p2.ch3.4
3. Equinovarus Deformity
Varus deformity is frequently observed in hemiplegic foot,
occasionally in diplegic foot, and in a form of windswept deformity
as well.
Problem of the equinovarus deformity is that weight of the
body is displaced and focused only on the lateral side of the sole
and so effective weight bearing on the sole is not possible. In most
of the feet, callosity is formed on the head of the fifth metatarsal
bone but in severe deformity also on its base of the fifth metatarsus
in severe deformity, accompanied by adduction deformity of the
foot. Occasionally fifth metatarsal bone has a fracture, due to
concentration of stress at the weight-bearing region. Treatment is
varied from muscle release surgery to bony surgery, according to
age, extent and type of deformity, such as dynamic one, fixed one
with ligamentous and capsular contractures, or fixed one with bony
changes.
Historical Reviews
Various approaches have been advocated for correction.
For correction of dynamic deformity due to muscle
imbalance, Z or sliding lengthening of the tibialis posterior has
been recommended.252,253 Certainly, Z or sliding lengthening is an
effective technique for correction. Many orthopaedic surgeons have
used this method for correction.67 However, overcorrection due to
postoperative weakness of the tibialis posterior often presents
serious loss of stability in the form of valgus deformity, since this
muscle also has antigravity activity. We have not used sliding l
engthening alone as a single procedure, to avoid this
overcorrection.
In order to prevent postoperative reverse deformity, many
authors have made maximum efforts. Intramuscular lengthening of
the tibialis posterior is a recommended procedure. In 1971, Ruda
and Frost proposed a technique of intramuscular lengthening of the
tibialis posterior.254 He reported only 2 feet with recurrence of the
29 treated feet and recommended this procedure for the feet of
younger children, since overcorrection was prevented. In this
procedure, the muscular part with short tendon is preserved, while
the muscular part with long tendon is selectively released, with
reduction of hypertonicity. So by intramuscular lengthening of the
tibialis posterior, we can expect the possibility of preserving the
supporting activities while reducing hypertonicity. However, this
procedure has some limitation in correction of severe deformity
since some of the remaining portion of the muscle fibers can still
be hypertonic and be a cause for recurrence. Hence another
extensive approach should be considered for correction of severe
deformity.
Tenotomy of the tibialis posterior has not been
recommended, because of occurrence of reverse deformity.
Postoperative loss of the medial longitudinal arch has been well
documented.255-257
Anterior transfer of the tibialis posterior through the
interosseous membrane has also been presented.258-262 However,
reverse valgus deformity combined with collapse of the medial
longitudinal arch is often observed and the final result is miserable.
Root and associates recommended posterior tibial transfer with
successful results in 72% of the feet operated. However, he also
presented 16 patients (28 %) with poor results. Thus, effects of this
procedure are unreliable.263 This procedure may be applied only in
cases with fixed equino varus deformity.
Anterior translocation of the tibialis posterior from its
original insertion to the anterior over the medial malleolus was also
reported by Baker and Hills.232 Bisla and associates stated that in
this procedure, little or no improvement occurred.260 Partial
transfer of the tibialis posterior is an another procedure, which
decreases the deforming force. Green and associates in 1983
advocated partial transfer of the tibialis posterior to the peroneus
brevis tendon.264 After follow up for a minimum of two years, they
described that there was no recurrence of the varus, nor was any
valgus or calcaneus deformity seen. Kling and associates in 1985
reported good results with a similar procedure.265 Green
emphasized that this can be evaluated as a safe procedure, since
the power of plantar flexion is not weakened because of partially
preserving the tibialis posterior. We can understand the advantage
of this procedure in which the important antigravity activities of
this invertor can be preserved, while at the same time sufficient
correction is obtained. However, I wonder if the remaining
hypertonicity of the tibialis posterior and hypertonicity of the
transferred tendon of the tibialis posterior to the peroneus brevis
can be evenly controlled in a well-balanced way. It is also
interesting, if the transferred tibialis posterior muscle with
inverting plantar flexion activities can act alternately as an everting
dorsiflexor, while the remaining tibialis posterior muscle can act as
an inverting plantar flexor in the same foot, in different stance and
swing phases.
In controlling equinovarus deformity, we use selective
release surgery, by combining sliding and intramuscular
lengthening of the tibialis posterior, sliding lengthening of the
flexor digitorum longus, intramuscular release of the flexor
digitorum brevis, and intramuscular and sliding lengthening of the
triceps surae. Medial release of the midtarsal capsule and bony
surgery are also combined.To ContentsBackNext
Surgical Approaches
Considerations:
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A. Before OSSCS
B. After OSSCS
Fig. 120AB: Effect of evans operation combined with OSSCS
Fig. 121: Effect of pantalar arthrodesis
for fixed equinovarus deformity
Underconstruction
Surgical Techniques:
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