Bilateral Anatomical Variation of the Extensor Hallucis Longus: Dual Attachments to the Hallux

Introduction:

The extensor hallucis longus (EHL) is a crucial muscle in the lower limb, responsible for the extension of the hallux and dorsiflexion of the ankle. While anatomical variation of the EHL has been documented, the extensor hallucis longus muscle typically has a single attachment on the dorsal aspect of the base of the distal phalanx of the hallux. Variations in its attachment sites can provide clinical significance for reconstructive procedures.

Methods:

Medical students at Philadelphia College of Osteopathic Medicine (PCOM) in South Georgia conducted a cadaveric dissection on a 69-year-old male. During a routine cadaver dissection, a bilateral observation was made regarding the lower limb of a cadaver. A detailed examination was performed to assess the muscle structure, attachment sites, and any variation present.

Results:

The extensor hallucis longus muscle was found to have two distinct attachments on the anterior surface of the hallux, observed bilaterally. The belly of the extensor hallucis longus bifurcates before extending toward the attachment sites. The primary attachment followed the common arrangement, inserting on the dorsal aspect of the base of the distal phalanx of the hallux. However, an additional attachment was identified, anchoring onto the medial aspect of the hallux.

Conclusion:

There were no signs of surgical procedures performed to the muscle indicating a congenital anomaly. The presence of the dual attachments may influence the functional strength of the extensor hallucis longus. The dual attachments of the extensor hallucis longus may influence the stability and control of the movement of the great toe. However, this variation could create an imbalance by altering the muscle’s line of pull, potentially reducing strength. The dual attachment may also impact biomechanics, such as walking and running. An increase in strength and stability could be advantageous, whereas any inefficiencies may require compensatory movement from other muscles.