Bipartite patella separation and partial quadriceps tendon rupture in the setting of trauma

Abstract

Normal development of the patella typically involves fusion of secondary ossification centers into a single bone during adolescence, with failure of fusion resulting in bipartite and tripartite patellae. In such variants, injury to incomplete ossification center fusion, though uncommon, has been reported to occur in the setting of traumatic quadriceps tendon rupture. The authors present a rare and complex case of traumatic bipartite fragment separation, patellar avulsion, and a complex partial quadriceps tendon tear confirmed surgically in a 36-year-old male. In this case, a tear in the lateral aspect of the quadriceps tendon attached to the nonfused patellar ossification center resulted in retraction of the band containing the bipartite fragment and separation of the patellar fragments, with superior displacement of the smaller bony avulsion likely due to complex attachments from the medial aspect of the quadriceps tendon. Knowledge of the classical locations of a bipartite and tripartite patella can aid in the differentiation of the anatomic variant versus patellar avulsion. Additionally, knowledge of the variable and complex nature of the quadriceps tendon aids in understanding the process of patellar avulsions and various tears, leading to the appropriate orthopedic management.

Keywords: Bipartite patella; CT, computed tomography; MRI, magnetic resonance imaging; ORIF, open reduction and internal fixation; Quadriceps rupture; Trauma.

Fig. 1

Coronal maximum intensity projection CT image demonstrates a superolateral defect within the patella with two well-corticated fragments (arrowheads) which are displaced superiorly due to avulsion/separation.

Fig. 2

Three sagittal CT slices of the knee demonstrating separated bipartite fragment with retraction of the ligamentous attachment (Fig 2A), smaller avulsed patellar fragment with retracted ligamentous attachment and adjacent fluid (Fig 2B), and subtle retraction and heterogeneity of the quadriceps tendon attached to the patella suggesting laxity and partial tear (Fig 2C).

Fig. 3

Lateral radiograph demonstrating superiorly displaced bony fragment suggestive of avulsion versus separation.