CT arthrography and anatomical correlation of the bare area of the ulnar trochlear fossa: a risk of misdiagnosis of cartilage ulcerations

Abstract

Aims: There is a variable bare area on the ulnar trochlear fossa that may be somehow interpreted as a cartilage defect. We aimed to correlate radiological images and dissections of this bare spot with CT arthrography imaging.

Materials and methods: We conducted a double study that included 10 unpaired fresh-frozen human cadaveric elbows (CT arthrography + dissection) and 40 CT arthrography of patients to investigate the 3-D architecture of the trochlear fossa of the ulna. Positioning, shape and measurements of the bare spot of each ulna were measured and correlated. A total of 40 were analyzed with this protocol of measurements to validate the anatomical findings.

Results: The bare spot area is located 15.8 mm from the tip of the olecranon and 13.8 mm from the coronoid process (mean values). This area measures 4.1 mm in cranio-caudal plane, 2.2 mm in transversal plane. This area is located above a small subchondral tubercle that measures 1.0 mm in antero-posterior axis. No significant difference has been found between left and right elbow regarding its positioning and shape. A significant difference has been found between genders regarding the positioning of this area but not according to its shape.

Conclusion: The ulnar trochlear notch has a small area without cartilage. This bare area is located at the site of fusion of the different ossification center of the proximal ulna. It should not be interpreted as a chondral lesion. The existence of a subchondral tubercle clearly indicates that this uncovered zone is normal. Radiologist should consider this when interpreting elbow CT arthrography.