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.
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
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 ?