Unicompartmental Knee Arthroplasty in Octogenarians versus Younger Patients: A Comparison of 30-Day Outcomes.

As the United States' octogenarian population (persons 80-89 years of age) continues to grow, understanding the risk profile of surgical procedures in elderly patients becomes increasingly important. The purpose of this study was to compare 30-day outcomes following unicompartmental knee arthroplasty (UKA) in octogenarians with those in younger patients. The American College of Surgeons National Surgical Quality Improvement Program database was queried. All patients, aged 60 to 89 years, who underwent UKA from 2005 to 2016 were included. Patients were stratified by age: 60 to 69 (Group 1), 70 to 79 (Group 2), and 80 to 89 years (Group 3). Multivariate regression models were estimated for the outcomes of hospital length of stay (LOS), nonhome discharge, morbidity, reoperation, and readmission within 30 days following UKA. A total of 5,352 patients met inclusion criteria. Group 1 status was associated with a 0.41-day shorter average adjusted LOS (99.5% confidence interval [CI]: 0.67-0.16 days shorter, p < 0.001) relative to Group 3. Group 2 status was not associated with a significantly shorter LOS compared with Group 3. Both Group 1 (odds ratio [OR] = 0.15, 99.5% CI: 0.10-0.23) and Group 2 (OR = 0.33, 99.5% CI: 0.22-0.49) demonstrated significantly lower adjusted odds of nonhome discharge following UKA compared with Group 3. There was no significant difference in adjusted odds of 30-day morbidity, readmission, or reoperation when comparing Group 3 patients with Group 1 or Group 2. While differences in LOS and nonhome discharge were seen, octogenarian status was not associated with increased adjusted odds of 30-day morbidity, readmission, or reoperation. Factors other than age may better predict postoperative complications following UKA.

Quantum de-trapping and transport of heavy defects in tungsten.

The diffusion of defects in crystalline materials1 controls macroscopic behaviour of a wide range of processes, including alloying, precipitation, phase transformation and creep2. In real materials, intrinsic defects are unavoidably bound to static trapping centres such as impurity atoms, meaning that their diffusion is dominated by de-trapping processes. It is generally believed that de-trapping occurs only by thermal activation. Here, we report the direct observation of the quantum de-trapping of defects below around one-third of the Debye temperature. We successfully monitored the de-trapping and migration of self-interstitial atom clusters, strongly trapped by impurity atoms in tungsten, by triggering de-trapping out of equilibrium at cryogenic temperatures, using high-energy electron irradiation and in situ transmission electron microscopy. The quantum-assisted de-trapping leads to low-temperature diffusion rates orders of magnitude higher than a naive classical estimate suggests. Our analysis shows that this phenomenon is generic to any crystalline material.

Are Readmissions After Total Knee Arthroplasty Preventable?

Readmission within 90 days following total joint arthroplasty has become a central quality measure of reimbursement initiatives; however, the validity of readmission rates as a measure of hospital care quality and the proportion of readmissions that are preventable are unknown. The purpose of this study is to determine if readmissions within 30 and 90 days after total knee arthroplasty (TKA) were related to orthopaedic or medical etiology and identify if these readmissions were preventable. We retrospectively reviewed 1,625 elective TKAs performed between 2011 and 2014 at our institution. Readmissions within 30 and 90 days were categorized into orthopaedic and medical etiologies and an expert research panel determined if readmissions were potentially preventable based on objective criteria from national or peer-reviewed consensus guidelines. Out of the 1,625 TKAs performed during the study period, there were a total of 79 (4.8%) readmissions within 90 days of surgery, of which 17 (22%) were of orthopaedic etiology and 62 (78%) were of medical etiology. Fifty-two (66%) of the 79 readmissions occurred within 30 days, with 11 (21%) of orthopaedic and 41 (80%) of medical etiology. Only 2 of 79 (3%) readmissions within 90 days were deemed potentially preventable, and neither of them were orthopaedic in nature. Hospital readmissions after total joint arthroplasty are inevitable; however, only a small percentage (3%) of readmissions to our health care system was potentially preventable. Orthopaedic readmissions constituted a minority of the proportion of readmissions at 30 or 90 days, and none were deemed preventable.

Trajectory Taken by Dimeric Cu/Zn Superoxide Dismutase through the Protein Unfolding and Dissociation Landscape Is Modulated by Salt Bridge Formation.

Native mass spectrometry (MS) is a powerful means for studying macromolecular protein assemblies, including accessing activated states. However, much remains to be understood about what governs which regions of the protein (un)folding funnel, which can be explored by activation of protein ions in a vacuum. Here, we examine the trajectory that Cu/Zn superoxide dismutase (SOD1) dimers take over the unfolding and dissociation free energy landscape in a vacuum. We examined wild-type SOD1 and six disease-related point mutants by using tandem MS and ion-mobility MS as a function of collisional activation. For six of the seven SOD1 variants, increasing activation prompted dimers to transition through two unfolding events and dissociate symmetrically into monomers with (as near as possible) equal charges. The exception was G37R, which proceeded only through the first unfolding transition and displayed a much higher abundance of asymmetric products. Supported by the observation that ejected asymmetric G37R monomers were more compact than symmetric G37R ones, we localized this effect to the formation of a gas-phase salt bridge in the first activated conformation. To examine the data quantitatively, we applied Arrhenius-type analysis to estimate the barriers on the corresponding free energy landscape. This reveals a heightening of the barrier to unfolding in G37R by >5 kJ/mol-1 over the other variants, consistent with expectations for the strength of a salt bridge. Our work demonstrates weaknesses in the simple general framework for understanding protein complex dissociation in a vacuum and highlights the importance of individual residues, their local environment, and specific interactions in governing product formation.

Preoperative Hyponatremia Is Associated with Reoperation and Prolonged Length of Hospital Stay following Total Knee Arthroplasty.

Hyponatremia is a risk factor for adverse surgical outcomes, but limited information is available on the prognosis of hyponatremic patients who undergo total knee arthroplasty (TKA). The purpose of this investigation was to compare the incidence of major morbidity (MM), 30-day readmission, 30-day reoperation, and length of hospital stay (LOS) between normonatremic and hypontremic TKA patients.The American College of Surgeons National Surgical Quality Improvement Program database was used to identify all primary TKA procedures. Hyponatremia was defined as <135 mEq/L and normonatremia as 135 to 145 mEq/L; hypernatremic patients (>145 mEq/L) were excluded. Multivariable logistic regression was used to determine the association between hyponatremia and outcomes after adjusting for demographics and comorbidities. An α level of 0.002 was used and calculated using the Bonferroni correction. Our final analysis included 88,103 patients of which 3,763 were hyponatremic and 84,340 were normonatremic preoperatively. In our multivariable models, hyponatremic patients did not have significantly higher odds of experiencing an MM (odds ratio [OR]: 1.05; 99% confidence interval [CI] 0.93-1.19) or readmission (OR: 1.12; 99% CI: 1-1.24). However, patients with hyponatremia did experience significantly greater odds for reoperation (OR: 1.24; 99% CI: 1.05-1.46) and longer hospital stay (OR: 1.15; 99% CI: 1.09-1.21). We found that hyponatremic patients undergoing TKA had increased odds of reoperation and prolonged hospital stay. Preoperative hyponatremia may be a modifiable risk factor for adverse outcomes in patients undergoing TKA, and additional prospective studies are warranted to determine whether preoperative correction of hyponatremia can prevent complications.

Improved Perioperative Care of Elective Joint Replacement Patients: The Impact of an Orthopedic Perioperative Hospitalist.

BACKGROUND: We developed an orthopedic hospitalist fellowship program for our total joint replacement program at a large urban academic medical center. The goal of the program was to improve patient outcomes, quality, and healthcare value through collaborative perioperative care and improved care coordination. This study evaluates the implementation and impact of our modified Hospitalist-Orthopaedic Team Co-management model on quality and performance metrics. METHODS: We reviewed our Quality Institute data using 3 databases for the 16 months before (PreOH) and 18 months after (PostOH) implementation. Procedural volume was identical during period 1 (1100 cases) vs period 2 (1119 cases). Metrics included mean LOS (length of stay), % patients discharged home, mean observed and expected LOS and LOS index, LOS variance, % ICU (intensive care unit) admissions, mean ICU days, % cases with complications, % mortality, 30-day readmission rate, and Hospital Consumer Assessment of Healthcare Providers and Systems scores. Statistical analysis was performed using the software imbedded in the database software. RESULTS: Statistically significant improvements occurred in multiple performance and quality metrics including mean hospital LOS for total knee replacement, percentage of total knee replacement patients discharged home, and percentage of patients discharged home for primary total hip arthroplasty, complication rate, and 30-day readmission rate. Reductions in % ICU admission and ICU LOS were seen but not statistically significant. HCAPHS scores improved in 6 of 8 categories, and was statistically significant in 3 of 8. CONCLUSION: The results of this study demonstrate that the modified Hospitalist-Orthopaedic Team Co-management model described above improves quality, cost effectiveness, and value for elective total joint replacement patients in comparison to the traditional consultation only model.

Irrigation and Debridement with Component Retention for Acute Infection After Hip Arthroplasty: Improved Results with Contemporary Management.

BACKGROUND: There are conflicting data on the results of irrigation and debridement with component retention in patients with acute periprosthetic hip infections. The goals of this study were to examine contemporary results of irrigation and debridement with component retention for acute infection after primary hip arthroplasty and to identify host, organism, antibiotic, or implant factors that predict success or failure. METHODS: Ninety hips (57 total hip arthroplasties and 33 hemiarthroplasties) were diagnosed with acute periprosthetic hip infection (using strict criteria) and were treated with irrigation and debridement and component retention between 2000 and 2012. The mean follow-up was 6 years. Patients were stratified on the basis of McPherson criteria. Hips were managed with irrigation and debridement and retention of well-fixed implants with modular head and liner exchange (70%) or irrigation and debridement alone (30%). Seventy-seven percent of patients were treated with chronic antibiotic suppression. Failure was defined as failure to eradicate infection, characterized by a wound fistula, drainage, intolerable pain, or infection recurrence caused by the same organism strain; subsequent removal of any component for infection; unplanned second wound debridement for ongoing deep infection; and/or occurrence of periprosthetic joint infection-related mortality. RESULTS: Treatment failure occurred in 17% (15 of 90 hips), with component removal secondary to recurrent infection in 10% (9 of 90 hips). Treatment failure occurred in 15% (10 of 66 hips) after early postoperative infection and 21% (5 of 24 hips) after acute hematogenous infection (p = 0.7). Patients with McPherson host grade A had a treatment failure rate of 8%, compared with 16% (p = 0.04) in host grade B and 44% in host grade C (p = 0.006). Most treatment failures (12 of 15 failures) occurred within the initial 6 weeks of treatment; failures subsequent to 6 weeks occurred in 3% of those treated with chronic antibiotic suppression compared with 11% of those who were not treated with suppression (hazard ratio, 4.0; p = 0.3). CONCLUSIONS: The success rate was higher in this contemporary series than in many previous series. Systemic host grade A was predictive of treatment success. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

National Incidence of Reportable Quality Metrics in the Knee Arthroplasty Population.

BACKGROUND: The Centers for Medicare and Medicaid Services (CMS) characterizes adverse quality events in the inpatient setting as patient safety indicators (PSI). The incidence of PSI has not been quantified in the total knee arthroplasty (TKA) population. METHODS: All patients in the Nationwide Inpatient Sample who underwent primary TKA during an inpatient episode in 2013 were identified using International Classification of Disease, Ninth Revision, Clinical Modification codes. The incidence of PSI was determined using the International Classification of Disease, Ninth Revision diagnosis code algorithms used by CMS. Multivariable logistic regression was used to determine significant associations between patient level covariates (demographics, comorbidities, and hospital characteristics) and the risk of experiencing one or more PSI after TKA. RESULTS: We identified 132,453 primary TKA patients in the Nationwide Inpatient Sample in 2013. We estimated the national incidence rate of experiencing one or more PSI as 0.98%. After adjusting for patient demographics and hospital characteristics, we found that relative to Medicaid/self-pay patients, neither Medicare nor privately insured patients faced significantly different risk of experiencing one or more PSI after TKA. However, alcohol abuse, deficiency anemia, congestive heart failure, coagulopathy, and electrolyte imbalance were associated with increased risk of experiencing one or more PSI after TKA. CONCLUSION: The national incidence of PSI among TKA patients was lower than has been reported in other surgical populations. CMS uses the incidence of adverse quality events (measured using PSI) in part to determine hospital reimbursement. As value-based payment becomes more widely adopted in the United States, initiatives designed to eliminate and reduce PSI incidence can benefit vulnerable patient populations, physicians, and hospital systems.

National Incidence of Patient Safety Indicators in the Total Hip Arthroplasty Population.

BACKGROUND: The Centers for Medicare & Medicaid Services use the incidence of patient safety indicators (PSIs) to determine health care value and hospital reimbursement. The national incidence of PSI has not been quantified in the total hip arthroplasty (THA) population, and it is unknown if patient insurance status is associated with PSI incidence after THA. METHODS: All patients in the Nationwide Inpatient Sample (NIS) who underwent THA in 2013 were identified using the International Classification of Diseases, Ninth Revision, Clinical Modification codes. The incidence of PSI was determined using the International Classification of Diseases, Ninth Revision, diagnosis code algorithms published by the Centers for Medicare & Medicaid Services and the Agency for Healthcare Research and Quality. The association of insurance status and the incidence of PSI during the inpatient episode was determined by comparing privately insured and Medicare patients with Medicaid/self-pay patients using a logistic regression model that controlled for patient demographics, patient comorbidities, and hospital characteristics. RESULTS: In 2013, the NIS included 68,644 hospitalizations with primary THA performed during the inpatient episode. During this period, 429 surgically relevant PSI were recorded in the NIS. The estimated national incidence rate of PSI after primary THA was 0.63%. In our secondary analysis, the privately insured cohort had significantly lower odds of experiencing one or more PSIs relative to the Medicaid/self-pay cohort (odds ratio, 0.47; 95% confidence interval, 0.29-0.76). CONCLUSION: The national incidence of PSI among THA patients is relatively low. However, primary insurance status is associated with the incidence of one or more PSIs after THA. As value-based payment becomes more widely adopted in the United States, quality benchmarks and penalty thresholds need to account for these differences in risk-adjustment models to promote and maintain access to care in the underinsured population.

Are Readmissions After THA Preventable?

BACKGROUND: Readmissions after total joint arthroplasty have become a key quality measure in elective surgery in the United States. The Affordable Care Act includes the Hospital Readmission Reduction Program, which calls for reduced payments to hospitals with excessive readmissions. This policy uses a method to determine excess readmission ratios and calculate readmission payment adjustments to hospitals, however, it is unclear whether readmission rates are an effective quality metric. The reasons or conditions associated with readmission after elective THA have been well established but the extent to which readmissions can be prevented after THA remains unclear. QUESTIONS/PURPOSES: (1) Are unplanned readmissions after THA associated with orthopaedic or medical causes? (2) Are these readmissions preventable? (3) When during the course of aftercare are orthopaedic versus medical readmissions more likely to occur? METHODS: We retrospectively evaluated all 1096 elective THAs for osteoarthritis performed between January 1, 2011 and June 30, 2014 at a major academic medical center. Of those, 69 patients (6%) who met inclusion criteria were readmitted in our healthcare system within 90 days of discharge after the index procedure during the study period. Fifty patients were readmitted within 30 days of discharge after the index procedure (5%). We defined a readmission as any unplanned inpatient or observation status admission to the hospital spanning at least one midnight. A panel of physicians not involved in the care of these patients used available criteria and existing consensus guidelines to evaluate the medical records, radiographs, and operative reports to identify whether the underlying reason for readmission was orthopaedic versus medical. They subsequently were classified as either nonpreventable or potentially preventable readmissions, based on any care that may have occurred during the index hospitalization. To make such determinations, consensus specialty society guidelines were used whenever possible for each readmission diagnosis. RESULTS: A total of 50 of 1096 patients (5% of those who underwent THA during the period in question) were readmitted within 30 days and 69 of 1096 (6%) were readmitted within 90 days of their index procedures. Thirty-one patients were readmitted for orthopaedic reasons (31/69; 45%) and 38 of 69 were readmitted for medical reasons (55%). Three readmissions (three of 69; 4%) were identified as potentially preventable. Of these potentially preventable readmissions, one was orthopaedic (hip dislocation) and two were medical. Thirty-day readmissions were more likely to be orthopaedic than 90-day readmissions (odds ratio, 4.06; 95% CI, 1.18-13.96; p = 0.026). CONCLUSIONS: Using a panel of expert reviewers, available existing criteria, and consensus methodology, it appears only a small percentage of readmissions after THA are potentially preventable. Orthopaedic readmissions occur earlier during the postoperative course. Currently, existing policies and readmission penalties may not serve as valuable external quality metrics. The readmission rates in our study may represent the threshold for expected readmission rates after THA. Future studies should enroll larger numbers of patients and have independent review panels in efforts to refine criteria for what constitutes preventable readmissions. LEVEL OF EVIDENCE: Level III, therapeutic study.

Osteocutaneous pedicle flap transfer for salvage of transtibial amputation after severe lower-extremity injury.

BACKGROUND: A conventional transtibial amputation may not be possible when the zone of injury involves the proximal part of the tibia, or in cases of massive tibial bone and/or soft-tissue loss. The purpose of this study was to examine the outcomes of salvage of a transtibial amputation level with a rotational osteocutaneous pedicle flap from the ipsilateral hindfoot. METHODS: Fourteen patients who had an osteocutaneous pedicle flap from the ipsilateral foot were included in the study. Twelve patients were followed for more than twenty-four months (mean, 60.2 months) and were evaluated with use of the Sickness Impact Profile (SIP), Musculoskeletal Function Assessment (MFA), and a 100-ft (30.48-m) timed walking test. RESULTS: There were ten men and four women with mean age of 43.2 years. Thirteen patients had a type-IIIB open tibial fracture, and one had extensive soft-tissue loss secondary to a burn. Four patients were treated for infection after the index procedure. There were no nonunions of the tibia to the calcaneus. Three patients underwent late reconstructive procedures to improve prosthetic fit. No patient required subsequent revision to a more proximal amputation level. Mean knee flexion was 139°. CONCLUSIONS: A novel technique has been developed to salvage a transtibial amputation level with use of a rotational osteocutaneous flap from the hindfoot. In the absence of adequate tibial length and/or soft-tissue coverage to salvage the entire limb or to perform a conventional-length transtibial amputation, this technique is a highly functional alternative that does not require microvascular free tissue transfer.

Identification of oral bacterial DNA in synovial fluid of patients with arthritis with native and failed prosthetic joints.

OBJECTIVE: We examined the presence of bacterial DNA in synovial fluids of native or clinically aseptically failed prosthetic joints from patients having periodontal disease and arthritis to determine whether there is bacterial spread from the oral cavity to the joints. METHODS: A total of 36 subjects were enrolled in the study. Among these, 11 were diagnosed with rheumatoid arthritis (RA) and 25 were diagnosed with osteoarthritis (OA). Eight patients with OA and 1 patient with RA had failed prostheses. Synovial fluid was aspirated from the affected hip or knee joint. Pooled subgingival plaque samples were collected, followed by clinical periodontal examination. Bacterial DNA was extracted from the collected synovial fluid and dental plaque samples were followed by polymerase chain reactions and DNA sequence analysis of the 16S-23S rRNA genes. RESULTS: Of the 36 patients, bacterial DNA was detected in the synovial fluid samples from 5 patients (13.9%): 2 with RA (1 native and 1 failed prosthetic joints) and 3 with OA (1 native and 2 failed prosthetic joints). Of these 5 patients, 2 were diagnosed with periodontitis and had identical bacterial clones (Fusobacterium nucleatum and Serratia proteamaculans, respectively) detected in both the synovial fluid and the dental plaque samples. Fusobacterium nucleatum was the most prevalent, detected in 4 of the 5 positive samples. No cultures were done and no patients were treated with antibiotics or developed clinical infection. CONCLUSIONS: The present findings of bacterial DNA in the synovial fluid suggest the possibility of organisms translocating from the periodontal tissue to the synovium. We suggest that patients with arthritis or failed prosthetic joints be examined for the presence of periodontal diseases and be treated accordingly.

Why knees fail in 2011: patient, surgeon, or device?

The outcome of total knee arthroplasty (TKA) is influenced by multiple interconnected factors, including patient selection, implant design, and surgical technique. Total knee arthroplasty has been shown to be highly successful, with patient satisfaction rates reported from 85% to 95% with low rates of failure, but if failure occurs, its impact is significant. In 2003, 402,000 primary TKAs and 32,000 revision TKAs were performed in the United States, and the number of TKAs is expected to double by 2015. Recent data on modern implant designs and techniques have demonstrated a surprising number of early failures, although the true number of early failures is unknown. Patient medical comorbidities should be optimized preoperatively, while psychosocial issues and workers compensation are more nebulous yet contribute greatly to patient perceived outcomes. Understanding current failure mechanisms of primary TKA and how to prevent complications will be critical to help manage a potentially overwhelming TKA revision burden. This article discusses failure rates as well as factors from the patient, surgeon, and device, that contribute to TKA failure.

Incidence of postthrombotic syndrome in patients undergoing primary total hip arthroplasty for osteoarthritis.

BACKGROUND: Postthrombotic syndrome (PTS) is a chronic condition in the lower extremity that develops after deep vein thrombosis (DVT). The incidence of PTS after total hip arthroplasty (THA) is not well established. QUESTIONS/PURPOSES: We (1) determined the incidence of PTS after DVT in patients undergoing primary THA for osteoarthritis; and (2) determined whether the incidence of PTS was greater in patients with DVT than without. METHODS: We retrospectively reviewed records of all 1037 patients who underwent primary THA for osteoarthritis during a 4-year period. All patients underwent postoperative screening ultrasound. We identified 21 (2%) patients with a DVT by ultrasound of whom 14 had a minimum 1-year followup (mean, 3.4 years; range, 1.0-6.0 years). PTS was diagnosed if any two of the six clinical signs were documented. RESULTS: Three of 14 patients with DVT had at least two signs consistent with PTS; two of these had a DVT proximal to the soleal arch. Three of 91 randomly matched patients undergoing THA without DVT had at least two signs of PTS. The incidence of developing PTS after THA appeared higher in patients with DVT than in patients without DVT. CONCLUSIONS: While we observed a difference between the incidence of PTS after THA in patients with and without DVT, that incidence was based on only three of 1037 patients with DVT after THA. PTS does not appear to be a major complication after DVT in patients undergoing THA. LEVEL OF EVIDENCE: Level III, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.

Surgical Techniques for Staged Revision of the Chronically Infected Total Knee Arthroplasty.

Infection after total knee arthroplasty is a rare yet devastating complication requiring multiple hospitalizations, operations, and outpatient visits placing a significant burden on both patient and treating surgeon. Two-stage exchange protocols for the treatment of the chronically infected total knee arthroplasty remain the standard of care in the United States. Thorough debridement, use of antibiotic spacers, treatment with parenteral antibiotics, and delayed reimplantation have resulted in treatment success rates greater than 90%. The use of antibiotic cement spacers has led to increased range of motion, preservation of the joint space, and maintenance of cleaner soft tissue plains making surgery at the time of reimplantation less arduous. This article describes our current surgical technique used for two-stage revision of the chronically infected total knee including: (1) exposure, (2) implant removal and debridement, and (3) construction of both static and mobile antibiotic spacers.

Incidence of postthrombotic syndrome in patients undergoing primary total knee arthroplasty for osteoarthritis.

UNLABELLED: Postthrombotic syndrome (PTS) is characterized by edema, venous ectasia, hyperpigmentation, varicose veins, venous ulceration, and pain with calf compression after deep venous thrombosis (DVT). We determined the incidence of PTS after DVT diagnosed on screening ultrasound in patients undergoing primary total knee arthroplasty (TKA) for osteoarthritis (OA). We retrospectively reviewed the records of 1406 patients who underwent primary TKA for osteoarthritis and compared the incidence of PTS in patients without and with DVT. All patients had postoperative screening ultrasound. From these 1406 patients we identified 66 (4.7%) who had DVT, 50 of whom had a minimum of 1 year followup (mean, 4.97 years; range, 1.00-7.53 years). PTS was diagnosed if any two of six signs were documented in the medical record. Three of 50 patients with DVT (6%) had signs consistent with PTS; two of these three had a DVT proximal to the soleal arch. Seven (8%) of 88 patients randomly chosen for primary TKA because of OA with similar mean age and gender, but without DVT, had signs of PTS. PTS does not seem to be a major sequela of DVT in patients undergoing primary TKA for OA. LEVEL OF EVIDENCE: Level III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Zirconia versus Co-Cr femoral heads in total hip arthroplasty: early assessment of wear.

Polyethylene wear and associated osteolysis are major limitations to the long-term success of total hip arthroplasty. In vitro laboratory studies suggest polyethylene wear in THA may be substantially reduced with ceramic femoral heads. We evaluated the potential value of zirconia ceramic on conventional polyethylene as an "alternative bearing" for total hip arthroplasty in a prospective, randomized clinical trial in comparison with femoral heads made of Co-Cr-Mo. Patients were evaluated with standardized clinical outcome instruments, and measurement of head penetration was performed with computerized wear measurement software. Study enrollment was halted because of a recall of the zirconia heads. At that time, 30 total hip arthroplasties with Co-Cr-Mo heads and 30 total hip arthroplasties with zirconia heads had been performed. Mean followup was similar for both groups (Co-Cr- Mo = 51.7 months; zirconia = 51.2 months). The mean annual head penetration rate was low and similar for both groups (Co-Cr-Mo = 0.060 mm/year; and zirconia = 0.055 mm/year). In view of the recently reported potential for zirconia ceramics to undergo monoclinic phase transformation in vivo, with resultant increased fracture risk and degradation of wear properties, we do not recommend use of zirconia femoral heads as an "alternative bearing" for total hip arthroplasty.

Cementless two-staged total hip arthroplasty for deep periprosthetic infection.

UNLABELLED: bTwo-staged exchange with delayed reimplantation of a new prosthesis is considered by many to be the preferred method of treatment for deep periprosthetic infection after total hip arthroplasty. Until recently, most authors of previously published reports of this two-staged exchange procedure have used cemented implants fixed with antibiotic-containing bone cement. In view of the superior results of revision total hip arthroplasties with cementless implants, we reviewed the results of 33 two-staged revision total hip arthroplasties done for deep infection using cementless femoral components. There were no recurrent infections in the 28 patients in this study who had a 2-year minimum followup. Two patients developed a new infection with a different organism after reimplantation of their hip. Three patients with considerable acetabular bone deficiency had acetabular component revision for aseptic loosening; however, there were no cases of femoral component loosening. The overall infection rate of 7% using this approach was comparable to previous reports of two-staged revision total hip arthroplasties done with cemented components fixed with antibiotic-containing bone cement. In addition, cementless femoral component fixation seemed to be more reliable and durable in comparison to previous reports of revision total hip arthroplasty with cemented stems. The results of this study support the continued use of cementless implant fixation for two-staged reconstruction of the infected total hip arthroplasty. LEVEL OF EVIDENCE: Therapeutic study, Level IV-1 (case series). See the Guidelines for Authors for a complete description of levels of evidence.