Evaluation and Treatment of Ankle Syndesmosis Injuries

Transcription

1 55 Evaluation and Treatment of Ankle Syndesmosis Injuries David A. Porter, MD, PhD Abstract Athletes sustain ankle syndesmosis injuries far less frequently than they do lateral ankle sprains; however, syndesmosis injuries are more challenging to detect and treat. Grade II injuries, which are occultly unstable, may be overlooked or treated too conservatively (nonsurgically), leading to latent diastasis, chronic instability, further injury, arthritic changes, chronic pain, osteochondral lesions, and other sequelae. Surgical intervention for chronic syndesmosis injuries produces mixed results and creates an uncertain future for athletes who desire to return to their sport. Optimal treatment starts with a comprehensive evaluation that includes a thorough physical examination as well as imaging studies to evaluate for instability (medial clear space widening and syndesmosis disruption). All acute unstable syndesmosis injuries (grades II and III) should be treated with surgery, which can include repair of the deltoid ligament with open reduction and internal fixation of the syndesmosis. Isolated deltoid sprains also are often repaired surgically in athletes. This more aggressive treatment helps avoid the chronic pain and instability and osteochondral abnormalities associated with chronic injury. Instr Course Lect 2009;58: The annual incidence of ankle syndesmosis injuries is approximately 15 cases per 100,000 individuals in the general population. 1 The incidence is higher in athletes, whose susceptibility to this injury is increased because of their participation in activities that involve planting the foot and then cutting motions as well as direct blows to the lateral ankle. Exact figures are elusive because differences in injury reporting do not capture all cases, but estimates indicate 1% to 18% of all ankle sprains are syndesmosis injuries. 2,3 Although this type of injury is seen less frequently than lateral ankle injuries, syndesmosis injuries can be more challenging to diagnose and treat. Although a complete syndesmotic disruption is easy to detect, more subtle injuries often go unnoticed. One survey of physicians and trainers who care for professional athletes identified syndesmosis injuries as the foot and ankle injury that is most difficult to treat. 2 Although significant morbidity is associated with such injuries, 4 syndesmotic disruption can cause persistent disability in competitive athletes. Patients with syndesmosis injuries frequently require almost twice as much time to return to sport compared with patients who have lateral ankle sprains. 3 Early diagnosis with appropriate treatment is preferable to late diagnosis because a chronic injury can be problematic, often leading to suboptimal and sometimes uncorrectable outcomes. 5 Syndesmosis Anatomy and Physiology The syndesmosis (also called the interosseous membrane) allows the tibia and fibula to work together as a single unit, providing stability to the lower leg and actions of the foot and ankle complex. At the distal ends of these two bones, the anterior-inferior tibiofibular ligament (AITFL), the posterior-inferior tibiofibular ligament, and the interosseous ligament lend stability to the ankle mortise and maintain the fibula in the incisura fibularis tibiae. The deltoid ligament helps maintain the syndesmosis indirectly by stabilizing the medial ankle mortise. Under normal circumstances, this configuration is so stable that the syndesmosis and the ankle mortise widen only approximately 1 mm during gait. 3 A syndesmosis sprain results from sustained forceful external rotation with abduction and dorsiflexion. Classification of Injury Syndesmosis injuries involve disruption of the ligamentous structures between the distal fibula and tibia as well as a disruption of the deltoid ligament medially. Forceful external rotation and abduction of the ankle widens the ankle mortise AAOS Instructional Course Lectures, Volume 58,

2 Foot and Ankle Figure 1 Classification of syndesmosis injury. See text for details. A, Grade I. B, Grade II. C, Grade III. (Reproduced with permission from Porter DA: Ligamentous injuries of the foot and ankle, in Fitzgerald RH, Kaufer H, Malkani AL (eds): Orthopaedics. St Louis, MO, Mosby, 2002, pp ) as the talus pushes the distal fibula laterally away from its articulation with the distal tibia. Stretching or tearing of the syndesmosis, deltoid, and associated ligamentous structures results in diastasis. A proximal fibular fracture can be involved in more severe injuries. A grade I injury involves injury to the anterior deltoid ligament and the distal interosseous ligament but without tearing of the more proximal syndesmosis or the deep deltoid ligament.6 The AITFL often is very tender to palpation and may have a higher grade injury; because no diastasis is present, the injury is, by definition, stable. A grade II injury involves disruption of the anterior and deep deltoid ligaments as well as a tear in a significant portion of the syndesmosis, resulting in an unstable ankle that is still normally aligned on nonstress radiographs. A grade II injury poses particular diagnostic challenges because the extent of the injury and its occult instability are often more difficult to recognize. Underestimating the injury or using a nonstabiliz576 ing treatment can have devastating consequences for the patient. A chronic, unstable syndesmosis can predispose the patient to further injury, arthritic changes, chronic pain, osteochondral lesions, and other sequelae.5 A grade III injury involves severe external rotation and abduction, with complete disruption of the medial ligaments and extensive disruption of the syndesmosis, frequently accompanied by fracture of the proximal fibula (Maisonneuve). Such injuries are overtly unstable on initial examination and standard radiographs. The classification of injury is shown in Figure 1. eral ligaments (anterior talofibular and calcaneofibular ligaments) but because less tension is placed on them with walking (compressive forces laterally in a valgus-aligned hindfoot), healing often is unremarkable. A grade II syndesmosis injury can lead to complications if not diagnosed and treated properly. Insight gained from observation of the varus-valgus resistance seen in the knee and mirrored in the ankle sheds light on potential pitfalls in assessing and treating occult syndesmosis instabilities. Current opinion is divided regarding surgical intervention of grade II injuries;7 however, some authors agree that all acute unstable syndesmosis injuries (grades II and III) should be treated surgically.8 Aggressive stabilization (open reduction and internal fixation) of the syndesmosis as well as surgical repair of the deltoid ligament is considered a more conservative approach to a grade II injury than nonsurgical treatment because repair of a chronic syndesmosis insufficiency yields poor results. Although nonsurgical treatment of a grade II injury can be successful, a suboptimal result makes it difficult for the athlete to return to sports activity. The challenge is to uncover occult instabilities before they become chronic and debilitating. Physical Examination Understanding Why Syndesmosis Injuries Often Lead to Complications and Chronic Injury The deltoid is twice as strong as the ankle s lateral ligaments.1 Thus, a tear of the deltoid leads to collapse of the hindfoot into valgus (because of the tensile stresses). In contrast, severe plantar flexion with inversion can lead to a complete tear of the lat- Palpation of the ankle produces tenderness along the anterior deltoid (in all grades) and the deep deltoid (particularly in grades II and III). Tenderness also is noted along the length of the syndesmosis in all grades of injury. With grade II and III injuries, the tenderness often extends at least one third to one half the length of the leg. The anterior talofibular ligament often is not ten- AAOS Instructional Course Lectures, Volume 58, 2009

3 Evaluation and Treatment of Ankle Syndesmosis Injuries Chapter 55 der, but significant tenderness is found in the AITFL, deltoid, and syndesmosis. Palpating the full length of the fibula can reveal evidence of a Maisonneuve fracture. It is also helpful to examine areas of swelling. In particular, swelling medially over the deltoid is highly suggestive of deltoid injury and, thus, a syndesmosis injury also is likely. Fites and associates 5 recommended that if swelling above the joint line between the tibia and fibula occurs less than 24 hours after injury, consider it a syndesmosis injury until proven otherwise. Although sometimes difficult to identify, it is important to attempt to determine if tenderness exists along the medial neck of the talus rather than along the deep deltoid. A highgrade lateral ankle sprain can result in medial impingement and medial talar neck pain (as opposed to softtissue tenderness of the deep deltoid). Another important clinical finding is that patients have difficulty bearing weight with an unstable syndesmosis injury. This denotes a more significant injury than a lateral ankle sprain. Numerous biomechanical tests have been used to determine if diastasis is present in a syndesmosis injury. The most reliable test is an external rotation test (Figure 2). A positive test will produce pain at the ankle or the syndesmosis. However, the external rotation test is not always helpful in determining the stability or instability of the syndesmosis. Figure 2 External rotation test. The foot and ankle are held with one hand and the upper leg stabilized with the other hand. The foot and ankle are externally rotated to check for pain in the ankle or leg. A, Medial view. B, Frontal view. (Reproduced with permission from Porter DA, Schon LC: Ankle sprains, ankle instability and syndesmosis injuries, in Porter DA, Schon LC (eds): Baxter s The Foot and Ankle in Sport, ed2. Philadelphia, PA, Mosby, 2008, pp ) Imaging Studies Much has been written about measuring the tibia-fibula interval and overlap on standard radiographs as a way to assess diastasis. 2,9 However, Gardner and associates 10 maintain that no optimal radiographic measurement exists for assessing syndesmotic integrity. Measurements of the tibia-fibula interval and overlap can be unreliable indicators of the stability of a diastasis because the measurements are highly dependent on the rotation of the ankle during positioning for radiographs. Also, the depth of the fibular notch varies because of size differences in the tibial tubercles that bind the lateral surface of the tibia anteriorly and posteriorly, thus making the measurements too variable to draw consistent conclusions. The medial clear space is a reliable indicator of instability. Generally, the determination is made by assessing the cartilage interval between the dorsal talus and the distal tibia (the tibial-talar interval). The interval between the medial malleolus and medial talus should be the same as this or within 1 to 2 mm (Figure 3). With the ankle in neutral dorsiflexion, any widening at the medial clear space of more than 2 mm larger than that of the tibial-talar interval is highly suggestive of deltoid rupture and instability. These measurements must be taken in the context of the patient s history and clinical findings (external rotation injury, significant swelling, tenderness over the deltoid and syndesmosis, positive external rotation stress test). Routine radiographs are obtained on all patients with significant injuries, especially those in whom syndesmosis sprain is suspected. If possible, weight-bearing radiographs are obtained in the AP, lateral, and mortise views. If a proximal fibular fracture is suspected, weightbearing radiographs of the entire tibia and fibula are obtained. External rotation stress radiographs of the ankle are obtained if the patient his- AAOS Instructional Course Lectures, Volume 58,

4 Foot and Ankle Figure 4 Removable walking boot with built-in cold compression. Figure 3 Measurement of the tibiotalar interval compared with medial clear space. A, AP view. B, Mortise view. (Reproduced from Wuest TK: Injuries to the distal lower extremity syndesmosis. J Am Acad Orthop Surg 1997;5: ) tory, physical examination, and standard radiographs do not clearly delineate stability or instability. A local ankle block can be used, if necessary, to obtain these stress images. If stability is still in doubt after these assessments, the patient can return in 1 week for reevaluation and repeat imaging studies or an MRI can be obtained. In some situations, MRI may be indicated to define the degree of anatomic injury. MRI also is helpful when the mechanism of injury is unknown or if stability is still in doubt. MRI and CT can provide images in the frontal, axial, and sagittal planes. Some believe that axial plane CT better shows small diastases (2 to 3 mm). Another advantage of MRI and CT is that three-dimensional reconstructions can be made of the distal tibia-fibula complex. 2,9 Because the degree of injury can be difficult to determine, repeat examinations and radiographs of grade I injuries are recommended 1, 2, 4, and 6 weeks after injury. If the ankle is unstable, surgery is planned. A good reduction is the only significant predictor for functional outcome in this type of injury Treatment Overview Grade I syndesmosis injuries are treated nonsurgically. Boot immobilization and cold therapy are used for comfort and assisting in rehabilitation (Figure 4). To ensure that the syndesmosis is stable, the examination and radiographs are repeated every 1 or 2 weeks until long-term stability is ensured. Patients use crutches only 1 to 2 weeks for comfort; then the athlete gradually is weaned out of the boot between 3 and 6 weeks, into either an off-the-shelf stirrup brace or a custom short articulating ankle-foot orthosis. During this time, exercises are initiated, gradually moving from range of motion and stretching exercises to a bike program and balancing exercises. The average time to return to sport after this injury is between 4 and 8 weeks. Grade II and III injuries, by definition, are unstable. There is a consensus that surgical intervention is always needed for grade III injuries. Although opinion is divided regarding surgical treatment of grade II injuries, 7 some authors advocate surgical treatment for all unstable tears (grades II and III), believing that it is preferable to err on the side of surgical treatment with open reduction and internal fixation of grade II injuries than to risk the sequelae of chronic instability. 11 Acute Versus Chronic Syndesmosis An acute syndesmosis injury is one that has been present less than 4 weeks. The goal is to reestablish stability and prevent it from becoming a chronic injury. Patients with acute injuries can have a good outcome if anatomic alignment is restored. Various authors have documented that a good reduction is the only predictor of outcome with syndesmosis injuries A recent retrospective study found that 98% of surgically treated patients were still pain free after 2 years, and their overall functional scores on the AAOS Foot and Ankle Module Assessment averaged A chronic injury is one that has been present at least 3 months. During the time it takes for an acute injury to develop into a chronic injury, outcome is uncertain. A chronic injury may be the result of many causes, including misdiagnosis, late diastasis, and subtle fibular malre- 578 AAOS Instructional Course Lectures, Volume 58, 2009

5 Evaluation and Treatment of Ankle Syndesmosis Injuries Chapter 55 duction. 10 Pain is the complaint that causes many patients to seek medical evaluation. The key goal of treatment of this difficult condition is to reestablish anatomic alignment with long-term stability. However, detailed evaluation is required to uncover the source of the patient s symptoms. MRI and CT can uncover distal adhesions, malreductions, and other conditions that plain radiographs might miss. Gardner and associates 10 reported that the prevalence of malreduction of the fibula may be three times higher than previously published. If previous screw fixation has failed, the syndesmosis must be reconstructed. A preoperative injection of local anesthesia into the area of pain can be both diagnostic and therapeutic in uncovering heterotopic ossification as a source of pain; 2,8 such ossification can be excised surgically. Debris that was not detected or removed previously may be a source of malreduction; this can be excised and the syndesmosis fixed with screws. The medial side of the ankle must be examined and any scar tissue or debris removed to allow anatomic reduction. Treatment may involve excision of medial soft-tissue debris, open reduction with long-term use of screws, reconstruction of lateral ankle ligaments (AITFL and distal syndesmosis), or other interventions. A modified Broström-like procedure can be used to reconstruct the medial deltoid ligament. If insufficient tissue remains for repair, an autologous graft can be taken from the plantaris, the second or third toe extensor, the semitendinosus, or the gracilis. 2 These autografts also can be used to reconstruct the syndesmosis ligament itself, if needed. An autogenous gracilis graft is the author s tissue of choice. A synostosis fusion may be a last resort to maintain stability of the tibia-fibula joint; it may be required if the patient is not an athlete and has a very large body mass (more than 250 lb) or has evidence of early significant arthritic changes in the ankle. Complete ankle fusion is a salvage procedure for extensive tibiotalar arthrosis after failed treatment or chronic injury that has progressed with cartilage destruction. Open Reduction and Internal Fixation for Syndesmosis Reestablishing the correct tibiafibula relationship through anatomic reduction is crucial in unstable syndesmosis injuries. The correct tibia-fibula interval, fibula length, and proper alignment of the fibula in the incisura must be established and maintained. Consideration should be given to repairing the deltoid ligament to allow evaluation of the talar dome and distal tibial cartilage surfaces, including the posterolateral tibia where bone contusions and cartilage injury are most common, and to allow early motion and early weight bearing, which promote cartilage health and collagen repair. 13 In addition, poor surgical and functional outcomes have occurred with chronic deltoid insufficiency. The talar dome bears more weight per unit area than any other joint surface. 1 If the deltoid injury causes even a 1-mm lateral talar shift, the joint contact area decreases by 42%. 7 A lateral talar displacement of more than 2 mm results in a more than 90% chance of degenerative changes unless it is properly realigned. 1 There is no clear scientific evidence for the number of screws or cortices needed to maintain anatomic alignment. 14 Options include two Figure 5 screws. Positioning of syndesmosis screws and four cortices, although three cortices may be used. A four-hole, one third tubular plate with 3.5-mm unicortical screws in the proximal and distal holes for positioning of the plate is used for fixation. With the ankle in neutral dorsiflexion, the reduction is held with a large forceps reduction clamp. Under fluoroscopic guidance, a partially threaded 4.5-mm screw is placed transsyndesmotically 1 cm above the distal tibial plafond. This first screw achieves adequate reduction of the fibula to the tibia. The second, more proximal 4.5-mm screw is a fully threaded neutralization screw that is used for added stability (Figure 5). If an associated Weber C fibular fracture is present, the fibula is fixed anatomically. Sometimes the same plate is used for the syndesmosis screws and the screws to fix the fibular fracture; at other times, two separate plates are used. If the fibular fracture is more than halfway up AAOS Instructional Course Lectures, Volume 58,

6 Foot and Ankle Table 1 Postoperative Rehabilitation Protocol Postoperative Crutches; no weight bearing; elevate leg Walking boot and cold therapy Start home exercise program for stretching 1 week Home exercises (stretches and range-of-motion exercises) Protected weight bearing as tolerated Wean to one crutch 2 weeks Assess range of motion Start home exercises with resistance bands Start weaning out of boot over next 2 weeks to stirrup brace 3 weeks Normal gait in walking boot 1 month Increase in weight-bearing exercises Proprioception (for example, biomechanical ankle platform system or BAPS board) and gait training with brace and athletic shoe are initiated; includes resistance band exercises, stationary bike 6 weeks Start progression from bike to elliptical trainer to stair climbing 8 to 10 weeks Running 2 months Strengthen entire lower extremity; work on sport-specific agility drills 3 months Remove screws 4 to 6 months Return to sport the shaft, fibular fixation is not performed. Reduction is confirmed with an intraoperative stress test. After documented reduction, sutures are tied medially in the deep deltoid and augmented with sutures in the anterior deltoid. (DVD 55.1) The syndesmosis screws (as well as the lateral plate) can be removed from 2 to 4 months after placement. The author s recommendation is that this hardware be removed at 3 months or later, depending on the athlete s choice. Although some sources might argue that this technique causes changes in ankle mechanics and limits range of motion over the short term, this limitation is not as crucial as obtaining and maintaining correct reduction of the syndesmosis and the mortise. 11 Lingering diastasis is a concern with syndesmosis injuries, but with this surgical approach persistent diastasis has not occurred. This surgical technique also allows early weight bearing, prevents disuse atrophy, promotes proprioception training, and hastens return to normal activities. Complications Complications of chronic syndesmosis instability may include deltoid insufficiency, a significant cause of instability, and no good solution currently exists for repair of chronic deltoid injuries. Arthritic changes may develop within 1 year of surgery because of significant impaction injury at the time of the syndesmosis sprain, a fracture that occurred during the injury, or the presence of osteochondral lesions on the tibia or talus. If such lesions occur on the tibia, surgical interventions produce mixed results at best. Tibial osteochondral lesions that are located far posteriorly have better outcomes because they can be resected without significantly affecting the weight-bearing surface. Treatment of other tibial osteochondral lesions is not as successful. Osteochondral changes can occur on the posterolateral area of the ankle because of plantar flexion and slight eversion that occurs with many syndesmosis injuries. However, osteochondral lesions on the talus usually can be treated successfully. The difference in treatment outcomes of osteochondral lesions of the tibia and talus may be because the tibia always is weight bearing, whereas the weight-bearing surface of the talus moves with plantar flexion and dorsiflexion so that an area containing an osteochondral lesion on the talus is only intermittently weight bearing. Screws may break. If this occurs late in the course of treatment and the deltoid ligament is stable, the screws can be removed without compromising stability. However, screw extraction may pose a challenge. Broken cannulated 4.5-mm screws used for syndesmosis fixation can be removed rather easily using the broken-screw removal set with reverse thread extractor. Also, if four cortices are used, the distal broken portion of the screw can be removed from the medial side with less difficulty. Postoperative Rehabilitation The rehabilitation protocol after open reduction and internal fixation of the syndesmosis begins with early protected weight bearing, followed by stretching, proprioception, and weight-bearing exercises, then progression to a bike and stair or elliptical program. Running and sportspecific exercises are incorporated (Table 1). A short articulating ankle-foot orthosis is recommended for protection and to facilitate training. New Treatment Technique: Tightrope Fixation Some surgeons are using a tightrope fixation for syndesmosis injuries. Scientific studies are emerging regarding the effectiveness of this permanent suture and washer approach for such a significant ligament inju- 580 AAOS Instructional Course Lectures, Volume 58, 2009

7 Evaluation and Treatment of Ankle Syndesmosis Injuries Chapter 55 ry. 15 If the fixation is adequate, it will have the advantage of not requiring a second surgical procedure to remove the hardware. Summary The key to treating syndesmosis injuries is to make the correct initial diagnosis and initiate treatment that will produce optimal stability and outcomes with the least chance for complications or chronicity. Tibiafibula diastasis often is overlooked or misdiagnosed. If a diastasis is undetected or inadequately treated, chronic ankle syndesmosis instability, pain, arthritic changes, and other problems will occur. 16 All acute unstable syndesmosis injuries (grades II and III) need surgical intervention. Appropriate treatment of the acute injury is the best solution for avoiding the adverse conditions associated with chronic injury. References 1. van den Bekerom MPJ, Lamme B, Hogervorst M, Bolhuis HW: Which ankle fractures require syndesmotic stabilization? J Foot Ankle Surg 2007; 46: Clanton TO, Paulos P: Syndesmosis injuries in athletes. Foot Ankle Clin North Am 2002;7: Lin CF, Gross MT, Weinhold P: Ankle syndesmosis injuries: Anatomy, biomechanics, mechanism of injury, and clinical guidelines for diagnosis and intervention. J Orthop Sports Phys Ther 2006;36: Nonfatal Occupational Injuries and Illnesses Requiring Days Away from Work. United States Department of Labor News. Washington, DC, Bureau of Labor Statistics, USDL November Fites B, Kunes J, Madaleno J, Silvestri P, Johnson DL: Latent syndesmosis injuries in athletes. Orthopedics 2006; 29: Porter DA: Ligamentous injuries of the foot and ankle, in Fitzgerald RH, Kaufer H, Malkani AL (eds): Orthopaedics. St. Louis, MO, Mosby, 2002, pp Jenkinson RJ, Sanders DW, Macleod MD, Domonkos A, Lydestadt J: Intraoperative diagnosis of syndesmosis injuries in external rotation ankle fractures. J Orthop Trauma 2005;19: Nicholson CW, Anderson RB: Operative treatment of syndesmotic injuries in the competitive athlete. Tech Foot Ankle Surg 2006;5: Zalavras C, Thordarson D: Ankle syndesmotic injury. J Am Acad Orthop Surg 2007;15: Gardner MJ, Demetrakopoulos D, Briggs SM, Helfet DL, Lorich DG: Malreduction of the tibiofibular syndesmosis in ankle fractures. Foot Ankle Int 2006;27: Ebraheim NA, Elgafy H, Padanilam T: Syndesmotic disruption in low fibular fractures associated with deltoid ligament injury. Clin Orthop Relat Res 2003;409: Porter DA, May BD, Berney T: Functional outcome after operative treatment for ankle fractures in young athletes: A retrospective case series. Foot Ankle Int 2008;29: Porter DA, Schon LC: Ankle sprains, ankle instability and syndesmosis injuries, in Baxter s The Foot and Ankle in Sport; ed 2. Philadelphia, PA, Mosby, 2007, pp Moore JA, Shank JR, Morgan SJ, Smith WR: Syndesmosis fixation: A comparison of three or four cortices of screw fixation without hardware removal. Foot Ankle Int 2006;27: Thornes B, McCartan D: Ankle syndesmosis injuries treated with the TightRope suture-button kit. Tech Foot Ankle Surg 2006;5: Ebraheim NA, Taser F, Shafiq Q, Yeasting RA: Anatomical evaluation and clinical importance of the tibiofibular syndesmosis ligaments. Surg Radiol Anat 2006;28: AAOS Instructional Course Lectures, Volume 58,

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