Anterior Cruciate Ligament Mechanoreceptors and their Potential Importance in Remnant-Preserving Reconstruction: A Review of Basic Science and Clinical Findings

Abstract

Mechanoreceptors, within the anterior cruciate ligament (ACL), are believed to have importance in proprioception, contributing to dynamic knee stability. The potential for reinnervation of the ACL graft is one of the proposed advantages of remnant-preserving reconstruction. The aim of this review is to summarize advances in the basic science underpinning this function, alongside recent clinical studies, to define the current role for remnant-preservation.A comprehensive systematic review was performed using PubMed and Medline searches. Studies were analyzed with particular focus placed on the methodology used to either identify mechanoreceptors or test proprioception.Contemporary work, using immunohistological staining, has shown mechanoreceptors primarily within proximity to the bony attachments of the ACL (peripherally in the subsynovial layer). The number of these receptors has been shown to decrease rapidly, following rupture, with adhesion to the posterior cruciate ligament slowing this decline. Recent studies have shown proprioceptive deficits, in both the injured and contralateral knees, with the clinical relevance of findings limited by testing methodology and the small differences found. The advantages of remnant-preservation, seen primarily in animal studies, have not been shown in systematic reviews or meta-analysis of clinical studies.The potential for reinnervation of the graft is likely time-dependent and reliant on continued loading of the remnant. Therefore, current clinical use and future research should focus on preserving remnants within 6 months of injury that remain loaded by adherence to the posterior cruciate ligament. Subsequent testing should account for central neurological changes and focus on clinically relevant outcomes.

Anterior cruciate ligament remnant‐preserving and re‐tensioning reconstruction: a biomechanical comparison study of three different re‐tensioning methods in a porcine model

“…Mechanoreceptors for proprioception can be stimulated by length changes, and the rate of changes in tension. [1,[15][16][17][18]. Furthermore, the strength of the remnant tissue in the early phase after reconstruction may be beneficial for rehabilitation and early incorporation [19].…”

Influence of Anterior Cruciate Ligament Surgery with Semitendinosus and Gracilis Graft on Static Postural Balance at 3 Months Postoperatively: Randomized Controlled Study

“…Postural alteration following ACL surgery may be primarily related to proprioceptive system involvement as well as the muscular system resulting in increased COP displacement during postural testing. Kosy et al [31] published a systematic review in 2017 in order to make an inventory in the field of proprioception in relation to the rupture of the ACL and its repair. Schulz and his collaborators are the first to highlight the presence of mechanoreceptors in the ACL in 1986.…”

“…The purpose of the surgery is to tend to recover this proprioception by replacing the native ACL by a graft that does not have the same mechanoreceptors. The phenomenon of ligamentization is a long process extending up to 1 year when it is estimated that at 6 months the neo-ligament seems identical to an ACL [31].…”

A review on finite element analysis of the anterior cruciate ligament reconstruction

“…Anterior Cruciate Ligament (ACL) injuries are common in accidents and sports activities and its reconstruction is necessary to restore the static and dynamic stability of the knee. It is also performed in patients with functional instability following ACL injury, resulting in surgical repair or reconstruction [1][2][3]. The yearly incidence rate is of over two million injuries worldwide [4].…”