Table 3: Fatty infiltration of paraspinal muscles and association with LBP.

ResearchModalityParticipantsSegments measuredLevel of measurementMethodFatty infiltrationAssociation with LBP

Fortin et al. [24]MRI33 patients diagnosed with posterolateral disc herniation at L4-L5The center of each intervertebral disc, the center of S1 vertebral body, perpendicular to the muscle massThe ratio of lean mass CSA to total CSA as an indicator of muscle composition (or fatty infiltration) Multifidus affected sideMultifidus nonaffected sideGreater fat infiltration on the side and at spinal levels adjacent to the disc herniation. Muscle asymmetry was not correlated with symptom duration
L3-L40.58 ± 0.210.61 ± 0.17
L4-L50.55 ± 0.160.57 ± 0.14
L5-S10.51 ± 0.110.53 ± 0.11
S10.46 ± 0.120.49 ± 0.13
Erector spine affected sideErector spine nonaffected side
L3-L40.58 ± 0.170.61 ± 0.14
L4-L50.47 ± 0.170.52 ± 0.12
L5-S10.30 ± 0.150.36 ± 0.15
S10.29 ± 0.260.32 ± 0.17
Signal intensity as an indicator for fatty infiltrationMultifidus affected sideMultifidus nonaffected side
L3-L41959.1 ± 1606.31972.6 ± 1610.7
L4-L52015.3 ± 1811.42243.2 ± 1766.0
L5-S12625.3 ± 2109.22476.3 ± 1932.
S13159.4 ± 2001.553029.2 ± 1837.5
Erector spine affected sideErector spine nonaffected
L3-L41988.0 ± 1593.11882.0 ± 1468.3
L4-L52520.6 ± 2092.62338.7 ± 1821.1
L5-S12876.9 ± 2320.62804.5 ± 2200.1
S13688.4 ± 2137.23323.7 ± 1795.4

Hebert et al. [34]MRI401 participants. 40-year-old adults randomly sampled from a Danish population and followed up at 45 and 49 years of ageL4
L5
Using signal intensity to separate muscle from fat. Presented as % of the fat CSA from the total muscle CSAOut of the four results (level L4, L5: left and right side), only the highest percentage of fat is presented
Age 40: 28.8 ± 12.7%
Age 45: 28.7 ± 11.9%
Age 49: 31.6 ± 13.0%
The relationship between multifidus fat infiltration and LBP/leg pain is inconsistent and may be modified by age

D’hooge et al. [25]MRI13 individuals with recurrent nonspecific LBP, and 13 asymptomatic individualsL3
L4
L4
Superior endplate
Superior endplate
Inferior end plate
Axial images
Muscle-fat-indexMultifidus:
LBP: 18.4 ± 6.4
Control: 14.0 ± 2.6
Erector spine:
LBP: 23.9 ± 6.1
Control: 20.7 ± 2.5
The increase in fatty infiltration in lean lumbar muscle tissue, in the absence of alterations in muscle size or macroscopic fat deposition after resolution of LBP. It is hypothesized that decreased muscle quality may contribute to the recurrence of LBP

Niemeläinen et al. [35]MRI126 asymptomatic menL3-L4
L4-L5
L5-S1
Not described in the manuscriptThe ratio of functional CSA to total CSA as an indicator of muscle composition (or fatty infiltration)Multifidus:
L3-L4; Rt: 82, Lt: 83
L4-L5; Rt: 76, Lt: 77
L5-S1; Rt: 72, Lt: 73
Erector spine:
L3-L4; Rt: 84, Lt: 85
L4-L5; Rt: 77, Lt: 79
L5-S1; Rt: 73, Lt: 76
The amount of intramuscular fat significantly increased caudally for both muscles.
Paraspinal muscle asymmetry, >10%, was commonly found in men without a history of LBP

Mengiardi et al. [13]MR spectroscopy25 patients with chronic LBP and in 25 matched asymptomatic volunteersL4-5 levelMean percentage fat content of the muscleMultifidus:
Chronic LBP: 23.6%
Control: 14.5%
Erector spine:
Chronic LBP: 29.3%
Control: 26.0%
Significantly higher fat content in the multifidus muscle in patients with chronic LBP than in asymptomatic volunteers

Chan et al. [27]US, in prone position12 asymptomatic men; 12 men with LBPL4
L4
Vertebral laminaFat CSA (cm2)Multifidus controls:
Lt; 0.56 ± 0.10;
Rt; 0.61 ± 0.09
Multifidus LBP:
Lt; 1.08 ± 0.23;
Rt; 1.13 ± 0.23
Fat area within the multifidus was larger in chronic LBP patients

LBP: low back pain, CSA: cross-sectional area, Rt: right side, and Lt: left side.