Mineralisation and mechanical strength of the subchondral bone plate of the inferior tibial facies.

BACKGROUND: The implantation of total ankle prosthesis is one of the most challenging operations in orthopaedic surgery. The main problem that surgeons face is the fixation of the total ankle prosthesis on the tibial side. The subchondral bone plate of the distal tibia is considered the strongest region on the inferior tibial facies. Based on information about the mineralisation of the subchondral bone plate, conclusions can be made concerning the mechanical stress, age-related changes, post-surgical biomechanical situations and regions of fixation. The aim of this study was to determine the correlation between the mineralisation of the subchondral bone plate and the topical mechanical strength. METHODS: By means of CT-osteoabsorptiometry, the distribution of mineralisation in the subchondral bone plate in 18 distal Tibiae was investigated. After removal of the cartilage of the facies articularis inferior, the mechanical strength of the joint surface was measured with an indentation apparatus. The linear regression of the mineralisation density and the maximal mechanical strength to penetrate the subchondral bone plate was determined. RESULTS: Our data showed a coefficient of determination between 0.75 and 0.97 and a coefficient of correlation between 0.86 and 0.97. The T test showed significance (P < 0.05). Furthermore, we demonstrated a bicentric distribution of mineralisation patterns. The maximal mineralisation was found ventromedially and mediolaterally on the joint surface. CONCLUSION: Our study shows good correlation of mineralisation and mechanical property of the inferior tibial facies. Therefore, as the results provide information on the topographical distribution of bone quality, they could be useful for the development of new fixation methods for total ankle prosthesis.

[Ligaments of the knee]. / Bänder des Kniegelenks.

The ligaments of the knee can be divided into four groups. Ventral reinforcements are the patellar retinaculae. The posteromedial complex stabilizes the valgus stress. It consists of the medial collateral ligament, the thickened posteromedial capsule and a branch of the tendon of the semimembranosus muscle as well as the oblique popliteal ligament. On the lateral side the posterolateral complex protects the knee against varus stress. Here the lateral collateral ligament, the tendon of the popliteus muscle and the so-called popliteofibular fibres work together. The cruciate ligaments control the contact between femoral condyles and tibial plateau during flexion-extension of the knee. They course between the two layers of the capsule, the membranous and the synovial layer.