Background

Knotted and knotless single-anchor reconstruction techniques are frequently performed for the reconstruction of full-thickness tears of the subscapularis (SSC) tendon. However, it is yet unclear if one technique is superior to the other.
Hypothesis/purposes: The hypothesis of the present study was that knotted reconstruction provides superior biomechanical stability compared to knotless reconstruction.

Methods

Eight matched pairs of human cadaveric shoulders were dissected and a full-thickness partial tear of the SSC (grade 3, according to the Fox and Romeo classification) was created. Prior to biomechanical evaluation, the specimens were equally randomized into two reconstruction groups: I) knotless single anchor, II) knotted single anchor. Using a customized setup which was integrated in a dynamic material testing machine, the humeri were consecutively loaded from 10 to 60 N, from 10 to 100 N, and finally from 10 to 180 N for 50 cycles, respectively. Furthermore, the gapping behavior of the tear was analyzed using a tracking system. Finally, the stiffness, gapping, maximal stiffness, yield loads, and maximum failure loads of both reconstruction groups were statistically elaborated. In all specimens, bone quality was measured at the footprint of the SSC by micro-computed tomography after biomechanical testing.

Results

No significant difference in stiffness was found between the two groups in any of the load stages [P = 0.550 (10 to 60 N); P = 0.950 (10 to 100 N); P = 0.480 (10 to 180 N)]. Furthermore, no significant difference was found in terms of gapping, maximal stiffness (P = 0.710), yield strength (P = 0.674), or maximal failure load (P = 0.690). Distribution of the failure modes was also not statistically different (P = 0.135) between the groups. Bone quality was equal for both groups.

Conclusions

The results suggest that single-anchor knotless and knotted reconstruction techniques used to repair full-thickness partial tears of the SSC ensure comparable primary stability of the SSC tendon.