Tibial spine avulsion fracture

AP (image 1) and lateral (image 2) radiographs of the knee show an avulsion fracture (arrow) of the medial tibial spine. This injury is an avulsion fracture of the anterior cruciate ligament insertion. Tibial spine avulsion fractures occur in children due to the greater tensile strength of the ligament compared to the underlying bone. Often, other internal derangement injuries are present.

Similar cases

Sagittal proton density weighted image shows an avulsion fracture of the posterior tibia epiphysis (arrow) and a moderate joint effusion with hemarthrosis (arrowhead). The posterior cruciate ligament is attached to the avulsed fragment. Posterior cruciate ligament avulsion fractures are uncommon. However, if a bone fragment is seen along the posterior tibial plateau, a PCL avulsion should be considered to be present. The posterior cruciate ligament provides stabilization to the knee and resists excessive posterior translation of the tibia.

Sagittal T2-W MRI shows the avulsion fracture (arrow) of the tibial spine and a large lipohemarthrosis (arrowhead). The lipohemarthrosis causes a parfait effect with blood layering most dependently (furthest from the arrowhead), effusion fluid in the middle, and fat floating on top. Tibial spine avulsion fractures are associated with anterior cruciate ligament (ACL) injuries. The ACL originates from the medial and anterior aspect of the tibial plateau and inserts on the lateral femoral condyle. Children are more likely to have tibial spine avulsions than an ACL rupture because the bone is weaker than the ligament.

Coronal (image 1), sagittal (image 2), and 3D reformatted (image 3) CT along with sagittal proton density MRI (image 4) highlight multiple injuries: an avulsion fracture (dashed arrow) of the lateral tibia epiphysis, an avulsion fracture of the tibial spine (arrow), and a large hemarthrosis (arrowhead). Both the fracture of the lateral tibia epiphysis and the tibial spine avulsion fracture are associated with ACL (orange arrow) rupture. The fracture of the lateral tibia epiphysis is termed a Segond fracture. In the majority of instances, Segond fractures are associated with ACL disruption. They occur as a result of internal rotation and varus stress. When the finding is made on radiograph, an MRI is typically indicated to assess for internal derangement of the knee. CT is not typically indicated. In this case, due to the extent of injury, CT was used to assess for loose bodies within the knee. The intact PCL (pink arrow) highlighted for comparison.

AP and lateral radiographs of the knee show a small avulsion fragment along the lateral aspect of the tibial epiphysis and a large knee effusion. This type of fracture represents an avulsion of the lateral collateral ligament and is known as a Segond fracture. It is important to recognize as it is almost always associated with an ACL injury.