Faculty Bibliography

Total knee arthroplasty is one of the most commonly performed orthopaedic surgical procedures in the United States. Primary concepts in the surgical technique include restoring limb alignment and soft-tissue balance about the knee. Currently, traditional mechanical alignment concepts that focus on restoring neutral limb alignment have been challenged by the principle of kinematic alignment. In addition to these recent philosophical challenges, new technologies have been introduced to help the surgeon more accurately achieve optimal limb alignment and soft-tissue balance.

Bilateral hip arthroplasty has been reported to be a safe and effective way to treat bilateral hip arthritis in a selective group of patients. We report a follow-up of 30 patients who underwent simultaneous bilateral total hip arthroplasty with hydroxyapatite implants and were followed for an average of 19.4 years. Patients had an average Harris Hip Score of 90 at the latest follow-up (range, 78-99). The average Western Ontario and McMaster Universities Arthritis Index questionnaire index score was 12 (range, 0-41), with high functional results on the 12-Item Short Form Health Survey (SF-12) and Oxford 12 questioners. Using the Kaplan-Meier survivorship analysis, with revision for any reason as an end point, survivorship was 94% at 12 years, 88% at 15 years, 74% at 18 years, and 61% at 23 years. All revisions were for the acetabular component, and the survivorship for the femoral component was 100% throughout the 23-year period. We conclude that bilateral uncemented total hip arthroplasty can provide satisfactory long-term clinical, radiological, and functional outcomes in patients even with older-generation polyethylene liners and stem designs.

A polyethylene cup explanted after 41 years was examined using several analytical techniques to determine whether there was a material cause for the extremely low wear observed. Neither the amount of polyethylene oxidation nor crystallinity appeared to be a factor.

Different acoustic frequencies have been used to diagnose progression of osteoarthritis, gross pathology, and wear in knee prostheses. It is possible that detailed analysis of higher frequencies could detect and quantify the smaller geometric changes (asperities) that develop in articular prosthetic wear. In this study we evaluated the feasibility of using ultrasonic emission to determine total knee arthroplasty (TKA) type and time from implantation using a simple, handheld measurement system. We examined the ultrasound emission generated by similar designs of posterior stabilized (PS) and cruciate retaining (CR) total knee prostheses and native knees of 58 patients and 10 controls. The subjects were asked to sit, rise, sit again, and take five steps while recording the acoustic data from both knees. Acoustic emission analysis examined frequency distributions and power spectrums of the recorded signals, and their relations to prosthesis type and time from implantation. We screened 44 CR and 48 PS TKAs, as well as 24 native knees. Analysis of this data suggested a possibility of differentiating between type of implants, and a relation to time since implantation. Our data suggest that we might be able to assess the status and time from implantation of a TKA by acoustic emission signals. Further in vitro analysis of the relationship of wear to ultrasonic emission data are needed for accurate quantification of arthroplasty wear. A simple, in-office screening tool for TKA patients could indicate which patients require closer follow-up and monitoring due to risk of potential problems

BACKGROUND: Previous acoustic emission (AE) studies of the hip have proposed using AE for the diagnosis of musculoskeletal conditions and assessing the clinical status (loosening, wear, etc.) of prostheses. However, these investigations have had problems with spurious signal noises or complicated measurement techniques, or both. PURPOSE: We performed a study on 98 patients to evaluate the feasibility of employing ultrasonic emission (UE) to determine total hip arthroplasty (THA) status, using a simple, hand-held measurement system that has addressed some of the prior problems with hip AE studies. METHODS: UE was recorded from both hips of study patients during walking and sitting activities. The patients had 79 metal-on-polyethylene implants, and at least 15 each with ceramic-on-polyethylene, ceramic-on-ceramic and metal-on-metal articulations; 10 young subjects without THA were similarly recorded as controls. Data were obtained from waveform analysis and standard UE signal parameters. Patient radiographs were evaluated for THA status, and wear measurements were made for metal-on-polyethylene articulations. RESULTS: There were distinct types of UE waveforms produced; one was typical of the control subjects as well as some patients. We did not find an apparent relationship among these waveform types and type of THA bearing, length of implantation or wear measurements in the metal on polyethylene bearings. CONCLUSIONS: Our results suggest that it may be possible to assess the status of THA by UE signals, but further studies are necessary to quantify this finding. The clinical relevance of this investigation is that a simple, in-office screening means for THA patients could indicate those patients who require closer follow-up and monitoring

Total hip arthroplasty is a highly successful procedure where the hip joint is replaced by an artificial ball and socket joint. Bearing wear continues to be a contributing factor to implant failure. Prosthetic femoral heads roughen in vivo which leads to increased wear. Along with the introduction of improved polyethylene which reduces wear by up to 99%, improved femoral head materials have been introduced to improve resistance to abrasion. The abrasion resistance of two of these improved femoral heads was assessed in this study and compared to a cobalt chromium (CoCr) femoral head. The resulting wear performance against a polyethylene acetabular component was assessed. The bulk ceramic (zirconia toughened alumina) femoral head exhibited superior abrasion resistance compared to CoCr (97% reduction in damage) as well as reduced wear after abrasion (97% reduction in wear). The oxide coated zirconium niobium femoral head showed inferior abrasion resistance compared to CoCr (99% increase in damage) as well as increased wear after abrasion (161% increase in wear). Both femoral head surfaces utilize hard ceramic materials, however, the thin ceramic coating on top of a softer metallic substrate of the oxide coated bearing was unable to withstand aggressive abrasion. (C) 2009 Elsevier B.V. All rights reserved

Recent case studies of surface oxidized zirconium THA heads removed after attempted, closed reduction have shown significant surface damage that has been suggested as potentially deleterious to polyethylene wear. We obtained 4 clinically retrieved specimens, produced well-characterized surface damage on additional heads, and tested them on a hip simulator. After 1 million cycles, the amount of polyethylene wear was related to the extent of surface damage, the most damaged clinical specimen showing more than 50 times more wear than a new head. Although all heads after failed attempted closed reduction(s) should be replaced, surface oxidized zirconium heads are of particular concern; those patients with a successful, simple closed reduction should be monitored for excessive wear

Recently, a strong emphasis has been placed on establishing rehabilitation protocols after primary total hip and knee arthroplasty in an attempt to shorten, improve, and standardize the postoperative period of recovery. Less invasive surgical techniques, patient demands, and the pressure of insurance regulations have forced postoperative rehabilitation to be placed on an expedited scale. With these concerns in mind, we introduce a pre- and postarthroplasty program involving the Pilates method. Modified exercises have been developed to account for the postoperative precautions and needs of total hip and knee arthroplasty patients. A patient-driven interest in the use of Pilates for postoperative rehabilitation has led to the development of our programs following total hip or knee arthroplasty. In reviewing our early observations of a small series of patients, it appears this technique can be utilized without early complications; however, further studies are necessary to confirm its utility and safety. Level of Evidence: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence

Previous studies have suggested that femoral component positioning in resurfacing arthroplasty may affect strains in the femoral neck that could lead to decreased implant longevity. A strain gaged, Sawbones model was used to determine the femoral neck strains for a variety of resurfacing head translations and angulations. We found that head positions affected strain distributions, most positions leading to increased neck strains, often over 100%, with the exception being a varus head position where the superior neck strains decreased over 50%. Although the clinical meaning of these findings is unclear, it could be of concern for stress-shielding or fatigue fracture of the femoral neck

This study consists of a single case report of a patient who had an irreducible obturator dislocation of a total hip arthroplasty after a motor vehicle accident, not previously described in the English literature. In particular, the focus will be on offering an educated opinion on the risk factors for dislocation and difficulties encountered with this type of dislocation. The aim is to offer valuable insight based on the operative experience with this patient and to supplement the literature with the management of such a complication following total hip arthroplasty