Mid-term progressive loosening of hydroxyapatite-coated femoral stems paired with a metal-on-metal bearing.

BACKGROUND: Several hydroxyapatite (HA)-coated femoral stems from a single manufacturer were identified to have aseptically loosened at mid-term follow-up despite prior radiographic appearance of osseointegration. Possible causes and associated risk factors for stem loosening were explored through radiographic review and implant retrieval analysis. METHODS: Forty-six retrieved hip stems (Corail, DePuy-Synthes) were identified and grouped by bearing type: metal-on-metal (MoM), metal-on-polyethylene, and ceramic-on-ceramic. Stem lucency was graded on post-operative radiographs up to the time of revision. Stems were examined for stripping of the HA coating, taper corrosion, and bearing wear in metal-on-metal cases. Patient demographics, implant design features, and perioperative data were collected from electronic databases and patient charts. RESULTS: Aseptic loosening occurred in 37% of cases examined. MoM bearings were associated with 7.25 times greater risk of loosening compared to other bearing types. Stem radiolucency was more prevalent for MoM cases and, although not statistically significant, demonstrated progressive lucency. Taper corrosion appeared more severe for MoM cases and correlated with proximal stem radiolucency. Removal of the HA coating from the stems was associated with both taper corrosion and MoM bearing wear. Length of implantation was a confounding factor for the MoM cases. CONCLUSION: This study has demonstrated a high risk of mid-term loosening of previously osseointegrated HA-coated femoral stems when paired with a MoM bearing. The mechanism of loosening appears progressive in nature and related to the MoM bearing, possibly interacting with the HA coating. If such loosening is recognized early, rapid revision may allow for retention of the femoral stem.

Low Revision Rates at 10 years for Metal on Metal Hip Implants in a Military Population.

INTRODUCTION: Prior to being largely abandoned due to unacceptably high failure rates and the adverse physiologic reactions to metal ions, metal-on-metal (MoM) total hip arthroplasty (THA) and hip resurfacing (HR) were in widespread use throughout the USA, and the potential benefit of decreased volumetric wear rates made it of particular interest to those who serve a young active population, such as military surgeons. The aim of our study was to determine the revision rate of metal on metal hip implants performed at our military institution and obtain current patient reported outcomes from this cohort. MATERIALS AND METHODS: We conducted a retrospective review of patients who underwent MoM total hip arthroplasty (THA) or hip resurfacing (HR) at our institution from 2006 to 2012. Revision status and component type were determined, and patients were contacted to obtain current HOOS JR scores. RESULTS: We identified 103 THAs in 88 patients and 38 HRs in 33 patients, with mean follow up of 10.2 years. Average age at time of surgery was 48 years, and 85% of the patients were male. The mean HOOS JR score in the THA and HR groups were 84.9 ± 17.6 and 75.8 ± 24.9, respectively (p = 0.38), and were not significantly lower in those who were revised. Two THA revisions occurred for metallosis and one for aseptic loosening of the femoral component. One HR revision occurred for breach of the anterior femoral neck, and one occurred for heterotopicossification. CONCLUSIONS: Revision rates of MoM THA and HR in this young, predominantly male population were 2.9% and 5.3%, respectively, and patients maintained generally good hip-specific outcomes.

Are all metal-on-metal hip revision operations contributing to the National Joint Registry implant survival curves? : a study comparing the London Implant Retrieval Centre and National Joint Registry datasets.

AIMS: The National Joint Registry for England, Wales and Northern Ireland (NJR) has extended its scope to report on hospital, surgeon and implant performance. Data linkage of the NJR to the London Implant Retrieval Centre (LIRC) has previously evaluated data quality for hip primary procedures, but did not assess revision records. METHODS: We analysed metal-on-metal hip revision procedures performed between 2003 and 2013. A total of 69 929 revision procedures from the NJR and 929 revised pairs of components from the LIRC were included. RESULTS: We were able to link 716 (77.1%) revision procedures on the NJR to the LIRC. This meant that 213 (22.9%) revision procedures at the LIRC could not be identified on the NJR. We found that 349 (37.6%) explants at the LIRC completed the full linkage process to both NJR primary and revision databases. Data completion was excellent (> 99.9%) for revision procedures reported to the NJR. DISCUSSION: This study has shown that only approximately one third of retrieved components at the LIRC, contributed to survival curves on the NJR. We recommend prospective registry-retrieval linkage as a tool to feedback missing and erroneous data to the NJR and improve data quality. TAKE HOME MESSAGE: Prospective Registry - retrieval linkage is a simple tool to evaluate and improve data quality on the NJR.

Total knee arthroplasty with an oxidised zirconium femoral component: ten-year survivorship analysis.

AIMS: Oxidised zirconium was introduced as a material for femoral components in total knee arthroplasty (TKA) as an attempt to reduce polyethylene wear. However, the long-term survival of this component is not known. METHODS: We performed a retrospective review of a prospectively collected database to assess the ten year survival and clinical and radiological outcomes of an oxidised zirconium total knee arthroplasty with the Genesis II prosthesis. The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Knee Injury and Osteoarthritis Outcome Score (KOOS) and a patient satisfaction scale were used to assess outcome. RESULTS: A total of 303 consecutive TKAs were performed in 278 patients with a mean age of 68 years (45 to 89). The rate of survival ten years post-operatively as assessed using Kaplan-Meier analysis was 97% (95% confidence interval 94 to 99) with revision for any reason as the endpoint. There were no revisions for loosening, osteolysis or failure of the implant. There was a significant improvement in all components of the WOMAC score at final follow-up (p < 0.001). The mean individual components of the KOOS score for symptoms (82.4 points; 36 to 100), pain (87.5 points; 6 to 100), activities of daily life (84.9 points; 15 to 100) and quality of life (71.4 points; 6 to 100) were all at higher end of the scale. DISCUSSION: This study provides further supportive evidence that the oxidised zirconium TKA gives comparable rates of survival with other implants and excellent functional outcomes ten years post-operatively. TAKE HOME MESSAGE: Total knee arthroplasty with an oxidised zirconium femoral component gives comparable long-term rates of survival and functional outcomes with conventional implants.

Detailed inspection of metal implants.

Detailed visual inspection of metal hips is the first step in retrieval analysis. In this study a systematic visual inspection protocol was developed to quantify bearing surface changes and their associations with material loss was investigated. Simple and multiple linear regression models found that moderate surface scratching, discolouration, haziness and the size of visible wear scars were all significantly associated with material loss (R2 = 5%-73%, p<0.05). Visual inspection is not a substitute for measurement of material loss but an understanding of bearing surface changes may offer unique clues as to the mechanisms of failure of retrieved hips.

All-polyethylene tibial components are not inferior to metal-backed tibial components in long-term follow-up of knee arthroplasties.

BACKGROUND: All-polyethylene tibias (APT) are under-utilized in most of the Western countries, due to a shift from the original all-polyethylene design to metal-backed tibia (MBT) components. Only few total knee prostheses allow direct comparison between APT and MBT components, due to different geometric designs in many systems. The Depuy PFC Sigma prostheses have a similar geometric design in both the MBT and the APT, and with the same corresponding femoral component, thus allowing an assessment and comparison between APT and MBT components. METHODS: This is a retrospective analysis of a consecutive series of osteoarthritic patients who underwent total knee arthroplasties with at least 10-year follow-up comparing a modern congruent APT component to a modular MBT component of the same design. RESULTS: Seventy-three patients (81 knees, mean age 73 years) were available for assessment. Among the cohort, three patients had revision surgery (one from the APT group). In total, 73 patients were available for follow-up (59 MBT prostheses and 22 APT prostheses). There were no differences in knee function (Knee Society score, range of motion, stability) or radiographic parameters between the groups. Of the three revisions due to tibial tray loosening, only one was performed in the APT group and two were performed in the MBT group; another revision in the MBT group was due to loosening of both components; none of the revisions were due to septic complications. Ten-year survivorship of both designs was 92 %. CONCLUSIONS: While function of both designs appears similar, the APT design shows a trend toward requiring fewer revisions and is more cost-effective.

Mechanical properties of a cemented porous implant interface.

BACKGROUND: Revision arthroplasty often requires anchoring of prostheses to poor-quality or deficient bone stock. Recently, newer porous materials have been introduced onto the market as additional, and perhaps better, treatment options for revision arthroplasty. To date, there is no information on how these porous metals interface with bone cement. This is of clinical importance, since these components may require cementing to other prosthesis components and occasionally to bone. METHODS: We created porous metal and bone cylinders of the same size and geometry and cemented them in a well-established standardized setting. These were then placed under tensile loading and torsional loading until failure was achieved. This permitted comparison of the porous metal/cement interface (group A) with the well-studied bone/cement interface (group B). RESULTS: The group A interface was statistically significantly stronger than the group B interface, despite having significantly reduced depth of cement penetration: it showed a larger maximum tensile force (effect size 2.7), superior maximum tensile strength (effect size 2.6), greater maximum torsional force (effect size 2.2), and higher rotational stiffness (effect size 1.5). INTERPRETATION: The newer porous implants showed good interface properties when cemented using medium-viscosity bone cement. The axial and rotational mechanical strength of a porous metal/cement interface appeared to be greater than the strength of the standard bone/cement interface. These results indicate that cementing of porous implants can provide great stability in situations where it is needed.