Elsevier

Manual Therapy

Volume 10, Issue 2, May 2005, Pages 116-126
Manual Therapy

Original article
Ultrasound imaging of lumbar multifidus muscle: normal reference ranges for measurements and practical guidance on the technique

https://doi.org/10.1016/j.math.2004.08.013Get rights and content

Abstract

This cross-sectional, prospective study aimed to produce normal reference data for measurements of the lumbar multifidus muscle. A total of 120 subjects, 68 females (aged 20–64 years) and 52 males (20–69 years) were studied. Bilateral transverse ultrasound images were made of multifidus at the fourth and fifth lumbar vertebrae (L4 & L5). Cross-sectional area (CSA, cm2) and linear dimensions (AP, anteroposterior; Lat, lateral) were measured and the latter expressed as a ratio (AP/Lat) to reflect shape. Relationships between CSA and anthropometric measures were examined. Multifidus CSA was larger in males (P<0.001) and age had no effect. The CSA was larger at L5 than L4 (P<0.001) and highly correlated between the two levels (males r=0.82, females 0.80). Differences in muscle shape were observed for gender, age and vertebral level. Between-side symmetry was high for size but not shape (CSA <10% difference). Linear measurements multiplied (AP×Lat) correlated highly with CSA (all groups r⩾0.94, P<0.0001). The AP dimension was also acceptably predictive of CSA at L4 (r⩾0.79). There were no clinically useful correlations between CSA and anthropometric measures. These findings provide normal references ranges for objective assessment of lumbar multifidus. This paper also addresses specific practical issues when scanning multifidus.

Introduction

Ultrasound imaging of the lumbar multifidus muscle is of increasing interest to physiotherapists, both for clinical and research purposes. Clinically, the application is twofold: as an objective assessment tool for detecting abnormalities and monitoring changes during recovery (Hides et al., 1996, Hides et al., 1994); and for visual biofeedback during re-education of muscle contraction (Hides et al., 1998).

The characteristics of multifidus for which normal data are available include cross-sectional area (CSA), linear measurements and shape, in small and relatively young populations (Hides et al., 1992, Hides et al., 1994).

Measurement of muscle size using ultrasound has provided an accurate assessment of muscle wasting in various muscles (see Stokes et al., 1997 for review). In acute low back pain (LBP), severe atrophy of multifidus was found to be selective and confined to the vertebral level and side of pain symptoms (Hides et al., 1994). The technique was also useful in demonstrating that multifidus size does not recover when pain subsides unless it undergoes specific exercises (Hides et al., 1996). For the technique to be applicable to populations other than those studied previously, normal data are required for subjects over a wider age range.

Of the various skeletal muscles explored with ultrasound scanning (see Stokes et al., 1997 for a review), lumbar multifidus is one of the most difficult to image and interpret. This is mainly because its lateral border with longissimus (an erector spinae muscle) is often not clear enough to see without refinements in the procedure.

When imaging multifidus, it is important to understand its functional anatomy, the main feature of which is the segmental arrangement of its fibres (Bogduk, 1997; Bogduk et al., 1992; Macintosh et al., 1986). Multifidus has both movement and stabilising roles. Working bilaterally with the other lumbar muscles, multifidus produces extension of the lumbar spine (Bogduk et al., 1992) and acts as a stabilizer in rotation, counterbalancing the flexion force produced simultaneously with rotation by the oblique abdominal muscles (Bogduk, 1997). Knowledge of this functional anatomy assists in imaging the muscle and using various manoeuvres for biofeedback.

The present study examined multifidus size and shape in normal subjects, and sought predictive equations for estimating the expected size. The paper also provides practical details of the imaging technique to help obtain and interpret scans.

Aims

  • 1.

    To provide reference ranges for multifidus size and shape at vertebral levels L4 and L5 in normal males and females over a wide age range.

  • 2.

    To investigate the degree of symmetry of multifidus size and shape.

  • 3.

    To examine the relationship between multifidus size and various anthropometric variables to provide predictive equations for muscle size.

Section snippets

Methods

Real-time ultrasound images of lumbar multifidus were taken bilaterally at vertebral levels L4 and L5.

Results

Multifidus CSA was significantly greater in males than females and also larger at L5 than at L4. Age had a significant effect on shape but not size. There were statistically significant correlations between CSA with SPL and lamina width but were not considered clinically significant to enable accurate prediction of multifidus size. High correlation between L4 and L5 CSA enables the size of one to be predicted from the other using regression equations. Linear measurements were more predictive of

Discussion

Reference ranges for multifidus size and shape were produced for normal subjects of different ages. Muscle size was influenced by gender and vertebral level but not age. The CSA can be estimated from the muscle's linear measurements or the CSA of the muscle at the adjacent vertebral level. None of the anthropometric measures were predictive of muscle size.

Conclusions

Assessment of multifidus size can be made by comparison with the 95% reference ranges reported. Separate data are needed for each gender and vertebral level but not for different age groups up to 69 years. Further data are needed for populations of different activity levels and specific sports, and people over 70 years. Changes in quality of muscle tissue with age require investigation.

Shape varied considerably amongst normal subjects, suggesting that it may be inappropriate to describe a

Acknowledgments

The authors thank the subjects at the Royal Hospital for Neuro-disability who took part in the study, Dr Anthony Swan for statistical advice and data analysis, and the Neuro-disability Research Trust for financial support.

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