Patient-specific computed tomography based instrumentation in total knee arthroplasty: a prospective randomized controlled study Stability and alignment do not improve by using patient-specific instrumentation in total knee arthroplasty: a randomized controlled trial Reliability of templating with patient-specific instrumentation in total knee arthroplasty. In-vivo alignment comparing patient specific instrumentation with both conventional and computer assisted surgery (CAS) instrumentation in total knee arthroplasty. The radiological outcomes of patient-specific instrumentation versus conventional total knee arthroplasty Patient-specific instrumentation improved mechanical alignment, while early clinical outcome was comparable to conventional instrumentation in TKA Comparison between patient-specific instruments and conventional instruments and computer navigation in total knee arthroplasty: a randomized controlled trial Improved alignment and operating room efficiency with patient-specific instrumentation for TKA. Component alignment and clinical outcome following total knee arthroplasty: a randomised controlled trial comparing an intramedullary alignment system with patient-specific instrumentation. Rotation in total knee arthroplasty: no difference between patient-specific and conventional instrumentation Small Improvements in Mechanical Axis Alignment Achieved With MRI versus CT-based Patient-specific Instruments in TKA: A Randomized Clinical Trial Kinematic femoral alignment with gap balancing and patient-specific instrumentation in total knee arthroplasty: a randomized clinical trial Patient-specific instrumentation in total knee arthroplasty: simpler, faster and more accurate than standard instrumentation—a randomized controlled trial Patient-specific instrumentation does not shorten surgical time: a prospective, randomized trial. Implant positioning in TKA: comparison between conventional and patient-specific instrumentation. The John Insall Award: No Functional Benefit After Unicompartmental Knee Arthroplasty Performed With Patient-specific Instrumentation: A Randomized Trial A radiological analysis of the difference between MRI- and CT-based patient-specific matched guides for total knee arthroplasty from the same manufacturer: a randomised controlled trial. Patient specific cutting blocks are currently of no proven value. No radiological and clinical advantages with patient-specific positioning guides in total knee replacement Optimization of imaging diagnosis of 1-2 cm hepatocellular carcinoma: an analysis of diagnostic performance and resource utilization. Patient-specific instrumentation for total knee arthroplasty does not match the pre-operative plan as assessed by intra-operative computer-assisted navigation No improvement in reducing outliers in coronal axis alignment with patient-specific instrumentation A comparison of patient-specific and conventional instrumentation for total knee arthroplasty: a multicentre randomised controlled trial.
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 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 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 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 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 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 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 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 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 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 in TKA has the proposed benefits of improving coronal and sagittal alignment and rotation of the components . In contrast , the literature is inconsistent if the use of patient-specific instrumentation improves alignment in comparison to conventional instrumentation . Depending on the manufacturer , patient-specific instrumentation is based on either MRI or CT scans . However , it is unknown whether one patient-specific instrumentation approach is more accurate than the other and if there is a potential benefit in terms of reduction of duration of surgery . Questions / purpose sWe compared the accuracy of MRI- and CT-based patient-specific instrumentation with conventional instrumentation and with each other in TKAs . The three approaches also were compared with respect to vali date d outcomes scores and duration of surgery . Methods A r and omized clinical trial was conducted in which 90 patients were enrolled and divided into three groups :  CT-based , MRI-based patient-specific instrumentation , and conventional instrumentation . The groups were not different regarding age , male/female sex distribution , and BMI . In all groups , coronal and sagittal alignments were measured on postoperative st and ing long-leg and lateral radiographs . Component rotation was measured on CT scans . Clinical outcomes ( Knee Society and WOMAC scores ) were evaluated preoperatively and at a mean of 3 months postoperatively and the duration of surgery was analyzed for each patient . MRI- and CT-based patient-specific instrumentation groups were first compared with conventional instrumentation , the patient-specific instrumentation groups were compared with each other , and all three approaches were compared for clinical outcome measures and duration of surgery . Results Compared with conventional instrumentation MRI- and CT-based patient-specific instrumentation showed higher accuracy regarding the coronal limb axis ( MRI versus conventional , 1.0 ° [ range , 0 ° –4 ° ] versus 4.5 ° [ range , 0 ° –8 ° ] , p < 0.001 ; CT versus conventional , 3.0 ° [ range , 0 ° –5 ° ] versus 4.5 ° [ range , 0 ° –8 ° ] , p = 0.02 ) , femoral rotation ( MRI versus conventional , 1.0 ° [ range , 0 ° –2 ° ] versus 4.0 ° [ range , 1 ° –7 ° ] , p < 0.001 ; CT versus conventional , 1.0 ° [ range , 0 ° –2 ° ] versus 4.0 ° [ range , 1 ° –7 ° ] , p < 0.001 ) , and tibial slope ( MRI versus conventional , 1.0 ° [ range , 0 ° –2 ° ] versus 3.5 ° [ range , 1 ° –7 ° ] , p < 0.001 ; CT versus conventional , 1.0 ° [ range , 0 ° –2 ° ] versus 3.5 ° [ range , 1 ° –7 ° ] , p < 0.001 ) , but the differences were small . Furthermore , MRI-based patient-specific instrumentation showed a smaller deviation in the postoperative coronal mechanical limb axis compared with CT-based patient-specific instrumentation ( MRI versus CT , 1.0 ° [ range , 0 ° –4 ° ] versus 3.0 ° [ range , 0 ° –5 ° ] , p = 0.03 ) , while there was no difference in femoral rotation or tibial slope . Although there was a significant reduction of the duration of surgery in both patient-specific instrumentation groups in comparison to conventional instrumentation ( MRI versus conventional , 58 minutes [ range , 53–67 minutes ] versus 76 minutes [ range , 57–83 minutes ] , p < 0.001 ; CT versus conventional , 63 minutes [ range , 59–69 minutes ] versus 76 minutes [ range , 57–83 minutes ] , p < .001 ) , there were no differences in the postoperative Knee Society pain and function and WOMAC scores among the groups . Conclusions Although this study supports that patient-specific instrumentation increased accuracy compared with conventional instrumentation and that MRI-based patient-specific instrumentation is more accurate compared with CT-based patient-specific instrumentation regarding coronal mechanical limb axis , differences are only subtle and of question able clinical relevance . Because there are no differences in the long-term clinical outcome or survivorship yet available , the widespread use of this technique can not be recommended . Level of Evidence Level I , therapeutic study . See the Instructions to Authors for a complete description of levels of evidence 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 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 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 The number of total knee arthroplasty ( TKA ) procedures continuously increases , with good to excellent results . In the last few years , new surgical techniques have been developed to improve prosthesis positioning . In this context , patient-specific instrumentation is included . The goal of this study was to compare the perioperative parameters and the spatial positioning of prosthetic components in TKA procedures performed with patient-specific instrumentation vs traditional TKA . In this prospect i ve comparative r and omized study , 15 patients underwent TKA with 3-dimensional magnetic resonance imaging ( MRI ) preoperative planning ( patient-specific instrumentation group ) and 15 patients underwent traditional TKA ( non-patient-specific instrumentation group ) . All patients underwent postoperative computed tomography ( CT ) examination .  In the patient-specific instrumentation group , preoperative data planning regarding femoral and tibial bone resection was correlated with intraoperative measurements . Surgical time , length of hospitalization , and intraoperative and postoperative bleeding were compared between the 2 groups . Positioning of implants on postoperative CT was assessed for both groups . Data planned with 3-dimensional MRI regarding the depth of bone cuts showed good to excellent correlation with intraoperative measurements . The patient-specific instrumentation group showed better perioperative outcomes and good correlation between the spatial positioning of prosthetic components planned preoperatively and that seen on postoperative CT . Less variability was found in the patient-specific instrumentation group than in the non-patient-specific instrumentation group in spatial orientation of prosthetic components . Preoperative planning with 3-dimensional MRI in TKA has a better perioperative outcome compared with the traditional method . Use of patient-specific instrumentation can also improve the spatial positioning of both prosthetic components 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 AIMS This prospect i ve r and omised controlled trial was design ed to evaluate the outcome of both the MRI- and CT-based patient-specific matched guides ( PSG ) from the same manufacturer . PATIENTS AND METHODS A total of 137 knees in 137 patients ( 50 men , 87 women ) were included , 67 in the MRI- and 70 in the CT-based PSG group . Their mean age was 68.4 years ( 47.0 to 88.9 ) . Outcome was expressed as the biomechanical limb alignment ( centre hip-knee-ankle : HKA-axis ) achieved post-operatively , the position of the individual components within 3 ° of the pre-operatively planned alignment , correct planned implant size and operative data ( e.g. operating time and blood loss ) . RESULTS The patient demographics ( e.g. age , body mass index ) , correct planned implant size and operative data were not significantly different between the two groups . The proportion of outliers in the coronal and sagittal plane ranged from 0 % to 21 % in both groups . Only the number of outliers for the posterior slope of the tibial component showed a significant difference ( p = 0.004 ) with more outliers in the CT group ( n = 9 , 13 % ) than in the MRI group ( 0 % ) . CONCLUSION The post-operative HKA-axis was comparable in the MRI- and CT-based PSGs , but there were significantly more outliers for the posterior slope in the CT-based PSGs . TAKE HOME MESSAGE Alignment with MRI-based PSG is at least as good as , if not better , than that of the CT-based PSG , and is the preferred imaging modality when performing TKA with use of PSG . Cite this article : Bone Joint J 2016;98-B:786 - 92 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 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 BACKGROUND & AIMS To determine the optimal imaging scan or combinations in terms of diagnostic performance and re source utilization for 1 - 2 cm nodules found on surveillance for hepatocellular carcinoma . METHODS Eighty-four cirrhotic patients with 101 , 1 - 2 cm nodules ( 34 malignant , 67 non-malignant ) prospect ively underwent st and ardized contrast-enhanced ultrasound , CT , and MRI scans .  Sensitivity/specificity and potential imaging/biopsy utilization of individual imaging modalities and two-modality combinations performed at the same time ( coincidental ) or in sequence were measured . Final diagnosis was determined by biopsy ( 23 ) , growth ( 10 ) , recurrence ( 1 ) , or stability in size for ≥ 18 months ( 67 ) . RESULTS For single imaging scans , sensitivities/specificities ranged between 53 - 62 % and 91 - 100 % . When two scans were combined requiring both to be positive , sensitivities/specificities ranged between 29 - 41 % and 99 - 100 % . When two scans were combined sequentially , requiring only one to be positive , sensitivities/specificities ranged between 74 - 89 % and 91 - 99 % . When comparing combination of two positive tests ( MRI and CT ) to MRI alone , there was a significant drop in sensitivity ( 41 % vs. 62 % , p=0.02 ) , no change in specificity ( both 100 % ) , with twice as many scans performed , and 9 % rise in potential biopsies or 7 % rise in follow-up scans . When comparing the combination of MRI then CT ( if MRI negative ) to MRI alone , there was an insignificant rise in sensitivity ( 74 % vs. 62 % , p=0.13 ) , drop in specificity ( 97 % vs. 100 % ) , with 77 % more scans performed , and 6 % drop in potential biopsies or 7 % drop in potential follow-up scans . CONCLUSIONS Single imaging scans have similar specificity to two coincidental positive scans with much less re source utilization . Sequential imaging provides the best sensitivity but with diminished specificity 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 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 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
There were no significant differences regarding the biomechanical axis or frontal femoral and individual tibial component alignment .
Conclusion This systematic review and meta- analysis demonstrate that alignment with MRI-based PSI is at least as good as , if not better than , that with CT-based PSI .
Purpose Patient-specific instruments ( PSIs ) are already in relatively common use , and their post-operative radiographic results are equal to those for total knee arthroplasty ( TKA ) with conventional instrumentation .
PSI use requires a preoperative MRI scan , CT scan , or a combination of MRI and a long-leg st and ing radiograph .
However , there is no consensus as to which of these modalities , MRI or CT , is the preferred imaging modality when performing TKA with PSIs .