Diagnosis

Partial articular, lateral sagittal fracture (AO/OTA 34B1)

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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.

 

Partial articular, sagittal fracture on the lateral side
Partial articular, sagittal fractures of the patella may be due to direct impact to the front of the knee (eg, dashboard injury).

These are classified by AO/OTA as 34B1.

The surgeon must not confuse a well-corticated superolateral bipartite patella with an acute fracture.

Options
1.  Partial articular, lateral sagittal simple fracture (AO/OTA 34B1.1)
2.  Partial articular, lateral sagittal fragmentary fracture (AO/OTA 34B1.2)

1.  Partial articular, lateral sagittal simple fracture (AO/OTA 34B1.1)

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

2.  Partial articular, lateral sagittal fragmentary fracture (AO/OTA 34B1.2)

These fracture types may be technically challenging to fix. Occasionally smaller fracture fragments if significantly displaced may be excised. If it is found that primary fixation is not possible then either a primary salvage procedure, or partial patellectomy, may need to be performed.

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