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

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. Those findings were then assessed by arthroscopic views.

The bare spot area is located 15.8mm from the tip of the olecranon and 13.8mm from the coronoid process (mean values). This area measures 4.1mm in cranio-caudal plane, 2.2mm in transversal plane. This area is located above a small subchondral tubercle that measures 1.0mm 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.

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. Arthroscopic, CT arthrography and anatomical correlation of the bare area of the ulnar trochlear fossa.