The Z-Shaped Elongating and Varisizing Osteotomy (ZEVO) Calcaneal Osteotomy for Pes Plano Abducto Valgus

Indications

Alternative to double osteotomy in acquired flatfoot deformity (AFFD)
When a combination of lengthening of anterior process and medial shift of tuber is indicated (usually in case of dorsolateral peritalar subluxation on weight-bearing radiographs)
When deformity is still reducible/flexible

Indications Pearls

Indications Pitfalls

In a nonflexible foot this is not an appropriate procedure; for example, a late case with degenerate joints or possibly a combination with a fixed deformity like a coalition.
Concomitant problems such as diabetes mellitus or poor vascular supply are risk factors that should be assessed.
On the medial side of calcaneus there are several important structures. It is thus important not to overpenetrate with instruments or implants on the medial side.

Indications Controversies

This procedure has now been in clinical use for 20 years. It is a variant of other procedures: the lateral column lengthening osteotomy described by Hintermann et al. (1999) and the Koutsogiannis sliding tuber osteotomy in combination.
As such this procedure is part of a pes plano abductovalgus (PPAV) reconstruction and is rarely, if ever, intended to be used alone.

There is a hindfoot flatfoot valgus deformity, possibly with abduction in midfoot
On toe raising there is no inversion of the heel
Often there are clinical signs of midfoot instability and contracted gastrocnemius
Radiographic signs of flatfoot with dorsolateral peritalar subluxation on standing weight-bearing plain films
No signs of secondary arthrosis in subtalar joints
Inversion at the Chopart joint level is close to normal (foot is reducible)
Often radiographic signs of tarsal instability on weight-bearing films

Treatment Options

A joint-preserving procedure with calcaneal osteotomy (sliding tuber or distal calcaneal/lateral column or double osteotomy [both]) together with medial tendon replacement transfer (flexor digitorum longus), and reefing of spring and deltoid ligaments, and possibly gastrocnemius release and midfoot stabilization (Lapidus or naviculocuneiform fusion)
A triple or more often a double fusion incorporating the subtalar and talonavicular joints and necessary soft-tissue balancing around this region

The calcaneus articulates the talus with the posterior subtalar joint and the anterior subtalar joint. It also articulates the cuboid in the calcaneo-cuboid joint. Between the posterior and anterior subtalar joints is the canalis tarsi, which laterally opens into the sinus tarsi, just distal to the lateral malleolus.
As flatfoot deformity develops, no matter the exact pathology, a dorsolateral peritalar subluxation develops.
The coxa pedis is the center of this biomechanical development.
The coxa pedis consists of the navicular joint, the anterior subtalar joints of calcaneus, and the spring ligament, which is the strong ligament between these. The latter might be torn in the case of an AFFD.
An anatomic specimen showing calcaneus’s joints from above, after the talus is removed, is presented in Fig. 32.1 .

By altering the shape and the forces around the coxa pedis, it has been shown that a correction or realignment of the AFFD is achieved.
By lengthening of the distal calcaneus (part of calcaneus from the canalis tarsi to the calcaneocuboid joint [CC-Joint]), a rotational moment is achieved in the coxa pedis that aligns the talar head into the talonavicular joint.
By the medialization acquired by the osteotomy, a medialization of the insertion of the Achilles tendon and plantar fascia is acquired and thus alignment correction occurs.
Fig. 32.2 shows a diagram of Z-shaped elongating and varisating osteotomy (ZEVO).

For this part of the procedure, patients are always positioned sideways with their foot on a pillow ( Fig. 32.3 ).
Under general anesthesia and with a tourniquet in place the skin is marked ( Fig. 32.4 ).

Positioning Pearls

If positioned sideways on a pillow that is stable and flat, it is easier to assess the amount of correction needed and gained to make a correct alignment of the hindfoot.
With training this can be done supine, which would facilitate the whole reconstruction.

Positioning Pitfalls

It is more difficult to see the axis of the altered calcaneus and to insert the implants in its new axis if the patient is supine.
Thus there seems to be a higher risk of medial penetration with implants.
When the osteotomy is finished, the patient is turned supine, which needs to be considered before draping is carried out.

Positioning Equipment

If positioned sideways, a pillow is recommended together with holding brackets at the back and front of the patient.
These are all removed when patient is turned supine.

Positioning Controversies

Repositioning of the patient during surgery might be considered bothersome, and in very heavy patients several people are needed to achieve a good position.

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