Comparison of tunnel suture and suture anchor methods as a function of time in a sheep model

There is little quantitative information available on the required healing time after a rotator cuff surgery. This study evaluated two surgical procedures by comparing the healing strength as a function of time of the tendon in a bone trough using a sheep model. The two surgical procedures compared were bioabsorbable suture anchors and bone tunnel suture technique. The infraspinatus tendon was split in half and procedure (suture anchor/tunnel suture) locations were randomly allocated to the proximal or distal half of the tendon at the healing time points of 0, 3, 6, 9, and 12 weeks with n = 6 at t = 0 and n = 8 in all other groups. At each time point, the surgical (right) and normal (left) shoulders were harvested and stored in a -30 degrees C freezer until testing. Biomechanical testing was performed using a MTS 809 Axial/Torsional Servohydraulic System. Special cryo-grips designed and built to test the infraspinatus tendon-bone interface in anatomical alignment were used. All samples were preloaded with 5 Newtons, and then force was measured during a crosshead displacement of 50 cm/min until failure. Force and displacement data were recorded to calculate load to failure and stiffness of the bone-tendon construct. There was only significant difference (95% CI) in mean tensile force at week 0, with the bone tunnel suture technique tensile force greater than the suture anchor method tensile force (p = 0.0261). There was no significant difference between stiffness means at any of the survival times.