Conditioned pain modulation (CPM) a measure of the effectiveness of the descending pain pathway and therefore a measure of the body's ability to perform endogenous analgesia. In subjects with normal function of the descending pain pathway, the net-effect during CPM testing is anti-nociceptive, or inhibition of the ascending pain pathway. In those with impaired descending pain pathway function, the response to CPM testing is pro-nociceptive, indicating that the body is unable to inhibit the pain signal, or may even amplify it. There is literature that supports the presence of impaired CPM, and therefore impaired descending pain pathway function, in numerus chronic pain conditions, including low back pain. Impaired descending pain pathway function may be contributing to this chronic pain presentation. This study will give us information on whether a typical physical therapy plan of care is able to improve impaired CPM, and if CPM values are predictive of improvement in physical therapy.
DEERS eligible
English speaking
Age 18-64 years
ODI baseline ≥25%
Serious spinal pathology (acute fracture, active cancer, inflammation, inflammatory arthropathy)
Low back pain symptoms radiating below the knee
Pregnancy
Diagnosed neurological disease including traumatic brain injury, multiple sclerosis, chronic regional pain syndrome, and fibromyalgia.
Single group
Physical therapy
Other interventionThe intervention will be physical therapy standard of care.
Modified Oswestry Disability Index
The ODI will be the primary outcome for this study. The ODI contains 10 items that assess function and disability (0 = no disability, 100 = maximal disability).
Central Sensitization Inventory
The CSI is a 25-item questionnaire that assesses symptoms common to central sensitization syndromes using a 0-100-point scale, in which 100 indicates a higher level of symptoms common to central sensitization.
Conditioned pain modulation
CPM calculation: It is recommended that CPM response be reported as an absolute value and percent change. The calculation for absolute value is: CPM = PPTpre -PPTconditioning. PPTpre is the testing stimulus conducted before conditioning stimulus application and PPTconditioning is the testing stimulus conducted during conditioning stimulation. This is expressed in kPa. A negative value suggests that CPM is functioning effectively and indicative of an anti-nociceptive profile, while a positive value suggests CPM is impaired and indicative of a pro-nociceptive profile. The second method will be CPM expressed as percent change of the testing stimulus before and during the application of the conditioning stimulus. The equation for percent change is: \[(postPPT - prePPT)/prePPT\] \* 100. CPM will be expressed as continuous ratio data via absolute value and percent change. The absolute value score will be used for the statistical model and will be collected at baseline and follow up.
Temporal Summation
Temporal summation is calculated as follows: VAS10th - VAS1st. A positive number indicates the magnitude of temporal summation of pain. This will be expressed as continuous ratio data and will be collected at baseline and follow up.
Numeric pain rating scale
The NPRS is an 11-point numerical pain rating scale used to measure pain. Patients rate pain ranging between 0 (no pain) and 10 (worst pain imaginable). This will be measured as the mean of three pain ratings: best pain rating over 24 hours, worst pain rating over 24 hours, and current pain rating.
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