Patient-specific instrumentation in total knee arthroplasty: simpler, faster and more accurate than standard instrumentation—a randomized controlled trial Comparison between patient-specific instruments and conventional instruments and computer navigation in total knee arthroplasty: a randomized controlled trial Component alignment and clinical outcome following total knee arthroplasty: a randomised controlled trial comparing an intramedullary alignment system with patient-specific instrumentation. Improved alignment and operating room efficiency with patient-specific instrumentation for TKA. The radiological outcomes of patient-specific instrumentation versus conventional total knee arthroplasty No improvement in reducing outliers in coronal axis alignment with patient-specific instrumentation Reliability of templating with patient-specific instrumentation in total knee arthroplasty. Patient-specific instrumentation does not shorten surgical time: a prospective, randomized trial. Patient-specific instrumentation improved mechanical alignment, while early clinical outcome was comparable to conventional instrumentation in TKA Patient-specific computed tomography based instrumentation in total knee arthroplasty: a prospective randomized controlled study In-vivo alignment comparing patient specific instrumentation with both conventional and computer assisted surgery (CAS) instrumentation in total knee arthroplasty. Patient-specific instrumentation for total knee arthroplasty does not match the pre-operative plan as assessed by intra-operative computer-assisted navigation Intra-operative results and radiological outcome of conventional and patient-specific surgery in total knee arthroplasty: a multicentre, randomised controlled trial Stability and alignment do not improve by using patient-specific instrumentation in total knee arthroplasty: a randomized controlled trial The John Insall Award: No Functional Benefit After Unicompartmental Knee Arthroplasty Performed With Patient-specific Instrumentation: A Randomized Trial Rotation in total knee arthroplasty: no difference between patient-specific and conventional instrumentation The value of patient-matched instrumentation in total knee arthroplasty. A comparison of patient-specific and conventional instrumentation for total knee arthroplasty: a multicentre randomised controlled trial. Patient-matched instruments versus standard instrumentation in total knee arthroplasty: a prospective randomized study Computer-assisted total knee arthroplasty using mini midvastus or medial parapatellar approach technique The accuracy of component alignment in custom cutting blocks compared with conventional total knee arthroplasty instrumentation: prospective control trial. Kinematic femoral alignment with gap balancing and patient-specific instrumentation in total knee arthroplasty: a randomized clinical trial Evaluation of the accuracy of a patient-specific instrumentation by navigation Patient-specific Guides Do Not Improve Accuracy in Total Knee Arthroplasty: A Prospective Randomized Controlled Trial Component alignment during total knee arthroplasty with use of standard or custom instrumentation: a randomized clinical trial using computed tomography for postoperative alignment measurement.
Abstract Purpose This r and omized controlled trial was conducted to compare patient-specific instrumentation ( PSI ) to st and ard instrumentation regarding efficacy to achieve a good coronal alignment and differences in surgical time , blood loss and length of stay . Methods Ninety-five of 100 r and omized patients eligible for total knee arthroplasty were analysed .  PSI with magnetic resonance and long-leg radiograph was performed in 47 patients , while 48 patients received st and ard instrumentation .  Primary outcome measure was coronal alignment , evaluated with long-leg radiograph . Deviation > 3 ° varus/valgus was considered an outlier . Surgical time was compared from skin to skin . Length of stay was a post hoc analysis . Blood loss was evaluated comparing the number of blood units spent , fall in haemoglobin and haematocrit levels . Results St and ard instrumentation had a higher number of outliers in the coronal alignment with a relative risk of 3.015 , compared to PSI . Surgical time was reduced by 18 min ( 24.8 % ) with the  PSI  , as well as length of stay , with a half-day reduction . Number of blood units spent was significantly less in the PSI group . Relative risk of transfusion was 7.09 for patients in the st and ard instrumentation group . Difference in Hg and Htc levels were not significant . No patient had to ab and on PSI . Minor changes to preoperative plan occurred in 14.9 % of the patient : cut review in 4.3 % and insert change in 10.6 % . Conclusions Patient-specific instrumentation ( PSI ) is able to provide important advantages over st and ard instrumentation in total knee arthroplasty : it lowers the risk of outliers and transfusion , is a faster procedure and enables a shorter length of stay with a low rate of intraoperative adjustments . Level of evidence Abstract Purpose The current study investigated the accuracy in achieving proper lower limb alignment and individual component positions after total knee arthroplasty ( TKA ) with 3 different instrumentation techniques . It was hypothesized that patient-specific instruments ( PSI ) would achieve more accurate lower limb alignment and component positions compared to conventional instruments ( CON ) . Methods Ninety knees in 81 patients were r and omized in 1:1:1 ratio into  CON , computer navigation ( NAV )  and PSI  groups to receive TKA . The surgical routines were st and ardized . The lower limb mechanical axis and individual component positions were assessed on st and ard radiographs . Tourniquet time , operation time and patients ’ functional scores were documented . Results Conventional instruments and PSI were more likely to result in an excessively flexed femoral component ( p = 0.001 ) compared to NAV . Number of outliers in postoperative lower limb alignment , and other components positions in the coronal and sagittal plane showed no statistically significant difference . The mean tourniquet time and operation time was significantly shorter in CON and PSI groups than NAV group ( p < 0.001 ) . Four early complications occurred in the PSI group ( p = 0.015 ) . At 3-month follow-up , there was no difference in terms of the knee range of motion and patients ’ function among the 3 groups . Conclusion No significant radiological and clinical benefit could be demonstrated in using PSI over CON or NAV in TKA . Routine use of PSI is not recommended because of the extra cost and waiting time . Level of evidence AIMS We conducted a r and omised controlled trial to assess the accuracy of positioning and alignment of the components in total knee arthroplasty ( TKA ) , comparing those undertaken using st and ard intramedullary cutting jigs and those with patient-specific instruments ( PSI ) . PATIENTS AND METHODS There were 64 TKAs in the st and ard group and 69 in the PSI group . The post-operative hip-knee-ankle ( HKA ) angle and positioning was investigated using CT scans . Deviation of > 3 ° from the planned position was regarded as an outlier . The operating time , Oxford Knee Scores ( OKS ) and Short Form-12 ( SF-12 ) scores were recorded . RESULTS There were 14 HKA-angle outliers ( 22 % ) in the st and ard group and nine ( 13 % ) in the PSI group ( p = 0.251 ) . The mean HKA-angle was 0.5 ° varus in the st and ard group and 0.2 ° varus in the PSI group ( p = 0.492 ) . The accuracy of alignment in the coronal and axial planes and the proportion of outliers was not different in the two groups . The femoral component was more flexed ( p = 0.035 ) and there were significantly more tibial slope outliers ( 29 % versus 13 % ) in the PSI group ( p = 0.032 ) . Operating time and the median three-month OKS were similar ( p = 0.218 and p = 0.472 , respectively ) . Physical and mental SF-12 scores were not significantly different at three months ( p = 0.418 and p = 0.267 , respectively ) or at one year post-operatively ( p = 0.114 and p = 0.569 ) . The median one-year Oxford knee score was two points higher in the PSI group ( p = 0.049 ) . CONCLUSION Compared with st and ard intramedullary jigs , the use of PSI did not significantly reduce the number of outliers or the mean operating time , nor did it clinical ly improve the accuracy of alignment or the median Oxford Knee Scores . Our data do not support the routine use of PSI when undertaking TKA . Cite this article : Bone Joint J 2016;98-B:1043 - 9 BACKGROUND Achieving accurate alignment in total knee arthroplasty ( TKA ) remains a concern . Patient-specific instrumentation ( PSI ) produced using preoperative 3D models was developed to offer surgeons a simplified , reliable , efficient and customised TKA procedure . METHODS In this prospect i ve study , 60 patients underwent TKA with conventional instrumentation and 71 patients were operated on using PSI .  The primary endpoint was surgical time . Secondary endpoints included operating room ( OR ) time , the number of instrument trays used and postoperative radiographic limb alignment . RESULTS Compared to conventional instrumentation , PSI significantly reduced total surgical time by 8.9 ± 3.3 min ( p=0.038 ) , OR time by 8.6 ± 4.2 min ( p=0.043 ) , and the number of instrument trays by six trays ( p<0.001 ) . Mechanical axis malalignment of the lower limb of > 3 ° was observed in 13 % of PSI patients versus 29 % with conventional instrumentation ( p=0.043 ) . PSI predicted the size of the femoral and tibial components actually used in 85.9 % and 78.9 % of cases , respectively . CONCLUSION PSI  improves alignment , surgical and OR time , reduces the number of instruments trays used compared to conventional instrumentation in patients undergoing TKA and results in fewer outliers in overall mechanical alignment in the coronal plane . LEVEL OF EVIDENCE II Prospect i ve comparative therapeutic study 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 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 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 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 Abstract Purpose The aim of this prospect i ve study was to compare early clinical outcome , radiological limb alignment , and three-dimensional (3D)-component positioning between conventional and computed tomography (CT)-based patient-specific instrumentation ( PSI ) in primary mobile-bearing total knee arthroplasty ( TKA ) . Methods Two hundred ninety consecutive patients ( 300 knees ) with severe , debilitating osteoarthritis scheduled for TKA were included in this study using either conventional instrumentation ( CVI , n = 150 ) or PSI ( n = 150 ) . Patients were clinical ly assessed before and 2 years after surgery according to the Knee-Society-Score ( KSS ) and the visual-analog-scale for pain ( VAS ) . Additionally , the Western Ontario McMaster Universities Osteoarthritis Index ( WOMAC ) and the Oxford-Knee-Score ( OKS ) were collected at follow-up . To evaluate accuracy of CVI and PSI , hip-knee-ankle angle ( HKA ) and 3D-component positioning were assessed on postoperative radiographs and CT . Results Data of 222 knees ( CVI : n = 108 , PSI : n = 114 ) were available for analysis after a mean follow-up of 28.6 ± 5.2 months . At the early follow-up , clinical outcome ( KSS , VAS , WOMAC , OKS ) was comparable between the two groups . Mean HKA-deviation from the targeted neutral mechanical axis ( CVI : 2.2 ° ± 1.7 ° ; PSI : 1.5 ° ± 1.4 ° ; p < 0.001 ) , rates of outliers ( CVI : 22.2 % ; PSI : 9.6 % ; p = 0.016 ) , and 3D-component positioning outliers were significantly lower in the PSI group . Non-outliers ( HKA : 180 ° ± 3 ° ) showed better clinical results than outliers at the 2-year follow-up . Conclusions CT-based PSI compared with CVI improves accuracy of mechanical alignment restoration and 3D-component positioning in primary TKA . While clinical outcome was comparable between the two instrumentation groups at early follow-up , significantly inferior outcome was detected in the subgroup of HKA-outliers . Level of evidence Prospect i ve comparative study , Level II Purpose The aim of this study was to compare radiological results of total knee arthroplasties ( TKAs ) performed with patient-specific computed tomography (CT)-based instrumentation and conventional technique . The main study hypothesis was that CT-based patient-specific instrumentation ( PSI ) increases the accuracy of TKA . Methods A prospect i ve , r and omized controlled trial was carried out between January and December 2011 . A group of 112 patients who met the inclusion and exclusion criteria were enrolled in this study and r and omly assigned to an experimental or control group . The experimental group comprised 52 patients operated on with the aid of the Signature ™ CT-based implant positioning system .  The control group consisted of 60 patients operated on using conventional instrumentation .  The radiographic evaluation of implant positioning and overall coronal alignment was performed 12 months after the surgery by using st and ing anteroposterior radiographs of the entire lower limb and st and ard lateral radiographs . Results Of the 112 patients initially enrolled for the study , 95 were included in the subsequent analyses . There were no statistically significant differences between groups in respect to coronal and sagittal component positioning and overall coronal alignment , except for frontal tibial component positioning . For this parameter , better results were obtained in the control group , with borderline statistical significance . Conclusions Our study did not reveal superiority of the CT-based PSI system over conventional instrumentation . Further high- quality investigations of patient-specific systems are absolutely indispensable to assess their utility for TKA . In our opinion , the surgeon applying PSI technology is required to have advanced knowledge and considerable experience with the conventional method Patient specific instrumentation ( PSI ) was developed to increase total knee arthroplasty ( TKA ) accuracy and efficiency . The study purpose was to compare immediate post-operative mechanical alignment , achieved using PSI , with conventional and computer assisted surgery ( CAS ) instruments in high volume TKA practice s. This prospect i ve , multicenter , non-r and omized study accrued 66 TKA patients using PSI .  A computed tomography ( CT ) based algorithm was used to develop the surgical plan . Sixty-two percent were females , 99 % were diagnosed with osteoarthritis , average age at surgery was 66 years , and 33 was the average body mass index . A historical control group was utilized that underwent TKA using conventional instruments ( n=86 ) or CAS ( n=81 ) , by the same set of surgeons . Postoperative mechanical alignment was comparable across the groups . Operative time mean and variance were significant 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 Purpose This prospect i ve , double-blind , r and omised controlled trial was design ed to address the following research questions : firstly , is there a significant difference in outliers in alignment in the frontal and sagittal plane between PSG TKA and conventional TKA . Secondly , is there a significant difference in operation time , blood loss and length of hospital stay between the two techniques . We hypothesise that there will be fewer outliers with PSG TKA and that operation time , blood loss and length of hospital stay can be significantly reduced with PSG . Methods A total of 180 patients were r and omised for PSG TKA ( group 1 ) or conventional TKA ( group 2 ) in two centres . Patients were stratified per hospital . Alignment of the mechanical axis of the leg and flexion/extension and varus/valgus of the individual prosthesis components were measured on digital , st and ing , long-leg and st and ard lateral radiographs by two independent outcome assessors in both centres . Percentages of outliers ( > 3 ° ) were determined . We compared blood loss , operation time and length of hospital stay . Results There was no statistically significant difference in mean mechanical axis or outliers in mechanical axis between groups . No statistically significant difference was found for the alignment of the individual components in the frontal plane nor for the percentages of outliers . There was a statistically significant difference in outliers for the femoral component in the sagittal plane , with a higher percentage of outliers in the group 1 ( p = 0.017 ) . No such significant result was found for the tibial component in that plane . All interclass correlation coefficients were good . Blood loss was 100 mL less in group 1 ( p < 0.001 ) . Operation time was 5 min shorter in group 1 ( p < 0.001 ) . Length of hospital stay was identical with a mean of 3.6 days ( p = 0.657 ) . Conclusions The results in terms of obtaining a neutral mechanical axis and a correct position of the prosthesis components did not differ between groups . A small reduction in operation time and blood loss was found with the PSG system . Future research should especially focus on cost-effectiveness analysis and functional outcome of PSG TKA.Level of evidence Purpose The primary aim of the study was to examine stability and alignment after total knee arthroplasty ( TKA ) using patient-specific instrumentation ( PSI ) and conventional instrumentation ( CI ) . The hypothesis was that stability and alignment would be better using PSI than CI , 12 months postoperatively . The secondary aim included the evaluation of clinical outcomes after TKA . Methods In this prospect i ve r and omized controlled trial , 42 patients with knee osteoarthritis received a Genesis II PS prosthesis with either PSI or CI . Patients visited the hospital preoperatively and postoperatively after 6 weeks and 3 and 12 months . To evaluate stability , varus – valgus laxity was determined in extension and flexion using stress radiographs 12 months postoperatively . Three months postoperatively , a long-leg radiograph and CT scan were obtained to measure hip – knee – ankle ( HKA ) alignment and component rotation . Furthermore , frontal and sagittal alignment of the components , the Knee Society Score , VAS Pain , VAS Satisfaction , Knee injury and Osteoarthritis Outcome score , Patella score ( Kujala ) , University of California Los Angeles activity score , anterior – posterior laxity , ( serious ) adverse device-related events , and intraoperative complications were reported . The clinical outcomes were compared using independent t tests or non-parametric alternatives , and repeated measurements ANOVA with a significance level of p < 0.05 . Results No significant differences were found between the two groups regarding stability , HKA angle , and rotational alignment . In four patients , the PSI did not fit correctly on the tibia and /or femur requiring intraoperative modifications . Both groups improved significantly over time on all clinical outcomes , with no significant differences between the groups 12 months postoperatively . The PSI group showed less tibial slope than the patients in the CI group [ PSI 2.6 ° versus CI 4.8 ° ( p = 0.02 ) ] . Finally , the PSI group more frequently received a thinner insert size than the CI group ( p = 0.03 ) . Conclusions Patients operated with PSI did not differ from CI in terms of stability and alignment . However , in the PSI  group ligament releases were more often required intraoperatively . Furthermore , the two methods did not show different clinical results . It seems that the preoperative planning for the PSI facilitates more conservative bone cuts than CI , but whether this is clinical ly relevant should be investigated . Since PSI is more expensive and time consuming than CI , and does not outperform CI with regard to clinical results , we recommend to use CI.Level of evidence Background Component alignment can influence implant longevity as well as perhaps pain and function after unicompartmental knee arthroplasty ( UKA ) , but correct alignment is not consistently achieved . To increase the likelihood that good alignment will be achieved during surgery , smart tools such as robotics or patient-specific instrumentation ( PSI ) have been introduced . Questions / purpose sWe hypothesized that UKA performed with PSI would result in improved level gait as ascertained with three-dimensional analysis , implant positioning , and patient-reported outcomes measured by a vali date d scoring system when compared with conventional instrumentation 3 months and 1 year after surgery . Methods We r and omized 60 patients into two groups using either the PSI technique or a conventional technique .  All patients were operated on using the same technique and the same cemented metal-backed implant . Mean age of the patients was 63 ± 4 years ( range , 54–72 years ) and mean body mass index was 28 ± 3 kg/m2 . Patients were evaluated preoperatively , at 3 months , and 1 year after surgery by an independent observer blind to the type of technique . Gait parameters were assessed with three-dimensional analysis during level walking preoperatively and at 1 year , frontal and sagittal position of the implant was evaluated on full-length radiographs at 3 months , and subjective functional outcome and quality of life using routine question naires ( SF-12 , new Knee Society Score [ KSS ] , Knee Injury and Osteoarthritis Outcome Score ) at 3 months and 1 year . This study had 80 % power to detect a 15 % difference in walking speed at the p < 0.05 level . Results One year after surgery , there were no differences between the two groups in the analyzed gait spatiotemporal parameters , respectively , for PSI UKA and conventional UKA : double limb support 31 % ( 25%–54 % ) versus 30 % ( 23%–56 % ; p = 0.67 ) and walking speed ( 1.59 m/s [ 0.86–1.87 m/s ] versus 1.57 m/s [ 0.71–1.96 m/s ] ; p = 0.41 ) . No difference was observed between the two groups in terms of lower limb alignment  ( PSI group 178 ° ± 3 ° , conventional group 178 ° ± 4 ° ; p = 0.24 ) or implant positioning on mediolateral and anteroposterior radiographs . There were no differences in the functional score between the PSI and conventional TKA groups at 3 months and 1 year after surgery : KSS objective knee scores ( PSI : 85 ± 8 points at 3 months , 87 ± 5 points at 1 year and conventional instrumentation : 82 ± 8 points at 3 months 83 ± 6 points at 1 year ; p = 0.10 ) and functional activity scores were similar in both group ( PSI : 71 ± 12 points at 3 months and 74 ± 7 points at 1 year versus conventional group : 73 ± 11 points at 3 months and 75 ± 6 at 1 year ; p = 0.9 ) . Conclusions Our observations suggest that PSI may confer small , if any , advantage in alignment , pain , or function after UKA . This argument can therefore not be used to justify the extra cost and uncertainty related to this technique . Level of Evidence Level I , therapeutic study 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 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 In this study we r and omised 140 patients who were due to undergo primary total knee arthroplasty ( TKA ) to have the procedure performed using either patient-specific cutting guides ( PSCG ) or conventional instrumentation ( CI ) . The primary outcome measure was the mechanical axis , as measured at three months on a st and ing long-leg radiograph by the hip-knee-ankle ( HKA ) angle . This was undertaken by an independent observer who was blinded to the instrumentation . Secondary outcome measures were component positioning , operating time , Knee Society and Oxford knee scores , blood loss and length of hospital stay . A total of 126 patients ( 67 in the CI group and 59 in the PSCG group ) had complete clinical and radiological data . There were 88 females and 52 males with a mean age of 69.3 years ( 47 to 84 ) and a mean BMI of 28.6 kg/m(2 ) ( 20.2 to 40.8 ) .  The mean HKA angle was 178.9 ° ( 172.5 to 183.4 ) in the CI group and 178.2 ° ( 172.4 to 183.4 ) in the PSCG group ( p = 0.34 ) . Outliers were identified in 22 of 67 knees ( 32.8 % ) in the CI group and 19 of 59 knees ( 32.2 % ) in the PSCG group ( p = 0.99 ) . There was no significant difference in the clinical results ( p = 0.95 and 0.59 , respectively ) . Operating time , blood loss and length of hospital stay were not significantly reduced ( p = 0.09 , 0.58 and 0.50 , respectively ) when using PSCG . The use of PSCG in primary TKA did not reduce the proportion of outliers as measured by post-operative coronal alignment 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 Background Despite the growing evidence in the literature there is still a lack of consensus regarding the use of minimally invasive surgical technique ( MIS ) in total knee arthroplasty ( TKA ) . Methods A prospect i ve , r and omized , international multicentre trial including 69 patients was performed to compare computer-assisted TKA ( CAS-TKA ) using either mini-midvastus ( MIS group ) or st and ard medial parapatellar approach ( conventional group ) .  Patients from 3 centers ( Maastricht , Zwickau , Adelaide ) with end-stage osteoarthritis of the knee were r and omized to either an MIS group with dedicated instrumentation or a conventional group to receive cruciate retaining CAS-TKA without patella resurfacing .  The primary outcome was to compare post operative pain and range of motion ( ROM ) . The secondary outcome was to measure the duration of surgery , blood loss , chair rise test , quadriceps strength , anterior knee pain , Knee Society Score (KSS),WOMAC scores , mechanical leg axis and component alignment . Results Patients in the MIS group ( 3.97 ± 2.16 ) had significant more pain at 2 weeks than patients in the conventional group ( 2.77 ± 1.43 ) p = 0.003 . There was no significant difference in any of the other primary outcome parameters . Surgery time was significantly longer ( p < 0.001 ) and there were significantly higher blood loss ( p = 0.002 ) in the MIS group as compared to the conventional group . The difference of the mean mechanical leg alignment between the groups was not statistically significant ( –0.43 ° ( 95 % CI –1.50 – 0.64 ) ; p = 0.43).There was no significant difference of component alignment between the two surgical groups with respect to flexion/extension ( p = 0.269 ) , varus/valgus ( p = 0.653 ) or rotational alignment ( p = 0.485 ) of the femur component and varus valgus alignment ( p = 0.778 ) or posterior slope ( p = 0.164 ) of the tibial component . Conclusion There was no advantage of the MIS approach compared to a conventional approach CAS-TKA in any of the primary outcome measurements assessed , however the MIS approach was associated with longer surgical time and greater blood loss . MIS-TKA in combination with computer navigation is safe in terms of implant positioning . Trial registration number Clinical Trials.gov NCT02625311 8 December BACKGROUND The purpose of this study was to assess whether custom cutting blocks improve accuracy of component alignment compared to conventional TKA instrumentation . METHODS Eighty primary TKA patients were enrolled in an open-label r and omized prospect i ve clinical trial and were divided into two groups , 40 custom cutting blocks and 40 conventional TKA instrumentations . The primary outcome was prosthetic alignment with respect to mechanical axis and epicondylar axis . Secondary outcomes included operative time , 24-hour postoperative blood loss and hemoglobin at discharged . RESULTS There were no statistical significant differences in the postoperative mechanical axis between the custom cutting blocks group and conventional TKA group , ( 95 % vs. 87.5 % within 3 ° of neutral mechanical alignment , p=0.192 ) . The average rotational alignment was statistically significantly different in the custom cutting blocks group ( 1.0 ° ±0.6 ° vs. 1.6 ° ±1.8 ° external rotation from epicondylar axis , p<0.001 ) . There were statistical significant differences in operation time  between custom cutting blocks group and conventional group , skin to skin [ 57.5±2.3 min vs. 62.1±1.5 , p<0.001 ] . We found an improvement in group 1 compared with group 2 regarding the proportion of patients with postoperative blood loss within 24 h. CONCLUSIONS Custom cutting blocks technique was a surgical procedure which provided better accuracy in rotational alignment but no statistical differences in mechanical axis , less operative time and reduced blood loss  than the conventional TKA instrumentation in the majority of patients While patient-specific instrumentation ( PSI ) in total knee arthroplasty ( TKA ) allows for transfer of the preoperative plan onto bony l and marks , the soft tissue balancing is not affected . The goals of this r and omized clinical trial were to compare PSI and the measured resection technique ( conventional ) with PSI and the gap balancing technique .  Fifty patients were r and omized to TKA with conventional PSI ( PSI-S ) ( n = 25 ) or to PSI with additional gap balancing ( PSI-GB ) ( n = 25 ) . All patients were clinical ly examined at 3 and 12 months postoperatively . Data on the range of motion , the Knee Society Score , the Western Ontario and McMasters Universities Osteoarthritis Index , the High-Flexion Knee Score ( HFKS ) , and the Forgotten Joint Score ( FJS ) were compiled at follow-up . Statistically significant improvements were found for all clinical parameters in the PSI-GB group compared to the PSI-S group at 3 months postoperatively and for FS , FJS , and HFKS at 12 months . However , the relevance of these differences , as well as their effect on long-term outcomes , needs to be evaluated further . In conclusion , patient-specific instrumentation combined with gap balancing yielded good early clinical outcomes 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 Background Recently , patient-specific guides ( PSGs ) have been introduced , cl aim ing a significant improvement in accuracy and reproducibility of component positioning in TKA . Despite intensive marketing by the manufacturers , this cl aim has not yet been confirmed in a controlled prospect i ve trial . Questions / purpose sWe ( 1 ) compared three-planar component alignment and overall coronal mechanical alignment between PSG and conventional instrumentation and ( 2 ) logged the need for applying changes in the suggested position of the PSG . Methods In this r and omized controlled trial , we enrolled 128 patients . In the PSG cohort , surgical navigation was used as an intraoperative control . When the suggested cut deviated more than 3 ° from target , the use of PSG was ab and oned and marked as an outlier . When cranial-caudal position or size was adapted , the PSG was marked as modified . All patients underwent long-leg st and ing radiography and CT scan .  Deviation of more than 3 ° from the target in any plane was defined as an outlier . Results The PSG and conventional cohorts showed similar numbers of outliers in overall coronal alignment ( 25 % versus 28 % ; p = 0.69 ) , femoral coronal alignment ( 7 % versus 14 % ) ( p = 0.24 ) , and femoral axial alignment ( 23 % versus 17 % ; p = 0.50 ) . There were more outliers in tibial coronal ( 15 % versus 3 % ; p = 0.03 ) and sagittal 21 % versus 3 % ; p = 0.002 ) alignment in the PSG group than in the conventional group . PSGs were ab and oned in 14 patients ( 22 % ) and modified in 18 ( 28 % ) . Conclusions PSGs do not improve accuracy in TKA and , in our experience , were somewhat impractical in that the procedure needed to be either modified or ab and oned with some frequency . Level of Evidence Level I , therapeutic study . See instructions for authors for a complete description of levels of evidence BACKGROUND Patient-specific femoral and tibial cutting blocks produced with use of data from preoperative computed tomography ( CT ) or magnetic resonance imaging ( MRI ) scans have been employed recently to optimize component alignment in total knee arthroplasty . We report the results of a r and omized controlled trial in which CT scans were used to compare postoperative component alignment between patients treated with custom instruments  and those managed with traditional instruments . METHODS The in-hospital data and early clinical outcomes , including Knee Society scores , were determined in a r and omized clinical trial of forty-seven patients who had undergone a total of forty-eight primary total knee arthroplasties with patient-specific instruments ( twenty-two knees ) or st and ard instruments ( twenty-six knees ) . Orientation of the implants was compared by using three-dimensional CT data . RESULTS No significant differences were found between the study and control groups with respect to any clinical outcome after a minimum of six months of follow-up . The patient-specific tibial cutting block was ab and oned in favor of a st and ard external alignment jig in seven of the twenty-two study knees because of possible malalignment . A detailed analysis of intent-to-treat and per- protocol groups of study and control knees did not show any significant improvement in component alignment , including femoral component rotation in the axial plane , in the patients treated with the custom instruments . The percentage of outliers -- defined as less than -3 ° or more than 3 ° from the correct orientation of the tibial slope -- was significantly higher in the group treated with use of patient-specific blocks than it was in the control group , in both the intent-to-treat ( 32 % versus 8 % , p = 0.032 ) and the per- protocol ( 47 % versus 6 % , p = 0.0008 ) analysis . CONCLUSIONS There were no significant improvements in clinical outcomes or knee component alignment in patients treated with patient-specific cutting blocks as compared with those treated with st and ard instruments . The group treated with patient-specific cutting blocks had a significantly higher prevalence of malalignment in terms of tibial component slope than the knees treated with st and ard instruments
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 .