IS Case 141: Patella Fracture
Imaging Sciences URMC 2008
Publication Date: 2009-05-21
Patient is a 21-year-old female who underwent revision of left knee anterior cruciate ligament reconstruction utilizing a right knee patellar tendon graft. Postoperatively patient sat up and felt a pop in her right knee.
Three views of the right knee demonstrate a displaced inferomedial patella fracture with a large joint effusion.
Fractures of the patella may result from direct trauma to the anterior aspect of the knee or from tension forces produced by the quadriceps tendon. Patella fractures represent 1% of all skeletal injuries. In general there are three types of patella fractures: longitudinal (vertical), transverse and comminuted. Patella fractures can be further classified by the system proposed by Hohl and Larson. This system describes six fracture types. They are longitudinal (vertical), nondisplaced transverse, displaced transverse, nondisplaced comminuted (stellate), displaced comminuted and avulsed superior margin. The most common type is the transverse type, seen in 60% of cases.
When evaluating patella fracture, it is important to rule out bipartitie or multipartite patella. These entities are developmental variants of the accessory ossification center or centers of the superolateral margin of the patella. The individual bones of a bipartite or multipartite patella do not fit together in contrast to the fragments of a patella fracture. In addition, the edges of a bipartite or multipartite patella are well corticated.
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