Collagen Scaffold Supplementation Does Not Improve the Functional Properties of the Repaired Anterior Cruciate Ligament

Department of Orthopaedics, Warren Alpert Medical School, Brown University, Providence, Rhode Island 02903, USA.
Journal of Orthopaedic Research (Impact Factor: 2.99). 06/2010; 28(6):703-9. DOI: 10.1002/jor.21071
Source: PubMed


Primary suture anterior cruciate ligament (ACL) repair was abandoned in favor of reconstruction due to a high rate of clinical failures. However, the insertion of a collagen scaffold loaded with platelets into the wound at the time of suture repair ("enhanced primary repair") has been shown to improve functional healing in animal models. Our objectives were to determine if using a collagen scaffold alone (without platelets) would be sufficient to increase the structural properties of the repaired ACL and decrease postoperative knee laxity compared to suture repair without the scaffold. Eight Yucatan minipigs underwent bilateral ACL transection and suture repair. In one knee, the repair was augmented with a collagen scaffold (SCAFFOLD group) while the other had suture alone (SUTURE group). After 13 weeks of healing, knee joint laxity and the structural properties of the ACL were measured. The addition of the collagen scaffold to suture repair of a transected ACL did not significantly improve the mean anteroposterior knee laxity [SCAFFOLD vs. SUTURE: 6.1 +/- 1.4 vs. 4.4 +/- 2.0 mm (p = 0.07), 8.1 +/- 2.0 vs. 7.6 +/- 2.0 mm (p = 0.66), and 6.2 +/- 1.2 vs. 6.1 +/- 1.8 mm (p = 0.85) at 30 degrees, 60 degrees, and 90 degrees flexion, respectively]. Likewise, there were no significant differences in the structural properties [SCAFFOLD vs. SUTURE: 367 +/- 185.9 vs. 322 +/- 122.0N (p = 0.66) and 90.7 +/- 29.5 vs. 85.0 +/- 30.3N/mm (p = 0.74) for the yield load and linear stiffness, respectively]. The use of a collagen scaffold alone to enhance suture repair of the ACL was ineffective in this animal model. Future work will be directed at stimulating biological activity in the scaffold.

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    • "The Mann-Whitney U-test was used to compare graft slippage, total graft movement, and ultimate tensile strength, and the Kruskal-Wallis test was used to compare BMD differences. The required study sample size was determined using biomechanical data from earlier studies.16,17,18) Results were analyzed using IBM SPSS ver. "
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    ABSTRACT: Background The purpose of this study was to determine the tibial fixation strength provided by different intraosseous soft tissue graft lengths within the tibial tunnel. Methods Porcine tibial bones and digital flexor tendons were used for testing. Bone mineral densities of proximal tibial medial condyles were measured, and two-strand tendon bundles of 8 mm diameter were used. An intraosseous graft length of 2 cm was used in group 1 (n = 10), and a graft length of 4 cm was used in group 2 (n = 10). Tunnels were 4 cm in length and 8 mm in diameter. Tibial fixation was performed using a suture tied around a screw post with a washer and an additionally inserted 7 × 20 mm bioabsorbable screw. After applying preconditioning loading of 10 cycles, 1,000 cycles between 70-220 N were applied at a frequency of 1 Hz. Graft slippage and total graft movement were recorded. Ultimate tensile strength was measured by pull-out testing at an Instron crosshead speed of 1,000 mm/min. Results No significant intergroup difference was found for total graft movement after cyclic loading (slippage in group 1, 1.2 mm and group 2, 1.2 mm, respectively, p = 0.917; and total graft movement in group 1, 3.3 mm and group 2, 2.7 mm, respectively, p = 0.199). However, mean ultimate tensile strength in group 2 was significantly higher than that in group 1 (group 1, 649.9 N; group 2, 938 N; p = 0.008). Conclusions In a porcine model, ultimate tensile strength was greater for a 4 cm long intraosseous flexor tendon in the tibial tunnel. However, no intergroup difference in graft slippage or total graft movement was observed. The results show that a 2 cm intraosseous graft length in the tibial tunnel is safe and has sufficient strength (> 450 N) for adequate rehabilitation after anterior cruciate ligament reconstruction.
    Full-text · Article · Jun 2014 · Clinics in orthopedic surgery
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    • "This important clinical challenge has promoted research using numerous animal models including goats [3], sheep [4], rabbits [5], Yucatan minipigs [6], and dogs [7]. The wealth of translational research on this topic aims at developing optimal animal models that closely mimic the condition in humans and would thus help define, develop, and compare new treatment strategies for successful and efficient replacement of the ACL. "
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    ABSTRACT: Various methods regarding allograft knee replacements have been described. The animal models, which are generally used for this purpose include sheep, dogs, goats, and pigs, and accrue significant costs for study protocols. The authors herein describe an efficient and cost-effective model to study either native or tissue-engineered allografts for anterior cruciate ligament (ACL) replacement in a New Zealand rabbit model with the potential for transgenic and cell migration studies. ACL reconstructions were performed in rabbits under general anesthesia. For fresh allograft implantations, two animals were operated in parallel. Each right extensor digitorum longus tendon was harvested and prepared for implantation. After excision of the ACL, tibial and femoral bone tunnels were created to implant each graft in the native ACL position. During a 2-year period, the authors have successfully undertaken this surgery in 61 rabbits and have not noticed any major complications attributed to this surgical technique. In addition, the authors have observed fast recovery in the animals postoperatively. The authors recommend this surgical procedure as an excellent model for the study of knee surgery.
    Full-text · Article · Aug 2013 · Journal of Orthopaedic Surgery and Research
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    • "Collagen was one of the first natural scaffold materials to be used in ligament reconstruction as it is the natural component of the native tissue and has great ability to support ligament fibroblast growth under static tension [44]. However, collagen scaffold alone was found to be ineffective to enhance suture repair of the ACL [45]. Fibroblast-seeded collagen scaffolds, on the other hand, were more effective in ligament regeneration [44, 46–48]. "
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    ABSTRACT: Ligaments are dense fibrous connective tissues that connect bones to other bones and their injuries are frequently encountered in the clinic. The current clinical approaches in ligament repair and regeneration are limited to autografts, as the gold standard, and allografts. Both of these techniques have their own drawbacks that limit the success in clinical setting; therefore, new strategies are being developed in order to be able to solve the current problems of ligament grafting. Tissue engineering is a novel promising technique that aims to solve these problems, by producing viable artificial ligament substitutes in the laboratory conditions with the potential of transplantation to the patients with a high success rate. Direct cell and/or growth factor injection to the defect site is another current approach aiming to enhance the repair process of the native tissue. This review summarizes the current approaches in ligament tissue engineering strategies including the use of scaffolds, their modification techniques, as well as the use of bioreactors to achieve enhanced regeneration rates, while also discussing the advances in growth factor and cell therapy applications towards obtaining enhanced ligament regeneration.
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