Virtual reality computer animation of the effect of component position and design on stability after total hip arthroplasty.

Virtual reality technology was utilized to assess the effect of component orientation and component design on the range of motion prior to impingement following total hip arthroplasty. Components were digitized, oriented in the pelvis, and computer animations were performed to assess the likelihood of dislocation with different combinations of component orientation.

Radiographic wear measurements in a cementless metal-backed modular cobalt-chromium acetabular component.

Linear polyethylene wear was measured radiographically and correlated with direct measurements of wear from 21 of 24 liners retrieved at revision. An optical comparator was used to assess linear wear using the shadowgraph technique. Postoperative and prerevision radiographs were reviewed to measure the amount of linear wear radiographically. Seven radiographic methods described in the literature were used: 5 were manual techniques, and 2 techniques used a computer-assisted digitizer. Linear regression analysis showed that there was a statistically significant correlation between the radiographic measurements compared with the direct measurement for 4 of the 5 manual techniques but only 1 of the 2 computerized techniques. Based on these results, radiographic wear measurements of cementless, modular components should be considered qualitative rather than quantitative. There is a significant difference in the measurements obtained among various published techniques. The addition of computer digitization to enhance manual methodology does not improve accuracy.

Corrosion properties of nanocrystalline Co-Cr coatings.

Nanocrystalline and conventional Co-Cr (ASTM F75) coatings were prepared by plasma spraying for possible orthopedic implant applications. Scanning electron microscopy and transmission electron microscopy were used to study the macrostructure and microstructure of the resultant sprayed coatings. The corrosion resistance was characterized by an in vitro potentiodynamic anodic polarization technique in a pseudophysiological solution. The nanocrystalline coating has higher porosity, lower corrosion current density, and less localized damage than that of the conventional one, demonstrating better application potential for orthopedic implants. A change in the atomic compositional difference between the grain interior and the grain boundary, the presence of residual strain in the grain interiors, and a change in the repassivation kinetics are discussed as possible explanations for the enhanced corrosion behavior observed.

Activity level and wear in total knee arthroplasty: a study of autopsy retrieved specimens.

We assessed the correlation between activity level, length of implantation (LOI), and wear in total knee arthroplasty. Twenty-eight implants were retrieved at autopsy from 8 men and 15 women. Linear, volumetric, and visual wear and the presence or absence of creep were quantitated. Functional level was classified using the Knee Society, the standard Charnley classification, and the UCLA activity level scale. The average age at surgery was 68 years +/- 14.0 SD and average LOI was 74 months +/- 38 SD. The average linear and volumetric wear rates were 0.127 mm/y +/- 0.104 SD and 31.80 mm3/y +/- 42.8 SD. LOI (B coefficient = -0.656 +/- 0.0 SE; P<.001) correlated with linear, volumetric, and visual wear rates. Charnley C patients showed decreased volumetric wear in the lateral compartment (P=.01). Decreased activity level (UCLA) correlated with areas of less extent and severity of creep (P=.001 and P<.001).

The cost of teaching total knee arthroplasty surgery to orthopaedic surgery residents.

The higher costs associated with teaching hospitals have received some attention in the literature. The objective of the current study was to determine the increase in resource consumption associated with resident education in knee arthroplasty surgery. Seventy-four patients who underwent primary total knee arthroplasty in the same hospital were studied (50 private practice and 24 teaching practice). Time in the operating room and medical severity of illness were noted. Hospital charges were used as a measure of resource consumption. In addition, length of stay and in-hospital consultations and complications were observed. Kruskall-Wallis, chi square, and stepwise multiple regression analysis were performed. The mean age of the patients was 68 years. Patients who underwent surgery at the teaching service had higher charges ($30,311 +/- $3,325 versus $23,116 +/- $3,341) and longer times in the operating room (190 +/- 19 minutes versus 145 +/- 29 minutes). These patients also had a trend toward more associated comorbid medical conditions (0.71 versus 0.42). Stepwise multiple regression analysis showed that teaching was the most important predictor of charges and operating room time. The results show a 22% increase in perioperative resource consumption for patients who underwent surgery at a teaching service. The measured increase in cost is significantly lower than what has been reported in other series (82%). At the teaching institution, the anesthesia and orthopaedic surgery residents work together on all cases and perform a significant percent of the procedures under direct supervision. The increased resource consumption observed in a teaching service is most likely attributable to the hands-on approach taken to train residents.

Anatomy and physiology of peripheral nerve injury and repair.

The management of peripheral nerve injury continues to be a major clinical challenge. Despite advancements in microsurgical technique, results after nerve repair have been unpredictable and dis appointing. The management of these nerve injuries relies on having a thorough understanding of peripheral nerve anatomy. This is the basis of the classification schemes by Seddon and Sunderland, in which the prognosis of nerve injuries varies depending on the degree of injury to their substructures. The most recent advances in the management of peripheral nerve injuries rely on the ability to manipulate the pathophysiologic processes triggered by nerve injuries and regeneration. End-to-end primary repair should be sought whenever a tension-free repair can be attained. If there is a significant nerve gap, use of nerve autograft remains the gold standard. In nerve injuries where a nerve autograft is not possible, the use of nerve allograft, as well as autogenous, biodegradable, and synthetic nerve conduits has shown promising results in experimental studies.

Core decompression in atraumatic osteonecrosis of the hip.

Core decompression for osteonecrosis of the femoral head continues to be a controversial procedure. We report the results of core decompression in the treatment of hip osteonecrosis. Forty-two patients (67 hips) were evaluated. Minimum follow-up was 2 years. Preoperative outcome instruments were assessed. Volume of involvement (%) from magnetic resonance imaging was assessed. Failure was described as a total hip arthroplasty (THA). Mean patient age was 40.26 years. The average clinical and radiologic follow-up was 40.7 months and 33.1 months. The average Harris Hip Scores preoperatively and postoperatively were 49 and 58. None of the hips classified as Ficat I progressed to THA, whereas 17% of Ficat II hips and 66% of Ficat III hips progressed to THA. Our results demonstrate no relationship between the volume of involvement of the femoral head or the location of the lesion in progression to collapse. Staging with the Ficat classification demonstrated the most statistically significant correlation with progression to THA. The SF-36 scores at last follow-up on our patients were significantly worse than patients undergoing THA.

Smoking and joint replacement: resource consumption and short-term outcome.

Smoking has been shown to increase morbidity and mortality in surgical procedures. Microvascular and trauma surgeons have documented the adverse effect of smoking in the healing of skin flaps and increased complication rates in the treatment of nonunions. In addition, spine surgeons have shown the adverse effects of smoking in fusion rates. The objective of this study was to assess the effects of smoking on the incidence of short term complications, resource consumption, and length of hospital stay of patients undergoing arthroplasty of the hip and knee. Two hundred two patients who underwent joint replacement surgery were evaluated. A smoking history was assessed for all patients. The number of packs multiplied by the number of years as a smoker were calculated. Operative and anesthesia time and medical severity of illness were documented on all patients. Short term outcome was assessed using hospital charges, length of stay, inhospital consults, and the presence and number of complications during the acute hospitalization. One hundred forty-one primary and 61 revision procedures were done. The mean age of the patients was 66.07 years. Sixty-one percent of the patients had osteoarthritis, 3.9% had rheumatoid arthritis, 4.9% had osteonecrosis, 28% had a failed total knee or hip arthroplasty and 2% had a periprosthetic fracture. There were 25 patients who smoked and 177 patients who did not smoke. For patients who currently smoke, the mean number of packs of cigarettes smoked per day multiplied by the number of years as a smoker was 28.3. The average length of stay in the hospital was 5.1 days and the average hospital charges were $31,315. Patients who smoked were younger and had fewer comorbidities than patients who did not smoke. However, patients who smoked were found to have statistically longer surgical time and higher charges adjusted for age, procedure, and surgeon than patients who did not smoke. Patients who smoked also had longer anesthesia times. A history of smoking is obtained easily on all patients. Preoperative screening for nicotine use can predict operative time and health resource consumption. The exact reasons why patients who smoked had higher hospital charges remain elusive. Probable reasons include higher degree of operative complexity (orthopaedic severity of illness). In addition patients who smoked previously also had better short term outcome than patients who currently smoke. This indicates the importance of smoking abstinence before joint replacement surgery and other surgical procedures. Regardless of the exact causes, it is more expensive to treat patients who smoke. Contracting for orthopaedic care should include a history of smoking.

Perioperative X-rays in arthroplasty surgery: outcome and cost.

Numerous legislative proposals to cut reimbursement to surgeons and hospitals are presently included in U.S. congressional and senate agendas. Perioperative x-ray films in arthroplasty surgery are standard operating procedure. Our objective was to assess the effects of the radiologist reading on the clinical and economic outcome of arthroplasty procedures. One hundred consecutive cases were prospectively studied. The radiologist reading, clinical management, and outcome of each case were carefully reviewed. The amount billed for the radiologist interpretation was noted for each examination. A total of 398 studies in 100 patients were done. Ninety-six preoperative, 110 intraoperative, and 192 postoperative radiographic studies were reviewed. These reports took an average of 1.71 days to be recorded on the chart (SD +/- 2.45). The total radiologic professional fees billed to Medicare in these cases was $11,054. (The radiologist's interpretation was not useful in the clinical management and did not affect the outcome in any case.) Assuming that each surgeon takes 1 x-ray film on every arthroplasty case, the total actual savings to Medicare of not having a radiologist reading these studies could reach $536,000 per year; if 2 intrahospital x-ray studies are performed per procedure (preoperative, intraoperative, or postoperative), the savings are $1.1 million per year. These cost reductions are achieved at no sacrifice to quality of care or outcome. Numerous areas of excessive spending with no improvement in outcome exist in the treatment of Medicare patients. There areas should be identified and eliminated before surgical fees are lowered even further.

Osteonecrosis of the femoral head.

New cases of osteonecrosis of the femoral head in the United States number between 10,000 and 20,000 per year. This disease usually affects patients in their late 30s and early 40s. Although a number of authors have related specific risk factors to this disease, its etiology, pathogenesis, and treatment remain a source of considerable controversy. This disorder has been associated with corticosteroid use, substance abuse, and various systemic medical conditions. Either direct damage to osteocytes (e.g., by toxin production) or indirect damage (e.g., due to disorders in fat metabolism or hypoxia) may lead to osteonecrosis. Patients at increased risk for osteonecrosis should be monitored closely. Unfortunately, most cases are diagnosed in an advanced stage of disease, when minimally invasive surgical procedures are no longer helpful. Furthermore, patients in the advanced stage of the disease must undergo total hip replacement at a young age, which carries a poor long-term prognosis.

Nutritional parameters and short term outcome in arthroplasty.

OBJECTIVE: Advances in surgical techniques and management of arthroplasty patients have contributed to a significant reduction in surgical complication rates. Preoperative nutritional status has a significant impact on surgical outcome. Studies have reported improved outcomes in burn and hip fracture patients receiving nutritional supplementation during their recoveries. Our objective was to assess the effects of preoperative nutritional status on the incidence of complications, resource consumption, and length of stay of patients undergoing hip and knee replacement surgery. METHODS: One hundred and nineteen patients were evaluated. Standard preoperative laboratory tests were performed on all patients. Medical severity of illness was assessed on all patients using the Charlson Comorbidity Index. Anesthesia and surgical time was recorded. Short term outcome was assessed utilizing hospital charges as a measure of resource consumption, length of stay (LOS), in-hospital consults and the presence and number of complications during hospitalization. Non-parametric Kruskall Wallis and chi-square statistical analyses were performed. A p value <.05 was considered significant. RESULTS: Mean age was 64.6 years +/-15.62. 52.9% had osteoarthritis (OA), 4.2% had rheumatoid arthritis (RA), 5.9% had osteonecrosis (ON), 9.2% had a hip fracture and 28% had a failed total knee arthroplasty (TKA) or total hip arthroplasty (THA). Mean albumin and total lymphocyte count (TLC) were 38.5 g/L +/-4.78 SD and 1884 cells/microL +/-762 SD, respectively. Patients with albumin levels less than 34 g/L had 32.7% higher charges ($50,108+/-8203 SE vs. $33,720+/-1128 SE, p<.006), higher medical severity of illness (p = .03) and longer LOS (8.6+/-1.7 SE vs. 5.2+/-.356 SE days, p<.001). Patients with TLC less than 1200 cells/microL had higher charges ($32,544+/-1050 SE vs. $42,098+/-3122 SE, p = .004), longer LOS (5.7+/-.531 vs. 5.4 days +/-.368, p = .004) and anesthesia (242.85+/-17.55 SE vs. 198.6 min. +/-6.06 SE, p = .02) and surgical times (177.14 min. +/-17.57 SE vs. 120.21 min. +/-6.22 SE, p = .002) when compared with patients with TLC higher than 1200 cells/microL. These findings were still significant when adjusted for medical severity of illness and age. CONCLUSIONS: Our data demonstrate that preoperative nutritional status is an excellent predictor of short term outcome. Serum albumin and TLC correlate with resource consumption, length of stay and operative time in patients undergoing joint replacement surgery. These parameters may be improved with nutritional supplementation prior to surgery.

Technique for a composite femoral intramedullary plug in cemented hip arthroplasty.

A brief technique to place a cement plug on top of a polyethylene is presented. This technique has helped the authors obtain better cement mantles when they are plugging the canal in total hip replacement.

An algorithm to identify knee prostheses from their radiographic appearances.

Modularity in total knee system design makes it important for the surgeon to know the model of prostheses being revised since components of different designs are not interchangeable. Preoperative information on the manufacturer and model of prostheses implanted may not always be available. This article describes an algorithm that allows surgeons to identify the prosthesis from standard radiographs. Ninety-nine percent of the knee prostheses implanted between 1985 and 1992 can be identified using this algorithm. The algorithm uses the shape of the tibial keel, the type of baseplate, and the shape of the femoral component as branch points to identify the model and manufacturer of 15 primary total knee prostheses. In addition, certain models were found to have radiographic "fingerprints" such as the presence of a spiked tibial keel. This algorithm should be an aid to surgeons performing total knee revisions.

Hemiarthroplasty in hip fracture care: effects of surgical volume on short-term outcome.

In 1992, the Agency of Health Care Administration in Tallahassee, Florida started releasing, as part of the discharge information, the names of the treating physician along with the clinical data. This information was used to assess the effects of volume on the short-term outcome of hemiarthroplasty surgery in hip fracture care as a function of surgeons and hospitals in the state of Florida, during the year 1992. A total of 5,604 cases were available for study. Analysis of the data showed that the average inhospital mortality rate was 4.3%. The average length of stay was 11.2 days. After arbitrarily dividing the doctors into three case volume groups (low, medium, high), results showed that surgeons with a low volume of arthroplasty cases (less than 10 per year) had a statistically significant higher average length of stay and inhospital charges when compared with the other two case volume groups.

The short-term economic implications of prosthetic selection in hemiarthroplasty of the hip.

This retrospective study assessed the economic impact of prosthetic selection in the treatment of displaced intracapsular fractures. The records of 28 patients were divided into two groups: 16 patients who received an Austin-Moore, nonmodular device and 12 patients (6 men and 6 women; mean age, 77 years) who received a modular, bipolar device. The bipolar group had significantly greater mean operative times, total charges for the device, and total charges for supplies. Surgeons treating hip fractures should consider implant cost, functional outcome, and patient demands when selecting a prosthesis for hemiarthroplasty care.

Cost-effectiveness of early surgical intervention in silent osteolysis.

Access to subspecialty care is the subject of significant controversy. Most managed-care systems closely monitor the number of specialist referrals as well as x-rays ordered for patients with no symptoms, but large lytic lesions can exist around implants without any pain. Intervention costs were calculated for 2 groups of patients: 1 group with silent lysis with no symptoms and another group with periprosthetic fractures around lytic lesions. The costs were significantly higher in the group in which the fractures occurred versus the group in which early intervention was performed. Early diagnosis of structurally critical lytic lesions around implants by routine follow-up monitoring is recommended for all joint replacement patients.

Ice-cream truck-related injuries to children.

Few studies exist on the cause and nature of injuries to children from ice-cream truck-related accidents. We reviewed the medical records of 11 children with orthopedic injuries treated at Children's Hospital-San Diego from 1985 to 1995 for injuries in such accidents. Of nine children on their way to or from an ice-cream truck who were struck by an oncoming vehicle, all were girls; eight had pelvic or lower-extremity fractures. When ice-cream trucks park on the street, they pose a danger to children, because children are drawn to them, and the trucks' large size blocks the vision of oncoming drivers.

Cost effectiveness and quality of life in knee arthroplasty.

Few studies quantitate the cost of a quality well being as produced by arthroplasty surgery. The objective was to use the Quality of Well Being Index to calculate the cost per quality of well year in knee arthroplasty surgery. The difference in Quality of Well Being Index scores before and after the intervention was calculated and multiplied by the patient's life expectancy. The procedure cost was divided by this quantity resulting in the cost of a quality well year. One hundred patients underwent a primary knee arthroplasty. There were 30 males (average age, 62 years old) and 70 females (average age, 64 years old). The calculated costs per a quality well year were $30,695 (standard deviation $90,883) at 3 months, $17,804 (standard deviation $25,888) at 6 months, $11,560 (standard deviation $11,874) at 1 year, and $6656 (standard deviation $3567) at 2 years postsurgery. Health economists consider an intervention costing less than $30,000 per quality of well year a bargain to society. Cost effectiveness of knee arthroplasty surgery compares favorably with other surgical interventions such as coronary artery bypass surgery ($5000 per quality of well year) and extremely favorable with medical treatments such as renal dialysis ($50,000.00 for the quality well year). Knee arthroplasty is a cost effective procedure and should be considered an appropriate investment by society.