Clinical History
A man presented with a painful tender swelling over the left proximal fibula following a road traffic accident where his motorcycle landed on his left leg.
Imaging Findings
A man was brought to the accident and emergency department following a road traffic accident. He was riding his motorcycle at 70mph when he was hit from behind by a car. He fell to his left side with the motorcycle landing on his left leg. He was unable to weight bear complaining of pain only in his left leg. Examination of the left knee revealed a tender swelling over the lateral aspect in the region of the fibula head. There were some abrasions to the medial aspect of the lower leg. He was able to flex his knee from 20-70º with pain but there was no knee effusion. The ligaments were intact on examination but there was pain on varus and valgus stressing. Hip and ankle examination was normal. The patella was non-tender and without demonstrated apprehension sign. There was no distal neuro-vascular deficit initially.
The following morning a closed reduction was performed under general anesthesia. Pre operative examination revealed paraesthesia in the first web space, no motor weakness of extensor hallus longus or ankle dorsiflexion. Reduction was achieved by direct postero-medial pressure on the prominent fibular head with the knee flexed to 90º. An audible "snap" was heard on reduction. Examination following reduction revealed full range of knee motion without instability on varus or valgus stressing, negative drawers and Lachmans tests. Post-reduction radiographs were taken and his knee was immobilized in a Raymed splint postoperatively. He self-discharged himself from hospital the same evening.
He attended clinic two weeks later complaining about decreased sensation over the lateral aspect of his lower leg. Examination revealed paraesthesia over the L4-L5 dermatome, the proximal tibio-fibular joint was shown to be in a satisfactory position on radiographs. He was able to flex his knee from 0-90º and was referred to the physiotherapist. His knee flexion improved to 0-100º over the next two weeks with gradual improvement in sensation along L4-L5 distribution. The sensation resolved five months following the injury with a full range of knee flexion.
Discussion
Isolated proximal tibiofibular joint dislocations are rare events but they have been described following many sporting injuries. The anterolateral type is the most common with rarer posteromedial and superior dislocations. They can often be difficult to diagnose as standard radiographic findings can be subtle, in one series the diagnosis was delayed in 60% of cases. Therefore a high index of suspicion is required during initial examination and when viewing the x-rays.
Three radiographic signs have been described for recognizing anterolateral dislocation:
1) lateral fibular displacement on the AP view,
2) proximal interosseous space widening, and
3) anterior fibular head displacement (increased overlap) on the lateral view.
Radiograph of the knee in 45-60º of internal rotation gives a better view of the articular space. If there is any doubt about a proximal tibiofibular joint dislocation or any associated fractures a CT scan maybe useful.
Early diagnosis and reduction of an isolated proximal fibular dislocation is important to minimize peroneal nerve injury and to avoid chronic dislocation/subluxation which can cause local pain with activity. Closed reduction is usually acheived under GA but if delayed may occassionally require open reduction with internal fixation with K-wires. There are very few studies with long-term follow up but persistent pain may be relieved by resection of the fibular head.
Differential Diagnosis List
An isolated anterolateral dislocation of the left proximal tibiofibular joint
Final Diagnosis
An isolated anterolateral dislocation of the left proximal tibiofibular joint
