STUDY TO DESCRIBE THE MORPHOLOGY OF A SERIES OF CLAVICLES & THE DIMENSIONS OF ITS INTRAMEDULLARY CANAL

Abstract

Aim: A study was done to investigate the range in size and morphological features of a series of human clavicles.

Method: A Phillips CT scanner was used to examine morphometric properties of 42 right and 36 left adult cadaveric clavicles. The resulting data was analysed with Voxar 3D software. The length of the s-shaped clavicle was measured and the planar cross-sectional geometry of the intramedullary canal and cortical thickness assessed at 10% increments along the length of the bone. MPR (multi-plane reformat) imaging allowed ‘fly-through’ reconstruction of cross-sectional morphology as one travels along the length of the bone.

Results: The sample studied followed a normal distribution with mean size= 136.2mm (range: 112.6– 172.0 mm). In general the sternal portion of the clavicle is circular or prismatic in cross-section where as the acromial portion is flatter on its superior and inferior surfaces. A spacious, variably shaped canal is observed at the sternal and acromial thirds in contrast to the denser, smaller, more circular shaped canal in the central third of the bone. Unlike most long bones, the clavicle was observed to have an extensive network of trabeculae along the entire length of the intramedullary canal. The central third of the clavicle has the thickest cortex. The mean cortical thickness (3.37mm; range: 1.8– 7.9mm) was greatest at a point 60% from the sternal end with the mean thinnest cortex (1.37 & 1.15mm) found at the extreme sternal and acromial ends of the bone respectively.

Conclusion: The clavicle is highly variable in shape and exhibits dramatic variations in both curvature and cross-sectional geometry along its length. Contrary to previous teaching, MPR reconstruction accurately demonstrates clear visualization of a distinct intra-medullary canal.