Patellar Fractures in Children. A Case Report in a Seven Year Old Girl

Summary

We describe a rare case of patellar fracture in a seven year old girl. The case was reviewed for various aspects such as clinical diagnosis, imaging tests and most suitable treatment.

Introduction

Pediatric patellar fractures are relatively uncommon. However, when reported, they involve patients younger than 16 years [1]. The peak incidence is between 8-12 years of age [2,3].The reason for this is the relative flexibility of the patella in childhood, which is less affected by impact and tension forces during quadriceps contraction [4]. The mechanism of such fractures is either due to direct trauma and/or excessive contraction of the extensor mechanism. Houghton and Ackroyd [5] elucidated an avulsion-type fracture of the lower end of the patella; in such fractures a significant chunk of cartilage is avulsed from the patella affixed to a discreet bone fragment. Such fractures may not be commonly diagnosed, especially if there is a large hemarthrosis or if radiographs studies aren’t clear about the fracture line [5,6]. Grogan et al. [7] gave his classification of pediatric patellar fractures based on their anatomic location. The proximal avulsion fracture, which is the commonest, involves the patellar upper pole while as the distal end avulsion is commonly traumatic, just like our case. Medial avulsion injury can be seen after a lateral patellar dislocation. The avulsion of the superolateral corner of the patella may be mistaken for a bipartite patella [8] or may be stress induced due to repeated traction of the vastus lateralis muscle [9]. A similar stress induced injury is the Sinding-Larsen-Johansson disease, due to repeated stress of the distal patellar end,s causing an incomplete avulsion of the patellar ligament fibers and subsequent necrosis and calcification [10]. In such cases, MRI of the knee is the diagnostic modality of choice [11-13] in the detection of this condition in order to avoid later damage to knee extension or the formation of megapatellas with irregular joint surface [14-16].