BACKGROUND: Patients with chronic non-specific low back pain (CNSLBP) were found with impaired postural control in previous studies. Since the trunk muscle take important efforts on core stability, the study aimed to examine the relationships of postural control during stance tasks and the contractility of trunk muscle in young adults with CNSLBP and without.
METHODS: Healthy individuals (n = 25) and individuals with CNSLBP (n = 30) were included. The thickness of the bilateral transversus abdominis (TrA) and lumbar multifidus (MF) was measured during rest and maximal voluntary contraction, and the change percentages (TrA%, MF%) were calculated. Regarding postural control, COP path length and sway area during the stance tasks were measured thrice in each group.
RESULTS: The bilateral TrA% of the CNSLBP group was less than that of the HC group (p < 0.05). The bilateral TrA% of the CNSLBP group was less than that of the HC group (p < 0.05). The bilateral MF% showed no significantly different(p > 0.05) between the two groups. Compared with healthy controls, CNSLBP patients resulted larger path length and sway area of COP during most of static stance tasks. During the EO task in the CNSLBP group, TrA% was found correlate to COP path length (p < 0.05); the right MF% was correlated with COP sway area (p < 0.05). No significant correlations appeared in the healthy controls (p > 0.05).
CONCLUSIONS: Compared with healthy individuals, impaired postural control during static stance with eyes open in patients with CNSLBP was likely to be related to the poor contraction ability of bilateral transversus abdominis and correlated to the normal contraction ability of right lumbar multifidus.

The aim of this study was to investigate whether fat infiltration of the lumbar multifidus (LM) muscle affects revision surgery rates for adjacent-segment degeneration (ASD) after L4-5 transforaminal lumbar interbody fusion (TLIF) for degenerative spondylolisthesis.
A total of 178 patients undergoing single-level L4-5 TLIF for spondylolisthesis (2006 to 2016) were retrospectively analyzed. Inclusion criteria were a minimum 2-year follow-up, preoperative MR images and radiographs, and single-level L4-5 TLIF for degenerative spondylolisthesis. Twenty-three patients underwent revision surgery for ASD during the follow-up. Another 23 patients without ASD were matched with the patients with ASD. Demographic data, Roussouly curvature type, and spinopelvic parameter data were collected. The fat infiltration of the LM muscle (L3, L4, and L5) was evaluated on preoperative MRI using the Goutallier classification system.
A total of 46 patients were evaluated. There were no differences in age, sex, BMI, or spinopelvic parameters with regard to patients with and those without ASD (p > 0.05). Fat infiltration of the LM was significantly greater in the patients with ASD than in those without ASD (p = 0.029). Fat infiltration was most significant at L3 in patients with ASD than in patients without ASD (p = 0.017). At L4 and L5, there was an increasing trend of fat infiltration in the patients with ASD than in those without ASD, but the difference was not statistically significant (p = 0.354 for L4 and p = 0.077 for L5).
Fat infiltration of the LM may be associated with ASD after L4-5 TLIF for spondylolisthesis. Fat infiltration at L3 may also be associated with ASD at L3-4 after L4-5 TLIF.

The aim of the present study was to evaluate the relative functional volume of bilateral lumbar multifidus (LM) muscles across different stages and ages of patients with lumbar disc herniation (LDH). The relative functional volumes of LM muscles in both non-affected and affected sides in the L4-L5 and L5-S1 segmental level were measured in a resting prone position, and visual analogue score (VAS) for pain and Japanese Orthopedic Association (JOA) scores were recorded. The correlation between changes in the relative net volume of LM muscles and times of onset, ages, VAS and JOA scores were analyzed. A total of 327 cases were selected. The affected sides of LM muscles could present a certain degree of atrophy in stages >3 weeks. During the duration of the course, all cases presented different degrees of LM muscle atrophy. In addition, the degree of LM muscle atrophy was positively correlated with its duration. Age could influence the degree of LM muscle atrophy. Patients with unilateral LDH had <10% asymmetry on relative functional volume in the youth group. At the L4-L5 segments, patients with unilateral LDH had >10% asymmetry within the course of 3 months in the elderly group. The reduced rate of the relative functional net LM muscle volume was positively correlated with VAS scores, age, duration and JOA scores. In conclusion, the reduced rate of relative functional net LM muscle volume was positively correlated with age, duration, VAS scores and JOA scores. Although these findings are unreliable markers of lumbar pathology in an individual level for use in clinical or research settings, there is a notable importance of early intervention in LM muscle atrophy.