Tendon-Bone Insertion Repair and Regeneration Using Polyglycolic Acid Sheet in the Rabbit Rotator Cuff Injury Model

Background The quality of tendons has considerable limitations regarding torn rotator cuff tendons. Tissue-engineering techniques using a biodegradable scaffold offer potential alternatives for recreating a valid tendon-to-bone interface. Hypothesis A polyglycolic acid (PGA) sheet could facilitate the regeneration of the rotator cuff tendon insertion in vivo. Study Design Controlled laboratory study. Methods An implant consisting of a PGA sheet, a rapidly absorbable material, was used to replace a completely resected infraspinatus tendon insertion in 33 adult Japanese white rabbits. The contralateral infraspinatus tendon was replaced by poly-L-lactate-epsilon-caprolactone (PLC), a slowly absorbable material, by the same methods based on the results of the pilot study. Histological comparisons were made at 4, 8, and 16 weeks, and mechanical evaluations were performed at 4 and 16 weeks in both groups. Unrepaired defects were created in a control group. Results: In the control group, the rotator cuff defects were covered with thin fibrous membranes with many fibroblasts arranged in an irregular pattern. In the PLC group, some chondrocytes were seen in the tendon insertion; however, these were not arranged along the long axis for a 16-week period. In the PGA group, a well-arranged fibrocartilage layer could be found in the regenerated tendon insertions; however, these tendon insertions were mainly regenerated by type III collagen. In mechanical examinations, the PGA group had significantly higher values in the maximum failure load, tensile strength, and Young's modulus for the 4-week and 16-week periods. These 3 categories statistically improved from 4 to 16 weeks postoperatively in both groups except for the Young's modulus in the PGA group (E = 5.66 at 4 weeks to 5.53 at 16 weeks). Conclusion The PGA sheet scaffold material allows for tendon insertion regeneration with a fibrocartilage layer but displays mechanical properties inferior to those of the normal tendon in an animal model. Clinical Relevance The PGA sheet represent a possible alternative scaffold material for tendon regeneration in rotator cuff repair.