We did not find any differences between PSI and SI with respect to any other parameters .
Conclusions PSI  has advantages in axial alignment of the femoral component , operative time , and perioperative blood loss relative to SI .
No significant differences were found between PSI and SI with respect to alignment of the remaining components , number of outliers , or length of hospital stay .
Purpose The purpose of the present study was to compare patient-specific instrumentation ( PSI ) with st and ard instrumentation ( SI ) in patients undergoing total knee arthroplasty ( TKA ) .
PSI is hypothesized to have advantages with respect to component alignment ; number of outliers ( defined as alignment > 3 ° from the target alignment ) ; operative time ; perioperative blood loss ; and length of hospital stay .
This new surgical technique is expected to exhibit superior performance .
No improvement in reducing outliers in coronal axis alignment with patient-specific instrumentation
Purpose and hypothesisPatient-specific instrumentation ( PSI ) uses 3D preoperative imaging to produce individualized cutting blocks specific to patients ’ anatomy and according to the preoperative plan with the aim to reduce the number of mechanical leg alignment ( MLA ) outliers , to improve implant positioning and to decrease surgery time . The primary purpose of this study was to investigate the efficacy of a specific PSI in comparison with st and ard instrumentation ( SI ) in reducing the number of MLA outliers . It was hypothesized that the number of MLA outliers would be significantly lower in the PSI group . Methods A multicenter r and omized controlled trial was implemented . There were 59 patients in the PSI group and 66 in the SI group . The absolute number of outliers outside the ± 3 ° target neutral MLA was compared between the groups with a Chi-square test . As secondary outcomes , the Knee Society Score ( KSS ) and the Knee Injury and Osteoarthritis Outcome Score ( KOOS ) were compared between the groups preoperatively and at 90-day follow-up . Results There were 15 ( 26.3 % ) MLA outliers in the PSI group and 8 ( 12.3 % ) in the SI group . The number of outliers was not independent from the group ( X2(1 ) = 3.8 , p = 0.04 ; Relative risk = 1.5 ) . Preoperatively , there were no significant differences between the groups when comparing their KSS and KOOS sub-scores . At 90 days postoperatively , the patients in the SI group showed better KOOS- Quality of Life ( KOSS-QOL ) in comparison with the PSI group ( p < 0.0001 ) . Conclusion The use of PSI did not significantly reduce the number of MLA outliers in comparison with SI . There were no differences when comparing the achieved mean MLA of both groups . Level of evidence Level I , prospect i ve r and omized controlled trial
We did not find any differences between PSI and SI with respect to any other parameters .
Conclusions PSI  has advantages in axial alignment of the femoral component , operative time , and perioperative blood loss relative to SI .
No significant differences were found between PSI and SI with respect to alignment of the remaining components , number of outliers , or length of hospital stay .
Purpose The purpose of the present study was to compare patient-specific instrumentation ( PSI ) with st and ard instrumentation ( SI ) in patients undergoing total knee arthroplasty ( TKA ) .
PSI is hypothesized to have advantages with respect to component alignment ; number of outliers ( defined as alignment > 3 ° from the target alignment ) ; operative time ; perioperative blood loss ; and length of hospital stay .
This new surgical technique is expected to exhibit superior performance .