Volume and fat infiltration of spino-pelvic musculature in adults with spinal deformity

Table 1 Muscles analyzed in this study, and grouping by function and joint

	Spine extensor	Spine flexor	Hip extensor	Hip flexor	Knee extensor	Knee flexor	Total muscle
Quadratus lumborum	x						x
Tractus medialis	x						x
Tractus lateralis	x						x
Psoas		x		x			x
Iliacus		x		x			x
Biceps femoris short			x			x	x
Biceps femoris long			x			x	x
Semi-membranosus			x			x	x
Semi-tendinosus			x			x	x
Gluteus maximus			x				x
Rectus femoris				x	x		x
Gracilis				x		x	x
Sartorius				x		x	x
Adductor				x			x
Tensor fascia lata				x			x
Vastus lateralis intermedius					x		x
Vastus medialis					x		x

Table 2 Demographic information

	Min	Max	Mean	SD	95%CI
					Lower	Upper
Age	37	80	60	13	54	66
BMI	17.4	31.2	22.9	3.52	21.1	24.6

BMI: Body mass index.

Table 3 Mean and standard deviation of Dixon fat-water ratio for the phantom with the different concentrations of fat

Vails	Real fat concentration (%)	Dixon fat-water ratio (%)
Only soybean oil	100	85.4 ± 0.3
Intralipid 20% fat emulsion	20	38.7 ± 1.7
Intralipid 10% fat emulsion	10	22.2 ± 1.0
Only water	0	1.4 ± 0.6

Table 4 Muscular Volumes of each muscle group

	Muscular volume
	Min	Max	Mean	SD	95%CI
					Lower	Upper
Spine extensor	0.92	1.89	1.46	0.27	1.33	1.59
Spine flexor	0.85	1.67	1.24	0.22	1.13	1.34
Hip extensor	3.42	6.00	4.83	0.63	4.52	5.13
Hip flexor	4.79	7.13	5.91	0.71	5.57	6.25
Knee extensor	3.70	6.95	5.15	0.86	4.73	5.57
Knee flexor	2.18	3.41	2.88	0.33	2.72	3.04
Total muscles	12.87	19.44	16.67	1.87	15.77	17.57

Reported values are normalized based upon the volume of the right femur of each patient (for example, the mean “Total Muscles” volume = 16.67 femurs volume).

Table 5 Percentage of infiltrated fat expressed by functional groups

	Percentage of fat component
	Min	Max	Mean	SD	95%CI
					Lower	Upper
Spine extensor	12.72	71.15	31.90	13.83	25.24	38.57
Spine flexor	5.67	20.39	11.92	3.63	10.17	13.66
Hip extensor	6.39	38.09	14.81	7.01	11.43	18.19
Hip flexor	6.10	20.22	10.76	3.16	9.24	12.29
Knee extensor	3.84	20.02	8.66	4.03	6.72	10.60
Knee flexor	6.93	25.44	12.81	4.20	10.78	14.83
Total muscles	6.12	28.84	13.34	5.33	10.77	15.91

Table 6 Ratio between flexors and extensors for each group of muscles (muscular volume and infiltrated fat volume)

	Ratio flex/ext: Vmusle						Ratio flex/ext: Vfat
	Min	Max	Mean	SD	95%CI		Min	Max	Mean	SD	95%CI
					Lower	Upper					Lower	Upper
Spine	0.61	1.21	0.87	0.17	0.79	0.95	0.10	0.68	0.36	0.14	0.29	0.42
Hip	1.02	1.43	1.23	0.13	1.17	1.29	0.54	1.31	0.95	0.19	0.86	1.04
Knee	0.42	0.72	0.57	0.08	0.53	0.61	0.66	1.10	0.87	0.12	0.81	0.93

Vmuscle: Muscular volume; Vfat: Infiltrated fat volume.

Table 7 Correlation between age and muscular volume, infiltrated fat volume and percentage of fat component

		Vmuscle		Vfat		Pfat
		r	P	r	P	r	P
Age	Spine extensor	-0.208	0.393	0.420	0.073	0.480a	0.038
	Spine flexor	-0.417	0.076	0.208	0.393	0.427	0.068
	Hip extensor	0.018	0.943	0.564a	0.012	0.633b	0.004
	Hip flexor	-0.309	0.198	0.555a	0.014	0.658b	0.002
	Knee extensor	-0.701b	0.001	0.645b	0.003	0.680b	0.001
	Knee flexor	-0.319	0.183	0.589b	0.008	0.679b	0.001
	All muscles	-0.433	0.064	0.614b	0.005	0.676b	0.001

Statistically significant difference with

^aP-value < 0.05; Statistically significant difference with

^bP-value < 0.01. Vmuscle: Muscular volume; Vfat: Infiltrated fat volume; Pfat: Percentage of fat component.

Table 8 Correlation between age and muscular volume, infiltrated fat volume and percentage of fat component

		Vmuscle		Vfat		Pfat
		r	P	r	P	r	P
BMI	Spine extensor	0.127	0.606	0.017	0.944	-0.038	0.876
	Spine flexor	-0.027	0.913	0.443	0.057	0.450	0.053
	Hip extensor	0.642b	0.003	0.693b	0.001	0.587b	0.008
	Kip flexor	0.159	0.515	0.657b	0.002	0.587b	0.008
	Knee extensor	-0.236	0.330	0.596b	0.007	0.518a	0.023
	Knee flexor	0.470a	0.042	0.761b	< 0.001	0.570a	0.011
	All muscles	0.207	0.394	0.592b	0.008	0.458a	0.049

Statistically significant difference with

^aP-value < 0.05; Statistically significant difference with

^bP-value < 0.01. Vmuscle: Muscular volume; Vfat: Fat volume; Pfat: Percentage of fat component.