Abstract
The premise for reconstruction of a malunited ankle fracture is joint preservation. Frequently, the joint may appear to be irreparable, with articular wear and erosive changes on the medial or lateral plafond. Even with these more advanced changes, however, restoring the alignment of the ankle is worthwhile. Most of these cases involve a malunion or a nonunion, or both, of the fibula. Occasionally, the medial malleolus or the posterior tibia also is involved in this malunited fracture, necessitating simultaneous correction. Lateral weight-bearing radiographs and a computed tomography (CT) scan of the ankle are helpful to plan the reconstruction. The CT scan does aid in determining the required degree of rotation of the fibula, syndesmotic malalignment, posterior malleolar involvement, and presence of articular impaction. It is always worth the effort to attempt a reconstruction of the malunited ankle fracture, except in the case of severe ankle arthrosis. If this fails, an arthrodesis and joint replacement are still options. The results with osteotomy of the fibula or the tibia, or both, are excellent even in ankles with considerable deformity and arthritis. In some situations, a reconstruction simply cannot be performed for technical reasons, and an arthrodesis is the best alternative. An important point in this context, however, is that an arthrodesis is not the only treatment option after severe trauma.
Key Words
malunion, revision, osteotomy, ankle fracture, fibula, tibia, syndesmosis, malleolar
Decision Making and Reconstruction
The premise for reconstruction of a malunited ankle fracture is joint preservation. Frequently, the joint may appear to be irreparable, with articular wear and erosive changes on the medial or lateral plafond. Even with these more advanced changes, however, restoring the alignment of the ankle is worthwhile. Most of these cases involve a malunion or a nonunion, or both, of the fibula. Occasionally, the medial malleolus or the posterior tibia is also involved in this malunited fracture, necessitating simultaneous correction. Lateral weight-bearing radiographs and a computed tomography (CT) scan of the ankle are helpful to plan the reconstruction. The CT scan does aid in determining the degree of malrotation of the fibula, syndesmotic malalignment, posterior malleolar involvement, and presence of articular impaction. It is always worth the effort to attempt a reconstruction of the malunited ankle fracture, except in the case of severe ankle arthrosis. If this fails, an arthrodesis and joint replacement are still options. The results with osteotomy of the fibula or the tibia, or both, are excellent even in ankles with considerable deformity and arthritis ( Figs. 17.1 and 17.2 ). In some situations, a reconstruction simply cannot be performed for technical reasons, and an arthrodesis is the best alternative. An important point in this context, however, is that an arthrodesis is not the only treatment option after severe trauma ( Fig. 17.3 ).
Debridement: Arthroscopy or Arthrotomy?
A decision needs to be made whether arthroscopic debridement of the joint is to be performed simultaneously. Arthroscopic evaluation of the joint is very helpful in these cases to document and stage the extent of ankle arthritis. In particular, arthroscopy is indicated for evaluation of a suspected posterior and inaccessible chondral defect that would not be visible with anterolateral arthrotomy. The hypertrophic tissue between the medial malleolus and the talus must be excised from the medial gutter for the reposition of the talus. Surprisingly small amounts of tissue in the medial gutter can actually block the correct medial shift of the talus back into the mortise ( Fig. 17.4 ). Fibular malunion is generally associated with a lateral translational deformity of the talus with an increase in the medial clear space, and the medial joint recess must be debrided, under visualization afforded by either arthrotomy or arthroscopy. In our opinion, if revision is to be attempted, the joint should be debrided in all cases, specifically the medial aspect of the joint to imbricate the deltoid ligament (in cases without medial malleolar fracture).
For this procedure, a vertical incision is made medial to the anterior tibial tendon directly over the anterior notch of the medial ankle over a 2-cm length. Alternatively, if the deltoid ligament is to be imbricated, an incision can be made directly over the medial malleolus extending distally to the deltoid. The incision based off the deltoid is more useful if the deltoid is to be imbricated. The incision is deepened through the joint. Then the capsule is incised, and the hypertrophic synovium, capsule, and scar are excised completely from the medial gutter. The insertion of a rongeur is useful; it should be turned around 180 degrees to ensure that the medial gutter is completely free and that the talus is mobile. The medial gutter will again be checked subsequently for correction of the fibular malunion as the talus is pushed over medially. In the cases of fibular malunion without medial malleolar fracture, the deltoid ligament has by definition healed in an elongated and incompetent position. Therefore the deltoid should be imbricated to restore the ligament to a functional length. We perform this by elevating the origin of the deltoid off the medial malleolus leaving a 1- to 2-mm cuff of tissue. Either suture anchors or drill holes can be placed within the medial malleolus as an anchor point. In similarity to a Brostrom procedure, the deltoid is then imbricated with the knots on the distal aspect of the ligament to avoid soft tissue prominence. Further stability is then gained by using number 0 absorbable suture in figure-of-eight fashion for the ligament, incorporating the proximal cuff of tissue ( Fig. 17.5 ).
Fibular and Medial Malleolus Deformity and Osteotomy
The fibula is commonly shortened and externally rotated in a malunion, although only one of these may be present, determining the type of osteotomy and bone graft. Ideally, it should not be necessary to strip the entire syndesmosis to lengthen the fibula. In cases in which the syndesmosis must be included in the procedure, such as arthrodesis requiring creation of a tibia pro fibula, the syndesmosis should be taken down completely ( Figs. 17.6 and 17.7 ; ). If the fibula is externally rotated and not shortened, then a derotational osteotomy can be performed without lengthening, thereby preserving the syndesmosis ( Fig. 17.8 ; ).
An extensile excision is made laterally directly over the fibula, frequently corresponding to the original incision. Existing hardware is removed. The key to this operation is to obtain the correct length and rotation of the distal fibula. These parameters are easy to judge by virtue of the bimalleolar axis, which should be measured out and planned preoperatively by comparison with the contralateral normal ankle. Correction of the external rotation, which is usually present, is not as easy. If healing of the fibula is complete, then an osteotomy has to be performed. This should be done at a level that permits application of adequate fixation distally (see ).
The plane of the fibular osteotomy can be either exactly transverse or oblique. The advantage of a transverse osteotomy is that adequate lengthening of the fibula is far easier to obtain with this type of osteotomy. This is particularly the case if the fibula is short and needs to be lengthened with a laminar spreader. If a transverse osteotomy in the fibula is made, structural interpositional bone graft should be used, provided, of course, that shortening of the fibula is present. Occasionally, external rotation of the fibula is present without shortening, and an internal rotational osteotomy is performed without lengthening (see Fig. 17.8 ).
The alternative is to lengthen the fibula with an oblique osteotomy and to slide the fibula more distally. The better bone contact may obviate the need for an interpositional bone graft, as seen in Fig. 17.9 . In this case, the long oblique malunion of the fibula facilitated an oblique osteotomy with the lengthening, and no bone graft was required ( ). Owing to the ankle valgus deformity and early arthritis, however, a simultaneous osteotomy of the tibia was performed to realign the weight-bearing forces on the ankle. With either type of osteotomy, the syndesmosis needs to be taken down to facilitate the actual lengthening. The tissues surrounding the fibula are stripped, the periosteum is completely elevated, and then the fibula is mobilized on its distal pedicle. If a transverse osteotomy is made, a laminar spreader is inserted in the osteotomy site, the fibula is distracted, and provisional fixation is obtained from the fibula into both the talus and the distal tibia to lock the fibula at the correct length. In the case of a long oblique malunion, bone graft is not usually required, and provided that stable fixation of the fibula and syndesmosis is obtained, the ankle alignment can be markedly improved ( Figs. 17.10 and 17.11 ).
