Semitendinosus tendons in physically immature patients have a lower type I collagen content.

Abstract

To determine the collagen composition of the semitendinosus and quadriceps tendons at different levels of physical maturity. Tissue samples were collected from 70 patients who underwent anterior cruciate ligament or medial patellofemoral ligament reconstruction using the semitendinosus or quadriceps tendon. The samples were immunostained to identify type I and type III collagen. Confocal microscopy and image analysis software were used to determine the percentage composition of collagen types (type I + type III, 100%). Patients were categorized into three groups based on age and epiphyseal patency: immature (<20 years, >1.5 mm), young (<20 years, <1.5 mm) and adult (>20 years). The Mann-Whitney U test was used to analyze differences between the immature and other groups in the semitendinosus tendon group. The percentage of collagen content in the semitendinosus and quadriceps tendons was evaluated based on the patient's maturity level. The median type I collagen content in the semitendinosus tendon was 54.2% (40.9-75.4), 98.9% (81.0-99.6) and 97.0% (40.0-100.0) in the immature (n = 6), young (n = 8) and adult (n = 18) groups, respectively. For the quadriceps tendon, the values were 98.4% (68.9-100.0), 89.1% (68.6-98.9) and 85.6% (72.3-99.6) in the immature (n = 11), young (n = 14) and adult (n = 13) groups, respectively. The semitendinosus tendon in the immature group had significantly lower type I collagen content than in the young and adult groups. Additionally, in the immature group, type I collagen content was significantly lower in the semitendinosus tendon than in the quadriceps tendon. A comparison of collagen composition between the semitendinosus and quadriceps tendons, based on patient maturity level, revealed that the semitendinosus tendon in immature patients had a lower percentage of type I collagen than in mature patients and lower than the quadriceps tendon. Not applicable.