Microscopic fracture aspects of impact tested human bones

The fracture aspects of impact twisted human femurs and tibias have been studied in their wet condition. The main tool used to correlate fracture behaviour with bone structure was the scanning electron microscope. Supplementary data were obtained from macroscopic fracture pattern analyses and stress coat experiments on slowly tested dried bone. The interest of the data reported concerns two major points. Firstly the analysis of the fractographic results leads to the conclusion that the fracture has presumably been initiated by shearing parallel with the torsion axis. The fracture propagates along so called spiral and oblique fracture lines. Secondly, the correlation of the macroscopic fracture pattern with microscopic fracture aspects indicates that the fracture is initiated along the cement lines, which can be considered as the weak matrix in an osteon-cement lining composite. The fracture propagates along the cement lines as well as through osteons and lamellae. Throughout the impact fracture surfaces ductile and brittle fracture aspects were observed, although the brittle fracture mode was predominant during propagation.

Haematogenous osteomyelitis of the patella. Report of three cases

Three cases of osteomyelitis of the patella are reported. One presented as an acute septic arthritis and another developed a sterile arthritis despite antibiotics. The clinical signs, diagnosis and treatment are discussed. Treatment with rest and antibiotics failed to cure the disease. In all three cases a sequestrectomy was carried out resulting in healing of the affected patella and recovery of knee mobility.

Aging of bone tissue: mechanical properties

The mechanical properties of machined cortical bone specimens from human femora and tibiae were determined in tension, torsion, and compression for a population ranging in age from twenty-one to eighty-six years. No significant differences were found between the mechanical properties of male and female specimens. Tibial specimens had greater ultimate strength, stiffness, and ultimate strain than femoral specimens. Consistent decreases with age for all mechanical properties except plastic modulus were found in the femoral but not in the tibial specimens. No consistent significant differences in tension properties were found in specimens from normal, osteoporotic, and corticosteroid-treated individuals.

Fatigue fractures of the femoral component of Charnley and Charnley-Müller type total hip prostheses

A survey is given of the mechanical failures of the femoral component of Charnley and Charnley-Müller type total hip prostheses. Fractographic analysis reveals that all the prostheses have broken by metal fatigue. A review of the clinical data has been combined with a metallurgical and a mechanical study in order to assess the reasons of the mechanical failures. The following conclusions have been reached. The prosthesis should be inserted in varus position with regard to the axis of the intramedullary canal, and the prosthesis should be made of an alloy with appreciably higher yield stress and fatigue strength than the alloys of the investigated broken Charnley and Charnley-Müller type prostheses.

Treatment of clubfoot by posterior capsulectomy

Posterior capsulectomy is a complete excision of the posterior tibiotalar and talocalcaneal capsule with a release of the distal tibiofibular connection. The operation is proposed for a resistant or relapsed clubfoot, where remaining equinus is the major problem. A follow-up of 29 operations showed that the average talocalcaneal angle became normal in the AP and lateral views. The best results were obtained with long postoperative cast immobilization, i.e. 6 months.