Summary
Verify how much and how the structural composition of the ACL repaired tissue is different from the reconstructed one and which of these is more like to healthy tissue.
Abstract
Background
The healing process of an anterior cruciate ligament (ACL) injury is not yet fully understood. Unlike extra-articular ligaments, whose repair occurs early, the intra-articular environment of the cruciate often prevents this process.
Purpose
Verify how much and how the structural composition of the ACL repaired tissue is different from the reconstructed one and which of these is more like to healthy tissue.
Methods
Three different groups were included in this study. In 15 patients, who previously underwent ACL repair (ACL REP), in-office needle arthroscopic second look was performed between 8 and 12 months postoperatively and a biopsy specimen of the repaired ACL was performed. The second group involved 10 patients, who had previously undergone ACL reconstruction (ACL REC) with hamstrings. A biopsy specimen was also taken in these patients, who underwent subsequent knee arthroscopy for reasons other than graft failure. The third control group (CTRL) consisted of 15 specimens taken from healthy ACL cadaver knees. A gene expression analysis of Collagen I (Coll I), Collagen III (Coll III), Collagen I-III ratio, alpha smooth muscle actine (a-SMA) and p16 in the three groups was performed.
Results
Gene expression analysis of Coll I showed a statistically significant difference between both the CTRL group and ACL REC group and between ACL REP group and ACL REC group (p = 0.0027). A statistically significant difference in both the Coll I/III ratio (p= 0.0003) and a-SMA expression (p = 0.001) was also found between the groups CTRL and ACL REC and between the groups ACL REP and ACL REC.
Conclusions
The molecular analysis of a repaired ACL in terms of mRNA expression is very similar to that of a healthy ACL cadaver knee. This similarity was observed in collagen quality, degree of activation of the cellular differentiation process (a-SMA), and degree of cellular senescence (p16) in the tissue samples examined. In contrast, the reconstructed ACL exhibits a completely different profile than a healthy ligament.