The average shearing strength of surgical Simplex P bone cement has been experimentally evaluated and found to be 5,762 plus or minus 180 psi. The average shearing strength for compact bone is about 10,000 psi. Therefore surgical Simplex P does not resist shear forces as well as compact bone and should not be used as a substitute for bone whenever possible. The inclusion of 10 per cent barium sulfate U.S.P. for radiographic purposes does not adversely affect the shear strength of the cement. This amount of barium is the same percentage by weight as that found in radiopaque Simplex P in clinical usage today. Varying the loading rate between 0.005 and 0.5 in/min slightly affected the magnitude of the shear force at failure. A comparison of the effect of short term curing times on the magnitude of the shear force at failure reveals that surgical Simplex P strengthens with time. The curing periods varied from 2 to 168 hours.

Acrylic Resins↗

PubMedDate not supplied

The effect of radiation on the shear strength of acrylic bone cement.

Bone loss due to secondary neoplastic disease of bone has frequently presented the orthopedic surgeon with difficult or insoluble problems of surgical management. Local radiation is the most effective, and widely used form of therapy for this type of metastatic disease. Levels of radiation in vitro comparable to therapeutic doses, as well as levels 6 times that commonly used in vivo on patients, demonstrate no significant effect on the mechanical properties of acrylic bone cement.

Acrylic Resins↗

PubMedDate not supplied

Long-term follow-up of the Conaxial (Beck-Steffee) total ankle arthroplasty.

Between 1975 and 1977, 30 patients with traumatic arthritis or rheumatoid arthritis underwent 36 Conaxial (Beck-Steffee) ankle replacements (DePuy, Warsaw, IN). Thirty-two were primary replacements and four were revisions of previous ankle arthroplasties. Twelve patients had traumatic osteoarthritis and 18 patients had rheumatoid arthritis. The average age at operation of patients with rheumatoid arthritis was 61 years (range 28-67 years) and with osteoarthritis was 52.9 years (range 32-72 years). The average follow-up was 10.8 years, with a range of 10 to 13 years. Early postoperative complications included wound dehiscence in 39% of patients (14 patients), deep wound infection in 6%, fractures of the medial or lateral malleolus in 22%, and painful talofibular impingement in 14%. At 2-year follow-up, 27% of the ankle replacements were loose. Sixty percent were loose at 5 years and 90% were loose at the 10-year follow-up. Ten patients had implant removal and attempted fusion. Six, or 60%, fused in an average of 5 months. Of those patients who achieved ankle fusion, four had internal fixation and iliac crest autografting, one had a Charnley compression apparatus with allograft bone, and one had internal fixation with allograft bone. The constrained Conaxial ankle replacement should no longer be implanted because of a 90% loosening rate at 10 years and an overall complication rate of 60%.

Adult↗

PubMedDate not supplied

Tuberculosis of the first cervical vertebra.

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Adult↗

PubMedDate not supplied

Revision of Mueller total hip arthroplasties.

Experience with 65 revisions of Mueller total hip arthroplasties and a minimum of two years follow-up on 32 revised total hips showed that the results appear to be poor in a significant number (22%) of patients: 18% required additional surgery. Revision of total hip arthroplasties with recementing of one or both components carries a significant risk of intraoperative and postoperative complications. Since the introduction of femoral components with improved metallurgic properties, no stem failures have occurred. Varus position of the femoral stem predisposes for stem loosening. Aspiration arthrography is of limited value in the evaluation of a painful total hip. In cases of femoral component loosening with gross cystic changes on the roentgenograms, early revision is recommended as fracture of the femoral shaft may ensue. Late loosening of the acetabular cup as yet appears to be an uncommon cause of total hip arthroplasty failure. Attention to the details of surgical technique and more research on material selection in primary total hip replacement are important.

Adult↗