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 .
Patient-specific instrumentation improves tibial component rotation in TKA
Purpose To compare the femoral and tibial components rotational alignment in total knee arthroplasty ( TKA ) performed either with conventional or with patient-specific instrumentation . Methods Forty-five patients underwent primary TKA and were prospect ively r and omized into two groups : 22 patients into the conventional instrumentation group ( group A ) and 23 patients into the Signature ™ patient-specific instrumentation group ( group B ) . All patients underwent computed tomography of the operated knee in the first week after surgery to measure  the components rotation . Results The femoral component rotation was 0.0 ° ( −0.25 , 1.0 ) in group A , and 0.0 ° ( 0.0 , 1.0 ) in group B. The tibial component rotation was −16.0 ° ( −18.5 , 11.8 ) in group A , and −16.0 ° ( −19.0 , −14.0 ) in group B. There were no significant differences between the two groups in tibial and femoral components rotation . The difference between the tibial component rotation and the neutral tibial rotation was similar in both groups [ 2.0 ° ( −0.5 , 6.3 ) in group A and 2.0 ° ( −1.0 , 4.0 ) in group B ] , but the dispersion around the median was different between the two groups . The amplitude of the difference between tibial rotation and neutral position was 27 ° ( −13 , 14 ) in group A and 9 ° ( −3 , 6 ) in group B. Conclusions There is a smaller chance of internal malrotation of the tibial component with the Signature ™ patient-specific instrumentation system , with less dispersion and amplitude of the tibial component rotation around the neutral position . Level of evidence II
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 .