Systematic Review of Patella Cubiti: Does it really exist?

BACKGROUND: Accessory bones located dorsally to the elbow joint are exceedingly rare and remain poorly defined. These include the patella cubiti, os supratrochleare posterius, and os sesamoideum tricipitale, which are frequently misdiagnosed as traumatic or pathological entities such as congenital pseudarthrosis, persistent epiphysis, and non-unions. The present study aims to systematically analyse documented cases of patella cubiti, establish diagnostic criteria, and differentiate these conditions from other pathologies. METHODS: A systematic review of the literature was conducted, examining reported cases of patella cubiti. Each case was analysed based on available radiographic images and subsequently classified into one of four defined categories: patella cubiti, os sesamoideum tricipitale, congenital pseudarthrosis, or trauma. RESULTS: A total of 31 studies describing 38 cases identified as patella cubiti were included in the analysis. Based on the proposed definitions, three cases were classified as patella cubiti, three as os sesamoideum tricipitale, and two as a congenital pseudarthrosis. Additionally, 11 cases were attributed to traumatic aetiology, while 19 cases lacked sufficient quality to allow conclusive analysis. DISCUSSION: Historically, the term patella cubiti has been used broadly to describe any bony structure near the olecranon with uncertain aetiology leading to diagnostic ambiguity. Reports illustrating scenarios, where patella cubiti could be a congenital accessory bone, are rare, and existing data are insufficient to draw definitive conclusions. To improve diagnostic accuracy, three radiographic criteria for accessory bones should be employed, followed by MRI to distinguish patella cubiti from os sesamoideum tricipitale.