Ultrastructural morphology of anterior cruciate ligament stump in ACL injured patients and semitendinosus graft used for ACL reconstruction with the help of electron microscopy and light microscopy; a comparative study
ACL injury is very common. ACL reconstruction is one of the commonest surgeries done for ACL injuries. Semitendinosus graft (STG) is often used to replace the torn ACL. It is pertinent to find out the structural differences between ACL and STG.
Aims and objectives: Tissues from ACL and STG were subjected for light microscopy (LM) and transmission electron microscopy (TEM) to study the structural details.
A prospective study was conducted between July 2012 and May 2014 with 38 patients (36 male and 2 female), mean age 27.56 years (range 21 to 37 years) who underwent arthroscopic ACL reconstruction for ACL injury. Tissue samples were taken from ACL and STG from each patient. Each sample was subjected for LM and TEM study for the histology ( using Hematoxylin and Eosin, Van Verhoeff, Masson Trichrome stains) and immunohistochemistry (using CD 34, Neurofilament protein antibody (NF) stains); and for ultrastructure respectively.
The mean density of blood vessels in ACL and STG were 9.77 per mm2 and 4.59 per mm2 respectively and the difference was significant (p < 0.01). However, there was no association between the duration of injury, sex and density of blood vessels. The mean density of nerve fibers were positive in 44.72 % (in 17 patients) and 7.89 % (in 3 patients) in ACL and STG respectively. And the mean density of fibroblasts were 37.14 per mm2 and 20.88 per mm2 in ACL and STG respectively and the difference was significant (p <0.01). The mean fibril – interstitium ratio in ACL was 54.11% and 74.63 % in STG and the difference was significant (p < 0.01). The mean collagen fibrils were 64.99 mm and 72.66 mm in ACL and STG respectively and the difference was not significant (p= 0.157).
Despite ultrastructural differences between the ACL and STG, the stump of ACL being more vascular and rich in nerve cells, needs to be preserved during ACL reconstruction surgery.