Aims and Objectives: To determine the prevalence of various injury patterns in patient with transient lateral patellar dislocation (TLPD) on magnetic resonance imaging (MRI).
Materials and methods: Thirty patients with clinical history pointing toward lateral patellar dislocation (LPD) were evaluated for the characteristic associated injury patterns including lateral femoral contusion, medial patellar contusion/osteochondral injury, medial retinaculum/medial patellofemoral ligament (MR/MPFL) injury, significant joint effusion, intraarticular loose bodies, medial collateral ligament (MCL) injury, and medial meniscus tear. Prevalence of all these findings was assessed.
Results: Our study showed some commonly observed injury patterns in patients with TLPD. Of 30 patients, 25 (83.3%) had MR/MPFL tear in general. Fifty percentage (15 of 30 patients) showed MPFL tear at its patellar insertion, 16.6% (5 of 30 patients) at its mid-part, and 46.6% (14 of 30 patients) at its femoral insertion; 80% (24 of 30 patients) revealed contusions of the lateral femoral condyle, and 73.33% (22 of 30 patients) had contusion/osteochondral injury of medial patella. Other MRI findings in TLPD included significant joint effusion (20 [66.6%] of 30), patellar tilt (17 [56.6%] of 30), patellar subluxation (17 [56.6%] of 30), medial meniscal tear (7 [23.3%] of 30), medial collateral injury (3 [10%] of 30), and intraarticular bodies (2 [6.6%] of 30).
Conclusion: Injury to the MR/MPFL, bony contusion involving lateral femoral condyle, and bony contusion/osteochondral injury involving medial aspect of patella are frequently associated with TLPD. Therefore, these findings should be used to diagnose TLPD.
Clinical significance: These findings can reliably help in diagnosing TLPD, and it is essential for the radiologist to be aware of these so as not to miss the diagnosis.
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