Cartilage thickness of distal humerus and its relationships with bone dimensions: magnetic resonance imaging bilateral study in healthy elbows.

Background: Little is known about the cartilage thickness of the distal humerus and how it affects the shape of the articular surface. Our aims were to assess cartilage thickness and to determine the extent to which it affects the true profile of the distal humerus.

Methods: We assessed 78 healthy elbows (39 subjects, 19 women and 20 men) with a mean age of 28 years (range, 21-32 years). Cartilage thickness was measured by use of high-definition magnetic resonance imaging scans at 19 different points of the articular surface, 13 on the trochlea and 6 on the capitellum, on the axial and coronal views. Bone diameters at the medial and lateral trochlear ridges, trochlear groove, and capitellum, as well as the articular surface width, were measured. Subject height was used as an indirect measurement of humerus length. Pearson correlation coefficients and the Student t test were used.

Results: Cartilage thickness showed a significant variation (range, 0.4-1.8 mm) independent of sex and side. It appeared thinner at the medial and lateral edges, whereas it increased at the level of the trochleocapitellar and trochlear grooves, the lateral trochlear ridges, and the center of the capitellum. The mean bone diameters of the medial ridge, lateral ridge, trochlear groove, and capitellum measured 25.1 mm, 21 mm, 16.9 mm, and 19.6 mm, respectively. The mean width of the articular surface was 42.9 mm (range, 35.8-50.2 mm). No significant correlation was found between cartilage thickness and bone dimensions.

Conclusion: Cartilage thickness is not uniform and modifies the morphologic shape and diameters of the humeral articular surface. These findings may be relevant to anatomic prosthesis design.