Bipartite patella fracture with quadriceps rupture is an unusual injury. It is quite often mistaken as an avulsion fracture of patella, and the X-ray of contra-lateral knee is useful for diagnosis, and appropriate treatment should be decided at the time of surgery. We report a single case of this entity in which bipartite patella fracture was misdiagnosed initially as a patellar fracture. IntroductionThe secondary ossification centre of patella that fails to coalesce with the primary ossification centre results in bipartite patella. The incidence of bipartite patella in general population is about 2%, and about 50% are bilateral, and only 2% are symptomatic.Research suggests that 75% of patellae ossify by single centre and 23% ossify by two to three centres [1]. These secondary ossification centres usually appear around the age of 12 [1-3]. The primary centre of ossification generally appears between 21 and 54 months in girls and 36 and 72 months in boys [1].Saupe, in 1943, classified bipartite patella into the following three types: type I, located at the inferior pole, 5% of patients; type II, located at the lateral margin, 20% of patients; and type III is the superolateral location (most common type), 75% of patients [13].

Background: Polycarbonate urethane (PCU) is a bearing surface with a lower modulus of elasticity than polyethylene or ceramic and is thought to more closely replicate the tribology of native hyaline cartilage. The purpose of this study was to determine the clinical outcomes with the use of PCU in elective total hip arthroplasty (THA). Methods: We carried out a prospective observational study in which 157 patients underwent elective THA with a metal-on-PCU hip system. Patients had radiographic follow-up at 6 months and 3 years after surgery. Oxford Hip Scores and EuroQol scores were obtained annually and Harris Hip Scores were obtained at 6 months and 3 years after surgery. Results: 180 hips were implanted, of which, 149 hips reached 3-year review with no revisions. There was an increase in Harris Hip Scores, Oxford Hip Scores and EuroQol scores ( p < 0.001). 12 patients (12 hips) reported painless hip squeaking. There were no dislocations and no other adverse events were reported. Conclusion: Our results showed satisfactory survivorship and improvements in patient reported outcomes with metal on PCU THA. Long-term data are still being collected to confirm these findings. We recommend further tribological research into the squeaking phenomenon we observed.

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