Scott Kling1, Michael R Karns2, Jeremy Gebhart1, Christos Kosmas1, Mark Robbin1, Shane J Nho3, Asheesh Bedi4, Michael J Salata1. 1. Department of Orthopaedic Surgery, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA. 2. Department of Orthopaedic Surgery, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA Michael.karns@uhhospitals.org. 3. Rush University Medical Center, Chicago, Illinois, USA. 4. Department of Orthopaedic Surgery, University of Michigan, Ann Arbor, Michigan, USA.
Abstract
BACKGROUND: The majority of rim recession for femoroacetabular impingement (FAI) is performed anteriorly and has traditionally been assessed by the lateral center-edge (CE) angle, which correlates most closely with lateral coverage. The radiographic false-profile view permits measurement of anterior coverage via the anterior CE angle and more closely correlates with anterior coverage. PURPOSE: To answer the following questions: (1) How does incremental anterior rim recession change lateral and anterior CE angles? and (2) Can these changes be predicted by a formula? STUDY DESIGN: Descriptive laboratory study. METHODS: Twelve cadaveric hips were dissected free of soft tissue to expose the anterior acetabular rim. Incremental resections of 2.5 mm (range, 0-10 mm) were performed from the 12- to 3-o'clock position using a Dremel rotary tool. Anteroposterior hip and false-profile radiographs were obtained at each interval using a fluoroscopic C-arm. The lateral and anterior CE angles were measured by 3 orthopaedic surgeons. RESULTS: The average preresection lateral CE angle was 35.1°, and the mean decrease in lateral CE angle from 0 to 10 mm was 9.9°; the average preresection anterior CE angle was 38.4° and the mean decrease in anterior CE angle from 0 to 10 mm was 18.2°. The anterior CE angle decreased by a factor of 1.9 when compared with the lateral CE angle (P = 2 × 10(-7)). The lateral CE angle decreased by approximately 1° (1.0°) per millimeter of rim recessed. The anterior CE angle decreased by approximately 2° (1.8°) per millimeter of rim recessed. CONCLUSION: The lateral CE angle should not be extrapolated to reflect anterior acetabular coverage. The anterior CE angle is a superior marker and predictably decreases with rim recession at double the rate of the lateral CE angle. CLINICAL RELEVANCE: The false-profile view is recommended in the perioperative workup for all patients undergoing arthroscopic treatment of pincer impingement.
BACKGROUND: The majority of rim recession for femoroacetabular impingement (FAI) is performed anteriorly and has traditionally been assessed by the lateral center-edge (CE) angle, which correlates most closely with lateral coverage. The radiographic false-profile view permits measurement of anterior coverage via the anterior CE angle and more closely correlates with anterior coverage. PURPOSE: To answer the following questions: (1) How does incremental anterior rim recession change lateral and anterior CE angles? and (2) Can these changes be predicted by a formula? STUDY DESIGN: Descriptive laboratory study. METHODS: Twelve cadaveric hips were dissected free of soft tissue to expose the anterior acetabular rim. Incremental resections of 2.5 mm (range, 0-10 mm) were performed from the 12- to 3-o'clock position using a Dremel rotary tool. Anteroposterior hip and false-profile radiographs were obtained at each interval using a fluoroscopic C-arm. The lateral and anterior CE angles were measured by 3 orthopaedic surgeons. RESULTS: The average preresection lateral CE angle was 35.1°, and the mean decrease in lateral CE angle from 0 to 10 mm was 9.9°; the average preresection anterior CE angle was 38.4° and the mean decrease in anterior CE angle from 0 to 10 mm was 18.2°. The anterior CE angle decreased by a factor of 1.9 when compared with the lateral CE angle (P = 2 × 10(-7)). The lateral CE angle decreased by approximately 1° (1.0°) per millimeter of rim recessed. The anterior CE angle decreased by approximately 2° (1.8°) per millimeter of rim recessed. CONCLUSION: The lateral CE angle should not be extrapolated to reflect anterior acetabular coverage. The anterior CE angle is a superior marker and predictably decreases with rim recession at double the rate of the lateral CE angle. CLINICAL RELEVANCE: The false-profile view is recommended in the perioperative workup for all patients undergoing arthroscopic treatment of pincer impingement.
Authors: Andrew J Riff; Alexander E Weber; Timothy C Keating; Benedict U Nwachukwu; Edward C Beck; Nozomu Inoue; Laura M Krivicich; Shane J Nho Journal: Arthrosc Sports Med Rehabil Date: 2019-08-06