Cam osteochondroplasty for femoroacetabular impingement increases microinstability in deep flexion: A cadaveric study

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Title: Cam osteochondroplasty for femoroacetabular impingement increases microinstability in deep flexion: A cadaveric study
Authors: Ng, KCG
Bankes, M
El Daou, H
Rodriguez y Baena, F
Jeffers, J
Item Type: Journal Article
Abstract: Purpose: The purpose of this in vitro cadaveric study was to examine the contributions of each surgical stage during cam femoroacetabular impingement (FAI) surgery (i.e., intact cam hip, T8 capsulotomy, cam resection, capsular repair) towards hip range of motion, translations, and microinstability. Methods: Twelve cadaveric cam hips were denuded to the capsule and mounted onto a robotic tester. Hips were positioned in several flexion positions: Full Extension, Neutral 0°, Flexion 30°, and Flexion 90°; and performed internal-external rotations to 5-Nm torque in each position. Hips underwent a series of surgical stages (T-capsulotomy, cam resection, capsular repair) and was retested after each stage. Changes in range of motion, translation, and microinstability (overall translation normalized by femoral head radius) were measured after each stage. Results: For range of motion, cam resection increased internal rotation at Flexion 90° (ΔIR = +6°, P = .001), but did not affect external rotation. Capsular repairs restrained external rotations compared to the cam resection stage (ΔER = –4 to –8°, P ≤ .04). For translations, the hip translated after cam resection at Flexion 90° in the medial-lateral plane (ΔT = +1.9 mm, P = .04), relative to the intact and capsulotomy stages. For microinstability, capsulotomy increased microinstability in Flexion 30° (ΔM = +0.05; P = .003), but did not further increase after cam resection. At Flexion 90°, microinstability did not increase after capsulotomy (ΔM = +0.03; P = .2, d = .24), but substantially increased after cam resection (ΔM = +0.08; P = .03), accounting for a 31% change with respect to the intact stage. Conclusions: Cam resection increased microinstability by 31% during deep hip flexion relative to the intact hip. This suggests that iatrogenic microinstability may be due to separation of the labral seal and resected contour of the femoral head. Clinical Relevance: Our in vitro study demonstrated that, at time-zero and prior to postoperative recovery, excessive motion after cam resection could disrupt the labral seal. Complete cam resection should be performed cautiously to avoid disruption of the labral seal and postoperative microinstability.
Issue Date: Jan-2021
Date of Acceptance: 29-Aug-2020
URI: http://hdl.handle.net/10044/1/82045
DOI: 10.1016/j.arthro.2020.08.037
ISSN: 0749-8063
Publisher: International Society of Arthroscopy, Knee Surgery, and Orthopaedic Sports Medicine
Start Page: 159
End Page: 170
Journal / Book Title: Arthroscopy: The Journal of Arthroscopy and Related Surgery
Volume: 37
Issue: 1
Copyright Statement: © 2020 Elsevier Ltd. All rights reserved. This manuscript is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International Licence http://creativecommons.org/licenses/by-nc-nd/4.0/
Sponsor/Funder: Engineering & Physical Science Research Council (EPSRC)
Engineering & Physical Science Research Council (E
National Institute for Health Research
Funder's Grant Number: EP/K027549/1
EP/N006267/1
NIHR300013
Keywords: Orthopedics
1103 Clinical Sciences
Publication Status: Published
Online Publication Date: 2020-09-11
Appears in Collections:Mechanical Engineering
Department of Surgery and Cancer
Faculty of Medicine
Faculty of Engineering



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