Wedge Tarsectomy & dorsi-flexing Lapidus

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There are various disparate causes of a Cavo-varus foot deformity all of which result in varying degrees of characteristic deformity secondary to imbalanced muscular action.
The objective of all treatment , operative and non-operative, is to place (and hold) a balanced foot squarely beneath the Tibia. Surgical management in particular is often referred to as “A La Carte” , alluding to the very specific nature of individual interventions for individual components of the deformity.
The indication for a Wedge tarsectomy is for correction of a comprehensive midfoot cavus. It is also possible to correct an element of adductus by excising an asymmetric tarsal wedge. If the excised tarsal wedge is truncated in its plantar aspect (in other words a wide based rather than sharp apex is cut) then secondary tightening of the plantar fascia is less likely to occur on closure of the wedge.

There are various disparate causes of a Cavo-varus ( or Equino-cavo-varus) foot deformity all of which result in varying degrees of characteristic deformity secondary to imbalanced muscular action.
The Cavus foot can be classified according to the level of the pathology causing the problem. Central neurological causes include CVA, Cerebral Palsy, and MS , spinal located causes include polio and spinal cord injury ,peripheral nerve lesions an be due to HSMN or Leprosy and most distally amongst the muscle pathologies to be considered are muscular dystrophy and the sequelae of a compartment syndrome.
The objective of all treatment is to place (and hold) a balanced foot squarely beneath the Tibia .Whilst a deformity remains flexible this can be done with orthotic management or if required operatively by means of tendon transfers and osteotomies. Once fixed however fusion surgery is likely to be required required though there remains a role for osteotomies to be combined.
The various elements of the deformity should be identified and both their level and nature must be documented. A careful assessment of the opposing neuromuscular units is always required .How to proceed surgically depends upon the level , extent of deformity and flexibility the balance of power of the agonist/antagonist muscle groups , their absolute strength(judged by the MRC scale) and also the passive correctibility of components of the deformity.
On the MRC grading scale no muscular contraction is graded as 0 , contraction but no movement as 1, active movement that cannot overcome gravity 2, active movement that can overcome gravity 3 ,active movement against gravity and resistance 4, normal muscle muscle strength 5. It should be remembered that in transferring a muscle to a different position and function it is expected that its MRC grading will fall by 1 or 2 points on the MRC scale , which makes transferring an MRC 1 or 2 power muscle of dubious value.
How to deal comprehensively with the Cavo-varus foot is beyond the scope of this section but its surgical management in particular is often referred to as “A La Carte” , alluding to the vary specific nature of individual interventions for individual components of the deformity.
A contracted Achilles may require lengthening . In the younger patient a global mid/forefoot equinus may respond to a Steindler plantar fascia release. In the adult with a stiffer deformity and comprehensive Midfoot cavus this is an indication for a wedge tarsectomy. An isolated plantar flexed 1st ray should also be looked for which may require correction by 1st Ray dorsiflexion osteotomy. This deformity in isolation can drive/produce a compensatory Calcaneal varus in order to allow the foot a degree of stability as a weight-bearing platform. This relationship between the hindfoot and forefoot should be explored with the Coleman block test. By removing the first ray from ground contact this reveals whether the hindfoot deformity is flexible and secondary to the 1st ray position. If it is the heel will correct to neutral and surgery to the 1st ray will deal with the hindfoot deformity. If the hindfoot stays in varus it may need discreet surgical correction, by means of a lateralising Calcaneal osteotomy.
Weakness of dorsiflexion with a relatively powerful Peroneus longus and poor Tibialis anterior may benefit from transferring Peroneus Longus to the Brevis. If on the other hand the Tibilais posterior is overpowering a weak Peroneus Brevis and Tibialis anterior it should be considered for transfer.
Most patients will present to the Surgeon already with a diagnosis and having been diagnostically worked up. If this is not the case then a complete neurological examination (including recording of power , reflexes and the presence of spasticity in upper and lower limbs) needs to be performed. The opinion of a neurologist should also be sought.

GA or regional anaesthesia
Femoral & sciatic blocks for post-operative pain relief
Laminar flow , peri-operative antibiotics , 2-4 weeks of post operative LMW Heparin
Thigh tourniquet and Flowtron on contra-lateral calf
Ankle positioned into neutral using sandbags & side supports
Large , rolled up sterile towels behind the ankle to improve access for cuts.
Kit required : Large single sided reciprocating saw blade, large power unit, large round nosed periosteal elevator, Hibs osteotomes.

2 weeks in back-slab , dressing changes at 1 & 2 weeks
Complete cast between weeks 2 to 6 & non-weight bear
Check X-ray at 6 week stage .
Patient depending into long post-operative boot and gradual increase in weight-bearing at this stage.For poorer bone quality patients or possible compliance issues continue in a walking cast until 12 weeks.
Add an “off the shelf” supportive , semi-rigid 3/4 length orthotic to be used once in post-operative boot and until return is made to normal shoe wear.
May be comfortable enough to make transition into stiff soled walking boot by 12 weeks.
Remain in this for all weight bearing for a further 6 weeks whilst using the orthotic.