Summary

To evaluate the age-related histological change in the semitendinosus muscle tendon (ST) graft, 47 STs were assessed using hematoxylin and eosin stain, and the number of tenocytes in ST were counted. The number of tenocytes significantly decreased among the immature, young, and adult groups. This study presented the possibility of age-related histological change in the ST graft.

Abstract

Introduction

The anterior cruciate ligament (ACL) reconstruction technique using the semitendinosus muscle tendon (ST) is one of the most major reconstruction methods. Re-rupture has been reported at an incidence of approximately 6–10%, especially for younger and female patients. The cause of the higher incidence of re-rupture in younger patients than that in adult patients is still unknown. In general, the tendon has been reported to become stronger and harder mechanically with age owing to the histological change in which the collagen content and collagen crosslinking of the extracellular matrix of the tendon increase, resulting in a relative decrease in the number of cells per unit area. However, the age-related change of the histological property of ST has not been reported yet. We hypothesized that the age-related histological change occurs in ST and the immature ST may cause re-rupture or residual laxity after ACL reconstruction. The purpose of this study was to evaluate the age-related histological change in the ST graft.

Methods

We assessed 47 patients who underwent ACL or medial patellar femoral ligament reconstruction for a patella dislocation using the ST graft (18 men and 29 women; age, 23.1±11.0 years). The patients were divided into 3 patient groups according to age and the epiphyseal plate of the distal femur and proximal tibia as follows: open epiphyseal plate confirmed on radiography (immature group; n = 3, 3 women, aged 9±1 years), epiphyseal plate closure and age of <20 years (young group; n=21, 10 men and 11 women, aged 16±1 years), and age of =20 years (adult group; n=23, 8 men and 15 women, aged 32±10 years). ST fragments appeared when the ST graft created were evaluated histologically using hematoxylin and eosin stain. The number of tenocytes in the ST was counted in 5 slides from each example, and the average within the groups were calculated. The number of tenocytes between the three groups were analyzed using one-way analysis of variance and the Tukey honestly significant difference test, with the significance level set at p<0.05. The differences in the number of tenocytes according to sex within each group were evaluated using a two-sample t test.

Results

The numbers of tenocytes in the immature, young, and adult groups were 695±167, 363±101, and 286±92 per mm2, respectively. A significant decrease in the number of tenocytes was observed between the immature and young groups and between the young and adult groups (p<0.001 and 0.039, respectively). The number of tenocytes according to sex (males and females) was 350±116 and 374±192 per mm2 in the young group, and 244±72 and 312±96 per mm2 in the adult group, respectively. No significant differences were found in the number of tenocytes according to sex within the young and adult groups (p=0.592 and 0.104 respectively).

Conclusions

This study showed a significant decrease in the number of tenocytes per unit area among the three groups. It presents the possibility of age-related histological change in the ST graft.