ePoster #721 - ISHA Annual Scientific Meeting 2016

Are Personalized and Sport-Specific Preoperative Plans Needed for Surgical Treatment of Femoro-Acetabular Impingement?

Rikin Patel, MS, Houston, TX UNITED STATES
Philip C. Noble, PhD, Houston, TX UNITED STATES
Joshua Choi, BS, Houston, TX UNITED STATES
Ryan Blackwell, BS, Houston, TX UNITED STATES
Sabir K. Ismaily, PhD, Houston, TX UNITED STATES
Joshua David Harris, MD, Houston, TX UNITED STATES

The Institute of Orthopedic Research and Education , Houston, TX, UNITED STATES

FDA Status Not Applicable

Summary: The location of the femoro-acetabular impingement site varies with different athletic activities to the extent that individualized preoperative planning for FAI surgery should be considered in lieu of a standardized operative plan for bony resection.

Background: In the athletic patient, a common cause of recurrence of symptoms after FAI surgery is under-correction of the initial deformity. This may occur if the surgical procedure fails to sufficiently increase the clearance between the femur and the acetabulum at the point of original impingement. Conceivably, this location could vary with the kinematic demands of each sport and the bony anatomy of each individual patient.

Research Questions: Does the anatomic location of the site of impingement between the femur and the acetabulum vary with different sporting activities? Will one standardized plan for bony resection meet the needs of the majority of patients?

Methods: 3D computer models were reconstructed from CT scans of ten (10) male hips (alpha angle: 56.2°±4.2°; lateral CE angle: 37.9°±5.9°) without degenerative arthrosis. Using the conventions defined by the International Society of Biomechanics, each hip model was placed initially in 90° of flexion and neutral abduction/adduction and then internally rotated until impingement, as detected by collision detection routines. The location of the point of impingement was measured circumferentially using the original clock-face convention (acetabular notch 6:00) and radially using the distance from the acetabular rim and from the head/neck junction. Each hip model was internally rotated an additional 10°, and the extreme radial/circumferential locations of the bony interference volume were recorded, indicating of the width of resection required for 10° of hip motion beyond impingement. The ROM procedure was repeated to simulate two high demand sporting activities: 1) Pitching/stooping (100° flexion; 5° adduction; 10-30° internal rotation) and 2) Hockey goalie ”butterfly slide” (75° flexion; 25° abduction; 20-60° internal rotation). The radial/circumferential coordinates recorded for each activity were compared using standard statistical methods.

Results: For IR/90° flexion, the average location of the impingement point was 3:06±0:41hrs on the femur (range: 2:07 to 4:01) and 2:02±0:31 on the acetabulum (range: 1:08 to 2:20). With stooping/pitching, the femoral impingement point moved to 3:36±0:27hrs (p=0.027) whereas the acetabular location was unchanged (2:05±0:22; p=0.701). Conversely, in the goalie maneuver, the impingement point moved vertically on both the femur (1:59±0:49; p=0.002) and the acetabulum (1:26±0:37; p=0.014). There was no difference between the three activities in terms of the radial location of the impingement points on the femur and the acetabulum, but` the location of the contact point on the femoral neck was highly variable (range: 2-20mm). When internal rotation was increased by 10°, the same differences in impingement location remained, however, the area of resection extended from a single point to an arc of 1:56±0:41hrs on the femur and 1:08±0:31hrs on the acetabulum with an average width of 7.4±1.8mm.

Conclusions: The location of the femoro-acetabular impingement site varies with different athletic activities. Even larger variations are observed between patients to the extent that a generic plan for osteochondroplasty would need to prescribe bone resection from 0 to 4:30hrs on the femur and 0:30 to 3:15 on the acetabulum to accommodate normal variation in hip anatomy. In view of these findings we recommend use of individualized preoperative planning for FAI surgery.