EP2.20 Utility of CT navigation hip arthroscopic surgery for secondary femoroacetabular impingement after rotational acetabular osteotomy Open Access

Introduction: Despite secondary FAI after pelvic osteotomy for dysplasia has recently been recognized, surgical strategy has not been established. We have been experienced computer-assisted hip arthroscopic osteochondroplasty for secondary FAI after rotational acetabular osteotomy. It is essential to identify the resection region before and during surgery. We introduce preoperative CT-based virtual surgery and CT-guide arthroscopic surgery.

Method: Firstly, apply a 3D bone model based on preoperative patient-specific CT using Zed Hip (Lexi, Tokyo). A dynamic simulation is then performed to determine whether the secondary FAI is due to the pincer lesion alone or combined with cam-type FAI. Specifically, the maximum internal rotation angle at 45 degrees, 70 degrees, and 90 degrees of flexion is identified as the impingement point. The acetabular impingement region is virtually resected and dynamic simulation until appropriate improvement of the hip internal rotation angle, in cases with cam deformity, the bony bump of the femoral neck is also virtually trimmed. After achieving a sufficient range of motion, bone models before and after the virtual surgery are imported into the CT navigation system to perform accurate arthroscopic surgery.

Result: Comparative verification of dynamic analysis using a postoperative CT showed equivalent to the preoperative planning, and the postoperative clinical outcomes were great.

Discussion: The anatomical positional relationship of the hip joint partially changes after pelvis osteotomy, and the resection region becomes complicated, making that difficult to confirm those areas via arthroscopic. Particularly carefully evaluating the presence of cam deformity is important. Accurate surgery is possible by identifying the impingement region using preoperative dynamic simulation and performing surgery with CT navigation.