Histological analysis of quadriceps tendon collagen composition across physical maturity levels and anatomical layers

To investigate whether patient physical maturity and histological layer influence the collagen composition of the quadriceps tendon (QT).

QT samples were collected intraoperatively from 25 patients undergoing primary anterior cruciate ligament reconstruction using a QT autograft or during knee osteochondral autograft harvesting for osteochondritis dissecans, with one sample obtained from each of the three QT layers. Sections were immunostained for type I and III collagen. The relative area of each collagen type (type I + type III = 100%) was quantified. Patients were grouped as immature, young, or adult based on age and distal femoral physeal patency observed on preoperative magnetic resonance imaging.

The immature (n = 7), young (n = 8), and adult (n = 10) groups had mean ages of 12.3 ± 2.4, 15.9 ± 1.9, and 30.7 ± 8.9 years, respectively. Only body weight was significantly lower in the immature group (p = 0.008). Median type I collagen proportions (%) in the first, second, and third QT layers were 96.3, 79.4, and 77.4 in the immature group; 89.4, 74.8, and 71.4 in the young group; and 92.8, 89.8, and 86.1 in the adult group, respectively. No significant differences in type I collagen content were detected across physical maturity levels within any layer or across tendon layers within any maturity group (p > 0.05).

In this cohort, no significant differences in QT collagen composition were detected across the three anatomical layers or physical maturity levels defined by age and physeal patency.