Hypersensitivity to metals in metal-on-metal hip arthroplasty: a prospective study of one hundred and thirty five lymphocyte transformation tests.

BACKGROUND: Metal allergy remains a controversial topic in the orthopaedic community. It is not known if or to what degree metal sensitivity contributes to inflammatory soft tissue failures, unexplained residual pain, or clinical complications after total joint replacement with metal prostheses. METHODS: We investigated the efficacy of the lymphocyte transformation test (LTT) in predicting adverse outcomes in patients after receiving a metal joint replacement. Our study cohort consists of 135 metal-on-metal hip resurfacing arthroplasty cases performed between 2013 and 2015. All study patients had an LTT preoperatively. We retrospectively analyzed clinical outcomes and failures for our cohort. RESULTS: There was no difference in LTT reactivity between men and women. Of the 135 patients tested, 46 (34.1% of cohort) tested positive to at least one of the materials comprising their implant, and 78 patients (57.8%) had at least one reactive score to any component of the LTT. After a minimum follow-up of two years, we did not observe an allergic response to the implant in any patients. There were no failures requiring revision. We observed a 2.2% rate of moderate residual pain; no patients with residual pain tested positive for metal sensitivity. When patients with moderate-high LTT reactivity (30.4% of cohort) were compared to the remainder of the study group, there was no difference in HHS or UCLA activity score. There was no correlation between blood metal ion levels and LTT reactivity. CONCLUSION: We were unable to prove any predictive value of the LTT. We failed to identify hypersensitivity to metals in patients with metal-on-metal hip resurfacing arthroplasty.

Long-term clinical outcomes of the Biomet M2a-38: a retrospective review of 335 total hip arthroplasty cases.

BACKGROUND: At the turn of the century, over one-third of total hip arthroplasties comprised metal-on-metal bearings. As this patient population and their implants age, it is crucial to understand associated late failure modes and expected long-term functional outcomes. We report the long-term results of a large metal-on-metal uncemented total hip arthroplasty system with unique design characteristics compared to others that have been reported with high failure rates. METHODS: We retrospectively analyze our prospective clinical database to determine overall implant survivorship and functional outcomes. Further, we compare these results to the clinical outcomes reported in orthopedic registries and in other published studies with similar metal-on-metal total hip arthroplasty cohorts. RESULTS: Implant survivorship at 10 years was 99.1% and continued to 97.6% survivorship at 20 years. Implant survivorship at 20 years did not vary significantly between sexes (Male: 98.3%, Female: 97.2%; log-rank p-value = 0.46). Mean whole blood cobalt levels were 2.6 µg/L in unilateral cases, 5.3 µg/L in bilateral patients, and 3.4 µg/L for the combined cohort. Average blood chromium levels were 1.4 µg/L in unilateral patients, 2.9 µg/L in bilateral patients, and 1.8 µg/L for group combined. We observed a 0.9% rate of failure due trunnion corrosion at a mean of 13.1 years postoperatively (10.6-15.6 years) but had no bearing wear failures. CONCLUSIONS: Our 20-year implant survivorship of 97.6% with the M2a-38 bearing surpassed registry benchmarks for THA. This large-bearing (38 mm), full hemisphere coverage metal-on-metal system had no bearing wear failures, one failure of instability, one failure of fixation, and three trunnion failures, perhaps suggesting an optimum balance between stability of the joint and the trunnion.

Antibiotic Delivery via Hickman Catheter for the Treatment of Prosthetic Joint Infection.

Infection rates for total joint arthroplasty range from 1% to 2%, and infection carries significant risk. The traditional course of treatment is irrigation and debridement, but historically, success rates have been variable. The goals of this study were to evaluate the safety and efficacy of Hickman catheterization in the treatment of prosthetic joint infection and to assess its value as an alternative to irrigation and debridement. The authors retrospectively analyzed 26 Hickman catheterizations in the treatment of acute early, acute late, and chronic late infections of primary and revision hip and knee arthroplasty. Initial arthroplasty procedures were performed between 2006 and 2018, with all cases followed for a minimum of 1 year postoperatively. The authors evaluated surgical data, clinical outcomes, and success rates, and they compared their success rates with reported values for cases treated with irrigation and debridement. The authors' success rate was 100% for acute early hip infection, 100% for chronic knee infection, and 80.0% for chronic hip infection. They reported a 75.0% success rate in the treatment of acute late infection for hip arthroplasty and a rate of 62.5% for knee arthroplasty. Postoperative clinical outcomes were significantly improved for both hips and knees for all infection types. The success rates for the treatment of acute early prosthetic joint infection and chronic late prosthetic knee infection were superior to available reported rates on irrigation and debridement. The authors also reported the highest success rate for the treatment of acute late infection. The current data suggest that Hickman catheterization is a promising safe and effective alternative to irrigation and debridement for the treatment of prosthetic joint infection. [Orthopedics. 2021;44(3):e395-e401.].

Hip resurfacing arthroplasty for end-stage arthritis caused by childhood hip disease.

INTRODUCTION: Patients with hip arthritis due to Legg-Calvé-Perthes (LCP) and slipped capital femoral epiphysis (SCFE) pose altered femoral anatomy, making hip resurfacing arthroplasty (HRA) technically complicated. We examined implant survival and clinical symptoms in patients with a history of LCP or SCPE who underwent HRA for end-stage osteoarthritis. METHODS: Data was collected for patients who underwent HRA for osteoarthritis due to LCP (n = 59) or SCFE (n = 32). Harris Hip Scores (HHS), UCLA activity scores, and radiographs were evaluated pre and postoperatively. Wilcoxon Signed-Rank Tests and Kaplan-Meier Survivorship curves were used to analyse data. RESULTS: Survivorship for freedom from revision or clinical failure was 93.55(95% CI, 78.47-98.18) at 5.79 years, up until the most recent follow-up of 11.23 years. There were 3 failures: 1 LCP due to instability at 2.4 years, 1 SCFE due to femoral neck fracture at 1 month, and another SCFE due to unexplained pain at 5.8 years. Five patients, 1 LCP and 4 SCFE, had retained hardware prior to surgery; 4 had their hardware removed during surgery. Postoperatively HHS and UCLA activity scores increased (p < 0.0001, for both measures). Leg-length discrepancy improved preoperatively from 7.9 (0.0-32) mm to 0.65 (0.0-10) mm postoperatively (p < 0.0001). Follow-up radiographs of all non-failure HRA patients revealed implants to be in good alignment with no indication of loosening. CONCLUSION: Although HRA in SCFE and LCP patients increases technical difficulties, findings demonstrate excellent implant survival, no intraoperative complications, and improvements in leg-length discrepancies and clinical functional outcomes.

Optimizing Acetabular Component Bone Ingrowth: The Wedge-Fit Bone Preparation Method.

We investigate the efficacy of a modified acetabular bone-preparation technique in reducing the incidence of two clinical problems identified in hip resurfacing arthroplasty. The first issue is failure due to lack of bone ingrowth into the acetabular component. The second is a newly recognized phenomenon of early cup shift. We hypothesize that these issues might be resolved by using a "wedge-fit method", in which the component wedges into the peripheral acetabular bone rather than bottoming out and potentially toggling on the apex of the cup. Prior to November 2011, all acetabula were reamed 1 mm under and prepared with a press-fit of the porous coated acetabular component. After November 2011, we adjusted reaming by bone density. In "soft bone" (T-score <-1.0), we underreamed acetabula by 1 mm less than the outer diameter of the cup, as was previously done in all cases. For T-scores greater than -1.0, we reamed line-to-line. Additionally, we began performing an "apex relief" starting June 2012 in all cases by removing 2 mm of apex bone with a small reamer after using the largest reamer. Failure of acetabular ingrowth occurred in 0.5% of cases before the wedge-fit method and <0.1% after. Rate of cup shift was reduced from 1.1% to 0.4%. The rate of unexplained pain between 2 and 4 years postoperatively also declined significantly from 2.6% to 1.3%. Our evidence suggests that wedge-fit acetabular preparation improves initial implant stability, leading to fewer cases of early cup shift, unexplained pain, and acetabular ingrowth failure.

Femoral Fixation Methods in Hip Resurfacing Arthroplasty: An 11-Year Retrospective Comparison of 4013 Cases.

BACKGROUND: The optimal femoral fixation method remains unclear. To evaluate the role of femoral fixation techniques in hip resurfacing, we present a comparison of 2 consecutive groups: group 1 (739 hips) with cemented femoral components; group 2 (3274 hips) with uncemented femoral components. METHODS: We retrospectively analyzed our clinical database to compare failures, reoperations, complications, clinical results, and radiographic measurements. Groups were consecutive, so cemented cases had longer follow-up. However, all patients from both groups were at least 2 years out from surgery. Two-year clinical and radiographic data were compared. Longer-term comparison data as well as Kaplan-Meier implant survivorship curves specifically focusing on femoral failure modes were analyzed. RESULTS: Kaplan-Meier 10-year implant survivorship using nontraumatic femoral failure as an end point was 98.9% for the cemented and 100% for the uncemented femoral component. The uncemented, group 2 cases showed a significantly lower raw failure rate (1.1% vs 4.6%), 2-year failure rate (0.8% vs 2.8%), 2-year femoral failure rate (0.4% vs 0.9%), and a lower combined rate of femoral complications and failures (0.6% vs 1.8%). In cases that did not fail, patient mean clinical scores, pain scores, and combined range of motion were all significantly better for group 2. CONCLUSION: We have demonstrated that in the fully porous-coated ReCap device, uncemented femoral fixation is superior to cemented fixation at 11 years follow-up (0.0% vs 1.1% late femoral loosening) in this single-surgeon cohort. Early femoral fractures also reduced from 0.8% to 0.3%, but this may be partially or completely due to a new bone density management program. This study demonstrates better femoral implant survivorship for the uncemented device compared to the cemented femoral resurfacing component for this implant design.

Acetabular Debonding: An Investigation of Porous Coating Delamination in Hip Resurfacing Arthroplasty.

BACKGROUND: To date, there have been no published investigations on the cause of acetabular debonding, a rare failure phenomenon in metal-on-metal hip resurfacing where the acetabular porous coating delaminates from the implant while remaining well fixed to the pelvic bone. PURPOSES: This study aims to summarize the current understanding of acetabular debonding and to investigate the discrepancy in rate of debonding between two implant systems. PATIENTS AND METHODS: To elucidate potential causes of debonding, we retrospectively analyzed a single-surgeon cohort of 839 hip resurfacing cases. Specifically, we compared rate of debonding and manufacturing processes between two implant systems. RESULTS: Group 1 experienced significantly more cases of debonding than Group 2 cases (4.0% versus 0.0%, p value<0.0001). Implant manufacturing processes differed in surface coating, heat treatment, postmanufacturing treatment, and apex thickness. Debonded implants were more likely to have missed RAIL guidelines (p=0.04). CONCLUSIONS: We identified implant system, postoperative time, and acetabular component placement as variables contributing to rate of debonding. We recommend minimizing acetabular inclination angle according to RAIL guidelines. Further, we evaluated manufacturing differences between the two implant systems but did not have access to proprietary data to identify the cause of debonding. Both implants met ASTM standards, yet only the Group 1 implant debonded. This suggests the second implant had greater fatigue shear strength. Because the Group 2 implant achieved a more durable interface that did not debond, we suggest the ASTM F1160 standard for fatigue shear strength be increased to that achieved by its manufacturer. LEVEL OF EVIDENCE II: A retrospective evaluation of prospectively collected data.

Interventions for Improving Hip Resurfacing Outcomes in Women: A High-Volume, Retrospective Study.

BACKGROUND: Women seeking surgical intervention for their hip disorders will often find total hip arthroplasty (THA) presented as their only option. THA, when compared with hip resurfacing arthroplasty, removes substantially more bone-stock, limits range-of-motion, exhibits increased dislocation risk, and presents greater overall 10-year mortality rate. Despite these risks, most surgeons continue to select against women for hip resurfacing because registries notoriously report inferior survivorship when compared with men and THA. METHODS: We investigated the reasons for why resurfacing arthroplasty devices survive poorly in women to develop interventions which might improve hip resurfacing outcomes in women. Using these findings, we developed a series of surgical interventions to treat the underlying issues. Herein, we compare 2 study groups: women who received hip resurfacings before (group 1) and after (group 2) these interventions. RESULTS: Eight-year implant survivorship substantially improved from 89.6% for group 1 to 97.7% for group 2. Adverse wear-related failure, femoral component loosening, and acetabular component loosening were all significantly reduced in group 2, which we attribute to the implementation of our relative acetabular inclination limit guidelines, use of uncemented femoral fixation, and selection of the Tri-Spike acetabular component for supplemental fixation, respectively. Kaplan-Meier implant survivorship curves, grouped into 2-year time intervals, show that the disparity in failure rates between men and women is diminishing. CONCLUSION: When experienced surgeons use refined and proper surgical technique, women show promise as excellent candidates for hip resurfacing as an alternative treatment for their debilitating hip conditions.

Metal-on-metal hip resurfacing in patients younger than 50 years: a retrospective analysis : 1285 cases, 12-year survivorship.

BACKGROUND: The Nordic registry reports patients under 50 years old with total hip replacements realize only 83% 10-year implant survivorship. These results do not meet the 95% 10-year survivorship guideline posed by the UK's National Institute for Health and Care Excellence (NICE) in 2014. METHODS: The purpose of this study is threefold: First, we evaluate if metal-on-metal hip resurfacing arthroplasty meets these high standards in younger patients. Next, we compare outcomes between age groups to determine if younger patients are at higher risk for revision or complication. Lastly, we assess how outcomes between sexes changed over time. From January 2001 to August 2013, a single surgeon performed 1285 metal-on-metal hip resurfacings in patients younger than 50 years old. We compared these to an older cohort matched by sex and BMI. RESULTS: Kaplan-Meier implant survivorship was 96.5% at 10 years and 96.3% at 12 years; this did not differ from implant survivorship for older patients. Implant survivorship at 12 years was 98 and 93% for younger men and women, respectively; survivorship for women improved from 93 to 97% by using exclusively Biomet implants. There were four (0.3%) adverse wear-related failures, with no instances of wear or problematic ion levels since 2009. Activity scores improved from 5.4 ± 2.3 preoperatively to 7.6 ± 1.9 postoperatively (p < 0.0001), with 43% of patients reporting a UCLA activity score of 9 or 10. CONCLUSIONS: Hip resurfacing exceeds the stricter 2014 NICE survivorship criteria independently in men and women even when performed on patients under 50 years old.

Comparison of Cemented and Bone Ingrowth Fixation Methods in Hip Resurfacing for Osteonecrosis.

BACKGROUND: The optimal surgical treatment for osteonecrosis of the femoral head has yet to be elucidated. To evaluate the role of femoral fixation techniques in hip resurfacing, we present a comparison of the results for 2 consecutive groups: group 1 (75 hips) received hybrid hip resurfacing implants with a cemented femoral component; group 2 (103 hips) received uncemented femoral components. Both groups received uncemented acetabular components. METHODS: We retrospectively analyzed our clinical database to compare failures, reoperations, complications, clinical results, metal ion test results, and X-ray measurements. Using consecutive groups caused time interval bias, so we required all group 2 patients to be at least 2 years out from surgery; we compared results from 2 years and final follow-up. RESULTS: Patient groups matched similarly in age, body mass index, and percent female. Despite similar demographics, the uncemented, group 2 cases showed a lower raw failure rate (0% vs 16%; P < .0001), a lower 2-year failure rate (0% vs 7%; P = .04), and a superior 8-year implant survivorship (100% vs 91%; log-rank P = .0028; Wilcoxon P = .0026). In cases that did not fail, patient clinical (P = .05), activity (P = .02), and pain scores (P = .03), as well as acetabular component position (P < .0001), all improved in group 2, suggesting advancements in surgical management. There were no cases of adverse wear-related failure in either group. CONCLUSION: This study demonstrates a superior outcome for cases of osteonecrosis with uncemented hip resurfacings compared to cases employing hybrid devices.

Reducing the failure rate of hip resurfacing in dysplasia patients: a retrospective analysis of 363 cases.

BACKGROUND: Arthritis secondary to developmental hip dysplasia often mandates implant surgery at a relatively young age. Hip resurfacing arthroplasty (HRA), compared with standard stemmed total hip arthroplasty (THA), affords a more active lifestyle including extreme-motion activities but stimulates concerns pertaining to implant failure. METHODS: We addressed the primary modes of failure through a series of interventions, including a new guideline for achieving proper implant alignment through intraoperative x-rays. We then compared two sequential cohorts in a single-surgeon practice: patients with developmental dysplasia who underwent HRA before (Group 1; 121 hips in 105 patients) and after (Group 2; 242 hips in 210 patients) June 2008, at which time the four interventions were all in place. RESULTS: Implants in Group 2 failed less frequently within two years (0.8 % vs. 6.6 %, p = 0.002) and were more likely to have projected seven-year Kaplan-Meier survivorship (99 % vs. 89 %, p < 0.0001 by log-rank test). Patients in Group 2 were more likely to have normal metal ion levels (77 % vs. 56 %, p = 0.0008) and optimum metal ion levels (99 % vs. 86 %, p = 0.0008). Patients in Group 2 also benefited from a 19-min decrease in mean operation time, a 45 % decrease in mean estimated blood loss, and a 0.9-day decrease in mean hospital stay (p < 0.0001 in each instance). CONCLUSIONS: We believe the interventions reported here, combined with sufficient surgeon experience and properly designed implants, afford patients with mild developmental dysplasia a more active lifestyle with favorable implant survival.

Outcomes after revision of metal-on-metal hip resurfacing arthroplasty.

We report the results of 58 hip resurfacing arthroplasties (HRA) revised by a single surgeon with an average of 5.2±2.6 years follow-up. The four most common causes for revision were acetabular component loosening, femoral neck fracture, femoral component loosening, and adverse wear related failure (AWRF). In 95% of cases (55/58), the revision bearing was a large metal-on-metal type including all seven AWRF cases; three cases were revised to ceramic-on-polyethylene. There were two repeat revisions due to acetabular component loosening. Revision of AWRF had an excellent outcome using limited debridement and a stable large metal bearing placed in the correct position. The only problematic group was the one revised for acetabular loosening in which 2/16 (6%) required repeat revision for failure of acetabular fixation.

Current status of modern fully porous coated metal-on-metal hip resurfacing arthroplasty.

Between March 2007 and July 2010, 1000 consecutive fully porous coated hip resurfacing arthroplasties (HRA) were performed by a single surgeon in 871 patients. The average length of follow-up was 3 ± 1 years. Three cases (0.3%) in three patients showed adverse wear related failures. Another 17 (1.7%) failures were identified at the time of this study. Using any failure of any component as the endpoint, the survivorship rate was 98.8% at two years and 97.4% at five years. Excluding the failed cases, all components were radiographically stable; there was only one partial femoral radiolucency seen. The clinical and radiological outcomes of this fully porous coated hip resurfacing were comparable to, if not better than, those reported by others using hybrid fixation methods at five years post-operatively.

Incidence of adverse wear reactions in hip resurfacing arthroplasty: a single surgeon series of 2,600 cases.

A single surgeon performed 2,559 metal-on-metal hip resurfacing arthroplasties in 2,109 patients. The Corin Cormet 2000 (393 cases) and Biomet Recap implants (2,166 cases) were used in our series. In this study, the adverse wear failure (AWF) rate was 0.27%. At 10 years postoperatively, our Kaplan-Meier cumulative revision rate for AWF was 1% for all patients, 0.2% for men, 2.6% for women, and 9% for patients with a diagnosis of dysplasia. All AWF failures had component sizes ≤48 mm. All had metal ion levels above 15 ug/ml. All had acetabular inclination angles (AIA) ≥50° on standing pelvis radiographs. All had severe metallosis found at the time of revision. Six of the seven AWF cases were in women. There were no failures from pseudotumours without AWF (metallosis) in this series.

A safe zone for acetabular component position in metal-on-metal hip resurfacing arthroplasty: winner of the 2012 HAP PAUL award.

A safe zone for acetabular component positioning in hip resurfacing (RAIL: Relative Acetabular Inclination Limit) was calculated based on implant size and acetabular inclination angle (AIA). For AIA below the RAIL, there were no adverse wear failures or dislocations, and only 1% of cases with ion levels above 10 µg/L. Other than high inclination angle and small bearing size, female gender was the only other factor that correlated with high ion levels in the multivariate analysis. Seven hundred sixty-one hip resurfacing cases are included in this study. The UCLA activity score, femoral shaft angle, body mass index, weight, American Society of Anesthesiologists score, combined range of motion, diagnosis, age, gender, implant brand, AIA, bearing size, and duration of implantation were analyzed to determine the potential risk factors for elevated metal ion levels. These findings apply to sub hemispheric metal-on-metal bearings with similar coverage arcs as the Biomet and Corin hip resurfacing brands. Additional problems may occur when these bearings are connected with trunions on stems for total hip arthroplasty.

Feasibility of proactive medical device surveillance: the VA Clinical Assessment Reporting and Tracking (CART) program.

BACKGROUND: Timely identification and reporting of medical device problems is critical to postmarket device surveillance programs to maximize patient safety. Cardiac catheterization laboratories are high-device utilization areas well suited for device surveillance. OBJECTIVE: To demonstrate the feasibility of the national VA Clinical Assessment, Reporting, and Tracking (CART) system, embedded in the electronic health record of all 76 VA cardiac catheterization laboratories, to document unexpected problems with medical devices at the point of care. METHODS: We evaluated 260,258 consecutive cardiac catheterization and/or percutaneous coronary intervention procedures on 175,098 Veterans between August 2006 and February 2012. Unexpected device problems (UDPs) encountered for any equipment used during a procedure were entered by clinicians at the point of care as part of regular care documentation. All UDPs were reviewed in collaboration with the FDA to ascertain the likelihood of a device defect (eg, in manufacture or design) and/or contributing to a procedural complication (level I, unlikely; level II, possibly; level III, likely). RESULTS: Of the 260,258 procedure reports, 974 (0.37%) UDP's were reported by 71 (92.2%) of the 76 VA hospitals. After triage, 739 (75.9%) were deemed level I, 196 (20.1%) level II, and 39 (4.0%) level III. Of the 39 level III reports, 12 (30.7%) are in the submission phase as a FDA MedWatch report. The number of monthly UDP reports increased significantly from 2006 to 2012 (P<0.001). CONCLUSIONS: Leveraging a clinical application embedded in the electronic health record and in collaboration with FDA, a proactive national cardiac device surveillance program has been successfully implemented in the VA.

Sex and risk of hip implant failure: assessing total hip arthroplasty outcomes in the United States.

IMPORTANCE: The role of sex in relationship to implant failure after total hip arthroplasty (THA) is important for patient management and device innovation. OBJECTIVE: To evaluate the association of sex with short-term risk of THA revision after adjusting for patient, implant, surgery, surgeon, and hospital confounders. DESIGN AND SETTING: A prospective cohort of patients enrolled in a total joint replacement registry from April 1, 2001, through December 31, 2010. PARTICIPANTS: Patients undergoing primary, elective, unilateral THA. MAIN OUTCOME MEASURES: Failure of THA, defined as revision procedure for (1) any reason, (2) septic reason, or (3) aseptic reason after the index procedure. RESULTS: A total of 35,140 THAs with 3.0 years of median follow-up were identified. Women constituted 57.5% of the study sample, and the mean (SD) patient age was 65.7 (11.6) years. A higher proportion of women received 28-mm femoral heads (28.2% vs 13.1%) and had metal on highly cross-linked polyethylene-bearing surfaces (60.6% vs 53.7%) than men. Men had a higher proportion of 36-mm or larger heads (55.4% vs 32.8%) and metal on metal-bearing surfaces (19.4% vs 9.6%). At 5-year follow-up, implant survival was 97.4% (95% CI, 97.2%-97.6%). Device survival for men (97.7%; 95% CI, 97.4%-98.0%) vs women (97.1%; 95% CI, 96.8%-97.4%) was significantly different (P = .01). After adjustments, the hazards ratios for women were 1.29 (95% CI, 1.11-1.51) for all-cause revision, 1.32 (95% CI, 1.10-1.58) for aseptic revision, and 1.17 (95% CI, 0.81-1.68) for septic revision. CONCLUSIONS: After considering patient-, surgery-, surgeon-, volume-, and implant-specific risk factors, women had a 29% higher risk of implant failure than men after THA in this community-based sample.

Total knee arthroplasty with fully porous-coated stems for the treatment of large bone defects.

Between February1999 and April 2006, 25 patients (28 knees) underwent a TKA by a single surgeon. At an average final follow-up of 7±2years (range, 3-10years), 34 (100%) of 34 fully porous stems had achieved bone ingrowth. However, one case (3%) had a component loosening due to the de-bonding of sheets of beads from the stem. The remaining cases remained well fixed. Three well-fixed stems in 2 patients failed from deep infection. There was one reoperation required for a femoral periprosthetic fracture. Our 10-year experience shows that fully porous-coated stems reliably achieve durable fixation in complex primary and revision TKA allowing the surgeon to bypass large bone defects and gain fixation in diaphyseal bone.

Risk of revision for fixed versus mobile-bearing primary total knee replacements.

BACKGROUND: Mobile-bearing total knee arthroplasty prostheses were developed to reduce wear and revision rates; however, these benefits remain unproven. The purposes of this study were to compare the short-term survivorship and to determine risk factors for revision of mobile-bearing and fixed-bearing total knee replacements. METHODS: A prospective cohort study of primary total knee arthroplasties performed from 2001 to 2009 was conducted with use of a community total joint replacement registry. Patient characteristics and procedure details were identified. Cox regression models were used. Bearing type was investigated as a risk factor for revision while adjusted for other risk factors such as age, American Society of Anesthesiologists (ASA) score, body mass index, sex, race, diagnosis, bilateral procedures, cruciate-retaining versus posterior-stabilized components, surgical approach, fixation, patellar resurfacing, hospital and surgeon volumes, and fellowship training. RESULTS: The study cohort consisted of 47,339 total knee arthroplasties, with 62.6% of the procedures in women. Fixed bearings were used in 41,908 knees (88.5%) and mobile bearings in 4830 (10.2%). Rotating-platform designs were used in all mobile-bearing total knee arthroplasties (3112 had a Rotating-Platform Press-Fit Condylar posterior-stabilized design; 1053, a Low Contact Stress [LCS] design; and 665, a Rotating-Platform Press-Fit Condylar cruciate-retaining design). Patients who received fixed-bearing total knee arthroplasty systems were older (mean age, 68.1 years) than those who received mobile-bearing total knee arthroplasty systems (mean age, 62.2 years); the difference was significant (p < 0.001). Overall, 515 knees (1.1%) were revised for reasons other than infection. The survival rate was 97.8% (95% confidence interval [CI], 97.4% to 98.0%) at 6.7 years. The adjusted risk of aseptic revision for the LCS total knee replacements was 2.01 times (95% CI, 1.41 to 2.86) higher than that for fixed-bearing total knee replacements (p < 0.001).There was no significant revision risk for the other mobile-bearing total knee arthroplasty systems. There was no association with surgeon and hospital case volumes and the risk of revision total knee arthroplasty. CONCLUSIONS: Our study suggests the benefit of potential long-term wear reduction with the LCS implant may not be realized in a community-based setting, where a variety of surgical skills, surgical experience, and diverse patient demographic factors may affect early outcomes. LEVEL OF EVIDENCE: Therapeutic Level II.