Abstract
INTRODUCTION
The patient-specific templates (PST) for total knee arthroplasty (TKA) have been developed to improve accuracy of implantation, decrease operating time and decrease costs. There remains controversy about the accuracy of PST in comparison with either navigated or conventional instruments. Furthermore, the learning curve after introducing PST has not been well defined. The goal of the present study was to perform quality control with a commercially available navigation system and the CUCUM test when introducing PST technique at our academic department.
MATERIAL AND METHODS
The first 50 TKAs implanted with the use of PST at an academic department were scheduled to enter in a prospective, observational study. PSTs were designed to obtain a neutral coronal alignment. All TKAs were implanted by an experienced, high volume senior consultant with high experience in knee navigation. PSTs were carefully positioned over the bone and articular surfaces to the best fit position, without any navigated information. Then the 3D femoral and tibia PSTs positioning were recorded by the navigation system. The difference between expected and achieved position was calculated, and an accuracy score was calculated and plotted according to the rank of observation into a CUSUM test.
RESULTS
There was no significant difference between the numerical values of femur plan and femur PST positioning for all four items. There was a significant difference between the numerical values of tibia plan and tibia PST positioning for all four items except the sagittal orientation. The knee score was still out of control after the 20th case. Both femur and tibia scores were still out of control after the 20th case as well. The decision was taken to interrupt the study after the 20th case as the learning curve appeared unacceptably long in comparison to the routine navigated technique.
DISCUSSION
Introduction of PST in an academic centre may involve a significant learning curve: the process remained out of control even after 20 procedures. The present results contradict the common belief that introduction of PSTs is easy and does not require special instruction. These results indicate that surgeons should have only a progressive confidence with the self- sitting of PSTs when introducing this technology. The decision was taken to discontinue using PSTs for TKA.
