Do Responders to Spinal Manipulative Therapy Differ Biomechanically From Nonresponders or Controls?
Summary by Dean L. Smith, DC, MS, PhD, ICCSP
Reference: Wong AY, Parent EC, Dhillon SS, Prasad N, Kawchuk GN. Do Participants With Low Back Pain Who Respond to Spinal Manipulative Therapy Differ Biomechanically From
Nonresponders, Untreated Controls or Asymptomatic Controls? Spine (Phila Pa
1976). 2015 Sep 1;40(17):1329-37.
Spinal manipulation is a common intervention for low back pain (LBP). Most research on chiropractic has focused on spinal manipulation (adjustment). As with any intervention, not all participants in randomized clinical trials report benefit with spinal manipulation. Several ways to address this differential response to spinal manipulation therapy (SMT) include psychosocial factors (e.g. expectation), the generation of clinical prediction rules (CPR) to identify SMT responders and observing biomechanical and neurophysiological characteristics (e.g., multifidus contraction thickness, water diffusion within lumbar discs, spinal stiffness). The goal of this paper was determine whether patients with LBP who respond to SMT differ biomechanically from nonresponders, untreated controls, or asymptomatic controls.
Participants aged 18 to 60 years with or without LBP were included in the study. LBP participants included those with or without leg symptoms, had at least 2 on the 11-point numeric pain rating scale, and modified Oswestry Disability Index (mODI) score of at least 20%. Exclusion criteria were “red flag” conditions, signs of nerve root compression, scoliosis, osteoporosis, joint hypermobility syndrome, previous lumbosacral surgery, and SMT/stabilization exercise treatment in the last 4 weeks. LBP individuals were enrolled into either the treatment ( + LBP/ + SMT) or untreated LBP control ( + LBP/-SMT) group if they possessed either (a) 4 or more of 5 CPR characteristics (predicted responders) or (b) 2 or less CPR characteristics (predicted nonresponders). Specifically the CPR were: 1. duration of current episode of symptoms < 16 days; 2. location of symptoms not extending distal to the knee; 3. scores on the Fear Avoidance Behavior Questionnaire (FABQ) work subscale < 19 points; 4. at least 1 lumbar spine segment judged to be hypomobile; 5. at least 1 hip with more than 35 degrees of medial rotation range of motion (ROM).
Approximately equal proportions of CPR-predicted responders (43.8%) and nonresponders (56.2%) were enrolled into the + LBP/ + SMT or + LBP/ − SMT group. Asymptomatic controls were enrolled with inclusion criteria of no current LBP and no history of LBP that required sick leave in the past year.
Participants With LBP Receiving SMT ( + LBP/ + SMT): 32 participants in this group completed 3 sessions. Session 1 included demographics, clinical examination, mODI. Three biomechanical outcome measures were collected before/after SMT: spinal stiffness, lumbar multifidus (LM) contraction thickness and apparent diffusion coefficient (ADC) of each lumbar disc. On session 2 (3–4 d later) the same variables were repeated with the exception of ADC. During session 3 (day 7), only spinal stiffness and LM contraction were collected together with the mODI. SMT involved a supine patient receiving a posteroinferior thrust to the patient's pelvis. A maximum of 2 thrusts were delivered to each side of the subject during each session.
Participants With LBP Not Receiving SMT ( + LBP/ − SMT): A group of 16 LBP controls were taken through the same procedures outlined for session 1 but did not receive SMT or any further sessions.
Asymptomatic Participants Not Receiving SMT ( − LBP/ − SMT): 59 asymptomatic participants completed sessions 1, 2, and 3 without SMT and without ADC measurement. Based on assessment at session 3, + LBP/ + SMT participants were classified as SMT responders (a cutoff of ≥ 30% reduction in baseline mODI scores) or nonresponders ( < 30% reduction in baseline mODI scores). The ADC values in the first and second scans of + LBP/ − SMT participants were compared with those of SMT responders/nonresponders. The spinal stiffness and LM thickness of SMT responders/nonresponders at various measurement time points were compared with those of − LBP/ − SMT participants.
Spinal Stiffness: Measured by a mechanical indentation device at the L3 spinous process
LM Thickness Ratio: Quantified at the L3-4 and L4-5 levels by ultrasound on the symptomatic side for those with LBP and on a random side for asymptomatic participants. All participants lay prone and raised a light weight 3 times in the contralateral hand 5cm creating a 30% maximal voluntary contraction. Thickness ratios were calculated as thickness con – thickness rest /thicknessrest x 100%.
Diffusion Weighted Imaging (DWI) and ADC: DWI is a form of MR imaging and derives its image contrast from differences in the motion of water molecules between tissues. To quantify lumbar disc diffusion, the ADCs of all lumbar IVDs were measured from the midsagittal ADC maps. ADC is a measure of the magnitude of diffusion (of water molecules) within tissue.
· After assessment of mODI results, 15 participants with LBP were classified as SMT responders and 17 as nonresponders
· Spinal stiffness: Stiffness of SMT responders was significantly reduced after each SMT and was maintained at day 7 whereas SMT nonresponders and − LBP/ − SMT group showed no such change
· LM thickness ratios: SMT responders demonstrated significant increases in LM thickness ratios after the first SMT and were sustained for more than 1 week whereas no similar change was noted in the nonresponders and the − LBP/ − SMT group
· DWI and ADC: only SMT responders had significant increases in diffusion within the L3–L4, L4–L5, and L5–S1 discs
· Participants with post-SMT improvement in disability demonstrated simultaneous changes between self-reported and objective measures of spinal function
· Responders to SMT for low back pain are characterized by an immediate and sustainable decrease in spinal stiffness and an increase in lumbar multifidus muscle thickness ratio
Immediate enhancement of lumbar disc diffusion was observed after the first spinal manipulative therapy in participants who reported improved back pain–related disability at 1 week