Extraperiosteal Plating of Pronation-Abduction Ankle Fractures

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137 T HE JOURNAL OF BONE & JOINT SURGERY · SURGICAL TECHNIQUES MARCH 2008 · VOLUME 90-A · SUPPLEMENT 2, PART 1 · JBJS.ORG placed medial malleolar fragment 2 . Thus, an anatomic reduction of a supracollicular medial malleolar fracture restores medial support, gains talar congruence, and assists with reduction of the lateral malleolus 2,3 (Fig. 2-A). The incision used on the medial side is slightly concave anteriorly and is centered over the medial malleolus, as this allows both visualization of the reduction and placement of the screws (Fig. 2-B). Bicortical lagscrew fixation, perpendicular to the fracture line, is preferred to increase the stability of the fixation and to compress across the fracture site (Fig. 3). Attention is then turned to the lateral side. The ankle should be positioned with bolsters under the ankle joint and not under the heel. Bolsters under the heel can cause anterior subluxation of the talus and a malreduction. The foot is adducted and medially translated to center the talus in the mortise, which aids in fibular alignment. Because the lateral ankle ligaments are intact in this injury pattern, reducing the talus under the plafond usually aligns the distal fibular fragment and restores fibular length. Fluoroscopic imaging at this point allows an assessment of fibular length. The lateral cortex of the fibula is comminuted, but the medial cortex typically starts as a transverse fracture line, so one can evaluate the reduction at this location to assess length (Fig. 4). Finally the talocrural angle on the affected side is compared with the contralateral, normal ankle to confirm fibular length 4 . As the talocrural angle is not related to the size of an image, fluoroscopic evaluation is not affected by magnification, as are other measures of fibular length. After determining the necessary manipulation of the foot that recreates fibular length, one can proceed. (For additional techniques to gain fibular length, see separate section below.) Once the general reduction of the fibula can be obtained, the incision is made. The incision is centered over the posterior onehalf of the fibula. When the incision has been made through the skin, care is taken not to incise the periosteum. It is found immediately subcutaneously and often has small rents in it as part of the injury, which can make it difficult to recognize. Sharp Weitlaner retractors can aid by applying tension to the skin, helping to peel the subcutaneous tissues from the periosteum. The periosteum is left entirely intact; individual fracture fragments are not identified, stripped, or further handled. Once the dissection is at the level of the periosteum (Fig. 5), all retractors are removed from the wound as they can shorten the fibula because of the tension placed on the surrounding soft tissues. Reduction is obtained by manipulating the foot, and then a lateral fluoroscopic image is made to confirm that there is no angulation or translation of the fibula. This is the last time that an unobstructed lateral radiograph can be made so it is imper- ative that any sagittal plane displacement of the fibula is corrected now. Once this is completed, the anteroposterior radiograph is made again to confirm the coronal plane reduction. Residual lateral translation or angulation is often seen; this is normal and is corrected later with the undercontoured plate. Next, a precontoured direct lateral fibular plate, or a straight one-third tubular smallfragment plate that the surgeon contours to the shape of the distal aspect of the fibula, is placed into the wound. It is vital that the plate be slightly undercontoured in relation to the lateral surface of the fibula as this ultimately corrects the lateral translation of the fibula. The plate is placed onto the fibula, with the surgeon ensuring that it is centered between the anterior and posterior borders of the bone. This is done initially by feel as one cannot strip the soft tissue from the fibula to visualize the bone directly, but a Kirschner wire can be used as a probe to assist in identifying the anterior and posterior borders of the fibula. Fluoroscopic lateral imaging is required to confirm that the plate is centered on the bone before fixation is placed (Fig. 6-A). This is paramount for the reduction as the direction of the force provided by the plate must be directly medially to reduce the laterally translated fibula. Additionally, the fibula must be evaluated for angulation. Any anterior or posterior angulation must be corrected prior to fixation by
138 T HE JOURNAL OF BONE & JOINT SURGERY · SURGICAL TECHNIQUES MARCH 2008 · VOLUME 90-A · SUPPLEMENT 2, PART 1 · JBJS.ORG FIG. 2-A The medial malleolus is composed of the anterior and posterior colliculi. A supracollicular fracture (left) extends from the anterior tibial cortex to the posterior tibial cortex; an anterior collicular fracture (right) exits inferiorly between the colliculi, creating an anterior fracture fragment. The broad superficial deltoid ligament, which is the weaker of the two portions of the ligament, takes its origin from the anterior colliculus and acts to prevent external rotation of the ankle when the foot is in plantar flexion. The stronger deep deltoid ligament originates from the posterior colliculus and the intercollicular groove, and prevents external rotation of the ankle with the foot in dorsiflexion. Fixation of a supracollicular medial malleolar fracture, with the deltoid ligament (most importantly, the deep portion) intact on it, restores medial stability 3 . The incision is concave anteriorly, which allows visualization of the joint and placement of lag screws perpendicular to the fracture. moving the bolster to an appropriate position. Once appropriate plate position is confirmed, the plate is provisionally fixed to the bone with Kirschner wires or provisional fixation pins (Fig. 6- B). After temporary fixation, the centered location of the plate on the fibula is again confirmed. Screws can then be placed, from proximal to distal, which will push the fibula (and therefore the talus) medially, under the plafond (Figs. 7-A and 7-B). The reduction is confirmed on the anteroposterior radiograph. If the talus does not reduce, one of two problems exists. Either the syndesmosis is unreduced or the plate is incorrectly contoured to effect a reduction and the fibula
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Extraperiosteal Plating of Pronation-Abduction Ankle Fractures

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