Economic burden of revision hip and knee arthroplasty in Medicare enrollees

Reconstruction options for acetabular revision

This article summarizes reconstruction options available for acetabular revision following total hip arthroplasty. A thoughtful methodology to the evaluation and treatment of patients with implant failure after joint replacement is essential to guarantee accurate diagnoses, appropriate triage to reconstruction options, and optimal clinical outcomes. In the majority of patients who undergo acetabular revision, factors such as bone loss and pelvic discontinuity provide a challenge in the selection and implementation of the proper reconstruction option. With advanced evaluation algorithms, imaging techniques, and implant designs, techniques have evolved to rebuild the compromised acetabulum at the time of revision surgery. However, clinical outcomes data for these techniques continue to lag behind the exponential increase in revision hip arthroplasty cases predicted to occur over the next several years. We encourage those involved in the treatment of patients undergoing hip replacement surgery to participate in well-designed clinical studies to enhance evidence-based knowledge regarding revision acetabular reconstruction options.

A financial analysis of revision hip arthroplasty: the economic burden in relation to the national tariff

Revision arthroplasty of the hip is expensive owing to the increased cost of pre-operative investigations, surgical implants and instrumentation, protracted hospital stay and drugs. We compared the costs of performing this surgery for aseptic loosening, dislocation, deep infection and peri-prosthetic fracture. Clinical, demographic and economic data were obtained for 305 consecutive revision total hip replacements in 286 patients performed at a tertiary referral centre between 1999 and 2008. The mean total costs for revision surgery in aseptic cases (n = 194) were £11 897 (sd 4629), for septic revision (n = 76) £21 937 (sd 10 965), for peri-prosthetic fracture (n = 24) £18 185 (sd 9124), and for dislocation (n = 11) £10 893 (sd 5476). Surgery for deep infection and peri-prosthetic fracture was associated with longer operating times, increased blood loss and an increase in complications compared to revisions for aseptic loosening. Total inpatient stay was also significantly longer on average (p < 0.001). Financial costs vary significantly by indication, which is not reflected in current National Health Service tariffs.

Classification and management of the unstable total hip arthroplasty

Seventy-five total hip arthroplasty revisions for instability were classified into 6 primary etiologies: I, acetabular component malposition; II, femoral component malposition; III, abductor deficiency; IV, impingement; V, late wear; or VI, unresolved etiology. The most common etiologies were cup malposition (type I; 33%) and abductor deficiency (type III; 36%). At a mean of 35.3 months, 11 redislocations occurred (14.6%). Acetabular revisions were protective against redislocation (P < .015). The number of previous operations (P = .0379) and previously failed constrained liners (P < .02) were risk factors for failure. Tripolar constrained liners demonstrated improved survivorship vs locking ring types (P < .02); cemented constrained liners failed more often than modular constrained liners (P < .0018). The highest risk of failure was in patients with abductor insufficiency with revisions for other etiologies having a success rate of 90%.

Thromboprophylaxis, bleeding and post-operative prosthetic joint infection in total hip and knee arthroplasty: a comprehensive literature review

INTRODUCTION

Concerns regarding risk versus benefit, that is, the possible impact of surgical-site bleeding on post-operative joint infections, have contributed to a continuing debate over recommendations for venous thromboembolism (VTE) prophylaxis in post-surgical orthopedic patients undergoing total hip and knee arthroplasty (THA/TKA).

AREAS COVERED

A comprehensive literature search using MEDLINE covering the period 2004-2009 was conducted, and published studies that focused on THA and TKA and contained data applicable to thromboprophylaxis, post-surgical wound infection and bleeding are reviewed in this paper. The search strategy included various combinations of terms related to lower limb joint arthroplasty, anticoagulant drugs, post-operative bleeding and prosthetic joint infection (wound infection). Methodological constraints included failure in some studies to define an infection, variations among the studies in the definitions of bleeding and differences in the follow-up time for capturing infection and bleeding events. Despite this, this comprehensive review identified observational, 'real-world' data that can contribute in important ways to the existing evidence base.

EXPERT OPINION

There are insufficient data to either confirm or refute the hypothesis that post-operative bleeding is a mediating pathophysiologic factor linking pharmacologic VTE prophylaxis to an increased risk for wound infection. Studies specifically designed to examine the interrelationship between thromboprophylaxis, bleeding and wound infections following THA/TKA are warranted.

Titanium-copper-nitride coated spacers for two-stage revision of infected total hip endoprostheses

Within the first two years after total hip arthroplasty implant-associated infection has become the second most common reason for a revision surgery. Two-stage implant exchange is frequently conducted using temporary spacers made of antibiotic-loaded cement in order to prevent a bacterial colonization on the spacer. Avoiding several disadvantages of cement spacers, a conventional hemi-endoprosthesis was equipped with a copper-containing implant coating for inhibition of bacterial biofilms. In the present paper details of this novel treatment concept are presented including a case report.

Two-stage revision of implant-associated infections after total hip and knee arthroplasty

Septic loosening of total hip and knee endoprostheses gains an increasing proportion of revision arthroplasties. Operative revisions of infected endoprostheses are mentally and physically wearing for the patient, challenging for the surgeon and a significant economic burden for healthcare systems. In cases of early infection within the first three weeks after implantation a one-stage revision with leaving the implant in place is widely accepted. The recommendations for the management of late infections vary by far. One-stage revisions as well as two-stage or multiple revision schedules have been reported to be successful in over 90% of all cases for certain patient collectives. But implant associated infection still remains a severe complication. Moreover, the management of late endoprosthetic infection requires specific logistics, sufficient and standardized treatment protocol, qualified manpower as well as an efficient quality management. With regard to the literature and experience of specialized orthopaedic surgeons from several university and regional hospitals we modified a commonly used treatment protocol for two-stage revision of infected total hip and knee endoprostheses. In addition to the achievement of maximum survival rate of the revision implants an optimisation of the functional outcome of the affected artificial joint is aimed for.

Functional and Emotional Results Differ After Aseptic vs Septic Revision Hip Arthroplasty

BACKGROUND

It is widely believed that a deep implant infection leads to poor functional and emotional outcomes following total hip arthroplasty.

QUESTIONS/PURPOSE

The purpose of this retrospective comparative review was to determine if patients who undergo two-stage, septic revision hip arthroplasty will have decreased emotional and general health scores, in addition to decreased function, compared to the aseptic revision group.

PATIENTS AND METHODS

One hundred forty-five of 195 patients who underwent aseptic total hip revision for aseptic loosening (mean follow-up = 61 months) and 45 of 73 patients who underwent two-stage, septic revision hip arthroplasty (mean follow-up = 48 months) met the inclusion criteria and had a technically successful outcome. All patients were retrospectively evaluated using Harris Hip Scores (HHS), ad hoc questions, and the SF-36 Health Survey.

RESULTS

The average HHS were 73.2 ± 20.5 (aseptic) and 57.4 ± 20.6 (septic). Significant differences in the SF-36 Health Survey were found between the two groups in: physical functioning (p = 0.026) and role limitations due to physical health (p = 0.004). No significant difference in SF-36 scores was seen in: Energy/Fatigue, General Health Perception, Personal or Emotional Problems, Role Limitations due to Emotional Well Being, Social Functioning, and Bodily Pain.

CONCLUSIONS

Two-stage, septic revision produces a poor functional outcome compared to aseptic revision; however, the overall impact of a septic revision emotionally and socially was not significantly different than patients undergoing aseptic revision.

In vitro biological and tribological properties of transparent magnesium aluminate (Spinel) and aluminum oxynitride (ALON®)

The purpose of this first generation investigation is to evaluate the in vitro cytotoxicity, cell-materials interactions and tribological performance of Spinel and ALON® transparent ceramics for potential wear resistant load bearing implant applications. Besides their non-toxicity, the high surface energy of these ceramics significantly enhanced in vitro cell-materials interactions compared to bioinert commercially pure Ti as control. These transparent ceramics with high hardness in the range of 1334 and 1543 HV showed in vitro wear rate of the order of 10⁻⁶ mm³ Nm⁻¹ against Al₂O₃ ball at a normal load of 20 N.

Prevalence and projections of total shoulder and elbow arthroplasty in the United States to 2015

HYPOTHESIS

This study examined national trends and projections of procedure volumes and prevalence rates for shoulder and elbow arthroplasty in the United States (U.S.). This study hypothesized that the growth in demand for upper extremity arthroplasty will be greater than the growth in demand for hip and knee arthroplasty and that demand for these procedures will continue to grow in the immediate future.

MATERIALS AND METHODS

The Nationwide Inpatient Sample (1993-2007) was used with U.S. Census data to quantify primary arthroplasty rates as a function of age, race, census region, and gender. Poisson regression was used to evaluate procedure rates and determine year-to-year trends in primary and revision arthroplasty. Projections were derived based on historical procedure rates combined with population projections from 2008 to 2015.

RESULTS

Procedure volumes and rates increased at annual rates of 6% to 13% from 1993 to 2007. Compared with 2007 levels, projected procedures were predicted to further increase by between 192% and 322% by 2015. The revision burden increased from approximately 4.5% to 7%. During the period studied, the hospital length of stay decreased by approximately 2 days for total and hemishoulder procedures. Charges, in 2007 Consumer Price Index-adjusted dollars, increased for all 4 procedural types at annual rates of $900 to $1700.

CONCLUSION

The growth rates of upper extremity arthroplasty were comparable to or higher than rates for total hip and knee procedures. Of particular concern was the increased revision burden. The rising number of arthroplasty procedures combined with increased charges has the potential to place a financial strain on the health care system.

Risk of subsequent revision after primary and revision total joint arthroplasty

BACKGROUND

Revision is technically more demanding than primary total joint arthroplasty (TJA) and requires more extensive use of resources. Understanding the relative risk of rerevision and risk factors can help identify patients at high risk who may require closer postsurgical care.

OBJECTIVES/PURPOSES

We therefore evaluated the risk of subsequent revision after primary and revision TJA in the elderly (65 years or older) patient population and identified corresponding patient risk factors.

PATIENTS AND METHODS

Using the 5% Medicare claims data set (1997-2006), we identified a total of 35,746 patients undergoing primary THA and 72,913 undergoing primary TKA; of these, 1205 who had THAs and 1599 who had TKAs underwent initial revision surgery. The rerevision rate after primary and revision TJAs was analyzed by the Kaplan-Meier method. The relative risk of revision surgery for primary and revision TJAs was compared using hazard ratio analysis.

RESULTS

The 5-year survival probabilities were 95.9%, 97.2%, 81.0%, and 87.4% for primary THA and TKA and revision THA and TKA, respectively. Patients with revision arthroplasty were five to six times more likely to undergo rerevision (adjusted relative risk, 4.89 for THA; 5.71 for TKA) compared with patients with primary arthroplasty. Age and comorbidities were associated with initial revision after primary THA and TKA.

CONCLUSIONS

Patients should undergo stringent preoperative screening for preexisting health conditions and careful patient management and followup postoperatively so as to minimize the risk of an initial revision, which otherwise could lead to a significantly greater likelihood of subsequent rerevisions.

Revision hip arthroplasty: infection is the most common cause of failure

BACKGROUND

Revision total hip arthroplasty (THA), although relieving pain and restoring function, fails in some patients. In contrast to failures in primary THA, the frequency of the causes of failure in revision THA has been less well established.

QUESTIONS/PURPOSES

We therefore determined the rate of each failure mode and the survivorship of revision THAs.

METHODS

We retrospectively reviewed the charts of 1366 revision THAs performed between 2000 and 2007. There were 609 (44.5%) men and 757 (55.5%) women with a mean age of 66 years. The indications for the revision surgery were mainly aseptic loosening (51%), instability (15%), wear (14%), and infection (8%). The minimum followup was 1 day (mean, 5.5 years; range, 1 day to 9 years).

RESULTS

Two hundred fifty-six of the revisions (18.7%) failed with an average time to failure of 16.6 months (range, 1 day to 7.5 years). Among 256 failed hips, infection was the most common cause of failure (30.2%) followed by instability (25.1%) and aseptic loosening (19.4%). At 5 years, the survivorships of septic and aseptic groups were 67% and 84.8%, respectively. Revision for infection or instability appears to have a considerably lower survivorship when compared to revision for aseptic causes.

CONCLUSIONS

The lower survivorship of revision for infection or instability highlights the importance of implementing better preventative methods that can minimize the impact of these two major causes of failure.

LEVEL OF EVIDENCE

Level III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Variation in outcome measures in hip and knee arthroplasty clinical trials: a proposed approach to achieving consensus

OMERACT began work over a decade ago on a consensus effort to identify optimal outcome measures for knee and hip osteoarthritis clinical trials. Recent evidence indicates extensive variation in outcome measures used in clinical trials of knee and hip arthroplasty published since 2000. This heterogeneity leads to confusion, not only for conducting systematic reviews but also for applying evidence to clinical practice. Given the extensive psychometric research conducted in the past 2 decades, the timing seems ideal to design and implement a study to develop consensus on optimal outcome measures for hip and knee arthroplasty trials. We describe a Delphi survey design and an approach for synthesizing the extensive psychometric literature on the outcome measures used in hip and knee arthroplasty trials. Plans for dissemination of the findings are also discussed. This proposed study could have an important influence on the design and reporting of future randomized trials of knee arthroplasty.

Accidental falls involving medical implant re-operation

Implantation of medical devices is becoming more prevalent, and as a result, a greater number of patients who fall accidentally are expected to have a medical implant. The Nationwide Inpatient Sample (NIS) was used to evaluate hospital admissions following accidental falls involving re-operation of existing medical implants (hip, knee, spine, and fracture fixation) from 1990 to 2005. From 1990 to 2005, hospitalisations due to accidental falls on level surfaces increased by 306%, and hospitalisations due to falls from stairs increased by 310%. Falls involving orthopaedic revision surgery (re-operation) are relatively rare, but the incidence has increased by approximately 35%. Hospital stays after falls on level surfaces involving re-operation were 1.0 day (median) longer and cost 50% (median) more than those that did not involve re-operation in 2005. After staircase falls, hospital stays for patients undergoing re-operations were 2.0 days (median) longer and cost 108% (median) more. The greater hospital costs and hospital stay for patients needing re-operations indicate that additional medical treatment was required.

Patient, hospital, and procedure characteristics influencing total hip and knee arthroplasty procedure duration

Procedure duration is a potential risk factor for total hip arthroplasty (THA) and total knee arthroplasty (TKA) complications. Presently, limited information regarding THA and TKA procedure duration in the United States is available. Patient, hospital, and procedure characteristics that influence procedure duration were determined using Medicare claims data (1997-2004). The median procedure duration decreased from 171.0 to 142.5 minutes for THA and 160.5 to 138.0 minutes for TKA between 1997 and 2004. The median procedure duration decreased as hospital and surgeon volume for both primary THA and TKA increased. Younger patients, males, patients not diagnosed with OA, and patients with more comorbidities generally underwent longer THA and TKA procedures. Larger hospitals (> or =500 beds) were associated with longer THA and TKA procedures, and nonprofit hospitals were associated with shorter procedures. This analysis provides baseline data for future investigation of the influence of procedure duration on total joint arthroplasty outcomes from a national perspective.

A multivariate statistical ranking of clinical and gait measures before and after total knee replacement

The purpose of this study was to assess the use of a multivariate statistical method to rank clinical and gait variables, thus describing a ranking of patient dysfunction prior to and following total knee replacement (TKR) surgery. Twenty end-stage knee osteoarthritis (KOA) subjects scheduled for TKR and 20 healthy controls performed level walking and stair ascent twice: pre- (P1) and 6 months post-surgery (P2). Clinical and gait measures were entered into a principle component analysis (PCA) to determine orthogonal principle components (PCs). The PCs were entered into a discriminant function analysis to determine the best predictors of group membership. The PCA extracted three PCs for both the P1 and P2 data sets. Three orthogonal dimensions were formed: "knee dysfunction", "gait dysfunction", and "stair ascent dysfunction". For P1 the "knee dysfunction" dimension composed of both subjective and objective measures, best discriminated between end-stage knee osteoarthritis patients and controls. For P2, the "stair ascent dysfunction" dimension best discriminated between 6 months post-TKR patients and controls. The results of this study suggest that a multivariate statistical method provides a clinically relevant ranking of patient dysfunction prior to and following TKR. This ranking of dysfunction could serve to identify rehabilitation priorities.

Primary and revision arthroplasty surgery caseloads in the United States from 1990 to 2004

We analyzed the temporal changes in the caseload of primary and revision hip and knee arthroplasty surgeons in the United States between 1990 and 2004. The Nationwide Inpatient Sample was used to identify arthroplasty procedures and the surgeons who performed them. Annual caseloads were analyzed for each procedure; 47% +/- 2% and 39% +/- 2% of hip and knee surgeons performed revisions nationwide. Average revision caseloads increased slightly over time at a rate of 1.2 and 1.4 cases per surgeon per decade for total hip arthroplasty (THA) and total knee arthroplasty (TKA), respectively. The caseload of primary THA and TKA increased by 1.4 and 1.7 cases per surgeon per decade. The caseload for the top 5% of primary THA and TKA surgeons increased from 25 to 45 and 33 to 86, respectively, during this period compared with the median caseload, which increased from 4 to 5 (hip) and 5 to 10 (knee). The revision caseload of surgeons has increased over time, particularly for surgeons with the highest caseloads.

The epidemiology of revision total hip arthroplasty in the United States

BACKGROUND

Understanding the causes of failure and the types of revision total hip arthroplasty performed is essential for guiding research, implant design, clinical decision-making, and health-care policy. The purpose of the present study was to evaluate the mechanisms of failure and the types of revision total hip arthroplasty procedures performed in the United States with use of newly implemented ICD-9-CM (International Classification of Diseases, Ninth Revision, Clinical Modification) diagnosis and procedure codes related specifically to revision total hip arthroplasty in a large, nationally representative population.

METHODS

The Healthcare Cost and Utilization Project Nationwide Inpatient Sample database was used to analyze clinical, demographic, and economic data from 51,345 revision total hip arthroplasty procedures performed between October 1, 2005, and December 31, 2006. The prevalence of revision procedures was calculated for population subgroups in the United States that were stratified according to age, sex, diagnosis, census region, primary payer class, and type of hospital. The cause of failure, the average length of stay, and total charges were also determined for each type of revision arthroplasty procedure.

RESULTS

The most common type of revision total hip arthroplasty procedure performed was all-component revision (41.1%), and the most common causes of revision were instability/dislocation (22.5%), mechanical loosening (19.7%), and infection (14.8%). Revision total hip arthroplasty procedures were most commonly performed in large, urban, nonteaching hospitals for Medicare patients seventy-five to eighty-four years of age. The average length of hospital stay for all types of revision arthroplasties was 6.2 days, and the average total charges were $54,553. However, the average length of stay, average charges, and procedure frequencies varied considerably according to census region, hospital type, and type of revision total hip arthroplasty procedure performed.

CONCLUSIONS

Hip instability and mechanical loosening are the most common indications for revision total hip arthroplasty in the United States. As further experience is gained with the new diagnosis and procedure codes specifically related to revision total hip arthroplasty, this information will be valuable in directing future research, implant design, and clinical decision-making.

A comprehensive joint replacement program for total knee arthroplasty: a descriptive study

Background

Total knee arthroplasty (TKA) is a commonly performed surgical procedure in the US. It is important to have a comprehensive inpatient TKA program which maximizes outcomes while minimizing adverse events. The purpose of this study was to describe a TKA program – the Joint Replacement Program (JRP) – and report post-surgical outcomes.

Methods

74 candidates for a primary TKA were enrolled in the JRP. The JRP was designed to minimize complications and optimize patient-centered outcomes using a team approach including the patient, patient's family, and a multidisciplinary team of health professionals. The JRP consisted of a pre-operative class, standard pathways for medical care, comprehensive peri-operative pain management, aggressive physical therapy (PT), and proactive discharge planning. Measures included functional tests, knee range of motion (ROM), and medical record abstraction of patient demographics, length of stay, discharge disposition, and complications over a 6-month follow-up period.

Results

All patients achieved medical criteria for hospital discharge. The patients achieved the knee flexion ROM goal of 90° (91.7 ± 5.4°), but did not achieve the knee extension ROM goal of 0° (2.4 ± 2.6°). The length of hospital stay was two days for 53% of the patients, with 39% and 7% discharged in three and four days, respectively. All but three patients were discharged home with functional independence. 68% of these received outpatient physical therapy compared with 32% who received home physical therapy immediately after discharge. Two patients (< 3%) had medical complications during the inpatient hospital stay, and 9 patients (12%) had complications during the 6-month follow-up period.

Conclusion

The comprehensive JRP for TKA was associated with satisfactory clinical outcomes, short lengths of stay, a high percentage of patients discharged home with outpatient PT, and minimal complications. This JRP may represent an efficient, effective and safe protocol for providing care after a TKA.

Diagnosis of infected total knee: findings of a multicenter database

Although total knee arthroplasty (TKA) is an effective and successful procedure, the outcome is occasionally compromised by complications including periprosthetic joint infection (PJI). Accurate and early diagnosis is the first step in effectively managing patients with PJI. At the present time, diagnosis remains dependent on clinical judgment and reliance on standard clinical tests including serologic tests, analysis of aspirated joint fluid, and interpretation of intraoperative tissue and fluid test results. Although reports regarding sensitivity and specificity of all diagnostic tests in the literature are abundant, the interpretation of the available data has been hampered by the low sample size of these studies. In view of the scope of this important problem and the limitations of previous reports, a large database was assembled of all revision TKA performed at three academic referral centers in order to determine the current status of diagnosis of the infected TKA utilizing commonly available tests. Intraoperative cultures should not be used as a gold standard for PJI owing to high percentages of false-negative and false-positive cases. When combined with clinical judgment, total white cell count and percentage of neutrophils in the synovial fluid more accurately reflects PJI and when combined with hematologic exams safely excludes or confirms infection.

LEVEL OF EVIDENCE

Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

Current state and future of joint replacements in the hip and knee

Joint replacements of the hip and knee are among the most clinically successful operations. According to figures compiled by the American Academy of Orthopaedic Surgeons, the number of primary total hip replacements performed in the USA was 220,000 in 2003. This was 38% more than in 1996 and this number is expected to rise to 572,000 (plus another 97,000 revisions) by 2030. The number of primary total knee replacements performed in 2003 was approximately 418,000 and is expected to rise exponentially with the increasing numbers of baby boomers and the aging population. Current research focuses not only on extending implant longevity, but also on improving function to meet the increased demands of today's patients, who are likely to be younger and more active than their predecessors two decades ago. Potential advancements in arthroplasty surgery include new, more wear-resistant bearing surfaces, porous metals to enhance osseointegration and replace lost bone stock, a clearer understanding of the biological processes associated with periprosthetic osteolysis, minimally invasive surgery and computer assisted surgery. Long-term studies are needed to establish the efficacy of these new technologies.

Impact of hospital volume on the economic value of computer navigation for total knee replacement

BACKGROUND

An aim of the use of computer navigation is to reduce rates of revisions of total knee replacements by improving the alignment achieved at the surgery. However, the decision to adopt this technology may be difficult for some centers, especially low-volume centers, where the cost of purchasing this equipment may be high. The purpose of this study was to examine the impact of hospital volume on the cost-effectiveness of this new technology in order to determine its feasibility and the level of evidence that should be sought prior to its adoption.

METHODS

A Markov decision model was used to evaluate the impact of hospital volume on the cost-effectiveness of computer-assisted knee arthroplasty in a theoretical cohort of sixty-five-year-old patients with end-stage arthritis of the knee to coincide with the peak incidence of knee arthroplasty in the United States.

RESULTS

Computer-assisted surgery becomes less cost-effective as the annual hospital volume decreases, as the cost of the navigation increases, and as the impact on revision rates decreases. Centers at which 250, 150, and twenty-five computer-navigated total knee arthroplasties are performed per year will require a reduction of the annual revision rate of 2%, 2.5%, and 13%, respectively, per year over a twenty-year period for computer navigation to be cost-effective.

CONCLUSIONS

Computer navigation is less likely to be a cost-effective investment in health-care improvement in centers with a low volume of joint replacements, where its benefit is most likely to be realized. However, it may be a cost-effective technology for centers with a higher volume of joint replacements, where the decrease in the rate of knee revision needed to make the investment cost-effective is modest, if improvements in revision rates with the use of this technology can be realized.

Effect of femoral head size and abductors on dislocation after revision THA

Dislocation is a common complication after revision total hip arthroplasty, particularly if the abductor mechanism is deficient. Use of a large femoral head may reduce the incidence of dislocation. However, it is not clear if the large femoral head is effective in controlling dislocation when the abductor mechanism is deficient. We separated 230 patients who underwent revision total hip arthroplasty into four groups: Group 1 (159 patients) had an intact abductor mechanism and a 28-mm femoral head, Group 2 (20 patients) had an absent abductor mechanism (trochanteric nonunion or complete segmental proximal femoral bone loss) and a 28-mm femoral head, Group 3 (42 patients) had an intact abductor mechanism and a 36-mm femoral head, and Group 4 (nine patients) had an absent abductor mechanism and a 36-mm femoral head. The minimum followup was 6 months (mean, 27 months; range, 6 months to 7 years). A 36-mm head was associated with a lower dislocation rate after revision total hip arthroplasty than a 28-mm head with an intact abductor mechanism; the rate of dislocation was 12.7% for Group 1, 40.0% for Group 2, 0% for Group 3, and 33.3% for Group 4. However, the use of a large-diameter head does not reduce the rate of dislocation if the abductor mechanism is absent.

Viscosupplementation with hyaluronans for osteoarthritis of the knee: clinical efficacy and economic implications

Treatment with intra-articular viscosupplementation with hyaluronan (hyaluronic acid) and its derivatives is an important component of the management of osteoarthritis (OA) of the knee. Several intra-articular hyaluronan formulations are now available that vary in their physical properties, duration of effect and treatment schedules. Although aspects regarding their mechanism of action are not completely understood, numerous clinical trials, systematic reviews and meta-analyses have confirmed the efficacy of intra-articular hyaluronan therapies for relieving OA-related pain and improving joint function. Data indicate that intra-articular hyaluronan preparations provide OA pain relief that is comparable to or greater than that observed with conventional treatment, NSAID medications, intra-articular corticosteroids, arthroscopic lavage, physical therapy and exercise. Other studies indicate that multiple courses of hyaluronan are effective. Intra-articular hyaluronan formulations are well tolerated and are associated with a low incidence of adverse effects, usually localised to the injected joint. Local adverse events associated with intra-articular hyaluronan products are typically mild to moderate in severity, benign and transient, although their aetiology is unknown. The cost effectiveness of intra-articular hyaluronan has been demonstrated, but only in a limited number of studies. Cost savings with intra-articular hyaluronan can also be realised with reduction of NSAID medication use and the possibility of delaying total knee replacement, which can reduce the need for costly revision procedures. Because different intra-articular hyaluronan formulations require different numbers of injections and office visits, are associated with variable treatment costs, and provide varying degrees of efficacy, not all intra-articular hyaluronan formulations may be equally cost effective over time.

Selfprotective smart orthopedic implants

In this review, we discuss current advances leading to an exciting change in implant design for orthopedic surgery. The initial biomaterial approaches in implant design are being replaced by cellular-molecular interactions and nanoscale chemistry. New designs address implant complications, particularly loosening and infection. For infection, local delivery systems are an important first step in the process. Selfprotective 'smart' devices are an example of the next generation of orthopedic implants. If proven to be effective, antibiotics or other active molecules that are tethered to the implant surface through a permanent covalent bond and tethering of antibiotics or other biofactors are likely to transform the practice of orthopedic surgery and other medical specialties. This new technology has the potential to eliminate periprosthetic infection, a major and growing problem in orthopedic practice.

2006 Otto Aufranc Award Paper: significance of in vivo degradation for polyethylene in total hip arthroplasty

Our research group developed an implant retrieval program to study in vivo degradation of polyethylene. We now have evidence to support our hypothesis that degradation of radiation-sterilized polyethylene occurs in the body for not only historical gamma air sterilized liners, but also for conventional gamma inert sterilized (ArCom) and annealed highly crosslinked polyethylene (Crossfire) liners as well. Our research has also led to the discovery that the most severe manifestations of in vivo oxidation typically occur in regions of the liner experiencing minimal wear, such as the rim of the component, where the body fluids (containing oxidizing species) have access to the polyethylene. Our data from historical, ArCom, and Crossfire retrievals all point to a similar scenario in which the femoral head limits the in vivo oxidation of polyethylene at the bearing surface. Consequently, provided rim impingement does not occur, and the polyethylene locking mechanisms remain relatively isolated from oxidizing fluid, in vivo oxidation does not seem to be clinically important in the first 10 years of implantation for conventional gamma sterilized polyethylene. We conclude that in vivo degradation should be included among the list of potential long-term failure modes for modular polyethylene components for total hip arthroplasty.