Current concepts review: Fractures of the patella

Abstract

Fractures of the patella account for about 1% of all skeletal injuries and can lead to profound impairment due to its crucial function in the extensor mechanism of the knee. Diagnosis is based on the injury mechanism, physical examination and radiological findings. While the clinical diagnosis is often distinct, there are numerous treatment options available. The type of treatment as well as the optimum timing of surgical intervention depends on the underlying fracture type, the associated soft tissue damage, patient factors (i.e. age, bone quality, activity level and compliance) and the stability of the extensor mechanism. Regardless of the treatment method an early rehabilitation is recommended in order to avoid contractures of the knee joint capsule and cartilage degeneration. For non-displaced and dislocated non-comminuted transverse patellar fractures (2-part) modified anterior tension band wiring is the treatment of choice and can be combined - due to its biomechanical superiority - with cannulated screw fixation. In severe comminuted fractures, open reduction and fixation with small fragment screws or new angular stable plates for anatomic restoration of the retropatellar surface and extension mechanism results in best outcome. Additional circular cerclage wiring using either typical metal cerclage wires or resorbable PDS/non-resorbable FiberWires increases fixation stability and decreases risk for re-dislocation. Distal avulsion fractures should be fixed with small fragment screws and should be protected by a transtibial McLaughlin cerclage. Partial or complete patellectomy should be regarded only as a very rare salvage operation due to its severe functional impairment.

Keywords: biomechanics; conservative treatment; patellar fracture; patellectomy; tension band.

Figure 1. Classifications of patellar fractures according to the AO/ASIF, reprinted with permission of the AO Foundation

Copyright by AO Foundation, Switzerland

Figure 2. Non-displaced fracture of the proximal patellar pole, which might be suitable for conservative treatment. Notably, these cases should be tested up to 60° of flexion under image intensifier control in order to confirm a stable fracture pattern.

Figure 3. Preoperative X-rays of a comminuted patella fracture (above). 3 months post-surgery using a combination out of K-wires, screws, and an eight-shaped cerclage wiring (below).

Figure 4. Preoperative X-rays of a comminuted patella fracture (above). 3 months post-surgery using screw fixation and modified tension band (below).

Figure 5. Preoperative X-rays of a non-comminuted transverse patella fracture (above). 3 months post-surgery using percutaneous screw fixation (below).

Figure 6. Preoperative X-rays of a transverse patella fracture (above). Loss of reduction with screw pullout 3 month after surgery (middle). 3 months after revision surgery with screw fixation and additional modified tension band (below).