Loss of rotator cuff tendon-to-bone interface pressure after reattachment using a suture anchor

Safety evaluation of a laxity-minimizing suture at 5 days and 6 weeks after repair of a sheep infraspinatus tendon

BACKGROUND

The ideal rotator cuff repair achieves high initial fixation strength and secure tendon-to-bone apposition until biological healing occurs. A suture that reacts to the local stress environment by minimizing suture laxity across the repair could theoretically maintain soft-tissue apposition to bone and therefore improve healing.

METHODS

By use of an in vivo ovine shoulder model, the infraspinatus tendon was transected and then repaired with either a laxity-minimizing suture or a traditional high tensile suture. The purpose of this study was to evaluate both sutures' safety at 5 days and 6 weeks after repair.

RESULTS

The macroscopic and microscopic analyses of the repair sites showed similar amounts of surgical trauma. There was no evidence of cheese wiring or tissue necrosis of the repaired tendons for either suture. There was no evidence of systematic toxicity in any animal. The maximum gap between cut edges of the tendon for repairs with the predicate suture was approximately twice the gap for the laxity-minimizing suture.

CONCLUSION

The laxity-minimizing suture was as safe at 5 days and 6 weeks as the predicate suture. Neither suture contributed to local tissue damage or particle generation leading to adverse systematic consequences. An additional observation was that the maximum gap between cut edges of the tendon for repairs with the predicate suture was approximately twice the gap for the laxity-minimizing suture.

Animal models for translational research on shoulder pathologies: from bench to bedside

Several animal models have been used for in vivo and in vitro shoulder research. In vitro models, consisting of cadaveric specimens, are useful in providing basic understanding of the functioning of the shoulder and for biomechanical experiments. In vivo models provide the means to model living phenomena, such as tendon healing process, tendinopathy, instability, and adaptive responses to surgery. However, intrinsic differences among different species make translation to human shoulder pathologies difficult. Most of the animals used in experimental settings are quadrupeds, using the forelimbs for weight-bearing during locomotion, with no or minimal overhead activity. The various animal models already used to study shoulder pathologies are presented in this article. However, there is a lack of validation for these animal models, which provides challenge to the further research in this field.

Tension, abduction, and surgical technique affect footprint compression after rotator cuff repair in an ovine model

INTRODUCTION

Shoulder motion after rotator cuff repair may result in changes in tension and contact pressure at the repair site. Our goal was to determine how tension and motion affect a repair and what type of repair best tolerates these variables.

METHODS

Rotator cuff tears were created ex vivo in 30 ovine shoulders divided into 5 groups: single-row repair, double-row repair, tension-band repair, suture bridge repair, and double-row tension-band repair. A pressure probe was passed through a hole created in the footprint to dynamically measure footprint pressure. The rotator cuffs were repaired, and contact pressure was measured with variable tension placed on the repaired tendon from 10 to 30 N and variable shoulder abduction from -10° to +10°. Repair strength was determined by use of a pull-to-failure test.

RESULTS

Increasing tension on the repaired tendon resulted in an increase in contact pressure whereas increasing the abduction angle resulted in a decrease in contact pressure in all 5 groups. For all abduction and tension combinations, the suture-bridge and double-row tension band groups recorded the highest contact pressures (P < .05), followed by the tension-band, single-row, and double-row repairs. Load to failure was greatest for the 2 double-row techniques, followed by the tension-band, suture-bridge, and single-row repairs.

DISCUSSION

Contact pressure increases as tension increases across the repair and decreases as the shoulder is abducted. The double-row tension-band rotator cuff repair showed the best combination of contact pressure and repair strength.