(924.5) Anatomical Study of the Innervation of the Fibularis Longus (FL) Muscle and its Correlation with Miofascial Trigger Points: Preliminary Results

Poster Board Number: C93

Lucas Park (University of São Paulo), Flávia Akamatsu (University of São Paulo), Flávio Hojaij (University of São Paulo), Mauro Andrade (University of São Paulo), Alfredo Jacomo (University of São Paulo)

Background:  Myofascial syndrome is a common cause of chronic musculoskeletal pain and results in dysfunction of the affected muscles. It is characterized by myofascial trigger points (MTPs) which are clinically identified by palpation of a muscle or fascial taut band. Previous publications have found MTPs to coincide with neuromuscular junctions at the innervation zone (IZ). The fibularis longus syndrome is one of the most frequent myofascial syndrome of the lower limbs and occurs due to a wide variety of etiologies, most commonly, overuse and ankle sprain. Referred pain and tenderness caused by the trigger points of the FL muscle are located above, behind and below the lateral malleolus and may extend along the lateral aspect of the foot and leg.


Objective:  Our study aimed to correlate the innervation of the FL muscle to clinically described MTPs.


Methods:  FL muscles from five cadavers were dissected to observe the exact point where nerve fibers penetrated the muscle belly. As muscle size varies among individuals, we describe the relative entry point of the nerve into the muscle by defining four different areas in 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. 


Results:  We found a mean of 12 branches of the superficial fibular nerve to the FL muscle. All of them were located into the areas I (67%) and II (33%). No branches were observed in areas III and IV. Our findings corresponded to previously described MTPs.


Conclusion: Anatomical correlation between MTPs may be a useful tool for a better understanding of the physiopathology of these disorders and may provide a rational basis for their treatment.