Prospective Study
Copyright ©The Author(s) 2015. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Orthop. Oct 18, 2015; 6(9): 727-737
Published online Oct 18, 2015. doi: 10.5312/wjo.v6.i9.727
Volume and fat infiltration of spino-pelvic musculature in adults with spinal deformity
Bertrand Moal, Nicolas Bronsard, José G Raya, Jean Marc Vital, Frank Schwab, Wafa Skalli, Virginie Lafage
Bertrand Moal, Frank Schwab, Virginie Lafage, Spine Division, Hospital for Joint Diseases, New-York University University Langone Medical Center, New York, NY 10003, United States
Nicolas Bronsard, Nice University Hospital Center, Orthopedic and Traumatologic Surgery Department, Hôpital Saint Roch, 06000 Nice, France
José G Raya, Center for Biomedical Imaging, Department of Radiology, New York University Langone Medical Center, New York, NY 10016, United States
Jean Marc Vital, University Hospital of Bordeaux, Spinal Unit, Departement of Orthopaedic Surgery, 33000 Bordeaux, France
Wafa Skalli, Laboratory of Biomechanics, Arts et Métiers ParisTech, 75013 Paris, France
Author contributions: All authors contributed equally to this work.
Supported by International Spine Study Group and ParisTech BiomecAM chair program on subject-specific musculoskeletal modeling, with the support of Proteor, Covea, Société Général, ParisTech and Yves Cotrel Foundation.
Institutional review board statement: Institutional review board approval.
Clinical trial registration statement: This study is registered at New York University of Medicine’s Institutional Review Board. The registration identification number is 11-01647.
Informed consent statement: All study participants, or their legal guardian, provided informed written consent prior to study enrollment.
Conflict-of-interest statement: Bertrand Moal, Nicolas Bronsard, José G. Raya and Jean Marc Vital have no conflicts of interest to declare; Frank J. Schwab is a consultant and received grants for research purpose by Medtronic and Depuy. He is a shareholder of Nemaris. Wafa Skalli has royalties from EOS imaging (Royalties) and received a grant for research purpose by the Fondation ParisTech chair program on subject specific musculoskeletal modelling. Virginie Lafage received a grant for research purpose by SRS and ISSG. She is giving lectures for Globus, Depuy Spine, Medtronic, Nuvasive and MDT. She is a shareholder of Nemaris.
Data sharing statement: Technical appendix, statistical code, and dataset available from the corresponding author at Virginie.lafage@gmail.com. Consent from participants was not obtained but the presented data are anonymized and risk of identification is low.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Virginie Lafage, PhD, Spine Division, Hospital for Joint Diseases, New-York University University Langone Medical Center, 306 E. 15th St., New York, NY 10003, United States. virginie.lafage@gmail.com
Telephone: +1-646-7948646 Fax: +1-646-6026926
Received: March 13, 2015
Peer-review started: March 16, 2015
First decision: June 4, 2015
Revised: July 23, 2015
Accepted: August 13, 2015
Article in press: August 14, 2015
Published online: October 18, 2015
Processing time: 221 Days and 7.4 Hours
Abstract

AIM: To investigate fat infiltration and volume of spino-pelvic muscles in adults spinal deformity (ASD) with magnetic resonance imaging (MRI) and 3D reconstructions.

METHODS: Nineteen female ASD patients (mean age 60 ± 13) were included prospectively and consecutively and had T1-weighted Turbo Spin Echo sequence MRIs with Dixon method from the proximal tibia up to T12 vertebra. The Dixon method permitted to evaluate the proportion of fat inside each muscle (fat-water ratio). In order to investigate the accuracy of the Dixon method for estimating fat vs water, the same MRI acquisition was performed on phantoms of four vials composed of different proportion of fat vs water. With Muscl’X software, 3D reconstructions of 17 muscles or group of muscles were obtained identifying the muscle’s contour on a limited number of axial images [Deformation of parametric specific objects (DPSO) Method]. Musclar volume (Vmuscle), infiltrated fat volume (Vfat) and percentage of fat infiltration [Pfat, calculated as follow: Pfat = 100 × (Vfat/Vmuscle)] were characterized by extensor or flexor function respectively for the spine, hip and knee and theirs relationship with demographic data were investigated.

RESULTS: Phantom acquisition demonstrated a non linear relation between Dixon fat-water ratio and the real fat-water ratio. In order to correct the Dixon fat-water ratio, the non linear relation was approximated with a polynomial function of degree three using the phantom acquisition. On average, Pfat was 13.3% ± 5.3%. Muscles from the spinal extensor group had a Pfat significantly greater than the other muscles groups, and the largest variability (Pfat = 31.9% ± 13.8%, P < 0.001). Muscles from the hip extensor group ranked 2nd in terms of Pfat (14% ± 8%), and were significantly greater than those of the knee extensor (P = 0.030). Muscles from the knee extensor group demonstrated the least Pfat (12% ± 8%). They were also the only group with a significant correlation between Vmuscle and Pfat (r = -0.741, P < 0.001), however this correlation was lacking in the other groups. No correlation was found between the Vmuscle total and age or body mass index. Except for the spine flexors, Pfat was correlated with age. Vmuscle and Vfat distributions demonstrated that muscular degeneration impacted the spinal extensors most.

CONCLUSION: Mechanisms of fat infiltration are not similar among the muscle groups. Degeneration impacted the spinal and hip extensors most, key muscles of the sagittal alignment.

Keywords: Spino-pelvic musculature; Adults with spinal deformity; Muscular degeneration; Muscular volume; Fat infiltration; Dixon method

Core tip: Volume and fat infiltration of spine, hip, and knee extensor and flexor muscles of 19 patients with spinal deformity were evaluated with an innovative method combining dedicated magnetic resonance imaging acquisition (Dixon method) and 3D reconstructions. The results demonstrated that mechanisms of fat infiltration are not similar among the muscle groups. Degeneration impacted the spinal and hip extensors most, key muscles of the sagittal alignment, highlighting the need for considering muscular factors beyond skeletal parameters.