William R. Murray

Constrained acetabular components.

Between May 1987 and October 1990, 21 constrained acetabular components were used in revision total hip arthroplasty at the University of California, San Francisco. In 18 patients, the device was placed for a chronically dislocating total hip arthroplasty. In the remaining three, intraoperative instability during revision total hip arthroplasty necessitated its use. At the minimum 2-year follow-up evaluation (average, 31 months; range, 24-64 months), 15 patients (71%) experienced no further dislocations or subluxations. There were eight dislocations in the remaining six patients (29%). The average Harris hip score at the follow-up evaluation was 76 points (range, 32-100 points). For those patients who redislocated (n = 6), an increased acetabular abduction angle of the metallic acetabular cup, averaging 70 degrees, was the only predictive factor of failure of the constrained cup (P < .05). No radiographic or clinical evidence of loosening in the 19 porous ingrowth acetabular component was observed. This device will relieve the complication of severe hip instability in the majority of patients, but is not universally successful.

Avascular Necrosis of Bone after Renal Transplantation

Two groups of patients underwent renal transplantation and were managed similarly in all respects, except for the dosage of corticosteroids administered post-operatively. For the first group, sixty-eight in number, the dosage was approximately three times greater than that for the second group with 136 patients. Avascular necrosis of bone appeared in sixteen patients in the first group and in two in the second. A greatly increased incidece of avascular necrosis after repeated transplantations was noted.

Use of Antibiotic-containing Bone Cement

Erythromycin and colistin (or other thermostable antibiotics) may legally be added to polymethylmethacrylate (PMMA) for use in the fixation of prostheses to bone. The antibiotics are leached or rapidly released from the combination in bactericidal concentrations. They do not reduce the strength characteristics of the cement below acceptable standards, nor do they change its handling characteristics. Erythromycin alone was used in 1112 total hip arthroplasties between 1971 and 1976, with an infection rate of 0.98%. Erythromycin-colistin bone cement was used in 786 total hip arthroplasties from July 1976 to December 1980, with a deep-wound infection rate of 0.4%. Erythromycin-colistin-containing bone cement is safe and effective in treatment of and prophylaxis against deep-wound infection in total joint arthroplasty.

99mTc-methylene diphosphonate bone imaging in the evaluation of total hip prostheses.

A retrospective study was performed to determine the accuracy of 99mTc-methylene diphosphonate bone imaging in the evaluation of total hip arthrosplasty for lossening and/or infection. Using focally increased activity at the tip of the femoral component or in the region of the acetabular component as a criterion, the examination was 77% specific and 100% sensitive for loosening and/or infection. A possible explanation for the increased uptake at the tip of the femoral component and the role of this examination in the management of a painful total hip prosthesis are discussed.

Juxtaacetabular ganglionic (or synovial) cysts: CT and MR features

Radiographic findings include supraacetabular bone erosions, subchondral acetabular cysts, soft tissue masses with or without radiolucent inclusions representing nitrogen gas, joint space narrowing, and abnormal hip configuration. Associated tears of the acetabular labrum were confirmed by arthrography in two patients. Computed tomography and magnetic resonance imaging afforded improved delineation of soft tissue ganglia and their relationship to the acetabular bone, labrum, and hip joint. We report our experience with seven patients in whom various imaging examinations clearly documented the presence of soft tissue cystic lesions adjacent to the acetabulum; in six of the seven patients, significant clinical manifestations were evident in the affected hip. Such cysts, whether designated synovial or ganglionic in type, appear to be a frequently overlooked yet important cause of hip symptomatology.

Prophylactic coverage of dental patients with artificial joints: A retrospective analysis of thirty-three infections in hip prostheses

Persons with total joint prostheses theoretically risk infection from the transient bacteremia that may accompany dental treatment, and the literature suggests that these patients be treated prophylactically with antibiotics. Effective prophylaxis requires that the most common infecting organisms be identified and tested for drug sensitivity. We reviewed thirty-three cases of infected hips out of a total of 1,855 hip prosthesis placements. The infections were classified as early (less than 6 months after placement) or late (greater than 6 months after placement). In the patients studied, the risk of infection associated with dental procedures was extremely low (0.05 percent). Staphylococcus aureus was the organism most often isolated from the infected hips, and its incidence was twice as high in the late as in the early infections. Based on the drug sensitivities of the most common infecting organisms, the recommended drugs of choice for prophylactic treatment of dental patients with artificial joints are erythromycin, clindamycin, or a penase-resistant penicillin.

MR imaging of chronic osteomyelitis.

Magnetic resonance (MR) at 1.5 T was used preoperatively and prior to aspiration to determine extent and location of infection in eight patients with chronic osteomyelitis. There was excellent correlation between MR and surgical findings in all cases. Infected areas, both Intraosseous and extraosseous, displayed increased signal intensity on T2-weighed images. Sequestra, sinus tracts, and soft tissue abscesses were seen. By directly imaging foci of infection MR may have certain advantages over CT and scintigraphy in the evaluation of chronic osteomyelitis.

Acetabular salvage in revision total hip arthroplasty using the bipolar prosthesis.

From June 1978 to December 1987, 106 revision total hip arthroplasties (THA) for acetabular salvage were performed using a bipolar device. Bone grafting was necessary in most of the patients. Five patients were unavailable for follow-up examination, leaving 96 patients (101 hips), who were followed for an average of two years 11 months (range, two months to 8.5 years). Excellent or good results were obtained in 43 patients; fair results were achieved in 20 patients. Of the nine patients with poor results, five demonstrated roentgenographic evidence of subluxation, and four showed no roentgenographic changes that could explain their persistent pain. Twenty-nine of these bipolar revisions failed and required reoperation. Fourteen of these failures were revised using fixed, cementless devices in conjunction with bone grafting. Ten patients developed deep-wound infection. Nine were treated successfully; the tenth patient died of overwhelming sepsis, her case complicated by multiple infected joint arthroplasties. While the results of revision THA in the present series are not as satisfactory as those reported by others who used fixed cemented or fixed cementless acetabular components, they are superior to the results obtained with excisional arthroplasty, the only alternative in many of these cases.

Imaging of the hip joint. Computed tomography versus magnetic resonance imaging

The authors reviewed the applications and limitations of computed tomography (CT) and magnetic resonance (MR) imaging in the assessment of the most common hip disorders. Magnetic resonance imaging is the most sensitive technique in detecting osteonecrosis of the femoral head. Magnetic resonance reflects the histologic changes associated with osteonecrosis very well, which may ultimately help to improve staging. Computed tomography can more accurately identify subchondral fractures than MR imaging and thus remains important for staging. In congenital dysplasia of the hip, the position of the nonossified femoral head in children less than six months of age can only be inferred by indirect signs on CT. Magnetic resonance imaging demonstrates the cartilaginous femoral head directly without ionizing radiation. Computed tomography remains the imaging modality of choice for evaluating fractures of the hip joint. In some patients, MR imaging demonstrates the fracture even when it is not apparent on radiography. In neoplasm, CT provides better assessment of calcification, ossification, and periosteal reaction than MR imaging. Magnetic resonance imaging, however, represents the most accurate imaging modality for evaluating intramedullary and soft-tissue extent of the tumor and identifying involvement of neurovascular bundles. Magnetic resonance imaging can also be used to monitor response to chemotherapy. In osteoarthrosis and rheumatoid arthritis of the hip, both CT and MR provide more detailed assessment of the severity of disease than conventional radiography because of their tomographic nature. Magnetic resonance imaging is unique in evaluating cartilage degeneration and loss, and in demonstrating soft-tissue alterations such as inflammatory synovial proliferation.

Computed tomography of the musculoskeletal system.

To demonstrate the potential impact of computed tomography on orthopaedics, a brief review was done of four generations of scanners and of one new development (assay of bone mineral in the spine) that is presently being researched. To assess the utility of the method in treating orthopaedic problems, the cases of 140 patients, including patients with congenital anomalies, tumors, infections, and traumatic lesions, were analyzed. In the majority of the patients the technique provided useful information, often unobtainable with any other technique.