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Age / Sex : /
Age / Sex : 17 / M
Chief complaint : Pain in left knee joint for 7 months
1) What is your impression?
Two weeks later, you can see the final diagnosis with a brief discussion of this case.
* Send Application Answers to Ja-Young Choi, MD (drchoi01@radiol.snu.ac.kr)
Courtesy : Byeong Seong Kang, MD. University of Ulsan College of Medicine, Ulsan University Hospital
Diagnosis: traumatic avulsion of bipartate patella
Discussion
Findings:
1. Plain radiography
- Bone fragment (1.6x0.8cm) in superolateral portion of patella
- Defect with smooth margin in superolateral portion of native patella
- Distension of suprapatellar bursa
- Swelling of prepatellar portion
2. MR
- Superolateral displacement of bipartite patella
- Edema between native patella and displaced bipartite patella
- Effusion in suprapatellar bursa
Discussion:
# Bipartite patella
-> Congenital fragmentation or synchondrosis of patella
-> Incidence : 2% ~ 6% -> M : F = 9 : 1
-> Bilateral : 50%
-> Three types: type I [distal pole (5%)], type II [lateral margin (20%)], type III [superolateral quadrant (75%)]
-> DDx with acute fracture
1) Bipartite patella is a frequently bilateral
2) Usually consists of a large main bone and a small bone usually situation at the upper outer quadrant of the patella
3) Radiolucent line of demarcation is wide and runs downward and lateral
4) Opposing bony margins are smooth, dense, and can be seen to be composed of bony cortices
# Traumatic avulsion of bipartite patella
- Patients with injuries to bipartite patella may develop pain associated with 2 variable presentations
1) Gradual onset of discomfort during activity
2) Sudden onset of pain after initial injury - When the cartilaginous connection between the ossification centers is weakened by recurrent microtrauma, inflammation or chronic stress - May be complicated with quadriceps tendon rupture
- Tx
1) Presence of an extra-articular fragment : excision
2) Presence of an intra-articular fragment : open reduction and internal fixaton
References:
1. Tauber M, Matis N, Resch H. Traumatic separation of an uncommon bipartite patella type: a case report. Knee Surg Sports Traumatol Arthrosc 2007;15:83-87
2. Thomas AL, Wilson RH, Thompson TL. Quadriceps avulsion through a bipartite patella. Orthopedics 2007;30:491-492
3. Ireland ML, Chang JL. Acute fracture bipartite patella: case report and literature review. Med Sci Sports Exerc 1995 ;27:299-302
4. Ball, O.G. Radiologic seminar CXXXV: bipartite patella. J MSMA 1974;15:18-20
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