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Locked patellar dislocation due to osteophytes: two case reports with a focused literature review
Ngoc Quyen Le1, Trong Xuan Cuong Tran1
1Orthopedics, Trauma, and Rehabilitation Department, School of Medicine, University of Medicine and Pharmacy at Ho Chi Minh City, Ho Chi Minh City, Vietnam.
Introduction:
Locked patellar dislocation is a rare injury in which the patella becomes irreducible due to mechanical obstruction. Osteophytes have been increasingly recognized as a cause of irreducibility, but the mechanisms remain incompletely characterized.
Case Presentation:
Case 1: A 41-year-old female sustained a locked lateral, vertical, intra-articular patellar dislocation following a motorcycle collision. An inferomedial patellar osteophyte was impacted against the medial femoral condyle and entrapped within soft tissue, requiring open reduction. Case 2: A 57-year-old female presented with a superior patellar dislocation during massage. An inferior patellar osteophyte was entrapped against the femoral intercondylar notch, successfully reduced using a modified disengagement-first maneuver.
Clinical Discussion:
Both cases demonstrate distinct osteophyte-mediated pathomechanisms of irreducibility. In both patients, imaging before definitive treatment identified the mechanical block and guided the choice between closed and open reduction. Both patients achieved excellent functional outcomes.
Conclusion:
Osteophytes can transform a simple patellar dislocation into an irreducible locked injury. Imaging, particularly computed tomography when indicated, can identify the mechanical block and guide safe reduction.