title: Inter-observer reliability of measurements performed on digital long-leg standing radiographs and assessment of validity compared to 3D CT-scan. Patient-specific instrumentation improves tibial component rotation in TKA Rotation in total knee arthroplasty: no difference between patient-specific and conventional instrumentation 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. Accuracy of CT-based patient-specific guides for total knee arthroplasty in patients with post-traumatic osteoarthritis Patient-matched instruments versus standard instrumentation in total knee arthroplasty: a prospective randomized study Intra-operative results and radiological outcome of conventional and patient-specific surgery in total knee arthroplasty: a multicentre, randomised controlled trial Patient-specific instrumentation does not shorten surgical time: a prospective, randomized trial. Reliability of templating with patient-specific instrumentation in total knee arthroplasty. Comparison between patient-specific instruments and conventional instruments and computer navigation in total knee arthroplasty: a randomized controlled trial Patient-specific computed tomography based instrumentation in total knee arthroplasty: a prospective randomized controlled study Patient-specific total knee arthroplasty: the importance of planning by the surgeon 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. Implant positioning in TKA: comparison between conventional and patient-specific instrumentation. Small Improvements in Mechanical Axis Alignment Achieved With MRI versus CT-based Patient-specific Instruments in TKA: A Randomized Clinical Trial Patient specific cutting blocks are currently of no proven value. The accuracy of component alignment in custom cutting blocks compared with conventional total knee arthroplasty instrumentation: prospective control trial. A prospective randomised controlled study of patient-specific cutting guides compared with conventional instrumentation in total knee replacement. Is TKA Using Patient-specific Instruments Comparable to Conventional TKA? A Randomized Controlled Study of One System
abstract: BACKGROUND Long-leg radiographs ( LLR ) are often used in orthopaedics to assess limb alignment in patients undergoing total knee arthroplasty ( TKA ) . However , there are still concerns about the adequacy of measurements performed on LLR . We assessed the reliability and validity of measurements on LLR using three-dimensional computed tomography ( 3D CT)-scan as a gold st and ard . METHODS Six different surgeons measured the mechanical axis and position of the femoral and tibial components individually on 24 LLR .  Intraclass correlation coefficients ( ICC ) were calculated to obtain reliability and Bl and -Altman plots were constructed to assess agreement between measurements on LLR and measurements on 3D CT-scan . RESULTS ICC agreement for the six observer measurements on LLR was 0.70 for the femoral component and 0.80 for the tibial component . The mean difference between measurements performed on LLR and 3D CT-scan was 0.3 ° for the femoral component and -1.1 ° for the tibial component . Variation of the difference between LLR and 3D CT-scan for the femoral component was 1.1 ° and 0.9 ° for the tibial component . 95 % of the differences between measurements performed on LLR and 3D CT-scan were between -1.9 and 2.4 ° ( femoral component ) and between -2.9 and 0.7 ( tibial component ) . CONCLUSION Measurements on LLR show moderate to good reliability and , when compared to 3D CT-scan , show good validity . CLINICAL TRIAL REGISTRATION NUMBER institutional review board Atrium-Orbis-Zuyd , number : 11-T-15 . LEVEL OF EVIDENCE Prospect i ve cohort study , Level II Purpose To compare the femoral and tibial components rotational alignment in total knee arthroplasty ( TKA ) performed either with conventional or with patient-specific instrumentation . Methods Forty-five patients underwent primary TKA and were prospect ively r and omized into two groups : 22 patients into the conventional instrumentation group ( group A ) and 23 patients into the Signature ™ patient-specific instrumentation group ( group B ) . All patients underwent computed tomography of the operated knee in the first week after surgery to measure  the components rotation . Results The femoral component rotation was 0.0 ° ( −0.25 , 1.0 ) in group A , and 0.0 ° ( 0.0 , 1.0 ) in group B. The tibial component rotation was −16.0 ° ( −18.5 , 11.8 ) in group A , and −16.0 ° ( −19.0 , −14.0 ) in group B. There were no significant differences between the two groups in tibial and femoral components rotation . The difference between the tibial component rotation and the neutral tibial rotation was similar in both groups [ 2.0 ° ( −0.5 , 6.3 ) in group A and 2.0 ° ( −1.0 , 4.0 ) in group B ] , but the dispersion around the median was different between the two groups . The amplitude of the difference between tibial rotation and neutral position was 27 ° ( −13 , 14 ) in group A and 9 ° ( −3 , 6 ) in group B. Conclusions There is a smaller chance of internal malrotation of the tibial component with the Signature ™ patient-specific instrumentation system , with less dispersion and amplitude of the tibial component rotation around the neutral position . Level of evidence II Abstract Purpose It was our hypothesis that patient-specific instrumentation ( PSI ) can improve the accuracy of the rotational alignment in TKA based on the concept of the system and on the potential to clearly identify pre-operatively during planning the classical anatomical l and marks that serve as references to set-up the rotation both for the femur and tibia . Material s and methods In this prospect i ve comparative r and omized study , 40 patients ( 20 in each group ) operated in our institution between September 2012 and January 2013 by the 2 senior authors were included . R and omization of patients into one of the two groups was done by the Hospital Informatics Department with the use of a systematic sampling method . All patients received the same cemented high-flex mobile bearing TKA . In the PSI group , implant position was compared to the planed position using previously vali date d dedicated software . The position of the implants ( frontal and sagittal ) was compared in the 2 groups on st and ard X-rays , and the rotational position was analysed on post-operative CT-scan . Results 90 % of the patients add < 2 ° or mm of difference between the planned position of the implants and the obtained position , except for the tibial rotation where the variations were much higher . Mean HKA was 179 ° ( 171–185 ) in the PSI group with 4 outliers ( 2 varus : 171 ° and 172 ° :184 ° and 185 ° ) and 178.3 ° with 2 outliers ( 171 ° and 176 ° ) in the control group . No difference was observed between the two groups concerning the frontal and sagittal position of the implants on the ML and AP X-rays . No significant difference of femoral rotation was observed between the two groups with a mean of 0.4 ° in the PSI group and 0.2 ° in the control group ( p : n.s ) . Mean tibial rotation was 8 ° of internal rotation in the PSI group and 15 ° of internal rotation in the st and ard group ( p : n.s ) . Conclusion Based on our results , we were unable to confirm our hypothesis as PSI can not improve rotation in TKA . More work needs to be done to more clearly define the place of PSI in TKA , to keep on improving the accuracy of the system and to better define the individual targets in TKA in terms of frontal , sagittal and rotational positioning of the implant for each patient . Level of evidence Prospect i ve comparative r and omized study , Level II Background 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 Abstract Published clinical trials who studied the accuracy of patient-specific guides ( PSG ) for total knee arthroplasty exclude patients with articular deformity of the knee joint . We prospect ively analysed a series of 30 patients with post-traumatic osteoarthritis of the knee joint with use of PSG . At 1 year post-operative , the achieved biomechanical ( HKA ) axis and varus/valgus of the femur and tibia components were measured on anterior – posterior ( AP ) long-st and ing weight-bearing radiographs . Flexion/extension of the femoral and AP slope of the tibia component was measured on st and ard lateral radiographs . Percentages > 3 ° deviation of the pre-operative planned HKA axis and individual implant components were considered as outliers . Approved and used implant size , median blood loss ( ml ) and operation time ( min ) were obtained from the operation records . Pre- and 1-year post-operative patient-reported outcome measures ( PROMs ) were performed . Eighty-three per cent of the patients had a HKA axis restored <3 ° of the pre-operative planned alignment . Varus/valgus outliers were 0.0 and 6.7 % for the femoral and tibial components , respectively . Percentages of outliers of flexion/extension were 36.7 % for the femoral component and 10.0 % for the AP slope of the tibial component . Median blood loss was 300 ml ( 50–700 ) , while operation time was 67 min ( 44–144 ) . In 20 % of all cases , the approved implant size was changed into one size smaller . One-year post-operative PROMs improved significantly . We conclude that the accuracy of CT-based PSG is not impaired in patients with post-traumatic osteoarthritis and this modality can restore biomechanical limb 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 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 The primary purpose of this prospect i ve , r and omized study was to determine if patient-specific instrumentation ( PSI ) for total knee arthroplasty ( TKA ) shortened surgical time . Secondarily the number of instrument trays and alignment were also compared to cases performed with traditional instrumentation ( TI ) .  Fifty-two cases ( 26 per group ) were r and omized and videotaped to measure the length of surgery , as well as each individual surgical step . Component alignment and mechanical axis was measured radiographically for each patient . Total surgical time was over 4 minutes shorter for patients in the TI group ( 57.4 minutes vs. 61.8 minutes ; P<0.01 ) . More instrument trays were used in the TI group ( 7.3 vs. 2.5 ; P<0.001 ) . There was no significant difference in mechanical alignment between groups on postoperative long alignment radiographs ( P=0.77 ) . In conclusion , PSI did not shorten surgical time or improve alignment compared with TI in this prospect i ve , r and omized trial , but did reduce the required number of trays Magnetic resonance imaging ( MRI ) or computed tomography-based patient-specific instrumentation ( PSI ) may allow for reliable alignment and fewer outliers when compared with conventionally instrumented total knee arthroplasty ( TKA ) . However , some authors have suggested that frequent intraoperative surgeon-directed changes may still be required . This study evaluated the accuracy of  PSI  to predict component sizing and alignment during TKA . A total of 84 patients ( 89 knees ) who underwent a TKA using a PSI system were evaluated . An MRI-based preoperative plan of every knee was provided and approved by the surgeons . This demonstrated the proposed prosthetic component alignment , as well as the femoral , tibial , and bearing insert component size and position . Intraoperative changes to these components were prospect ively recorded and compared with the computerized preoperative plan . Major changes were defined as any changes in femoral or tibial resection , size , and position of the components . Minor changes were defined as any change in the size of the polyethylene bearing insert . The preoperative plan was able to correctly predict the size of the implanted tibial and femoral component in 93 and 95.5 % of the cases , respectively . Thirteen major intraoperative changes were made . In one knee , the proposed femoral resection was not acceptable ( because of the presence of significant amount of osteophytes ) and was ab and oned in favor of a manual extramedullary guide . In another patient , the proposed femoral and tibial components were upsized . In two other patients , the femoral components were downsized , in four patients , the tibial components were downsized , and in another patient , it was upsized . There were also 16 minor changes , which included 2-mm upsizing of the polyethylene liner in 13 knees and 4-mm upsizing in 3 knees . Surgical experience is necessary to recognize improper component size , incorrect surgical resection , or nonideal alignment when performing TKA using PSI . The authors believe that the design and manufacture of PSI combined with a comprehensive templating result ed in excellent intraoperative concordance of the preoperative plan at the default setting s with minimal changes Abstract Purpose The 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 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 Abstract Purpose The purpose of the study was to evaluate the accuracy of the planning of the patient-specific pin guides in total knee arthroplasty ( TKA ) . This planning was performed primarily by a technician of the company and offered to the surgeon . All parameters of the implantation can either be modified or accepted by the surgeon . The hypothesis was that the plan needs preoperative intervention by the surgeon . Methods A prospect i ve study in 50 patients was carried out . All patients received the same posterior-stabilised implant with patient-specific instrumentation . All surgical parameters ( coronal , sagittal , rotational alignment , femoral and tibial resection levels and implant sizes ) were checked by the orthopaedic surgeon and changed if necessary . Results Preoperatively , the femoral size was changed in 8 patients ( 16 % ) , the femoral flexion in 23 patients ( 46 % ) , the femoral shift in 34 patients ( 68 % ) , the tibial size in 24 patients ( 48 % ) and the tibial rotation in all patients . The epicondylar axis was accepted in 47 patients ( 94 % ) in the technician plan . Mean planning time was 8 ± 4 min . Intraoperatively , the femoral anterior – posterior size was in 50 patients ( 100 % ) the same as in the surgeon and in 42 patients ( 84 % ) the same as in the technician plan ( p = 0.003 ) . The tibial component implanted was in 42 patients ( 84 % ) the same as in the surgeon and in 19 patients ( 38 % ) the same as in the technician plan ( p < 0.0001 ) . A femoral distal recut was necessary in 31 patients ( 62 % ) and a change of the tibial proximal cut in 17 patients ( 34 % ) during surgery . Intraoperatively , no changes of the femoral and tibial alignment , the femoral anterior – posterior size , the femoral flexion , the femoral shift , the femoral and tibial rotation were necessary . Postoperatively , the coronal mechanical overall axis was within ±3 ° in 47 patients ( 94 % ) with a maximum deviation of 5.6 ° . Conclusions Significant changes of the technician plan were necessary to get an accurate preoperative plan . Intraoperative changes were significant less compared to the surgeon than to the technician plan . No major changes ( alignment , femoral anterior – posterior size and rotation ) of the surgeon plan were necessary . Surgeons using patient-specific pin guides in TKA may verify the default plan provided by the technician . A blind reply on the technician plan may be not recommended . Level of evidence Therapeutic study , Level III 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 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 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 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 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 Patient-specific cutting guides ( PSCGs ) are design ed to improve the accuracy of alignment of total knee replacement ( TKR ) . We compared the accuracy of limb alignment and component positioning after  TKR  performed using PSCGs or conventional instrumentation . A total of 80 patients were r and omised to undergo TKR with either of the different forms of instrumentation , and radiological outcomes and peri-operative factors such as operating time were assessed . No significant difference was observed between the groups in terms of tibiofemoral angle or femoral component alignment . Although the tibial component in the PSCGs group was measurably closer to neutral alignment than in the conventional group , the size of the difference was very small ( 89.8 ° ( sd 1.2 ) vs 90.5 ° ( sd 1.6 ) ; p = 0.030 ) . This new technology slightly shortened the bone-cutting time by a mean of 3.6 minutes ( p < 0.001 ) and the operating time by a mean 5.1 minutes ( p = 0.019 ) , without tangible differences in post-operative blood loss ( p = 0.528 ) or need for blood transfusion ( p = 0.789 ) . This study demonstrated that both PSCGs and conventional instrumentation  restore limb alignment and place the components with the similar accuracy . The minimal advantages of PSCGs in terms of consistency of alignment or operative time are unlikely to be clinical ly relevant Background Patient-specific CT-based instrumentation may reduce implant malpositioning and improve alignment in TKA . However , it is not known whether this innovation is an advance that benefits patients . Questions / purpose sWe evaluated ( 1 ) the precision of  patient-specific TKA by comparing the incidence of outliers in postoperative alignment between TKAs using  patient-specific instruments  and TKAs using conventional instruments , and ( 2 ) the reliability of patient-specific instruments by intraoperatively investigating whether the surgery could be completed with patient-specific instruments alone . Methods In this r and omized controlled trial , we compared  patient-specific TKA instruments from one manufacturer ( n = 50 ) with conventional TKA instruments ( n = 50 ) . Postoperative hip-knee-ankle angles , femoral component rotation , and coronal and sagittal alignments of each component were measured . The validity of the patient-specific instrument was examined using cross-checking procedures with conventional instruments during the surgeries . When the procedure could not be completed accurately with patient-specific instruments , the procedure was converted to TKA using conventional instruments , and the frequency of this occurrence was tallied . Results Outliers in the hip-knee-ankle angle were comparable between groups ( 12 % in the patient-specific instrument group and 10 % in the conventional instrument group ) . Other parameters such as sagittal alignment and femoral component rotation did not differ in terms of outliers . Patient-specific guides were ab and oned in eight knees ( 16 % ) during the surgery because of malrotation of the femoral components and decreased slope of the tibia . Conclusions Accuracy was comparable between TKAs done with patient-specific instruments and those done with conventional instruments . However , the patient-specific instrument procedures had to be aborted frequently , incurring expenses that did not benefit patients .Level of Evidence Level II , therapeutic study . See Instructions for Authors for a complete description of levels of evidence
target: 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 .
background: 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 .