ABSTRACT

Isolated medial malleolus fractures comprise two-thirds of all ankle fractures and are rarely accompanied by a posterior tibial tendon rupture and dislocation. However, a medial malleolus fracture accompanied by an anterior tibial tendon rupture is unusual, and has not yet been reported. In this paper, a case of medial malleolus fracture accompanied by a tibialis anterior tendon rupture is presented and discussed.

Introduction

Ankle fractures are among the most frequently seen fractures, and age, bone quality, increased body weight, previous ankle fracture, and the mechanism of the injury are the most important risk factors (1,2). The incidence is approximately 187 fractures per 100.000 people each year (3). Isolated medial malleolus fractures comprise two-thirds of all ankle fractures (4) and are rarely accompanied by tendon ruptures. Medial malleolus fractures accompanied by a posterior tibial tendon rupture and dislocation have been reported (5,6), however, a medial malleolus fracture accompanied by an anterior tibial tendon rupture is unusual, and has not yet been reported. In this paper, a medial malleolus fracture accompanied by a tibialis anterior tendon rupture is presented and discussed.

Case

A 54-year-old man was admitted to the hospital with a crush injury of the ankle caused by a log. Physical examination revealed medial left ankle and medial midfoot swelling and tenderness. Limited ankle movement was thought to be due to severe pain. There was no additional injury, and neurovascular examination was normal. On the anteroposterior and lateral radiographs of the ankle, an isolated medial malleolus fracture was seen (Figure 1). After the application of a temporary short-leg splint, the patient was taken into surgery. During the operation, it was noticed that the tibialis anterior tendon had ruptured. After fixation of the medial malleolus by two 4.5 mm cannulated screws, the incision was extended towards the medial cuneiform. It was then detected that the tendon had split from its insertion site. The distal tip of the tendon was slightly shortened and refreshed because of the degeneration. Due the shortening, it was attached to the navicular bone using two 3.5 mm anchors (Figure 2). After fluoroscopic control, the operation was completed, and a short-leg splint in mild dorsiflexion was applied (Figure 3).

The next day, the patient was mobilized on the healthy limb using two Canadian walkers, and was discharged on the second day. The short-leg splint was removed six weeks later, and a rehabilitation program that included passive and active ankle exercises was initiated. Full weight-bearing was allowed in the eighth week after surgery. At the three-month follow up, the patient had a full range of motion (Figure 4), and the American Orthopedic Foot and Ankle Society (AOFAS) score was 90 according to mild pain after a long walk. At the six, 12, and 18 month follow ups, the patient had no complaints, and the AOFAS scores were 100.

Discussion

The tibialis anterior muscle is the most important muscle of the foot for dorsiflexion and is responsible for approximately 80% of the power required for this movement. It occupies the anterior compartment of the leg, and originates from the lateral condyle and upper two-thirds of the lateral surface of the tibia, the interosseous membrane, and the deep surface of the fascia and the intermuscular septum. Its insertion site is on the plantar surface of the first metatarsal and the medial plantar surface of the first cuneiform. It also helps with the inversion of the foot at the subtalar and midtarsal joints, and assists with holding up the medial arch of the foot (7).

Acute rupture of the tibialis anterior tendon is quite rare and traumatic (8-11), and spontaneous ruptures due to gout, systemic lupus erythematosus, rheumatoid arthritis, diabetes mellitus, and psoriasis have been reported (12-15).

The loss of the tendon contour over the ankle and weakness of dorsiflexion of the foot are highly suggestive of a tibialis anterior rupture, but the diagnosis of a ruptured tendon accompanied by a medial malleolus fracture may be overlooked during the physical examination because of pain, swelling, and the limited movement due to the fracture. Direct roentgenograms may demonstrate avulsion fractures at the insertion site. The diagnosis can be confirmed by ultrasound and magnetic resonance imaging (MRI) (9,16). Early diagnosis of the tendon rupture is very important because early repair of the tendon results in a better outcome, whereas delayed surgery often requires grafting and has a lower success rate (17). In this rare injury, surgeons may be suspicious on tendon tension during surgery, and physical examination findings such as edema, swelling and ecchymosis in tendon insertion could be doubted.

Screw fixation and tension band wiring techniques are the most popular fixation methods for medial malleolus fractures (18). Screw fixation could be made by cannulated screws or malleolar screws. The surgeon selects the method depending on the type of the fracture, the size of the fragment, and bone quality, etc. (19). All these methods have successful rates. These fixation techniques are quite stable. In this case, we preferred open reduction for displaced fragment reduction and screw for stable fixation.

Of all the cases reported in the literature, tendon tears accompanying a medial malleolus fracture were diagnosed intraoperatively, and treated with the fixation of the medial malleolus and primary suture of the tendon (6). All the malleolar fractures previously presented were accompanied by posterior tibial tendon ruptures. Din reported a case of anterior tibial tendon injury associated with a closed midshaft tibial fracture (20). However, there have been no reports of medial malleolus fractures accompanied by anterior tibial tendon tears in the literature. In this case, the anterior tibial tendon tear was detected during surgery for the medial malleolus fracture. Depending on the shape of the fracture, this injury may occur due to trauma and direction of the forces applied to the foot. The tendon ruptured from its insertion site, unlike those presented in the literature, and was attached to the navicular bone using two anchor sutures after the stabilization of the medial malleolus fracture. No complications occurred and the patient had full movement of the ankle three months after surgery.

Although it is a very rare occurrence, anterior or posterior tibial tendon tears may accompany medial malleolus fractures. Lack of an early diagnosis can result in major complications. Thus, palpation of the tendons and checking for local tenderness are very important during the physical examination. Patients should be evaluated with ultrasound and MRI in addition to radiographs if required.