Deltoid and Syndesmosis Ligament Injury of the Ankle Without Fracture

Deltoid and Syndesmosis Ligament Injury of the Ankle Without Fracture Chris D. Miller, MD, Walter R. Shelton,* MD, Gene R. Barrett, MD, F. H. Savoie, MD, and Andrea D. Dukes, MS From the Mississippi Sports Medicine and Orthopaedic Center, Jackson, Mississippi ABSTRACT Ankle diastasis without fracture is a rare injury with few examples reported. We report on four male patients, aged 16 to 18 years, who sustained this injury playing football. Swelling and tenderness over both the deltoid and syndesmosis ligaments are the most common physical findings. Plain ankle radiographs demonstrated lateral talus subluxation in three patients, and a stress radiograph demonstrated subluxation of the talus in one patient. Treatment consisted of reduction and fixation of the syndesmosis with a screw followed by 6 weeks of cast immobilization. Using the scale developed by Edwards and DeLee, three patients had excellent results and one had a good result. Diagnosis of tears of the deltoid and syndesmosis ligaments without fracture requires a high index of suspicion on the physician s part. In patients whose mortise is more than 1 mm subluxated, reduction and screw fixation will produce good results. *Address correspondence and reprnt requests to Walter R Shelton, MD, Mississippi Sports Medicine and Orthopaedic Center, 1325 East Fortification Street, Jackson, MS 39202 No author or institution has received any financial benefit from research m this study Diagnosis of most ankle dislocations and fractures is easy because of obvious clinical and radiographic findings. However, tears of the distal tibiofibular syndesmosis and deltoid ligament without fracture can be more subtle in appearance, both clinically and on plain radiographs. Diagnosis can be difficult unless the physician has a high index of suspicion for the injury. Ankle diastasis is most commonly associated with the classic fracture that Maisonneuve described in the 19th century. A ligamentous injury at the ankle without a fracture is an infrequent injury with few reports. Ashhurst and Bromer,l Menelaus, and Staples&dquo; have described patients with lateral displacement of the fibula and resultant lateral subluxation of the talus. Numerous authors have reported on an injury to the syndesmosis in which the distal fibula is rotated posteriorly and trapped behind the tibia, resulting in posterior subluxation or dislocation of the ta- IUS.5,6,12,15,16 A more severe injury results when there is complete ankle diastasis with superior dislocation of the talus between the fibula and tibia. 10, 15 Edwards and DeLee combined reports and developed a classification system of four different types of ankle diastasis without fracture. Types I and II correspond to the straight lateral injury with lateral subluxation of the talus; the only difference between types I and II is a plastic deformity of the fibula in type II injuries. Type III is a posterior rotatory displacement injury of the fibula and talus, and type IV is a complete ankle diastasis with superior talus subluxation. Our four cases of ankle diastasis without fracture were classified as Edwards and DeLee type I. Our experience with these four athletes has led to an awareness that ankle diastasis without fracture injuries have increased. MATERIALS AND METHODS During 2 months in the fall of 1993, four patients were treated for type I ankle diastasis injuries without fracture at the Mississippi Sports Medicine and Orthopaedic Center. All patients had closed injuries after they were hit during contact football on the lateral aspect of the ankle when the foot was planted firmly in a weightbearing position. All patients had pain and swelling in the affected ankle. Tenderness and swelling were noted over the deltoid and syndesmosis ligaments. Only one patient had swelling and pain in the anterior talofibular ligament region. Syndesmosis tenderness was distinctly more proximal than that observed in routine ankle sprains. No patient had tenderness over the middle or proximal fibula. Anteroposterior, lateral, and mortise radiographs were obtained in all patients. In three patients, ankle diastasis was seen with widening of the medial ankle joint space of greater than 1 mm. In one patient, plain radiographs were normal but physical examination revealed significant deltoid and syndesmosis pain and swelling. A stress radiograph demonstrated greater than 1 mm of subluxation of 746

747 the talus in the ankle mortise. Full films of the complete tibia and fibula were obtained in all cases, and no fractures were seen. All patients who demonstrated subluxation greater than 1 mm were treated with reduction of the subluxation and with percutaneous placement of a single syndesmosis screw from lateral to medial within 7 days of presentation. We used a 4.5-mm AO screw with purchase on the medial cortex of the tibia. One patient also underwent open repair of the deltoid and anteroinferior tibiofibular ligaments as preferred by the attending surgeon. Postoperatively, all patients were immobilized in a short leg cast. At 6 weeks, the cast was taken off and the syndesmosis screw was removed in three patients, followed by aggressive range of motion, strengthening exercises, and weightbearing. One patient, who failed to have his syndesmosis screw removed at 6 weeks, began weightbearing after cast removal. The screw broke at 4 months after surgery and was subsequently removed. RESULTS All patients were evaluated at 6 months after surgery and rated according to the scale developed by Edwards and DeLee (Table 1). All ankle ligaments were stable on physical examination, with no residual subluxation on radiographs at followup (range, 8 to 10 months). Three patients were rated as having excellent results with no swelling or instability (Table 1). Each patient had a normal gait, and ankle motion was normal and equal to the opposite side. Radiographs showed complete and concentric reduction of the ankle in the three patients who had excellent results. The fourth patient, who had a good result, had very slight TABLE 1 a Ankle Rating Scale&dquo; a Rating scale developed by Edwards and DeLee is excellent, 0 points; good, 1 to 3 points; fair, 4 to 6 points; poor, >6 points. pain with excessive activity (Table 1). Strenuous activity caused him to slightly favor the affected ankle; otherwise, the patient had a normal gait. His ankle motion was normal and equal to the opposite side, but radiographs revealed slight calcification of the syndesmosis. Slightly low placement of the syndesmosis screw at a point 1.5 cm proximal to the tibiotalar joint and the proximal end of the tibiofibular syndesmosis joint was believed to cause his pain. He was the only patient to achieve less than an excellent result, a score of three (good) on the scale developed by Edwards and DeLee. Despite his result, the patient earned a college football scholarship after his senior high school season. One patient, who had an excellent score, had numbness along the sole of his foot and developed claw toes. At 10 months after surgery, he was evaluated with EMG and nerve conduction studies, which showed a partial conduction block of the posterior tibial nerve behind the medial malleolus. A surgical exploration revealed a stretch type injury of the posterior tibial nerve involving a 1-inch segment posterior to the medial malleolus. The injury, which was not initially recognized, was believed to be due to a stretch of the posterior tibial nerve during the original subluxation and lateral displacement of the talus. A complete neurolysis was done, and followup revealed partial but incomplete recovery. The patient has a mild clawtoe deformity that does not require surgery. DISCUSSION Anatomy The syndesmosis of the ankle, composed of the distal articulation of the tibia and fibula, is stabilized by four separate ligaments: the anterior and posterior inferior tibiofibular ligaments, the transverse tibiofibular ligament, and the interosseous membrane (Fig. 1). The integrity of these ligaments is essential for the maintenance of the ankle mortise. According to the scale developed by Edwards and DeLee, type III and IV injuries are obvious on radiographs and diagnosis is not difficult. The physician s challenge is to 1) detect a type I or type II injury where the diastasis is subtle and 2) differentiate between a stable ankle sprain and a disruption of the deltoid and syndesmosis ligament, which can be difficult. Careful evaluation, including physical examination for swelling and pain over the deltoid and syndesmosis ligaments and demonstration of lateral talus subluxation by either plain or stress radiographs, is the key to making the diagnosis. Tenderness in the region of the syndesmosis is characteristically more proximal than that associated with a tear of the anterior talofibular ligament. Other findings that help in the diagnosis are 1) the exacerbation of pain on dorsiflexion of the ankle as the anterior talus spreads the syndesmosis, 2) a positive result on the Hopkinson squeeze test, which is performed by squeezing the tibia and fibula together at the midshaft, producing syndesmosis pain, and 3) a positive result on the Kleiger

748 Figure 1. Anatomy of the syndesmosis of the ankle. test (external rotation test), 2,4 which is performed by placing the ankle at the neutral position with the knee flexed 90, eliciting syndesmosis pain with external rotation stress. The diagnosis was achieved using careful physical examination, which demonstrated pain and swelling over the syndesmosis and deltoid ligaments. The physical examination was followed by plain radiographs and lateral stress radiographs if needed. Radiology Proper radiographs are essential for the diagnosis. Radiographic evidence of syndesmosis injury, as defined by Sclafani,13 includes more than 5 mm of widening of the anterior tibial tubercle-fibular space on the mortise view or the posterior tibial tubercle space on the AP view, widening more than 5 mm of the medial ankle joint space on the AP view, or asymmetry of the tibiotalar crescents on the lateral view (Fig. 2A). To differentiate between a stable ankle sprain and a diastasis, stress views of the ankle are often required. 8,11,14 Edwards and DeLee3 defined widening of the medial ankle joint space of greater than 1 mm compared with the normal side as evidence of a lateral syndesmosis injury. We have used this criterion in diagnosing syndesmosis disruption because all four patients demonstrated widening of the medial ankle joint space and had tibiofibular syndesmosis greater than 1 mm. One patient required a stress view to demonstrate this widening (Fig. 2B). Marymont et al.$ described the use of radionuclide imaging in the detection of syndesmosis injuries and showed it could be effective when stress radiographs could not be obtained. We have no experience using this test for diagnosis. Our diagnostic steps included careful examination of AP, lateral, and mortise radiographs of the ankle, followed by lateral stress radiographs of the ankle if the diagnosis was still not evident. Treatment Rupture of the deltoid and syndesmosis ligaments should be treated aggressively to ensure anatomic restoration of the mortise and congruent reduction of the talus within the ankle joint. Surgery was our treatment of choice in all four patients. We believed that surgery ensured a complete reduction of the injury, and that it would guard against late subluxation of the ankle mortise that might occur with cast immobilization. Reduction was accomplished and held with a syndesmosis screw inserted from the lateral side. The screws used were 4.5-mm AO screws, and purchase was obtained on the medial cortex of the tibia. Staples 14 states that an interposed deltoid ligament can block complete reduction of the mortise and that open repair of the deltoid ligament may be necessary to achieve a concentric reduction. Routine repair of these ligaments can be done if desired by the surgeon ; however, it is not essential for an excellent result if complete reduction is maintained. In our series, one of the four patients had an open repair of the deltoid ligament and anterior talofibular ligament because of the preference of the treating surgeon. A radiograph taken in surgery after reduction of the mortise and

749 / 1 ~ 1 Figure 2. Radiographs demonstrate occult syndesmosis injury without fracture. Note that subtle subluxation on the resting mortise view is more apparent on the stress view. A, mortise view. B, stress view. insertion of the screw should be done to ensure that a complete and concentric reduction of the ankle mortise has been achieved and that there is no interposing soft tissue. After surgery, all four patients were immobilized for 6 weeks in a short leg cast to protect the repair. Edwards and DeLee immobilized their patients for 8 to 12 weeks, and they noted that the patients developed stiffness. At followup, stiffness was not a problem for our patients, and all repaired ankles regained full range of motion. The syndesmosis screw should be removed at 6 weeks postoperatively, and an aggressive rehabilitation program of range of motion, strengthening exercises, and weightbearing should be initiated. The only patient in our series who elected not to have the screw removed at 6 weeks had eventual breakage of the screw at 4 months, but this did not affect his final outcome. In a patient in which ankle diastasis without fracture is properly recognized and a stable reduction is achieved and maintained, good results can be expected. The patient should be informed that recovery will take longer than that for a normal sprain because of the increased number of ligaments involved and the increased severity of the tear (i.e., a complete tear versus a stretch). CONCLUSIONS Tears of the deltoid and syndesmosis ligaments without fracture is an unusual injury that requires a high index of suspicion on the physician s part. The diagnosis should be suspected in a patient who exhibits swelling and tenderness over the deltoid and syndesmosis ligaments. Plain radiographs should be carefully examined to rule out lateral subluxation of the talus in the ankle joint, and stress radiographs should be done if necessary. Successful treatment depends on recognizing the injury, followed by reduction of the mortise within 3 weeks in all patients who have greater than 1 mm lateral subluxation of the ankle mortise as seen on radiographs. We recommend maintaining this reduction with a syndesmosis screw rather than a cast because of the theoretical catastrophic results that could be produced with only a 1 mm residual subluxation of the talus. Reduction of the ankle mortise more than 3 weeks after injury becomes increasingly difficult because of the interposition of scar tissue between the tibia and the fibula. Recovery time will be longer than for the more common lateral ankle sprain. Good results can be expected if the injury is recognized early, reduced, and held with a screw for 6 weeks, followed by removal of the screw and institution of an ankle rehabilitation program. ACKNOWLEDGMENT The authors thank Michael Schenk, University of Mississippi Medical Center, for preparing the illustrations. REFERENCES 1 Ashhurst APC, Bromer RS Classification and mechanism of fractures of the leg bone involving the ankle. Arch Surg 4 51-129, 1922 2. Boytim MJ, Fischer DA, Neumann L Syndesmotic ankle sprains Am J Sports Med 19 294-298, 1991

750 3 Edwards GS, DeLee JC Ankle diastasis without fracture Foot Ankle 4. 305-312, 1984 4 Hopkinson WJ, St Pierre P, Ryan JB, et al Syndesmosis sprains of the ankle. Foot Ankle 10 325-330, 1990 5 Kirschenmann JJ Rotated fibula N Y State J Med 37 1731-1732, 1937 6. Lovell ES An unusual rotatory injury of the ankle J Bone Joint Surg 50A. 163-165, 1968 7 Maisonneuve JG Recherches sur la fracture du perone Arch Gen Med 7 165-187,433-473,1840 8 Marymont JV, Lynch MA, Henning CE: Acute ligamentous diastasis of the ankle without fracture: Evaluation by radionuclide imaging Am J Sports Med 14 407-409, 1986 9 Menelaus MB Injuries of the anterior inferior tibiofibular ligament. Aust N Z J Surg 30. 279-287, 1961 10. Milliken SM Complete dislocation of ankle without fracture of leg bone Ann Surg 69. 650-651, 1919 11 Neer CS II Injuries of the ankle joint evaluation Conn State Med J 17 580-583, 1953 12 Olerud S. Subluxation of the ankle without fracture of the fibula J Bone Joint Surg 53A 594-596, 1971 13 Sclafani SJA Ligamentous injury of the lower tibiofibular syndesmosis: Radiographic evidence Radiology 156 21-27, 1985 14 Staples OS. Ligamentous injuries of the ankle joint Clin Orthop 42 21-35, 1965 15 Wilson MJ, Michele AA, Jacobson EW Ankle dislocations without fracture. J Bone Joint Surg 21 198-204, 1939 16 Woods RS. Irreducible dislocation of the ankle joint BrJSurg29 359-360, 1942