Effect of anterior cruciate healing on the uninjured ligament insertion site

Department of Orthopaedic Surgery, Children's Hospital, Boston, MA 02115, USA.
Journal of Orthopaedic Research (Impact Factor: 2.99). 01/2012; 30(1):86-94. DOI: 10.1002/jor.21498
Source: PubMed


The effect of anterior cruciate healing on the uninjured ligament insertion site after enhanced suture repair with collagen-platelet composites (CPC) has not yet been defined. In this study, we hypothesized that fibroblasts and osteoclasts would participate in generating histologic changes in insertion site morphology after transection and bioenhanced repair of the ACL, and that these changes would be age-dependent. Skeletally immature, adolescent, and adult Yucatan mini-pigs underwent ACL transection and bioenhanced suture repair. The histologic response to repair of the insertion site was evaluated at 1, 2, 4, and 15 weeks. In young and adolescent animals treated with bioenhanced suture repair with CPC, changes in the insertion site included: (1) fibroblastic proliferation with loss and return of collagen alignment in the fibrous zone; (2) osteoclastic resorption within fibrocartilage zones at 2-4 weeks; and (3) partial reappearance of fibrocartilage zones at 15 weeks. In adult animals; however, degenerative changes were noted by 15 weeks: (1) loss of parallel arrangement of collagen fibers in the fibrous zone; and (2) increasing disorganization and loss of columnation of chondrocytes in the fibrocartilage zone. These results suggest that fibroblasts and osteoclasts mediate histologic changes at the insertion site during bioenhanced suture repair of the ACL which may prevent insertion site degeneration, and that the magnitude of these changes may be a function of skeletal maturity.

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Available from: Martha M Murray, Mar 27, 2015
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    • "Also, biomechanical testing showed that failure to load was significantly higher in the augmentation group compared with the conventional reconstruction group. Histological examination of human ACL remnant demonstrates an intrinsic potential for healing [25], with an intact vascular support provided by the synovial layer and an ability for fibroblasts to synthesize collagen [26]. Murray and Spector [17] demonstrated that cells in the human ACL retain their ability to migrate into an adjacent scaffold in vitro, four weeks after a complete rupture. "
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    ABSTRACT: Purpose The aim of this study was to investigate the histological features of the remaining fibers bridging femur and tibia in partial ACL tears. Methods 26 ACL remnants were harvested from patients who had arthroscopic criteria concordant with a partial tear. Histological analysis includes cellularity, blood vessel density evaluation and characterization of the femoral bony insertion morphology. Immunohistochemical studies were carried out to determine cell positive for α-smooth actin and for mechanoreceptors detection. Results In this samples, a normal femoral insertion of the remnant was present in 22.7% of the cases. In 54 % of the samples, substantial areas of hypercellularity were observed. Myofibroblasts were the predominant cell type and numerous cells positive for α-smooth actin were detected at immunostaining. Blood vessel density was increased in hypercellularity areas and in the synovial sheet. Free nerve endings and few Golgi or Ruffini corpuscles were detected in 41 % of the specimens. The cellularity was correlated to the time between injury to surgery (p = .001). Conclusion Competent histological structures including a well vascularized synovial sheet, numerous fibroblasts and myofibroblasts and mechanoreceptors were found in ACL remnants. These histological findings bring additional knowledge towards the preservation of the ACL remnant in partial tears when ACL reconstruction or augmentation is considered.
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    ABSTRACT: This chapter focuses on the use of biomaterials, nano-scale features, and scaffold enhancements for the construction of successful biological scaffolds for ligament regeneration. Ligament composition, structure, physiology, function, and properties are first introduced in order to identify key design parameters for scaffold design. The second part of the chapter describes injury, healing, and treatment of the anterior cruciate ligament focusing on current techniques utilized clinically for reconstruction. Subsequent content focuses on the materials, techniques, and features being used to develop scaffolds for ligament regeneration. Finally, the approaches (e.g., addition of growth factors and platelet rich plasma, and induced mechanical strain) which have been used to enhance engineered scaffolds for ligament regeneration are discussed.
    No preview · Chapter · Jul 2013
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    ABSTRACT: Background The response of the joint to anterior cruciate ligament (ACL) injury has not been fully characterized. In particular, the characterization of both catabolic factors, including interleukin-6 (IL-6), interleukin-8 (IL-8), and markers of ongoing tissue damage (CRP), and anabolic factors, including vascular endothelial growth factor (VEGF), transforming growth factor β-induced (TGFβI), and the presence of CD163+ macrophages, have not been well defined. In this study, we hypothesized ACL injury would catalyze both catabolic and anabolic processes and that these would have different temporal profiles of expression. Methods Adolescent Yucatan minipigs were subjected to ACL transection. Within the joint, gene expression levels of IL-6, IL-8, VEGF, and TGFβI were quantified in the synovium, ligament, and provisional scaffold located between the torn ligament ends at days 1, 5, 9, and 14 post-injury. Macrophage infiltration was also assessed in the joint tissues over the two week period. Serum C-reactive protein (CRP) levels were measured at multiple time points between 1 hour to 14 days after injury. Results Increases in IL-6 and IL-8 gene expression peaked at day 1 after injury in the synovium and ligament. CRP levels were significantly increased at day 3 before returning to pre-injury levels. VEGF and TGFβI gene expression did not significantly increase until day 9 in the synovium and were unchanged in the other tissues. CD163+ macrophages increased in the ligament and synovium until day 9. Conclusion Taken together, these results suggest that the response within the joint is primarily catabolic in the first three days after injury, switching to a more anabolic phase by nine days after injury. The effect of medications which alter these processes may thus depend on the timing of administration after injury.
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