Effect of Decreasing the Anterior Pelvic Tilt on Range of Motion in Femoroacetabular Impingement: A Computer-Simulation Study

Abstract

Background: The influence of pelvic tilt mobility, which can be reproduced in computer-simulation models, is an important subject to be addressed in the understanding of femoroacetabular impingement (FAI) pathophysiology. Purpose: To use computer-simulation models of FAI cases to evaluate the optimum improvement in hip range of motion (ROM) achieved by decreasing the anterior pelvic tilt and compare the results with the improvement in ROM achieved after cam resection surgery. Study Design: Controlled laboratory study. Methods: The pre- and postoperative computed tomography (CT) images from 28 patients with FAI treated with arthroscopic cam resection were evaluated. Using a dynamic computer-simulation program, 3-dimensional models with a 5° and a 10° decrease in anterior pelvic tilt from the supine functional pelvic plane (baseline) were created from the preoperative CT scans. Similar models were constructed for hips before (at baseline) and after cam resection. Improvements from baseline in maximum internal rotation at 45°, 70°, and 90° of flexion were assessed for the 5° change in pelvic tilt, 10° change in pelvic tilt, and cam resection models, and the results were compared for all conditions. Results: The combination of a 10° change in pelvic tilt and cam resection showed the largest ROM improvement from baseline ( P < .001). Improvement in internal rotation in the cam resection model was significantly higher compared with the 5° pelvic tilt change model ( P < .001), while there was no significant difference between the cam resection model and the 10° pelvic tilt change model. Conclusion: Decreasing anterior pelvic tilt by 10° in the preoperative computer simulation model resulted in an equivalent effect to cam resection, while a 5° change in pelvic tilt was inferior to cam resection in terms of ROM improvement. Clinical Relevance: Enough of a decrease in anterior pelvic tilt may contribute to ROM improvement that is as effective as that of cam resection surgery.

Shelf acetabuloplasty may inhibit range of motion: A computer simulation analysis

“…Computer simulation for kinematics is a powerful tool that has been applied to virtual osteochondroplasty in femoroacetabular impingement (FAI), 9 identification of the impingement point, 10 and assessments of the effect of pelvic mobility in FAI. 11,12 While there are several limitations, as listed below, computer simulation is effective, particularly when used to quantify ROM and bony impingement. To the best of our knowledge, no previous study has applied computer simulation analysis for evaluation after shelf acetabuloplasty.…”

Effect of 3-Dimensional Versus Single-Plane Changes in Pelvic Dynamics on Range of Motion in Hips With Femoroacetabular Impingement: A Computer Simulation Analysis

“…Given these results, we examined the effects of a 10° change in pelvic tilt. In a previous study, we conducted a dynamic simulation analysis to compare improvements in ROM (ie, MIR) between cam resection models and models of a 10° change in St. 16 Cam resection models were based on postoperative CT scans (cam resection surgery). We showed that a change in posterior St of 10° was as effective as cam resection at reducing impingement; however, a change of only 5° was not as effective as cam resection.…”

“…The clinical question arising here was “Should physical therapy that considers 3-dimensional (3D) complex mobility rather than just sagittal mobility be performed in patients with FAI?” The purpose of this study was to use simulation analysis to examine and compare the effect of 3D changes versus a single-plane change (ie, sagittal tilt [St]) in pelvic movement on hip ROM in patients with FAI. Because the effect of sagittal posterior tilt on improving hip ROM has been well demonstrated, 16,33,37 we focused on the comparison between complex 3D change and sagittal posterior tilt change. We hypothesized that the combination of 3D planar mobility (ie, St, axial rotation [Ar], and coronal tilt [Ct]) would lead to more effective resolution of biomechanical impingement, with small changes (5°) in 3D motion rather than a large change (10°) in a single direction (ie, sagittal).…”

“…9,12,13,40 For instance, trunk stabilization exercises improve clinical outcomes for FAI. 2 Similarly, changing pelvic position suitably may contribute to resolution of FAI 16,27 ; however, it is difficult to measure mobility, particularly in 3 dimensions.…”

“…33 In addition, a change in posterior sagittal pelvic tilt of 10° is as effective at improving range of motion (ROM) as cam resection, at least in a computer simulation setting. 16 However, in such cases, a large change in tilt in only a single plane (ie, the sagittal plane in the case of posterior tilt) may be limited and unnatural in terms of pelvic anatomic mobility. 41 It may be difficult to change the pelvic tilt by 10° through physical therapy alone.…”