Introduction. Patient self-reported outcome scales have recently been used to evaluate total knee arthroplasty (TKA) outcomes. Many follow-up studies have been conducted on patients undergoing TKA; however, they have mostly reported outcomes after unilateral TKA. We believe that a longitudinal study after bilateral TKA will be more useful in evaluating the quality of life (QOL) of such patients. Objectives. The objective of this study was to longitudinally evaluate QOL using the Japanese Knee Osteoarthritis Measure (JKOM). Objective outcomes were assessed using the Knee Society Score (KSS) and the Timed Up and Go test (TUG) for more than 5 years after bilateral TKA. Furthermore, QOL and objective outcomes were compared between younger (age ≤ 80 years at the final follow-up point) and older (age > 80 years) age groups. Methods. In total, 109 patients underwent two-staged bilateral TKAs for varus knee osteoarthritis at our clinic between October 2006 and March 2013. Of these patients, 78 were evaluated preoperatively (Pre) and at 1, 3 and 5 years or more (average, 6.7 years; range, 5–10 years) after bilateral TKAs using JKOM, KSS and TUG. The average patient age at the time of the first and the contralateral TKAs was 73.3 (range, 61–85) years and 74.0 (range, 62–85) years, respectively. The average patient age at the final follow-up point among younger (36 patients) and older (42 patients) age groups was 75.8 (range, 67–80) years and 84.7 (range: 81–92) years, respectively. The outcomes at each evaluation point were compared using Steel–Dwass test. A comparison of the JKOM scores and objective outcomes between the younger and older age groups was performed using Mann–Whitney U-test. P values < 0.05 were considered significant. Results. A significant improvement in the JKOM score was observed between ‘Pre’ and ‘1 year after bilateral TKA’; the improvement was maintained until the final follow-up point. All four subscales in JKOM showed the same improvement as JKOM itself. Furthermore, significant improvements in the total KSS, knee and function scores were observed between ‘Pre’ and ‘1 year after bilateral TKA’; the improvement was maintained until the final follow-up point. A significant improvement in the TUG scores was observed between ‘Pre’ and ‘1 year after bilateral TKA’; although the improvement was maintained for 3 years, there was a small but significant deterioration at the final follow-up point. Although the average age difference between the two groups was 8.9 years, no significant differences were found in the JKOM and objective outcome scores between the younger and older age groups. Conclusions. This is the first longitudinal mid-term follow-up study to evaluate QOL after bilateral TKAs. The JKOM and objective outcome scores reached a plateau 1 year after bilateral TKA, and the improvement was maintained for an average of 6.7 years; however, TUG scores showed a small deterioration at the final follow-up point. The improvement in the JKOM and objective outcome scores maintained by the older age group was equivalent to that by the younger one

A primary goal of revision Total Knee Arthroplasty (rTKA) is restoration of the Joint Line (JL) and Posterior Condylar Offsets (PCO). The presence of a native contralateral joint allows JL and PCO to be inferred in a way that could account for patient-specific anatomical variations more accurately than current techniques. This study assesses bilateral distal femoral symmetry in the context of defining targets for restoration of JL and PCO in rTKA. 566 pre-operative CTs for bilateral TKAs were segmented and landmarked by two engineers. Landmarks were taken on both femurs at the medial and lateral epicondyles, distal and posterior condyles and hip and femoral centres. These landmarks were used to calculate the distal and posterior offsets on the medial and lateral sides (MDO, MPO, LDO, LPO respectively), the lateral distal femoral angle (LDFA), TEA to PCA angle (TEAtoPCA) and anatomic to mechanical axis angle (AAtoMA). Mean bilateral differences in these measures were calculated and cases were categorised according to the amount of asymmetry. The database analysed included 54.9% (311) females with a mean population age of 68.8 (±7.8) years. The mean bilateral difference for each measure was: LDFA 1.4° (±1.0), TEAtoPCA 1.3° (±0.9), AAtoMA 0.5° (±0.5), MDO 1.4mm (±1.1), MPO 1.0mm (±0.8). The categorisation of asymmetry for each measure was: LDFA had 39.9% of cases with <1° bilateral difference and 92.4% with <3° bilateral difference, TEAtoPCA had 45.8% <1° and 96.6% <3°, AAtoMA had 85.7% <1° and 99.8% <3°, MDO had 46.2% <1mm and 90.3% <3mm, MPO had 57.0% <1mm and 97.9% <3mm. This study presents evidence supporting bilateral distal femoral symmetry. Using the contralateral anatomy to obtain estimates for JL and PCO in rTKA may result in improvements in intraoperative accuracy compared to current techniques and a more patient specific solution to operative planning

BACKGROUND. Patella resurfacing in TKA remains controversial. The purpose of this study was to compare the long-term clinical outcome in TKA in patients undergoing bilateral TKAs with one patella resurfaced and the other patella nonresurfaced. METHODS. Twenty-nine patients (58 knees) underwent primary bilateral TKA for osteoarthritis. These patients were enrolled in a prospective randomised double blinded study and represent a subset of a larger study of patella resurfacing. All patients received the same posterior cruciate sparing TKA. Patients each had one knee randomised to treatment with or without patella resurfacing. The contralateral knee then received the alternative patellar treatment, such that all patients had one knee with a resurfaced patella and the other nonresurfaced. Clinical evaluations consisted of routine radiographic and clinical follow-up and included with a Knee Society Score patellofemoral specific patient questionnaire. Twenty-eight patients (56 knees) participated and were followed for a mean of 118 months (range, 69–146 months). RESULTS. There were no significant differences between the knees treated with and without patellar resurfacing with regard to range of motion, KSCRS, or the pain and function scores. Forty-six percent (13/28 patients) of patients preferred the resurfaced knee, 36% (10/28) the nonresurfaced knee, and 18% (5/28) had no preference. Two patients (7%) in the nonresurfaced group required revision for a patellofemoral related complication, compared to one patient (3.5%) in the group with a resurfaced patella. CONCLUSIONS. Ten year follow-up reveals equivalent results for resurfaced and nonresurfaced patellae in TKA with regards to ROM, KSCRS, pain and function, or patellofemoral symptoms. In this large series of bilateral TKAs, 64% of patients either preferred the unresurfaced knee or had no preference

Introduction. A large proportion of patients with osteoarthritis of the knee, present with bilateral symptoms at the outpatient department. A simultaneous total knee arthroplasty (TKA) procedure is available for such patients. The first operation in a simultaneous surgery may provide information to the operator to determine component size, soft tissue balancing, and estimate gap size for the second operation, while the second team usually conducts an operation in a confined space on the contralateral side during closure for the first operation, which can disturb cooperation during the second operation and may lead to more intra-operative surgical errors. We hypothesized that the circumstances of the two consecutive operations of a simultaneous bilateral TKA are different, could lead to different outcomes of overlapping bilateral TKAs. We therefore addressed the following research questions to determine whether there would be differences in short-term clinical outcomes, radiographic results, and implanted component size between the two sides. Methods. A retrospective review of 451 consecutive patients, who underwent simultaneous bilateral TKA between January 2011 and April 2012, was conducted. Bilateral TKAs were performed with the senior surgeon conducting the main procedure (from skin incision to implantation of first prosthesis until prior closure of the first knee) on the right side first and subsequently the left side with a second team. At 1 year after surgery, clinical outcome scores (the Knee Society Knee and Function scores, WOMAC score), radiologic findings were evaluated and clinical results as postoperative blood loss, operation time were compared between bilateral sides. Results. A greater incidence (16.1%) of outliers during postoperative coronal limb alignment (>±3o) were identified in the second TKA than those in the first TKA (9.0%) (p =0.003). Multivariate analysis for the association of outlier rates in the second TKA relative to the first revealed a significance for severity of the preoperative deformity (pre-op. coronal limb alignment, p = 0.002) and decreased ROM (p = 0.042) from the GEE analysis. The second knee also showed more blood loss (735 vs. 656mL), and longer operation time (61, 58 minutes respectively), as compared to the first TKA, while no significant differences in clinical outcomes. Discussion and Conclusion. There were no significant differences in the clinical outcomes even though few distinct outcomes due to different circumstances of the surgery. Awareness of these findings can help the continued success of bilateral TKA in an increasing patient population

Until recently, research has failed to show a difference between posterior-stabilised (PS) and cruciate-retaining (CR) designs in total knee arthroplasty (TKA). This classic debate has been given pause over the past decade due to futile efforts to prove one design superior over the other. Recently, anterior-lipped and more conforming CR bearings have emerged to substitute for the PCL, if absent, damaged or resected, and obviate the need for the archaic cam-post mechanism of a traditional PS design. Advantages of avoiding a PS TKA include decreasing the risk of femoral condylar fracture that may occur via the box cut, as well as decreasing operative time by removing that step in the procedure. Avoiding a post-cam mechanism also removes the articulation that is a source of wear, post deformation, breakage, or dislocation. Patella clunk is also associated solely with PS designs. Modern anterior lipped inserts in PCL-deficient TKAs have demonstrated similar functional outcomes compared to PS knees. A prospective randomised controlled trial of 28 patients undergoing bilateral TKAs had a PS bearing in one knee and a contralateral CS insert with the PCL excised and reported no functional outcome difference at 5-year follow up. Scott and co-authors compared 56 PS TKAs to 55 TKAs with anterior-lipped inserts in a randomised, prospective study and found no functional outcome differences at minimum two-year follow up, with tourniquet times significantly longer in the PS group. In a recent report, 43 anterior-lipped compared to 39 matched PS TKAs had equivalent function scores at minimum 1-year follow-up. Ultra-congruent bearings provide inherent stability in TKA and two studies have reported identical functional outcomes compared to PS TKAs. Finally, there is now recent registry data that demonstrates a significant decrease in long-term survivorship in PS TKAs with a 45% higher risk of revision compared to minimally stabilised bearings in TKA. Equivalent functional outcomes in multiple studies comparing CR-type bearings and PS TKAs, combined with the potential deleterious outcomes associated with PS designs and increased risk of revision and decreased long-term survivorship, preclude the need for PS TKA designs in the modern healthcare environment. Hence, PS TKA designs are truly “vestigial organs”, and should be relegated to historical interest

Introduction. Risks and benefits of bilateral total knee arthroplasty (TKA), whether simultaneous, sequential single-staged, or staged is a topic of debate. Similarly, computer-assisted navigation for TKA is controversial regarding complications, cost-effectiveness, and benefits over conventional TKA. To our knowledge, no studies have compared computer-assisted and conventional techniques for sequential bilateral TKA. We hypothesise that the computer-assisted technique has fewer complications. Methods. We retrospectively reviewed 40 computer-assisted and 36 conventional bilateral sequential TKAs from 2007–2011 with 1 year follow-up for complications. Groups were matched by age, gender, body mass index (BMI), Charlson Comorbidity Index (CCI), and American Society of Anesthesiologists Classification (ASA). Pearson's Chi-square, Fisher's exact test, and independent samples t-test were used to compare groups. Results. Our populations' mean age was 65.9 years, BMI 31.6, CCI 3.4, ASA 2.3, and a male to female ratio of 1:2. Computer-assisted demonstrated significantly better postoperative day (POD) 1 hemoglobin (p=.001), decreased number of blood transfusions (p=.001) and fewer complications (p=.023). Mean preoperative hemoglobin (Hgb) for both groups was 12.4 g/dL, but mean POD1 Hgb was 10.2 g/dL and 9.3 g/dL, for computer-assisted and conventional groups respectively. Total blood transfusion units were a mean of 1.0 and 1.7 for computer-assisted and conventional groups respectively. Seven (19%) patients in the conventional group had lethargy, altered mental status (AMS), or syncope versus none in the computer-assisted group. Subsequent Hgb levels, tourniquet time, length of stay, readmissions, and reoperations were not significantly different with numbers available between the two groups. Conclusion. Computer-assisted sequential bilateral TKAs had higher Hgb on POD1 and lower blood transfusions and complications. This may be due to violation of the femoral canal causing increased bleeding using the conventional technique. Fat emboli from the femur may have caused AMS, but did not increase incidence of pulmonary embolism in the conventional group

Until recently, research has failed to show a difference between posterior-stabilised (PS) and cruciate-retaining (CR) designs in total knee arthroplasty (TKA). This classic debate has been given pause over the past decade due to futile efforts to prove one design superior over the other. Recently, anterior-lipped and more conforming CR bearings have emerged to substitute for the PCL, if absent, damaged or resected, and obviate the need for the archaic cam-post mechanism of a traditional PS design. Advantages of avoiding a PS TKA include decreasing the risk of femoral condylar fracture that may occur via the box cut, as well as decreasing operative time by removing that step in the procedure. Avoiding a post-cam mechanism also removes the articulation that is a source of wear, post deformation, breakage, or dislocation. Patella clunk is also associated solely with PS designs. Modern anterior lipped inserts in PCL-deficient TKAs (CS) have demonstrated similar functional outcomes compared to PS knees. A prospective randomised controlled trial of 28 patients undergoing bilateral TKAs had a PS bearing in one knee and a contralateral CS insert with the PCL excised and reported no functional outcome difference at 5-year follow up. Scott and co-authors compared 56 PS TKAs to 55 TKAs with anterior-lipped inserts in a randomised, prospective study and found no functional outcome differences at minimum two-year follow up with tourniquet times significantly longer in the PS group. In a recent report, 43 anterior-lipped compared to 39 matched PS TKAs had equivalent function scores at minimum 1-year follow-up. Ultra-congruent bearings provide inherent stability in TKA and two studies have reported identical functional outcomes compared to PS TKAs. Equivalent functional outcomes in multiple studies comparing CR-type bearings and PS TKAs, combined with the potential deleterious outcomes associated with PS designs, preclude the need for PS TKA designs in the modern health care environment. Hence, PS TKA designs are truly “vestigial organs”, and should be relegated to historical interest

Until recently, research has failed to show a difference between posterior-stabilised (PS) and cruciate-retaining (CR) designs in total knee arthroplasty (TKA). This classic debate has been given pause over the past decade due to futile efforts to prove one design superior over the other. Recently, anterior-lipped and more conforming CR bearings have emerged to substitute for the PCL, if absent, damaged or resected, and obviate the need for the archaic cam-post mechanism of a traditional PS design. Advantages of avoiding a PS TKA include decreasing the risk of femoral condylar fracture that may occur via the box cut, as well as decreasing operative time by removing that step in the procedure. Avoiding a post-cam mechanism also removes the articulation that is a source of wear, post deformation, breakage, or dislocation. Patella clunk is also associated solely with PS designs. Anterior lipped inserts in PCL-deficient TKAs have demonstrated similar functional outcomes compared to PS knees. A prospective randomised controlled trial of 28 patients undergoing bilateral TKAs had a PS bearing in one knee and a contralateral CS insert with the PCL excised and reported no functional outcome difference at 5-year follow up. Scott and co-authors compared 56 PS TKAs to 55 TKAs with anterior-lipped inserts in a randomised, prospective study and found no functional outcome differences at minimum two-year follow up, with tourniquet times significantly longer in the PS group. In a recent report, 43 anterior-lipped compared to 39 matched PS TKAs had equivalent function scores at minimum 1-year follow-up. Ultra-congruent bearings provide inherent stability in TKA and two studies have reported identical functional outcomes compared to PS TKAs. Equivalent functional outcomes in multiple studies comparing CR-type bearings and PS TKAs, combined with the potential deleterious outcomes associated with PS designs, preclude the need for PS TKA designs in the modern healthcare environment. Hence, PS TKA designs are truly “vestigial organs” and should be relegated to historical interest

Aims. This study was conducted to investigate the influence of surgical experience on the outcomes and component positioning of total knee arthroplasty (TKA). We compared the outcomes and component positioning of simultaneous bilateral TKAs performed by supervisors and trainee surgeons. Patients and Methods. A total of 20 patients (40 knees) who underwent simultaneous bilateral primary TKA using the same cruciate-retaining TKA system between 2011 and 2015 were included. The mean patient age was 76 years (range: 64 to 86 years). There were 2 males and 18 females. The first phase of the operation was performed on the knee that was more severely degenerated by one supervisor who had performed over 1000 TKAs. The other knee was operated on next by trainee surgeons who had performed less than 20 TKAs. The knees were categorized into two groups: those operated on by supervisors (group S) and those operated on by trainee surgeons (group T). Outcome measures included range of motion (ROM), Knee Score (KS), and Function Score (FS). We also evaluated operative time, alignment of the leg, and the orientation of components, which was determined on post-operative long-leg coronal films. Results. The mean pre-operative maximal flexion was 119.8° in group T and 114.8° in group S (p=0.548). The mean pre-operative KS was 47.5 in group T and 35.6 in group S (p<0.01). The mean operative time was 124.5 min in group T and 91.8 min in group S (p<0.01). The mean post-operative maximal flexion was 114.0° in group T and 113.0° in group S (p=0.967). The mean post-operative KS was 93.9 in group T and 92.9 in group S (p=0.978). There were no significant differences in the ROM and KS when comparing supervisor and trainee surgeons. The overall mean FS increased to 70 from 42. The varus angle of the mean coronal tibial component was −1.12° in group T and 1.12° in group S (p<0.01). The varus angle of the mean coronal femoral component was 0.24° in group T and 1.82° in group S (p=0.0447). The mean FTA was 172.7° in group T and 176.4° in group S (p<0.01). The mean HKA was 179.2° in group T and 182.9° in group S (p<0.01). Conclusions. Operative time was significantly longer for TKAs performed by trainee surgeons compared to those performed by supervisors. However, alignment for knees in the supervisor group were significantly more likely to be varus compared with those in the trainee group. This study showed no significant difference in ROM and KS between supervisors and trainee surgeons

Over the past twenty years, the Low Contact Stress Rotating Platform (LCS RP) showed good results. Buechel and Pappas invented the Buechel-Pappas Knee (B-P Knee) system that is a modified version of the LCS system with different material (titanium), axial rotation limiting bar and improved conformity. The purpose of this prospective randomized study was to compare the 2-year clinical outcomes between two implants in the same patients who had been operated with bilateral TKAs. We prospectively enrolled 107 patients and 18 patients were lost to follow-up. Therefore, 89 patients (178 knees; mean age, 69.8±6.0years) were included in the study. The range of motion and clinical scores such as Knee Society score (KSS), Hospital for Special Surgery score (HSS) and Western Ontario and McMaster University (WOMAC) scores were measured preoperatively and postoperatively. At each follow-up, patients also complete a Likert scale questionnaire regarding subjective pain, lightness, left-right side preference (naturalness and satisfaction) and subjective instability. There were no significant differences in all preoperative variables between the two groups(P<.05). Mean follow-up period was 29.9±7.2 months. At the 2-year follow-up, mean value of flexion contracture, further flexion and range of motion were not significantly different between both groups. Also, there were no significant differences in the clinical scores and in side to side difference for the feeling of laterality between two groups(P<.05). After minimum 2-year follow-up, we found no differences in early clinical outcomes as well as subjective side to side difference between the LCS RP and B-P Knee system in this study

Introduction. A femoral rotational alignment is one of the essential factors, affecting the postoperative knee balance and patellofemoral tracking in total knee arthroplasty (TKA). To obtain an adequate alignment, the femoral component must be implanted parallel to the surgical epicondylar axis (SEA). We have developed “a superimposable Computed Tomography (CT) scan-based template”, in which the SEA is drawn on a distal femoral cross section of the CT image at the assumed bone resection level, to determine the precise SEA. Therefore, the objective of this study was to evaluate the accuracy of the rotational alignment of the femoral component positioned with the superimposed template in TKA. Patients and methods. Twenty-six consecutive TKA patients, including 4 females with bilateral TKAs were enrolled. To prepare a template, all knees received CT scans with a 2.5 mm slice thickness preoperatively. Serial three slices of the CT images, in which the medial epicondyle and/or lateral epicondyle were visible, were selected. Then, these images were merged into a single image onto which the SEA was drawn. Thereafter, another serial two CT images, which were taken at approximately 9 mm proximal from the femoral condyles, were also selected, and the earlier drawn SEA was traced onto each of these pictures. These pictures with the SEA were then printed out onto transparent sheets to be used as potential “templates” (Fig. 1-a). In the TKA, the distal femur was resected with the modified measured resection technique. Then, one template, whichever of the two potential templates, was closer to the actual shape, was selected and its SEA was duplicated onto the distal femoral surface (Fig. 1-b). Following that, the distal femur was resected parallel to this SEA. The rotational alignment of the femoral component was evaluated with CT scan postoperatively. For convention, an external rotation of the femoral component from the SEA was given a positive numerical value, and an internal rotation was given a negative numerical value. Results. The subjects were 4 knees in 4 males and 26 knees in 22 females. A mean age (for 30 knees) at the operation was 76.7 ± 6.1 years (range from 66.4 to 88.3). The posterior condylar angle was −0.27 ± 1.43, and the outlier, more than 3 degrees, was 1 case. Discussion. Conventionally, the SEA is palpated intraoperatively, however, the sulcus of the medial condyle sometimes cannot be identified precisely in osteoarthritic degeneration at the medial condyle. Also, the SEA is determined from the posterior condylar axis (PCA) by calculating the posterior condylar angle, which is between the SEA and the PCA, with the measurements from the preoperative CT scan. However, the residual cartilage thickness is not considered in this method, and thus, the SEA is possible to be inaccurate. The simple technology of our template allowed us to determine the SEA directly on the femoral surface, without any influence from bone degeneration. The femoral components could be implanted accurately, and therefore, the superimposed template was considered to improve TKA outcomes with the accurate SEA

BACKGROUND. This study aims to identify recent trends in discharge disposition following bilateral total knee arthroplasty (TKA) as well as factors that predispose patients to enter inpatient rehabilitation facilities (IRF) or skilled nursing facilities (SNF) versus home-rehabilitation (HR). The goal was to identify risk factors that predispose prolonged hospital stays and identify changes in management over time that may be responsible for decreased length of stay (LOS) and a HR program. METHODS. A retrospective cohort study design was used to collect and analyze clinical and demographic data for 404 consecutive bilateral primary total knee arthroplasty (TKA) procedures. Patients who underwent elective primary bilateral total knee arthroplasty from 2011 to 2016 were identified from hospital records at a single institution. Clinical and demographic data including sex, age, and disposition were analyzed. RESULTS. 404 bilateral TKAs were performed by 17 surgeons at a single institution from 2011 to 2016. The average age for bilateral TKA was 63y (31.4–86.6) and 59% were females (239/404). From 2011 to 2016, an increase of 61% (10% to 71%) was noted with regards to home discharge (22.035, <0.001), as well as an increase in the ratio of males being discharged home vs IRF/SNF (1.04 vs 2.4; 2.304, 0.008). Univariate analysis for factors associated with home discharge showed significance for age <60y (3.781, <0.001), age >70 (0.118, 0.001), the use of TXA (3.52, <0.001), type of implant (6.055, <0.001), low postoperative Hg (0.333, <0.001), and yearly trend (Pearson: 0.322, <0.001). Factors associated with prolonged LOS included age <60y (0.641, 0.029), age >70 (1.723, 0.032), active cancer (0.256, 0.027), low postoperative Hg (1.674, 0.020), and postoperative transfusion (1.667, 0.015). Multivariate regression for factors associated with a home discharge showed aggregate significance for BMI <25 (0.886, 0.024), use of TXA (1.139, <0.001), type of implant (1.310, 0.008), age <60 (0.956, 0.004), and age >70 (−1.627, 0.036). Multivariate logistic regression for factors associated with a prolonged LOS showed aggregate significance for active cancer (−1.654, 0.015), postoperative transfusion (0.485, 0.023), and age >70 (0.600, 0.024). CONCLUSION. There has been a significant trend towards postoperative home-rehabilitation programs rather than inpatient rehabilitation following bilateral total knee arthroplasty. There has also been a trend towards an increasing age for those undergoing bilateral total knee arthroplasty. Factors predisposing patients towards non-home discharge disposition include increased age and female gender. The increased use of both TXA and patient specific implants has led to a decrease in operative time and postoperative transfusion rates, and thus a decrease in the overall length of inpatient hospital stay

There is ample data to confirm that Computer-assisted total knee replacement improves alignment of the limb when compared with the conventional technique. There is also published evidence that optimum alignment correlates with longevity of implants. CAS enables accurate component alignment of both femoral and tibial components. It enables accurate restoration of the posterior tibial slope which has important consequences for flexion range and stability of the component in flexion especially if mobile bearing implants are considered. CAS also aids in correctly orienting rotation of the femoral component; this has value in minimizing patellar maltracking. We will present our data showing accurate restoration of joint line and posterior femoral offset. As CAS ensures alignment, rotation, sizing and positioning of components, the surgeon is free to devote his efforts to ensuring soft-tissue balance and stability, since TKA is really a ‘soft-tissue’ operation. How CAS is of immense value in deformity correction and soft-tissue balancing will be illustrated with examples. It helps in better understanding and quantification of the effects of soft-tissue release on flexion-extension gaps and this is of great value not only for minimal deformities (to minimise releases) but also for severe deformities (to ensure complete correction by adequate release). CAS is invaluable in helping equalize flexion-extension gaps; how it can help balance the flexion gap to the extension gap by ‘virtual surgery’ will be depicted with examples. It is particularly useful in presence of hardware in the femur or tibia and for concomitant extra-articular deformity. We have also found a consistent improvement in recovery of functional milestones with CAS with similar results for both unilateral and bilateral TKAs. Furthermore, there is evidence to support that ensuring alignment has important benefits in improving functional and quality of life scores. In addition, those with alignment of mechanical axis within 3 degrees of normal have been shown to have a shorter stay in hospital by 2 days. Studies have shown reduced blood loss and incidence of emboli after CAS TKA. Using CAS routinely for all cases, the author is ‘time neutral’. While there is always room for improvement with evolving technologies and CAS is no exception, it already has enormous benefits in the performance and outcome of TKA, and is an important part of the surgical armamentarium for a successful knee arthroplasty

Over the past decade, there has been an increase in the number of total knee arthropalsty (TKA). Demand of TKA for the young patients who often have high physical demands is also increasing. However, the revision rate in such young patients is much higher due to polyethylene (PE) wear and instability (Julin J, Acta Orthop 2010). Therefore, next generation total knee prostheses are expected to decrease PE wear and to provide stability. Although in vitro study such as wear simulator test provides important information about PE wear, we have often encountered the discrepancy between the in vitro results and in vivo results. Thus we have performed in vivo PE wear particle analysis, and showed that in vivo PE wear was affected by the design of articulating surface and the materials of femoral component and PE insert (Minoda Y, JBJS Am 2009). Medial pivot design, ceramic femoral component, and highly cross-linked PE decreased in vivo PE wear particle generation. Patients who underwent bilateral staged TKAs were more likely to prefer medial pivot prosthesis or ACL-PCL retaining prosthesis than the other types of prostheses, because they feels “more stable overall” (Pritchett JW, J Arthroplasty 2011). In vivo fluoroscopic 3D analysis showed that medical pivot and bi-cruciate substituting designs restored physiological knee motion and provided higher reproducibility (Mueller J. Komistek RD, Trans ORS 2009, Iwakiri K, Trans ORS 2007). The excellent mid-term clinical results of those newly introduced total knee prosthesis, such as alumina medial pivot TKA (Iida T, ORS 2008), medial pivot TKA (Mannan K, JBJS Br 2009, Kakachalions T, Knee 2009), ACL-PCL retaining TKA (Clouter JM, JBJS Am 1999), and highly cross-linked PE (Hodrick JT, CORR 2008), have been reported. From the point of view of in vivo PE wear, in vivo stability, and the mid-term clinical results, we suspect that medial pivot prosthesis is one of the prostheses which meet the demand in future especially for young active patients