Abstract
Introduction: Contact stresses, derived from navigation system and conventional TKR alignments, are compared to ideally aligned component stresses.
Methods: This study builds upon the work of previous studies, in which post-operative CT scans from 70 patients were utilized to extract knee component angular alignments from patients undergoing both navigation based and conventional TKR. Knee component (Stryker Orthopaedics DuraconTM Condylar) FE models were oriented into specific alignment positions. Tibial insert contact stresses were computed under physiologically relevant loads at various flexion angles. FEA was also performed on ideally aligned cases for comparison purposes.
Results: At full extension, the median alignment of conventional TKR induces contact stresses 17.8% above ideal alignment conditions. Navigation based TKR alignment induces stresses 3.5% above ideal alignment conditions. At 45–90° flexion, conventional TKR alignment induces stresses 2.7% above ideal alignment conditions, while comparable navigation based TKR alignment induces stresses that match ideal alignment conditions.
Conclusion: Navigation based TKR procedures improve knee component alignment, which decreases contact stresses in UHMWPE tibial inserts. The result is a reduction in abnormal wear patterns and expected wear rates, with an increase in the structural longevity of knee system components.
Correspondence should be addressed to Mr Tim Wilton, BASK at the Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London WC2A 3PE.
