Clinical Correlates of Pressure Pain Thresholds in Back and Leg Pain

Across manual therapy professionals there is at present little agreement regarding how to quantitatively measure painful spinal lesions associated with uncomplicated back and/or leg pain.{Waddell, 1996 #564;Hegmann KT, 2019 #16740;Himelfarb I, 2020 #16733} In the United States, the Medicare program requires "pain and tenderness" reportage as a metric to diagnose spinal lesions (segmental dysfunction, or SDF) associated with uncomplicated back pain, prior to reimbursement of treatment by chiropractors.{Services, 2019 #16731} Medicare guidelines for chiropractors specifically list use of algometry as an acceptable way to record paraspinal tenderness.{CMS, 2019 #16198} However, research regarding paraspinal algometry to measure tenderness has to date yielded conflicting results.{Jung, 2023 #16196} Medicare suggests use of pain scales such as the Numeric Rating Scale (NRS) for reporting pain levels before, during, and after chiropractic care to determine when patients have achieved maximum improvement, are pain free, and therefore no longer eligible for reimbursement of spinal manipulation (SM), the primary component of chiropractic manipulative therapy (CMT).{CMS, 2019 #16198} While there is some prior research that correlates pain with paraspinal tenderness measured using algometry, there is no body of literature correlating these findings with other commonly used clinical variables required by Medicare for documentation, either before or after CMT.{Leach, 1993 #15773;Jung, 2023 #16196;Nim, 2022 #16201} For example, both Medicare and chiropractic practice guidelines advocate for clinicians to distinguish uncomplicated back pain associated with facet joint lesions (also considered SDF), from back and leg pain that may be caused by disc lesions. One of the clinical tests for this is a pain provocation measure known as the Kemp Test (or Kemp; the patient extends their trunk backwards and to the right or left, to see if back and/or leg pain are reported. Complaint of back pain only suggests "facet syndrome" while complaint of leg pain suggests "disc syndrome.").{CMS, 2019 #16198;Hawk, 2020 #16139;Editors, 2024 #16738} As presently used there is only weak clinical evidence for use of pain provocation tests such as Kemp Test, and we found no prior research comparing Kemp Test results with other outcome variables after CMT.{Editors, 2024 #16738} Among clinical variables validated by research, reported extensively in manual therapy literature, and advocated in the Medicare guidelines for documentation by chiropractors, aside from NRS pain scores, only use of self-reported measures such as the Oswestry Lower Back Pain Disability Questionnaire are fully validated and operationalized.{Fairbank, 2000 #16739;Hawk, 2020 #16139} Yet even this dependent variable has only rarely been correlated with paraspinal tenderness.{Leach, 1993 #15773} Only NRS pain and Oswestry measures have been used extensively in reportage of outcomes after CMT.{Clohesy NC, 2018 #16743;Hawk, 2020 #16139;Himelfarb I, 2020 #16733} Neither algometry nor the Kemp Test have been previously compared with Oswestry and NRS scores both before and after CMT, to determine whether these reported measures of SDF improve after chiropractic, or even whether they correlate with one another. This lack of research regarding promising and/or commonly used chiropractic dependent variables may factor into our inability to clinically define the Medicare diagnosis SDF, and may instead serve to perpetuate the "enigma of back pain."{Waddell, 1996 #564}

Differences between instruments and protocols used in clinical trials, performed only on pain free subjects, using only one or a few sessions of SM, and with small sample sizes may have contributed to prior conflicting reports regarding the ability of algometry to distinguish pain free from painful lower back muscles; also, studies conducted in university or controlled environments may lack generalizability to clinical practice.{Jung, 2023 #16196} When an examiner measures paraspinal tenderness by using an algometer asking the patient to say "yes" when discomfort is first noted, the corresponding value read from the instrument is termed the pressure pain threshold (PPT). Emerging evidence that the number and frequency of CMT sessions may impact both short and long term outcomes gives rise to the question as to whether paraspinal tenderness is affected by the number and frequency of treatments as well.{Haas, 2004 #4710;Haas, 2014 #15996} For example, would SM twice a week for 4 weeks increase paraspinal PPTs and reduce PPT asymmetry (the difference between paraspinal tenderness on the right versus the left) more significantly than SM provided only once a week for 2 weeks? Extending the prior PPT work by reporting tenderness quantified by algometry along with other commonly reported and operationalized clinical measures, determining whether the variables improved as expected after care, and correlating the measures before and after chiropractic may help inform future prospective research of their validity with regard to measurement of SDF within the Medicare program.