Diagnosis

Complete articular, frontal/coronal fracture (AO/OTA 34C1)

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General considerations
Patellar fractures are some of the most difficult fractures 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:

  1. they generally disrupt the extensor mechanism and
  2. they are 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 fracture (AO/OTA 34C1)
These fractures are characterized by a transverse fracture with complete disruption of the extensor apparatus of the knee. These are classified by AO/OTA as 34C1. All displaced complete articular fractures should be fixed surgically.

These fractures may be due to a hyperflexion injury, with a sudden quadriceps contraction when the knee is flexed.

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.

Options
1.  Complete articular, frontal/coronal simple fracture of the middle third (AO/OTA 34C1.1)
2.  Complete articular, frontal/coronal simple fracture of the proximal third (AO/OTA 34C1.2)
3.  Complete articular, frontal/coronal simple fracture of the distal third (AO/OTA 34C1.3)

1.  Complete articular, frontal/coronal simple fracture of the middle third (AO/OTA 34C1.1)

When the fracture occurs through the middle third of the patella, it is classified by AO/OTA as 34C1.1.

2.  Complete articular, frontal/coronal simple fracture of the proximal third (AO/OTA 34C1.2)

When the fracture occurs through the proximal third of the patella, it is classified by AO/OTA as 34C1.2.

X-ray by courtesy of Spital Davos, Switzerland, Dr C Ryf and Dr A Leumann.

3.  Complete articular, frontal/coronal simple fracture of the distal third (AO/OTA 34C1.3)

When the fracture occurs through the distal third of the patella, it is classified by AO/OTA as 34C1.3.

X-ray by courtesy of Spital Davos, Switzerland, Dr C Ryf and Dr A Leumann.