In all specimens the cross-sections of bone taken at 4 marked points showed atrophy of the cortical bone which had occured in a typical manner. In the 1-week specimens no qualitative changes could be observed by normal light microscopy. In the 2nd week, however, a vivacious bone remodelling with wide Haversian canals and vessels starts from the medial cortex as could be seen identically in every series of our experiments. In the 4th week and especially in the 6th week it becomes also apparent on the lateral, dorsal and ventral wall. In the 12th week bone remodelling is still active but obvious diminishing of the osteons can be observed between internal and external lamellae. In the 24th week only solitary enlarged sinus and few osteons are found medially and laterally. Alltogether the cortical bone has become very thin. The bone remodelling has stopped and this state is characterized by loss of osteons and abundance of intermediate lamellae. Already in the 1st week polarisation microscopy shows a certain demascating of the collagenous fibres opposite to the plate. The control specimens do not show changes of the collagenous structure in this area. In addition to these results histomorphometric investigations of 1-week specimens revealed a quantitative increase of Haversian canals which are located closer to the medullary space as well as to the side opposite the plate. This result is due to the fact that the bone remodelling starts from the cortex opposite to the metal implant.

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Thirty-eight cases presenting with chronic instability of the ankle joint have been examined. Tenodesis using peroneus brevis has given satisfactory results in 29 cases and poor results in 9 cases (after the method of assessment by Weber). We have classified instability of the ankle joint in a functional way from Types I to III. In Type III, an extended form of tenodesis is required.

Our results are in accordance with previously published data of smaller series using the Zweymüller/Alloclassic( total hip. The survival rate of this cementless rectangular titanium prosthesis for the reported follow-up time compares favorably with contemporary cemented hip prostheses.