Morphology of flexor digitorum brevis muscle in northern Tamil Nadu region-an anatomical study with phylogenetic perspective

Background and aims : "Arches of foot" formed by the combination of skeletal and a muscular element is a unique feature of evolution as an adaptation to habitual erect posture in humans. Flexor digitorum brevis (FDB) is the most superficial intrinsic muscle of the sole that present with variations frequently. The objective of this study was to find out the pattern of presentation of FDB in northern Tamil Nadu region. Material and methods: Thirty soles of 12 male and three female embalmed cadavers were dissected and FDB was observed for variations. A comparative analysis was done with previous studies. Results: Twenty five soles showed absence of FDB tendon to little toe. Three soles confirmed to the classical book description. The soles of a 62 years old male cadaver presented with a variation of FDB. It showed a separate deep slip to the 5th toe arising from intermuscular septum and from long flexor tendon with the slip found to get inserted at the base of middle phalanx bilaterally. The incidence of 83.3% absence of FDB tendon to 5th toe in the present study was significantly higher when compared to many previous reports. Conclusion: Variations of FDB are clinically significant because FDB musculocutaneos flap is used in the reconstruction of the heel pad and FDB tendons are used in tendon transfer surgeries for claw or hammer toe deformities. The absence of FDB tendon to the 5th toe shows clustering around Asian region, which signifies possibility of occurrence of evolutionary changes in specific topographic region