To review, the patient is a 33 year-old male presenting with right ankle pain after a fall from scaffolding, with absent dorsalis pedis pulses in the injured extremity.
Questions and Answers:
1) What is this patient's injury/fracture pattern?
This patient has an obvious fracture of the fibula at the level of the syndesmosis without other apparent fractures. Ankle fractures have several different classification schema that could be used to describe and categorize this injury, two of which are most applicable: the anatomic, and the Danis-Weber.
The anatomic classification is easily diagnosed using radiographs and does not change depending on ligament instability. Using this classification schema, the above patient has an isolated lateral malleolar fracture.
The Danis-Weber classifications can be used to more specifically describe isolated lateral malleolar fractures. Type A Danis-Weber (Weber A) fractures are fractures in which the medial aspect of the fracture line lies inferior to the syndesmosis between talus and tibia. In Weber B fractures the fracture lies adjacent to the syndesmosis, and in Weber C fractures the fracture lies proximal to the syndesmosis. The above patient has a minimally-displaced Weber B fracture of the distal fibula.
2) What is the next step in evaluation?
This patient has absent dorsalis pedis pulses in the right foot, which requires further consideration, as absent pulses, dusky foot, or tented skin are indications for emergent reduction of fracture/dislocations. However, this patient does not have an apparent dislocation on radiograph and otherwise has good capillary refill.
Approximately 1.8% of patients have bilateral congenitally absent dorsalis pedis pulses. An additional 1% of patients have unilateral congenitally absent dorsalis pedis pulses. The posterior tibial pulse is absent in <0.2% of patients. This patient, with no evidence of radiographic dislocation and intact capillary refill, is likely one of these patients and his fracture should therefore not be manipulated.
In orthopedic evaluation, the determination of stability has important implications for outpatient management and referral processes. The stability of isolated malleolar fractures depends on the location of the fibular fracture. Weber A fractures are considered stable and need no further emergent evaluation. Weber C fractures are considered unstable and require no further emergent evaluation. Weber B fractures, however, can be either unstable or stable depending on associated ligamentous injury.
Approximately 50% of patients with Weber B fractures also have deltoid ligament tears which results in medial ankle instability and therefore an unstable ankle. Classically, the stability of the deltoid ligament has been assessed with gravity stress views of the ankle. In these views, the foot hangs off the edge of the bed, lateral sided down, and mortise view radiographs are taken. The ankle is determined to be unstable if the mortise increases to over 4 millimeters in gravity stress views.
These images can be time-consuming to take and painful for the patient, and recent research shows that we no longer have to do gravity stress views to determine stability in patients with Weber B fractures. In a new Finnish Study, The standard AP, lateral, and mortise radiographs for 300 patients with isolated lateral malleolus fractures were examined for features that might predict deltoid ligament injury. The patients had Weber B fractures and mortise < 4mm on mortise view radiograph.
The two features most closely associated with stable ankles were:
1) only two fracture segments, and
2) less than 2 mm of posterior displacement (diastasis) of the distal fracture segment on lateral radiographs.
In patients with both of these features, the ankle is very likely (94-98%) to be stable. Our patient, with only two fracture segments and less than 2 mm of posterior diastasis, can be safely diagnosed with a stable ankle fracture and needs no further emergency department evaluation.
3) What is the next step in management?
Patients with stable ankle fractures such as the above patient can be instructed to bear weight as tolerated, and placed in a walking boot or walking cast. They should be instructed to follow-up with orthopedics in 1-2 weeks for further assessment of healing and stability and will likely not need to proceed to operative repair.
Radiographs for the case courtesy of Dr Alborz Jahangiri, Radiopaedia.org, rID: 46843
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Schock HJ, et al. The use of gravity or manual-stress radiographs in the assessment of supination-external rotation fractures of the ankle. J Bone Joint Surg Br. 2007 Aug;89(8):1055-9.
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