General Session: Diagnostic Imaging
Presented by: V. Lafage
N. Bronsard(1), C. Amabile(2), A. Ianessi(1), B. Moal(2), W. Skalli(2), H. Bao(3), F. Schwab(4), F. de Peretti(1), V. Lafage(4)
(1) Centre Hospitalier Universitaire de Nice, Nice, France
(2) Laboratoire de Biomécanique, Arts et Métiers ParisTech, Paris, France
(3) Nanjing Drum Tower Hospital, Nanjing, China
(4) Hospital for Special Surgery, New York, NY, United States
Background: Spinal alignment involves both bony and muscular factors. Current realignment strategies focus on the bony architecture. The lack of attention to muscular factors is partially from the lack of normative data on muscle quality, particularly with respect to gender.
Purpose: To establish normal reference values of muscle volume (MV) and fat infiltration (FI) and to investigate gender-based differences. Study desgin/setting: Prospective consecutive enrollment of asymptomatic volunteers
Patient Sample: 30 Subjects
Outcome Measures: 3D muscle reconstructions, cross-sectional muscle areas and fat infiltration.
Methods: Asymptomatic volunteers between 18 and 25 years old underwent an axial MRI from T12 to the knee using the 2-point Dixon method (fat/water separation technique). A total of 20 muscles were manually outlined on each MRI and the following parameters were extracted: 3D muscle reconstructions, cross-sectional muscle areas, and fat infiltration. Individual muscles were anatomically grouped (Anterior/Posterior) to the spine, hip, and knee. Muscle Volumes and Fat Infiltration data across these groups were compared between males and females.
Results: 15 Male and 15 Female asymptomatic volunteer were enrolled. There was no significant difference between male and female subjects in terms of age (mean=19.6 ± 1.35 years old) or BMI (mean=21.02±1.91 kg/m2). Male subjects had 50% larger Muscle Volumes than female subjects (14,749cm3 vs 9,803cm3, p< 0.01), without significant differences in Fat Infiltration (M=19.1%, F=23.3%%, p=0.1). As a percentage of the total Muscle Volume, the posterior hip muscles represented 45%, followed by the anterior hip muscles (37%), the posterior spine muscles (10%), and the posterior knee muscles (10%). Gender did not affect these proportional distributions in muscle volume. The comparison between Anterior and Posterior groups revealed significantly smaller Fat Infiltrations within the posterior groups (Hip -13% p< 0.01, Knee -14% p< 0.01, p< 0.01), except for at the spine (+15%, p< 0.01). Gender did not affect these anterior vs. posterior Muscle Volume and Fat Infiltration patterns except for spinal muscles, where females had greater Fat Infiltration both anteriorly (26% vs 19%, p< 0.01) and posteriorly (34% vs 20%, p< 0.01). Muscle by muscle, the erector spinae (28%) and the rectus abdominus (30%) had the highest Fat Infiltrations. Females had higher Fat Infiltrations in seven muscles, six of which were at the spinal level.
Conclusions: This is the first study to volumetrically compare and quantify gender-based normative muscle quality in young adults. The mean Fat Infiltration of 20% in young asymptomatic subjects emphasizes the need to pre-operatively evaluate muscle quality in adult spinal deformity patients.