Primary Repair for Treating Acute Proximal Anterior Cruciate Ligament Tears: A Histological Analysis and Prospective Clinical Trial

Abstract

Reconstruction surgery for acute proximal anterior cruciate ligament (ACL) tears remains controversial. Recently, ACL primary repair has received increasing attention in ACL treatment. This study aimed to explore the histological characteristics of ACL healing in primary repair and compare its therapeutic and prognostic results with the reconstruction of acute proximal ACL tears. Histological experiments using rabbits and a prospective clinical trial were conducted. We established a rabbit model of ACL primary repair, and histological changes were observed using haematoxylin and eosin (HE) and toluidine blue staining. We performed immunohistochemical analysis of CD34 and S-100 and measured the expression of collagen I and II using qRT-PCR, Western blotting, and immunohistochemistry. The prospective clinical trial involved performing ACL primary repair and reconstruction in patients with acute proximal ACL tears to detect proprioception and evaluate the function of joints. We discovered that primary repair promoted cell proliferation in the tendon-bone transition and ligament portions, reduced osteoarthritis-like pathological changes, and maintained blood vessels and proprioceptors within the ACL. In the clinical trial, primary repair achieved similar therapeutic outcomes, including recovery of knee function and proprioception, in the follow-up period as ACL reconstruction. However, the primary repair had a significantly shorter operative time and lower cost than reconstruction. Therefore, doctors should consider the benefit of primary repair in treating acute proximal ACL tears.

Microanatomical characteristics of arterial vascularization of the anterior cruciate ligament

“…Primary repair promotes cell proliferation in the tendon-bone transitional zone and ligament portions, reduces osteoarthritis-like pathological changes, and maintains blood vessels within the ACL. Histological immunohistochemical research using CD34, the most sensitive endothelial marker of blood vessels, confirmed that the microvessels have a significant effect on tissue healing during the primary repair [18]. Our research performing CD34 immunostaining reported a fine synovial arterial network on the ACL surface from which originated thin vessels for the fibrous tissue of the ligament itself, and penetrating vessels for its femoral attachment and surrounding femoral bony tissue.…”

“…Restoration of native ACL maintains its structural anatomical characteristics, proprioceptive and biomechanical functions. ACL primary repair is safe less invasive procedure, avoids graft-related complications, and faster rehabilitation is possible [18,19]. Preserved periligamentous synovial sheath should be confirmed before the repair because of the mesenchymal stem cells which are evident in the tissue surrounding the blood vessels [20].…”

“…Immunohistochemical studies were performed on 30 isolated ACL specimens obtained from cadavers of persons of both sexes(18 males and 12 females) aged 36-72 years (mean age 58.6 years) during autopsies at the Institute of Pathology of the Medical Faculty of Belgrade, with the approval of the Institute of Pathology. The material for histochemical and immunohistochemical staining methods was prepared in a standard manner at the Institute of Histology and Embryology and the Institute of Pathology of the Faculty of Medicine in Belgrade.…”