Short-term increase in discs' apparent diffusion is associated with pain and mobility improvements after spinal mobilization for low back pain

Abstract

Pain perception, trunk mobility and apparent diffusion coefficient (ADC) within all lumbar intervertebral discs (IVDs) were collected before and shortly after posterior-to-anterior (PA) mobilizations in 16 adults with acute low back pain. Using a pragmatic approach, a trained orthopaedic manual physical therapist applied PA mobilizations to the participants' spine, in accordance with his examination findings. ADC all was computed from diffusion maps as the mean of anterior (ADC ant ), middle (ADC mid ), and posterior (ADC post ) portions of the IVD. After mobilization, pain ratings and trunk mobility were significantly improved and a significant increase in ADC all values was observed. The greatest ADC all changes were observed at the L3-L4 and L4-L5 levels and were mainly explained by changes in ADC ant and ADC post , respectively. No significant changes in ADC were observed at L5-S1 level. The reduction in pain and largest changes in ADC observed at the periphery of the hyperintense IVD region suggest that increased peripheral random motion of water molecules is implicated in the IVD nociceptive response modulation. Additionally, ADC changes were observed at remote IVD anatomical levels that did not coincide with the PA spinal mobilization application level.

Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1

Decision tree used by the orthopaedic manual physical therapist (OMPT) to select the parameters of PA. Grades I & II corresponds to clinical group1, and grades III & IV to clinical 2 and 3, described by Maitland. Here, only grades III and IV were selected by the OMPT, ranging from III− − to III+ + and IV− − to IV+ +. When pain was greater than stiffness, the OMPT felt pain as the limiting factor of movement early in the ROM; when pain was equal to stiffness, the OMPT felt pain or stiffness as the limiting factor of movement in the ROM with both pain and stiffness present at a high level; and when stiffness was greater than pain, the OMPT felt stiffness as the limiting factor of movement in the end of the ROM with pain at a low level (P > 5/10). Anatomical level (L1-L2 to L5-S1) and location (central or unilateral) were chosen, by palpation during PA mobilization, as the most painful and stiffest sites. The slump test was considered as painful (P), when pain was radiating below the knees and not painful (no P) when not.

Figure 2

T2-weighted MRI cross section at L4-L5 IVD and ADC mappings in sagittal medial and parasagittal planes. Position of the 3 section planes are shown on T2 image (a) and their resultant ADC mappings in parasagittal right (b), sagittal medial (c), and parasagittal left (d) planes.

Figure 3

(a) T2-weighted image for an IVD classified as Pfirrmann’s grade 1 (arrow, left panel) and the corresponding diffusion-weighted image with the location of anterior, middle, and posterior ROIs used for the computation of ADC values (right panel). (b) Similar T2- and diffusion-weighted images for an IVD classified as Pfirrmann’s grade 3.

Figure 4

Mean ADC values before and after intervention, for the 9 ROIs (#1 to #9) at the 5 anatomical levels (L1-L2 to L5-S1). The color code denotes the importance of ADC values, with cold colors (blue, cyan) for low values and warm colors (red, brown) for high values. Anterior (ant.), middle (mid.) and posterior (post.) portions of the IVDs along the sagittal medial (M, ROIs #2, #5, and #8), parasagittal left (L, ROIs #1, #4, and #7) and right planes (R, ROIs #3, #6, and #9). Values before the intervention are represented by the circles in the foreground and the ones after the intervention in the background.

Figure 5

(a) Bar chart of mean and SD results for ADCall changes after PA mobilizations expressed for each of the 5 anatomical level (1: L1-L2 to 5: L5-S1) and the primary level of application of mobilizations (PA level) on the participants (L1, L3, L4 and L5). (b) Bar chart of mean and SD results for ADCall changes after PA mobilizations expressed for each of the 5 anatomical level and the grade of mobilizations (PA grade) applied on the participants (III and IV). These two plots were only drawn for exploratory graphical analyses and the ADCall changes observed for PA mobilizations level of application and grades as a function of the anatomical levels were not tested statistically.

Figure 6

(a) Scree plot of percentage of explained variances after PCA. This plot shows the proportion of total variance in the data included in the PCA for each principal component (dimensions), in descending order of magnitude. The scree plot confirms the choice of the first three components to summarize the data (cumulative percentage of variance of 65.9%). (b) PCA results: correlation circle for dimensions 1 and 2. (c) PCA results: correlation circle for dimensions 1 and 3. (d) PCA results: correlation circle for dimensions 2 and 3. The contribution of each variable to the principal axes (‘contrib’) are coded in colors, with cold colors (turquoise blue) showing low contribution and warm colors (orange) high contribution. Dim 1 (mobility), 2 (pain), and 3 (diffusion) denotes the three first dimensions or components, explaining 34, 16.6, and 15.3% of total variance, respectively.