Recurrent ankle sprains secondary to nonunion of a lateral malleolus fracture
Article Outline
Abstract
A case of an adult man with symptoms of chronic recurrent ankle sprains secondary to nonunion of a fracture of the tip of the lateral malleolus is presented. The nonunion was debrided, bone grafted, and internally fixed by using the tension band wire technique. The fracture healed and the patient experienced no further episodes of ankle sprain. (The Journal of Foot & Ankle Surgery 42(1):45–47, 2003)
Keywords: lateral malleolus, nonunion, recurrent ankle sprains
Treatment of the lateral malleolus fracture generally is straightforward and complete healing is usually the case. Nonunion of a lateral malleolus fracture is very rare but nonunion of an isolated fracture of the tip of the lateral malleolus is even more uncommon 1, 2, 3, 4, 5, 6, 7, 8, 9. Nonunions after these avulsion injuries often follow initial closed treatment and fail to unite because of residual displacement of the fracture, interposed soft tissue, or associated lateral instability.
Symptomatic nonunions can be treated with open reduction and internal fixation or removal of the un-united portion. However, excision of the fragment may compromise lateral ankle ligament integrity if the calcaneofibular ligament was responsible for the avulsion injury. Therefore, attainment of union may be desirable to ensure ligamentous integrity and balance. We present such a case of fracture and nonunion of the lateral malleolar tip treated with open reduction and internal fixation.
Case report
A 36-year-old man presented to the Accident and Emergency Department with swelling and tenderness of both malleoli after a twisting type of injury to the left ankle. The radiograph of the ankle joint showed a fracture of the tip of the lateral malleolus but the ankle mortise was intact. The patient was treated with a below-knee cast for 6 weeks, and weight bearing was allowed. When the cast was removed there was minimal residual ankle tenderness on the lateral and medial malleolar areas. On testing the ankle inversion, there was a positive apprehension for ankle subluxation and severe tenderness over the anterior talofibular ligament. He was given an elastic support and referred for physiotherapy.
Twelve weeks after the injury he was complaining of pain around the lateral malleolus. He was not able to return to work, which involved carrying heavy objects. However, he had a good range of movement of the ankle except for a restriction of ankle joint dorsiflexion. Radiographs showed persistence of the lateral malleolus fracture in good position. He was encouraged to return to normal activities. At follow-up evaluation 16 weeks after the injury, there was a lack of significant clinical improvement and symptoms of recurrent ankle sprains on walking were related. Suspicion about the progress of bony union arose and there were no clinical or radiologic signs of healing of the lateral malleolous fracture (Fig. 1).
Fig. 1.
Anteroposterior radiograph of the ankle joint taken 4 months after injury, showing nonunion of the tip of the lateral malleolar fracture.
Fig. 2.
T2 magnetic resonance image scan of the ankle confirming that the lateral malleolar tip fracture is related to the malleolus. Note the lack of interposed tissue between the fibula and the free fragment.
Through a lateral incision, the distal fibula was exposed. The proximal surface of the un-united fragment was observed to have no cartilaginous or cortical border, confirming the nonunion. The calcaneofibular ligament was found to be attached to the tip of the fragment, and seemed to exert tension on the distal fragment. Although partially disrupted, some fibers of the anterior talofibular ligament were attached to the lateral malleolus proximal to the nonunion. The posterior talofibular ligament was intact.
The nonunion was debrided accordingly and grafted using an ipsilateral lateral malleolar bone graft. Fixation consisting of 2 parallel Kirschner wires passed across the plane of the fracture from front to back were applied. A figure-of-8 tension band fixation using number-2 polyester suture was applied. The soft-tissue attachments to the lateral malleolus were preserved. The ankle was immobilized for 6 weeks in a below-knee cast and weight bearing was avoided. Partial weight bearing was then allowed. Ten weeks after surgery, the patient was able to bear weight without pain or instability. He was able to go back to work 4 months after surgery and perform sports activities 5 months postoperatively. A radiograph of the ankle at that time showed signs of a healed fracture (Fig. 3).
Fig. 3.
Mortise radiograph of the ankle joint 3 months after surgery showing that the fracture has healed.
Discussion
Accessory ossicles at the tip of the lateral malleolus are a differential diagnosis after an injury to this area. The incidence of ossicle or os subfibulare is 1% compared with an incidence of 20% in relation to the medial malleolus (2). There has been considerable debate as to whether these represent secondary ossification centers, traction apophyses, areas of ischemic necrosis, pseudepiphyses, or accessory ossicles 2, 3. However, there is no disagreement that acutely symptomatic lesions should be treated as fractures 2, 3. The main complaint of our patient was pain and recurrent ankle sprains The recurrent ankle sprain experienced after nonunion of the tip of the lateral malleolus most likely was caused by loss of stability of the attachment of the intact calcaneofibular ligament and the partially attenuated anterior talofibular ligaments (4). This patient had no previous problems with the ankle, and there was no evidence of a false joint in-between the fragments on surgical exploration. We therefore assume that the lesion was a fracture of the tip of the lateral malleolus and not an accessory ossicle.
Sneppen states that pseudoarthrosis of the lateral malleolus does not influence the long-term prognosis of ankle fracture (5).
Although there are few reports of nonunion of the lateral malleolus, there is increased incidence in male patients, after supination and high lateral malleolus fractures, comminuted fracture patterns, and after primary internal fixation 6, 7. Also, malrotation of the distal end of the fibular fragment has been reported as a cause of nonunion (8).
Siliski et al. suggested open reduction and plating as the treatment of choice (7). The small size of the distal fragment may make fixation difficult with compression screws. Tension band wiring technique was used in our case because of the small size of the fragment. Polyester was used instead of flexible wires to avoid skin irritation of subcutaneous wires.
Although it is suggested by some investigators that the excision of the tip of the lateral malleolar fracture is a surgical option for nonunion 4, 9, we do not agree with this. Anatomic reduction and internal fixation provide more accurate ligamentous reconstruction and stability than excision of the nonunited fragment. Proximal advancement of the ligamentous tissue after excision of the fragment may alter ligamentous tension and affect normal mechanics of the ankle.
References
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© 2003 American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.
