Biomechanical consequences of proximal biceps tenodesis stitch location: musculotendinous junction versus tendon only

The purpose of this study was to determine the biomechanical effects of placing the biceps tenodesis stitch at the musculotendinous junction versus in the tendon only. Placing the stitch at the musculotendinous junction was hypothesized to result in a significantly weaker repair than stitching in the tendon only.

Testing was performed on two groups of six matched pairs of long head of the biceps (LHB) with enclosed musculotendinous junction and muscle belly. Specimens were randomly distributed between two groups. The same baseball whipstitch configuration was performed using the same suture material in both groups. In group 1, the stitch configuration started 1 cm proximal of the musculotendinous junction (tendon tissue only). For contralateral specimens, the baseball whipstitching included the distal 1 cm of the musculotendinous junction. Specimens were pulled to failure at a rate of 60 mm/min. Ultimate failure load and failure pattern were recorded.

Average ultimate failure load of group 2 was significantly higher than group 1 (mean increase 18.6 %, range -9.7 to 35.8 %; p = 0.046). A cut-through failure pattern was observed for all specimens in both groups. There were highly significant correlations between ultimate failure load and tendon thickness (p = 0.004, τ = 0.636), age of the specimen (p = 0.002, τ = 0.724), and gender (p = 0.004, τ = -0.739). No significant difference between the groups regarding tendon diameter was observed.

Baseball whipstitching of the LHB including the distal part of the tendon and the musculotendinous junction was stronger than sutures placed in the tendon alone. These results suggest that suture pattern affects initial strength of repair, and therefore may affect decisions regarding early post-operative rehabilitation or ultimate clinical outcomes. Inclusion of the musculotendinous junction should be considered clinically for improved time zero strength of the repair construct.