Pressure threshold meter: its use for quantification of tender spots.
The pressure threshold meter (PTM) and its use for evaluation of tender spots and trigger points are described. Pressure threshold is the minimum pressure inducing pain or discomfort. The PTM consists of a force gauge (11 kg range) to which a rubber disc with lcm2 surface is attached. This surface has been proven adequate for quantification of deep tenderness in soft tissues. Normal threshold values were established in 50 volunteers, 24 men and 26 women, at nine different sites frequently affected by trigger points, including the trapezius, supraspinatus, infraspinatus, teres major, lumbar paraspinals (2 sites), gluteus and pectoralis muscles. The deltoid, where muscle sensitivity is usually normal, was used as a reference. PTM is used clinically for quantification of tenderness for medicolegal purposes, but primarily to prove the presence of trigger points to patients and health professionals. Reaction to various forms of treatment such as physiotherapy and drugs can be assessed quantitatively. When trigger point injections are properly administered to affected areas, pressure threshold measurements usually increase by 4 kg/cm2. Failure to increase the reading indicates that the injection was incomplete and the procedure should be repeated. The PTM can be used for monitoring tenderness, inflammation, arthritis activity, and fibrositis.