In a patient with hallux valgus, the lateral displacement of the sesamoids seen on a weight-bearing radiograph occurs primarily because of which anatomical change?
- A The first metatarsal head displaces medially away from the sesamoids, which remain held by the deep transverse metatarsal ligament ✓
- B Erosion of the tibial sesamoid by the first metatarsal head
- C Rupture of the medial collateral ligament of the first MTP joint
- D Atrophy of the abductor hallucis muscle
Correct answer: A. The first metatarsal head displaces medially away from the sesamoids, which remain held by the deep transverse metatarsal ligament
Explanation
The sesamoids are anchored to the second metatarsal base through the adductor hallucis tendon and the deep transverse metatarsal ligament, so they do not truly sublux laterally. As the first metatarsal drifts into varus, the head moves medially relative to the fixed sesamoid complex, creating the appearance of lateral sesamoid displacement. The ligaments themselves remain intact, which rules out options B and C.
Reference: Campbell's Operative Orthopaedics, 14th ed.
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Written and medically reviewed by the StethoPrep medical team.