A concern regarding the diagnosis of injury of a bipartite patella at the lower part of the patella

Abstract

I read with interest the article by Stocker et al. [1] entitled “Injury of a bipartite patella in a young upcoming sportsman”. I congratulate the authors on their very interesting case report; however, I have a concern regarding their diagnosis. It is my opinion that this case was not an injury of a bipartite patella but probably a fracture or stress fracture of the lower part of the patella. Their case suVered an intense pain around his left knee-cap while taking oV from a jumping board. A light swelling and light hematoma as well as local pain were identiWed. X-rays and magnetic resonance imaging showed an isolated distal pole of the patella with 2 mm diastasis. The radiographs taken 10 weeks after the injury showed a complete consolidation. In that report, the authors stated that a fracture or separation of the bipartite patella was retrospectively diagnosed. However, in our previous histopathological studies of the painful bipartite patella, we found that the striking features of the interpose tissue were Wbrous tissue and necrosis of the Wbrocartilage [2]. Therefore, I suppose that in the case of the developmental anomaly of ossiWcation type bipartite patella, consolidation may not take place and when consolidation is shown, it is probably fracture or stress fracture of the patella or accessory ossiWcation centers of the patella [3]. Okuno et al. [4] also described traumatic separation of a type I bipartite patella and bone union was obtained in their conservatively treated cases. However, these cases may also represent a transverse fracture or transverse stress fracture of the distal part of the patella. Another concern is the existence of the developmental anomaly of ossiWcation type bipartite patella at the lower part of the patella. In our previous clinical studies of the bipartite or tripartite patella, the developmental anomaly of ossiWcation type bipartite patella did not exist at the lower part of the patella [5]. Ogden [6] also mentioned that a separate ossiWcation center at the inferior pole probably does not exist. Thus, the existence of the developmental anomaly of ossiWcation type bipartite patella at the lower part of the patella is questionable. Several diseases such as Sinding-Larsen–Johansson lesion, fragmentations of the distal part of the patella associated with spastic cerebral palsy and transverse fracture or stress fracture could be included when bipartite fragment was observed at the distal part of the patella [5]. However, Sinding-Larsen–Johansson lesion and fragmentations of the distal part of the patella associated with spastic cerebral palsy could be excluded in this case. Therefore, Wnally, transverse fracture or stress fracture of the distal part of the patella may be suspected.