failure of ingrowth ; eight have been revised . Partial radiolucencies occurred in 53 % of the tibias . Thirteen ( 12 % ) small osteolytic lesions developed , all around screws or screw holes in the tibial components . At an average of 11 years followup , cementless fixation yielded mixed results : cementless femoral fixation was excellent and metal-backed patellar components had a 48 % patellar revision rate . Cementless tibial components had an 8 % aseptic loosening rate and a 12 % incidence of small osteolytic lesions . Based on these results , the authors have ab and oned cementless fixation in total knee arthroplasty Summary Production of inflammatory mediators ( IM ) by cells and specifically macrophages around loosened implants may be responsible for their loosening . Our hypothesis was that different material s give rise to different amounts of these IM . It is thought that alumina/alumina for total hip replacement ( THR ) , which has been used for 15 years in our orthopedic department , may produce less IM than other systems . We initiated a clinical prospect i ve study to measure the level of prostagl and in E2 ( PGE2 ) in tissue surrounding loosened prostheses to quantify PGE2 production regarding the types of material involved in the friction couple , i.e. , alumina/alumina versus metal/polyethylene , and the type of fixation , i.e. , cemented versus cementless . A total of 29 THR revisions were performed in 28 patients . Four implant groups were identified : alumina/alumina cemented , alumina/alumina cementless , metal/polyethylene cemented , and metal/polyethylene cementless . For each revision , tissues surrounding the failed implants were harvested and processed , and the PGE2 was measured in a blind manner using an immunoassay technique . As the measuring technique was difficult , at least three determinations for each sample were necessary . Some sample s were excluded from the analysis for various reasons , for example , second or further revisions involving many different material s in the past , conjunction of metallic and alumina debris and sample s taken from nonloosened components . Finally , 15 sample s were considered adequate for inclusion in this study . Two groups were analyzed and compared : the alumina/alumina couple and the metal/polyethylene couple . Tissue surrounding the first group demonstrated a PGE2 level of 69 ± 56 fmol/mg wet weight compared to 202 ± 156 fmol/mg for the second . The Wilcoxon test was applied , and there was a statistical difference ( P < 0.05 ) . When the alumina/alumina cemented group was compared to the alumina/alumina cementless group , there was a tendency to less PGE2 with the cemented , but the difference was not statistically significant . Results thus demonstrate that alumina/alumina produces less IM than metal/polyethylene . However , these results do not indicate whether this is related to the type of debris , the amount , or both . This remains a preliminary study . Further studies with more sample s , other mediators and growth factors , and a precise comparison to histological findings are still necessary BACKGROUND The use of larger femoral heads has been proposed to reduce the risk of dislocation after total hip arthroplasty , but there is a lack of evidence to support this proposal . The aim of this multicenter r and omized controlled trial was to determine whether the incidence of dislocation one year after total hip arthroplasty is significantly lower in association with the use of a 36-mm femoral head articulation as compared with a 28-mm articulation . METHODS Six hundred and forty-four middle-aged and elderly patients undergoing primary or revision arthroplasty were r and omized intraoperatively to receive either a 36 or 28-mm metal femoral head on highly cross-linked polyethylene .  Patients who were at high risk of dislocation ( including those with dementia and neuromuscular disease ) and those undergoing revision for the treatment of recurrent hip dislocation or infection were excluded . Patients were stratified according to other potential risk factors for dislocation , including diagnosis and age . Diagnosis of hip dislocation required confirmation by a physician and radiographic evidence of a dislocation . RESULTS Overall , at one year of follow-up , hips with a 36-mm femoral head articulation had a significantly lower incidence of dislocation than did those with a 28-mm articulation ( 1.3 % [ four of 299 ] compared with 5.4 % [ seventeen of 316 ] ; difference , 4.1 % [ 95 % confidence interval , 1.2 % to 7.2 % ] ) when controlling for the type of procedure ( primary or revision ) ( p = 0.012 ) . The incidence of dislocation following primary arthroplasty was also significantly lower for hips with a 36-mm femoral head articulation than for those with a 28-mm articulation ( 0.8 % [ two of 258 ] compared with 4.4 % [ twelve of 275 ] ; difference , 3.6 % [ 95 % confidence interval , 0.9 % to 6.8 % ] ) ( p = 0.024 ) . The incidence of dislocation following revision arthroplasty was 4.9 % ( two of forty-one ) for hips with a 36-mm articulation and 12.2 % ( five of forty-one ) for hips with a 28-mm articulation ; this difference was not significant with the relatively small sample size of the revision group ( difference , 7.3 % [ 95 % confidence interval , -5.9 % to 21.1 % ] ) ( p = 0.273 ) . CONCLUSIONS Compared with a 28-mm femoral head articulation , a larger 36-mm articulation result ed in a significantly decreased incidence of dislocation in the first year following primary total hip arthroplasty . However , before a 36-mm metal-on-highly cross-linked polyethylene articulation is widely recommended , the incidence of late dislocation , wear , periprosthetic osteolysis , and liner fracture should be established There is no published literature to support mid to long term results of hip resurfacing ( HR ) arthroplasty in patients over the age of 70 years . The purpose of our study was to evaluate the function HR in this age group ( 70 or older at the time of surgery ) at medium to long term follow-up . Between July 1997 and November 2002 , the Oswestry Outcome Centre independently and prospect ively collected data on 5000 Birmingham Hip Resurfacings ( BHRs ) . 106 had been implanted in elderly patients who were 70 years of age or older . The post-operative Harris and Merle D'Aubigné and Postel ( MDP ) hip scores and causes for revision were used to ascertain function and implant survival . Hip scores for the older BHR patients were compared with those from younger patients . The average age at surgery of the elderly BHR cohort was 73.2 years ( range , 70.0 to 87.9 years ) with a mean follow-up of 7.1 years ( range , 0.5 to 10.9 years ) . Four patients had a femoral neck fracture and required conversion to a conventional total hip replacement . There were no patients lost to follow-up and no dislocations in this series . The median Harris hip score ( HHS ) was significantly better in the younger BHR group compared with the elderly BHR group , ( 96 vs. 94 p=0.008 ) . There was no significant difference in recovery rates after surgery . There was a significantly higher rate of revision in women than men among the elderly patients ( male= 1 of 65 ( 1.5 % ) ; women = 3 of 19 ( 15.8 % ) , p=0.03 ) . At latest follow-up the elderly patients continued to function well when compared with the younger BHR patients . There was a high mid to long term success rate after HR in patients who were 70 years of age or older , without the failure burden possibly anticipated . Elderly patients had a poorer functional outcome , but a difference in HHS of two points may be of only minor clinical significance 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 r and omized , 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 r and omized 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 Although the published studies on the outcomes of  total hip arthroplasty (  THA ) performed with currently available ceramic components show high survivorship and low bearing wear at midterm followup , concern over ceramic fracture and squeaking persist . For these reasons , the use of ceramic is limited . Recently , a new alumina matrix composite material ( Delta ceramic ) with improved material properties was developed to address these concerns . We report the early outcomes and complications of a prospect i ve , r and omized , multicenter trial of 263 patients ( 264 hips ) at eight centers , comparing a Delta ceramic-on-ceramic ( COC ) articulation with a Delta ceramic head-crosslinked polyethylene bearing combination ( COP ) . There were 177 COC hips and 87 COP hips . Complications  were reported for all patients , whereas  clinical and radiographic results were provided for the 233 patients with minimum 2-year followup ( average , 31.2 months ; range , 21–49 months ) . The Harris hip scores and clinical , radiographic , and survivorship outcomes were similar in both groups . There were four ( 2 % ) revisions in the COC group and two ( 2 % ) in the COP group . We encountered three intraoperative ceramic liner-related events . In addition , one patient receiving the COC underwent revision for chipping of the ceramic liner , and a second had ceramic fragmentation on followup radiographs but has not undergone revision . These liner related complications remain a concern . No patient reported squeaking in either group ; this leaves us hopeful the new material will lessen the frequency of squeaking . In the short term , the Delta COC articulation provided similar functional scores and survivorship and complication rates with the ceramic head mated with crosslinked polyethylene . Level of Evidence : Level I , therapeutic study . See Guidelines for Authors for a complete description of levels of evidence This study determined how ceramic-on-ceramic bearing THA affected joint-specific pain , function and stiffness in the first five postoperative years compared with ceramic-on-highly-crosslinked-polyethylene bearing THA .  Subjects less than 61 years of age were r and omized  to ceramic-on-ceramic ( CERAMIC ) [ n = 48 ] or ceramic-on-highly-crosslinked-polyethylene ( POLYETHYLENE ) [ n = 44 ] bearing THA . Subjects were assessed using the Western Ontario McMaster Osteoarthritis Index ( WOMAC ) and the R AND 12-Item Health Survey ( R AND -12 ) preoperatively , and at one and five years postoperatively . 92 subjects(50 ( 54 % ) males ; average age = 52 ( SD 6.6 ) years ) were enrolled . 78 ( 85 % ) subjects returned five years postoperatively . All subjects reported improvements at one and five years in all measured indices with no group differences detected . Seven ( 8 % ) subjects experienced postoperative THA complications , none related to bearing surfaces ; two subjects ( POLYETHYLENE ) required revision for instability . Both bearing surfaces provided excellent short-term results in younger subjects Purpose To evaluate early performance of contemporary dual mobility acetabular systems with second generation annealed highly cross-linked polyethylene for primary hip arthroplasty of patients under 55 years of age . Methods A prospect i ve observational five years study across five centers in Europe and the USA of 321 patients with a mean age of 48.1 years was performed . Patients were assessed for  causes of revision , hip instability , intra-prosthetic dissociation , Harris hip score and radiological signs of osteolysis .  Results There were no dislocations and no intra-prosthetic dissociations . Kaplan Meier analysis demonstrated 97.51 % survivorship for all cause revision and 99.68 % survivorship for acetabular component revision at five years . Mean Harris hip score was 93.6 . Two acetabular shells were revised for neck-rim implant impingement without dislocation and ten femoral stems were revised for causes unrelated to dual mobility implants . Conclusion Contemporary highly cross-linked polyethylene dual mobility systems demonstrate excellent early clinical , radiological , and survivorship results in a cohort of patients that dem and high performance from their implants . It is envisaged that DM and second generation annealed HXLPE may reduce THA instability and wear , the two most common causes of THA revision in hip arthroplasty Background and purpose Femoral deformity associated with osteoarthritis is a challenge for both the surgeon and the implant . Many of the patients with these deformities are young . St and ard implants can be difficult to fit into these femurs . We prospect ively evaluated the outcome of custom uncemented femoral stems in young patients . Methods 61 consecutive patients ( 72 hips ) underwent surgery for osteoarthritis because of femoral deformity at a mean age of 35 ( 22–40 ) years . The patients received a CT3D-A custom-made femoral stem and an uncemented cup . The mean follow-up time was 14 ( 10–16 ) years . 2 patients died at 7 and 8 years after surgery , otherwise , none of the patients were lost to follow-up . Results At follow-up , the femoral prosthesis had not been revised in 59 patients ( 70 hips ) . 3 patients ( 3 hips ) had required revision surgery due to loosening of the acetabular component ; 2 hips were awaiting revision surgery for loosening of the acetabular cup . There were no cases of dislocation or infection . At review , all stems were considered stable according to the radiographic criteria . No migration or subsidence was observed on plain radiographs . Interpretation Our results are comparable to published results of custom stems regarding survival and outcome . Considering the young age and the deformities in this series of uncemented custom femoral stems , and the fact that there was follow-up of up to 16 years , the survival is remarkable . This technique appears to be a reasonable alternative in younger patients with femoral deformities Patellar resurfacing in total knee arthroplasty remains controversial . This study compared the long-term clinical outcomes of total knee arthroplasties performed with and without the patella resurfaced and is an up date of a previous report . Eighty-six patients ( 118 knees ) underwent primary total knee replacement  and were r and omized into two groups : those treated with and those treated without resurfacing of the patella . Outcomes included the scores according to the Knee Society clinical rating system , the scores according to a forty-one- question patellofemoral-specific patient question naire , patient satisfaction , global and anterior knee pain scores , radiographic findings , and complications and revisions .  Fifty-seven patients ( seventy-eight knees ) were followed for a minimum of ten years . No significant differences were identified between the two groups in terms of the range of motion , Knee Society scores , satisfaction , global knee pain , or anterior knee pain . The overall revision rates in the original series of 118 knees were 12 % in the nonresurfacing group and 9 % in the resurfacing group . Seven patients ( 12 % ) in the nonresurfacing group and two patients ( 3 % ) in the resurfacing group underwent revision for a reason related to a patellofemoral problem . On the basis of these findings , we concluded that , with the type of total knee arthroplasty used in our patients , similar results may be achieved with and without patellar resurfacing 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 , r and omised 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 question naires . 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 r and omly 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 can not definitively exclude clinical ly 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 IS RCT N33354155 , UKCRN 4093
Conclusions Revisions and reoperations are more frequent and occur earlier with metal-on-metal hip resurfacing , except when discontinued devices are removed from the analyses .
Background Metal-on-metal hip resurfacing was developed for younger , active patients as an alternative to THA , but it remains controversial .
Study heterogeneity , inconsistent outcome definitions , and unst and ardized outcome measures challenge our ability to compare arthroplasty outcomes studies .
Questions / purpose sWe asked how early revisions or reoperations ( within 5 years of surgery ) and overall revisions , adverse events , and postoperative component malalignment compare among studies of metal-on-metal hip resurfacing with THA  among patients with hip osteoarthritis .
Secondarily , we compared the revision frequency identified in the systematic review with revisions reported in four major joint replacement registries .