Patellar fractures may be difficult to treat. The surgeon will often underestimate the complexity of the injury and will therefore not be prepared for a very challenging osteosynthesis. The articular injury is usually much more severe than predicted from the radiographs. In addition, multiple small articular fragments may be difficult to bring together. Patellar fractures are important for two reasons:
- they generally disrupt the extensor mechanism and
- they may be associated with a significant articular injury to the patellofemoral joint
Clinical examination: straight leg raise test
Injury to the patella may disrupt the extensor apparatus of the knee and the patient may be unable to perform an active straight leg raise. Untreated, displaced patellar fractures may lead to marked difficulty with normal gait. If there is clinical uncertainly about the correct diagnosis of disruption of the extensor apparatus of the knee, an ultrasound scan, or MRI, of the extensor apparatus, including the quadriceps tendon and patellar tendon should be obtained, in order to elucidate the correct diagnosis.
Complete articular, frontal/coronal, wedge fracture (AO/OTA 34C2)
These fractures may be due to direct blow to the knee, such as a dashboard injury, or to a hyperflexion injury. These are classified by AO/OTA as 34C2.
They may need a combination of fixation techniques, such as screw fixation with tension band wiring.
The patellofemoral joint surface may be injured, associated with impaction deformation of the patellar joint surface that can be difficult to restore anatomically and stably.