Dimensions of the trapezium bone: a cadaver and CT study.

ABSTRACT

PURPOSE: The primary purpose of this study was to define the size of the trapezium bone through measurements on cadaver specimens and CT scans of living subjects. The secondary purpose of this study was to determine if any correlation existed between the size of the trapezium and local anatomical parameters. METHODS: The radio-ulnar length (L), dorsopalmar width (ℓ) and height (h) of the distal surface of the trapezium were measured by two independent observers on 20 cadaver specimens. The same measurements were carried out by two other observers on anonymized CT scans from 18 patients. The inter- and intra-observer agreement was determined using the intraclass correlation coefficient. RESULTS: In the cadavers, the mean length, width and height of the trapezium were 22.8, 15.5 and 15.2 mm, respectively. On the CT scans, these same dimensions were 19.2, 11.4 and 11.6 mm. Inter-observer agreement was statistically significant in both parts of the study. DISCUSSION: The dimensions of the trapezium bone were about 3.33 mm larger in cadavers than on CT scans. These differences can be explained partially by a systematic under-sizing error on the CT scans and the fact that the cartilage layer cannot be directly visualized. CONCLUSION: This study was able to define the dimensions of the trapezium bone. It may be possible to predict the trapezium height from the length of the forearm or the width of the radial epiphysis. Our data can be used to adjust the size of trapezium implants to the dimensions of the patient's bone.