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BACKGROUND: We have successfully established an animal model of small ear pig in southern Yunnan province with internal tension relieving technique combined with autologous Achilles tendon for anterior cruciate ligament reconstruction, and verified the stability and reliability of the model. However, whether internal tension relieving technique can promote the ligamentalization process of autologous Achilles tendon graft has not been studied. OBJECTIVE: To investigate the differences in the process of ligamentalization between conventional reconstruction and internal reduction reconstruction of the anterior cruciate ligament by gross view, histology and electron microscopy. METHODS: Thirty adult female small ear pigs in southern Yunnan province were selected. Anterior cruciate ligament reconstruction was performed on the left knee joint with the ipsilateral knee Achilles tendon (n=30 in the normal group), and anterior cruciate ligament reconstruction was performed on the right knee joint with the ipsilateral knee Achilles tendon combined with the internal relaxation and enhancement system (n=30 in the relaxation group). The autogenous right forelimb was used as the control group; the anterior cruciate ligament was exposed but not severed or surgically treated. At 12, 24, and 48 weeks after surgery, 10 animals were sacrificed, respectively. The left and right knee joint specimens were taken for gross morphological observation to evaluate the graft morphology. MAS score was used to evaluate the excellent and good rate of the ligament at each time point. Hematoxylin-eosin staining was used to evaluate the degree of ligament graft vascularization. Collagen fibers and nuclear morphology were observed, and nuclear morphology was scored. Ultrastructural remodeling was evaluated by scanning electron microscopy and transmission electron microscopy. RESULTS AND CONCLUSION: (1) The ligament healing shape of the relaxation group was better at various time points after surgery, and the excellent and good rate of MAS score was higher (P < 0.05). Moreover, the relaxation group could obtain higher ligament vascularization score (P < 0.05). (2) The arrangement of collagen bundles and fiber bundles in the two groups gradually tended to be orderly, and the transverse fiber connections between collagen gradually increased and thickened, suggesting that the strength and shape degree of the grafts were gradually improved, but the ligament remodeling in the relaxation group was always faster than that in the normal group at various time points after surgery. (3) The diameter, distribution density, and arrangement degree of collagen fibers in the relaxation group were better than those in the normal group at all time points, especially in the comparison of collagen fiber diameter between and within the relaxation group (P < 0.05). [ABSTRACT FROM AUTHOR]

BACKGROUND: As a dominant breed pig in southwest China, the southern Yunnan small-ear pig has been widely used as an experimental animal in the basic research of other disciplines, but there are still no reports on its application in anterior cruciate ligament reconstruction. OBJECTIVE: To establish a large animal model of the southern Yunnan small-ear pig with anterior cruciate ligament with autologous Achilles tendon was established. METHODS: Twenty adult female Yunnan small-ear pigs were equally randomized into two groups. In the autologous Achilles tendon group, the right knee anterior cruciate ligament was reconstructed with autologous Achilles tendon as a graft, while in the sham-operated group, a similar operation was performed on the right knee without any treatment of the anterior cruciate ligament. General conditions of each pig were observed and recorded before and 12 months after surgery. Ligaments and grafts were taken for gross observation and MAS scoring. Hematoxylin-eosin staining was performed to observe morphological characteristics of ligaments. The staining and arrangement of type I and type III collagen were evaluated by immunohistochemistry. Transmission electron microscopy was used to observe the type, size, diameter, ratio, and distribution of collagen fibers in ligaments. RESULTS AND CONCLUSION: All animals had normal diet and activity, good wound healing, no obvious inflammatory reaction, no local purulent infection, and no significant changes in mental and urinary conditions compared with those before surgery. The reconstructed cruciate ligament of the knee was intact, with no stiffness and normal range of motion. Both the anterior drawer and Lachman tests were negative. Gross observation of the graft: 12 months after surgery, the grafts was in good position, with good integrity, obvious tension, ligament color close to the original anterior cruciate ligament, and complete surface synovial coverage. Most of the intraarticular ligaments in the autologous Achilles tendon group were defined as MAS I type and a few were defined as MAS II type. In the sham-operated group, the intraarticular ligament was defined as MAS I type. Hematoxylin-eosin staining indicated that, 12 months after surgery, collagen fibers in the autologous Achilles tendon group began to appear bundled, isotropic, and uniformly arranged, with more obvious isotropic corrugations, and the nuclei were mainly linear or spindle-shaped, which were similar to those in normal anterior cruciate ligament tissue of the sham-operated group. Immunohistochemistry results indicated that, 12 months after surgery, there was a higher expression of type I collagen and significantly less expression of type III collagen in the reconstructed anterior cruciate ligament in the autologous Achilles tendon group. The degree of type I and type III staining was similar in the two groups. Under the transmission electron microscope, the diameter, arrangement and density of collagen fibers in the reconstructed anterior cruciate ligament of the autologous Achilles tendon group were similar to those of the original anterior cruciate ligament at 12 months after surgery, indicating that the ligament remodeling process had been basically completed in the autologous Achilles tendon group at 12 months after surgery. Through a comprehensive evaluation of animal general conditions, ligament general view, MAS score, hematoxylin-eosin staining, immunohistochemistry, and transmission electron microscopy observation, we successfully established a large animal model of anterior cruciate ligament reconstruction using autogenous Achilles tendon in southern Yunnan small-ear pigs, with good morphological, histological and ultrastructural results. [ABSTRACT FROM AUTHOR]

BACKGROUND: Internal tension-reduction technique is to reconstruct the anterior cruciate ligament through high-strength suture system combined with tendon. It can effectively reduce graft relaxation and frets by sharing the internal load of the knee joint, and has achieved good biomechanical results and clinical efficacy. However, whether it can reduce cartilage degeneration after anterior cruciate ligament reconstruction through stress sharing reduction has not been studied. OBJECTIVE: To investigate the effect of internal tension-reduction technique on articular cartilage degeneration in southern Yunnan small-ear pigs undergoing anterior cruciate ligament reconstruction. METHODS: Ten adult female Yunnan small-ear pigs were selected, and the ipsilateral knee Achilles tendon was taken from the left knee joint for anterior cruciate ligament reconstruction (normal group, n=10), and the ipsilateral knee Achilles tendon from the right knee joint combined with internal tension)reduction and augmentation system for anterior cruciate ligament reconstruction (tension-reduction group, n=10). One year after surgery, the experimental pigs were sacrificed, and the left and right knee cartilage was taken for hematoxylin-eosin staining, Safranin O-fast green staining, Osteoarthritis Research Society International scoring, and immunohistochemistry staining of type II collagen, interleukin-1β, and tumor necrosis factor-alpha in the cartilage. RESULTS AND CONCLUSION: Hematoxylin-eosin staining showed that in the tension-reduction group, there were mild pathologic changes of osteoarthritis, with a low number of empty bone lacunae and no obvious pathological changes such as fibrosis or cell layer breakage; in the normal group, more severe cartilage damage, with an increased number of empty bone lacunae, loss of chondrocytes near the bone and even the formation of fissures. Safranin O-fast green staining indicated that the tension-reduction group had normal cartilage tissue thickness, flat cartilage surface, a neat cell arrangement in a polar pattern, and no swelling or apoptosis, while in the normal group, the thickness of cartilage tissue was obviously thinner, the cell arrangement was disordered with no polarity, the number of cells was reduced, obvious cartilage fractures and cartilage vacuoles formed, and the absence of cells near the central bone was obvious. The Osteoarthritis Research Society International score was significantly lower in the tension-reduction group than in the normal group (P < 0.05). Immunohistochemical findings showed that the protein expression of type II collagen in cartilage tissue of the tension-reducing group was higher than that of the normal group (P < 0.05), and the protein expression of interleukin 1β and tumor necrosis factor ɑ in cartilage tissue was lower than that of normal group (P < 0.05). To conclude, internal tension-reduction technique can delay the degeneration of articular cartilage in Yunnan small-eared pigs following anterior cruciate ligament reconstruction. [ABSTRACT FROM AUTHOR]

BACKGROUND: Arthroscopic anterior cruciate ligament reconstruction is an important treatment for anterior cruciate ligament injury and fracture. Postoperative tendon to bone healing is closely related to the early postoperative rehabilitation and functional recovery of patients. In particular, the time and firmness of tendon to bone healing have become important indicators to evaluate the efficacy of anterior cruciate ligament reconstruction. OBJECTIVE: To summarize the research progress in promoting tendon to bone healing after anterior cruciate ligament reconstruction in recent years, hoping to inspire surgeons and related researchers and better serve basic research and clinical work. METHODS: Using “anterior cruciate ligament, tendon to bone Healing, knee joint, anterior cruciate ligament reconstruction” as English and Chinese search terms, related articles regarding tendon to bone healing were searched by computer in CNKI, WanFang Database, PubMed, and FMRS. The time period of literature retrieval was from January 2011 to December 2021, and systematic generalization, summary and analysis were conducted. The shortcomings and future prospects of the research are also discussed. RESULTS AND CONCLUSION: With the development of medical technology and research level, tendon to bone healing after anterior cruciate ligament reconstruction can be promoted from various aspects such as surgical method improvement, tissue engineering technology and postoperative rehabilitation optimization. However, there are also some limitations, such as a lot of research achievements to promote tendon to bone healing only stay on the animal experiment, especially the experiments of small animals (rat and rabbit). These animals are small in size and extremely different from humans in terms of biological mechanics and body mass; therefore, further research is required to explore whether these study results have the same effect in humans and whether there are long-term adverse reactions or not. There are still few studies on whether the combination of various methods to promote tendon to bone healing can produce a synergistic effect or an inhibitory effect, which may provide new ideas for further research on tendon to bone healing. [ABSTRACT FROM AUTHOR]