Abstract
We assessed the initial mechanical properties of repaired infraspinatus tendons after immediate and delayed repairs using #2 sutures. Fifteen shoulders were harvested from 8 beagle dogs, and were divided into two repair groups. Immediate repair group (group I) (n=8) : the insertion of the infraspinatus tendon was detached from the greater tuberosity and then sutured to the bone trough with 4-strand sutures (#2 Ethibond). Delayed repair group (group D) (n=7) : the insertion of infraspinatus tendon was detached from the greater tuberosity and retracted proximally. Five weeks later, the shoulders were harvested and the tendons were repaired in the same way as the immediate repair group. The ultimate strength and stiffness of each tendon was measured with a force transducer, and the pattern of the tendon disruption was also determined. The data were analyzed by one-way ANOVA and P <0.05 was regarded as statistically significant.
The average ultimate tendon strength was 155.7±35.7 (S.D.) N in group I and 170.7±53.6 (S.D.) N in group D, with no significant difference between the two groups (p=0.528). The average tendon stiffness was 18.5±12.8 (S.D.) KN/m in group I and 13.8±5.6 (S.D.) KN/m in group D, with no significant difference between the two groups (p=0.380). In group I, the tendon ruptured in 6 shoulders and suture loops in the tendon moved distally during traction in 2 shoulders. In group D, the tendon ruptured in 6 shoulders and the bone avulsed at the greater tuberosity in one shoulder. There was no difference in the initial mechanical properties between the immediate and delayed repair tendons after surgery using #2 sutures. A repaired rotator cuff tendon end at 5 weeks after detachment is expected to have clinically enough strength.
