Amy S. Lyons

Augmentation of a Rotator Cuff Suture Repair Using rhPDGF-BB and a Type I Bovine Collagen Matrix in an Ovine Model

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 inter-digitation 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.

Biomechanical Analysis of an Ovine Rotator Cuff Repair via Porous Patch Augmentation in a Chronic Rupture Model

Background Rotator cuff repair is a commonly performed procedure, but many of these repairs fail in the postoperative term. Despite advances in surgical methods to optimize the repair, failure rates still persist clinically, thereby suggesting the need for novel mechanical or biological augmentation strategies. Nonresorbable implants provide an appealing approach because patch materials may confer acute mechanical stability and act as a conductive scaffold for tissue ingrowth at the site of the tendon insertion. Hypothesis The polyurethane scaffold mesh will confer greater biomechanical function relative to a nonaugmented repair after 12 weeks in vivo using a chronic ovine model of rotator cuff repair. Study Design Controlled laboratory study. Methods After development of the chronic rupture model, the tensile failure properties of the nonresorbable mesh-augmented repair (n, 9) were compared with those of a surgical control in an ovine model (n, 8). Results Rotator cuff repair with the scaffold mesh in the chronic model resulted in a significant 74.2% increase in force at failure relative to the nonaugmented surgical control (P = .021). Apparent increases in stiffness (55.4%) and global displacement at failure (21.4%) in the mesh-augmented group relative to nonaugmented controls were not significant (P = .126 and P = .123, respectively). At the study endpoint, the augmented shoulders recovered 37.8% and 40.7% of the force at failure and stiffness, respectively, of intact, nonoperated controls. Conclusion Using the previously described chronic rupture model, this study demonstrated that repair of a chronic tendon tear with the polyurethane scaffold mesh provides greater mechanical strength in the critical healing period than that of traditional suture anchor repair. Clinical Relevance This device could be used to enhance the surgical repair of the rotator cuff and consequently improve long-term clinical outcome.

Evaluation of rhPDGF-BB in Combination with a Flowable Collagen Matrix for the Treatment of Acute Achilles Tendon Injury:

INTRODUCTION: Rupture of the Achilles tendon occurs frequently in the general population, affecting athletes and non-athletes of all ages. Most Achilles injuries occur in men between the ages of 30 and 50 years of age [1]. The mechanical rigors on the Achilles tendon and the limited cell source and vascular supply available at the repair site contribute to the incidence of postoperative failures after primary repair. Tendon augmentation procedures, incorporating the use of autograft, allograft and xenograft materials for repair, have been utilized, though incomplete healing and/or graft failure is not uncommon. The documented incidence of repair failures highlights the need for treatments which include stimulators of wound repair and regeneration. Platelet-derived growth factor-BB (PDGF-BB) is a well characterized wound healing protein known to be chemotactic and mitogenic for cells of mesenchymal origin, including tendon (tenoblast/tenocyte) cells. Additionally, PDGF-BB has been shown to improve healing when applied to animal models of tendon injury [2,3]. We hypothesized that recombinant human plateletderived growth factor-BB (rhPDGF-BB) combined with a flowable collagen matrix would improve healing of an acute Achilles tendon injury, as assessed biomechanically and histologically.

Shoulder Tendon Repair Biomechanics Using a Polyurethane Patch in a Chronic Ovine Defect Model

Rotator cuff disorders are one of the most common soft tissue injuries of the musculoskeletal system [1], second only to lower back pain presentations in clinical frequency [2]. Surgical repairs of chronic, massive rotator cuff tears are associated with a high rate of complications, typically by full or partial re-rupture of the repair [3,4]. The literature is replete with clinical retrospective studies or evaluation of cadaveric shoulders [5], however these studies do not address the in vivo healing characteristics of a given surgical repair. The purpose of this study was to quantitatively describe the degree of shoulder healing via biomechanical analyses using an ovine chronic infraspinatus model that was repaired with and without a polyurethane scaffold rotator cuff repair (RCR) patch.Copyright

Kinetic and Biomechanical Testing of Two-Level Cervical Disc Replacement

Cervical disc replacement has become an increasingly common practice in Europe and several disc designs are currently being evaluated via clinical trial for regulatory approval in the United States. The majority of these procedures have been performed at one level in the absence of adjacent level fusion. However, recent conference proceedings have reported on multi-level implantations of these devices. Numerous literature accounts have reported on the in vitro kinetics and kinematics of these devices that have generally shown motion equivalence to the intact spine when implanted at one level. The current study seeks to build upon this previous work by investigating the kinetics associated with two-level disc replacement. In addition, we investigated the implications of a minimally invasive two-level salvage procedure that would involve direct plating over an implanted disc prosthesis while maintaining the disc replacement at an adjacent level.Copyright