SH10: DYNAMIC ASSESSMENT OF FOOTPRINT PROPERTIES OF ROTATOR CUFF REPAIRS OVER TIME FOLLOWING THE REPAIR: STRESS RELAXATION AS A POTENTIAL CAUSE OF EXCESSIVE GAP FORMATION CAN BE PARTIALLY REVERSED WITH RETIGHTENING.

Abstract

Rotator cuff repair failure may to some extent be attributed to tendon-bone gap formation at the repair sight caused by insufficient suture tightening. We measured the footprint contact properties over time of single row and trans-osseous equivalent repairs. We also investigated the effect of suture retightening on the repair.

Rotator cuff tears (RCT) were created in the supra-spinatus tendon of 6 cadaveric shoulders. An electronic pressure sensor (Tekscan) was placed between the tendon and bone to measure the footprint pressure. The OPUS AutoCuff System was used to consecutively repair the RCT using a single row repair (SR-R) and two trans-osseous equivalent repair (TOE-R) techniques;

1. two parallel sutures (TOE-P) and

2. cross over suture pattern (TOE-C). Sutures were tightened, then retightened in each group.

Peak initial contact force, were recorded on suture tightening (peak force) and equilibrium contact properties after 300 seconds relaxation (equilibrium force). Data were analysed using pairwise ANOVA.

All techniques demonstrated a similar trend in the contact properties over the test period with an initial peak in contact force on tightening of the sutures, followed by a rapid drop in contact pressure immediately after suture tightening, and finally tending towards equilibrium contact force at 300 seconds.

The TOE-C group demonstrated the highest mean ‘peak force’ and the highest ‘equilibrium force’ after 300 seconds relaxation. The TOE-P ‘peak force’ and ‘equilibrium force’ were −15% and −3% that of TOE-C, while the SRR was −45% and −25% that of TOE-C.

Retightening the sutures a second time had little effect on the SSR contact properties, while retightening the TOE repairs increased the equilibrium contact force by 30% although this was not significant.

Significant relaxation occurs especially within the first 30s, compromising the contact properties.

TOE-R’s exhibit better contact properties than SRR. Retightening the TOE-R’s tended towards a higher final equilibrium contact force. SRR repair contact properties were unaffected by a second tightening.

TOE-R’s should be re-tightened before the suture is locked