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-matched instruments versus standard instrumentation in total knee arthroplasty: a prospective randomized study
Summary Background Optimal positioning of implants and restoration of neutral mechanical axis are two primary surgical goals in total knee arthroplasty ( TKA ) . Despite modern instruments and improved surgical techniques , malalignment remains an important cause of early failure after TKA . The aim of this prospect i ve r and omized study was to compare the value of a new patient-matched instrument system ( PMI ) ( SignatureTM ; Biomet , Inc , Warsaw , Indiana ) to that of st and ard TKA surgical instrumentation ( STD ) in terms of coronal mechanical alignment , time of operation and blood loss . Patients and methods A total of 38 patients waiting for primary TKA were enrolled and r and omized into two groups ( 19 PMI and 19 STD ) . Magnetic resonance imaging was performed in all patients in the PMI group , and specific instruments for the femur and tibia were design ed preoperatively . All patients were operated on using the st and ard medial parapatellar approach with no use of tourniquet . Mechanical axis , time for the operation , and blood loss were evaluated . Results Patients in both groups had comparable age , body mass index , preoperative mechanical axis , Knee Society Score , and level of hemoglobin . Postoperative results showed that the PMI group fell significantly closer to neutral mechanical axis ( STD : 2.7 ± 1.7 , PMI : 1.7 ± 0.9 ; P = 0.013 ) with no outliers and a reduced time for the operation . There was no difference in the evaluation blood loss . Conclusions The use of PMI can contribute in achieving better mechanical axis with reduction in outliers and decreased operation time . Due to small differences between PMI and st and ard instruments , additional research are needed to confirm these preliminary results , and to discover potential benefits and functional improvements in the long-term outcome
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 .