Anatomical considerations for minimally invasive osteotomy of the fifth metatarsal for bunionette correction - A pilot study.

Introduction: Operative correction of symptomatic bunionette by means of minimally invasive (MI) osteotomies of the 5th metatarsal (M5) has gained popularity. This study aims to investigate the safe zones of commonly used techniques and the risk of injury to neurological structures.

Materials And Methods: Ten human fresh frozen cadaveric feet were dissected and branches of the sural nerve were identified. A frontal section of the feet was performed at the site of the skin incision described for M5 MI osteotomies (corresponding to distal and mid diaphyseal osteotomies). The location of the lateral dorsal cutaneous nerve (LDCN) of the sural nerve or its branches was documented using a goniometer and o'clock references placed on the frontal section of the M5.

Results: The LDCN showed variations in the distribution of its branches, forming the dorsolateral branch - a single terminal branch for the 5th toe - in 6/10 cases or two terminal branches - the dorsolateral and dorsomedial - in 4/10. At the point of osteotomies, the dorsolateral branch was identified at a mean of 22.7° from the extensor tendon around the M5 circumference and in all cases between 12 and 2 o'clock in a right foot or 10 o'clock to 12 o'clock in a left.

Conclusion: The studied M5 osteotomies can place the dorsolateral branch of the fifth toe at risk and safe zones lie between 10 o'clock to 2 o'clock in any foot laterality. If these landmarks are considered, the risk of nerve damage is minimized when performing MI osteotomies of the M5.