Dislocation of posteriorly stabilized total knee arthroplasties

Area of Science:

• Orthopedic surgery
• Biomedical engineering
• Knee biomechanics

Background:

• Posterior stabilized total knee arthroplasty (PS-TKA) is a common procedure for end-stage knee arthritis.
• The Insall-Burnstein II (IB-II) is a specific type of PS-TKA known for its stability.
• Dislocations of PS-TKA systems are infrequent but can lead to significant morbidity.

Observation:

• Two cases of Insall-Burnstein II total knee dislocation are presented.
• The dislocations occurred under specific conditions: loaded knee in extreme flexion with applied rotational force.
• Both cases involved a posterior stabilized design, specifically the IB-II system.

Findings:

• Closed reduction was successful in both reported cases of IB-II dislocation.
• The reduced knees were stable, indicating the integrity of the implant and surrounding structures post-reduction.
• No patient required revision surgery, suggesting favorable outcomes with non-operative management for these specific dislocations.

Implications:

• This report highlights a potential, previously undocumented failure mode for the Insall-Burnstein II total knee system.
• Understanding the mechanism of dislocation (extreme flexion + rotation on a loaded knee) is crucial for patient education and surgical technique.
• Non-operative management via closed reduction appears effective for these rare dislocations, potentially avoiding complex revision procedures.