title: Patient-specific instrumentation improves tibial component rotation in TKA Rotation in total knee arthroplasty: no difference between patient-specific and conventional instrumentation Patient-specific Total Knee Arthroplasty Required Frequent Surgeon-directed Changes Patient-specific instrumentation for total knee arthroplasty does not match the pre-operative plan as assessed by intra-operative computer-assisted navigation Patient-specific instrumentation does not shorten surgical time: a prospective, randomized trial. Reliability of templating with patient-specific instrumentation in total knee arthroplasty. The radiological outcomes of patient-specific instrumentation versus conventional total knee arthroplasty Evaluation of the accuracy of a patient-specific instrumentation by navigation The value of patient-matched instrumentation in total knee arthroplasty. Patient-specific total knee arthroplasty: the importance of planning by the surgeon Patient specific cutting blocks are currently of no proven value. A prospective randomised controlled study of patient-specific cutting guides compared with conventional instrumentation in total knee replacement.
abstract: 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 Abstract Purpose It was our hypothesis that patient-specific instrumentation ( PSI ) can improve the accuracy of the rotational alignment in TKA based on the concept of the system and on the potential to clearly identify pre-operatively during planning the classical anatomical l and marks that serve as references to set-up the rotation both for the femur and tibia . Material s and methods In this prospect i ve comparative r and omized study , 40 patients ( 20 in each group ) operated in our institution between September 2012 and January 2013 by the 2 senior authors were included . R and omization of patients into one of the two groups was done by the Hospital Informatics Department with the use of a systematic sampling method . All patients received the same cemented high-flex mobile bearing TKA . In the PSI group , implant position was compared to the planed position using previously vali date d dedicated software . The position of the implants ( frontal and sagittal ) was compared in the 2 groups on st and ard X-rays , and the rotational position was analysed on post-operative CT-scan . Results 90 % of the patients add < 2 ° or mm of difference between the planned position of the implants and the obtained position , except for the tibial rotation where the variations were much higher . Mean HKA was 179 ° ( 171–185 ) in the PSI group with 4 outliers ( 2 varus : 171 ° and 172 ° :184 ° and 185 ° ) and 178.3 ° with 2 outliers ( 171 ° and 176 ° ) in the control group . No difference was observed between the two groups concerning the frontal and sagittal position of the implants on the ML and AP X-rays . No significant difference of femoral rotation was observed between the two groups with a mean of 0.4 ° in the PSI group and 0.2 ° in the control group ( p : n.s ) . Mean tibial rotation was 8 ° of internal rotation in the PSI group and 15 ° of internal rotation in the st and ard group ( p : n.s ) . Conclusion Based on our results , we were unable to confirm our hypothesis as PSI can not improve rotation in TKA . More work needs to be done to more clearly define the place of PSI in TKA , to keep on improving the accuracy of the system and to better define the individual targets in TKA in terms of frontal , sagittal and rotational positioning of the implant for each patient . Level of evidence Prospect i ve comparative r and omized study , Level II Background Patient-specific instrumentation potentially improves surgical precision and decreases operative time in total knee arthroplasty ( TKA ) but there is little supporting data to confirm this presumption . Questions / purpose sWe asked whether patient-specific instrumentation would require infrequent intraoperative changes to replicate a single surgeon ’s preferences during TKA and whether patient-specific instrumentation guides would fit securely . Methods We prospect ively evaluated the plan and surgery in 60 patients treated with 66 TKAs performed with patient-specific instrumentation and recorded any changes . A subset of six postoperative radiographic changes to the femoral and tibial components ( implant size , coronal and sagittal alignment ) was analyzed to determine if surgeon intervention was beneficial . Each guide was evaluated to determine fit . We compared patient demographics and implant sizing in the patient-specific instrumentation group with a control group in which traditional instrumentation was used . Results We recorded 161 intraoperative changes in 66 knee arthroplasties ( 2.4 changes/knee ) performed with patient-specific instrumentation . The predetermined implant size was changed intraoperatively in 77 % of femurs and 53 % of tibias . We identified a subset of 95 intraoperative changes that could be radiographically evaluated to determine if our changes were an improvement or detriment to reaching goal alignment . Eighty-two of the 95 changes ( 86 % ) made by the surgeon were an improvement to the recommended alignment or size of patient-specific instrumentation . The guide did not fit securely on eight femurs ( 12 % ) and three tibias ( 5 % ) . Tourniquet time and blood loss were not improved with patient-specific instrumentation . Conclusions We caution surgeons against blind acceptance of patient-specific instrumentation technology without supportive data .Level of Evidence Level III , therapeutic study . See Guidelines for Authors for a complete description of levels of evidence Abstract Purpose The introduction of patient-specific instruments ( PSI ) for guiding bone cuts could increase the incidence of malalignment in primary total knee arthroplasty . The purpose of this study was to assess the agreement between one type of patient-specific instrumentation ( Zimmer PSI ) and the pre-operative plan with respect to bone cuts and component alignment during TKR using imageless computer navigation . Methods A consecutive series of 30 femoral and tibial guides  were assessed in-theatre by the same surgeon using computer navigation . Following surgical exposure , the PSI cutting guides were placed on the joint surface and alignment assessed using the navigation tracker . The difference between in-theatre data and the pre-operative plan was recorded and analysed . Results The error between in-theatre measurements and pre-operative plan for the femoral and tibial components exceeded 3 ° for 3 and 17 % of the sample , respectively , while the error for total coronal alignment exceeded 3 ° for 27 % of the sample . Conclusion The present results indicate that alignment with Zimmer PSI cutting blocks , assessed by imageless navigation , does not match the pre-operative plan in a proportion of cases . To prevent unnecessary increases in the incidence of malalignment in primary TKR , it is recommended that these devices should not be used without objective verification of alignment , either in real-time or with post-operative imaging . Further work is required to identify the source of discrepancies and vali date these devices prior to routine use . Level of evidence II The primary purpose of this prospect i ve , r and omized study was to determine if patient-specific instrumentation ( PSI ) for total knee arthroplasty ( TKA ) shortened surgical time . Secondarily the number of instrument trays and alignment were also compared to cases performed with traditional instrumentation ( TI ) .  Fifty-two cases ( 26 per group ) were r and omized and videotaped to measure the length of surgery , as well as each individual surgical step . Component alignment and mechanical axis was measured radiographically for each patient . Total surgical time was over 4 minutes shorter for patients in the TI group ( 57.4 minutes vs. 61.8 minutes ; P<0.01 ) . More instrument trays were used in the TI group ( 7.3 vs. 2.5 ; P<0.001 ) . There was no significant difference in mechanical alignment between groups on postoperative long alignment radiographs ( P=0.77 ) . In conclusion , PSI did not shorten surgical time or improve alignment compared with TI in this prospect i ve , r and omized trial , but did reduce the required number of trays Magnetic resonance imaging ( MRI ) or computed tomography-based patient-specific instrumentation ( PSI ) may allow for reliable alignment and fewer outliers when compared with conventionally instrumented total knee arthroplasty ( TKA ) . However , some authors have suggested that frequent intraoperative surgeon-directed changes may still be required . This study evaluated the accuracy of  PSI  to predict component sizing and alignment during TKA . A total of 84 patients ( 89 knees ) who underwent a TKA using a PSI system were evaluated . An MRI-based preoperative plan of every knee was provided and approved by the surgeons . This demonstrated the proposed prosthetic component alignment , as well as the femoral , tibial , and bearing insert component size and position . Intraoperative changes to these components were prospect ively recorded and compared with the computerized preoperative plan . Major changes were defined as any changes in femoral or tibial resection , size , and position of the components . Minor changes were defined as any change in the size of the polyethylene bearing insert . The preoperative plan was able to correctly predict the size of the implanted tibial and femoral component in 93 and 95.5 % of the cases , respectively . Thirteen major intraoperative changes were made . In one knee , the proposed femoral resection was not acceptable ( because of the presence of significant amount of osteophytes ) and was ab and oned in favor of a manual extramedullary guide . In another patient , the proposed femoral and tibial components were upsized . In two other patients , the femoral components were downsized , in four patients , the tibial components were downsized , and in another patient , it was upsized . There were also 16 minor changes , which included 2-mm upsizing of the polyethylene liner in 13 knees and 4-mm upsizing in 3 knees . Surgical experience is necessary to recognize improper component size , incorrect surgical resection , or nonideal alignment when performing TKA using PSI . The authors believe that the design and manufacture of PSI combined with a comprehensive templating result ed in excellent intraoperative concordance of the preoperative plan at the default setting s with minimal changes Abstract Purpose The aim of this study was to investigate the post-operative radiological outcomes of patient-specific instrumentation ( PSI ) surgery versus conventional total knee arthroplasty ( TKA ) . Methods Sixty patients scheduled for a primary TKA were prospect ively divided into PSI or conventional technique . Coronal and sagittal radiographic long limb films were taken post-operatively . The accepted values for normal alignment were 180 ° ± 3 ° for hip-knee-ankle angle ; 90 ° ± 3 ° for coronal femoral component angle or coronal tibia component angle ; 0 ° to 3 ° flexion for sagittal femoral component angle and 0 ° to 7 ° posterior slope for sagittal tibia component angle . Results For hip-knee-ankle angle , there were 21 % more outliers in the PSI group compared to the conventional group ( p = 0.045 ) . Most of these outliers had valgus deformity in the PSI group and varus deformity in the conventional group ( p = 0.045 ) . For implant placement , there was no difference in the proportion of outliers between the two groups . There was also no difference in the duration of surgery . Conclusions This study showed that PSI surgery is associated with a larger proportion of outliers for lower limb alignment . PSI surgery as an alternative to conventional TKA is not advisable . Level of evidence II Purpose The aim of this study is to evaluate the accuracy of a  patient-specific instrumentation ( PSI ) as assessed by the intraoperative use of knee navigation software during the surgical procedure . Methods Fifteen patients with primary gonarthrosis were selected for unilateral total knee arthroplasty . The first three patients were excluded from this study , as they were considered to be a warm up to set-up the procedure . All patients were operated on with a cemented posterior-stabilised prosthesis cruciate ligament-sacrificing by the same surgeon using the patient matched cutting jigs . The size of the implant , level of resection , and alignment in the coronal and sagittal planes were evaluated . An unsatisfactory result was considered an error ≥2 ° in both planes for each component as a possible error of 4 ° could result in aggravation . Results On the coronal plane the mean deviation of the tibial guide from the ideal alignment was 1.2 ± 1.5 ( range 0–5 ° ) and in the sagittal plane was 3.8 ± 2.4 ( range 0–7.5 ° ) . On the coronal plane the mean deviation of the femoral guide from the ideal alignment was 1.2 ± 0.6 and in the sagittal was 3.7 ± 2 . Conclusion On the basis of this preliminary experience the PSI system based only on data acquisition with A-P radiograms and RMN can not be defined as accurate . In cases of the use of the custom made cutting jigs it is recommended to perform an accurate control of the alignment before making the cuts , for any step of the procedure . Level of evidence II The purpose of the current prospect i ve , r and omized study was to compare the value of a new mechanically aligned patient-matched instrument system for total knee arthroplasty ( TKA ) ( Visionaire ; Smith & Nephew , Inc , Memphis , Tenn ) ( VIS ) to that of st and ard TKA surgical instrumentation ( STD ) . Twenty-nine primary TKA patients were enrolled and completed surgery ( 15 VIS and 14 STD ) . Postoperatively , mechanical alignment was significantly closer to neutral zero in the VIS group ( 1.7 ° vs 2.8 ° ; P = .03 ) . Furthermore , the VIS group demonstrated significant reductions in duration of hospital stay , operative time , incision length , and number of used instrument trays ( P < .05 ) . Although additional research is underway to confirm these preliminary results , this evidence suggests that patient-matched instrumentation may support repeatable improvements in surgical accuracy and hospital efficiency Abstract Purpose The purpose of the study was to evaluate the accuracy of the planning of the patient-specific pin guides in total knee arthroplasty ( TKA ) . This planning was performed primarily by a technician of the company and offered to the surgeon . All parameters of the implantation can either be modified or accepted by the surgeon . The hypothesis was that the plan needs preoperative intervention by the surgeon . Methods A prospect i ve study in 50 patients was carried out . All patients received the same posterior-stabilised implant with patient-specific instrumentation . All surgical parameters ( coronal , sagittal , rotational alignment , femoral and tibial resection levels and implant sizes ) were checked by the orthopaedic surgeon and changed if necessary . Results Preoperatively , the femoral size was changed in 8 patients ( 16 % ) , the femoral flexion in 23 patients ( 46 % ) , the femoral shift in 34 patients ( 68 % ) , the tibial size in 24 patients ( 48 % ) and the tibial rotation in all patients . The epicondylar axis was accepted in 47 patients ( 94 % ) in the technician plan . Mean planning time was 8 ± 4 min . Intraoperatively , the femoral anterior – posterior size was in 50 patients ( 100 % ) the same as in the surgeon and in 42 patients ( 84 % ) the same as in the technician plan ( p = 0.003 ) . The tibial component implanted was in 42 patients ( 84 % ) the same as in the surgeon and in 19 patients ( 38 % ) the same as in the technician plan ( p < 0.0001 ) . A femoral distal recut was necessary in 31 patients ( 62 % ) and a change of the tibial proximal cut in 17 patients ( 34 % ) during surgery . Intraoperatively , no changes of the femoral and tibial alignment , the femoral anterior – posterior size , the femoral flexion , the femoral shift , the femoral and tibial rotation were necessary . Postoperatively , the coronal mechanical overall axis was within ±3 ° in 47 patients ( 94 % ) with a maximum deviation of 5.6 ° . Conclusions Significant changes of the technician plan were necessary to get an accurate preoperative plan . Intraoperative changes were significant less compared to the surgeon than to the technician plan . No major changes ( alignment , femoral anterior – posterior size and rotation ) of the surgeon plan were necessary . Surgeons using patient-specific pin guides in TKA may verify the default plan provided by the technician . A blind reply on the technician plan may be not recommended . Level of evidence Therapeutic study , Level III Patient specific cutting guides generated by preoperative Magnetic Resonance Imaging ( MRI ) of the patient 's extremity have been proposed as a method of improving the consistency of Total Knee Arthroplasty ( TKA ) alignment and adding efficiency to the operative procedure . The cost of this option was evaluated by quantifying the savings from decreased operative time and instrument processing costs compared to the additional cost of the MRI and the guide .  Coronal plane alignment was measured in an unselected consecutive series of 200 TKAs , 100 with st and ard instrumentation and 100 with custom cutting guides .  While the cutting guides had significantly lower total operative time and instrument processing time , the estimated $ 322 savings was overwhelmed by the $ 1,500 additional cost of the MRI and the cutting guide . All measures of coronal plane alignment were equivalent between the two groups . The data does not currently support the proposition that patient specific guides add value to TKA Patient-specific cutting guides ( PSCGs ) are design ed to improve the accuracy of alignment of total knee replacement ( TKR ) . We compared the accuracy of limb alignment and component positioning after  TKR  performed using PSCGs or conventional instrumentation . A total of 80 patients were r and omised to undergo TKR with either of the different forms of instrumentation , and radiological outcomes and peri-operative factors such as operating time were assessed . No significant difference was observed between the groups in terms of tibiofemoral angle or femoral component alignment . Although the tibial component in the PSCGs group was measurably closer to neutral alignment than in the conventional group , the size of the difference was very small ( 89.8 ° ( sd 1.2 ) vs 90.5 ° ( sd 1.6 ) ; p = 0.030 ) . This new technology slightly shortened the bone-cutting time by a mean of 3.6 minutes ( p < 0.001 ) and the operating time by a mean 5.1 minutes ( p = 0.019 ) , without tangible differences in post-operative blood loss ( p = 0.528 ) or need for blood transfusion ( p = 0.789 ) . This study demonstrated that both PSCGs and conventional instrumentation  restore limb alignment and place the components with the similar accuracy . The minimal advantages of PSCGs in terms of consistency of alignment or operative time are unlikely to be clinical ly relevant
target: Results The majority of studies did not show an improvement in overall limb alignment when PSI was compared with st and ard instrumentation .
  The studies demonstrated mixed results regarding the influence of PSI on operative times .
  Decreased operative times were not uniformly observed , and when noted , they were found to be of minimal clinical or financial significance .
  PSI did reliably reduce the number of instrument trays required for processing perioperatively .
  The accuracy of the preoperative plan , generated by the PSI manufacturers , was found lacking , often leading to multiple intraoperative changes , thereby disrupting the flow of the operation and negatively impacting efficiency .
  Neither of the two studies we identified provided strong evidence to support an advantage favoring the use of PSI .
  Conclusions PSI for TKA has not reliably demonstrated improvement of postoperative limb or component alignment when compared with st and ard instrumentation .
  Although decisive evidence exists to support that PSI requires fewer surgical trays , PSI has not clearly been shown to improve overall surgical efficiency or the cost-effectiveness of TKA .
  Limited available literature does not clearly support any improvement of postoperative pain , activity , function , or ROM when PSI is compared with traditional instrumentation
background: Background Patient-specific cutting blocks have been touted as a more efficient and reliable means of achieving neutral mechanical alignment during TKA with the proposed downstream effect of improved clinical outcomes .
  However , it is not clear to what degree published studies support these assumptions .
  Questions / purpose sWe asked : ( 1 ) Do  patient-specific cutting blocks  achieve neutral mechanical alignment more reliably during TKA when compared with conventional methods ? (
  2 ) Does patient-specific instrumentation ( PSI ) provide financial benefit through improved surgical efficiency ? (
  3 ) Does the use of patient-specific cutting blocks translate to improved clinical results after TKA when compared with conventional instrumentation ?