August 23, 2020
fibular fractures review cover

A Review of Distal Fibula Fractures

Isolated distal fibula fractures account for up to 55-65% of all ankle fractures (4). There are many different classifications used for these fractures. For the purpose of this review, we will use the Danis-Weber criteria for lateral fibula fractures. The Weber criteria relates the position of the distal fibula fracture to the syndesmosis (4). The other criteria commonly used is the Lauge-Hansen classification. This criteria is based upon the position of the foot at the time of the injury, which is typically in a supination-external rotation position (4).
weber classification distal fibular fracture

Image 1. Weber classification of distal fibular fractures (courtesy of faculty.washington.edu)

In order to discuss treatment of these fractures, it is important to understand the anatomy of the ankle joint. Outside of the bones, which include the talus, medial malleolus, lateral malleolus, and tibia plafond, there are three ligamentous groups that provide support to the ankle (4). The medial ankle is supported by the deltoid ligament (4). The lateral ankle is supported by the anterior talofibular, calcaneofibular, and posterior talofibular ligaments (4). There is also the syndesmosis which connects the distal tibia and fibula. The syndesmosis includes the interosseous ligament, anterior inferior tibiofibular ligament, inferior transverse ligament, and posterior inferior tibiofibular ligament (4).

Weber A

A Weber A fracture typically occurs during an inversion ankle injury (2). Weber A fractures occur below the syndesmosis (4). These fractures are typically associated with a stable ankle joint. Diagnosis is typically made with standard weight bearing radiographs of the ankle. Treatment is typically non-operative with a period of time in a short leg non-weight-bearing immobilization (2). As pain improves, a patient can be advanced to weight bearing and there should also be a focus on early range of motion activities (4).

Weber B

A Weber B fracture occurs due to a rotational injury with the development of an oblique fracture line starting at the tibia plafond (3). These are also called Lauge-Hansen supination-external rotation stage 2 fractures (8). The challenge with these fractures is determining which Weber B fractures are stable. The deep portion of the deltoid ligament prevents external rotation of the talus (10). Typically, if there is tearing of the deep portion of the deltoid ligament, there can be lateral talar shift or talar tilting (3,4). Medial sided tenderness on physical exam cannot be used as an accurate predictor of deltoid ligament tearing (7).
Radiographs need to be done to evaluate the stability of the ankle mortise. Gravity stress tests can be done to evaluate for deltoid ligament injury. A study in Foot Clinics International looked at the role of weight bearing xrays in determining ankle stability (9). They identified a group of patients who had positive stress xrays in the setting of a distal fibula fracture (9). They found that medial clear space on their weightbearing radiographs was on average 2.9mm (9). They only identified three patients who had a widened medial clear space that required surgical fixation (9). The other 35 patients were treated non operatively and had good outcomes (9). The success of the patients with a normal weight bearing radiograph but positive stress views support the use of weight bearing radiographs as a quick and inexpensive screening test for ankle stability (9).
weber classification distal fibular fracture xray

Image 2. Weber classification demonstrated on xray (courtesy of BMJ)

The medial clear space is measured from “the superior-medial aspect of the talus to the superior-medial corner of the plafond on the mortise” (7). Providers use a medial clear space measurement greater than 4mm or 5mm as a threshold for determining ankle stability (3).

Researchers have also looked at using MRI to evaluate the deltoid ligament to assess for ankle instability. In a study of fifty patients with a distal fibula fracture, an MRI identified multiple deltoid ligament findings. They identified edema within the deltoid ligament, partial tearing, and full thickness tearing of the anterior and posterior deep portion of the deltoid ligament (10). The study found that no patients with a medial clear space <5 mm had a tear of the posterior deep deltoid ligament. This helps support the role of weight bearing radiographs in assessing stability of the ankle. 

Initial treatment involves the use of a cast or fracture boot (3). The patient’s pain can help dictate weight bearing status. Initial indications for surgical evaluation is a laterally translated talus on radiographs or medial malleolus and lateral malleolus fracture (4)

Weber C

A Weber C fracture occurs above the level of the syndesmosis (1). The mechanism of injury typically occurs when the foot is pronated and externally rotated (1). Rupture of the deltoid ligament allows for external rotation of the talus that permits a shift in the contact pressure of the talus (6). This contact can predispose patients to develop articular cartilage damage (6).
These fractures are typically managed surgically as they can be unstable (1). Physicians must assess for tibia-talar joint congruity, fracture of the medial malleolus, and evaluate for deltoid tear when evaluating for joint stability (1).

Conclusion

For nonsurgical clinical assessment, ankle stability is the biggest challenge when seeing a patient with a distal fibula fracture. Research shows that weight bearing radiographs can be used to assess the medial clear space when evaluating for ankle stability. Those patients with medial clear space widening less than 5mm typically do well with non-operative measures.

ReferenceS

1) Rye Y., et al. “Functional Outcomes Following Operative and Nonoperative Management of Weber C Ankle Fractures: A Systematic Review.” The Journal of Foot and Ankle Surgery: Official Publication of the American College of Foot and Ankle Surgeons, vol. 59, no. 1, Feb. 2020, pp. 105–11. PubMed, doi:10.1053/j.jfas.2019.06.005.
2) Mandi, Denise M. “Ankle Fractures.” Clinics in Podiatric Medicine and Surgery, vol. 29, no. 2, Apr. 2012, pp. 155–86, vii. PubMed, doi:10.1016/j.cpm.2012.01.002.
3) Holmes, James R., et al. “A Novel Algorithm for Isolated Weber B Ankle Fractures: A Retrospective Review of 51 Nonsurgically Treated Patients.” The Journal of the American Academy of Orthopaedic Surgeons, vol. 24, no. 9, Sept. 2016, pp. 645–52. PubMed, doi:10.5435/JAAOS-D-16-00085.
4) Aiyer, Amiethab A., et al. “Management of Isolated Lateral Malleolus Fractures.” The Journal of the American Academy of Orthopaedic Surgeons, vol. 27, no. 2, Jan. 2019, pp. 50–59. PubMed, doi:10.5435/JAAOS-D-17-00417.
5) Norkus, Susan A., and R. T. Floyd. “The Anatomy and Mechanisms of Syndesmotic Ankle Sprains.” Journal of Athletic Training, vol. 36, no. 1, 2001, pp. 68–73.
6) Hunt, Kenneth J., et al. “Ankle Joint Contact Loads and Displacement With Progressive Syndesmotic Injury.” Foot & Ankle International, vol. 36, no. 9, Sept. 2015, pp. 1095–103. PubMed, doi:10.1177/1071100715583456.
7) DeAngelis, Nicola A., et al. “Does Medial Tenderness Predict Deep Deltoid Ligament Incompetence in Supination-External Rotation Type Ankle Fractures?” Journal of Orthopaedic Trauma, vol. 21, no. 4, Apr. 2007, pp. 244–47. PubMed, doi:10.1097/BOT.0b013e3180413835.
8) Tartaglione, Jason P., et al. “Classifications in Brief: Lauge-Hansen Classification of Ankle Fractures.” Clinical Orthopaedics and Related Research, vol. 473, no. 10, Oct. 2015, pp. 3323–28. PubMed Central, doi:10.1007/s11999-015-4306-x.
9) Hoshino, C. Max, et al. “Correlation of Weightbearing Radiographs and Stability of Stress Positive Ankle Fractures.” Foot & Ankle International, vol. 33, no. 2, Feb. 2012, pp. 92–98. PubMed, doi:10.3113/FAI.2012.0092.
10) Nortunen, Simo, et al. “Stability Assessment of the Ankle Mortise in Supination-External Rotation-Type Ankle Fractures: Lack of Additional Diagnostic Value of MRI.” The Journal of Bone and Joint Surgery. American Volume, vol. 96, no. 22, Nov. 2014, pp. 1855–62. PubMed, doi:10.2106/JBJS.M.01533.