Characterisation of morphology in musculus semitendinosus tendon used for anterior cruciate ligament reconstruction: a pilot study

Introduction. Anterior cruciate ligament (ACL) rupture is very common in athletes. In the general population, incidence is
approximately 33 per 100 000 people.
Aim of the study. The aim of the study was the evaluation of morphological changes in the musculus semitendinosus tendon used for the reconstruction of ACL to understand the quality of most common for surgery used material.
Material and methods. The materials were obtained from four ACL autologous hamstring reconstruction surgeries. The tissue
was stained with hematoxyllin and eosin and with immunohistochemical (IMH) staining of PGP9.5, VEGF, collagen I and collagen III. The material was evaluated with semiquantitative method.
Results. Routine staining showed practically unchanged tendon structure, with one exception when sclerotic blood vessels were
observed in endotenon. Collagen III IMH demonstrated moderate to numerous positive collagen fibres in two cases, but in other
two there were only few positive structures seen. Collagen I IMH showed few to moderate number of positive collagen fibres in
all cases. In two cases, moderate number of PGP9.5 positive nerve fibres was observed and in two other cases occasional to few number of positive structures was detected. PGP 9.5 marked higher number of nerve fibres in peritenon than in endotenon.
Numerous VEGF positive endotheliocytes were observed in two cases, but in two other cases VEGF positive endotheliocytes were
occasional.
Conclusions. Tendon of musculus semitendinosus displays two patterns of distribution of tissue ischemia, neuropeptide
containing innervation and collagen I and III. Collagen III is thought to be evaluated as a response of tendon to the ischemia and intensive innervation, while increase of collagen I probably is related to the relatively unchanged vascularity and innervation. The pattern of musculus semitendinosus tendon structural changes seems to be connected to the individual homeostasis in patients persisting before the usage of tendon for the reconstruction.