Greater radial tuberosity size is associated with distal biceps tendon rupture: a quantitative 3-D CT case–control study

Purpose: During pronation, the distal biceps tendon and radial tuberosity internally rotate into the radioulnar space, reducing the linear distance between the radius and ulna by approximately 50%. This leaves a small space for the distal biceps tendon to move in and could possibly cause mechanical impingement or rubbing of the distal biceps tendon. Hypertrophy of the radial tuberosity potentially increases the risk of mechanical impingement of the distal biceps tendon. The purpose of our study was to determine if radial tuberosity size is associated with rupturing of the distal biceps tendon. Methods: Nine patients with a distal biceps tendon rupture who underwent CT were matched 1:2 to controls without distal biceps pathology. A quantitative 3-dimensional CT technique was used to calculate the following radial tuberosity characteristics: 1) volume in mm3, 2) surface area in mm2, 3) maximum height in mm and 4) location (distance in mm from the articular surface of the radial head). Results: Analysis of the 3-dimensional radial tuberosity CT-models showed larger radial tuberosity volume and maximum height in the distal biceps tendon rupture group compared to the control group. Mean radial tuberosity volume in the rupture-group was 705 mm3 (SD: 222 mm3) compared to 541 mm3 (SD: 184 mm3) in the control group (p = 0.033). Mean radial tuberosity maximum height in the rupture-group was 4.6 mm (SD: 0.9 mm) compared to 3.7 mm (SD: 1.1 mm) in the control group, respectively (p = 0.011). There was no statistically significant difference in radial tuberosity surface area (ns) and radial tuberosity location (ns). Conclusion: Radial tuberosity volume and maximum height were significantly greater in patients with distal biceps tendon ruptures compared to matched controls without distal biceps tendon pathology. This supports the theory that hypertrophy of the radial tuberosity plays a role in developing distal biceps tendon pathology. Level of evidence: Level III.