Surgical Anatomy of the Medial Cuneiform (Cotton) Osteotomy.

Background: The Cotton osteotomy, or dorsal-opening wedge osteotomy of the medial cuneiform (MC), is used to address medial column alignment to restore the static-triangle of support. There are many described techniques regarding the incision and osteotomy. Successful completion of the osteotomy requires knowledge of the anatomy, particularly the location of the medial dorsal cutaneous nerve (MDCN). This study describes the relationship between MDCN, tibialis anterior, extensor-hallucis-longus tendon, and ligamentous attachments to the MC. A technique to determine a safe location for the osteotomy is also described.

Methods: Twelve fresh-frozen adult foot specimens were used for this study (7 male and 5 female). The MDCN and its branches were dissected and its relationship with the MC was documented. Osteotomy tilt angle and relationship to structures around the MC were measured.

Results: MDCN traveled medially and distally over the dorsum of the MC, and a small branch to the MC was observed. The tilt angle was 80.1 ±1.4 degrees. There was no significant difference between the distance from the distal-articular surface to the midline of the cuneiform and to the interosseous ligament ( = .69), or between the distance from the distal-articular surface to the second tarsometatarsal joint and to the origin of the Lisfranc ligament ( = .12).

Conclusions: The dorsal-medial-oblique incision effectively protected MDCN and the MC. We believe the osteotomy should be performed in the safe zone to maintain the stability of the opening wedge.

Clinical Relevance: The dorsal-medial-oblique incision could reduce the risk of injury to the MDCN and the tibialis-anterior tendon.