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Chapter 66 Supramalleolar Osteotomy with Internal Fixation: Perspective 2

T E C H N I Q U E S

■ Lateral Closing Wedge Osteotomy to Correct Valgus Exposure ■ After exsanguination of the leg, a pneumatic tourniquet is in- flated on the thigh. ■ A 10-cm longitudinal, slightly curved incision is made along the anterior margin of the distal fibula. If the incision needs to be extended distally, it is curved ventrally to end just distal to and anterior of the lateral malleolus ( TECH FIG 1 ). ■ The fibula and the tibia are then exposed laterally. To avoid de- vascularization of the bone, stripping of the periosteum is not performed. ■ At the distal end of the incision, the anterior syndesmosis is exposed. ■ The lateral branch of the sural nerve and the short saphenous vein run dorsal to the line of incision and are usually not seen during this procedure. However, extended proximal dissec- tion may require identification, exposure, and protection of the branches of the superficial peroneal nerve. Cauterization of some of the branches of the peroneal artery, which lie deep to the medial surface of the distal fibula, may be necessary. Fibular Osteotomy ■ In most cases in which a varus deformity is addressed with a lat- eral closing wedge osteotomy, the fibula needs to be shortened to preserve the congruency in the ankle joint. The shortening can be done by simple bone block removal or a Z-shaped os- teotomy. Alternatively, an oblique osteotomy (distal anterior to proximal posterior) can be used, although the Z-shaped fibular osteotomy confers greater control of rotation and primary stabil- ity compared to a block resection for fibular shortening. ■ The length of the Z-shaped fibular osteotomy is approximately 2 to 3 cm, starting distally at the level of the anterior syndesmosis. ■ Kirschner wires (K-wires) can be placed as a reference at the level of the transverse cuts to confirm the location of the oste- otomy fluoroscopically. ■ The osteotomy is then carried out with an oscillating saw. ■ After the fibula has been mobilized, bone blocks are resected on both ends of the Z based on the amount of the planned shortening ( TECH FIG 2 ).

■ To avoid interference from the dense syndesmotic ligaments when performing the Z-osteotomy, we routinely direct the proxi- mal transverse cut anteriorly and the distal cut (which typically sits at the syndesmosis) posteriorly. Lateral Closing Wedge Tibial Osteotomy ■ To define the desired osteotomy, two K-wires are drilled through the tibia, with the tips converging at the medial cortex, making sure that the angle between the K-wires corresponds with the preoperative planning (see TECH FIG 2 ). ■ Unless the deformity is located proximal to the supramal- leolar area, the wires are directed from proximal to the anterior syndesmosis to the medial physeal scar ( TECH FIG 3A ). ■ After fluoroscopic verification of the location of the wires ( TECH FIG 3B ), the periosteum is incised only at the level of the planned osteotomy and carefully mobilized with a scalpel or periosteal elevator. ■ The osteotomy is then performed using an oscillating saw cooled with saline or water irrigation to limit thermal injury to bone. ■ Placing the K-wires accurately avoids cutting through the medial cortex; ideally, the medial cortex should serve as a hinge. ■ Correction of the deformity must be performed at the CORA of the deformity to avoid relative translational malpositioning of the distal (ankle) and proximal (tibial shaft) fragments. ■ The gap is then closed and the osteotomy is secured with a plate. We prefer locking plates that afford optimal primary stability; however, it is imperative that the osteotomy is com- pletely closed when employing locking plate technology ( TECH FIG 3C,D ).

TECH FIG 2 ● Drawing illustrating the Z-shaped osteotomy to shorten the fibula.

TECH FIG 1 ● Lateral approach to the distal fibula and tibia.