Objectives: Operative repair of distal biceps tendon ruptures have shown successful outcomes. However, little is known about the amount of tendon or repair site lengthening or creep. Treatment algorithms in regards to repair fixation, immobilization, initiation of activity and physical therapy are largely made on previous tendon healing principles and anecdotal findings. The purpose of our study was to evaluate distal biceps tendon repair via intratendinous radiostereometric analysis to evaluate tendon lengthening/creep at different time intervals of healing. Methods: Ten patients were recruited who sustained a distal biceps rupture requiring operative repair. Distal biceps repairs were performed using an endobutton only, single incision technique. Intraoperatively, two 2-mm tantalum beads with laser-etched holes were sutured to the distal biceps tendon. One bead was placed at the radius tendon interface and the other placed 1cm proximal to the first bead. Beads were evaluated via both CT scans immediately post-operatively and at 16 weeks and x-rays obtained at time 0 and then at 4, 8, and 16 weeks. Measurements were made using the endobutton to bead and bead-to-bead distances in order to assess repair site elongation as well as tendon elongation over time. Following final follow-up, patients underwent a DASH questionnaire and ultrasound to confirm the integrity of the tendon. Results: Ten patients were included in the study. Nine patients had complete ruptures with one having a partial rupture that underwent completion and subsequent repair. All patients showed statistically significant lengthening after surgery. The mean amount of lengthening after surgery was 21.8 mm (range 10.1-29.7 mm, p < 0.05). The repair site lengthened a mean of 12.5 mm (range 8.8-17.0 mm, p <0.05) and the tendon lengthened a mean of 9.4 mm (range: 4.0-18.8 mm, p<0.05) from surgery to final follow-up. The greatest change in lengthening was noted between time 0 and week 4 (mean: 11.8 mm, range: 4.0-18.0 mm, p<0.05), with the least amount of lengthening between week 8 and week 16 (mean: 3.6 mm, range: 2.1-5.5 mm, p<0.05). Average DASH scores after surgery was 4.5 (range: 2.5-16.7). Final ultrasound evaluations found no re-ruptures in any of the patients. Conclusion: This study’s findings suggest that all patients undergoing distal biceps tendon repair have significant elongation of their repair site and tendon after surgery, with the greatest amount of lengthening seen in the early post-operative period. These findings lend insight into decision-making with regards to intraoperative repair fixation and post-operative activity protocols while also adding knowledge to overall tendon repair principles.
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