MRI‐­ and CT‐­based metrics for the quantification of arthroscopic bone resections in femoroacetabular impingement syndrome

Abstract

The purpose of this in vitro study was to quantify the bone resected from the proximal femur during hip arthroscopy using metrics generated from magnetic resonance imaging (MRI) and computed tomography (CT) reconstructed threedimensional (3D) bone models. Seven cadaveric hemipelvises underwent both a 1.5 T MRI and CT scan before and following an arthroscopic proximal femoral osteochondroplasty. The images from MRI and CT were segmented to generate 3D proximal femoral surface models. A validated 3D-3D registration method was used to compare surface-to-surface distances between the 3D models before and following surgery. The new metrics of maximum height, mean height, surface area and volume, were computed to quantify bone resected during osteochondroplasty.Stability of the metrics across imaging modalities was established through paired sample t-tests and bivariate correlation. Bivariate correlation analyses indicated strong correlations between all metrics (r = 0.728-0.878) computed from MRI and CT derived models. There were no differences in the MRI-and CT-based metrics used to quantify bone resected during femoral osteochondroplasty. Preoperative and postoperative MRI and CT derived 3D bone models can be used to quantify bone resected during femoral osteochondroplasty, without significant differences between the imaging modalities.

Three-Dimensional Quantification of Cam Resection Using MRI Bone Models: A Comparison of 2 Techniques

“…More recently, Guidetti et al 22 compared pre- and postoperative surface models and provided new metrics (ie, FH max , FH mean , FSA, FV) of quantifying bone resection during femoral osteochondroplasty. In the present study, the BFS method was used to quantify cam resection, with the ultimate goal of relating these metrics to those presented by Guidetti et al The BFS-AA and PP-SMS metrics indicated strong positive correlations, with r values ranging from 0.679 to 0.888.…”

“…Pre- and postoperative MRI scans were performed on all specimens on a 1.5-T Magnetom Espree system (Siemens) using a sequence previously described. 22 , 37 All MRI scans were exported as DICOM (Digital Imaging and Communication in Medicine) files and stored in an institutional picture archiving and communication system. All pre- and postoperative MRI scans were segmented using a semiautomatic segmentation process with commercially available software (Mimics version 21; Materialise).…”

“…The postoperative 3D bone model was subtracted from the preoperative model to quantify the bone resected during hip arthroscopy as previously described. 22 The postoperative 3D bone model was subtracted from the preoperative model to quantify the bone resected during hip arthroscopy, with a threshold of greater than 0.5 mm ( Figure 3 ) required to define the cam resection. The cam resection was quantified using the following metrics: maximum height (FH max ; mm), mean height (FH mean ; mm), surface area (FSA; mm 2 ), and volume (FV; mm 3 ).…”

“…Malloy et al 37 validated the use of magnetic resonance imaging (MRI) for evaluating the anatomy of the proximal femur in patients with cam-type FAIS, reporting that 1.5-T MRI produced femoral surface models that more accurately represented the actual bone surface than did CT with respect to the laser-scanned ground-truth models. More recently, Guidetti et al 22 incorporated postoperative imaging to quantify the amount of bone resected after osteochondroplasty via a 3D preoperative-postoperative surface model subtraction (PP-SMS) technique.…”

Outcomes for the Arthroscopic Treatment of Femoroacetabular Impingement Syndrome With Acetabular Retroversion: A 3D Computed Tomography Analysis

“…However, previous studies have demonstrated that 1.5-T MRI can be used to produce 3D bone models and are equivalent to models derived from CT, supporting the potential to perform a similar study with MRI-based bone models. 20,38 Moreover, while alignment of the pelvis to a standard coordinate plane may provide a standardized method to assess acetabular version, it may fail to represent the patient's true pelvic orientation during activities of daily living. For example, patients who function with posterior pelvic tilt at baseline will have reduced AA when aligned to a standard coordinate plane.…”