Inter- and Intraobserver reproducibility of T2 relaxation times of the discus interpubicus: A feasibility study at 3 Tesla

Kai-Jonathan Maas,Marc Regier,Maxim Avanesov,Azien Laqmani,Julius Weinrich,Cyrus Behzadi,Gerhard Adam,Michael G Kaul,Markus Sauer,Jan Fritz

doi:10.1371/journal.pone.0202698

Kai-Jonathan Maas, Marc Regier + Show 8 more

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https://doi.org/10.1371/journal.pone.0202698

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Abstract

ObjectiveTo quantify standard values of the discus interpubicus in healthy subjects and to determine reliability and repeatability using T2 relaxation time measurements at 3T.Methods20 asymptomatic participants (10 male, 10 female; mean age: 27.3 years ±4.1, BMI: 22.2 ±1.8) underwent a 3T Magnetic Resonance Imaging (MRI) of the pelvic region in a supine position. We included sagittal and para-axial T2w sequences centred over the pubic symphysis in order to identify the complete discus interpubicus. For quantitative analysis, a multi-echo Turbo Spin Echo (TSE) sequence (including 12 echo times between 6.4 and 76.8 ms) was acquired and analysed by using an in-house developed quantification plugin tool (qMapIt) extending ImageJ. Two readers in consensus defined three central slices of the pubic symphysis with the greatest length. For each slice, both readers separately placed three regions-of-interest (ROI) covering the whole discus interpubicus. Both readers repeated the ROI placements in identical fashion after a four-week interval on the original MRI images. Statistical analysis included intraclass correlation coefficient (ICC), nonparametric Wilcoxon test, Fisher exact test and mean relaxation time in ms and 95% confidence intervals.ResultsT2 relaxation time analysis was performed for all 20 participants. In total, a mean relaxation time of all analysed segments for both observers was 48.6 (±6.3 ms), with a mean relaxation time for observer 1 of 48.7 (±6.0 ms) and for observer 2 of 48.5 ms (±6.6ms). The calculated ICC comparing inter- and intrarater reproducibility was excellent in all segments (≥0.75).ConclusionT2 mapping of the discus interpubicus demonstrates good inter- and intrarater repeatability as well as reliability. Mean relaxation times were calculated with 48.6ms in healthy volunteers.

Highlights

Osteitis pubis (OP) is considered as one of the major reasons for groin pain in athletes overall [1]
The discus interpubicus is centrally located in the pubic symphysis between the joint surfaces of the pubic bones (Facies symphysialis) while representing an important stabilizer for biomechanical shear forces
It consists of a thick, fibrocartilaginous disc which blends into the surrounding ligamentous structures and a thin cartilage layer of the articular surfaces of the pubic bones [5]

Summary

Introduction

Osteitis pubis (OP) is considered as one of the major reasons for groin pain in athletes overall [1]. The discus interpubicus is centrally located in the pubic symphysis between the joint surfaces of the pubic bones (Facies symphysialis) while representing an important stabilizer for biomechanical shear forces It consists of a thick, fibrocartilaginous disc which blends into the surrounding ligamentous structures and a thin cartilage layer of the articular surfaces of the pubic bones [5]. At the caudal aspect of the discus interpubicus is the inferior (= arcuate) pubic ligament situated in the angulus subpubicus The former mentioned thick arcuate ligament is considered as the most important mechanical stabilizer of the pubic symphysis[6]. The discus is surrounded by various muscle insertions originating from the upper and lower body as e.g. the musculus rectus abdominis and the adductor muscles This anatomic constellation demonstrates the enormous mechanical forces centred on the pubic symphysis. The authors even successfully demonstrated the feasibility of T2 relaxation time measurements of the sacroiliac joint in a preliminary study design demonstrating moderate inter- and intraobserver reliability[17]

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