Time-dependent changes in failure loads of 3 biceps tenodesis techniques: In vivo study in a sheep model

Background: Failure load of the tendon-fixation material-bone unit has a crucial importance for the rehabilitation protocol after tenodesis procedures. Purpose: To investigate and compare the time-dependent changes in fixation strengths of 3 proximal biceps tenodesis techniques. Study Design: Controlled laboratory study. Methods: Two intraosseous techniques (suture sling and tenodesis screw) and 1 extraosseous technique-(2 suture anchors) were investigated. Biceps tenodesis was performed on 45 shoulders of 26 sheep, 15 shoulders for each technique. Twelve similar cadaveric sheep shoulders (4 for each technique) provided the day 0 results. Sheep were sacrificed at 3, 6, and 9 weeks, and specimens were tested for the failure load of the tenodeses. Results: All 3 tenodesis techniques were found to have similar failure loads at all time intervals tested. All 3 curves remained below the failure load of the intact tendon (862 ± 96 N) and above their day 0 results for the study period; similarly, at each time interval, results tended to be better compared to the previous test. The tenodesis screw group exhibited significantly higher failure loads at week 3 (419 ± 53 N) compared to day 0 values (164 ± 45 N) (P = .009). The same level of significance was observed at week 6 in the remaining 2 groups. Conclusion: Tenodesis of the biceps tendon on the proximal humerus at an extra-articular site does not weaken after surgery. The tenodesis screw group had a significantly higher increase in the fixation strength within the first 3 weeks. Clinical Relevance: No significant differences could be found between the failure loads of all 3 investigated tenodeses for the first 9 weeks.