Developmental
problems
During the period in which the foot is growing a variety of interrelated
problems can arise. These fall into two groups of significant problems but
represent a relatively small percentage of the total population. The vast
majority of children presenting to a surgeon will in fact be normal. The major
cause for presentation will be parental concern about perceived problems about
the shape of the foot or abnormal shoe wear. The two groups of disorder, foot
shape and function, are the conditions leading to a progressive planovalgus
(or flat) foot and those that lead to pes-cavus or a high arched foot. Some of
the toe conditions start to become symptomatic in the childhood years but only
in adolescence does the condition of hallux valgus appear as a significant
developmental abnormality.
Planovalgus
foot
The flat foot is normal providing that the longitudinal arch rises and
falls dynamically. In activities such as standing
The
flat foot becomes pathological when one of three things happens. First, anything
which stops movement in one of the joints of the hindfoot will simply prevent
the normal behaviour of this mechanism. The condition of tarsal coalition is
the most obvious example of this. This is where there is an abnormal join
(fibrous or bony) between two or more tarsal bones.
Second,
conditions which affect the integrity of the primary restraints of the various
joints involved will result in instability. This leads to the foot deforming
into a valgus heel position and into an abducted (and supinated) forefoot
position.
Conditions such as Marfan’s syndrome are examples of this form of problem.
Commoner is familial hypermobility, but only a few of these patients exhibit
pathological foot function.
Third,
imbalance between the secondary restraints can cause progressive deformity. The
best example of this is in neurological conditions such as cerebral palsy. Here
the spasm in the peroneal muscle groups overcomes the action of the inverters of
the foot. The hindfoot is gradually pulled into valgus. This in turn leads to
stretching of primary restraints. If the deforming force is un-resisted for long
enough, the effect is to produce bony deformity; this fixes the deformity.
Although this pattern of developing deformity can be applied to the adolescent
foot, it also underlies the pattern of development of a progressive planovalgus
foot in any age group. In the elderly rupture of the tibialis posterior tendon
will cause imbalance of the secondary restraints.
Treatment
Primary
treatment should always be conservative in nature. In the foot with increased
mobility the use of orthoses will control the foot position while a shoe is
worn. This diminishes the pressure on the foot created by the shoe; thus the
symptoms due to pressure effects are reduced. The shoe itself is less likely to
deform and produce abnormal wear contributing to the pressure on the foot. There
is no evidence that such devices influence the long-term outcome for the foot.
Corrective orthoses in conditions where the deformity is fixed, as in a
coalition, do not work. In these circumstances orthoses should be used to
increase the cushioning available in the foot. This can reduce symptoms by
reducing the forces passing through the foot. Rest and modification of activity
can have a profound effect on the symptoms that the patient experiences. This
can mean that despite the rigidity of the foot the patient is pain free and has
reasonable function. If the joints involved are irritable and painful an
injection of a local anaesthetic agent with an intraarticular steroid
injection can reduce symptoms until the child is older.
In
the neurological conditions such as cerebral palsy, physiotherapy including
stretching exercises has a role to play. This allows the imbalance to be
corrected passively. The use of ankle foot orthoses to maintain the position of
the foot is helpful (Fig. 31.3). If the increased tone in the peroneal and calf
muscles is a particular problem then botulinum toxin injections into the muscle
bellies can be useful. The effect wears off within days but during the period of
reduced spasm the benefit of surgical treatment can be assessed in the knowledge
that the paralysis will wear off in the fullness of time. During the period when
the toxin is active physiotherapy may overcome the deformity further providing a
longer-term benefit.
The
principle of surgical treatment is first to balance the forces acting on the
foot to remove the deforming forces; second, to correct any deformity that has
already developed; third, to stabilise the foot in order to prevent deformity
from recurring.
• Correcting bony deformity. This can be achieved by lengthening
the lateral border of the foot using a modified distraction osteotomy originally
described by Dillwyn Evans (Fig. 31.4) or by an osteotomy of the os calcis
designed to transfer the contact point of the calcaneum medially.
• Balancing the secondary restraints. This may involve tightening
of the inverters of the foot. This may include formal reconstruction of the
tibialis posterior tendon.
• Reconstructing the primary medial restraints such as the
talonavicular joint capsule.
Pes
cavus
The mechanism of the generation of the deformity of the high arch foot
is less easy to understand. This is partly because a number of conditions leads
to similar although not identical deformity. The common feature of the condition
is some element of neurological dysfunction. This leads to the problem of muscle
imbalance. The intrinsic muscles are weak leading to a mismatch between the
intrinsic and extrinsic muscle power. With equinus deformity the Achilles tendon
is tight. This is not an invariable feature of pes cavus and in conditions where
the calf muscles are weak there is a calcaneus deformity. In addition there is
a group of patients who have a relatively higher inverter power than everter
power. This will lead to the foot rotating so that the lateral border is mainly
in contact with the floor.
The
clinical presentation of patients with pes cavus most commonly occurs in late
childhood or early adolescence when the presence of the deformity becomes more
obvious. The deformity is obviously influenced by growth but can progress
after growth has ceased. Symptoms which are usually present are increased
pressure on the forefoot due to clawing of the toes and equinus, pain on the
lateral border of the foot due to a varus heel position and finally feelings of
Because
of the variations in specific aetiology, and the progression and nature of the
deformity, various management options need to be considered. The use of
conservative treatment is important and largely revolves round the use of
Although
this guide gives a concept of the procedures that have to be considered when
treating the cavus foot, there is a great variation in the pattern of deformity
with different aetiologies. The deformity can progress throughout life. This
again has to be taken into account in planning the management of each individual
case (Fig 31.5).