biomechanics

Background

Bunion

- medial prominence of head of 1st MT

Hallux Valgus

- medial deviation 1st MT

- lateral deviation of great toe

Metatarsal head

- has 2 grooves separating ridge (cristae)

Able to achieve relatively high level of function after STJ fusion

- previously believed that isolated STJ fusion should not be performed

- believed that triple arthrodesis was operation of choice for hindfoot

- STJ fusion has superior result with less stress on AJ

Average loss of DF 30% / PF 10%

Position of hindfoot determines flexibility of transverse tarsal (CCJ & TNJ) joints

- imperative that fusion be positioned in ~ 5^o valgus

- 90% load through plafond to talus

- 10% load through lateral talofibular articulation

A. Lateral Ligament Complex

ATFL (Anterior Talo-Fibular Ligament)

- tight in plantar flexion