[Mechanical stress and subchondral mineralization of the human elbow joint. A CT-osteoabsorptiometric study]

We examined 21 elbow joints (age 60-97 years; mean 79 years) that had been fixed in 3.7% formalin. The articular surface of the trochlear notch was completely divided in 10 cases, undivided in 5, and only partially divided in the medial aspect of the joint surface in 6. Subchondral mineralisation was investigated by means of CT osteoabsorptiometry (Müller-Gerbl et al. 1989) on sections 2 mm apart with a Siemens Somatom SF CT scanner. Two-dimensional reconstruction of the surface distribution was achieved by dividing it into 8 Hounsfield ranges (< 300 HU > 900 HU) and using a joint template. Higher values for the subchondral mineralisation are usually found in the distal and medial parts of the joint, indicating greater stress there. Whereas the radial head and the capitulum show a distribution pattern with mineralisation falling off more or less concentrically from the centre outwards, the trochlea and trochlear notch are often poorly mineralised in the centre. There is one maximum on the proximal and one on the distal aspect of the joint surface. Such "two-peak" distribution patterns are more often found when there is complete central division of the articular cartilage of the trochlear notch than when it is continuous. In the latter case, a more central localisation of higher subchondral density is common. In the humero-radial part of the joint, the mineralisation pattern suggests central pressure transmission, probably a result of the fovea capitis radii being slightly less curved than the opposing capitulum.(ABSTRACT TRUNCATED AT 250 WORDS)