A hypoplastic patella fracture in nail patella syndrome: a case report

INTRODUCTION: Nail patella syndrome is a rare autosomal dominant hereditary condition, with an incidence of 22 per million in the United Kingdom. The syndrome's most common features include iliac horns, hypoplastic patella and nail dysplasia. CASE PRESENTATION: We report the case of a 26-year-old Caucasian man with nail patella syndrome who sustained a fracture of his right hypoplastic patella after a fall. His right knee became swollen and he was unable to extend against gravity immediately post fall. Radiographs revealed a fracture of the lower pole of his right patella with associated complete disruption of the extensor mechanism of the knee. He underwent operative fixation and his post operative course was uneventful. He was further treated post operatively with a full knee cast and graded immobilization. At six months he had regained the full range of motion at the knee joint. CONCLUSIONS: To the best of our knowledge, this is the only case report in the literature describing a patella fracture in an individual with nail patella syndrome. We hypothesize that given the extent of pre-existing knee joint impairment in these individuals, functional outcome may be inferior, suggesting the need for more frequent follow-up.