Objectives: The indirect head of the rectus femoris (IHRF) tendon has been used as an autograft for segmental labral reconstruction. However, the biomechanical properties and anatomic characteristics of the IHRF, as they relate to surgical applications, have yet to be investigated. The purpose of our study was to quantitatively and qualitatively (1) describe the anatomy of IHRF and its relationship with surrounding arthroscopically relevant landmarks, (2) detail radiographic findings pertinent to IHRF, (3) biomechanically assess segmental labral reconstruction with IHRF including restoration of the suction seal and contact pressures in comparison to iliotibial band (ITB) reconstruction, and (4) assess potential donor site morbidity caused by graft harvesting. Methods: A cadaveric study was performed using 8 fresh-frozen human cadaveric full pelvises and 7 hemi-pelvises. Three-dimensional anatomic measurements were collected using a 3D-coordinate digitizer. Radiographic analysis was accomplished by securing radiopaque markers of different sizes to the evaluated anatomical structures of the assigned hip. Suction seal and contact pressure testing were performed over 3 trials on 6 pelvises under 4 different testing conditions for each specimen: intact, labral tear, segmental labral reconstruction with ITB, and segmental labral reconstruction with IHRF. After IHRF tendon harvest, each full pelvis had both the intact and contralateral hip tested under tension along its anatomic direction to assess potential site morbidity, such as tendon failure or bony avulsion. Results: The centroid and posterior apex of the indirect rectus attachment are respectively located 10.35 ± 2.56 mm and 21.07 ± 6.53 mm posteriorly, 2.47 ± 7.81 mm and 0.66 ± 7.98 mm superiorly, and 5.03 ± 2.82 mm and 22.19 ± 4.36 mm laterally to the 12:30 labral position. Radiographically, the mean distance of the IHRF to the following landmarks was measured as follows: anterior inferior iliac spine (AIIS, 8.81 ± 2.52 mm), direct head of rectus femoris (DHRF, 8.04 ± 3.88 mm), 12-o’clock labrum (14.09 ± 2.77 mm), and 3-o’clock labrum (36.46 ± 4.35 mm). During suction seal testing, both the ITB and IHRF reconstruction groups had significantly lower peak loads and lower energy to peak loads than both intact and tear groups (p=0.013 to 0.017 for all comparisons). There were no significant differences between the reconstruction groups for peak loads, energy, and displacement at peak load. The ITB and IHRF reconstruction groups had greater contact pressures compared to intact labra (100% versus 128.1%, p=0.003; and 100% versus 130.2%, p=0.05, respectively). In 60° of flexion, there were no differences in normalized contact pressure and contact area between ITB or IHRF reconstruction groups (p>0.99). There were no significant differences between intact and harvested specimen groups in donor site morbidity testing. Conclusions: The IHRF tendon is within close anatomical proximity to arthroscopic acetabular landmarks. Harvesting of the IHRF tendon as an autograft does not lead to significant donor-site morbidity in the remaining tendon. Segmental labral reconstruction performed with the IHRF tendon exhibits similar biomechanical outcomes compared to that performed with ITB.
