Pain scales, like that with the visual analog scale (VAS) and the numerical rating scale (NRS), are used to measure pain in musculoskeletal management. However, because pain is a subjective experience, the validity of these pain scales often come into question. Most recently, a research paper in the Journal of Experimental Social Psychology 1, researchers questioned the impact of the scale itself on the pain rating. That is, did one measurement affect a second measurement? Did the actual pain scale alter the sequential readings?
Matching Pain and MRI Findings
Above that, there has been confusion about matching physical findings to these pain scales. In one breath, a popularized paper showed that many people have physical findings of degenerative disc disease and at the same time do not have symptoms 2. However, a second paper by the same authors (and not so popularized) showed people with pain are more likely to have degenerative findings on MRI 3. And yet, many practitioners are bypassing the degenerative changes found in these MRI scans and struggle in connecting those symptomatic patients to their own anatomical findings. As Stuart McGill often says, the MRI tells a story of one’s back history of wounds and scars. Scars, which are gristled old injuries are tagged by radiologists as degenerative findings which can come in the form of disc height loss, disc bulges, facet arthropathy, and numerous other labels. However, the wounds which are more acute, are only determined by a careful assessment. Radiologists report on these findings too but it is very difficult for them to determine where the pain is being derived from.
Simply pressing on anatomical structures can increase or in some cases decrease pain. In the case of manual therapy during motion palpation of joint play to determine joint mobility and sensitivity, this often can increase or decrease the pain in the back pain patient. This investigation is a common practice by physiotherapists, chiropractors, osteopaths and orthopaedists and will include watching, or asking the patient whether this or that pressure hurts. Using a visual analog scale, in this case, is not very useful as the pain will vary based on the pressure the practitioner places on specific areas of the back, for example.
More current research is beginning to reveal a concept of motion sharing in the spine. Breen at al. 4 demonstrated that uneven motion between the vertebral motion segments contributes to the chronic pain, non-specific back pain people. (Non-specific back pain refers to mechanical back pain and not pathological) This research is beginning to shape our understanding of the origins of back pain as it relates to hypermobility. Some vertebral segments move more than others and it is beginning to look like those spinal motion segments may be contributing to the pain sources. And if this is the case, which it is beginning to look like, in the palpatory investigation of the patient by the practitioner, joints that move too much could likely be revealed by simply pressing on particular anatomical landmarks and extracting from the patient whether that movement is symptomatic.
Clearly the measurement of pain as it relates to a specific patient is challenging. However, as we are beginning to see, hypermobility or uneven motion sharing is making its case. This supports the work by Kirkaldy-Willis 5. With the advent of advancing techniques in MRI and fluoroscopy it may be time to begin to attempt extract more real-time data from the patient. Stay tuned with Dynamic Disc Designs Corp. Innovation is in our blood.
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