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Biomedical subjects

F C Ewald

Publications and source records attributed to F C Ewald.

At least 55 records · Page 3Linked to original sources
PubMed1982

Stress fracture of the patella following duopatellar total knee arthroplasty with patellar resurfacing.

Stress fracture of the patella can occur with significant frequency following patellar replacement with the duopatellar knee prosthesis. In the first 372 knees with patellar resurfacing, the incidence was 0.7% in rheumatoid arthritis (2 fractures in 286 knees) and 3.5% in osteoarthritis (3 fractures in 86 knees). The incidence may be greater in osteoarthritic patients because they have more function and are generating greater force across the patellofemoral joint. There was an association with osteonecrosis of the patella in at least three cases in which a lateral retinacular release had been performed and the lateral superior genicular artery sacrificed. This vessel should be preserved during a lateral release to save its contribution to the blood supply of both the patella and the lateral skin flap. Initial treatment of the stress fractures can be nonoperative, with surgery necessary only if the patellar prosthesis has become dislodged, or if pain or inadequate active extension persists. If the fracture can not be repaired, patellectomy can yield a good result. To avoid stress fracture, a minimal amount of patellar articular surface should be resected and the peripheral cortex of both the medial and lateral facets preserved. Fewer stress fractures may occur if a smaller fixation lug is used, thereby preserving more patellar bone stock.

Aged↗
PubMed1981

Fixation of tibial components of knee prostheses.

Twelve different tibial components were compared for fixation. The components included compartmental, anteriorly joined, posterior-cruciate retaining, and one-place with one, two, or three fixation posts; all-plastic or with a metal tray. The apparatus applied compressive load with anterior-posterior force, rotational torque, or varus-valgus moment. The relative deflections, both compressive and distractive, were measured between the component and the bone. The least deflections occurred with one-piece metal-tray components with one or two posts and with one-piece plastic components with a post on each side. Compartmental components deflected the most.

Biomechanical Phenomena↗
PubMed1980

Capitellocondylar total elbow arthroplasty.

Sixty-nine non-constrained capitellocondylar metal-to-plastic total elbow-replacement prostheses were implanted in sixty-four patients with rheumatoid arthritis. These patients were followed for an average of 3.5 years. Postoperative flexion and pronation were significantly improved, but no significant increase in postoperative extension or supination could be demonstrated. Based on a rating system evaluating pain and function, there were 87 per cent good or excellent results. The complication rate based on the total number of prostheses implanted was 39 per cent. Eight patients required revision of the arthroplasty: four for dislocation of the prosthesis, two for sepsis, one for loosening, and one for a fracture. Eight other asymptomatic patients showed minimum radiolucent lines adjacent to the ulnar component. No patient demonstrated radiolucent lines adjacent to the humeral component.

Adolescent↗
PubMed1978

Total hip replacement with and without osteotomy of the greater trochanter. Clinical and biomechanical comparisons in the same patients.

Twelve patients with bilateral hip replacement, one side performed with a trochanteric osteotomy and the other without osteotomy, were analyzed by review of the clinical records, the findings on physical examination, preoperative and postoperative Harris hip scores, each patient's evaluation, biomechanical analysis of the preoperative and postoperative roentgenograms of the hips and pelvis, and force-plate gait analysis. All operations yielded good results clinically but the majority of patients preferred the replacement done without osteotomy. Blood loss and trochanteric bursitis were greater problems in patients who had an osteotomy. There were no differences between the two groups in the postoperative Harris scores or in the biomechanical measurements made on the preoperative and postoperative roentgenograms except for the change in the abductor-muscle length. Changes in this parameter correlated well with the patients' symptoms and clinical findings.

Adult↗
PubMed1976

Complications of total hip-replacement arthorplasty in patients with rheumatoid arthritis.

During the period 1969 through 1974, 716 total hip-replacement arthorplasties were performed. The results of the surgery in 275 cases of rheumatoid arthritis as regards complications were compared with those in 382 procedures in cases of osteoarthritis. In contrast to the reports of others,the incidence of deep would infection in the two groups was found to be equal. Patients undergoing total hip-replacement arthroplasty as a revision of a previous operation had a substantially increased risk of infection. Patients with rheumatoid arthritis, however, were more subject to certain other complication (intraoperative fracture, difficulties with anesthesia, and malposition of prosthetic components), in addition to the complications that were predictable because of the involvement of multiple joints and the systemic disease process.

Adult↗
PubMedDate not supplied

Total knee arthroplasty experience at the Robert Breck Brigham Hospital.

Between 1973 and 1978, 1,474 metal-to-plastic knee arthroplasties were evaluated to determine the typical modes of failure and improved design concepts (Table 2). Although the concepts are still evolving, and longer follow-up is necessary, recent experience with nearly 1,000 semiconstrained devices allowing cruciate retention strongly suggests that duopatella and kinematic design concepts are correct. Soft tissue reconstruction is critical with these designs, since they rely heavily on soft tissue integrity and balance. If the concepts of soft tissue balance, prosthetic design, and physical rehabilitation are applied, total knee replacement is as reliable in relieving pain and restoring function as total hip replacement. The low incidence of radiolucency at the bone-cement interface (although the length of follow-up is relatively short), coupled with the results of in vitro bench testing, suggest that the longevity of this generation of knee implants should be adequate.

Biomechanical Phenomena↗
PubMedDate not supplied

Six- to 11-year results of total hip arthroplasty in rheumatoid arthritis.

The results of 138 total hip arthroplasties in 98 rheumatoid arthritic patients were reviewed six to 11 years (mean, 7.0 years) after operation. While 96% of the patients were clinically improved as a result of surgery, radiographic analysis suggests that, despite their low functional requirements, this group of patients experiences mechanical loosening and failure with time. Improvements in prosthetic design and cementing technique should contribute to a lowered incidence of mechanical failure in the future. In addition to improvements in technology, the failure rate can be further diminished by recognition of the systemic problems associated with rheumatoid arthritis, e.g., high incidence of infection, osteopenia, and sequelae of multiple joint involvement. In reconstruction of the acetabulum, especially in the presence of protrusio, failure to restore the anatomic position and orientation of the acetabulum predisposes to loosening and migration.

Arthritis, Rheumatoid↗
PubMedDate not supplied

Factors influencing the incidence and outcome of infection following total joint arthroplasty.

During a ten-year period, 4240 total hip, knee, and elbow arthroplasties were performed. The overall infection rate was 1.25%. Certain groups were identified as being at higher risk of infection following total joint arthroplasty: rheumatoid arthritics were at 2.6 times greater risk than osteoarthritics; patients undergoing total hip arthroplasty as a revision of a previous operation were eight times more likely to have infection than those undergoing a primary operation; and patients with metal-to-metal hinged knee prostheses, when compared with patients with metal-to-plastic knee prostheses, were 20 times more likely to have infection. The majority of infections could be attributed either to perioperative problems or late bacterial seeding from a distant site. Although most infections occurred by two years after operation, late infections, particularly in rheumatoid patients via the hematogenous route, occurred as long as nine years after operation. There was no correlation between the Gram's-staining characteristics of the pathogen and the outcome of the infected joint. Gram-negative organisms were frequent in the perioperative period and reflected either nosocomial infection or the ineffectiveness of the prophylactic antibiotic regimen used in inhibiting gram-negative pathogens. The major factors that influenced the outcome of the infected joint included the interval from the initial surgery to recognition of infection, the delay in institution of appropriate treatment, the particular joint that was infected, the integrity of the bone-cement interface, the type of prosthesis used, and the host susceptibility. Identification of high-risk groups and the recognition that patients with joint implants are at risk of infection at any time in the postoperative period may lead to a lowered infection rate in the future.

Aged↗