The impact of free-radical stabilization techniques on in vivo subsurface mechanical properties in highly cross-linked polyethylene acetabular liners.

Highly cross-linked polyethylene (HXLPE) for total hip arthroplasty was developed to improve wear resistance in vivo and associated complications in comparison to ultrahigh molecular weight polyethylene. This material typically goes through various free-radical stabilization techniques by remelting, single-annealing, or sequentially annealing the polyethylene to improve in vivo oxidation and wear properties. The purpose of this study is to determine if there is evidence of subsurface microhardness changes in retrieved HXLPE liner at the rim and articular subsurface after extended in vivo time that could be associated with oxidation and its effects on mechanical properties and implant integrity. Retrieved HXLPE liners were chosen based on peak subsurface Fourier transform infrared spectroscopy oxidation values. Each was mechanically tested for subsurface microhardness at both the rim and articular surface using a validated microindentation technique. Rim testing demonstrated a decrease in mechanical integrity that corresponded to higher subsurface oxidation values regardless of the free-radical stabilization technique. At the articular surface, a decrease in mechanical integrity was observed near the surface corresponding to peak oxidation and Vicker's hardness, which decreased with increasing depths. This was found in all groups, with the exception of the single-annealed liners, which demonstrated decreased mechanical integrity trends at greater depths between 1.0 and 2.0 mm. Our results suggest that subsurface mechanical properties do change in vivo for certain implants. Though it is likely that the mechanical failures are multifactorial, we have shown that mechanical property degradation of HXLPE liners does occur with long-term in vivo exposure and should be considered a possible risk factor.

The Morscher Press-Fit Acetabular Component: An Independent Long-Term Review at 18-22 Years.

BACKGROUND: There are relatively few 20-year results of uncemented acetabular components, and most of these are modular designs. This study reports the 20-year results of a monoblock press-fit acetabular component. METHODS: A total of 122 total hip arthroplasties (111 patients) using the Morscher cup were reviewed at a mean of 19.7 years. The average age at implantation was 57.3 years (range, 36-74 years), and 81 (66%) were men. RESULTS: Twenty-two patients (25 hips) had died. Seven hips were revised, including 5 acetabular revisions. Six patients (6 hips) declined to participate but were known not to have been revised. The mean Oxford hip score was 41.1 (range, 22-48), and the mean reduced Western Ontario and McMaster Universities Osteoarthritis Index score was 5.7/48 (range, 0-24). Eccentric wear was seen in 13 (15.7%) and major osteolysis in 14 (17%) of 82 surviving hips with radiographs. The all-cause revision rate was 0.32 per 100 observed component years (95% confidence interval [CI], 0.13-0.66). The 20-year Kaplan-Meier survival was 93.4% (CI, 86.6-96.8) for all-cause revisions, 95.5% (CI, 89.4-98.1) for any acetabular revision, and 97.1% (CI, 91.2-99.1) for acetabular aseptic loosening, wear, or osteolysis. CONCLUSION: The Morscher acetabular component has continued to perform well at 20 years despite using conventional polyethylene with results that match or surpass other cementless acetabulae.

Surgical treatment for lateral epicondylitis: a long-term follow-up of results.

HYPOTHESIS: Since its first description, the pathology, natural history, and treatment of lateral epicondylitis have remained controversial. For patients in who conservative management fails, surgery remains an option. The optimal method of surgery remains debatable and is further confounded by a relative lack of long-term follow-up studies. MATERIALS AND METHODS: This study describes a modification of the Nirschl surgical technique and presents its long-term results. Patients undergoing this open technique were reviewed by use of the Hospital for Special Surgery and Mayo elbow performance assessment tools, as well as having grip strength and subjective outcome recorded. RESULTS: From June 1986 to December 2001, 158 consecutive patients (171 elbows) underwent surgery in a single-surgeon series. Of these patients, 137 (86.7%) were available for follow-up at a mean of 9.8 years. The mean age of the group was 42 years. Subjectively, the results were good to excellent in 94.6% of patients and in 92.6% to 94.0% of patients by use of the Hospital for Special Surgery and Mayo scores, respectively. No differences were noted in grip strength. No patient required revision surgery. CONCLUSIONS: This repeatable open technique offers excellent results with a low rate of complications at a mean follow-up of 9.8 years. These results compare favorably in terms of numbers followed up, length of follow-up, and outcome and offer strong evidence of its efficacy.

Pelvic pseudotumor: an unusual presentation of an extra-articular granuloma in a well-fixed total hip arthroplasty.

A 76-year-old woman developed a pelvic mass and abdominal pain 12 years after cementless total hip arthroplasty. The mass was a cystic granuloma that communicated with the hip joint via a soft tissue herniation under the inguinal ligament. There was no acetabular lysis or defects. The shell and femoral component were well fixed, the polyethylene was worn, and a liner exchange was undertaken. The cyst was debrided, and follow-up computed tomography demonstrated resolution of the granuloma and no recurrence of the cyst. Removal of the source of the particle wear debris via liner exchange or revision surgery combined with cyst debridement via a single incision is recommended.

Animal cloning and the FDA--the risk assessment paradigm under public scrutiny.

The evidence gathered thus far--ultimately to be published in the Draft Risk Assessment on Animal Cloning--indicates that there are no unique risks associated with animal cloning.

The US FDA and animal cloning: risk and regulatory approach.

The Food and Drug Administration's (FDA's) Center for Veterinary Medicine issued a voluntary request to producers of livestock clones not to introduce food from clones or their progeny into commerce until the agency had assessed whether production of cattle, swine, sheep, or goats by somatic cell nuclear transfer (SCNT) posed any unique risks to the animal(s) involved in the process, humans, or other animals by consuming food from those animals, compared with any other assisted reproductive technology (ART) currently in use. Following a comprehensive review, no anomalies were observed in animals produced by cloning that have not also been observed in animals produced by other ARTs and natural mating. Further systematic review on the health of, and composition of meat and milk from, cattle, swine, and goat clones and the progeny of cattle and sheep did not result in the identification of any food-consumption hazards. The agency therefore concluded that food from cattle, swine, and goat clones was as safe to eat as food from animals of those species derived by conventional means. The agency also concluded that food from the progeny of the clone of any species normally consumed for food is as safe to eat as those animals. The article also describes the methodology used by the agency to analyze data and draw these conclusions, the plans the agency has proposed to manage any identified risks, and the risk communication approaches the agency has used.

Food consumption risks associated with animal clones: what should be investigated?

Somatic Cell Nuclear Transfer (SCNT), or cloning, is likely to be used for the expansion of elite breeding stock of agronomically important livestock used for food. The Center for Veterinary Medicine at the US Food and Drug Administration has been developing a risk assessment to identify hazards and characterize food consumption risks that may result from cloning. The risk assessment is comprised of two prongs. The first evaluates the health of animal clones, and is referred to as the Critical Biological Systems Approach. The second considers the composition of meat and milk from animal clones. Assessing the safety of food products from animal clones and their progeny, at least during these early stages of the development of the technology, is best accomplished by using both approaches: prospectively drawing on our knowledge of biological systems in development and maturation, and in retrograde, from an analysis of food products. Subtle hazards and potential risks that may be posed by animal clones must, however, be considered in the context of other mutations and epigenetic changes that occur in all food animal populations.

Rapid osteolysis after revision hip arthroplasty in Paget's disease.

Rapid bone turnover in Paget's disease has been of concern to many surgeons performing hip arthroplasties. We present the case of a 71-year-old man with Paget's disease affecting the proximal femur. He had undergone total hip arthroplasty 14 years before. He sustained a fracture at the tip of the femoral component, which was managed with revision total hip arthroplasty. His postoperative course was complicated by rapid and profound osteolysis of the femur distal to the fracture site, secondary to disease activity. This case highlights the need for awareness of Paget's disease activity and this potential complication.