Verification of in vivo accuracy of Trumatch™ patient-specific instrumentation in total knee replacement using pin-less computer navigation

Purpose: Accurate component alignment in total knee replacement (TKR) is one of the important factors in determining long-term survivorship. This has been achieved by conventional jigs, computer-assisted technology (CAS) and more recently patient-specific instrumentation (PSI). The purpose of the current study was to investigate the in vivo accuracy of Trumatch™ PSI using validated pin-less computer navigation system.  

Method: Twenty consecutive selected patients that fulfilled our inclusion/exclusion criteria underwent TKR using PSI. Coronal alignment, posterior slope, resection thickness and femoral sagittal alignment were recorded using pin-less navigation. The position of the actual cutting block was appropriately adjusted prior to proceeding to definitive resections.  

Results: The coronal alignment using PSI without the assistance of navigation would have resulted in 14 (70 %) within ±3°, 11 (55 %) within ±2° and 6 (30 %) outside acceptable alignment. Thirty-five percentage of proposed femur sagittal alignment and 55 % of posterior tibial slope were achieved within ±3°. Components size was accurately predicted in 95 % of femurs and 90 % of tibia.  

Conclusion: The purported advantages in restoring alignments using Trumatch™ PSI alone over standard equipment are debatable. However, it predicts sizing well, and femoral coronal alignment is reasonable. Combining Trumatch™ PSI with CAS will allow in vivo verification and necessary corrections.