A comparison of clinical- and patient-reported outcomes of the cemented ATTUNE and PFC sigma fixed bearing cruciate sacrificing knee systems in patients who underwent total knee replacement with both prostheses in opposite knees

BACKGROUND

The ATTUNE Knee by DePuy Synthes was introduced in 2013. It is designed to provide better range of motion and address patient-reported instability. The PFC Sigma Knee, an earlier prosthesis by DePuy Synthes, is a common knee replacement with a strong clinical track record. Our aim is to compare the outcomes after primary total knee replacement for end-stage knee osteoarthritis of the PFC and ATTUNE knee systems in 21 patients who each have prosthesis in opposite knees using WOMAC, Oxford Knee and SF-12 scores and evaluation of range of motion.

METHODS

A review was carried out on 21 patients who underwent primary total knee replacement with both the ATTUNE and PFC knee systems. These were staged operations performed in the same institution and by the same surgeon. All cases were followed up for a minimum of 6 months. WOMAC, Oxford Knee and SF-12 scores, as well as knee range of motion were recorded preoperatively and at 6 months postoperatively.

RESULTS

There was a significant difference in pre- to 6-month post-operative outcomes in PFC and ATTUNE groups with regard to improvement in range of motion (10° ± 8 and 13° ± 11, respectively). There was also a significant improvement in WOMAC scores (PFC group) and Oxford Knee Scores (ATTUNE group) (8.9 ± 7.7 and 12.1 ± 8.4, respectively). There was a significant improvement in SF-12 Score in both groups (10.1 ± 9.3 for PFC and 15.8 ± 13.3 for ATTUNE). The minimum clinically important difference (MCID) in scoring systems at 6 months was reached by 6 patients in the PFC group and 12 in the ATTUNE group.

CONCLUSION

A significant difference was demonstrated in clinical outcome at 6 months postoperatively between PFC and ATTUNE knee systems in patients who underwent total knee arthroplasty with both prostheses. Superior results were recorded for the ATTUNE knee system.

Re-admissions treble the risk of late mortality after primary total hip arthroplasty

BACKGROUND

Following a total hip arthroplasty (THA), early hospital re-admission rates of 3-11% are considered as 'acceptable' in terms of medical care cost policies. Surprisingly, the impact of re-admissions on mortality has not been priorly portrayed. Therefore, we sought to determine the mortality rate after 90-day re-admissions following a THA in a series of patients from a captive medical care program.

PATIENTS AND METHODS

We prospectively analysed 90-day readmissions of 815 unilateral, elective THA patients operated upon between 2010 and 2014 whose medical care was the one offered by our institution. We stratified our sample into readmitted and non-readmitted cohorts. Through a Cox proportional hazards model, we compared demographic characteristics, clinical comorbidities, surgical outcomes and laboratory values between both groups in order to determine association with early and late mortality.

RESULTS

We found 37 (4.53%) re-admissions at a median time of 40.44 days (IQR 17.46-60.69). Factors associated with re-admission were hospital stay (p = 0.00); surgical time (p = 0.01); chronic renal insufficiency (p = 0.03); ASA class 4 (p = 0.00); morbid obesity (p = 0.006); diabetes (p = 0.04) and a high Charlson index (p = 0.00). Overall mortality rate of the series was 3.31% (27/815). Median time to mortality was 455.5 days (IQR 297.58-1170.65). One-third (11/37) of the re-admitted patients died, being sepsis non-related to the THA the most common cause of death. After adjusting for confounders, 90-day re-admissions remained associated with mortality with an adjusted HR of 3.14 (CI95% 1.05-9.36, p = 0.04).

CONCLUSIONS

Unplanned re-admissions were an independent risk factor for future mortality, increasing three times the risk of mortality.

Pauwels Osteotomy for Femoral Neck Nonunion in Two Adult Siblings with Osteogenesis Imperfecta

This is a retrospective review of two adult siblings with osteogenesis imperfecta (OI) type III (according to Sillence classification), who sustained a spontaneous femoral neck fracture and subsequent nonunion. The diagnosis of OI in these two patients was made based on clinical, radiological and genetic findings. The fracture was most likely caused by femoroacetabular impingement secondary to OI induced acetabular protrusio. A valgus osteotomy according to Pauwels'principles and fixation of the osteotomy and nonunion with a locking plate resulted in healing despite compromised bone quality and limited bone stock. Long-term follow up (4.5 years and 6.5 years, respectively) is provided.

When treating this difficult problem, improving the mechanobiological environment and decreasing the femoroacetabular impingement by a Pauwels type osteotomy should be considered.

Endogenous Opiates and Behavior: 2016

This paper is the thirty-ninth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2016 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia, stress and social status, tolerance and dependence, learning and memory, eating and drinking, drug abuse and alcohol, sexual activity and hormones, pregnancy, development and endocrinology, mental illness and mood, seizures and neurologic disorders, electrical-related activity and neurophysiology, general activity and locomotion, gastrointestinal, renal and hepatic functions, cardiovascular responses, respiration and thermoregulation, and immunological responses.

Synchrotron analysis of human organ tissue exposed to implant material

BACKGROUND

Orthopaedic implants made of cobalt-chromium alloy undergo wear and corrosion that can lead to deposition of cobalt and chromium in vital organs. Elevated cardiac tissue cobalt levels are associated with myocardial injury while chromium is a well-established genotoxin. Though metal composition of tissues surrounding hip implants has been established, few investigators attempted to characterize the metal deposits in systemic tissues of total joint arthroplasty patients.

METHODS

We report the first use of micro-X-ray fluorescence coupled with micro-X-ray absorption spectroscopy to probe distribution and chemical form of cobalt, chromium and titanium in postmortem samples of splenic, hepatic and cardiac tissue of patients with metal-on-polyethylene hip implants (n = 5).

RESULTS

Majority of the cobalt was in the 2+ oxidation state, while titanium was present exclusively as titanium dioxide, in either rutile or anatase crystal structure. Chromium was found in a range of forms including a highly oxidised, carcinogenic species (CrV/VI), which has never been identified in human tissue before.

CONCLUSIONS

Carcinogenic forms of chromium might arise in vital organs of total joint arthroplasty patients. Further studies are warranted with patients with metal-on-metal implants, which tend to have an increased release of cobalt and chromium compared to metal-on-polyethylene hips.

Extra-articular deformities in arthritic knees-a grueling challenge for arthroplasty surgeons: An evidence-based update

Critical to the success of a total knee arthroplasty (TKA) is the anatomical alignment. This may appear as a challenge in an extra-articular deformity (EAD) that may be inherent in certain people or result from fracture malunion, congenital disorders, nutritional, metabolic and infective causes. This appraisal aimed at providing the reader with an up-todate overview of the research carried out on, and existent evidence of EAD correction while planning a TKA. We reviewed the current English literature on TKA in extra-articular knee deformities. Among the published data, a common initial approach of mandatory clinical and radiological assessment emerges as an obligatory step while handling cases with EAD. While several methods of managing the deformity and arthritis have been described, a broad division into intra-articular and extra-articular means can be deciphered. The relatively old-school, yet reliable thought process of extra-articular correction allows an all-inclusive restoration of alignment with the inherent complications related to the necessary osteotomy. A cohort of younger and more venturesome surgeons seem inclined towards performing navigated, intra-articular correction for mild to moderate and sometimes, severe deformities. The crux of the matter lies is obtaining a well-balanced knee without violating the all-important cruciates. Restoring the patient’s ambulatory status seems sooner with the intra-articular methods which are also more precise in determining the axes and while removing minimum bone. Greatest satisfaction is accomplished in those with less grotesque, rotationallyaligned knees while meticulously balancing soft-tissues and encouraging earlier weightbearing.

Administrative Costs Associated With Physician Billing and Insurance-Related Activities at an Academic Health Care System

Importance

Administrative costs in the US health care system are an important component of total health care spending, and a substantial proportion of these costs are attributable to billing and insurance-related activities.

Objective

To examine and estimate the administrative costs associated with physician billing activities in a large academic health care system with a certified electronic health record system.

Design, Setting, and Participants

This study used time-driven activity-based costing. Interviews were conducted with 27 health system administrators and 34 physicians in 2016 and 2017 to construct a process map charting the path of an insurance claim through the revenue cycle management process. These data were used to calculate the cost for each major billing and insurance-related activity and were aggregated to estimate the health system's total cost of processing an insurance claim.

Exposures

Estimated time required to perform billing and insurance-related activities, based on interviews with management personnel and physicians.

Main Outcomes and Measures

Estimated billing and insurance-related costs for 5 types of patient encounters: primary care visits, discharged emergency department visits, general medicine inpatient stays, ambulatory surgical procedures, and inpatient surgical procedures.

Results

Estimated processing time and total costs for billing and insurance-related activities were 13 minutes and $20.49 for a primary care visit, 32 minutes and $61.54 for a discharged emergency department visit, 73 minutes and $124.26 for a general inpatient stay, 75 minutes and $170.40 for an ambulatory surgical procedure, and 100 minutes and $215.10 for an inpatient surgical procedure. Of these totals, time and costs for activities carried out by physicians were estimated at a median of 3 minutes or $6.36 for a primary care visit, 3 minutes or $10.97 for an emergency department visit, 5 minutes or $13.29 for a general inpatient stay, 15 minutes or $51.20 for an ambulatory surgical procedure, and 15 minutes or $51.20 for an inpatient surgical procedure. Of professional revenue, professional billing costs were estimated to represent 14.5% for primary care visits, 25.2% for emergency department visits, 8.0% for general medicine inpatient stays, 13.4% for ambulatory surgical procedures, and 3.1% for inpatient surgical procedures.

Conclusions and Relevance

In a time-driven activity-based costing study in a large academic health care system with a certified electronic health record system, the estimated costs of billing and insurance-related activities ranged from $20 for a primary care visit to $215 for an inpatient surgical procedure. Knowledge of how specific billing and insurance-related activities contribute to administrative costs may help inform policy solutions to reduce these expenses.

Development of finite element model for customized prostheses design for patient with pelvic bone tumor

The aim of this study was to design a hemi-pelvic prosthesis for a patient affected by pelvic sarcoma. To investigate the biomechanical functionality of the pelvis reconstructed with designed custom-made prosthesis, a patient-specific finite element model of whole pelvis with primary ligaments inclusive was constructed based on the computed tomography images of the patient. Then, a finite element analysis was performed to calculate and compare the stress distribution between the normal and implanted pelvis models when undergoing three different static conditions-both-leg standing, single-leg standing for the healthy and the affected one. No significant differences were observed in the stresses between the normal and reconstructed pelvis for both-leg standing, but 20%-40% larger stresses were predicted for the peak stress of the single-leg standing (affected side). Moreover, two- to threefold of peak stresses were predicted within the prostheses compared to that of the normal pelvis especially for single-leg standing case, however, still below the allowable fatigue limitation. The study on the load transmission functionality of prosthesis indicated that it is crucial to carry out finite element analysis for functional evaluation of the designed customized prostheses before three-dimensional printing manufacturing, allowing better understanding of the possible peak stresses within the bone as well as the implants for safety precaution. The finite element model can be equally applicable to other bone tumor model for biomechanical studying.

Rapid destructive osteoarthritis of the hip after intra-articular steroid injection

Rapid destructive osteoarthritis of the hip is a separate entity different from the usual osteoarthritis. It is usually seen in elderly women, and the characteristic feature is the rapid progression within 6 to 12 months to complete destruction of the joint. The exact etiology is not known. We present a rare case of rapid destructive osteoarthritis of the hip in a 62-year-old woman who developed it within 2 months of intra-articular steroid injection, which was managed well with uncemented total hip arthroplasty. Through this report, we emphasize the possibility of the disastrous complication of injection, which should be informed to the patient before any intra-articular injection.

Total Knee Arthroplasty: Does Day of Surgery Matter?

Introduction

There has been an influx of research studies aimed at identifying all factors that contribute to minimizing cost and maximizing postoperative care after total knee arthroplasty (TKA). Length of stay (LOS) has been defined as a significant factor that contributes to increased burden. We aimed at looking whether day of surgery has any significant effect on the LOS and postoperative complications following total knee arthroplasty (TKA).

Materials and methods

Retrospective cohort study done at the Aga Khan University Hospital, Pakistan, from January 2007 to December 2015. A total of 611 patients who underwent a unilateral or bilateral total knee arthroplasty (TKA) were included in study: 269 (44.0%) patients underwent unilateral TKA and 342 (56.0%) underwent a bilateral TKA.

Results

Kruskal-Wallis test and post hoc pairwise comparisons showed that unilateral TKAs performed on Tuesday, Saturday, and Sunday resulted in a lower median LOS (P < .05). No significant association was seen in bilateral TKA group. Day of surgery was not associated with postoperative complications.

Conclusions

Unilateral TKAs performed earlier during the week and later on the weekend are associated with a significantly lower LOS. It is highly probable that patch ancillary services during the latter part of the week and a higher workload for the staff are important reasons for this phenomenon.

Third-generation pure alumina and alumina matrix composites in total hip arthroplasty: What is the evidence?

Wear, corrosion and periprosthetic osteolysis are important causes of failure in joint arthroplasty, especially in young patients.

Ceramic bearings, developed 40 years ago, are an increasingly popular choice in hip arthroplasty. New manufacturing procedures have increased the strength and reliability of ceramic materials and reduced the risk of complications.

In recent decades, ceramics made of pure alumina have continuously improved, resulting in a surgical-grade material that fulfills clinical requirements.

Despite the track record of safety and long-term results, third-generation pure alumina ceramics are being replaced in clinical practice by alumina matrix composites, which are composed of alumina and zirconium.

In this review, the characteristics of both materials are discussed, and the long-term results with third-generation alumina-on-alumina bearings and the associated complications are compared with those of other available ceramics.

Cite this article: EFORT Open Rev 2018;3:7-14. DOI: 10.1302/2058-5241.3.170034

Cost-effective peri-operative pain management: assuring a happy patient after total knee arthroplasty

Aims

The aim of this study was to determine the optimal regimen for the management of pain following total knee arthroplasty (TKA) by comparing the outcomes and cost-effectiveness of different protocols implemented at a large, urban, academic medical centre.

Patients and Methods

Between September 2013 and September 2015, we used a series of modifications to our standard regimen for the management of pain after TKA. In May 2014, there was a department-wide transition from protocols focused on femoral nerve blocks (FNB) to periarticular injections of liposomal bupivacaine. In February 2015, patient-controlled analgesia (PCA) was removed from the protocol while continuing liposomal bupivacaine injections. Quality measures and hospital costs were compared between the three protocols.

Results

The cohort being treated with PCA-less liposomal bupivacaine injections had a significantly higher percentage of patients who were discharged to their home (p = 0.010) and a significantly shorter length of stay (p < 0.001). Patient-reported Hospital Consumer Assessment of Healthcare Providers and Systems (HCAHPS) scores relating to pain being “well-controlled” and “overall pain management” also favoured this cohort (p = 0.214 and p = 0.463, respectively), in which cost was significantly lower compared with the other two cohorts (p = 0.005).

Conclusion

The replacement of FNBs injections and the removal of PCAs, both of which are known to be associated with high rates of adverse outcomes, and the addition of liposomal bupivacaine periarticular injections to a multimodal pain regimen, led to improvements in many quality measures, HCAHPS pain scores, and cost-effectiveness.

Cite this article: Bone Joint J 2018;100-B(1 Supple A):55–61.

Trunnion corrosion: what surgeons need to know in 2018

AIMS

To present a surgically relevant update of trunnionosis.

MATERIALS AND METHODS

Systematic review performed April 2017.

RESULTS

Trunnionosis accounts for approximately 2% of the revision total hip arthroplasty (THA) burden. Thinner (reduced flexural rigidity) and shorter trunnions (reduced contact area at the taper junction) may contribute to mechanically assisted corrosion, exacerbated by high offset implants. The contribution of large heads and mixed metallurgy is discussed.

CONCLUSION

Identifying causative risk factors is challenging due to the multifactorial nature of this problem. Cite this article: Bone Joint J 2018;100-B(1 Supple A):44-9.

Local Infiltration Analgesia With Liposomal Bupivacaine Improves Pain Scores and Reduces Opioid Use After Total Knee Arthroplasty: Results of a Randomized Controlled Trial

BACKGROUND

Local infiltration analgesia (LIA) with liposomal bupivacaine (LB) in patients undergoing total knee arthroplasty (TKA) has yielded mixed results. The PILLAR study, which was designed to minimize limitations associated with previous studies, compared the effects of LIA with or without LB on pain scores, opioid consumption, including proportion of opioid-free patients, time to first opioid rescue, and safety after primary unilateral TKA.

METHODS

Patients (N = 140) were randomized to LIA with LB 266 mg/20 mL (admixed with bupivacaine HCl 0.5%, 20 mL) or LIA with bupivacaine HCl 0.5%, 20 mL. Standardized infiltration techniques and a standardized multimodal pain management protocol were used. The coprimary efficacy endpoints were area under the curve (AUC) of visual analog scale pain intensity scores 12-48 hours (AUC_12-48) postsurgery and total opioid consumption 0-48 hours postsurgery.

RESULTS

Mean AUC_12-48 of visual analog scale pain intensity score was 180.8 with LB and 209.3 without LB (least squares [LS] mean treatment difference -26.88, P = .0381). LS mean total opioid consumption 0-48 hours postsurgery was 18.7 mg with and 84.9 mg without LB (LS ratio 0.220, P = .0048). Significant differences in favor of LB were observed for the percentage of opioid-free patients (P < .01) and time to first opioid rescue (P = .0230). Treatments were similarly well tolerated.

CONCLUSION

This study provides data on LIA with LB administered using optimal techniques specific to TKA. In this setting, LIA with LB significantly improved postsurgical pain, opioid consumption, and time to first opioid rescue, with more opioid-free patients and no unexpected safety concerns.

Implementation of Preoperative Screening Criteria Lowers Infection and Complication Rates Following Elective Total Hip Arthroplasty and Total Knee Arthroplasty in a Veteran Population

BACKGROUND

Total hip arthroplasty (THA) and total knee arthroplasty (TKA) are common procedures with a risk of complications. Attempting to minimize complications, our institution implemented preoperative screening criteria for patients undergoing elective total joint replacement. Our study aimed to determine if screening criteria lowered total complications and/or surgical site infections (SSI).

METHODS

Two groups of consecutive patients undergoing TKA and THA at a single Veterans Affairs facility were evaluated prior to and after implementation of screening criteria, 520 and 475 respectively. Screening criteria included hemoglobin A1c ≤7, hemoglobin ≥11, body mass index ≤35, and albumin ≥3.5. Groups were analyzed for demographics, preoperative comorbidities, and postoperative complications. Rates of total complications and SSI were compared. Average follow-up was at least 2 years with minimum of 1 year.

RESULTS

Demographics and comorbidities outside the screening criteria were similar. Total complication rate was reduced from 35.4% to 14.8% (P < .01) after implementation of screening criteria. For TKA, total complications were reduced from 33.1% to 15.0% (P < .01) and for THA they were reduced from 42.4% to 14.2% (P < .01). SSI rates for combined TKA and THA were reduced from 4.4% to 1.3% (P < .01). For knees, SSI was reduced from 4.6% to 1.3% (P = .01) and was statistically significant. For THA, SSI decreased from 3.8% to 1.2% (P < .05).

CONCLUSION

Our institution saw a statistically significant decrease in both SSI and total complications following implementation of preoperative screening criteria for elective TKA and THA.

Increasing Perioperative Communication With Automated Mobile Phone Messaging in Total Joint Arthroplasty

BACKGROUND

Automated mobile phone messaging has not been reported in total joint arthroplasty (TJA). Our purpose was to compare Press Ganey (PG) and Hospital Consumer Assessment of Healthcare Providers and Systems (HCAHPS) scores between TJA patients who did and did not receive perioperative automated mobile phone messages.

METHODS

Patients were prospectively enrolled and received messages for 1 week prior until 2 weeks after TJA. Message content included reminders, activity, and pain control. Patients answered select PG/HCAHPS and questions regarding their experience with the automated communication platform. Average PG/HCAHPS scores were compared to historical TJA patients in the 3-year window prior (control group) with significance P < .05.

RESULTS

Thirty-seven consecutive patients were approached and 92% (n = 34) were enrolled. The experimental group was 47% male, with 80% patients between 51 and 75 years. The experimental (n = 30) and control groups (n = 26) were similar. Patients receiving messages were more likely to have a good understanding of health responsibilities (P = .024) and feel that the care team demonstrated shared decision-making (P = .024). Of patients enrolled, 87% felt messages helped them be more prepared for surgery, 100% felt messages kept them better informed, and 97% would participate again.

CONCLUSION

TJA patients who received perioperative communication via automated mobile phone messaging had improved patient satisfaction scores postoperatively. Patients perceived this form of communication was useful and kept them better informed. Automated mobile phone messaging can be an easily integrated, helpful adjunct to surgeons, healthcare systems, and case managers to more effectively communicate with patients undergoing TJA in this era of value-based care.

Outpatient Total Knee Arthroplasty: Are We There Yet? (Part 2)

The method by which surgeons conduct outpatient total knee procedures has yet to be fully elucidated. Literature demonstrates different experiences from various care protocols in place across the nation. This article reviews current recommendations for implementing successful total knee arthroplasty (TKA) and unicompartmental knee arthroplasty outpatient protocols. Specifically, information regarding anesthesia and analgesia modalities, perioperative care, operative technique, and postoperative care within outpatient TKA pathways is discussed.

A comparative analysis of femoral nerve block with adductor canal block following total knee arthroplasty: A systematic literature review

Background:

Patients undergoing total knee arthroplasty suffer from moderate-to-severe postoperative pain resulting in immobility-related complications and prolonged hospitalization. Femoral nerve block is associated with reduction in the quadriceps strength and increasing incidence of falls. Adductor canal block has been shown to be as effective as femoral nerve block without causing quadriceps weakness.

Objectives:

To compare outcomes of studies comparing adductor canal block and femoral nerve block in patients undergoing primary total knee arthroplasty.

Data Sources:

Original articles, published between July 2013 and April 2017, comparing the above interventions.

Study Eligibility Criteria, Participants, and Interventions:

Comparison of outcome measures of all original articles shortlisted by the PUBMED and Google Scholar databases search using key words, “adductor canal block; femoral nerve block; total knee arthroplasty; total knee replacement.”

Study Appraisal and Synthesis Methods:

The primary outcome measures reviewed were: pain scores; interventional failure; post-operative opioid consumption; patient fall or near fall during postoperative rehabilitation; and length of stay.

Results:

The opioid consumption was found to be comparable with both the interventions on the first and second postoperative day. Patients administered adductor canal block had better quadriceps power, longer ambulation distance, and shorter length of hospital stay.

Limitations:

Of the studies reviewed five were retrospective and thus data quality amongst the studies may have been compromised.

Conclusions and Implications of Key Findings:

Mobilization and ambulation, which are both important for recovery after total knee arthroplasty are both inhibited less by adductor canal block.

Outcomes of dual mobility components in total hip arthroplasty

Aims

Instability remains a challenging problem in both primary and revision total hip arthroplasty (THA). Dual mobility components confer increased stability, but there are concerns about the unique complications associated with these designs, as well as the long-term survivorship.

Materials and Methods

We performed a systematic review of all English language articles dealing with dual mobility THAs published between 2007 and 2016 in the MEDLINE and Embase electronic databases. A total of 54 articles met inclusion criteria for the final analysis of primary and revision dual mobility THAs and dual mobility THAs used in the treatment of fractures of the femoral neck. We analysed the survivorship and rates of aseptic loosening and of intraprosthetic and extra-articular dislocation.

Results

For the 10 783 primary dual mobility THAs, the incidence of aseptic loosening was 1.3% (142 hips); the rate of intraprosthetic dislocation was 1.1% (122 hips) and the incidence of extra-articular dislocation was 0.46% (41 hips). The overall survivorship of the acetabular component and the dual mobility components was 98.0%, with all-cause revision as the endpoint at a mean follow-up of 8.5 years (2 to 16.5). For the 3008 revision dual mobility THAs, the rate of aseptic acetabular loosening was 1.4% (29 hips); the rate of intraprosthetic dislocation was 0.3% (eight hips) and the rate of extra-articular dislocation was 2.2% (67 hips). The survivorship of the acatabular and dual mobility components was 96.6% at a mean of 5.4 years (2 to 8). For the 554 dual mobility THAs which were undertaken in patients with a fracture of the femoral neck, the rate of intraprosthetic dislocation was 0.18% (one hip), the rate of extra-articular dislocation was 2.3% (13 hips) and there was one aseptic loosening. The survivorship was 97.8% at a mean of 1.3 years (0.75 to 2).

Conclusion

Dual mobility articulations are a viable alternative to traditional bearing surfaces, with low rates of instability and good overall survivorship in primary and revision THAs, and in those undertaken in patients with a fracture of the femoral neck. The incidence of intraprosthetic dislocation is low and limited mainly to earlier designs. High-quality, prospective, comparative studies are needed to evaluate further the use of dual mobility components in THA. Cite this article: Bone Joint J 2018;100-B:11–19.

Arthroprosthetic cobaltism associated with cardiomyopathy

Systemic cobaltism related to metal-on-metal total hip arthroplasty has been published in case reports and series with effects on the cardiac, neurologic, endocrine, and immunologic systems. This case report presents a 46-year-old male who underwent bilateral metal-on-metal total hip arthroplasty and subsequently developed cardiomyopathy requiring left ventricular assist device implantation. Intervention with bilateral revision to non-cobalt-containing implants resulted in improved cardiac function. This case report will alert clinicians to the presentation of this rare but devastating complication while also displaying improvement following revision total hip arthroplasty. It is our hope this case will aid in early recognition and intervention of this condition.

Characteristics of Cobalt-Related Cardiomyopathy in Metal Hip Implant Patients: An Evaluation of 15 Published Reports

Over 300,000 hip replacements occurred in the USA in 2010, and the frequency is likely increasing annually. Blood Cobalt (Co) concentrations in patients with well-functioning cobalt-chromium (Co-Cr) hip implants are usually elevated above background concentrations relative to the general population. Excessive Co exposure, in rare cases, can result in cardiomyopathy. The purpose of this review was to identify cases of cardiomyopathy in metal-containing hip implant patients and to evaluate the possible cause of each patient's cardiomyopathy. We evaluated 15 cases published between 2009 and 2016, and, based on a review of the preexisting risk factors, blood Co concentrations, and histopathological information published for each patient, they were stratified into one of four categories regarding the association between Co exposure and the development of cardiomyopathy: (1) Co was causal (five cases); (2) Co was contributory (two cases); (3) Co was possibly contributory (six cases); and (4) Co was non-causal (two cases). In all 15 cases, blood Co concentrations (14-6521 μg/L) were elevated beyond levels associated with the majority of metal-containing implant patients (0.1-10 μg/L), and, in many cases, there was evidence of a malfunctioning implant. The data indicate that individuals with well-functioning implants, even those with preexisting risk factors, are at no risk of developing cardiac effects. We conclude that blood Co measurements are informative, but should be interpreted with caution, and in context of other factors evaluated in this analysis. The mere presence of elevated Co is not sufficient to indicate causation for a patient's cardiomyopathy.

Myocardial Cobalt Levels Are Elevated in the Setting of Total Hip Arthroplasty

BACKGROUND

Arthroplasty implants commonly contain elemental metal that may undergo wear-related release. Recently, cases of hip implant-associated myocardial injury have been reported. However, we are not aware of any previous study that has systematically measured myocardial metal levels or examined the relationship with total hip arthroplasty (THA).

METHODS

Archives of our institution were queried for autopsies of individuals who had undergone THA between 1990 and 2013. Myocardial tissue samples were analyzed for cobalt (Co) and chromium (Cr) levels with inductively coupled plasma mass spectroscopy. Seventy-five Co/Cr-on-polyethylene THA cases were included (mean age at time of death = 77.4 years; 49% women) as were 73 non-arthroplasty controls matched for age, sex, and history of hypertension and diabetes mellitus.

RESULTS

Significantly higher median myocardial concentrations of Co were observed in individuals with THA compared with controls (0.12 versus 0.06 μg/g, p < 0.0001). The median Co concentration was 69% higher in patients who had undergone THA revision (0.169 μg/g) than in those who underwent primary THA (0.100 μg/g; p = 0.004). In general, higher Co levels were observed in those with multiple replaced joints, although this finding only trended toward significance. Cardiomegaly, interstitial fibrosis, and decreased ejection fraction were observed more frequently in the postmortem samples of patients with implants than in those of controls (p = 0.0002, 0.044, and 0.0039, respectively).

CONCLUSIONS

We believe this to be the first study to quantify metal levels in cardiac tissue in patients with and without joint replacement. The elevated Co levels, in concert with cardiomegaly and increased interstitial fibrosis found during autopsy, in the arthroplasty cohort are novel, important findings. Although Co levels were significantly elevated above those in controls, the majority were below those seen in clinical case reports of death from Co cardiotoxicity associated with metal-on-metal prostheses.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Management of Chronic Massive Traumatic Popliteal Artery Pseudoaneurysm: A Case Series With Different Treatment Strategies

Giant traumatic popliteal artery (PA) pseudoaneurysms (PSA) are rare but limb threatening if untreated. Management can be challenging, as no standardized approach exists. This report evaluates our experience with 3 cases treated differently. Treatment is individualized based on patient disease and comorbidities. Endovascular and local patch arterial repair are safe alternatives to graft bypass when feasible.

An Approach to Developing Customized Total Knee Replacement Implants

Total knee replacement (TKR) has been performed for patients with end-stage knee joint arthritis to relieve pain and gain functions. Most knee replacement patients can gain satisfactory knee functions; however, the range of motion of the implanted knee is variable. There are many designs of TKR implants; it has been suggested by some researchers that customized implants could offer a better option for patients. Currently, the 3-dimensional knee model of a patient can be created from magnetic resonance imaging (MRI) or computed tomography (CT) data using image processing techniques. The knee models can be used for patient-specific implant design, biomechanical analysis, and creating bone cutting guide blocks. Researchers have developed patient-specific musculoskeletal lower limb model with total knee replacement, and the models can be used to predict muscle forces, joint forces on knee condyles, and wear of tibial polyethylene insert. These available techniques make it feasible to create customized implants for individual patients. Methods and a workflow of creating a customized total knee replacement implant for improving TKR kinematics and functions are discussed and presented in this paper.

Autoimmune heparin-induced thrombocytopenia

Autoimmune heparin-induced thrombocytopenia (aHIT) indicates the presence in patients of anti-platelet factor 4 (PF4)-polyanion antibodies that are able to activate platelets strongly even in the absence of heparin (heparin-independent platelet activation). Nevertheless, as seen with serum obtained from patients with otherwise typical heparin-induced thrombocytopenia (HIT), serum-induced platelet activation is inhibited at high heparin concentrations (10-100 IU mL-1 heparin). Furthermore, upon serial dilution, aHIT serum will usually show heparin-dependent platelet activation. Clinical syndromes associated with aHIT include: delayed-onset HIT, persisting HIT, spontaneous HIT syndrome, fondaparinux-associated HIT, heparin 'flush'-induced HIT, and severe HIT (platelet count of < 20 × 109  L-1 ) with associated disseminated intravascular coagulation (DIC). Recent studies have implicated anti-PF4 antibodies that are able to bridge two PF4 tetramers even in the absence of heparin, probably facilitated by non-heparin platelet-associated polyanions (chondroitin sulfate and polyphosphates); nascent PF4-aHIT-IgG complexes recruit additional heparin-dependent HIT antibodies, leading to the formation of large multimolecular immune complexes and marked platelet activation. aHIT can persist for several weeks, and serial fibrin, D-dimer, and fibrinogen levels, rather than the platelet count, may be helpful for monitoring treatment response. Although standard anticoagulant therapy for HIT ought to be effective, published experience indicates frequent failure of activated partial thromboplastin time (APTT)-adjusted anticoagulants (argatroban, bivalirudin), probably because of underdosing in the setting of HIT-associated DIC, known as 'APTT confounding'. Thus, non-APTT-adjusted therapies with drugs such as danaparoid and fondaparinux, or even direct oral anticoagulants, such as rivaroxaban or apixaban, are suggested therapies, especially for long-term management of persisting HIT. In addition, emerging data indicate that high-dose intravenous immunoglobulin can interrupt HIT antibody-induced platelet activation, leading to rapid platelet count recovery.

Pseudotumor in ceramic-on-metal total hip arthroplasty

The increasing demand for total hip arthroplasty (THA) in relatively young, high-demand patients has led to the use of hard-on-hard bearing surfaces. Adverse local tissue reaction/pseudotumor and elevated serum metal ion levels are commonly reported complications encountered in metal-on-metal THA, while audible articulation and rim fracture are reported in ceramic-on-ceramic THA. For this reason, ceramic-on-metal THA was implemented as an ideal hard-on-hard bearing combination. In this report, we describe a case of bilateral simultaneous ceramic-on-metal THA in a 69-year-old woman who presented 7 years postoperatively with unilateral hip pain associated with underlying pseudotumor and elevated serum cobalt and chromium ion levels. Pre-revision workup, intraoperative findings, and postoperative evaluation are included and suggest acetabular malposition as a potential source for complication.

Perioperative Pain Management in Hip and Knee Arthroplasty

Total hip and knee arthroplasty is associated with significant perioperative pain, which can adversely affect recovery by increasing risk of complications, length of stay, and cost. Historically, opioids were the mainstay of perioperative pain control. However, opioids are associated with significant downsides. Preemptive use of a multimodal pain management approach has become the standard of care to manage pain after hip and knee arthroplasty. Multimodal pain management uses oral medicines, peripheral nerve blocks, intra-articular injections, and other tools to reduce the need for opioids. Use of a multimodal approach promises to decrease complications, improve outcomes, and increase patient satisfaction after hip and knee arthroplasty.

Posterior hip instability relocation testing: a resident's case report

BACKGROUND

Micro-instability (non-radiographic clinical instability) continues to gain recognition as a problem at the hip. Although most research has been directed to anterior hip instability, posterior hip instability (PHI) has also garnered attention. PHI is under recognized, difficult to identify, and confused with other hip pathologies such as a simple sprain or strain. A novel clinical test is introduced that may have helped identify PHI in this patient. Additionally, a conservative rehabilitation approach emphasizing stabilization exercises is described.

CASE DESCRIPTION

A 29-year-old female presented with complaints of posterior lateral and anterior hip pain of 1.5 years duration. Upon initiating an aggressive stretching program, her pain worsened. Examination revealed limited and painful hip flexion, and positive anterior impingement testing for femoroacetabular impingement. Both tests were significantly less painful with more motion when retested with manual repositioning of the femoral head from posterior to anterior, referred to as posterior relocation testing. The patient was instructed to discontinue stretching. A stabilization plan was established including strengthening of the deep external rotators with trunk and lower quarter neuromuscular re-education.

OUTCOME

The patient completed 12 appointments over 2.5 months. At discharge, the patient reported improvements with pain and function. The Lower Extremity Functional Scale improved from 64/80 to 77/80 and Oswestry Disability Questionnaire improved from 8 to 0%.

DISCUSSION

PHI may have contributed to this patient's symptoms. The posterior relocation test may assist clinicians with identification of PHI, thus directing treatment toward stabilization and neuromuscular control rather than interventions designed to increase mobility.

LEVEL OF EVIDENCE

4.

Periarticular Liposomal Bupivacaine Injection Versus Intra-Articular Bupivacaine Infusion Catheter for Analgesia After Total Knee Arthroplasty: A Double-Blinded, Randomized Controlled Trial

BACKGROUND

Intra-articular bupivacaine hydrochloride (HCl) infusion catheters and periarticular injections of liposomal bupivacaine are often used as postoperative local anesthetics. The purpose of this study was to compare the efficacies of these local anesthetics following total knee arthroplasty.

METHODS

This study was a superiority trial with a randomized, controlled, double-blinded design. Patients were randomly assigned to either delivery of bupivacaine HCl by the ON-Q* Pain Relief System pump (n = 96) or by an injection of Exparel (liposomal bupivacaine) (n = 104). The primary outcome of this study was cumulative narcotic consumption on postoperative days 0 through 3. Narcotic consumption data were collected retrospectively from in-hospital records while patients were in the hospital. Following discharge, narcotic consumption data were gathered from patient surveys, as were secondary outcomes measures.

RESULTS

We did not identify greater narcotic use in the ON-Q* group compared with the Exparel group (p = 0.641). The mean difference between the groups was 0.5 morphine equivalent (95% confidence interval [CI] = -1.7 to +2.8), with the ON-Q* group consuming an average 10.4 morphine equivalents (95% CI = 8.7 to 12.0) compared with 10.9 (95% CI = 9.3 to 12.5) in the Exparel group. There were no significant differences between groups with regard to any of the secondary measures of pain with the exception of pain while walking and pain with physical therapy (p = 0.019 and p = 0.010, respectively), both of which showed an approximately 1-point difference in favor of the ON-Q* group on a visual analog scale (VAS). There were also no differences in the postoperative side effects, including nausea, constipation, or vomiting, or in the rates of study-related complications, patient satisfaction, or length of hospital stay.

CONCLUSIONS

Exparel did not have superior efficacy compared with the ON-Q* Pain Relief System as reflected by narcotic consumption, our primary outcome. There were small significant differences, in favor of the ON-Q* group, in 2 secondary measures of pain during activity, but these approximately 1-point VAS differences are unlikely to be clinically relevant. The choice of a local anesthetic modality should be based on a combination of safety, convenience, and cost considerations.

LEVEL OF EVIDENCE

Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Comparison of Pre-Revision Magnetic Resonance Imaging and Operative Findings in Mechanically Assisted Crevice Corrosion in Symptomatic Metal-on-Polyethylene Total Hip Arthroplasties

BACKGROUND

Failed total hip arthroplasty (THA) caused by mechanically assisted crevice corrosion (MACC) has serious consequences-notably, adverse local tissue reactions. Metal artifact reduction sequence (MARS) magnetic resonance imaging (MRI) has been used to evaluate failed THA for other reasons but has not been assessed for the analysis of cases of MACC in the setting of metal-on-polyethylene arthroplasties.

METHODS

We examined the correlation between preoperative MARS MRI and surgical findings in a cohort of 20 consecutive patients undergoing revision THA for symptomatic MACC without other associated orthopedic diagnoses. Surgical findings included soft tissue and bone evaluation, presence and location of fluid, abductor disruption, composite tissue damage grade, and prosthesis trunnion damage at the time of revision.

RESULTS

MARS MRI complex synovitis, thickened pseudocapsule, and extra-articular fluid extension each strongly correlated with both the soft-tissue damage grade and trunnion damage noted at surgery. Bone marrow edema was also found to strongly correlate with bone necrosis intraoperatively.

CONCLUSION

MARS MRI is an excellent diagnostic tool for evaluation of patients with elevated serum Co after metal-on-polyethylene THA. Patients with complex synovitis, a thick pseudocapsule, bone marrow edema, and extra-articular fluid should strongly consider revision surgery.

Ion release in ceramic bearings for total hip replacement: Results from an in vitro and an in vivo study

INTRODUCTION

Literature on the potential release of trace elements following implantation of Zirconia-platelet toughened alumina (ZPTA) ceramic components is scant. The present study therefore analysed the in vitro and in vivo potential release of ions from ZPTA bearings.

MATERIAL AND METHODS

An in vitro and in vivo study was conducted. The in vitro study compared leaching in bovine serum from two groups: ZPTA ceramic heads and Co-28Cr-6Mo alloy heads, both 28-mm diameter. A third group without implant served as reference group. An in vivo clinical study compared trace elements in the whole blood of patients with 36-mm diameter ZPTA ceramic-on-ceramic articulation after three and 12 months. A cohort of subjects without any prosthesis was used as control group. The release of ions was determined by high resolution-inductively coupled plasma-mass spectrometry.

RESULTS

In the in vitro experiment, significant differences (p ≤ 0.01) in trace element release for chromium, cobalt and molybdenum were found, with increased levels of ion release in the Co-28Cr-6Mo metal group. The very low detection limit for yttrium allowed detection of a small yttrium release from the ZPTA heads, which was not confirmed by the in vivo study. No significant difference between the groups was found for strontium, aluminium, and zirconium. In the in vivo study, no relevant differences in ion levels between the reference group without any implant and the study group were found at the three and 12-month follow-up.

CONCLUSION

This study supports that ZPTA ceramic articulation components are safe in terms of ion release, and may be an excellent alternative to bearings based on Co-28Cr-6Mo alloys.

Intraoperative load-sensing drives the level of constraint in primary total knee arthroplasty: Surgical technique and review of the literature

Total knee arthroplasty is a traditional surgical procedure aimed to restore function and relief pain in patients with severe knee osteoarthritis. Recently, many medial pivot knee systems were deigned to replicate the normal knee kinematic: a highly congruent medial compartment and a less conforming lateral tibial plateau characterize these devices. A slightly asymmetric soft tissue balancing is mandatory using medial pivot designs to obtain a correct and physiological knee biomechanics leading good outcomes and long survival rates. This article describes a new surgical technique using a modern third generation TKA design combined with wireless load-sensor tibial trials to improve the correct knee load balancing with a minimal conformity of the polyethylene insert. The use of wireless load-sensing tibial trials has several benefits: it is an intraoperative, objective and dynamic tool allowing surgeons to optimize in real time soft tissue balancing. The meaning of a "truly balanced knee" is still a controversial issue in the current literature.

Liposomal bupivacaine versus indwelling interscalene nerve block for postoperative pain control in shoulder arthroplasty: a prospective randomized controlled trial

BACKGROUND

Pain management strategies following shoulder arthroplasty vary significantly. Liposomal bupivacaine (LB) is an extended-release delivery of a phospholipid bilayer encapsulating bupivacaine that can result in drug delivery up to 72 hours. Prior studies in lower extremity surgery demonstrated efficacy of LB in comparison to a single-shot peripheral nerve block; however, no study has investigated LB in a total shoulder arthroplasty population. Therefore, this study compared LB vs. an indwelling interscalene nerve block (IINB).

METHODS

This is a prospective, randomized study of 83 consecutive shoulder arthroplasty patients; 36 patients received LB and a "bridge" of 30 mL of 0.5% bupivacaine, and 47 patients received an IINB. Postoperative visual analog scale pain levels, opiate consumption measured with oral morphine equivalents, length of hospital stay, and postoperative complications were recorded. Continuous variables were compared using an analysis of variance with significance set at P < .05.

RESULTS

Visual analog scale pain scores were statistically higher in the LB cohort immediately postoperatively in the postanesthesia care unit (7.25 vs. 1.91; P = .000) as well as for the remainder of postoperative day 0 (4.99 vs. 3.20; P = .005) but not for the remainder of admission. Opiate consumption was significantly higher among the LB cohort in the postanesthesia care unit (31.79 vs. 7.47; P = .000), on postoperative day 0 (32.64 vs. 15.04; P = .000), and for the total hospital admission (189.50 vs. 91.70, P = .000). Complication numbers and length of stay were not statistically different.

CONCLUSION

Use of an IINB provides superior pain management in the immediate postoperative setting as demonstrated by decreased narcotic medication consumption and lower subjective pain scores.

Vancomycin Prophylaxis for Total Joint Arthroplasty: Incorrectly Dosed and Has a Higher Rate of Periprosthetic Infection Than Cefazolin

BACKGROUND

In total joint arthroplasty (TJA), vancomycin is used as perioperative antibiotic prophylaxis in patients with penicillin allergy or in patients colonized with methicillin-resistant Staphylococcus aureus (MRSA). Although vancomycin dosing should be weight-based (15 mg/kg), not all surgeons are aware of this; a fixed 1-g dose is instead frequently administered.

QUESTIONS/PURPOSES

(1) Is there a difference in the risk of periprosthetic joint infection (PJI) in patients receiving vancomycin or cefazolin prophylaxis after primary TJA? (2) What proportion of patients is adequately dosed with vancomycin? (3) Compared with actual fixed dosing, does weight-based dosing result in a greater proportion of patients staying above the recommended 15-mg/L level at the beginning and end of surgery? (4) Are patients overdosed with vancomycin at greater risk of developing nephrotoxicity and acute kidney injury?

METHODS

A single-institution, retrospective study was performed on 1828 patients undergoing primary TJAs who received vancomycin prophylaxis between 2008 and 2014. During the same period, 5810 patients underwent primary TJA and received cefazolin monotherapy. A chart review was performed to obtain patient characteristics, antibiotic dose and timing of administration, and microbiology data. Adequate vancomycin dosing was defined as 15 mg/kg and within the 125-mg range. Vancomycin levels were calculated at the beginning and end of surgery using pharmacokinetic equations. Levels of 15 mg/L were considered adequate. Logistic regression, chi square tests, and analysis of variance were performed.

RESULTS

Among primary TJAs, patients receiving vancomycin had a higher rate of PJI (32 of 1828 [2%]) compared with patients receiving cefazolin prophylaxis (62 of 5810 [1%]; adjusted odds ratio, 1.587 [1.004-2.508]; p = 0.048). Ten percent of PJIs in the vancomycin underdosed group (two of 20) was caused by MRSA, and no patients with adequate dosing or overdosing of vancomycin developed PJI with MRSA. Of all procedures in which vancomycin monotherapy was used, 28% (518 of 1828) was adequately dosed according to weight-based dosage recommendations. Furthermore, 94% (1726 of 1828) of patients received a fixed 1-g dose of vancomycin, of whom 64% (1105 of 1726) were underdosed. All patients had vancomycin infusion initiated within 2 hours before incision. A weight-based protocol would have resulted in fewer patients having unacceptably low vancomycin levels (< 15 mg/L) compared with those with actual fixed dosing, both for the beginning of surgery at the time of incision (zero of 1828 [0%] versus 471 of 1828 [26%]; odds ratio, 0.001 [0.000-0.013]; p < 0.001) and at the end of surgery (33 of 1828 [2%] versus 746 of 1828 [41%]; odds ratio, 0.027 [0.019-0.038]; p < 0.001). Between the vancomycin dosage groups, there were no differences in the rate of nephrotoxicity (underdosed: 12 of 1130 [1%], adequately dosed: five of 518 [1%], overdosed: four of 180 [2%], p = 0.363) and acute kidney injury (underdosed: 28 of 1130 [2%], adequately dosed: 10 of 518 [2%], overdosed: six of 180 [3%], p = 0.561).

CONCLUSIONS

The majority of patients given vancomycin prophylaxis are underdosed according to the weight-based dosage recommendations, and MRSA did not occur in patients who were adequately dosed with vancomycin. Surgeons should thus ensure that their patients are adequately dosed with vancomycin using the recommendation of 15 mg/kg and that the dose of vancomycin is administered in a timely fashion. Furthermore, and based on the findings of this study, we have moved toward limiting the utilization of vancomycin prophylaxis for patients undergoing elective arthroplasty at our institution.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Infection burden in total hip and knee arthroplasties: an international registry-based perspective

Background

Infection remains a leading cause of failure of hip and knee replacements. Infection burden is the ratio of implants revised for infection to the total number of arthroplasties in a specific period, measuring the steady state of infection in a registry. We hypothesized infection burden would be similar among arthroplasty registries.

Methods

We evaluated publicly reported data from 6 arthroplasty registries (Australian Orthopaedic Association National Joint Replacement Registry [AOANJRR], New Zealand Joint Registry, Swedish Hip Arthroplasty Register, Swedish Knee Arthroplasty Register, National Joint Registry of England, Wales, Northern Ireland, and the Isle of Man, and the American Joint Replacement Registry) for revisions performed with an infection diagnosis over the last 6 years.

Results

The 2015 hip infection burden varied between registries from 0.76% (AOANJRR) to 1.24% (Swedish Hip Arthroplasty Register), and the unweighted overall average for hip infection burden was 0.97%. In 2012, 2013, and 2014, average hip infection burden held steady at 0.87%, 0.93%, and 0.94%, respectively, higher than the preceding 2 years. The 2015 knee infection burden varied from 0.88% (AOANJRR) to 1.28% (Swedish Knee Arthroplasty Register), and the unweighted average was 1.03%. In 2012, 2013, and 2014, knee infection burden was 1.04%, 1.11%, and 1.02%, respectively. These numbers were also higher than the preceding 2 years.

Conclusions

Infection burden may be one measure of the overall success in registry populations as well as monitoring the steady state of infection worldwide. Despite global efforts to reduce postoperative infection, infection burden has actually increased in the selected registries over time.

Differences in Patient-Reported Outcomes Between Unicompartmental and Total Knee Arthroplasties: A Propensity Score-Matched Analysis

BACKGROUND

The purpose of this study was to compare the patient-reported outcomes regarding joint awareness, function, and satisfaction after unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA).

METHODS

We identified all patients who underwent a UKA or TKA at our institution between September 2011 and March 2014, with a minimum follow-up of 2 years. Propensity score matching was performed for age, gender, body mass index, operation side, and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score. One hundred UKAs to 100 TKAs were matched. Each knee was evaluated according to the WOMAC score, Forgotten Joint Score (FJS), High Flexion Knee Score (HFKS) and patient's satisfaction at postoperative 2 years.

RESULTS

There was no significant difference in WOMAC score at postoperative 2 years between UKA and TKA groups. However, the FJS of the UKA group was significantly higher than that of the TKA group (67.3 ± 19.8 and 60.6 ± 16.6, respectively; P = .011). The HFKS was also significantly higher in the UKA group compared with the TKA group (34.4 ± 6.4 and 31.3 ± 5.2, respectively; P < .001). Eighty-six percent of all patients who underwent UKA were satisfied compared with 71% of those who underwent TKA (P = .027).

CONCLUSION

Patients who underwent UKA had higher FJS, HFKS, and satisfaction rate when compared with patients who underwent TKA, indicating that UKA facilitated less knee awareness and better function and satisfaction than TKA.

Supramacroparticulate PE in 6 different joint endoprostheses localisations: An indicator for PE damage?

In the histopathological particle algorithm polyethylene (PE) particles with maximum lengths of more than 100μm - called PE supramacroparticles - are identified exclusively for knee joint and hip prostheses. However, a definitive characterisation, detection in all joint localisations and a causal clarification of the pathogenesis are lacking. In this study a total of 175 SLIM (synovial-like interface membrane) cases with PE supramacroparticles of knee joint prostheses (n=89), hip joint prostheses (n=44), ankle joint prostheses (n=36) and prostheses in three localisations of the upper extremities (n=6) were systematically investigated. The arithmetic mean of the particle length varied greatly within the prosthesis types. This had a significant positive correlation with the prosthesis lifetime and negative correlation with the date of implantation. It can be concluded that both the lifetime and the time of implantation have an influence on the particle length. The prostheses with supramacroparticulate damage moreover showed a clearly reduced survival rate compared with other data published on the prosthesis lifetime. The material wear therefore could not be attributed solely to the usual fatigue factors. Since loosening of the prostheses, decentring of the PE components or damage to the PE inlay existed in all cases, mechanical dysloading seems to be the most probable cause of PE supramacroparticle genesis. Due to the striking length and for demarcation from PE macroparticles, the term supramacroparticulate PE is proposed for a length of more than 100μm. In the extended histopathological particle algorithm supramacroparticulate PE has been included in the macroparticles category and should be taken into account and interpreted causally in histopathological diagnostics of joint prosthesis failure.