Augmentation of a rotator cuff tendon repair using a bioinductive biocomposite scaffold in an ovine infraspinatus model

Clinical studies support that augmenting rotator cuff repair through the induction of new host tissue can prevent gapping or retear by increasing tendon thickness and strength. To date, most implants for augmentation have focused solely on biologic healing or mechanical reinforcement of the repair. This preclinical study evaluated the short- and long-term performance of a biocomposite (type I collagen and poly-l-lactic acid [PLLA]) scaffold to support the rapid proliferation, maturation, and remodeling of new host tissue in a large-animal rotator cuff repair model. A full-thickness detachment of the central third of infraspinatus tendon was created and repaired in 25 sheep using a double-row suture bridge technique augmented with a biocomposite scaffold. Animals were euthanized at 6, 12, 26, and 52 weeks for assessment of tendon thickness and maturation via magnetic resonance imaging (MRI) and histology (n = 3 sheep per time point). Mechanical testing was performed at 6 weeks (n = 7 sheep) and 12 weeks (n = 6 sheep) and compared to the nonoperative controls. All animals recovered well following surgery, and no adverse events were encountered during the in vivo phase out to 52 weeks. Histology revealed a progressive integration and incorporation of new fibrous tissue within, above, and below the scaffold at 6 weeks that continued to mature and remodel with time out to 52 weeks. Enthesis healing improved with time as the repaired infraspinatus tendon healed to the humeral attachment. MRI findings showed an 180% increase in tendon thickness at all time points, compared with the nonoperative control. The ultimate load (newtons) of the repairs significantly increased between 0, 6, and 12 weeks (P < .01). This study demonstrated the collagen-PLLA biocomposite scaffold increased the thickness of a repaired rotator cuff tendon through the rapid induction of host-generated connective tissue at all time points. Histology confirmed the bioinductivity of organized fibrous tissue within, above, and below the scaffold. Progressive healing and maturation of the enthesis was observed with MRI and histology out to 52 weeks, without any adverse reactions. The combination of biologic healing and mechanical reinforcement in a single implant provides an exciting solution for rotator cuff augmentation.