Background: Rotator cuff tears are a common source of shoulder pain. High rates (20%-94%) of structural failure of the repair have been attributed to multiple factors, including poor repair tissue quality and tendon-to-bone integration. Biologic augmentation using growth factors has potential to promote tendon-to-bone integration, improving the function and long-term success of the repair. One such growth factor is platelet-derived growth factor–BB (PDGF-BB), which has been shown to improve healing in tendon and bone repair models.
Hypothesis: Recombinant human PDGF-BB (rhPDGF-BB) combined with a highly porous type I bovine collagen matrix will improve the biomechanical function and morphologic appearance of the repair in a dose-dependent manner, relative to a suture-only control, after 12 weeks in an acute ovine model of rotator cuff repair.
Study Design: Controlled laboratory study.
Methods: An interpositional graft consisting of rhPDGF-BB and a type I collagen matrix was implanted in an ovine model of rotator cuff repair. Biomechanical and histologic analyses were performed to determine the functional and anatomic characteristics of the repair after 12 weeks.
Results: A significant increase in the ultimate load to failure was observed in repairs treated with 75 µg (1490.5 ± 224.5 N, P = .029) or 150 µg (1486.6 ± 229.0 N, P = .029) of rhPDGF-BB, relative to suture-only controls (910.4 ± 156.1 N) and the 500-µg rhPDGF-BB group (677.8 ± 105.9 N). The 75-µg and 150-µg rhPDGF-BB groups also exhibited increased tendon-to-bone interdigitation histologically. No differences in inflammation or cellularity were observed among treatments.
Conclusion: This study demonstrated that an interpositional graft consisting of rhPDGF-BB (75 or 150 µg) and a type I collagen matrix was able to improve the biomechanical strength and anatomic appearance in an ovine model of rotator cuff repair compared to a suture-only control and the 500-µg rhPDGF-BB group.
Clinical Relevance: Recombinant human PDGF-BB combined with a type I collagen matrix has potential to be used to augment surgical repair of rotator cuff tears, thereby improving clinical success.
Background: Rotator cuff tendon heals by formation of an interposed zone of fibrovascular scar tissue. Recent studies demonstrate that transforming growth factor–beta 3 (TGF-β3) is associated with tissue regeneration and “scarless” healing, in contrast to scar-mediated healing that occurs with TGF-β1.
Hypothesis: Delivery of TGF-β3 in an injectable calcium-phosphate matrix to the healing tendon-bone interface after rotator cuff repair will result in increased attachment strength secondary to improved bone formation and collagen organization and reduced scar formation of the healing enthesis.
Study Design: Controlled laboratory study.
Methods: Ninety-six male Sprague-Dawley rats underwent unilateral detachment of the supraspinatus tendon followed by acute repair using transosseous suture fixation. Animals were allocated into 1 of 3 groups: (1) repair alone (controls, n = 32), (2) repair augmented by application of an osteoconductive calcium-phosphate (Ca-P) matrix only (n = 32), or (3) repair augmented with Ca-P matrix + TGF-β3 (2.75 µg) at the tendon-bone interface (n = 32). Animals were euthanized at either 2 weeks or 4 weeks postoperatively. Biomechanical testing of the supraspinatus tendon-bone complex was performed at 2 and 4 weeks (n = 8 per group). Microcomputed tomography was utilized to quantitate bone microstructure at the repair site. The healing tendon-bone interface was evaluated with histomorphometry and immunohistochemical localization of collagen types I (COLI) and III (COLIII). Statistical analysis was performed using 2-way analysis of variance with significance set at P < .05.
Results: There was significantly greater load to failure of the Ca-P matrix + TGF-β3 group compared with matrix alone or untreated controls at 4 weeks postoperatively (P = .04). At 2 weeks, microcomputed tomography revealed a larger volume of newly formed bone present at the healing enthesis in both experimental groups compared with the control group. By 4 weeks, this newly formed, woven bone had matured into calcified, lamellar bone. Histomorphometric analysis demonstrated significantly greater fibrocartilage and increased collagen organization at the healing tendon-bone insertion site in both experimental groups compared with the control group at 2 weeks (P = .04). Over time, TGF-β3 delivery led to greater COLI expression compared with COLIII at the healing enthesis, indicating a more favorable COLI to COLIII ratio with administration of TGF-β3.
Conclusion: Augmentation with an osteoconductive Ca-P matrix at the tendon-bone repair site is associated with new bone formation, increased fibrocartilage, and improved collagen organization at the healing tendon-bone interface in the early postoperative period after rotator cuff repair. The addition of TGF-β3 significantly improved strength of the repair at 4 weeks postoperatively and resulted in a more favorable COLI/COLIII ratio.
Clinical Relevance: The delivery of TGF-β3 with an injectable Ca-P matrix at the supraspinatus tendon footprint has promise to improve healing after soft tissue repair.
