OBJECTIVE:The purpose of this study was to examine the relationship between obesity and patient-administered outcome measures after total joint arthroplasty.RESEARCH METHODS AND PROCEDURES:A voluntary questionnaire-based registry contained 592 primary total hip arthroplasty patients and 1011 primary total knee arthroplasty patients with preoperative and 1-year data. Using logistic regression, the relationships between body mass index and the several outcome measures, including Short Form-36 and Western Ontario and McMaster Universities Osteoarthritis Index, were examined.RESULTS:There was no difference between obese and non-obese patients regarding satisfaction, decision to repeat surgery, and Delta physical component summary, Delta mental component summary, and Delta Western Ontario and McMaster Universities Osteoarthritis Index scores (p > 0.05 for all). Body mass index was associated with an increased risk of having difficulty descending or ascending stairs at 1 year (odds ratio, 1.2 to 1.3).DISCUSSION:Obese patients enjoy as much improvement and satisfaction as other patients from total joint arthroplasty.

A survey was conducted of the entire membership of the American Association of Hip and Knee Surgeons to determine their experience with total hip arthroplasty (THA) device-related failures. Forty-seven percent of the membership reviewed their preceding 5-year clinical experience and returned the survey instrument. The aggregate 5-year volume encompassed experience with more than 60,000 hip arthroplastics. The median 5-year experience per respondent was 200 metal-backed sockets and 214 metal stems. The frequency distribution of the number of hip arthrosplatics per respondent was skewed to the right, with fewer surgeons reporting the higher volumes of arthroplasties. In aggregate, 60,115 of the acetabular components used were metal backed. Nonmetal acetabular component usage totaled 3,219. Complete polyethylene failure was defined as fracture or complete wear through of the polyethylene portion of the component. Complete polyethyene failure was seen in 172 metal-backed sockets (29/10,000). Seventy-seven all-polyethylene sockets had complete polyethyelene failure (239/10,000). A total of 87 THAs were revised for modular acetabular dissociations for a dissociation rate of 15/10,000. In aggregate, 64,483 metal-stemmed components were used. Femoral stem fractures occurred in 172 for a rate of 27/10,000. A total of 56,965 metallic femoral components were reported as being modular. Dissociation between the femoral head and neck was uncommonly seen (3/10,000). Use of cereamic femoral heads was low (5,023); however, a total of 11 ceramic head fractures were revised in the 5-year period for a failure rate of 22/10,000. The risks of catastrophic prosthetic THA failure are low but vary according to hip component and the manufacturer of the part. On the basis of this survey, polyethylene is the weakest link in THA prosthetic design. Manufacturers' efforts should continue to address factors leading to polyethylene failure, in addition to the other factors that result in premature prosthetic hip failures. Surgeons and patients may use this information to assist in the selection of quality manufacturers are preferred vendors. Because of the low frequency of device failures, the large simple survey methodology can provide failure rate estimates that cannot be reliably determined by individual orthopaedists or institutions working in isolation.

In summary, the immune system provides two specific types of responses: humoral or B-cell immunity, and T-cell-mediated immunity to a specific stimulus. In response to a noxious stimulus, the inflammatory response utilizes some common cellular elements of the immune system and is not immunologically mediated. The antigen provides the foundation for all specific immune reactions. These molecules are unique and form the basis for transplantation immunology—the human MHC, or major histocompatibility complex. Genes code for molecules on the surface of cells which identify an individual by species-specific and individual-specific markers. Transplanted biologic materials may have cells, but they also have matrix or collagen components that are immunogenic. To determine and characterize these immune responses, a number of diagnostic methods are available. These range from routing H&E histological studies for cell population to sophisticated mitogenic stimulation assays for determining antigenicity and patient sensitization. Certainly immunobiology will be increasingly important as the use of biologic material and transplantation become more widespread.

A neutral metal protease has been identified which cleaves native type V collagen under conditions where pepsinized type IV collagen or the interstitial collagens are not significantly degraded. The enzyme is secreted into the media of cultured M50-76 reticulum cell sarcoma (malignant macrophages) and leiomyosarcoma tumor cells. Biosynthetically labeled type V collagen prepared from organ cultures of human amnion membrane is used for a routine assay of type V collagenolytic activity. The partially purified enzyme a) exists in a latent form requiring trypsin activation for maximum activity; b) has a molecular weight estimated by molecular sieve chromatography of approximately 80,000 daltons; c) is inhibited by EDTA but not phenylmethylsulfonyl fluoride; and d) produces specific cleavage products of both A and B collagen chains.