Fig. 28.1
Ankle fracture malunions often lead to posttraumatic arthritis as shown in this radiograph with medial malleolar malreduction allowing lateral subluxation of the talus
Injury of the distal tibiofibular syndesmosis can occur concomitantly with ankle fractures. In general, the estimated rate of ankle syndesmosis injuries has been reported at 2.15 per 100,000 person-years [17]. However, up to 45% of supination external rotation ankle fractures are associated with an unstable syndesmosis disruption [18].
Syndesmosis malunions are prevalent with malreduction rates reported as high as 52% (Fig. 28.2) [19]. The high rate of malalignment has been attributed to the insensitivity of radiographic measures that allow occult syndesmosis injuries to go undetected [20–22]. One study demonstrated that syndesmosis widening evidenced by the tibiofibular clear space from radiographic imaging remained unchanged with up to 30° of external rotation the fibula (Fig. 28.3a, b) [23]. Malreduced syndesmosis disruptions associated with talar malalignment have been associated with instability, pain, and poor functional outcomes [24, 25]. Reduction and stability of the syndesmosis have also been attributed to the posterior malleolar fracture due to its attachment to the fibula via the posterior tibiofibular syndesmosis [26].
Fig. 28.2
Distal tibiofibular malunions are most apparent with frank diastasis of the tibiofibular clear space though most rotational misalignments can be undetected up to 30° of fibular external rotation
Fig. 28.3
(a) Radiographic studies are often insensitive in identifying rotational alignments of the fibular in the fibular incisura of the tibia as seen in this patient with chronic syndesmosis pain from external rotation injury sustained 1.5 years ago. (b) Computed tomography of the same patient case demonstrates widening of the syndesmosis with external rotation of the fibula in the fibular incisura of the tibia not obvious on plain radiograph
Diagnostic Workup
Bilateral weightbearing radiographs can reveal asymmetries to either identify occult malleolar and syndesmosis malalignments or be used for deformity correction planning. Tibiotalar axis which is the middiaphyseal axis of the tibia should bisect the talus. Deviation of tibiotalar axis can demonstrate malalignment of a malleolus, malleoli, or syndesmosis (Fig. 28.4). Medial, tibiotalar, and lateral spaces of the ankle mortise view should be equidistant. On the ankle AP view, the medial clear space and the tibiofibular overlap should also be symmetric. Fibular length may be assessed by comparing bilateral talocrural angles, which is the medial intersection of a perpendicular line from the tibial plafond to the intermalleolar line (Fig. 28.5) [27]. On the ankle mortise view, the tibiofibular clear space should also be symmetric (Fig. 28.6). Alternatively, fibular length may also be measured with the angle of the bimalleolar angle which is the intersection between the line parallel to the fibular shaft and the intermalleolar line. Normal variations of bimalleolar angles in contralateral ankles have been reported to be an average of 1.3° [28]. Other measures of fibular length include Shenton’s line, a curved congruous subchondral bone line from Wagstaffe’s tubercule projecting to the tibial plafond, and the circle sign or dime sign, a concentric curve from the lateral talar process to the fibular recess (Fig. 28.7) [29]. Computed tomography (CT) 2-dimensional images or 3-dimensional reconstructions can provide further information on planes of deformity and the presence of joint degeneration.
Fig. 28.4
Bilateral weightbearing ankle views can reveal asymmetries suggestive of ankle malalignments. The middiaphyseal axis of the tibia bisecting the talus denotes anatomic tibiotalar alignment as shown on the left. Deviation of tibiotalar axis can demonstrate malalignment of a malleolus, malleoli, or syndesmosis as shown on the right
Fig. 28.5
Comparing bilateral weightbearing AP ankle views : medial clear space (b) and tibiofibular overlap (a) of the ankle mortise view should be symmetric. Fibular length may be assessed by comparing the symmetry of talocrural angles, which is the medial intersection of a perpendicular line from the tibial plafond to the intermalleolar line (c). All radiographic values are increased on the right
Fig. 28.6
Comparing bilateral weightbearing mortise ankle views : medial clear space (b) and tibiofibular clear space (a) should be symmetric. Both values are increased on the right and suggestive of deep deltoid and syndesmosis ligament disruption
Fig. 28.7
Shenton’s line is a curved congruous subchondral bone line from Wagstaffe’s tubercule projecting to the tibial plafond and the circle sign or dime sign which is a concentric curve from the lateral talar process to the fibular recess
Radiographic measures used to evaluate the syndesmosis include the tibiofibular clear space on the mortise projection and tibiofibular overlap on the anterior-posterior projection (Fig. 28.6). On the lateral projection, the anterior border of the fibula is often midline of the tibial axis as evidenced by normative data from CT scans [30]. Because radiographic parameters are relatively insensitive for identifying syndesmosis disruptions , CT scans of bilateral ankles are often necessary to identify rotational and translational malalignments otherwise missed on plain radiographs (Fig. 28.3a, b) [30–33].
Indications of Procedure
Restoration of tibiotalar and talomalleolar articular congruity and joint stability are the primary objectives of malleolar malunion and syndesmosis repair. Articular realignment can reduce abnormal focal contact pressures that can lead to advanced cartilage degeneration. Reestablishing tibiotalar joint stability will reduce abnormal joint kinematics leading to degenerative arthrosis, pain, and dysfunction.
Contraindications/Limitations
Specific contraindications to malunion repair should be considered if manifestations of advanced degenerative changes are seen clinically and/or radiographically or if reconstruction cannot achieve joint stability or anatomic articular alignment.
Ankle Malleolar Fracture Malunion
Restoring Fibular Length and Rotation
Loss of length and malrotation of the fibula are the most common causes of talar malalignment within the tibiotalar joint. Fibular fracture displacement alone whether it is shortened, laterally displaced, and/or external rotated does not cause talar instability provided the medial malleolus and the deep deltoid ligament are intact. Lateral talar subluxation is often seen in cases of isolated fibular malleolar ankle fractures with deep deltoid ligament rupture or in bimalleolar/trimalleolar ankle fractures, which are inherently unstable. In either clinical circumstance, the medial restraint (medial malleolus and/or deep deltoid ligament), which provides talar stability, is disrupted allowing the talus to sublux. In most cases, the talus will displace in the direction of the fibula as the lateral collateral ligaments remain intact and the peroneal tendons pull will cause displacement of the fibula (Fig. 28.8a–c). Reestablishing fibular length restores the lateral buttress preventing the talus from subluxing laterally. Correcting fibular rotation restores talofibular articulation, tibiotalar alignment, and congruent range of motion of the tibiotalar joint. Secondarily, failure to restore fibular length will render difficulty with distal tibiofibular syndesmosis reduction.
Fig. 28.8
Anterior-posterior (a), mortise (b), and lateral (c) ankle conventional radiographs of failed nonoperative management of Weber C fibular fracture with deep deltoid ligament disruption and lateral talar subluxation. Anterior-posterior views demonstrate a short fibula is short and wide medial clear space (a), while the mortise view shows both widening of medial and tibiofibular clear space (b)
Through a standard lateral longitudinal incisional approach, fibular length can be achieved by several methods (Fig. 28.9). For isolated fibular malleolar ankle fractures with medial clear space widening, a small medial incisional approach is often needed to debride the scar tissue, which interposes the articulation between the medial malleolus and medial talus preventing reduction (Fig. 28.10a, b). In chronic cases of malunion and medial clear space widening, adhesive fibrosis of the scar tissue can occur along the articular cartilage, therefore, should be debrided carefully. Fibular osteotomy should be performed in the orientation of the original fracture, and the use of an intercalary bone graft should be anticipated for bony deficits encounter with deformity correction (Fig. 28.11a, b). The use of CT imaging can assist in identifying the orientation for the osteotomy. A locking plate is positioned on the lateral fibula held in place with a towel clamp along the proximal segment of the fibular fracture to ensure axial alignment of the plate. The locking plate is secured to the distal fibular fracture with locking screws (Fig. 28.12). In the isolated fibular malleolar or bimalleolar fracture malunions, the use of a Weber reduction clamp placed along the transmalleolar axis can assist in the reduction of the talus axially beneath the tibia during the process of restoring fibular length (Fig. 28.13). Because the fibula is often bound by peripheral scar and fibrosis, achieving fibular length often requires use of an articulated distractor, which is secured to the proximal fibular segment and lengthens the distal fibula through the locking plate (Fig. 28.14). The bolt to the threaded rod is turned providing incremental distraction. The proximal towel clamp secures the position of the plate on the fibula to better resist anterior, posterior, or lateral migration of the distal fibular segment during the lengthening. Appropriate length is determined by restoring fibular symmetry with contralateral ankle radiographs, Shenton’s lines, and the subfibular circle sign. A second towel clamp is applied along the distal malleolus to correct rotational malalignment of the fibula by achieving patency of the lateral talofibular articulation on the ankle mortise view (Fig. 28.15a, b). Once satisfactory fibular length has been achieved and rotation has been corrected, the reduction is stabilized with a locking screw in the proximal fibular segment (Fig. 28.16a–c). Nonlocking screws to secure the proximal portion of the plate may cause loss of rotational correction to the distal fibular segment due to contact of the plate on the irregular lateral surface of the fibula.
Fig. 28.9
Standard lateral approach to ankle reveals fibular malunion with woven bone callus formation the fibular shaft
Fig. 28.10
Clinical (a) and intraoperative fluoroscopy (b) demonstrates medial clear space debridement. Anterior medial ankle arthrotomy is performed, and scar tissue interposed in the medial clear space is carefully debrided
Fig. 28.11
Fibular osteotomy is performed either with sagittal saw or osteotome in the orientation of the original fracture (a). Once fibular malunion deformity correction is performed, spatial bone deficit is often encountered (b)
Fig. 28.12
A locking plate is held on the fibula proximally with a towel clamp to maintain axial alignment of the plate, while the distal portion of the locking plate is secured to the distal fibula with locking screws
Fig. 28.13
A Weber reduction clamp placed across the transmalleolar axis to assist in the reduction of the talar dome within the ankle mortise while achieving fibular length
Fig. 28.14
An articulated distractor is applied to the proximal end of the fibula with a screw and lengthens the fibula through its attachment to the locking plate
Fig. 28.15
Intraoperative fluoroscopy demonstrating application of a towel clamp along the distal malleolus (a). The fibula is rotated until a patent talofibular articulation on the ankle mortise view is achieved on mortise view (b)
Fig. 28.16
Once fibular length and rotation has been corrected, the reduction is stabilized with a locking screw in the proximal fibular segment. Anterior-posterior view of ankle demonstrating patent medial clear space (a). Mortise view of ankle demonstrates equidistant medial, tibiotalar, and lateral clear spaces (b). Lateral view of ankle demonstrates patent tibiotalar joint with fibular positioned anatomically at the posterior ½ of the tibia (c)
Restoring Medial Malleolar Rotation and Alignment
Deformity correction of medial malleolar malunions and nonunions can be complicated by resorptive bone loss and loss of cortical margins to guide anatomic reduction. For the medial malleolar component of ankle fracture cases, CT scan can provide the orientation of the malunion and the plane for intended osteotomy. A standard medial longitudinal or anterior medial curvilinear approach provides adequate exposure. In bimalleolar ankle fracture malunion/nonunion, medial malleolar osteotomy is often performed prior to fibular osteotomy and lengthening to ensure no malleolar obstruction to tibiotalar alignment (Figs. 28.17a–c and 28.18a, b). In cases of bimalleolar or trimalleolar ankle fracture malunions, the fibular malleolus is often fixed first because the ankle joint radiographic landmarks to guide fibular length and rotation are often preserved compared to the few landmarks available to the medial malleolus (Figs. 28.19, 28.20, and 28.21).
Fig. 28.17
Anterior-posterior (a), mortise (b), and lateral (c) ankle conventional radiographs of a 51-year-old female with a trimalleolar ankle fracture sustained 4 months prior treated nonoperatively at an outside facility presenting with resultant malunion/nonunion and pain with walking
Fig. 28.18
Intraoperative fluoroscopy demonstrating medial malleolar osteotomy (a) and lateral malleolar osteotomy (b)
Fig. 28.19
Fibula is lengthened and stabilized with positional screws and locking plate
Fig. 28.20
Weber reduction forceps are used to reduce the chronic syndesmosis diastasis and allow the fibula to buttress the talus into the ankle mortise. Towel clamp is applied to the fibular malleolus to correct the talofibular articulation and concomitantly the syndesmosis
Fig. 28.21
Once fibular rotation is corrected, two-positional 3.5 mm tetracortical transyndesmotic screws are placed to maintain reduction of fibular rotation and syndesmosis
Because of the deformity from the malunion and subsequent bony gap that is encountered with subsequent realignment of the medial malleolus, cortical landmarks available to guide reduction may be limited. The only method of reduction to ensure anatomic congruity of the medial malleolar-talus articulation is through indirect reduction of the medial malleolus through loading of the tibiotalar joint. Once the medial malleolar osteotomy is performed, loading the ankle at 90° will allow full contact of the tibiotalar articulation stabilizing the tibiotalar joint by realigning the tibiotalar axis [8]. Secondarily, while the tibiotalar joint is loaded and axis corrected, the congruity of the medial malleolar-talus articulation allows correct rotation and alignment of the medial malleolus (Fig. 28.22). Because a bony defect is frequently encountered , in bicortical fixation fully threaded 3.5 or 4.0 mm cortical screws are used as positional screws to bridge the gap and maintain correction (Figs. 28.23a–d and 28.24a–c). Alternatively, an angled locking plate may also be used to bridge the bony defect.
