Session IV - Foot & Ankle

*Stress Examination of SE-Type Fibular Fractures

Paul Tornetta, III, MD; Timothy McConnell, MD; William R. Creevy, MD; Boston University Medical Center, Boston, MA (all authors ­ a-Aircast Foundation)

Introduction: Isolated SE-type fibular fractures are one of the most common fractures seen by the orthopaedist. If the deltoid ligament is intact, then the mortise is stable and the fracture may be treated nonoperatively (SE2 fractures). However, if the deltoid is disrupted, operative management is recommended to maintain stability of the mortise during healing (SE4 fractures). A history of dislocation or findings of a widened medial clear space or subluxation of the talus on the initial radiographs confirms a medial injury (SE4 pattern). However, many patients with isolated fibular fractures have radiographs that demonstrate a normal medial clear space and no talar subluxation. In this situation, it is unknown whether the deltoid ligament is intact. Medial tenderness and swelling are often cited as an operative indication; likewise, lack of these findings may lead to nonoperative management. To our knowledge, neither tenderness nor swelling has been proven to predict deltoid injury. The purpose of this study was to prospectively evaluate a method of stress testing in the emergency room to differentiate SE2 from SE4 patterns and to determine whether medial tenderness or swelling correlates with deltoid instability.

Methods: Over a 32-month period 138 skeletally mature patients with acute Weber B fractures of the lateral malleolus that fit the criteria of supination-eversion as described by Lauge-Hansen (1954) were included in this prospective study. We evaluated injury mechanism, associated injuries, soft tissue swelling, and ecchymosis of both sides of the ankle (graded as none, moderate, or severe). A visual analog pain scale was used to evaluate tenderness at nine locations about the ankle. Standard AP, lateral, and mortise radiographs were made of all fractures. Patients with fibula fractures and a reduced mortise underwent a stress radiograph at the time of presentation. This radiograph was made with the leg stabilized in 15 degrees of internal rotation and neutral dorsiflexion to obtain a mortise view while an external rotation force of approximately 8 lb (3.6 kg) was applied to the ankle. On the basis of the work of Pankovich, a positive stress radiograph indicating deltoid incompetence was defined as medial joint space widening of more than 4 mm and less than 1 mm more than the superior space, or any talar subluxation. Ankles with a negative stress radiograph (medial clear space < 4 mm) were defined as "SE2" patterns, and these patients were treated nonoperatively with an Aircast stirrup brace, with weightbearing as tolerated. Those patients who were found to have a positive stress radiograph were diagnosed with "stress (+) SE4" patterns and treated with open reduction and internal fixation. Fractures with a wide medial clear space and talar subluxation initially were termed "displaced SE4" fractures, not stressed, and treated with open reduction and internal fixation. A single author then measured the following radiographic parameters: syndesmotic distance, medial clear space, superior clear space, lateral clear space, height of the fibular fracture, and fibular displacement. Comparisons were made between the groups as defined by the stress examination: SE2 fractures, stress (+) SE4 fractures, and displaced SE4 fractures (presenting with a wide clear space and not requiring a stress radiograph).

Results: Of 138 SE-type fibula fractures, 97 patients presented with an isolated fibular fracture and a reduced mortise. Sixty-one (63%) patients had a negative stress radiograph, were diagnosed as SE2 fractures, and were allowed to bear weight as tolerated in an Aircast stirrup splint. Thirty-six fractures were found to be unstable, stress (+) SE4 and treated operatively. Six examinations were not diagnostic (of poor quality or malrotated) and were repeated in the operating room. Fifty of the 61 SE2 ankles were followed to union. All healed without widening of the medial clear space or talar subluxation, confirming their stability. In comparing the radiographic measurements on the initial presentation films of the SE2, displaced SE4, and stress (+) SE4 ankles, there were significant differences found in several of the measured parameters; however, the differences were not helpful in decision making. For example, the medial clear space on the AP radiograph of the SE2 vs. the stress (+) SE4 fractures was 3.3 mm vs. 3.7 mm (P = 0.01). All measurements were £ 4 mm, so this information did not help to differentiate the injuries at the time of presentation. Severe medial tenderness was reported by 24% of the patients with SE2 injuries as compared with 37% of those with stress (+) SE4 injuries. Conversely, 50% of the patients with stress (+) SE4 injuries and 31% of displaced SE4 injuries had only minimal tenderness medially. Medial soft tissue swelling was present in 24% of SE2, 37% of stress (+) SE4, and 56% of displaced SE4 fractures.

Discussion: We examined the efficacy of a radiographic stress examination to differentiate SE2- from SE4-type ankle fractures of patients with an isolated fibular fracture and a reduced mortise. A negative stress examination (< 4 mm medial clear space and no talar subluxation) was predictive of a stable ankle that could be treated with full weightbearing in a functional brace and that would heal without displacement. Medial tenderness did not predict deltoid incompetence or the need for a surgical procedure. Likewise, lack of medial tenderness did not confirm a stable ankle. There were statistical differences in the radiographic parameters between the groups on the initial presentation radiographs, but the magnitude of these differences was small and not helpful in decision making.

Conclusion: A stress examination under local anesthesia is a useful clinical examination for predicting the ability to treat isolated fibular fractures functionally and without a surgical procedure. The presence or absence of medial tenderness and swelling does not correlate with deltoid injury and cannot be used to determine the type of treatment required.