Biomechanical evaluation of lateral patellar dislocations

Area of Science:

• Orthopedic Surgery
• Sports Medicine
• Anatomy

Background:

• Acute lateral patellar dislocation is a common knee injury.
• The specific structures within the medial retinaculum that are torn during this injury are not fully understood.
• Accurate anatomical localization of these injuries is crucial for effective treatment.

Purpose of the Study:

• To identify torn structures within the medial retinaculum after acute lateral patellar dislocation.
• To anatomically localize these injury sites using a cadaver model.
• To correlate magnetic resonance imaging (MRI) findings with anatomical dissection.

Main Methods:

• Lateral translation of the patella (135% of width) was performed on 10 fresh-frozen cadaver knees using a universal testing instrument.
• Magnetic resonance imaging (MRI) was conducted before and immediately after testing.
• Anatomical dissection of the medial retinaculum was performed post-testing.

Main Results:

• Dissection revealed avulsion fractures from the inferomedial patellar border in 80% of specimens.
• The medial patellofemoral ligament was injured in 80%, with tears varying in location (femoral avulsion, midsubstance tear, or stretch).
• MRI identified medial retinaculum tears in 60%, correlating with specific ligament injuries (medial patellofemoral ligament from femur, medial patellomeniscal ligament from patella).

Conclusions:

• Acute lateral patellar dislocations involve injuries to the medial patellofemoral ligament and/or medial patellomeniscal ligament.
• Femoral-sided tears often represent the medial patellofemoral ligament, while patellar avulsion fractures may indicate the medial patellomeniscal ligament.
• Understanding this spectrum of injury can improve diagnostic accuracy and guide surgical restoration of damaged structures.