Ankle morphometry evaluated using a new semi-automated technique based on X-ray pictures

Background. The study of bone morphometry is important in anatomy, biomechanics and the design of joint arthroplasty, because the design of prostheses depends also on the knowledge of joint geometry, both for the replication of function and for the proper sizing of the components. Relevant information for the human ankle joint bones is particularly scarce. Methods. A large number of morphological measurements of the ankle joint were collected in 36 normal subjects by means of a new semi-automated radiographic measurement method based on standard frontal and sagittal X-ray projections. Lengths, heights and widths of the main parts of this articulation together with the radii of curvature of the talar dome and of the trochlea tali in the sagittal plane were worked out. Statistical analysis was performed on these measurements. Findings. A large spectrum for the values of these measures was found. Significant correlation was found among some of the measures, but not between any of these and the subject height. Interpretation. Bones at the ankle joint have similar shapes, i.e. the three dimensions are in direct proportion to each other. No one of the internal dimensions is correlated with the only one possible external measurement, i.e. the malleolar width. Sizes of the current total ankle replacement designs may differ considerably from real corresponding joint dimensions.