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Change in Muscle Thickness in Response to Treatment for Low Back Pain

The cause of most low back pain (LBP) remains unknown. Without a way to categorize LBP patients based on pathology, health care providers use two other approaches to classification. The first is treatment-based classification (TBC). The second is impairment-based.

The TBC system places acute LBP patients into one of four treatment groups. Each group has a set of exercises to perform. This direction-specific program includes flexion or extension, mobilization or manipulation, core training, and traction.

In this study, physical therapists use rehabilitative ultrasound imaging (RUSI) to assess deep muscle function in patients with LBP. RUSI is the use of US by rehabilitative specialists for biofeedback and to measure muscle performance. RUSI can be used to assess deep muscle function.

The goal was to measure the amount of change in muscle thickness in the lumbar multifidus (LM) and transverse abdominis (TrA) muscles. These two muscles are deep spinal stabilizers. Muscle thickness was measured for the TrA while actively pulling the stomach in toward the spine. The same measurements were taken for the LM during an arm lifting activity.

A second aim of the study was to see if changes in muscle thickness are different for patients with LBP based on how long they had painful symptoms. Measurements were compared between two groups. The first group had LBP and were referred to physical therapy for treatment. The second (control) group had no history of LBP and no current symptoms of back pain.

The authors reported that muscle thickness change of both muscles was different between the patient and control groups. There was no difference in muscle thickness among the patients in the four TBC-treatment groups. In other words, all back pain patients had changes in the thickness of the deep spinal stabilizers. Subcategories of patients with LBP had the same changes.

Differences in muscle thickness were also observed based on duration of symptoms. The results of this study point to the need for further RUSI research. Studies are needed to show if muscles thickness change can be reversed with treatment. And if so, which treatment works the best?

References: Kyle B. Kiesel, PT, PhD, et al. A Comparison of Select Trunk Muscle Thickness Change Between Subjects with Low Back Pain Classified in the Treatment-Based Classification System and Asymptomatic Controls. In Journal of Orthopaedic & Sports Physical Therapy. October 2007. Vol. 37. No. 10. Pp. 596-607.

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