AbstractLow Back Pain (LBP) is a condition that most people experience at least once in their lifetime and for which many will seek physiotherapeutic intervention. Recently published and internationally recognised clinical guidelines for the management of LBP recommend the use of spinal manual and manipulative therapy techniques alongside exercise, advice, education and pharmaceutical therapies, particularly in the early stages. Other areas of development in the last decade include classification systems, clinical prediction rules (CPR’s), patient-reported outcome measures (PROMS’s) and minimum clinically important difference (MCID) thresholds. Additionally, sympathetic nervous system (SNS) measures of treatment responses are now recognised as providing quantifiable indicators of peripheral, spinal and central effects of manual therapy interventions although research in the lumbar spine is very limited with none providing data on a patient population.
The aims of the study were; to determine the reliability and stability of the Biopac System in recording skin conductance (SC) activity levels and calculate the smallest real difference (SRD) statistic; to generate data on the magnitude of SC response to two commonly utilised treatments for LBP; and to observe the changes in a clinical population receiving guideline-endorsed physiotherapy treatment for the management of acute and sub-acute LBP. Furthermore, clinical data analysis sought to identify correlations of SC measures to PROM’s and evaluate the feasibility of using SC responses as a predictive tool for therapeutic outcome.
The ability of the Biopac System to reliably record SNS activity was established by using SC measurements with 12 participants on two occasions, one-week apart. Data was recorded within a natural, non-laboratory setting. Results established that SC measurements could be reliably recorded between data sessions with a measurement variability of; ICC=0.99 (p<0.005) with an SRD value of 0.315 μmho’s (4.633%). In conclusion, any SC change above the SRD could be regarded as an SNS change that is independent of any measurement error or variability thus representing a real change ascribable to the intervention under investigation.
The pre-clinical investigation compared the magnitude of SC response (SCR) of two, independently administered, specific MT techniques, applied, after randomisation, to the Lumbar 4/5 segment of 50 asymptomatic healthy volunteers. Treatments included; a rotatory lumbar manipulation technique or a repeated McKenzie extension in lying exercise. Findings revealed that both techniques produced statistically significant changes in SNS activity in the lower limbs (> SRD) with manipulative technique SCR’s (76%) that were twice the size of the McKenzie repeated extension in lying exercise (EIL) technique (35.7%)( p=0.0005). Only the manipulation technique had a lasting effect that was carried into the final rest period (p=0.012) but the SNS response was not a side-specific phenomenon (p= 0.76).
The final clinical study recruited 60 acute and sub-acute LBP patients (symptoms of up to 12 weeks duration) who received guideline-recommended physiotherapy treatment within a hospital-based musculoskeletal out-patient physiotherapy department. SCRs were recorded throughout all treatment episodes with standardised, validated PROM’s used for comparison of status at inception, mid-point and at discharge. Functional impairment was determined using the Oswestry Disability Index (ODI) and the Roland Morris Disability Questionnaire (RMDQ) with pain intensity evaluated with the Narrative Pain Rating Score (NPRS).
A preliminary comparison, between the asymptomatic population and a random selection from the patient population, revealed that patients had treatment SCR’s that were significantly greater (three-fold) than those of the asymptomatic groups (manipulation, p=0.003; EIL exercises p=0.001).
Analysis of the patient data indicated that pre-treatment/baseline SC activity levels in the inception data capture point were lower than at discharge (18 µMho’s; p<0.0005) but, conversely, that treatment SC levels were initially high, but diminished in magnitude by discharge (230 to 172 µMho’s; p<0.0005) representing a SCR reduction of 125%. Correlational analyses of change scores of maximum SCR’s to PROM’s, from inception to discharge suggested weak positive correlations of SCR treatment responses to functional disability score improvements (rho 0.278) and pain intensity reductions (rho=0.229) that were significant for function (p=0.033) but not significant for pain (p=0.080). The final analyses indicated that there were trends in the magnitude of response to specific elements of treatment with manipulation having the largest SCR (266%). Further evaluative analysis of SC readings as a predictor, at inception, of functional outcome, at discharge indicated that a critical/cut-off value of 195% may indicate those patients least and most likely to respond positively to MT treatment. Preliminary logistic regression analysis indicated that the 195% SCR value was excellent at identifying poor responders but less successful at identifying good responders, functionally, to treatment. Nonetheless, SCR was a better predictor of outcome than duration of symptoms and patient age. Characteristically, patients achieving the 195% value were most likely to have higher functional disability and pain intensity scores at inception but by discharge had required fewer treatments, had greater overall functional improvement and lower pain intensities than those not achieving this threshold.
In conclusion, SC activity levels and SCR’s may be a reliable, stable, alternative and objective measure of LBP patients’ SNS status and changes that occur as a result of symptom abatement throughout a course of physiotherapy treatment. SC readings may (indirectly) reflect the state of dorsal horn (DH) sensitisation and of the central nervous system (CNS) processing system and its facilitatory capacity to activate the descending pain inhibitory system (DPIS). Further research, in patient populations (including chronic LBP patients), is recommended to verify these findings and validate the 195% SCR cut-off point. Definitive RCT’s are indicated to further the understanding of guideline-endorsed physiotherapy treatment (a complex intervention –MRC, 2000) and to determine whether the SNS activity measurements can be used to help classify, predict, and ultimately, direct the care of patients with LBP.
|Date of Award||2013|
|Supervisor||Paul J. Watson (Supervisor)|
- manual therapy interventions
- low back pain