Rotational alignment of femoral component between custom cutting block and conventional technique in total knee arthroplasty. Stability and alignment do not improve by using patient-specific instrumentation in total knee arthroplasty: a 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. Evaluation of the accuracy of a patient-specific instrumentation by navigation Comparison of radiographic alignment of imageless computer-assisted surgery vs conventional instrumentation in primary total knee arthroplasty. The radiological outcomes of patient-specific instrumentation versus conventional total knee arthroplasty Comparison between patient-specific instruments and conventional instruments and computer navigation in total knee arthroplasty: a randomized controlled trial Patient specific cutting blocks are currently of no proven value. Comparison of robot-assisted and conventional total knee arthroplasty: A controlled cadaver study using multiparameter quantitative three-dimensional CT assessment of alignment Comparison between computer-assisted-navigation and conventional total knee arthroplasties in patients undergoing simultaneous bilateral procedures: a randomized clinical trial. Patient-specific instrumentation in total knee arthroplasty: simpler, faster and more accurate than standard instrumentation—a randomized controlled trial Alignments and Clinical Results in Conventional and Navigated Total Knee Arthroplasty Navigated total knee arthroplasty: a radiological analysis of 42 randomised cases. The accuracy of component alignment in custom cutting blocks compared with conventional total knee arthroplasty instrumentation: prospective control trial. Navigation Improves Accuracy of Rotational Alignment in Total Knee Arthroplasty Patient-specific computed tomography based instrumentation in total knee arthroplasty: a prospective randomized controlled study Component alignment and clinical outcome following total knee arthroplasty: a randomised controlled trial comparing an intramedullary alignment system with patient-specific instrumentation. Patient-specific instrumentation for total knee arthroplasty does not match the pre-operative plan as assessed by intra-operative computer-assisted navigation Comparison of Outcome and Survival After Unicompartmental Knee Arthroplasty Between Navigation and Conventional Techniques With an Average 9-Year Follow-Up. Minimal invasive and computer-assisted total knee replacement compared with the minimal invasive technique: a prospective, randomized trial with short-term outcomes Patient-specific Guides Do Not Improve Accuracy in Total Knee Arthroplasty: A Prospective Randomized Controlled Trial Mobile-bearing prosthesis did not improve mid-term clinical results of total knee arthroplasty Effect of alignment changes on sagittal and coronal socket reaction moment interactions in transtibial prostheses.
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 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 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 Purpose The aim of this study is to evaluate the accuracy of a  patient-specific instrumentation ( PSI ) as assessed by the intraoperative use of knee navigation software during the surgical procedure . Methods Fifteen patients with primary gonarthrosis were selected for unilateral total knee arthroplasty . The first three patients were excluded from this study , as they were considered to be a warm up to set-up the procedure . All patients were operated on with a cemented posterior-stabilised prosthesis cruciate ligament-sacrificing by the same surgeon using the patient matched cutting jigs . The size of the implant , level of resection , and alignment in the coronal and sagittal planes were evaluated . An unsatisfactory result was considered an error ≥2 ° in both planes for each component as a possible error of 4 ° could result in aggravation . Results On the coronal plane the mean deviation of the tibial guide from the ideal alignment was 1.2 ± 1.5 ( range 0–5 ° ) and in the sagittal plane was 3.8 ± 2.4 ( range 0–7.5 ° ) . On the coronal plane the mean deviation of the femoral guide from the ideal alignment was 1.2 ± 0.6 and in the sagittal was 3.7 ± 2 . Conclusion On the basis of this preliminary experience the PSI system based only on data acquisition with A-P radiograms and RMN can not be defined as accurate . In cases of the use of the custom made cutting jigs it is recommended to perform an accurate control of the alignment before making the cuts , for any step of the procedure . Level of evidence II 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 Abstract Purpose The aim of this study was to investigate the post-operative radiological outcomes of patient-specific instrumentation ( PSI ) surgery versus conventional total knee arthroplasty ( TKA ) . Methods Sixty patients scheduled for a primary TKA were prospect ively divided into PSI or conventional technique . Coronal and sagittal radiographic long limb films were taken post-operatively . The accepted values for normal alignment were 180 ° ± 3 ° for hip-knee-ankle angle ; 90 ° ± 3 ° for coronal femoral component angle or coronal tibia component angle ; 0 ° to 3 ° flexion for sagittal femoral component angle and 0 ° to 7 ° posterior slope for sagittal tibia component angle . Results For hip-knee-ankle angle , there were 21 % more outliers in the PSI group compared to the conventional group ( p = 0.045 ) . Most of these outliers had valgus deformity in the PSI group and varus deformity in the conventional group ( p = 0.045 ) . For implant placement , there was no difference in the proportion of outliers between the two groups . There was also no difference in the duration of surgery . Conclusions This study showed that PSI surgery is associated with a larger proportion of outliers for lower limb alignment . PSI surgery as an alternative to conventional TKA is not advisable . Level of evidence II Abstract Purpose The 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 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 Introduction : A functional total knee replacement has to be well aligned , which implies that it should lie along the mechanical axis and in the correct axial and rotational planes . Incorrect alignment will lead to abnormal wear , early mechanical loosening , and patellofemoral problems . There has been increased interest of late in total knee arthroplasty with robotic assistance . This study was conducted to determine whether robot-assisted total knee arthroplasty is superior to the conventional surgical method with regard to the precision of implant positioning . Material s and Methods : Twenty knee replacements , comprising ten robot-assisted procedures and ten conventional operations , were performed on ten cadavers . Two experienced surgeons performed the surgeries . Both procedures on each cadaver were performed by the same surgeon . The choice of which procedure was to be performed first was r and omized . Following implantation of the prosthesis , the mechanical axis deviation , femoral coronal angle , tibial coronal angle , femoral sagittal angle , tibial sagittal angle , and femoral rotational alignment were measured via 3D CT scanning . These variables were then compared with the preoperatively planned values . Results : In the knees that underwent robot-assisted surgery , the mechanical axis deviation ranged from −1.94 ° to 2.13 ° ( mean : −0.21 ° ) , the femoral coronal angle from 88.08 ° to 90.99 ° ( mean : 89.81 ° ) , the tibial coronal angle from 89.01 ° to 92.36 ° ( mean : 90.42 ° ) , the tibial sagittal angle from 81.72 ° to 86.24 ° ( mean : 83.20 ° ) , and the femoral rotational alignment from 0.02 ° to 1.15 ° ( mean : 0.52 ° ) in relation to the transepicondylar axis . In the knees that underwent conventional surgery  , the mechanical axis deviation ranged from −3.19 ° to 3.84 ° ( mean : −0.48 ° ) , the femoral coronal angle from 88.36 ° to 92.29 ° ( mean : 90.50 ° ) , the tibial coronal angle from 88.15 ° to 91.51 ° ( mean : 89.83 ° ) , the tibial sagittal angle from 80.06 ° to 87.34 ° ( mean : 84.50 ° ) , and the femoral rotational alignment from 0.32 ° to 4.13 ° ( mean : 2.76 ° ) in relation to the transepicondylar axis . In the conventional knee replacement group , there were two instances of outliers outside the range of 3 ° varus/valgus for the mechanical axis deviation . The robot-assisted knee replacements showed significantly superior femoral rotational alignment results compared with conventional surgery ( p = 0.006 ) . There was no statistically significant difference between robot-assisted and conventional total knee arthroplasty with regard to the other variables . All the measurements showed high intra-observer and inter-observer reliability . Conclusion : Robot-assisted total knee arthroplasty showed excellent precision in the sagittal and coronal planes of the 3D CT scan . In particular , the robot-assisted technique showed better accuracy in femoral rotational alignment compared to the conventional surgery , despite the fact that the surgeons who performed the operations were more experienced and familiar with the conventional method than with robot-assisted surgery . It can thus be concluded that robot-assisted total knee arthroplasty is superior to conventional total knee arthroplasty BACKGROUND Total knee arthroplasty has been increasingly used for young and active patients , and prosthesis durability is important in these patients . The accuracy of implant placement has been one of the major factors that determine the long-term survival of the prosthesis . The purpose of this study was to compare the accuracy of prosthetic alignment between computer-assisted-navigation and conventional total knee arthroplasties . METHODS From March 2007 to June 2008 , thirty-two patients with bilateral knee osteoarthritis underwent simultaneous bilateral total knee arthroplasty with the same type of implant in each knee .  The subjects included seven men and twenty-five women , with an average age of sixty-three years . For each patient , the bilateral total knee arthroplasty was performed with computer-assisted navigation in one knee and a conventional technique in the other . The operative technique and the order of the surgical procedures were r and omized . The patients and surgeons conducting the follow-up study and performing the imaging measurements were blinded to the type of surgical procedure . RESULTS There was a significant difference between the two groups with regard to the alignment of the knee prosthesis in the coronal and sagittal planes . Nine knee implants ( 28 % ) in the conventional group , compared with no knee implants in the computer-navigation group , deviated > 3 ° from the mechanical axis in the coronal plane . The coefficient variation of data in the conventional group was three times greater than that in the computer-navigation group . There was no significant difference in the rotational angle of the femoral component between the two groups . The Hospital for Special Surgery ( HSS ) scores at six months postoperatively were substantially increased compared with the preoperative scores in both groups . CONCLUSIONS Computer-assisted navigation consistently provided coronal plane alignment within 3 ° of the mechanical axis , which was significantly better than the alignment obtained with conventional total knee arthroplasty Abstract Purpose This r and omized controlled trial was conducted to compare patient-specific instrumentation ( PSI ) to st and ard instrumentation regarding efficacy to achieve a good coronal alignment and differences in surgical time , blood loss and length of stay . Methods Ninety-five of 100 r and omized patients eligible for total knee arthroplasty were analysed .  PSI with magnetic resonance and long-leg radiograph was performed in 47 patients , while 48 patients received st and ard instrumentation .  Primary outcome measure was coronal alignment , evaluated with long-leg radiograph . Deviation > 3 ° varus/valgus was considered an outlier . Surgical time was compared from skin to skin . Length of stay was a post hoc analysis . Blood loss was evaluated comparing the number of blood units spent , fall in haemoglobin and haematocrit levels . Results St and ard instrumentation had a higher number of outliers in the coronal alignment with a relative risk of 3.015 , compared to PSI . Surgical time was reduced by 18 min ( 24.8 % ) with the  PSI  , as well as length of stay , with a half-day reduction . Number of blood units spent was significantly less in the PSI group . Relative risk of transfusion was 7.09 for patients in the st and ard instrumentation group . Difference in Hg and Htc levels were not significant . No patient had to ab and on PSI . Minor changes to preoperative plan occurred in 14.9 % of the patient : cut review in 4.3 % and insert change in 10.6 % . Conclusions Patient-specific instrumentation ( PSI ) is able to provide important advantages over st and ard instrumentation in total knee arthroplasty : it lowers the risk of outliers and transfusion , is a faster procedure and enables a shorter length of stay with a low rate of intraoperative adjustments . Level of evidence In this prospect i ve , r and omized , controlled study , we compared the performance of conventional and navigated total knee arthroplasties .  Component alignment was measured in 60 patients operated on using navigation and in 60 patients operated on using the conventional technique .  The groups then were divided into a sub population to measure alignments of the distal femoral cuts in the three anatomic planes , the proximal tibial cut in the frontal and sagittal planes , and the result ing lower limb mechanical axis in the frontal plane . Postoperative weightbearing long-view radiographs  were evaluated as were clinical results using three st and ard question naires at 28 months followup . The intraoperative measurements ( mean ± st and ard deviation ) at the resection planes showed navigated surgeries result in more accurate alignments than conventional surgeries for the femur : in the frontal plane , 0.1 ° ± 0.9 ° and 0.7 ° ± 1.6 ° valgus , respectively ; in the sagittal plane , 1.1 ° ± 1.8 ° and 2.8 ° ± 2.0 ° flexion ; and in the transversal plane , 0.1 ° ± 1.2 ° and 0.9 ° ± 1.7 ° internal rotation . The navigated technique also reduced the number of cases with final mechanical axes greater than 3 ° from 20.0 % to 1.7 % . Postoperative radiographs showed better component alignment using navigation , particularly at the femur . However , clinical scoring systems showed this radiographic improvement did not necessarily result in a better clinical outcome at short-term followup . Level of Evidence : Level I , therapeutic study . See the Guidelines for Authors for a complete description of level of evidence The purpose of this study was to evaluate the use of a  navigation device  in a cohort of 42 total knee arthroplasties ( TKA ) . The patients were r and omised into two groups . Total knee arthroplasties performed using the conventional technique formed the control group ( 21 knees ) ; the experimental group included 21 knees performed with the aid of a computed navigation system .  Postoperative mean values for the various measurements showed no significant difference in component alignment . However , the range of individual measurements for coronal and sagittal plane positioning was smaller in the navigated group , in which there were no outliers . Rotational alignment was not different between the two groups . This confirms the advantages and limitations of navigated TKA presented in larger studies 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 Successful total knee arthroplasty is dependent on the correct alignment of implanted prostheses . Major clinical problems can be related to poor femoral component positioning , including sagittal plane and rotational malalignment . A prospect i ve r and omized study was design ed to test whether an optical navigation system for total knee arthroplasty achieved greater implantation precision than a nonnavigated technique . The primary variable was rotation of the femoral component in the transverse plane , measured from postoperative radiographs and computed tomography images . Sixty-four patients were included in the study . All patients received the Duracon total knee prosthesis .  The patients were r and omly divided into two groups : Group C patients had conventional total knee arthroplasty without navigation ; Group N patients had total knee arthroplasty using a computer-assisted knee navigation system . Analysis showed that patients in Group N had significantly better rotational alignment and flexion angle of the femoral component than patients in Group C. In addition , superior postoperative alignment of the mechanical axis , posterior tibial slope , and rotational alignment was achieved for patients in Group N. The use of a navigation system provides improved alignment accuracy , and can help to avoid femoral malrotation and errors in axial alignment 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 AIMS We conducted a r and omised controlled trial to assess the accuracy of positioning and alignment of the components in total knee arthroplasty ( TKA ) , comparing those undertaken using st and ard intramedullary cutting jigs and those with patient-specific instruments ( PSI ) . PATIENTS AND METHODS There were 64 TKAs in the st and ard group and 69 in the PSI group . The post-operative hip-knee-ankle ( HKA ) angle and positioning was investigated using CT scans . Deviation of > 3 ° from the planned position was regarded as an outlier . The operating time , Oxford Knee Scores ( OKS ) and Short Form-12 ( SF-12 ) scores were recorded . RESULTS There were 14 HKA-angle outliers ( 22 % ) in the st and ard group and nine ( 13 % ) in the PSI group ( p = 0.251 ) . The mean HKA-angle was 0.5 ° varus in the st and ard group and 0.2 ° varus in the PSI group ( p = 0.492 ) . The accuracy of alignment in the coronal and axial planes and the proportion of outliers was not different in the two groups . The femoral component was more flexed ( p = 0.035 ) and there were significantly more tibial slope outliers ( 29 % versus 13 % ) in the PSI group ( p = 0.032 ) . Operating time and the median three-month OKS were similar ( p = 0.218 and p = 0.472 , respectively ) . Physical and mental SF-12 scores were not significantly different at three months ( p = 0.418 and p = 0.267 , respectively ) or at one year post-operatively ( p = 0.114 and p = 0.569 ) . The median one-year Oxford knee score was two points higher in the PSI group ( p = 0.049 ) . CONCLUSION Compared with st and ard intramedullary jigs , the use of PSI did not significantly reduce the number of outliers or the mean operating time , nor did it clinical ly improve the accuracy of alignment or the median Oxford Knee Scores . Our data do not support the routine use of PSI when undertaking TKA . Cite this article : Bone Joint J 2016;98-B:1043 - 9 Abstract Purpose 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 Unicompartmental knee arthroplasty(UKA ) has become a treatment of choice for many patients with isolated unicomparmental arthritis due to its specific advantages over total knee arthroplasty , but few studies have compared conventional and navigational UKA with similar instrumentation on mid- to long-term results . We investigated whether the use of imageless navigation can improve implant positioning and clinical outcomes of UKA at a long-term follow-up compared to the conventional technique . METHODS We prospect ively studied clinical and radiological results in 68 patients with an average age of 64.0 years ( range , 50 to 81 years ) who received UKA between January 2003 and December 2005 using the conventional or navigational technique .  Clinical evaluations were performed preoperatively and the last follow-up included knee range of motion , Hospital for Special Surgery ( HSS ) scores , Western Ontario and McMaster Universities Osteoarthritis Index ( WOMAC ) scores and Visual Analogue Scale ( VAS ) pain score . For radiologic evaluation , the mechanical alignment of the lower limb was measured using mechanical femoro-tibial angle ( mFTA ) and Kennedy protocol . RESULTS After an average 9-year follow-up ( range , 7.4 to 10.8 years ) , the navigation group showed better coronal alignments of the components , fewer radiological outliers and better clinical scores , but similar estimated 10-year prosthesis survival rates . CONCLUSION This study indicates that the use of navigation significantly contributes to the desired mechanical axis and improved component placement as compared to the conventional technique . LEVEL OF EVIDENCE Prospect i ve comparative study , Level III Abstract Introduction Up to now , no prospect i ve , r and omized comparisons between minimal invasive and computer-assisted total knee arthroplasty ( MICA-TKA ) , and minimal invasive technique ( MI-TKA ) has been documented to evaluate not only clinical , but also radiologic results of the MICA-TKA . This prospect i ve , r and omized study was performed to compare the short-term results of MICA-TKA with minimal invasive technique MI-TKA for 6-month follow-up . Patients and methods We reported the clinical and radiological results of 80 subjects who had cruciate-substituting , TKA-implanted primary total knee arthroplasties using either minimal invasive and computer-assisted technique ( 40 patients Group I ) or minimal invasive technique ( 40 patients , Group II ) .  Tourniquet time , length of skin incision , and total blood loss were compared . Knee society scores ( KSSs ) , knee society functional scores ( KSFSs ) , range of motion ( ROM ) , and radiographic results were assessed and reported preoperatively and at 6-month follow-up . Results The accuracy of the implantations in relation to the coronal mechanical axis in Group I was superior to that of Group II ( P < 0.05 ) . The femoral rotational profile revealed the prosthesis in Group I that was implanted with significantly less internal rotation than in Group II . The average blood loss in patients of Group I was significantly reduced as compared to patients of Group II . No significant difference was detected in terms of tourniquet time or length of skin incision . Clinical results , with regard to ROMs and KSSs , as well as KSFSs were equally good in both the groups . Conclusions Better alignment and similarity of good clinical results at short-term follow-up may provide subjects who receive MICA-TKA with long-term endurance of their implants . Further studies on longer-term outcomes and functional improvements are required to vali date these possibilities 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 A prospect i ve study was performed to compare the clinical and radiological results of mobile- and fixed-bearing total knee arthroplasty  with specific attention to rotational alignment and range of motion . Sixty-one knees were assigned to total knee arthroplasty with either the NexGen LPS Flex fixed-bearing or with the NexGen LPS Flex mobile-bearing prosthesis . Postoperatively , knees were compared with regard to range of motion , clinical score , and radiographic findings . Rotational alignment of the femoral and tibial components was evaluated by computed tomography . The median follow-up period was 5.9 years ( range 2.1–8.8 years ) . Median postoperative Knee Society scores were 99 points ( 68–100 ) for the fixed-bearing group and 100 points ( 66–100 ) for the mobile-bearing group ( n.s . ) . The median postoperative flexion angles of 120 ° ( 90 ° –150 ° ) for the fixed-bearing group and 125 ° ( 90 ° –145 ° ) for the mobile-bearing group were not significantly different from each other ( n.s . ) . No knee required revision surgery due to wear of polyethylene or loosening of the component in either group . Computed tomography showed that 11 knees had rotational mismatches of more than 10 ° between the femoral and tibial components , but no significant difference was found in the postoperative extension and flexion angles or in the clinical score between the two treatment groups . Using the identical design for both fixed- and mobile-bearing prostheses , this prospect i ve , r and omized study did not show any clinical advantages of the mobile-bearing knee . Analysis of rotational alignment by CT scan did not reveal a particular advantage of the self-aligning mechanism of mobile-bearing implants Alignment is important for comfortable and stable gait of lower-limb prosthesis users . The magnitude of socket reaction moments in the multiple planes acting simultaneously upon the residual limb may be related to perception of comfort in individuals using prostheses through socket interface pressures . The aim of this study was to investigate the effect of prosthetic alignment changes on sagittal and coronal socket reaction moment interactions ( moment-moment curves ) and to characterize the curves in 11 individuals with transtibial amputation using novel moment-moment interaction parameters measured by plotting sagittal socket reaction moments versus coronal ones under various alignment conditions . A custom instrumented prosthesis alignment component was used to measure socket reaction moments during walking . Prosthetic alignment was tuned to a nominally aligned condition by a prosthetist , and from this position , angular ( 3 ° and 6 ° of flexion , extension , abduction or adduction of the socket ) and translational ( 5 mm and 10 mm of anterior , posterior , medial or lateral translation of the socket ) alignment changes were performed in either the sagittal or the coronal plane in a r and omized manner . A total of 17 alignment conditions were tested . Coronal angulation and translation alignment changes demonstrated similar consistent changes in the moment-moment curves . Sagittal alignment changes demonstrated more complex changes compared to the coronal alignment changes . Effect of sagittal angulations and translations on the moment-moment curves was different during 2nd rocker ( mid-stance ) with extension malalignment appearing to cause medio-lateral instability . Presentation of coronal and sagittal socket reaction moment interactions may provide useful visual information for prosthetists to underst and the biomechanical effects of malalignment of transtibial prostheses
We found that there was no significant benefit from using PS instrumentation in primary knee arthroplasty to aid in the positioning of either the tibial or femoral components .
Furthermore sagittal plane tibial component positioning was worse in the PS than the traditional ST group .
Our results suggest that at present PS instrumentation is not superior to ST instrumentation in primary total knee arthroplasty .
OBJECTIVE The aim of this study was to review the radiological alignment outcomes of patient Specific ( PS ) cutting blocks and St and ard Instrumentation in Primary Total Knee Arthroplasty .
METHODS We hypothesized that the use of PS techniques would significantly improve sagittal , coronal and rotational alignment of the prosthesis on short term .