Use Of Total Hip Arthroplasty Research Articles

CORR Insights ®: Metal-on-conventional total hip arthroplasty bearing surfaces have a higher risk of revision than metal-on-highly crosslinked polyethylene: results from a US registry.

H ighly crosslinked polyethylene (XLPE) has essentially supplanted conventional polyethylene for use in total hip arthroplasty (THA) during the past decade. There now exists good evidence to demonstrate a clear reduction in femoral head penetration (and presumably polyethylene wear) and periprosthetic osteolysis associated with the use XLPE compared to conventional polyethylene in THA [2, 3]. While the annual reports of Australian Orthopaedic Association National Joint Replacement Registry continue to show the clinical benefits of XLPE (demonstrating a reduction in revision rates) [1], other investigators have not demonstrated a clear reduction in revision rates with the use of XLPE at mid-term followup [4]. The current study by Paxton and colleagues attempts to demonstrate the clinical benefits resulting from the use of XLPE compared to conventional polyethylene through the analysis of a large US-based patient database. Their findings demonstrate that, for two specific implant designs, the revision rate was significantly decreased for XLPE compared to the use of conventional polyethylene. Therefore, this work essentially confirms the experience reported by the Australian Orthopaedic Association National Joint Replacement Registry during the past decade. While important work, this study is limited by the observational nature of the study, inherent to all registry or database analysis, and only provides information about two specific hip designs (both of which having been replaced by more recent designs by their respective manufacturers). Furthermore, analysis of this type does not provide any radiological, functional or patient-derived outcomes This CORR Insights is a commentary on the article ‘‘Metal-on-conventional Total Hip Arthroplasty Bearing Surfaces Have a Higher Risk of Revision Than Metal-on-highly Crosslinked Polyethylene: Results From a US Registry’’ by Paxton and colleagues available at: DOI: 10.1007/s11999-014-4105-9 The author certifies that he, or any member of his immediate family, has no funding or commercial associations (eg, consultancies, stock ownership, equity interest, patent/ licensing arrangements, etc.) that might pose a conflict of interest in connection with the submitted article. All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research editors and board members are on file with the publication and can be viewed on request. The opinions expressed are those of the writers, and do not reflect the opinion or policy of CORR or the Association of Bone and Joint Surgeons. This CORR Insights comment refers to the article available at DOI: 10.1007/s11999-0144105-9

Survivorship of hip and knee implants in pediatric and young adult populations: analysis of registry and published data.

One of the least researched areas in orthopaedic pediatrics is the safety and effectiveness of joint replacement, in part because it is uncommon and is undertaken for a wide range of conditions not common for adult joint replacement. This study used data from the AOANJRR (Australian Orthopaedic Association National Joint Replacement Registry) to analyze the use of total hip arthroplasty (THA) and total knee arthroplasty (TKA) in the pediatric population and to provide preliminary data on the outcome of these procedures. The AOANJRR, which is part of the ICOR (International Consortium of Orthopaedic Registries), provided information on pediatric procedures reported to the registry by hospitals undertaking arthroplasty procedures in Australia. All THA and TKA procedures reported to the registry from 1999 to 2012 were included. The cumulative percent revision and the hazard ratio from Cox proportional-hazards models were used for analysis. All tests were two-tailed, with a 5% level of significance. Additionally, an overview of the literature is presented to provide a point of reference. Primary conventional THA was performed in 297 patients twenty years of age or younger; the cumulative percent revision at five years was 4.5%. Primary conventional THA was performed in 975 young adults twenty-one to thirty years of age; the cumulative percent revision at five years was 5.4%. Primary THA was performed in 105 patients twenty years of age or younger; the cumulative percent revision at five years was 4.6%. Primary TKA was performed in 159 young adults twenty-one to thirty years of age; the cumulative percent revision at five years was 10.3%. Compared with older adults, pediatric patients and young adults undergoing THA and TKA have very different diagnoses, including a high prevalence of tumor. Although the reported rate of revision surgery is currently similar to that for older patients, the number of reported procedures and the follow-up period remain limited. It is important for registries to continue to collect and analyze data relevant to this cohort and to coordinate these activities in order to better understand the safety and effectiveness of joint arthroplasty in the pediatric population.

Early Intraprosthetic Dislocation of Dual-Mobility Total Hip Arthroplasty Implant Following Attempted Closed Reduction: A Case Report

Introduced in 1974 by Bousquet, the dual-mobility bearing for use in total hip arthroplasty (THA) confers increased jump distance and improved overall stability relative to conventional THA designs [1-3]. The dual-mobility bearing incorporates a relatively small (22-28mm) metal or ceramic femoral head press fit into a larger polyethylene liner which articulates with the acetabular component. Dissociation of the femoral head from the polyethylene liner (intraprosthetic dislocation) is a known late complication thought to be related to polyethylene liner wear and has been previously reported [2-7]. In a consecutive series of 384 primary THAs employing Bousquet’s original design, there were 14 intraprosthetic dislocations over 15 years (3.6%). The authors cited polyethylene wear as causative and mean time to intraprosthetic dislocation was 8.9 years [2].

Early Intraprosthetic Dislocation of Dual-Mobility Total Hip Arthroplasty Implant Following Attempted Closed Reduction: A Case Report

Introduced in 1974 by Bousquet, the dual-mobility bearing for use in total hip arthroplasty (THA) confers increased jump distance and improved overall stability relative to conventional THA designs [1-3]. The dual-mobility bearing incorporates a relatively small (22-28mm) metal or ceramic femoral head press fit into a larger polyethylene liner which articulates with the acetabular component. Dissociation of the femoral head from the polyethylene liner (intraprosthetic dislocation) is a known late complication thought to be related to polyethylene liner wear and has been previously reported [2-7]. In a consecutive series of 384 primary THAs employing Bousquet’s original design, there were 14 intraprosthetic dislocations over 15 years (3.6%). The authors cited polyethylene wear as causative and mean time to intraprosthetic dislocation was 8.9 years [2].

(v) Computer assisted navigation in primary total hip arthroplasty

Abstract Computer Assisted Surgery (CAS) is an important development in orthopaedic surgery. While its use in total hip arthroplasty is recent, it has led to significant changes in the surgeon's perception of the procedure, allowing visualization of stages of the operation that previously had to be inferred, such as cup position during acetabular reaming and femoral stem orientation, making surgery more accurate and reproducible.

Changing trends in the treatment of femoral neck fractures: a review of the american board of orthopaedic surgery database.

The purpose of this study was to investigate the trends in operative management of femoral neck fractures by orthopaedic surgeons applying for board certification. We queried the American Board of Orthopaedic Surgery database to identify all femoral neck fractures that had been treated and reported by candidates taking Part II of the licensing examination from 1999 to 2011 to determine the utilization of internal fixation, hemiarthroplasty, and total hip arthroplasty. The longitudinal trends were then stratified by patient age (younger than sixty-five, sixty-five to seventy-nine, eighty and older) and the declared subspecialty of the candidate. There were 19,541 femoral neck fractures that had been treated by 4450 board certification candidates. The use of total hip arthroplasty increased over time (0.7% of fractures in 1999, 7.7% in 2011, p < 0.001); use of hemiarthroplasty (67.1% in 1999, 63.1% in 2011, p = 0.020) and internal fixation (32.2% in 1999, 29.2% in 2011, p = 0.064) declined slightly. All geographic regions showed an increase in utilization of total hip arthroplasty, with substantial variation between locations. The proportion of patients younger than age sixty-five who were managed with total hip arthroplasty increased from 1.4% to 13.1% (p < 0.001). Candidates with a declared subspecialty of "adult reconstruction" showed a strong trend toward the use of total hip arthroplasty (4.3% from 1999 to 2002, 21.1% from 2009 to 2011, p < 0.001), while "trauma" subspecialty candidates demonstrated decreasing utilization of internal fixation (40.9% from 1999 to 2002, 32.9% from 2009 to 2011, p = 0.012). The percentage of candidates treating at least one femoral neck fracture decreased from 54.8% from 1999 to 2002 to 46.3% from 2009 to 2011 (p < 0.001). The most substantial changes in treatment of femoral neck fractures were seen in the younger group of patients. Currently, a smaller percentage of board certification candidates are treating femoral neck fractures than those in the past, possibly reflecting a trend toward specialty care.

Femoral neck modularity: A bridge too far

Modular femoral neck use in total hip arthroplasty (THA) affords the operating surgeon increased intra-operative flexibility with regard to offset, version, and leg length. Proponents also advocate a reduced dislocation rate, reduced impingement issues, and ease of revision of acetabular component, head, or neck. However, the increased intra-operative flexibility and potential postoperative advantages come at a significant price. Adverse events and complications associated with modular femoral neck usage are being reported with increasing frequency. Modular femoral neck fractures as a result of patient- and implant-related factors are prevalent. Corrosion at the neck–stem interface is associated with a number of sequelae, including osteolysis, synovitis, adverse local tissue reactions (ALTRs), and aseptic lymphocyte-laminated vascular-associated lesions (ALVAL). Systemic complications of metallosis are also pertinent following corrosion at the neck–stem junction. Failure to disassemble the neck from the stem due to corrosion and cold welding is a documented complication and obviates a potential benefit of modularity at the time of revision. Modular femoral necks have a twofold increase in overall revision rate in the Australian registry data as compared to fixed-neck stems. Lastly, modular femoral necks add significant cost to each THA. The purpose of this review article is to discuss the current state of femoral neck modularity and provide the readership with pause prior to the continued use of modular femoral neck THA. Given the current and emerging literature, the modular femoral neck is a bridge too far.

Metal on Metal Total Hip Arthroplasty Using Modular Acetabular Shells

Metal on metal bearings were reintroduced into the United States for use in total hip arthroplasty approximately a decade ago. We evaluated a consecutive series cohort of 148 patients with 169 hips who underwent THR using a metal on metal bearing surface with a modular acetabular shell that had fixation augmentation with dome screws. At 3 to 8year follow-up, average 4.7years, only one component was revised (for femoral loosening). 3 hips demonstrated proximal femoral osteolysis and 3 hips demonstrated pelvic osteolysis. The average follow-up Harris Hip Score was 94 (range, 57–100). Although the results have been excellent, we continue to closely monitor these hips for any long term failures, or concerns.

End-stage Posttraumatic Osteoarthritis Treated With THA in Osteogenesis Imperfecta

Osteogenesis imperfecta is an incurable genetic disorder manifested with altered bone quality that predisposes patients to a multitude of fractures throughout their lives, including acetabular fractures. The management of acetabular fractures in patients with osteogenesis imperfecta remains a challenging clinical problem, with a paucity of literature supporting treatments and their outcomes. Limited reports in the literature validate the use of total hip arthroplasty (THA) in patients with osteogenesis imperfecta, and they describe the adult population only.This article describes a case of delayed diagnosis of a transverse acetabular fracture and femoral head impaction fracture that led to posttraumatic end-stage hip osteoarthritis in a 16-year-old boy with osteogenesis imperfecta (Sillence Type I) that was sustained after minimal trauma. Clinical examination 3 months postinjury revealed a significant pelvic obliquity, severe pain with hip range of motion, and limited hip range of motion. Imaging studies revealed a complete loss of articular cartilage and significant joint effusion.The patient underwent THA. No postoperative complications occurred. Two-year follow-up showed an excellent clinical result. The patient's hip was pain free, and he was able to walk with no limp.The authors are unaware of any reported cases of children with osteogenesis imperfecta undergoing THA. Based on the reported literature and the authors' experience, THA can be a reliable surgical option for patients with osteogenesis imperfecta.

Intra- and extra-articular planes of reference for use in total hip arthroplasty: a preliminary study.

Acetabular component malalignment in total hip arthroplasty can lead to potential complications such as dislocation, component impingement and excessive wear. Computer-assisted orthopaedic surgery systems generally use the anterior pelvic plane (APP). Our aim was to investigate the reliability of anatomical landmarks accessible during surgery and to define new potential planes of reference. Three types of palpations were performed: virtual, on dry bones and on two cadaveric specimens. Four landmarks were selected, the reproducibility of their positioning ranging from 0.9 to 2.3 mm. We then defined five planes and tested them during palpations on two cadaveric specimens. Two planes produced a mean orientation error of 5.0° [standard deviation (SD 3.3°)] and 5.6° (SD 2.7°). Even if further studies are needed to test the reliability of such planes on a larger scale in vivo during surgery, these results demonstrated the feasibility of defining a new plane of reference as an alternative to the APP.

Verwendungsraten von Prothesen der unteren Extremität in Deutschland und der Schweiz

In the United States the use of total hip arthroplasty (THA) has substantially increased over the last decade. It is not known, however, if this trend can be applied to other countries as well. The aim of the current study was therefore a detailed comparison of hip, knee, and ankle arthroplasty utilization rates in Germany and Switzerland in the years 2005-2008 and a secondary comparison with the United States.Based on datasets from the national statistical offices the number of inhabitants, gender and age distributions and the number of primary and revision surgeries were determined. These figures served for calculating primary, revision and overall surgical volumes, revision burden, primary and revision rates per 100,000 inhabitants, gender and age-specific primary and revision rates. A comparably smaller dataset was provided for the respective US analyses.In Germany, Switzerland and the US the number of implanted total and partial hip arthroplasties per 100,000 inhabitants rose from 235.8, 238.2 and 116.8 in 2005 to 254.7, 262.7 and 127.3 in 2008, respectively. For total and partial knee arthroplasty the rates were 156.3, 140.1 and 178.2 implantations in 2005 and 188.3, 176.8 and 213.6 in 2008, respectively. With 13.6% the revision burden in Germany was 3.6% higher than in Switzerland and accounted for 11.2% in the US. In 2008 it was 15.1% in Germany, was hence 4.6% higher than in Switzerland and remained stable at 11.2% in the US. For knee replacements the 2005 German revision burden was 11.1% which was 3.5% higher than in Switzerland and was 7.4% in the US. In 2008 it was 12.8% in Germany and 4.2% lower in Switzerland and in the US it accounted for 8.9%. In all three countries the revision burden for knee arthroplasty was constantly lower than for hip arthroplasty.In all three countries the primary rates for hip and knee replacements rose over the years but those for knee arthroplasty to a higher extent. The 2008 revision burden was highest in Germany for both types of arthroplasty. In Switzerland there was a transient revision burden decrease with a new increase from the year 2007 onwards. The US hip replacement utilization rates per 100,000 inhabitants were considerably lower than those in Germany and Switzerland and for knee replacements they were slightly higher.

Excellent Survivorship With the Use of Proximally Coated Tapered Cementless Stems for Total Hip Arthroplasty in Octogenarians

The use of total hip arthroplasty (THA) continues to grow partially because of the increasing life expectancy of the American population. Whether to use cemented or cementless femoral fixation options in older patients is often debated. The purpose of the present study was to compare the clinical and radiographic outcomes after cementless THA in patients ≥80 years to younger patients. Clinical and radiographic data were gathered on 33 patients (35 hips) all 80 years or older who had undergone proximally coated cementless total hip arthroplasties. Outcomes were compared with a matching group for age, body mass index, and diagnosis, who had undergone the same procedure by the same surgeon at a similar time. Harris hip scores were evaluated pre- and postoperatively, and radiographs were reviewed for evaluation of fixation and stability. At a mean follow-up of 4 years, 97% of the hips (34 of 35) remained unrevised and the mean Harris hip score had improved by 39 points to 83 points (range, 26-100 points). On radiographic evaluation, 91% were found to have full bony ingrowth, with 1 hip having osteolysis of the proximal femur. Mortality was 23% at 86 months. Except for mortality, the outcomes and complication rates were similar to the younger group except that the matching group had higher final postoperative Harris hip scores. Proximally coated tapered cementless THA is a safe and efficacious method for providing good clinical outcomes with low revision rates in patients 80 years of age or older.

A Population-Based Study of Trends in the Use of Total Hip and Total Knee Arthroplasty, 1969-2008

To study the rates of use of total hip arthroplasty (THA) and total knee arthroplasty (TKA) during the past 4 decades. The Rochester Epidemiology Project was used to identify all Olmsted County, Minnesota, residents who underwent THA or TKA from January 1, 1969, through December 31, 2008. We used a population-based approach because few data are available on long-term trends in the use of THA and TKA in the United States. Rates of use were determined by age- and sex-specific person-years at risk. Poisson regression was used to assess temporal trends by sex and age group. The age- and sex-adjusted use of THA increased from 50.2 (95% confidence interval [CI], 40.5-59.8) per 100,000 person-years in 1969-1972 to 145.5 (95% CI, 134.2-156.9) in 2005-2008, whereas TKA increased markedly from 31.2 (95% CI, 25.3-37.1) per 100,000 person-years in 1971-1976 to 220.9 (95% CI, 206.7-235.0) in 2005-2008. For both procedures, use was greater among females, and the rate generally increased with age. In this community, TKA and THA use rates have increased steadily since the introduction of the procedures and continue to increase for all age groups. On the basis of these population-based data, the probable need for TKA and THA exceeds current federal agency projections.

Mechanical characterization of nacre as an ideal-model for innovative new endoprosthesis materials

To mimic the impressive mechanical behavior of natural ceramics for technical or biomedical applications, interest has been focused on nacre, a natural composite consisting of imbricated aragonite platelets embedded in a protein matrix. Nacre is an ideal model material for implants, since it possesses favorable strength and toughness properties compared to the component materials of which it is composed. The focus of the present study was to test standardized parameters which are good indicators of the material's suitability as an implant material. A three-point bending test was performed on polished nacre samples according to international standards for Young's modulus, bending strength and fracture toughness. A total of 60 nacre samples were tested, with 5 samples each in 4 states of hydration (dry, distilled water, 0.9% NaCl and sea water). As a basis for comparison, 10 samples of a newly developed bioceramic material were tested for fracture toughness. The fracture toughness of nacre tended to be higher for specimens conditioned in 0.9% NaCl than for dry specimens (5.3 ± 0.6 vs. 4.3 ± 0.7 MPam(1/2), p = 0.061). The fracture toughness of the bioceramic investigated was observed to be somewhat higher than nacre (5.8 ± 0.4 vs. 4.3 ± 0.7 MPam(1/2), p ≤ 0.001). The increase in fracture toughness of hydrated nacre was not as large as would be expected based on the difference in stiffness of the matrix material after hydration that has been reported. Modulus and toughness were similar to published values and the fracture toughness observed was somewhat higher than reported for alumina implant ceramics, which are in use in total hip arthroplasty. In a direct comparison, we found that a newly developed alumina bioceramic material can in fact match nature in terms of fracture toughness.

Tribological and surface analysis of 38mm alumina–as-cast Co–Cr–Mo total hip arthroplasties

There is currently much discussion over the use of ceramic femoral components against metal acetabular cups, for use in total hip arthroplasty. The current study investigates six hot isostatically pressed alumina femoral heads of 38 mm diameter articulating against six as-cast Co-Cr-Mo metallic acetabular cups. Standard walking-cycle simulator wear testing was carried out to 5 x 10(6) cycles using the Durham Mark II hip wear simulator, and wear was determined gravimetrically. In addition, surface topography, using a non-contacting profilometer, an atomic force microscope, and an optical microscope, was monitored throughout the wear test. The wear of the ceramic heads was found to be undetectable using the current gravimetric method; however, a change in the surface topography was seen, as grain removal on the pole was observed through atomic force microscopy analysis. A biphasic wear pattern was found for the metallic cups, with low wear rates of 1.04 +/- 0.293 mm3/10(6) cycles (mean, +/- 95 per cent confidence interval) and 0.0209 +/- 0.004 mm3/10(6) cycles (mean, +/- 95 per cent confidence interval) for running-in and steady state wear phases respectively. Frictional measurement revealed that the joints were tending towards full fluid-film lubrication in parts of the walking cycle. The results show that the combination of hot isostatically pressed alumina and as-cast Co-Cr-Mo is a promising alternative for total hip arthroplasties.

Impact of body mass on hospital resource use in total hip arthroplasty

To determine the impact of BMI on post-operative outcomes and resource utilization following elective total hip arthroplasty (THA). A retrospective cohort analysis on all primary elective THA patients between 1996 and 2004. Primary outcomes investigated using regression analyses included length of stay (LOS) and costs (US dollars). Mayo Clinic Rochester, a tertiary care centre. Patients were stratified by pre-operative BMI as normal (18.5-24.9 kg/m(2)), overweight (25.0-29.9 kg/m(2)), obese (30.0-34.9 kg/m(2)) and morbidly obese (> or =35.0 kg/m(2)). Of 5642 patients, 1362 (24.1 %) patients had a normal BMI, 2146 (38.0 %) were overweight, 1342 (23.8 %) were obese and 792 (14.0 %) were morbidly obese. Adjusted LOS was similar among normal (4.99 d), overweight (5.00 d), obese (5.02 d) and morbidly obese (5.17 d) patients (P = 0.20). Adjusted overall episode costs were no different (P = 0.23) between the groups of normal ($17,211), overweight ($17,462), obese ($17,195) and morbidly obese ($17,655) patients. Overall operative and anaesthesia costs were higher in the morbidly obese group ($5688) than in normal ($5553), overweight ($5549) and obese ($5593) patients (P = 0.03). Operating room costs were higher in morbidly obese patients ($3418) than in normal ($3276), overweight ($3291) and obese ($3340) patients (P < 0.001). Post-operative costs were no different (P = 0.30). Blood bank costs differed (P = 0.002) and were lower in the morbidly obese group ($180) compared with the other patient groups (P < 0.05). Other differences in costs were not significant. Morbidly obese patients were more likely to be transferred to a nursing home (24.1 %) than normal (18.4 %), overweight (17.9 %) or obese (16.0 %) patients (P = 0.001 each). There were no differences in the composite endpoint of 30 d mortality, re-admissions, re-operations or intensive care unit utilization. BMI in patients undergoing primary elective THA did not impact LOS or overall institutional acute care costs, despite higher operative costs in morbidly obese patients. Obesity does not increase resource utilization for elective THA.

Hot isostatic pressing (HIP) of α-Al2O3 submicron ceramics pressureless sintered at different temperatures: Improvement in mechanical properties for use in total hip arthroplasty (THA)

Abstract The effect of hot isostatic pressing (HIPing) on as-sintered α-Al2O3 ceramics for total hip arthroplasty (THA) was investigated. The sinterability of these powders and the minimum temperature required to obtain closed porosity have been determined by pressureless sintering in air at temperatures between 1280 and 1460 °C for 2 h. Temperatures of 1300 and 1325 °C and applied pressures of 150 MPa for 30 min were utilised in the HIP cycles. Densities >98% of the theoretical density (TD) have been obtained after HIPing, and the grain sizes previously obtained during pressureless sintering increased slightly during the HIP treatment. The microstructures before and after HIP treatments were observed by means of scanning electron microscopy (SEM). The fracture toughness was obtained by the indentation fracture technique using a Vickers hardness tester at a load of 10 N with a dwell time of 15 s for all cases. The ceramics obtained at the lowest HIP temperature (1300 °C) presented a grain size of 0.62 ± 0.04 μm, hardness of 20.5 ± 0.6 GPa, and fracture toughness of 4.8 ± 0.3 MPa m1/2. The reported values were higher than those obtained by other authors and were in concordance with international standards that could make these ceramics available as a replacement for metal-on-polyethylene in orthopaedic surgery.

Wear Rate of Highly Cross-Linked Polyethylene in Total Hip Arthroplasty

Highly cross-linked polyethylene was introduced for clinical use in total hip arthroplasty with the expectation that it would exhibit less wear when compared with conventional polyethylene. The purpose of this study was to report the clinical and radiographic results, after a minimum of five years of follow-up, of a randomized, blinded, controlled trial comparing a conventional polyethylene with a first-generation highly cross-linked polyethylene. One hundred patients were enrolled in a prospective, randomized controlled study comparing highly cross-linked and conventional polyethylene acetabular liners in total hip arthroplasty. Fifty patients were in each group. At the time of follow-up, clinical outcomes were assessed and steady-state femoral head penetration rates (after bedding-in) for each patient were calculated with use of a validated radiographic technique. In addition, a statistical comparison of polyethylene wear between groups was performed with use of generalized estimating equations. At a mean of 6.8 years postoperatively, there were no differences between the two polyethylene groups with regard to the Harris hip score, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), or Short Form-12 (SF-12) score. The mean femoral head penetration rate in the first through fifth years was found to be significantly lower in the group treated with the highly cross-linked polyethylene (0.003 mm/yr [95% confidence interval, +/-0.027]) than it was in the group treated with conventional polyethylene (0.051 mm/yr [95% confidence interval, +/-0.022]) (p=0.006). Men treated with a conventional polyethylene liner had a significantly higher (p<or=0.012) femoral head penetration rate (0.081 mm/yr [95% confidence interval, +/-0.065]) than both men and women with a highly cross-linked liner (-0.013 mm/yr [95% confidence interval, +/-0.074] and 0.009 mm/yr [95% confidence interval, +/-0.028], respectively). The general estimating equations demonstrated that the group with a highly cross-linked polyethylene liner had a significantly lower femoral head penetration rate than the group with a conventional polyethylene liner (p=0.025), and a significantly higher femoral head penetration rate was demonstrated in men with a conventional polyethylene liner when compared with both men and women with a highly cross-linked liner (p=0.003). At a minimum of five years postoperatively, the steady-state femoral head penetration rate associated with this first-generation highly cross-linked polyethylene liner was significantly lower than that associated with a conventional polyethylene liner. Long-term follow-up is required to demonstrate the clinical benefit of this new material.

Failure of Metal-on-Metal Total Hip Arthroplasty Mimicking Hip Infection

New-generation metal-on-metal bearings made from cobalt-chromium alloys for use in total hip arthroplasty are now being utilized worldwide. A hypersensitivity reaction to a metal-on-metal bearing is a rare but reported complication and is thought to be a novel mode of failure of these implants1,2. These reactions were initially observed in patients with first-generation bearings and are now being reported in association with the second-generation metal-on-metal bearings currently in use3-5. Characteristic histological changes in the periprosthetic tissues obtained during revision surgical procedures in these patients have suggested the development of an immunological response2,6. Reports have suggested that the possibility of such a reaction should be considered when a patient presents with persistent, or the early reappearance of, preoperative pain symptoms, including a marked joint effusion, and the development of early osteolysis or radiolucent lines in the absence of infection2,7. Fever and elevated serum levels of inflammatory markers have routinely been reported to not occur in these patients. We describe two patients with failure of metal-on-metal implants who presented with signs that mimicked a deep-seated hip infection. To our knowledge, this has not been reported previously. Although the two cases were similar in terms of the clinical presentation, each ultimately represented a different pathological condition and etiology. The patients were informed that data concerning the case would be submitted for publication, and they consented. Case 1. A fifty-three-year-old man presented to our emergency department because of bilateral hip pain and episodes of low-grade fever three years after a bilateral metal-on-metal total hip arthroplasty. A Pinnacle acetabular component with a cobalt-chromium metal bearing surface (DePuy Orthopaedics, Warsaw, Indiana) had been implanted bilaterally. The pain had been present since the surgery, and the patient had never stopped …

Total Hip Arthroplasty for Displaced Fracture of the Femoral Neck using Size 32 mm Femoral Head and Soft Tissue Repair after a Posterior Approach

The optimal operative treatment of displaced sub capital femoral fractures in the elderly is controversial. Recently, randomised controlled trials have suggested a better outcome with the use of total hip arthroplasty (THA) to treat displaced intra capsular fractures of the femur for elderly patients in good health. However, overall there is limited evidence to support the choice between different types of arthroplasty. Dislocation remains a concern with THA, especially when a posterior approach is used. We analysed the outcome of twenty primary cementless THA using a posterior approach with soft tissue repair and a size 32 mm head in active elderly patients presenting with displaced intra capsular femoral neck fractures. We also compared the results with the outcome in a cohort of matched patients who underwent primary THA for osteoarthritis. Satisfactory results were noted in terms of pain control, return to pre-morbid activity and radiological evidence of bone implant osseointegration. The functional outcome in the fracture group was similar to the osteoarthritis group. In conclusion, with optimal patient selection THA seems to provide a good functional outcome and pain control in the management of displaced intracapsular femoral neck fractures. Use of 32 mm head and posterior capsule repair may reduce the high risk of dislocation noted with the posterior approach.