Background: Trigger point (TrPs) identification has become the mainstay of diagnosis for the treatment of Myofascial Pain Syndrome; however, manual pressure (MP) to identify TrPs by determining low-pressure pain threshold has low interrater reliability and may lack validity since it is done on inactive muscles. To elicit contractions and mimic an active muscle or movement that "causes" pain, a Muscle Pain Detection Device (MPDD) has been developed. A selected muscle is stimulated and painful muscles are precisely detected, allowing distinctions between primary and referred muscle pain as well as distinguishing other functional muscle pain thought to cause MPS.
Methods: An IRB approved randomized controlled study is presented of MP (20 patients) control vs MPDD (20 patients) to identify which muscle(s) was the source of pain in subjects presenting to the NYU Pain Management Center with a minimum 3 months history of back pain. Patients were unaware of their diagnostic method. Subjects were injected in 1-3 sites identified via MP or MPDD by a separate, blinded physician. Prior to, and following treatment at one week and one month, the patients were administered Oswestry and visual analog scale pain questionnaires by a blinded evaluator, and their range of motion was measured by a blinded physical therapist.
Results: The MPDD group reported significantly larger improvements in pain, mood and Oswestry scores compared with the control (P < 0.05). Moreover, the MPDD group reported 82.5% pain relief at 1 month, compared with 53.2% in the control (P < 0.001). The range of motion measurements failed to reveal any significant difference between the groups.
Conclusions: Using the MPDD appears to be more valid and potentially more reliable than palpation to identify muscles causing regional pain that could benefit from injections.