The accuracy of component alignment in custom cutting blocks compared with conventional total knee arthroplasty instrumentation: prospective control trial. Improved alignment and operating room efficiency with patient-specific instrumentation for TKA. Patient specific cutting blocks are currently of no proven value. In-vivo alignment comparing patient specific instrumentation with both conventional and computer assisted surgery (CAS) instrumentation in total knee arthroplasty. Is TKA Using Patient-specific Instruments Comparable to Conventional TKA? A Randomized Controlled Study of One System 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 Patient-specific Guides Do Not Improve Accuracy in Total Knee Arthroplasty: A Prospective Randomized Controlled Trial Small Improvements in Mechanical Axis Alignment Achieved With MRI versus CT-based Patient-specific Instruments in TKA: A Randomized Clinical Trial Robotic-assisted TKA Reduces Postoperative Alignment Outliers and Improves Gap Balance Compared to Conventional TKA No improvement in reducing outliers in coronal axis alignment with patient-specific instrumentation Rotational alignment of femoral component between custom cutting block and conventional technique in total knee arthroplasty. Comparison of radiographic alignment of imageless computer-assisted surgery vs conventional instrumentation in primary total knee arthroplasty. The value of patient-matched instrumentation in total knee arthroplasty. Reliability of templating with patient-specific instrumentation in total knee arthroplasty. Component alignment and clinical outcome following total knee arthroplasty: a randomised controlled trial comparing an intramedullary alignment system with patient-specific instrumentation. Stability and alignment do not improve by using patient-specific instrumentation in total knee arthroplasty: a randomized controlled trial Patient-specific Total Knee Arthroplasty Required Frequent Surgeon-directed Changes Patient-matched instruments versus standard instrumentation in total knee arthroplasty: a prospective randomized study Patient-specific instrumentation does not shorten surgical time: a prospective, randomized trial. Patient-specific instrumentation for total knee arthroplasty does not match the pre-operative plan as assessed by intra-operative computer-assisted navigation No Benefit of Patient-specific Instrumentation in TKA on Functional and Gait Outcomes: A Randomized Clinical Trial The radiological outcomes of patient-specific instrumentation versus conventional total knee arthroplasty
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 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 Patient specific cutting guides generated by preoperative Magnetic Resonance Imaging ( MRI ) of the patient 's extremity have been proposed as a method of improving the consistency of Total Knee Arthroplasty ( TKA ) alignment and adding efficiency to the operative procedure . The cost of this option was evaluated by quantifying the savings from decreased operative time and instrument processing costs compared to the additional cost of the MRI and the guide .  Coronal plane alignment was measured in an unselected consecutive series of 200 TKAs , 100 with st and ard instrumentation and 100 with custom cutting guides .  While the cutting guides had significantly lower total operative time and instrument processing time , the estimated $ 322 savings was overwhelmed by the $ 1,500 additional cost of the MRI and the cutting guide . All measures of coronal plane alignment were equivalent between the two groups . The data does not currently support the proposition that patient specific guides add value to TKA Patient specific 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 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 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 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 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 Background Several studies have shown mechanical alignment influences the outcome of TKA . Robotic systems have been developed to improve the precision and accuracy of achieving component position and mechanical alignment . Questions / purpose sWe determined whether robotic-assisted implantation for TKA ( 1 ) improved clinical outcome ; ( 2 ) improved mechanical axis alignment and implant inclination in the coronal and sagittal planes ; ( 3 ) improved the balance ( flexion and extension gaps ) ; and ( 4 ) reduced complications , postoperative drainage , and operative time when compared to conventionally implanted TKA over an intermediate-term ( minimum 3-year ) followup period . Methods We prospect ively r and omized 100 patients who underwent unilateral TKA into one of two groups : 50 using a robotic-assisted procedure and 50 using conventional manual techniques .  Outcome variables considered were postoperative ROM , WOMAC scores , Hospital for Special Surgery ( HSS ) knee scores , mechanical axis alignment , flexion/extension gap balance , complications , postoperative drainage , and operative time . Minimum followup was 41 months ( mean , 65 months ; range , 41–81 months ) . Results There were no differences in postoperative ROM , WOMAC scores , and HSS knee scores . The robotic-assisted group result ed in no mechanical axis outliers ( > ± 3 ° from neutral ) compared to 24 % in the conventional group . There were fewer robotic-assisted knees where the flexion gap exceeded the extension gap by 2 mm . The robotic-assisted procedures took an average of 25 minutes longer than the conventional procedures but had less postoperative blood drainage . There were no differences in complications between groups . Conclusions Robotic-assisted TKA appears to reduce the number of mechanical axis alignment outliers and improve the ability to achieve flexion-extension gap balance , without any differences in clinical scores or complications when compared to conventional manual techniques . Level of Evidence Level I , therapeutic study . See Instructions for Authors for a complete description of levels of evidence 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 OBJECTIVE Rotation of femoral components could be optimized to improve function and durability of the knee joint . The purpose of the present study was to assess rotational alignment of femoral component comparing between CT-based , custom cutting blocks and the contemporary total knee arthroplasty , instrument technique . MATERIAL AND METHOD The prospect i ve control study of 80 patients underwent total knee arthroplasty by using PFC Sigma PS total knee design . Rotation offemoral component was analyzed in all patients using postoperative CT scan .  Forty patients were perfonned on by using CT-based , patient-specific cutting blocks with femoral rotational axis relative to transepicondylar axis while forty patients were performed on by using contemporaly instrumentation with alignment at 3 degrees external rotation from posterior condylar line . The rotation of the femoral component with external rotation ofmore than 3 degrees or internal rotation was considered outlier . RESULTS There was no statistically significant difference among ages , gender ; BMI , pre-operative mechanical axis between the two groups . There were eleven outliers in conventional group ( range , 5 degrees ofexternal rotation to 3 degrees of internal rotation ) , three femoral components were in excessive external rotation with the angle of more than 3 degrees and eight femnoral components were in internal rotation . In contrast with custom cutting block group was no outliers offemoral rotation . The average rotational alignment was 1.040 + /- 0.62 external rotation from epicondylar axis in custom cutting group and 1.58 + /- 1.750 in contemporary group . CONCLUSION Custom cutting , block technique significantly reduced the outlier of the femoral component rotation and aided in positioning of the femoral component in optimal alignment . The improvement of femoral rotation showed no difference in clinical outcome between the two groups A total of 208 patients were enrolled in a multicenter , prospect i ve r and omized , institutional review board-approved study that compared preoperative surgical plan to postoperative 2-dimensional radiographic alignment measured by a blinded review er for  primary total knee arthroplasty ( TKA ) implanted using computer-assisted surgery ( CAS ) compared with conventional TKA instrumentation . The results demonstrated a statistically significant improvement in the coronal tibial component alignment ( P < .03 ) and failed to demonstrate a statistically significant improvement in the mechanical axis , femoral coronal/sagittal , and tibial sagittal alignment . Knee Society Score knee and function scores and 6-minute walk test were equivalent between the 2 treatment groups at all postoperative intervals . There was a statistically significant increase in the skin-skin time ( P < .0001 ) and the time until first bone cut ( P < .0001 ) for the CAS knees compared with those implanted with conventional instrumentation . The use of CAS in this r and omized clinical trial conducted at high-volume centers did not offer a clinical ly meaningful improvement in postoperative alignment , clinical , functional , or safety outcomes compared with conventional TKA 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 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 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 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 Patient-specific instrumentation potentially improves surgical precision and decreases operative time in total knee arthroplasty ( TKA ) but there is little supporting data to confirm this presumption . Questions / purpose sWe asked whether patient-specific instrumentation would require infrequent intraoperative changes to replicate a single surgeon ’s preferences during TKA and whether patient-specific instrumentation guides would fit securely . Methods We prospect ively evaluated the plan and surgery in 60 patients treated with 66 TKAs performed with patient-specific instrumentation and recorded any changes . A subset of six postoperative radiographic changes to the femoral and tibial components ( implant size , coronal and sagittal alignment ) was analyzed to determine if surgeon intervention was beneficial . Each guide was evaluated to determine fit . We compared patient demographics and implant sizing in the patient-specific instrumentation group with a control group in which traditional instrumentation was used . Results We recorded 161 intraoperative changes in 66 knee arthroplasties ( 2.4 changes/knee ) performed with patient-specific instrumentation . The predetermined implant size was changed intraoperatively in 77 % of femurs and 53 % of tibias . We identified a subset of 95 intraoperative changes that could be radiographically evaluated to determine if our changes were an improvement or detriment to reaching goal alignment . Eighty-two of the 95 changes ( 86 % ) made by the surgeon were an improvement to the recommended alignment or size of patient-specific instrumentation . The guide did not fit securely on eight femurs ( 12 % ) and three tibias ( 5 % ) . Tourniquet time and blood loss were not improved with patient-specific instrumentation . Conclusions We caution surgeons against blind acceptance of patient-specific instrumentation technology without supportive data .Level of Evidence Level III , therapeutic study . See Guidelines for Authors for a complete description of levels of evidence 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 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 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 Background Although some clinical reports suggest patient-specific instrumentation in TKA may improve alignment , reduce surgical time , and lower hospital costs , it is unknown whether it improves pain- and function-related outcomes and gait . Questions / purpose sWe hypothesized that TKA performed with patient-specific instrumentation would improve patient-reported outcomes measured by vali date d scoring tools and level gait as ascertained with three-dimensional ( 3-D ) analysis compared with conventional instrumentation 3 months after surgery . Methods We r and omized 40 patients into two groups using either patient-specific instrumentation or conventional instrumentation .  Patients were evaluated preoperatively and 3 months after surgery . Assessment tools included subjective functional outcome and quality -of-life ( QOL ) scores using vali date d question naires ( New Knee Society Score © [ KSS ] , Knee Injury and Osteoarthritis Outcome Score [ KOOS ] , and SF-12 ) . In addition , gait analysis was evaluated with a 3-D system during level walking . The study was powered a priori at 90 % to detect a difference in walking speed of 0.1 m/second , which was considered a clinical ly important difference , and in a post hoc analysis at 80 % to detect a difference of 10 points in KSS . Results There were improvements from preoperatively to 3 months postoperatively in functional scores , QOL , and knee kinematic and kinetic gait parameters during level walking . However , there was no difference between the patient-specific instrumentation and conventional instrumentation groups in KSS , KOOS , SF-12 , or 3-D gait parameters . Conclusions Our observations suggest that patient-specific instrumentation does not confer a substantial advantage in early functional or gait outcomes after TKA . It is possible that differences may emerge , and this study does not allow one to predict any additional variances in the intermediate followup period from 6 months to 1 year postoperatively . However , the goals of the study were to investigate the recovery period as early pain and functional outcomes are becoming increasingly important to patients and surgeons . Level of Evidence Level I , therapeutic study . See the Instructions to Authors for a complete description of levels of evidence 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
Results The majority of studies did not show an improvement in overall limb alignment when PSI was compared with st and ard instrumentation .
The studies demonstrated mixed results regarding the influence of PSI on operative times .
Decreased operative times were not uniformly observed , and when noted , they were found to be of minimal clinical or financial significance .
PSI did reliably reduce the number of instrument trays required for processing perioperatively .
The accuracy of the preoperative plan , generated by the PSI manufacturers , was found lacking , often leading to multiple intraoperative changes , thereby disrupting the flow of the operation and negatively impacting efficiency .
Neither of the two studies we identified provided strong evidence to support an advantage favoring the use of PSI .
Conclusions PSI for TKA has not reliably demonstrated improvement of postoperative limb or component alignment when compared with st and ard instrumentation .
Although decisive evidence exists to support that PSI requires fewer surgical trays , PSI has not clearly been shown to improve overall surgical efficiency or the cost-effectiveness of TKA .
Limited available literature does not clearly support any improvement of postoperative pain , activity , function , or ROM when PSI is compared with traditional instrumentation
Background Patient-specific cutting blocks have been touted as a more efficient and reliable means of achieving neutral mechanical alignment during TKA with the proposed downstream effect of improved clinical outcomes .
However , it is not clear to what degree published studies support these assumptions .
Questions / purpose sWe asked : ( 1 ) Do  patient-specific cutting blocks  achieve neutral mechanical alignment more reliably during TKA when compared with conventional methods ? (
2 ) Does patient-specific instrumentation ( PSI ) provide financial benefit through improved surgical efficiency ? (
3 ) Does the use of patient-specific cutting blocks translate to improved clinical results after TKA when compared with conventional instrumentation ?