Histological changes of semitendinosus autograft after anterior cruciate ligament reconstruction in an immature rabbit model

Journal of Experimental Orthopaedics, Aug 2015

Introduction The anterior cruciate ligament (ACL) injury is one of the most common in the knee. Tendons can be used as alternative grafts for ACL repair, with tendon “ligamentization” often reported in literature. The purpose of this study was to evaluate the morphological and histological changes occurring in a semitendinosus tendon (ST) during ACL reconstruction in growing rabbits. Materials and methods Twenty-one 8-week-old New Zealand white rabbits, weighing about 1500 g underwent reconstructive surgery on the right knee. In two cases the left knee was used to verify the normal microstructure of the ACL and ST in rabbits. The rabbits were then randomly divided into seven groups and sacrificed at 1, 4, 6, 8, 12, 24 and 48 weeks after surgery. The specimens were evaluated under light microscopy to analyze the changes in the intra-articular tract of the graft. The evidence of necrosis, neovascularization and organization of the collagen fibers were investigated. Results One month after surgery, numerous disorganized fibroblasts and collagenous fibers were identified. A marked reduction of cellular necrosis was observed in the early phase of the neo-ligament healing process. After 4 weeks, these fusiform-like cells became more rounded. By 8 weeks, the collagen fibers had become aligned in parallel with newly formed capillaries and highly differentiated fibroblasts. At 24 and 48 weeks the transplanted tendon differed histologically from both tendon and ligament. Conclusions The data of the present study showed that ligamentization did not occur until at least 24 months post-operatively and, during healing, the grafted tendon assumed a unique micro-architecture that was a middle between a tendon and a ligament. The ACL reconstruction in pediatric age has become more frequent in these past recent years. The use of semitendinosus graft with preservation of its distal attachment should be the gold standard in skeletally immature patients.

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Histological changes of semitendinosus autograft after anterior cruciate ligament reconstruction in an immature rabbit model

Giordano et al. Journal of Experimental Orthopaedics Histological changes of semitendinosus autograft after anterior cruciate ligament reconstruction in an immature rabbit model Marco Giordano 0 2 Francesco Falciglia 0 2 Alessia Poggiaroni 0 2 Angelo Gabriele Aulisa 0 2 Pietro Savignoni 0 2 Vincenzo Guzzanti 0 1 2 0 Orthopaedics and Traumatology Division, Bambino Gesù Children's Hospital, Institute of Scientific Research , Piazza San Onofrio 4, I-00165 Rome , Italy 1 University of Cassino (FR) , Cassino , Italy 2 Orthopaedics and Traumatology Division, Bambino Gesù Children's Hospital, Institute of Scientific Research , Piazza San Onofrio 4, I-00165 Rome , Italy Introduction: The anterior cruciate ligament (ACL) injury is one of the most common in the knee. Tendons can be used as alternative grafts for ACL repair, with tendon “ligamentization” often reported in literature. The purpose of this study was to evaluate the morphological and histological changes occurring in a semitendinosus tendon (ST) during ACL reconstruction in growing rabbits. Materials and methods: Twenty-one 8-week-old New Zealand white rabbits, weighing about 1500 g underwent reconstructive surgery on the right knee. In two cases the left knee was used to verify the normal microstructure of the ACL and ST in rabbits. The rabbits were then randomly divided into seven groups and sacrificed at 1, 4, 6, 8, 12, 24 and 48 weeks after surgery. The specimens were evaluated under light microscopy to analyze the changes in the intra-articular tract of the graft. The evidence of necrosis, neovascularization and organization of the collagen fibers were investigated. Results: One month after surgery, numerous disorganized fibroblasts and collagenous fibers were identified. A marked reduction of cellular necrosis was observed in the early phase of the neo-ligament healing process. After 4 weeks, these fusiform-like cells became more rounded. By 8 weeks, the collagen fibers had become aligned in parallel with newly formed capillaries and highly differentiated fibroblasts. At 24 and 48 weeks the transplanted tendon differed histologically from both tendon and ligament. Conclusions: The data of the present study showed that ligamentization did not occur until at least 24 months post-operatively and, during healing, the grafted tendon assumed a unique micro-architecture that was a middle between a tendon and a ligament. The ACL reconstruction in pediatric age has become more frequent in these past recent years. The use of semitendinosus graft with preservation of its distal attachment should be the gold standard in skeletally immature patients. Immature animal models; Anterior cruciate ligament; Ligamentization; Intra-articular tract; Semitendinosus tendon - Background Anterior cruciate ligament (ACL) injuries in the skeletally immature athletes have been reported with increasing frequency, accounting for 31 % of the total knee injuries (Shea et al. 2004). ACL reconstruction in adolescents is still discussed. Non operative management is an appealing option in reason of the risk of physeal damage, however the recent literature uniformly indicates that conservative treatment of ACL tears in children results in a higher rate of instability that may progress to intraarticular damage, including meniscal tears (Fabricant et al. 2013; Henry et al. 2009; Ramsky et al. 2013). For this reason, there has been an increasing interest in the early operative management to restore stability in skeletally immature knees (Falciglia et al. 2014). Several aspects of the biology and biomechanics of the reconstruction of the anterior cruciate ligament have been underlined, but only © 2015 Giordano et al. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. few studies have been conducted on the process of ligamentization in childhood. Although tendons have different both biological and histological features compared to ligaments, numerous studies have reported the use of tendons for ligamentous repair. One of the still debatable questions is to clarify how the so-called “neo-ligament” really progressively loses its tendon specific biological characteristics exhibiting ligamentous histological properties. While there has been a wide number of studies exploring the various aspects of ACL reconstruction in adults only limited data are available regarding the human or animal tendon graft healing process in skeletally immature patients. In the early twentieth century Roux, Bertocchi-Bianchetti, and Vallone published the first experimental studies on the histological characteristics of tendon grafts (Amiel et al. 1986). Later, (...truncated)


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Marco Giordano, Francesco Falciglia, Alessia Poggiaroni, Angelo Aulisa, Pietro Savignoni, Vincenzo Guzzanti. Histological changes of semitendinosus autograft after anterior cruciate ligament reconstruction in an immature rabbit model, Journal of Experimental Orthopaedics, 2015, pp. 17, 2, DOI: 10.1186/s40634-015-0033-1