Biomechanical analysis of the crural fascia and investigation of its role in the stress reactions occurring in the anterior compartment

The aim of this study was to determine whether the anatomical and biomechanical characteristics of the crural fascia in the anterior compartment of the leg indicate the levels of anterior tibial stress injury, which has been shown to be the cause of pain in exercise beginners. In 18 cadaveric legs (11 male, 7 female, 8 bilateral, 2 right) fixed with 10% formalin, the crural fascia between the head of fibula and the intermalleolar line was released from the line of attachment to the anterior intermuscular septum of leg laterally and deviated medially. From proximal to distal, 4 equal parts were seperated as Q1, Q2, Q3, Q4. Horizontal-vertical samples of 0.5 cm width and 2.5 cm length were taken from the parts. In addition, vertical samples were taken from the intersection of the crural fascia and the periosteum of the tibia. Biomechanical data were obtained from force-deformation and stress-strain curves with the Stress-Test Device. Non-normally distributed data were analyzed by Friedman's test, Mann Whitney U, Wilcoxon signed-rank test, Spearman's rho correlation coefficient. Image-J software was used to calculate the area percentage of muscle fiber attachment area and fiber angulation. Young's modulus values of vertical samples of crural fascia were significantly higher than horizontal ones at all levels. The young's modulus value of the horizontal samples of the four parts increased from proximal to distal, while that of the vertical samples decreased (p<0.05). There was no significant diference according to gender and side. The muscle attachment area was almost always in the proximal 1/3, but not in Q3 and Q4. The angulation of the most prominent fibers of the crural fascia relative to the margo anterior of the tibia followed a course approaching horizontal from proximal to distal. This angulation was from Q2 towards the distal: 14.61±5.29° for Q2, 27.15±5.99° for Q3, 55.13±8.99° for Q4 and 86.82±5.99° for RES. In the proximal part, it was observed that muscle fibers were attached to the crural fascia, a septum was extend from the crural fascia between the muscles, an intermuscular septum almost always located in the sagittal plane with variable dimensions was attached to the crural fascia, strong fibrous septums beginning from the crural fascia at the level of the retinaculum proceeded in the sagittal plane between the tendons and attached to the deep bone periosteum. It was observed that the force transferred to the crural fascia was less elastically transferred proximally in the vertical plane and more elastically transferred distally. In contrast, the portion of this force distributed in the horizontal plane was found to be transferred more elastically proximally but less elastically distally. As we approached the distal part of the crural fascia, we thought that the force that the vertically oriented fibers should assume may be gradually decreasing. Our findings indicating differences in the biomechanical properties of the crural fascia according to the levels of anterior tibial stress injuries in the literature support the idea that the role of fascia properties in these injuries may be more than known. Keywords: Crural fascia; dreaded black line; anterior tibial stress injury; biomechanics; stress fracture