Ankle & hindfoot: a free FRCS (Tr & Orth) Section 1 question

The accepted position for ankle arthrodesis is neutral in the sagittal plane, about 5° of hindfoot valgus and 5–10° of external rotation matching the other side, with the talus translated slightly posteriorly under the tibia to shorten the lever arm of the foot and ease roll-over. Equinus produces a vaulting gait, a recurvatum thrust at the knee and midfoot overload. Varus locks the transverse tarsal joint, giving a rigid foot that bears weight on its lateral border. Internal rotation is poorly tolerated because the foot trips the swing leg, and excessive external rotation strains the knee and medial foot. Anterior translation lengthens the lever arm. Fixed dorsiflexion overloads the heel. Reference: Buck P, Morrey BF, Chao EY, J Bone Joint Surg Am 1987; Miller's Review of Orthopaedics 8e.