Multifidus atrophy is localized and bilateral in active persons with chronic unilateral low back pain

Report of the NIH task force on research standards for chronic low back pain

Despite rapidly increasing intervention, functional disability due to chronic low back pain (cLBP) has increased in recent decades. We often cannot identify mechanisms to explain the major negative impact cLBP has on patients' lives. Such cLBP is often termed nonspecific and may be due to multiple biologic and behavioral etiologies. Researchers use varied inclusion criteria, definitions, baseline assessments, and outcome measures, which impede comparisons and consensus. Therefore, NIH Pain Consortium charged a research task force to draft standards for research on cLBP. The resulting multidisciplinary panel recommended using 2 questions to define cLBP; classifying cLBP by its impact (defined by pain intensity, pain interference, and physical function); use of a minimum data set to describe research participants (drawing heavily on the Patient Reported Outcomes Measurement Information System methodology); reporting "responder analyses" in addition to mean outcome scores; and suggestions for future research and dissemination. The Pain Consortium has approved the recommendations, which investigators should incorporate into NIH grant proposals. The research task force believes that these recommendations will advance the field, help resolve controversies, and facilitate future research addressing the genomic, neurological, and other mechanistic substrates of cLBP. We expect that the research task force recommendations will become a dynamic document and undergo continual improvement.

PERSPECTIVE

A task force was convened by the NIH Pain Consortium with the goal of developing research standards for cLBP. The results included recommendations for definitions, a minimum data set, reporting outcomes, and future research. Greater consistency in reporting should facilitate comparisons among studies and the development of phenotypes.

Report of the NIH Task Force on research standards for chronic low back pain

Despite rapidly increasing intervention, functional disability due to chronic low back pain (cLBP) has increased in recent decades. We often cannot identify mechanisms to explain the major negative impact cLBP has on patients' lives. Such cLBP is often termed non-specific and may be due to multiple biologic and behavioral etiologies. Researchers use varied inclusion criteria, definitions, baseline assessments, and outcome measures, which impede comparisons and consensus. Therefore, NIH Pain Consortium charged a Research Task Force (RTF) to draft standards for research on cLBP. The resulting multidisciplinary panel recommended using 2 questions to define cLBP; classifying cLBP by its impact (defined by pain intensity, pain interference, and physical function); use of a minimum dataset to describe research participants (drawing heavily on the PROMIS methodology); reporting "responder analyses" in addition to mean outcome scores; and suggestions for future research and dissemination. The Pain Consortium has approved the recommendations, which investigators should incorporate into NIH grant proposals. The RTF believes that these recommendations will advance the field, help to resolve controversies, and facilitate future research addressing the genomic, neurologic, and other mechanistic substrates of chronic low back pain. We expect that the RTF recommendations will become a dynamic document and undergo continual improvement.

PERSPECTIVE

A task force was convened by the NIH Pain Consortium with the goal of developing research standards for chronic low back pain. The results included recommendations for definitions, a minimum dataset, reporting outcomes, and future research. Greater consistency in reporting should facilitate comparisons among studies and the development of phenotypes.

Reliability of the Goutallier classification in quantifying muscle fatty degeneration in the lumbar multifidus using magnetic resonance imaging

OBJECTIVE

The purpose of this study was to investigate the reliability of the Goutallier classification system (GCS) for grading muscle fatty degeneration in the lumbar multifidus (LM) using magnetic resonance imaging (MRI) examinations.

METHODS

Lumbar spine MRI scans were obtained retrospectively from the radiology department imaging system. Two examiners (a chiropractic diagnostic imaging resident and a board certified chiropractic radiologist with 30 years of experience) independently graded each LM at the L4/5 and L5/S1 intervertebral level. ImageJ pixel analysis software (version 1.47; National Institutes of Health, Bethesda, MD) was used independently by 2 observers to quantify the percent fat of the LM and allow correlation between LM percent fat and GCS grade. Twenty-five subject MRIs were randomly selected. Magnetic resonance imaging scans were included if they were obtained using a 1.5 T imaging system and were excluded if there was evidence of spinal infection, tumor, fracture, or postoperative changes. For all tests, P < .05 was defined as significant.

RESULTS

Intraobserver reliability grading LM fat ranged from a weighted κ (κw) of 0.71 to 0.93. Mean interobserver reliability grading LM fat was κ(w), 0.76 to κ(w), 0.85. There was a significant (P < .001) correlation between LM percent fat and GCS grade. Furthermore, interobserver reliability in determining percent fat was between intraclass correlation coefficient, 0.73 to intraclass correlation coefficient, 0.90.

CONCLUSIONS

In this study, the GCS was reliable in grading LM fatty degeneration and correlated positively with a quantified percent fat value. In addition, ImageJ software (National Institutes of Health) was reliable between raters when quantifying LM percent fat.

Size and symmetry of trunk muscles in ballet dancers with and without low back pain

STUDY DESIGN

Cross-sectional, observational study.

OBJECTIVES

To investigate the cross-sectional area (CSA) of trunk muscles in professional ballet dancers with and without low back pain (LBP).

BACKGROUND

LBP is the most prevalent chronic injury in classical ballet dancers. Research on nondancers has found changes in trunk muscle size and symmetry to be associated with LBP. There are no studies that examine these changes in ballet dancers.

METHODS

Magnetic resonance imaging was performed in 14 male and 17 female dancers. The CSAs of 4 muscles (multifidus, lumbar erector spinae, psoas, and quadratus lumborum) were measured and compared among 3 groups of dancers: those without LBP or hip pain (n = 8), those with LBP only (n = 13), and those with both hip-region pain and LBP (n = 10).

RESULTS

Dancers with no pain had larger multifidus muscles compared to those with LBP at L3-5 (P<.024) and those with both hip-region pain and LBP at L3 and L4 on the right side (P<.027). Multifidus CSA was larger on the left side at L4 and L5 in dancers with hip-region pain and LBP compared to those with LBP only (P<.033). Changes in CSA were not related to the side of pain (all, P>.05). The CSAs of the other muscles did not differ between groups. The psoas (P<.0001) and quadratus lumborum (P<.01) muscles were larger in male dancers compared to female dancers. There was a positive correlation between the size of the psoas muscles and the number of years of professional dancing (P = .03).

CONCLUSION

In classical ballet dancers, LBP and hip-region pain and LBP are associated with a smaller CSA of the multifidus but not the erector spinae, psoas, or quadratus lumborum muscles.

Multifidus and paraspinal muscle group cross-sectional areas of patients with low back pain and control patients: a systematic review with a focus on blinding

BACKGROUND

Several studies have investigated differences in paraspinal muscle morphology between patients with low back pain (LBP) and control patients. However, inconsistencies in the results of some of these studies may limit generalizations.

OBJECTIVE

The purpose of this study was to systematically review studies evaluating paraspinal muscle morphology in patients with LBP and control patients, with a focus on the effects of blinding.

DATA SOURCES

An electronic search was performed with the use of relevant databases. Study quality was evaluated by means of the Newcastle-Ottawa Quality Assessment Scale.

STUDY SELECTION

Case-control studies investigating paraspinal muscle size between patients with LBP and control patients who were healthy were included. Studies that compared paraspinal muscle size between symptomatic and asymptomatic sides of patients with unilateral LBP also were included.

DATA EXTRACTION

Studies investigating the same outcome-at the same spinal level and for the same muscle and population-were pooled. Mean differences with 95% confidence interval were calculated for each study.

DATA SYNTHESIS

Eleven studies were included. With 1 exception, all pooled results were significantly different statistically between groups, suggesting that paraspinal muscles are smaller in patients with chronic LBP than in control patients and on the symptomatic side of patients with chronic unilateral LBP. In patients with acute unilateral LBP, there was no significant difference between sides. A qualitative examination demonstrated a trend toward an increased effect size when outcome assessors were unblinded.

LIMITATIONS

Limitations of this review include the small number of studies included and their small sample size. Misclassification of blinding status may have occurred when the study did not report blinding status.

CONCLUSIONS

Evidence suggests that paraspinal muscles are significantly smaller in patients with chronic LBP than in control patients. Although no definite conclusion could be taken as to the effects of blinding, future imaging studies should consider the use of blinded outcome assessors.

Spectral analysis of EMG using intramuscular electrodes reveals non-linear fatigability characteristics in persons with chronic low back pain

Greater fatigability across lumbar extensors has been reported in persons with chronic low back pain (LBP), however, extensor atrophy tends to be local to the site of pain. Therefore, specific ultrasound guided local and remote intramuscular electromyographic recordings were undertaken during an isometric horizontal trunk hold in two carefully matched cohorts; persons with and without LBP. The test was performed to self-determined maximal hold time, and the control group held the horizontal position longer (P < 0.001). A power spectral analysis was performed to calculate the normalized median frequency (NMF) slope for both the first and last 30s of the fatigue test due to the group difference in hold times. There were no significant group differences in NMF slope at the first 30s of testing (P = 0.650). The NMF slope for the first and last 30s was not different in healthy subjects (P = 0.688), but was different in persons with LBP, illustrated by shallowing of the slope at the last 30s of the test (P = 0.008). A between muscle comparison in the LBP group showed greater non-linear behavior in the deep multifidus (painful region) in contrast to T10 longissimus thoracis (nonpainful region) (P = 0.013). Possible explanations for these findings are discussed.