Algometry in Diagnosis of Musculoskeletal Pain and Evaluation of Treatment Outcome: An Update

SUMMARY

This is an updated review (1) of pressure algometry [PA] as employed for quantification of tenderness in diagnosis of tender spots [TSs], trigger points [TrPs], fibromyalgia [FMS] and muscle spasm. The pressure pain threshold [PPT], i.e., the minimum pressure that induces pain or discomfort expresses the degree of sensitization affecting the nerve fibers by sensitizing substances.

This relation seems to be linear. The clinical use of PA includes the following:

Diagnostic Applications

1. Quantification of tenderness in myofascial and other musculoskeletal pain. The critical level of abnormality has been established as a 2 kg/cm² lower threshold relative to a normal control point, usually selected over a contralateral corresponding site. This criterion is applicable for diagnosis of TSs, which cause local pain in the maximum point of tenderness, and TrPs which induce referred pain in a distant area. Point tenderness which is quantified by algometry is the most consistent and reliable finding for diagnosis of TrPs and TSs.

2. Tender points that are diagnostic of FMS can be evaluated quantitatively by algometry. The critical pressure is 4 kg/cm².

3. Activity of arthritis and other inflammatory conditions can be quantified.

4. tenderness of subcutaneous layers [corresponding to pinch and roll sensitivity] can be quantified by algometry and differentiated from deep tissue [muscle] tenderness.

5. Medicolegal applications of PA include quantitative documentation of abnormal tenderness. Reproduction of results on repeated measurements can rule out malingering.

Evaluation of Treatment Results

1. The immediate effect of treatment particularly injections of TrPs and TSs can be assessed. Failure to increase PPT after injection indicates inadequate treatment and the need for reinjection. Physical modalities and stretching have been successfully evaluated by PA. Efficacy of “preinjection blocks,” which prevent pain caused by needling and infiltration of TrPs and TSs can be quantified.

2. Long-term outcome of treatment can be quantified. A good correlation between improvement of pain and increase in PPT indicates that the treated TSs or TrPs were the immediate cause of the patient's complaints.

3. Effects of systemic painkillers and anti-inflammatory medications can be assessed.