Segond Fracture

Etiology

Segond fractures are usually caused by a forced mechanism of internal rotation with varus stress to the knee. It was first described by Paul Segond in his published works in 1879, following a cadaveric study of knee injuries.[2] This has later been correlated with ACL ruptures via the invention of more advanced imaging techniques. Segond also described a fibrous band at the point of the avulsion injury that has been defined as the anterolateral ligament.[4] More recent MRI studies however have been unable to identify any distinct ligamentous attachments associated with the anterolateral ligament, but do show evidence of posterior capsule and iliotibial band fibers attaching to the Segond fragment. These findings however are controversial.[5]

Epidemiology

Segond fractures have a high association with ACL ruptures, being present in 75% to 100% of cases. Conversely, 9-12% of ACL ruptures have an associated Segond fracture.[6][7]

ACL ruptures are a common orthopedic injury with an annual incidence of 68.6 per 100 000 people per year in the United States.[8] Incidence is slightly higher in male patients, with a peak incidence occurring later in men than in women - occurring in men aged 19-25 years of age with an incidence of 0.00241 and in women aged 14-18 with an incidence of 0.002276.

History and Physical

As Segond fractures have such a strong correlation with ACL ruptures, it is of no surprise that their history and mechanism of injury are also the same. Patients commonly describe a ‘pop’ following a twisting mechanism. They generally have an associated discomfort, swelling, decreased range of motion at the knee, and difficulty mobilizing.

There is no specific physical test for a Segond fracture, as they are generally noted on radiographs of the knee. However, as Segond fractures are often pathognomonic of ACL ruptures, testing for an intact ACL is imperative. Lachmann's test is the most sensitive physical examination maneuver in assessing for ACL tears, but there is also utility in the anterior drawer test. Integrity of all other ligaments of the knee should be assessed as well, including posterior drawer, varus/valgus stress testing, and pivot shift testing.

Evaluation

A Segond fracture can normally be diagnosed with a plain radiograph. A bony fragment (avulsion fracture) is seen in the anteroposterior view of the knee on the lateral aspect of the proximal tibia.

As previously discussed, with likely underlying ligamentous and or meniscal injuries, magnetic resonance imaging (MRI) is necessary for further evaluation, which may also highlight the more subtle Segond fractures.

Computed tomography is not usually used in the diagnosis of Segond fractures. While there is a much higher sensitivity for diagnosing fractures with CT Scan, MRI is the imaging modality of choice to identify the specific associated ligamentous injuries in the knees.

Treatment / Management

Initial treatment should be supportive. This includes resting the affected knee, elevating it whenever possible, simple analgesia, and icing the knee. Patients are highly likely to require walking aids, such as crutches. Having a knee brace early can also help support the knee before the consideration of surgery.

Surgical intervention is directed at underlying injuries rather than the Segond fracture itself. There is no evidence that Segond fractures need to be fixed. Furthermore, evidence suggests that ACL reconstructions are not at greater risk of failure with the presence of a Segond fracture.[9] While Segond fractures suggest higher instability associated with ligamentous knee injuries pre-operatively, the post-operative comparison suggests no difference in tested stability after the ligamentous injury is addressed.[10]

Direct repair of Segond fractures by repairing the anterolateral ligament is an option, as some suggest that it may restore rotational stability to the knee. Segond fractures can be repaired by either direct suture repair, suture anchor techniques, or screw fixation dependant on the size and characteristics of the fracture. Surgical repair of Segond fractures has shown good results with minimal complications, however, these were not compared to a control group.[2] 

All surgical interventions should be undertaken following shared decision making with the patient and following informed consent. The decision to proceed with surgery is often largely swayed by the patient’s co-morbidities, activity levels, the patient’s expectations, and their likelihood of a favorable outcome.

Regardless of whether a patient elects for operative versus non-operative management, all patients need some form of rehabilitation from an interprofessional team approach. They will need to see a therapist for rehabilitation and may benefit from bracing to add stability and comfort to the knee.[11]

Differential Diagnosis

"Arcuate sign" is an avulsion fracture of the fibular head and is frequently mistaken for a Segond fracture on radiographs. The arcuate ligament complex or the posterolateral ligaments may avulse from the fibular head during a traumatic deformity to the knee. Like Segond fractures, this finding is pathognomonic for ligamentous knee injury and instability and should be investigated in a similar fashion. There are, however, subtle differences on plain radiographs, as an arcuate avulsion is normally more horizontal, lateral, and posterior than would be seen in a true Segond fracture.

Prognosis

The prognosis for a Segond fracture itself is good. As previously discussed, there has not been shown to be any benefit to fixing this fracture. Furthermore, the presence of Segond fractures do not appear to represent a higher risk of requiring revision surgery.[11] The main concern with regards to prognosis is appropriately addressing the associated ligamentous injuries in the knee. If addressed appropriately, patients will generally have a favorable outcome. Any alteration of the mechanics of the knee often leads to an increased risk of osteoarthritis (OA). It is well known that an ACL rupture leads to OA in a high proportion of patients. Unfortunately, ACL reconstruction has not been shown to completely reduce the risk of developing OA but has been shown to reduce its prevalence.[12]

Complications

The most common short-term complications from a Segond fracture are ongoing pain and stiffness. If the patient undergoes an ACL reconstruction, additional short to mid-term complications exist associated with the surgical procedure. Generally, however, ACL reconstruction is considered a safe procedure, with a 0.75% risk of a wound complication. Although thromboprophylaxis for ACL reconstruction is felt to be unnecessary, one paper has quoted deep vein thrombosis levels at 0.30% and pulmonary embolism levels at 0.18%.[13] The topic of thromboprophylaxis after ligamentous repair of the knee is controversial, and the decision to provide anticoagulation postoperatively should be made on a case by case basis by the surgeon considering each patient's specific medical comorbidities.