1 - Anatomical Subtract of the Flexor Pollicis Brevis Muscle Myofascial Trigger Points

Poster Board Number: 1
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Abstract Body : Background: Myofascial syndrome is a common cause of chronic musculoskeletal pain and is characterized by myofascial trigger points (MTPs). MTPs are clinically identified by palpation of a muscle or fascial taut band. Although pathophysiology of MTPs remains unclear, coincidence between them and muscle motor plate at the innervation zone (IZ) have been reported. One of the integral functions of the intrinsic muscles is thumb to index finger key and tip pinch. This function is important for many activities of daily living such as using keys, holding eating utensils, getting dressed (buttons and zippers), holding a toothbrush, opening small caps, and tearing open packages. The intrinsic muscles primarily involved in this action are the adductor pollicis (AP) muscle, the first dorsal interosseous (DI) muscle, and the flexor pollicis brevis (FPB) muscle. Pain dysfunction problems as myofascial pain can produce extremity discomfort affecting the function of the hand. Clinical reports usually describe trigger points in tenar muscles, and we aimed to identify correlation with the pattern of muscle innervation.
Methods: We dissected the flexor pollicis brevis (FPB) muscles from four cadavers to observe the exact point where nerve fibers penetrated the muscle belly. As muscle size varies among individuals, we considered the entry point of the nerve branch in four different areas of the muscle belly: two superior (I, II) and two inferior (III and IV). Statistical analysis of anatomical data was obtained by Poisson distribution and logarithm link function followed by Bonferroni multiple comparisons. The comparison of points between sides was made by Mann-Whitney test. Data are presented as mean ± standard deviation, and the level of significance was adjusted to 5% (p < 0.05) for all tests.
Results: The number of nerve branches did not differ between sides. Areas I, II, III and IV were also similar regarding the number of nerve entry sites (1±1).
Conclusion: Location of nerve entry points into the FPB muscle can be useful to identify the myofascial trigger points (MTPs) and guide therapeutic procedures.