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4: Lo w er Extrem ity Chapter 38 Ankle Fractures Matt Graves, MD Ankle Fractures Ankle fractures are among the most common injuries treated by an orthopaedic surgeon.1 As with other frac- tures, the treatment goal is expedient return to optimal function in the absence of complications. This goal typ- ically requires an anatomic reduction of the ankle mor- tise with maintenance of ankle joint stability during early, active mobilization. With nondisplaced, stable fractures, function can be achieved nonsurgically. With displaced, unstable fractures, surgical treatment is nec- essary. It logically follows that a clear understanding of displacement and stability is required. More than 50 years after the popularization of surgical treatment, the understanding of these concepts is still being refined. Over the past 5 years, understanding has improved sig- nificantly. These changes will be covered as they relate to the clinical and radiographic evaluation, currently used classification systems, recent modifications of sur- gical treatment, and the complications and expected outcomes of treatment. Initial Evaluation Clinical The patient history focuses on the mechanism and tim- ing of injury, as these provide clues to associated inju- ries and progression of swelling. Specific findings in the history noted to have an adverse effect on outcome in- clude advanced age, osteoporosis, diabetes mellitus, pe- ripheral vascular disease, female sex, and high Ameri- can Society of Anesthesiologists (ASA) class.2-4 The effect of obesity is controversial, as it has had differing effects depending on the study.5,6 Social factors such as smoking, alcohol use, and lower levels of education have been noted as independent predictors of lower physical function postoperatively.7 The presence of these findings should not prevent surgical treatment of unstable, displaced ankle fractures but instead should (1) allow for a more candid preoperative discussion re- garding potential complications and outcome, (2) en- courage more careful soft-tissue handling and attention to construct stability, and (3) encourage treatment of modifiable risk factors during the perioperative period. The physical examination should include a neurovascu- lar examination of the leg and focus on the soft tissue in line with proposed surgical incisions. Dislocations and subluxations should be reduced expediently to take pressure off of the skin and neurovascular bundle and prevent point loading of articular cartilage. This can be accomplished by using intra-articular analgesic injec- tions, intravenous narcotics, or conscious sedation. A recent study compared the efficacy of an intra-articular block to conscious sedation for the closed reduction of ankle fracture-dislocations.8 The intra-articular lido- caine block provided a similar degree of analgesia that was adequate for reduction, and a decreased time to reach the reduced, splinted position. Radiographic Plain radiographs are the standard imaging modality for the evaluation of ankle fractures. Quality imaging is essential and consists of the AP, mortise, and lateral ra- diographs. Each view provides insight into the patho- anatomy of the injury complex. Classic studies have shown that reproducible radiographic measurements can be used to quantify the extent of injury and help predict clinical outcome.9,10 The AP view is defined by placing the long axis of the foot in the true vertical position. In addition to viewing the cortical margins of the malleoli and the ta- lus, it is necessary to evaluate the relationship between the talus and the distal tibial subchondral surface. The tibiotalar joint space should be symmetric with no signs of talar tilt. Markers for syndesmotic injury include the tibiofibular overlap and the tibiofibular clear space (Figure 1, A). The mortise view is defined by internally rotating the leg so that the medial and lateral malleoli are parallel to the tabletop. This typically requires approximately 10° of internal rotation of the fifth metatarsal with respect to the vertical position.11 This rotation is required be- cause the coronal plane of the ankle joint is externally rotated with respect to the coronal plane of the knee joint. It provides the true AP view of the tibiotalar ar- ticulation. In addition to evaluating cortical margins and the tibiotalar joint space, specific radiographic pa- rameters should be noted (Figure 1, B). The tibiofibular overlap is also used in this view to evaluate syndes- motic injury. The medial clear space is considered to be representative of the status of the deep deltoid liga- Dr. Graves or an immediate family member is a member of a speakers’ bureau or has made paid presentations on behalf of Synthes or is a paid consultant for product development and has received research or institutional support from Synthes. 493© 2011 American Academy of Orthopaedic Surgeons Orthopaedic Knowledge Update 10 4: L o w er E xt re m it y ment. Markers for fibular length include the talocrural angle, the Shenton line of the ankle, and the dime sign.12,13 The lateral view is defined by placing the radio- graphic beam perpendicular to the long axis of the an- kle joint (Figure 1, C). It provides for evaluation of the cortical margins of the malleoli, with improved visual- ization of the posterior malleolus. The tibiotalar joint space should be symmetric with no signs of talar sub- luxation. The relationship of the posterior border of the distal fibula to the tibia provides information re- garding syndesmotic competency. Associated or occult injuries are also noted, including fractures of the lateral process of the talus, posterior tubercle of the talus, and anterior process of the calcaneus. The indications for additional imaging modalities such as CT and MRI are unclear. CT has provided for an improved understanding of posterior malleolar frac- ture patterns, articular impaction, and syndesmotic reduction.14-17 MRI has been used to evaluate the com- petency of the syndesmosis and deep deltoid ligament, as well as to better view osteochondral talar lesions as- sociated with ankle fractures.18-20 Classification Danis and Weber/AO The Danis and Weber/AO classification of malleolar fractures focuses on the height of the fibular fracture (Figure 2). The rationale is based on the relationship between the height of the fibula fracture and the asso- ciated damage to the tibiofibular ligaments. The higher the fibula fracture, the more extensive the damage to the syndesmosis, and thus the greater degree of ankle joint instability. A recently published study has sup- ported the reproducibility of this classification system, revealing substantial interobserver and intraobserver agreement using an AP and lateral view of the ankle.21 Although this classification system still is commonly used, some have taken issue with prioritizing the fibula in evaluation of ankle joint stability, as many recent studies have convincingly established the primacy of the deep deltoid and medial malleolus in determining ankle joint stability.22 In addition to this, an MRI study has recently questioned the relationship of the level of fibula fracture to the integrity of the interosseous mem- brane.18 Lauge-Hansen The Lauge-Hansen classification system is an extensive mechanistic system based on a cadaver study that at- tempted to improve the understanding of ankle fracture patterns.23 The first word in the classification system refers to the position of the foot at the time of injury; the second word refers to the direction of the deform- ing force (Figure 2). The system is imperfect. All ankle fractures do not fit neatly into the different classes. The proposed mechanism of injury has been refuted and the interobserver and intraobserver reliability have been questioned; nevertheless, the system is still commonly used.24,25 Much of the recent literature devoted to ankle fractures has used the Lauge-Hansen system; recent treatment advances will therefore be described with re- spect to this system. Treatment Advances Supination-Eversion Supination-eversion (also called supination-external ro- tation) ankle fractures are the most common type seen Figure 1 Standard trauma series for evaluation of ankle pathology. A, AP view. The tibiofibular overlap is measured 1 cm above the plafond. It is the distance between the lateral edge of the Chaput fragment of the distal tibia and the medial border of the fibula. The tibiofibular clear space is measured at the same level and is the distance between the depth of the incisura fibularis and the medial border of the fibula. It reflects the posterior aspect of the distal tibiofibular relationship. B, Mortise view. The medial clear space is the distance between the lateral border of the medial malleolus and the medial border of the talus at the level of the talar dome. The Shenton line of the ankle is noted by following the subchondral bone of the distal tibial articular surface across the syndesmotic space to the small spike of the fibula. The dime sign is the unbroken curve between the lateral part of the articular surface of the talus and the distal fibular peroneal tendon recess. C, Lateral view. Outlines of the medial malleolus (black), lateral malleolus (red), and posterior malleolus (green) are noted. Section 4: Lower Extremity 494 Orthopaedic Knowledge Update 10 © 2011 American Academy of Orthopaedic Surgeons 4: Lo w er Extrem ity clinically, accounting for nearly 70% of all malleolar fractures. The fibular fracture pattern is oblique and oriented from posterosuperior to anteroinferior, typi- cally at the level of the syndesmotic ligaments (Weber B). If there is no associated medial injury, the ankle mortise is thought to be stable, with closed treatment leading to successful long-term outcomes.26 If there is an associated medial malleolar fracture, the ankle mor- tise is thought to be unstable, and surgical fixation is the treatment of choice. Recent literature has centered on the determination of instability in the absence of a medial malleolar frac- ture. Historically, clinical signs and symptoms have been used as a correlate for deep deltoid instability. The presence of these findings, in addition to a radiograph revealing the typical fibular fracture pattern, led to sur- gical management. More recently, findings such as me- dial tenderness, medial swelling, and medial ecchymosis have been identified as inaccurate predictors of instabil- ity.27,28 These soft-tissue findings can be present second- ary to superficial deltoid injury in the absence of deep deltoid compromise. Because of this, radiographic stress examinations have been used to more accurately demonstrate dynamic instability that is not apparent on static radiographs. With the applied stress, a mortise radiographic view is used and the medial clear space is evaluated for widening. This widening represents talar subluxation and is evidence of deep deltoid instability (Figure 3). Both the gravity stress view and the manual stress view have been proposed for differentiating be- tween supination-eversion type II and ligamentous supination-eversion type IV fractures.27-29 Although both views seem to be reliable, the gravity stress view requires less radiation exposure for the surgeon and has been perceived as more comfortable for the patient.30 Most recently, the assumption that a positive ankle Figure 2 The Danis and Weber and Lauge-Hansen classification systems of ankle fractures. (Reproduced with permission from Carr JB, Trafton PG: Malleolar fractures and soft tissue injuries of the ankle, in Browner BD, Jupiter JB, Levine AM, Trafton PG: Skeletal Trauma, ed 2. Philadelphia, PA, WB Saunders, 1998, pp 2327-2404.) Chapter 38: Ankle Fractures 495© 2011 American Academy of Orthopaedic Surgeons Orthopaedic Knowledge Update 10 4: L o w er E xt re m it y stress test represents a complete deep deltoid transec- tion has been questioned.20 In this study, MRI was used as a decision tool in the treatment of ankle fractures. Patients with a positive stress test after an isolated We- ber B lateral malleolus fracture were further evaluated using MRI to determine the status of the deep deltoid. If the deep deltoid is partially intact, the extremity was placed in a walking boot and weight bearing with am- bulation was allowed as tolerated. At short-term follow-up, there was no evidence of residual medial clear space widening, posttraumatic arthrosis, or poor outcomes in this group. Further work will be necessary to clearly define the role of MRI as a decision-making tool in the treatment of ankle fractures. Controversy also exists as to the ideal type of lateral malleolar fixation in this fracture pattern. Lag screw fixation has been efficacious in noncomminuted oblique fractures in patients younger than 50 years, when the fracture was long enough to accept two lag screws at least 1 cm apart.31 Smaller incisions and fewer reports of hardware prominence were noted. More commonly, the implant decision is between the dorsal antiglide plate and the lateral neutralization plate. Although dorsal plating provides the potential advantages of improved biomechanical strength, less soft-tissue dissection, less palpable hardware, and lon- ger screw placement, it provides the potential disadvan- tage of peroneal tendon irritation.32,33 Lateral neutral- ization plating provides the potential advantage of avoidance of the peroneal tendons. To date, no clinical study comparing the two techniques has statistically shown one to be superior.34 To summarize, isolated oblique Weber B lateral mal- leolar fractures can be treated nonsurgically with the expectation of a good outcome. When this form of fib- ula fracture is associated with a medial malleolar frac- ture, surgical treatment is recommended to reduce and stabilize the ankle mortise. In the absence of a medial malleolar fracture, evidence of deep deltoid incompe- tence can be reached through stress views by examining the medial clear space. If instability is present, surgical treatment is recommended. Syndesmotic stability should always be examined via a stress examination while visualizing the tibiofibular clear space and tibio- fibular overlap after fixing other components of the in- jury. Supination-Adduction Supination-adduction ankle fractures are characterized by a transverse, tension-based fibula fracture below the level of the syndesmotic ligaments (Weber A level) with an associated vertical medial malleolar fracture. Be- cause the medial-sided injury is compression based, ar- ticular impaction is often present at the anteromedial corner of the tibial plafond. Evidence of this associated marginal impaction was noted in early descriptions of the Weber A fracture, and highlighted in a more recent case series of supination-adduction ankle fractures.16 Radiographic visualization of this impaction is noted at the medial gutter on the AP and/or mortise view and at the anterior aspect of the plafond on the lateral view. Although cortical reduction reads are often used to en- sure articular reduction in malleolar fractures, the asso- ciated impaction present in these injuries makes this technique less than ideal. Because of this, an anterome- dial approach that allows direct visualization of the ar- ticular surface is a logical choice with this fracture pat- tern. Reduction of the articular surface with possible grafting of the impaction defect is possible. Stabiliza- tion of this medial reduction can take many forms. A recent biomechanical study revealed that a properly ap- plied buttress plate offers a significant mechanical ad- vantage over screw-only constructs. This advantage must be weighed against the disadvantages of greater soft-tissue dissection and more prominent hardware.35 Pronation-Abduction Pronation-abduction fractures are characterized by a tension-based medial-sided injury (deltoid disruption and/or transverse medial malleolar fracture) in associa- tion with a compression-based, comminuted Weber B fibula fracture. More severe pronation-abduction inju- ries often present with transverse medial tension failure soft tissue injuries with extrusion of the plafond. As in the supination-adduction variant of ankle fractures, the compression gutter should be evaluated for plafond im- paction. In the pronation-abduction pattern, the com- pression gutter is the anterolateral corner of the tibial plafond. Because of the primacy of the medial side of the ankle in controlling talar displacement—and the simple transverse fracture noted on the medial side with this pattern—it is logical to fix the medial malleo- lus first if a fracture is present. Through the pull of the deep deltoid, the talus typically returns to its anatomic position in the mortise and indirectly reduces the fibula via the intact lateral ligamentous complex. Extra- periosteal plating is then possible, decreasing the risk of Figure 3 Evaluation of the medial clear space in the pres- ence of an isolated fibular fracture. A, Mortise view of ankle fracture without stress. B, Mortise view of ankle fracture with stress. Widening of the medial clear space reveals a nonfunctional deep deltoid ligament and ankle joint instability. Section 4: Lower Extremity 496 Orthopaedic Knowledge Update 10 © 2011 American Academy of Orthopaedic Surgeons 4: Lo w er Extrem ity fibular nonunion associated with excessive soft-tissue dissection.36 If length is not adequately restored indi- rectly through the pull of the lateral ligamentous com- plex, direct manipulation of the distal fragment and a length-stable fibular construct is required. A stress ex- amination of the syndesmosis is then completed, with fixation recommended if instability is noted upon visu- alization of the distal tibiofibular clear space and over- lap. Pronation-External Rotation Pronation-external rotation injuries are the most unsta- ble of all ankle fracture patterns. Pathoanatomy begins on the medial side with a deltoid disruption and/or a medial malleolar fracture. After disrupting the anterior inferior tibiofibular ligament, a Weber C fibula fracture takes the form of a spiral or oblique pattern. Posterior malleolar injuries are occasionally noted. A syndes- motic disruption is present until proven otherwise and should be addressed if any instability is present. Treat- ment requires an anatomic reduction of the malleolar fractures and the syndesmotic disruption. Outcomes are generally not as good as with other malleolar frac- ture patterns. These deficiencies are likely related to problems with the distal tibiofibular syndesmosis. This specific injury component requires further discussion. Specific Fracture Components Requiring Further Delineation Distal Tibiofibular Syndesmosis The distal tibiofibular syndesmosis is a fibrous articula- tion connecting the tibia and fibula that consists of five parts: (1) interosseous membrane, (2) interosseous liga- ment, (3) anterior inferior tibiofibular ligament, (4) posterior inferior tibiofibular ligament, and (5) inferior transverse tibiofibular ligament. It functions to resist external rotation, axial translation, and lateral transla- tion of the talus. The mechanism of injury is typically severe external rotation of the ankle and foot relative to the position of the tibia. Clinical signs and symp- toms of injury include ecchymosis proximal to the an- kle joint, pain over the anterior inferior tibiofibular lig- ament, pain created while squeezing the tibia and fibula together (“squeeze test”), and pain with an external ro- tation stress test. Classic radiographic signs of injury on the AP view include a tibiofibular clear space of greater than 5 mm and a tibiofibular overlap of less than 10 mm. On the mortise radiograph, a tibiofibular overlap of less than 1 mm is suggested to be pathologic.10 These numbers have been questioned in multiple studies, as th