The Effects of Tensioning of the Anterior Cruciate Ligament Graft on Healing after Soft Tissue Reconstruction

Abstract

The purpose of this study is to determine the effect of the magnitude of static mechanical tension on the anterior cruciate ligament (ACL) graft at the time of surgery on healing within the graft tunnels. Ninety male rats underwent unilateral ACL resection followed by reconstruction with a soft tissue tendon autograft. The ACL graft mechanical environment was modulated by different ACL graft pretension levels at the time of surgery (no pretension: 0N; moderate tension: 5N; over tension: 10N). External fixators were used to eliminate graft and joint motion during cage activity. Graft–tunnel healing was assessed at 3- and 6-week postoperatively, and articular joint surfaces were assessed at 9 weeks. Our results demonstrate that the ACL graft–tunnel healing was sensitive to different static graft pretension levels as demonstrated by different load-to-failure and stiffness properties among the different pretension levels. Pretensioning the graft to 5N (7–8% of the rat ACL ultimate load to failure) resulted in the best graft–tunnel healing as shown by higher graft–tunnel failure load and stiffness. Higher bone volume fraction was also seen in the 5N group relative to other pretension levels. Histological analysis of the graft–tunnel interface revealed differences in cellularity of the ACL graft between the 5N group and the other two groups. Furthermore, the highest graft pretension level (10N) resulted in loss of proteoglycan content among articular joint surfaces. In conclusion, we found that ACL graft–tunnel healing is sensitive to the magnitude of graft pretension at the time of surgery in a preclinical model of ACL reconstruction with joint immobilization. The combination of high-graft tension and immobilization is also deleterious for the articular surface. Further study is necessary to understand the interaction between the magnitude of graft tensioning and joint motion.

Clinical and Functional Comparison of Two Different Fixation Techniques in Anterior Cruciate Ligament Reconstruction: All-Inside Versus Anteromedial

“…The complication rate of all-inside ACL reconstruction was reported at 5.89% in the literature, which was comparable to the other arthroscopic ACL reconstruction techniques. ( 24 In our study, no major complications required additional surgery or further hospitalization in any group. Similar minor complications were observed in the early follow-up period in both groups (p > 0.05).…”

“…However, this may cause premature graft rupture or possible secondary ligamentization problems. ( 24 …”

“…However, this may cause premature graft rupture or possible secondary ligamentization problems. 24 Although some studies showed that all-inside ACL reconstruction had good to excellent clinical and functional results, few studies compared these results with interference screw fixation. 25 In this study, the authors compared the functional results of the two groups…”

Fibroblasts From Common Anterior Cruciate Ligament Tendon Grafts Exhibit Different Biologic Responses to Mechanical Strain

“…The healing can be affected by forces on the ACL graft. 45,46 Furthermore, the graft tissue undergoes an early complex ligamentization process that includes inflammation, a decrease in graft cellularity (particularly centrally), and a resultant structural weakening of the ACL graft tissue. 56 While some animal studies have demonstrated an early stage of complete graft necrosis, or acellularity, after reconstruction, 3,4,38 others have shown only partial or no acellular necrosis.…”

“…Tendon tissues and ACL grafts are subject to and sensitive to mechanical stimuli after surgery. 37,45,46,70,71 The objective of this study was therefore to evaluate the biologic responses from common tendon fibroblasts used for ACL reconstruction to mechanical strain. Using an in vitro model and tissues derived from the large animal model most commonly used for preclinical ACL studies, we aimed to characterize how different tendon fibroblasts respond to different levels of mechanical strain with respect to proinflammatory mediator and extracellular matrix production, which may alter the local graft environment.…”