The use of ultrasound imaging to evaluate the thoracolumbar fascia in people with and without lower back pain

Chronic lower back pain remains a poorly understood multi-factorial condition, associated with reduced quality of life and function. Traditionally, research in lower back pain has focused on vertebrae, trunk muscles, motor control and biopsychosocial factors. Despite this substantial body of research, chronic lower back pain remains a prevalent global issue affecting health and well-being. Recently, the thoracolumbar fascia has been recognised to play a role in the pathophysiology of chronic lower back pain. Currently, there are no standardised methods for imaging and analysis of the thoracolumbar fascia. This thesis seeks to advance methods of analysis as well as furthering our understanding of role thoracolumbar fascia plays in chronic lower back pain.

The study presented in Chapter 4 aims to assess the reliability of intra- and inter-image reliability of ultrasound images of the thoracolumbar fascia. One investigator acquired and measured ultrasound images of eleven participants. The morphology of the thoracolumbar fascia was measured using an adapted grey-scale MatLab script to measure the echogenicity and an on-screen cursor to measure the thickness of the dense connective tissue layers. The investigator measured the same series of images on day 1, and 2 days later. The investigator acquired a further set of images from the same participants 4 days later. Both sets of images were analysed 3 months after image acquisition. The intraclass correlation coefficient (ICC) for same image (intra-image) reliability was >0.94, which represents good reliability. The ICC for inter-image reliability of scans taken across 2 days of the same participants, ranged between >0.95 - 0.63, which represents good to moderate reliability. Inspection of Bland Altman Plots revealed no systematic pattern of variability. It was concluded that ultrasound is a reliable method to evaluate the thoracolumbar fascia, when using one investigator.

The study presented in Chapter 5 used ultrasound to investigate the thickness and echogenicity of the thoracolumbar fascia in people with and without back pain. One hundred and forty-one participants took part in the study (74 with back pain, 67 without back pain). This study found that the echogenicity (brightness of pixels indicating presence of collagen) of the thoracolumbar fascia in people with lower back pain was 10% higher (p = 0.04), compared to people without lower back pain. Higher echogenicity suggests tissue fibrosis, as found in other pathological connective tissues.

The study reported in Chapter 6 was an investigation of the impact of a 4 week endurance training programme on the ultrasound outcomes of the thoracolumbar fascia. This study found no difference in either thickness or echogenicity in either the training group or the control group. This could be an indication that a longer training intervention is required in order to visualise changes in the thoracolumbar fascia, using ultrasound imaging.

The study presented in Chapter 7 was an inter-rater reliability study in which 30 medical practitioners rated the morphology of the thoracolumbar fascia of 30 ultrasound images of 30 individuals. The scans were rated on a Likert-type scale ranging from 5 being very disorganised, to 1 being very organised. Images were selected by a focus group and consisted of a representative range of thoracolumbar morphologies. This study found that medical practitioners can reliably rate scans, regardless of ultrasound experience (Cronbach's alpha - 0.98).

The conclusion of this thesis is that ultrasound is a reliable imaging method to evaluate the thoracolumbar fascia. Furthermore, higher echogenicity was found in images of people with lower back, which could be an indicator of fibrosis. Ultrasound is a viable and promising method to evaluate the thoracolumbar fascia, which has been associated with lower back pain.

These findings contribute to the emerging field of research into the pathophysiology of the human fascial system.