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 radiological and clinical advantages with patient-specific positioning guides in total knee replacement
Background and purpose — Although the use of patient-specific positioning guides ( PSPGs ) in total knee replacement ( TKR ) in theory is promising , the technique has not yet proven its superior- ity compared with the conventional method . We compared radio- logical alignment and clinical outcome between TKR performed with the use of PSPGs and the conventional operation method . Patients and methods — 3 hospitals participated in a prospec- tive trial . 109 patients were r and omized to either the conventional method or to the use of PSPGs .  Postoperatively a full-length st and ing anteroposterior radiograph and a postoperative CT scan were taken . On the CT scan the alignments were measured for both the femoral and tibial components in the frontal , sagit- tal , and axial plane . The Knee injury and Osteoarthritis Outcome Score ( KOOS ) , the Eurocol-5D-3L ( Eq5D ) descriptive system and visual analogue scale ( VAS ) , a pain score ( NRS ) , and range of motion ( ROM ) were recorded preoperatively , and at 3 months , 1 , and 2 years . The operation time and length of hospital stay were recorded . Results — 90 patients were available for postoperative CT mea- surements . A statistically significant difference was found between the conventional TKR instrumentation and the use of PSPGs for the frontal femoral ( mean ( SD ) 0.6 ° ( 1.7 ) vs. –0.3 ° ( 2.2 ) , CI 0.08 to 1.69 ) and tibial ( –0.3 ° ( 1.5 ) vs. 0.9 ° ( 2.1 ) , CI –1.98 to –0.44 ) compo- nent angles and for the tibial alignment in the sagittal plane ( –3.8 ° ( 3.0 ) vs. –2.2 ° ( 2.5 ) , CI –2.72 ; –0.42 ) . The proportions of outliers were similar between the groups as well as the hip – knee – ankle angle , the KOOS sub scores , the Eq5D , pain ( NRS ) , ROM , opera- tion time , and length of hospital stay . Interpretation — The use of PSPGs requires a preoperative CT scan or MRI and the guides have an additional cost . As this study was not able to prove any extra benefit of the use of PSPGs we recommend the conventional operation method for TKR
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 .