Active_comparator: Microfracture

As per current standard of care for focal articular cartilage lesions of the acetabulum, the unstable cartilage will be debrided and removed from the subchondral bone using a mechanical shaver until a stable margin is obtained. A ring curette will be used to remove the calcified cartilage layer and create a border of healthy cartilage tissue that can support the marrow clot. Through the mid-anterior portal, specialized 90˚ awls will then be placed with the tip perpendicular to the subchondral bone of the acetabulum, and a mallet will be used to penetrate the subchondral bone with perforations 3 mm deep to access the bone marrow elements. This is done until the defect is homogeneously covered with micro-perforations 2-3 mm apart.

Experimental: Autologous matrix-induced chondrogenesis (AMIC)

Those allocated to the AMIC treatment group will also receive microfracture. Once the walls of the debrided lesion are confirmed to be stable with a probe, the exact size of the defect will be measured for templating of the scaffold. The dry Chondro-Gide® matrix will be prepared by cutting it to 10% smaller than the focal defect (as it increases in size about 10% after moistening). Once the cartilage lesion is dried manually, the implant will then be secured to the defect in a press-fit fashion to the surrounding cartilage. Manual pressure is then applied to secure the implant into the defect and the hip is released from traction and rotated to facilitate further fixation of the graft. Traction is then applied to arthroscopically confirm position and fixation of the implant.