the tendons, Achillis and peronei, may require to be lengthened. If
the ankle is unstable as a result of the absence of the lateral
malleolus, it may be artificially ankylosed, or the lower end of the
tibia may be split vertically so as to make a socket for the talus. In
either case, the foot is placed in the equinus attitude to compensate
for the shortening of the leg. Deficiency of the tibia is frequently
associated with imperfect development of the great toe; deficiency of
the fibula with absence of the lateral toes and their metatarsal
bones.

_Volkmann's Supra-malleolar Deformity._--This condition, which is
closely allied to that just described, consists in a congenital
deficiency in the development of the bones of the leg, and especially
of the fibula, as a result of which the articular surface is oblique
and the foot deviates to one or other side. The foot usually occupies
a valgus position, the sole looking laterally, and only its medial
border coming into contact with the ground. It is treated by
supra-malleolar osteotomy.

THE FOOT

Various deformities are met with in the region of the ankle and
tarsus. The term "talipes" is commonly used to include all these, but
here it will be restricted to that form in which the heel is more or
less elevated, and the foot supinated so that it rests on its lateral
border--_talipes equino-varus_. In _pes equinus_ the foot is in the
position of plantar-flexion, and the patient walks on the toes. In
_pes calcaneus_ the foot is dorsiflexed so that the tip of the heel
comes in contact with the ground; this deformity may be combined with
eversion of the foot, _pes calcaneo-valgus_, or with inversion, _pes
calcaneo-varus_. When the instep is unduly arched, the terms _pes
cavus_, _pes arcuatus_ or _hollow claw-foot_ are employed; while loss
of the arch constitutes _flat-foot_, and eversion of the sole, _pes
valgus_.

CLUB-FOOT

#Talipes Equino-varus.#--This deformity may be congenital or
acquired.

#Congenital talipes equino-varus# (Fig. 142) is a common malformation
which is sometimes associated with other deformities, such as hare-lip
or spina bifida, and may be met with in several members of one family.
It is nearly twice as common in boys as in girls, and is slightly more
frequently bilateral than unilateral. Its etiology is obscure, and
various hypotheses have been put forward to account for it, but no one
is convincing. It may be pointed out, however, that the fo