Introduction. Malrotation following total knee replacement is directly related to poor outcome. The knowledge of proximal and distal rotational axes and angles of the femur is therefore of high importance. The aim of the study was to determine whether the most used proximal and distal femoral angles; femoral anteversion angle (FAA) and posterior condylar angle (PCA) were different within individuals, between right, left and gender. As well, we studied whether the “inferior condylar angle” is correlated to the PCA and therefore useful in determining the rotation of the distal femur. Material and Methods. From 36 cadavers the femora were obtained and after removing the soft tissue a Computed Tomography (CT) scan was made. Three angles were measured: (i) the FAA between femoral columnar line (FHNL) and posterior condylar line (PCL), (ii) the PCA between anatomical transepicondylar line (TEL) and PCL, (iii) the inferior condylar angle (ICA) between the TEL and inferior condylar line (ICL). Statistical analysis of comparative relationships between the different angles was examined by calculating correlation coefficients and a paired t-test. Results. The mean FAA, PCA and ICA for the whole group were respectively 12.0 degrees (range 0.2–31.6, SD 8.3, 95% CI 9.6–14.4), 4.8 degrees (range 0.9–9.6, SD 2.3, 95% CI 4.1–5.4) and 4.5 degrees (range 0.1–9.8, SD 2.1, 95% CI 3.9–5.1). A strong correlation of the FAA was found within the total group and left versus right (r = 0.82; p = 0.00). A weaker relationship was found for the total group of the PCA measurements (r = 0.59; p = 0.00). When FAA compared to the PCA subdivided in only sexes, there is a weak correlation for the female group (r = 0.54; p = 0.00) Despite the small mean difference of the mean ICA and PCA, there was no correlation between these two angles. Conclusion. Considering the weak correlation of the FAA and PCA within the group but also individuals, the importance of development of more individual approaches for determining the optimal rotation of the components in total knee surgery is essential. As a result, one should be aware that the widely used, current guidelines for knee rotation of 3 degrees of external rotation in placing total knee arthroplasties shows variation between individuals. A more individual approach in total knee arthroplasty seems essential for future knee prosthesis implantations

The pourpose of this study was to investigate the variability of the posterior condylar angle and the whiteside’s angle to establish if three degrees of external rotation of the femoral component produce the correct rotational alignment, in varus knee. 33 patients (33 knee) affected by varus osteoarthritic knee (5°–30°)underwent a preoperative CT scan examination of the knee and the hip. On the axial views, we have evaluated the femoral anteversion, the posterior condylar angle and the whitesiede’s angle. The mean femoral anteversion angle was 5.5°±13.7° (−24°;33°). The mean posterior condylar angle was 6.1°±2.5° (1°;14°). The mean intraobserver error was 0.9°. In 60.6% of the cases the angle was greater than 5°. The mean Witheside’s angle was 6°±3.5° (1°;16.5°). The mean intraobserver error was 0.8°. In 51.5% of the cases the angle was greater than 5°. Both the posterior condylar angle and the Whiteside’s angle showed values almost double than three degrees proposed as standard rotation for the femoral component. The method of three degrees standard of external rotation lead to relative internal rotation of the femoral component in TKR also for varus knee

Patello-femoral tracking and polyethylene wear are strongly dependent on rotational alignment of the components in total knee arthroplasty. In the current literature four methods to obtain correct axial femoral alignment are reported: the transepicondylar axis method, Whiteside’s method, the tibial axis method and 3° external rotation of posterior condyles method. Because of its simplicity the last of these is the most popular method used at present. But it is also the most accurate? The purpose of this study was to investigate the accuracy of the 3° external rotation method, comparing it to the transepicondylar axis and the White-side’s A-P line. We performed a CT scan examination of the hip and the knee of 40 patients scheduled to undergo a total knee arthroplasty. Seven cases of valgus deformity were excluded from the study, leaving 34 cases. The mean age was 72.4 and the left knee was involved in 23 cases. The mean height was 159 cm and the mean weight was 76.6 kg. The mean varus deformity was 14° (min 5° – max 30°). CT scan was conducted using a Picker PQCT machine. Two axial images were obtained in all the patients: one of the femoral neck and one of the knee with good visualisation of the posterior aspect of the condyles of the femur and epicondyles. We measured the following angles: the femoral anteversion angle (between the femoral neck line and the posterior condylar line), the posterior condylar angle (between the posterior condylar line and the transepicondylar axis) and the Whiteside’s angle (between the posterior condylar line and the perpendicular line to the White-side’s A-P line). The mean femoral anteversion angle was 5.5°± 13.7° (min -24°; max 33°). The mean posterior condylar angle was 6.1°± 2.5° (min 1°; max 14°). In 20 cases (60.6%) the posterior condylar angle was greater than 5°. The mean Whiteside’s angle was 6°±3.5° (min 1°; max 16.5°). In 17 cases (51.5%) it was greater than 5°. Both the posterior condylar angle and the White-side’s angle showed average values, which doubled the 3° proposed as standard for external rotational alignment of the femoral component, with maximum values of 14° and 16.5° respectively. More than 50% of the cases showed a posterior condylar angle grater than 5°. The two methods (transepicondylar and Whiteside’s line) are complementary. The posterior condylar axis and the Whiteside’s line were not altered by severe varus deformity or femoral neck retro- or anteversion. The 3° external rotation of the posterior condyle line is not recommended as a standard procedure to determine the degree of external rotation of the femoral component in total knee arthroplasty

Introduction and Objective. The geometry of the proximal tibia and distal femur is intimately linked with the biomechanics of the knee and it is to be considered in total knee arthroplasty (TKA) component positioning. The aim of the present study was to evaluate the proximal tibial torsion in relation to the flexion-extension axis of the knee in healthy and pathological cohort affected by knee osteoarthritis (OA). Materials and Methods. We retrospectively analyzed computed tomography scans of OA knee of 59 patients prior to TKA and non-arthritic knee of 39 patients as control. Posterior condylar angle (PCA), femoral tibial torsion (TEAs-PTC and TEAs-PTT), proximal tibial torsion (PTC-PTT and PCAx-PTC) and distance between tibial tuberosity and the trochlear groove (TT-TG) were measured. Results. No differences were found for gender, age, TG-TT and PCAn angles. Statistically significant differences were found for all the other angles considered. Significant relation was found between Tibial Torsion and TEA-PTT angles, between PCAx-PTC and TEA-PTC, between TEA-PTT and TEA-PTC and between PCAx-PTC and TEA-PTT. All measures, except TG-TT and PCAn angles, showed high validity (AUC > 75%) in detecting OA, with TEA-PTT displaying the highest validity with an AUC of 94.38%. Conclusions. This is the first study to find significant differences in terms of proximal tibia geometry and anatomy between non arthritic and OA knees. It is conceivable that such anatomy could be implicated in the development of OA. Based on our data, the TEAs is a valid reference for correct positioning of tibial component in TKA. Indeed, setting the tibial component parallel to TEAs makes the prosthetic knee more similar to the native non-arthritic knee

Background. Finding the anatomical landmarks used for correct femoral rotational alignment can be difficult. The Posterior Condylar Line (PCL) is probably the easiest to find during surgery. The aim of this study was to analyze if a predetermined fixed angle referencing of the PCL could help obtain good femoral alignment in TKA patients. Methods. 2637 CT scans used for preoperative planning and creation of patient-specific instrumentation (PSI) were used to analyze the Posterior Condylar Angle (PCA) between the Surgical Epicondylar Axis (SEA) and the PCL. Results. The mean PCA was 3.99° +/− 1.35° of external rotation. A significant relation was found between more external rotation and more varus of the tibia and more valgus of the femur. In 132 patients bilateral CT's were available and 94 (71%) had rotation within 1° of the opposite side. 96% of patients would receive the right amount of external rotation with 6°. On 105 (4%) CT's external rotation between 7° to 11° was measured and 77 (73%) of those were in varus or neutral alignment. Conclusions. After substracting a correction of 1° for cartilage remnants, a posterior condylar angle of 5° external rotation is proposed which should cover 96% of the population. For 4% of patients, both varus and valgus knees, 5° of external rotation will not be sufficient. The epicondylar axis should be explored during surgery, determined with patient-specific instruments, or a balancer should be used for this group

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

Aim. The aim of this study is to evaluate the effect of three-dimensional (3D) simulation with 3D planning software ZedKnee® (ZK) in total knee arthroplasty (TKA). Materials and methods. The participants in this study were all TKA patients whose operations were simulated by using ZK. The alignment of all components was evaluated with the ZK valuation software in postoperative computer tomography. Thirty patients (43 knees) met the inclusion criteria. 6 patients were male and 24 patients were female. The mean age of the 30 patients was 72 years old. Diagnoses for surgery were: osteoarthritis- 40 knees, rheumatoid arthritis- 2 knees and osteonecrosis- 1 knee. TKA was performed using the measured resection technique. The distal femur axis where the intramedullary rod would be inserted was drawn manually on the 3D image. Then, the angle between the distal femoral axis and the mechanical axis was measured. The rotational angles of the femoral components were determined from the automatically calculated angle between the posterior condylar axis and the surgical epicondylar axis (SEA) by using ZK. The ZK data used during the operation was the posterior condylar angle, the angle between the distal femoral axis and the mechanical axis and implant size. Results. The angle in coronal plane between the 3D mechanical axis and the distal femoral axis in preoperative planning ranged between 3 degrees and 11 degrees, mean 6.7 (SD 2.2) degrees. The postoperative femoral component alignment was on average 0.7 (SD 1.3) degrees in varus. Outlier of more than 3 degrees in coronal alignment was recognized in 3 cases (7%). The mean posterior condylar angle in preoperative planning was 3.8 (SD 1) degrees. The postoperative femoral component alignment was on average 1.5 (SD 1.6) degrees in external rotation to surgical epicondylar axis. Outlier of more than 3 degrees in rotational alignment was recognized in 6 cases (14%). The concordance rate between the preoperative planning size and the intraoperative selective size was 91%. Discussion. Some errors may be observed in the preoperative TKA X-ray planning, because of the rotational position of the femur while having the X-ray taken or angle of the X-ray beam. Kanekasu et al reported the measurement of the condylar twist angle during the X-ray and it was relatively correct compared with the measurement during CT. Max 1.9 degrees error occurred in the measurements using X-rays. It appeared that preoperative planning using CTs was more accurate than using X-rays. Conclusion. Femoral components with 3D simulation using ZK were fixed perpendicularly against the mechanical axis and parallel to the surgical epicondylar axis with high accuracy. We considered that the ZK 3D simulation in TKA is useful for the accurate alignment of femoral components

Introduction: Currently, minimal attention has been paid to thorough preoperative planning in primary total knee arthroplasty. The aim of this study was to evaluate the results and the effectiveness of a previously reported x-ray view as a simple way of preoperative planning in total knee arthroplasty. Materials & Methods: The rotational alignment of the distal end of the femur is usually evaluated by measuring the angle (posterior condylar angle, PCA) between the surgical transepicondylar axis (TEA) and the posterior condylar line (PC line), which connects the posterior aspects of the femoral condyles. A simple and convenient technique for assessing the TEA and PC line using plain radiography is the kneeling view. The kneeling view has been described as a posteroanterior projection at right angles to the tibial shaft with the knee in approximately 80° of flexion and with the hip joint in neutral rotation. Preoperative planning is possible using the kneeling view in measuring the rotational alignment of the distal femur using the posterior condylar angle. Additionally, information about the varus inclination of the upper part of the tibia may be obtained using the same x-ray view. Kneeling views were obtained in fifty patients with advanced osteoarthritis (classified as 4 on the Kellgren–Lawrence scale) that were admitted in our department for primary TKA. The varus inclination of the upper part of the tibia and condylar twist angle were measured using digital protractors. Results: There was no statistically significant correlation between the posterior condylar angle and the varus inclination of the upper part of the tibia. Bivariate linear regression analysis did not reveal any prediction equation or relation between the two computed variables in advanced osteoarthritic knees. Conclusions: Using this method of preoperative planning, the current practice of cutting the tibia perpendicular to its mechanical axis and applying a predefined external rotation of the femoral component is strongly disputed, especially in advanced osteoarthritic knees. The results of this study show that preoperative planning may be very helpful in assessing the rotational deformity of the distal femur. The final amount of external rotation of the femoral component must be approached on an individual basis based on a thorough preoperative planning

Introduction. Instability, loosening, and patellofemoral pain belong to the main causes for revision of total knee arthroplasty (TKA). Currently, the diagnostic pathway requires various diagnostic techniques such as x-rays, CT or SPECT-CT to reveal the original cause for the failed knee prosthesis, but increase radiation exposure and fail to show soft-tissue structures around TKA. There is a growing demand for a diagnostic tool that is able to simultaneously visualize soft tissue structures, bone, and TKA without radiation exposure. MRI is capable of visualising all the structures in the knee although it is still disturbed by susceptibility artefacts caused by the metal implant. Low-field MRI (0.25T) results in less metal artefacts and offers the ability to visualize the knee in weight-bearing condition. Therefore, the aim of this study is to investigate the possibilities of low field MRI to image, the patellofemoral joint and the prosthesis to evaluate the knee joint in patients with and without complaints after TKA. Method. Ten patients, eight satisfied and two unsatisfied with their primary TKA, (NexGen posterior stabilized, BiometZimmer) were included. The patients were scanned in sagittal, coronal, and transversal direction on a low field MRI scanner (G-scan Brio, 0.25T, Esaote SpA, Italy) in weight-bearing and non-weight-bearing conditions with T1, T2 and PD-weighted metal artefact reducing sequences (TE/TR 12–72/1160–7060, slice thickness 4.0mm, FOV 260×260×120m. 3. , matrix size 224×216). Scans were analysed by two observers for:. - Patellofemoral joint: Caton-Descamps index and Tibial Tuberosity-Trochlear Groove (TT-TG) distance. - Prosthesis malalignment: femoral component rotation using the posterior condylar angle (PCA) and tibial rotation using the Berger angle. Significance of differences in parameters between weight-bearing and non-weight-bearing were calculated with the Wilcoxon rank test. To assess the reliability the inter and intra observer reliability was calculated with a two-way random effects model intra class correlation coefficient (ICC). The two unsatisfied patients underwent revision arthroplasty and intra-operative findings were compared with MRI findings. Results. In the satisfied group, a significant difference was found between TT-TG distance in non-weight-bearing and weight-bearing condition (p=0.018), with a good interrater reliability ICC=0.89. Furthermore, differences between weight-bearing and non-weight-bearing were found for the CD ratio, however, not significant (p=0.093), with a good interrater reliability ICC=0.89. The Berger angle could be measured with an excellent interrater reliability (ICC=0.94). The PCA was hard to assess with a poor interrater reliability (ICC=0.48). For one unsatisfied patient a deviation was found for tibial component rotation, according to the perioperative findings as, ‘malposition of the tibial component’. For the other unsatisfied patient revision surgery was performed due to aseptic loosening in which the MRI showed a notable amount of synovitis. Conclusion. It is possible to image the patellofemoral joint and knee prosthesis with low field MRI. Patellofemoral measurements and tibial component rotation measurements can reliably be performed. For the two patients with complaints MRI findings were consistent with intra-operative findings. Further research should focus on a larger group of patients with complaints after TKA to verify the diagnostic capacity of low field MRI for peri-prosthetic knee problems. For any figures or tables, please contact authors directly

Purpose. External rotation of the femoral component is one factor that favors a satisfactory clinical result. New technologies have been developed to precisely implant the components of a total knee arthroplasty, including computer-assisted surgery (CAS) and patient-specific instruments (PSIs). The aim of this study was to compare the precision of CAS and PSIs when determining the orientation of the femoral component. Methods. A total of 65 patients operated on in 2008 with CAS had pre- and post-operative computed tomography (CT) in which the posterior condylar angle (PCA) was measured. The same pre- and post-operative measurements were performed for 27 patients operated on in 2010 with the assistance of PSI. For both populations, the antero-posterior femoral cuts were directed to implant the femoral component 3° of external rotation from the pre-operative posterior condylar line (PCL). Results. The pre-operative parameters for both groups were identical. The post-operative PCA was not significantly different between the CAS and PSI groups, but the pre- to post-operative difference in PCA for the PSI group indicated a diminution of 2 ± 2° compared to no change in the CAS group. A total of 28% of the patients operated on with CAS had their femoral component more internally rotated after the surgery compared to the pre-operative measurements. Conclusion. Both PSI and CAS achieve the same objective of externally rotate the femoral component in the transversal plan, even if CAS, some femoral components still remains less rotated than the plan

Background. Recent anthropometric studies have suggested that current design of total knee arthroplasty (TKA) does not cater to racial anthropometric differences. The purpose of this study was to investigate the exact sizing and rotational landmarks of the distal femur collected from a large group of healthy Southern Chinese using three dimensional computer tomographic measurements, and then compare these measurements to the known dimensions from Caucasian populations. Methods. This study evaluated distal femoral geometry in 125 healthy Southern Chinese, included 58 women (106 knees) and 67 men (134 knees) with a mean age of 35.2±8.11 years, a mean height of 165.5±7.94 cm, and a mean weight of 61.7±9.56 kg. The width of the articular surface as projected onto the transepicondylar line(ML), anteroposterior dimension (AP), the dimensions from medial/lateral epicondyle to posterior condylar (MEP/LEP)were measured. A characterization of the aspect ratio (ML/AP) was made for distal femur[Fig. 1]. The angles between the tangent line of the posterior condylar surfaces, the Whiteside line, the transepicondylar line, and the trochlear line were measured. The sulcus angle and hip center-femoral shaft angle were also measured. Known dimensions from Caucasian populations were compared with the morphologic data collected in this study[Fig. 2]. In analyzing the data, best-fit lines were calculated with use of least-squares regression. The dimensions are summarized as the mean and standard deviation. The differences of rotational landmarks and sizing between the Southern Chinese and Caucasians were assessed with use of the Student t test. A p value of <0.05 indicated a significant effect. Results. Within the Southern Chineses population, males had larger ML and AP values than females (ML: 70.38±3.09 vs. 62.09±2.52mm, P<0.001; AP: 63.68±2.82 vs. 57.83±2.91mm, P<0.001). The results also showed that Southern Chinese knees were generally smaller than Caucasian (ML: 67.27±4.95 vs. 76.8±7.2mm, P<0.001). The femoral aspect ratio of Southern Chinese was significantly smaller than Caucasian (1.09±0.04 vs. 1.28±0.06, P<0.001). In addition, we found a gradual decrease in the aspect ratio corresponding to an increase in anteroposterior dimension in the distal femur of Southern Chinese, as seen in most other studies. The transepicondylar axis was found to be a reliable landmark to properly rotate the femoral component, so we used the femoral condylar MEP and LEP evaluate posterior condylar offset, the values were respectively 28.62±2.18mm and 22.50±2.19mm. From this study, most of the angles were different from Caucasian. Anteroposterior line minus epicondylar line angle was 90.14±1.30° (Caucasian 90.33±2.44°, P>0.05), anteroposterior line minus posterior condylar line angle was 83.18±1.94° (Caucasian 86.82±2.71°, P<0.001), epicondylar line minus posterior condylar line angle was 7.00±1.70° (Caucasian 3.60±2.02°, P<0.001), trochleoepicondylar angle was 12.45±2.34°(Caucasian 4.95±2.15°, P<0.001), sulcus angle was 147.40±4.69° (Caucasian 139.6±6.96°, P<0.001). The angle between mechanical and anatomic axis of the femur was 5.92±0.47°(Caucasian 6.33±2.42°, P<0.001). Conclusion. Because dimensions of the distal femur and the aspect ratio tend to be smaller in Southern Chinese populations, whereas sulcus angles tend to be larger, designs for knee implants should be modified to improve the outcome of surgical treatment in this population. The Larger epicondylar line minus posterior condylar line angles, and the smaller angle between mechanical and anatomic axis seen in Southern Chinese populations also requires us to pay particular attention to surgical technique, in order to ensure patient safety

Purpose. To validate accuracy of transepicondylar axis as a reference for femoral component rotation in primary total knee arthroplasty. Methods. A prospective study done from dec 2010 to dec 2011 at tertiary centre. 80 knees were included (43 females and 21 males). All surgeries were carried out by one senior arthroplasty surgeon. All patients undergoing primary total knee replacement were included and all revision cases were excluded. Intraoperative assessment of TEA was done by palpating most prominent point on lateral epicondyle and sulcus on medial epicondyle and passing a k wire through it. Confirmation is done under image intensifier C arm with epicondylar view. Postoperative TEA was assessed by taking CT scan, measuring condylar twist angle and posterior condylar angle. Also correlation of femoral component rotation with postoperative anterior knee pain was assessed. Results. The mean PCA was around 4° with TEA as reference and only 10% patients required an additional lateral release of which 2% patient had preop patellar maltracking. No postoperative patellar maltracking was seen. Anterior knee pain was present in 8% patients. No postop infection is noted. Alignment ranging from 3° to 9° external rotation. Conclusion. TEA is most accurate reference for femoral component rotation even in severely deformed arthritic knees. Key words – Transepicondylar axis, total knee arthroplasty, femoral component rotation,

Purpose:. To compare accuracy of transepicondylar axis as a reference for femoral component rotation in primary navigated versus non navigated total knee arthroplasty in severely deformed knees. Methods:. A prospective study done from dec 2009 to dec 2011 at tertiary centre. 180 knees were included (124 females and 56 males). All cases were randomly allocated into 2 groups: navigated and non navigated. All surgeries were carried out by two senior arthroplasty surgeons. All patients undergoing primary total knee replacement were included and all revision cases were excluded. Intraoperative assessment of TEA was done by palpating most prominent point on lateral epicondyle and sulcus on medial epicondyle and passing a k wire through it. Confirmation is done under image intensifier C arm with epicondylar view in Non navigated knees. Postoperative TEA was assessed by taking CT scan, measuring condylar twist angle and posterior condylar angle (PCA). Results:. The mean PCA was around 4° with TEA as reference in Navigated and 6° in Non navigated knees and only 7% patients required an additional lateral release of which 2% patient had preop patellar maltracking. No postoperative patellar maltracking was seen. Anterior knee pain was present in 10% patients. No postop infection is noted. Alignment ranging from 4° to 8° external rotation. Conclusion:. Navigation is most accurate measure for TEA as reference, as compared to non navigated TKA, which can lead to excessive external rotation especially in severely deformed knees

Background. The use of Computed Tomography (CT) as a medical imaging tool has widespread applications in the field of knee surgery. Surgeons use a CT scan in a conventional way during the pre-operative stage, to plan the position of the femoral component in the horizontal plane. In the post-operative stage, the use of a CT scan is a routine tool in the evaluation of failed TKA as rotational malalignment of the femoral component has been determined as a cause of poor clinical outcome after TKA. Aim. How accurately can we measure the different angles with importance for alignment on a 3D-image in comparison to a standard CT, 2D, image. Material and methods. This study includes patients above 55 years of age who were scheduled for a TKA at our centre and who had a pre- and postoperative full-leg length computed tomography (CT). These images were analysed using Mimics V 16.0 ® and 3-matic V 8.0 ® (Materialise, Haasrode, Belgium) to create the surface reconstruction and perform the 3D-measurements. Different angles were measured pre- and post-operatively on these images both in 2D as in 3D: condylar twist angle (CTA), posterior condylar angle (PCA), hip-knee-ankle angle (HKA), tibiofemoral rotation angle (TFRA), posterior tilt of the tibial implant (STPA) and the frontal plane angle of the tibial implant (FTPA). A power analysis showed a needed sample size of 18 patients. Pre-operatively 21 patients were included, 18 of them also received a post-operative full-leg CT. Three observers participated in the study and they all performed all analyses twice with a minimum interval of one week for obtaining intra-observer repeatability. Statistical analysis was performed to obtain the intra- and interobserver variability. Results. The intra-and interobserver intra-class coefficients (ICC) were evaluated using the classification of Landis&Koch (see table). Preoperative results: Rotation of femoral component in 3D: ICC CTA=0,73; ICC PCA=0,66. Rotation in 2D: ICC PCA=0,75, ICC CTA=0,84. The highest ICC was found for the HKA: ICC>0,98 both 2D and 3D. Postoperative results. All ICC's are in the highest category (‘almost perfect’) except for the intraobserver ICC PCA in 2D which was ‘substantial’. Conclusions and clinical implications. CT-evaluation is invaluable for the preoperative planning of the position of the femoral component, for the evaluation of the rotation of the femoral component and for accurate assessment of the overall knee alignment,. This study demonstrates low intra- and inter- observer variability in the CT measurement of the pre- and postoperative alignment of the knee. To determine the rotation of the femoral component preoperatively there was no advantage for 3D over 2D. Post-operatively the use of the 3D technique has a lower variability with regard to the assessment of the rotation of the femoral component

Introduction: Using navigation the AP alignment of a total knee arthroplasty (TKA) improves. However, much less is known on the influence of navigation on the rotation of the femoral component. The rotation of the femoral component is of high importance considering the balancing of the knee and the patellofemoral joint. The aim of our study was to evaluate the accuracy of the femoral component rotation when using navigation. Materials and Methods: We evaluated twenty navigated TKA’s. The Vector Vision system of Brainlab was used during surgery. The preoperative data considering the rotation were stored. On postoperative CT scans the rotation of the femoral component was measured twice at different times by two observers. The posterior condylar angle (the angle between the posterior condylar line and the epicondylar line) was used to define the rotation. The definite position was compared to the per-operative data. The difference between the preoperative determined rotation and the postoperative rotational position was analyzed. The Cohen’s kappa coefficient was used to compare the agreement of results. Results: The postoperative CT scan showed an average measured rotation of the femoral component (posterior condylar angle) of 3,8 degrees. The average rotation based on the navigation data was 5.8 degrees. The difference between the preoperative data and the definite position measured on the CT was 2,8 degrees with a large range. We found a moderate agreement between the two observers and a good agreement within the two observers. Conclusion: The rotation of the femoral component is important in the knee kinematics and patellofemoral joint. Using navigation, it is (yet) not possible to accurately determine or improve the rotational position of the femoral component. Further development of the software and method of determining the epicondylar axis during surgery is needed to be able to improve the rotational position of the femoral component

Introduction: Rotational alignment of the femoral component is widely believed to be crucial for the ultimate success of total knee arthroplasty (TKA). However there is a paucity of normative data on femoral component rotation in ‘perfect’ TKA. Methods: Femoral component rotation in well-functioning TKA was assessed by means of axial radiography as described by Kanekasu et al. Well-functioning TKA were defined by three criteria at 5-year follow-up:. Knee Society objective and functional score of 190 or above. full knee extension and a maximum flexion of 125° or above. excellent subjective patient rating. Thirty TKA of 29 patients (9 male, 20 female) with a median age of 70 years (range, 31–87) at time of surgery fulfilled the study criteria. All TKA were implanted at a single high-volume joint replacement center in 2002. In all cases both the condylar twist angle (CTA) using the clinical epicondylar axis (CEA) and the posterior condylar angle (PCA) using the surgical epicondylar axis (SEA) were used to assess rotational alignment of the femoral component. Results: Overall, the mean CTA was 3.6+−3.5° of internal rotation (IR) (range, 4.1° of external rotation (ER) to 8.6° of IR) for the femoral component. For females, the CTA had a mean value of 4 +/−3.7° of IR (range, 7.6° of IR to 4.1° of ER) compared to 2.3 +/−3° of IR (range, 5.3° of IR to 2.5° of ER) in males. Overall, the mean PCA was 1.5 +/−3.5° of ER (range, 8.4° of ER to 5.1° of IR). In females, the mean PCA was 1 +/−3.9° ER (range, 2.3° of IR to 5.8° of ER) compared to 2.8 +/−2° ER (range, 0.4° of ER to 5.7° of ER) in males. The mean angle between CEA and SEA was overall 5.1 +/−1.8° (range, 3.3° to 9.1°), in females 5.1 +/−1.6° (range, 3.5° to 9.0°) compared to 5.0 +/−2.4° (range, 3.2° to 9.1°) in males. Conclusion: Well-functioning TKA demonstrated a highly variable rotational alignment of the femoral component ranging from excessive external rotation to excessive internal rotation. These findings challenge current reference values for optimal femoral component rotation

Introduction: Rotational alignment of femoral component in TKA affect the clinical results of long-term follow up (Stiehl). Improper alignment may lead to unstable femoro-tibial joint, to wear or loosening of tibial component, and is associated with the subluxation or dislocation of the patella by patella-femoral mal-tracking (Pascal 1996). The precise setting of femoral component is important for the smooth patella tracking and good ligament balancing in TKA. Previously orientation of rotation of the femoral component has been set by equal resection of the posterior condyle (Hungerford 1985, Laskin 1989). The anteroposterior axis of the distal femur that was defined by a line through the deepest part of the patellar groove anteriorly and the center of the intercondylar notch posteriorly, was an easy and reliable landmark of the rotational alignment of the femoral component (Whiteside, Arima). The posterior condylar line (PC line) that connects the posterior condyle of the femur is widely used as a landmark for the cutting of the posterior condyle. Also, 3°external rotation off the posterior femoral condyle has been commonly used as a intraoperative landmark (Laskin1995). The anatomical and functional axis of the femur has been studied so far (Poilvache.Yoshioka1987). Transepicondylar axis (TEA) as the origin of collateral ligament is valuable axis for the parallel cut of the posterior condyle (Berger, Miller). TEA was found to be a reliable landmark to proper rotation of the femoral component, measuring the angle between the axis and the posterior condylar line to orient the femoral component is very important. However, intra-operative manual palpation of the TEA was not reproducible because most prominent point was covered with soft tissue (Jenny). It is sometimes difficult to identify the sulcus of the medial epicondyle accurately with palpation even during surgery (). Therefore, it is crucial to measure and evaluate the TEA as the preoperative planning. The posterior condylar line (PC line) that connects the posterior condyle of the femur is also used for the landmark of the cutting of the posterior condyle. The methods of examining the angle between TEA and PC line are computed tomography (CT) and kneeling view that was simple radiographic technique by Takai et al. Posterior condyle of deformed side makes inaccurate decision of the angle for TEA and PC line because thickness of cartilage and bone are different between medial and lateral condyle. PCA is not applicable in MIS-TKA because it is very difficult to visualize the posterior condyle in the lateral side by the medial approach. Alternative landmark of the angle between TEA and anterior trochlear line of lateral and medial femoral condyles for the determination of rotational positioning of the femoral component may be considered. We have improved the simple radiographic view of evaluating the TEA and PC line but also anterior trochlear line for the assessment of rotational alignment of the distal femur in TKA. The purpose of this study was to measure these angles and to evaluate the reliabilities in compared with 3D-CT. Subjects and methods Our new radiograph we describe is the antero-posterior view of looked-up distal femur. The patient lies on the supine position and flexes the knee about 130 degrees as much as possible. X-ray is applied to the knee at the right angle to the front of the skin from 20 degrees bottom (Figure 1). We pointed out the location of the anterior surface of the condyles, medial epicondyle and lateral epicondyle. We marked the medial and lateral epicondyle of anterior surface of condyles, and posterior condyles as the indivisual reference points in these views. We defined the anterior intercondylar line (trochlear line) as the most axial projections of the medial and lateral femoral condyles. We defined PC line as a line connecting the surfaces of the subarticular cortex of the medial and lateral posterior femoral condyles likewise. We used to obtain clinical TEA that was defined by drawing the most prominent points of the medial and lateral epicondyles. We measured the external rotational angle between PC line and clinical TEA (condylar twist angle), and the internal rotational angle between clinical TEA and trochlear line (Figure 2). Reproducibility of our radiographic technique We examined the reproducibility of our new radiographical technique by 20 healthy volunteers. They included ? males and ? females and the average age of the patients was # years (# ~ # years). No knees in volunteers showed remarkable deformities. We photographed at the flexion angle from 110 to 140 degrees every 10 degrees, at the incident angle of 20 and 30 degrees. The anterior trochlear line, PC line and clinical TEA were drawn on the images and measured condylar twist angle and the internal rotation angle between clinical TEA and trochlear line. The differences of their measurements were quantified using paired t-test. Comparison with our view and reconstruction images of 3-dimensional helical CT system The CT images of 35 knee joints in 28 patients had been taken at full extension of the knee using 512 × 512 pixel matrix, in addition of plain X-ray. From the data of CT images, two different images were acquired such as the composition images and the reconstruction images of 3D. The composition images were obtained by putting a photograph with slices of every 2 mm on top of one another. The CT slices (Shimazu Co Ltd, Kyoto, Japan) obtained from the proximal edge of the patella to the joint line of the knee. We added anterior surface of condyles, medial epicondyle, lateral epicondyle and posterior condyles on tracing paper every slice in the same place. Then we drawn trochlear line, PC line and clinical TEA, and measured the external rotation angle between PC line and clinical TEA (condylar twist angle) and the internal rotation angle between clinical TEA and trochlear line. The reconstruction images were obtained by the distal femoral view looked-up from distal aspect and reconstructed with 3-dimensional helical CT system. We have drawn trochlear line, PC line, clinical TEA, and measured the external rotation angle between PC line and clinical TEA (condylar twist angle), and the internal rotation angle between clinical TEA and trochlear line from three methods mentioned above and had compared them. The differences of their measurements were compared with three groups. This study involved 122 knees in 82 patients including 22 males and 80 females with osteoarthritis of the knee. The average age of the patients was 67.3 years from 37 to 89 years. We classified by Kellgren and Lawrence classification (K-L grade). They consisted of grade 1; 12 knees, grade 2; 37 knees, grade 3; 34 knees, and grade 4; 39 knees. Tibiofemoral angle (TFA) on long-leg radiography at the standing position were ranged from 164°to 197°; mean, 180.2°±6.7°. We examined the correlation between condylar twist angle and gender, TFA, height and weight. Informed consent. Statistics: Statistical analysis was performed on a personal computer using a statistical software of Statview (SAS institute, Chicago, IL). P values of less than.05 was considered as statistically significant. We used the t-test, which does not need the raw data, to compare our results with those published. We were able to obtain information on the number of subjects (to calculate the degree of freedom) and the mean from the publications. Results: The external rotation angle between PC line and clinical TEA (PC-TEA), that is condylar twist angle (CTA) was 5.6°±2.8°(mean±s.d). The internal rotational angle between clinical TEA and anterior trochlear line (trochlear-TEA) was 5.7°±3.2°. K-L grade was negatively correlated with these rotational angles using Kruskal Wallis test (Table 1). These angles of female was larger than those of male (Table 2). The varus angle was negatively correlated with the CTA (R=−0.30) and positively correlated with the internal rotation angle of trochlear-TEA (R=0.376) (Figure 3). The external rotation angle between PC line and clinical TEA was 5.3°±2.4° at our view, and 5.5°±2.3° at reconstruction images from 3-dimensional helical CT system. The difference of condylar twist angle between plain X-ray and 3D-CT was shown in Figure 4. The internal rotation angle between clinical TEA and anterior trochlear line was 5.3°±2.4° at our view, °and 5.7°±2.3° at reconstruction images from 3-dimentional helical CT system. The difference of the internal rotation angle between clinical TEA and anterior trochlear line between plain X-ray and 3D-CT was shown in Figure 5. Regarding the reproducibility about the flexion angle of the knee and the incident angle, correlation coefficients were ? for the flexion angle of the knee, ? for the incident angle. All cases were within 5° variations of the external rotation angle between PC line and clinical TEA, and 4° variations of the internal rotation angle between clinical TEA and trochlear line, respectively. The case of at 110° flexion and 30° incident angle, however, tends to be more variable than the other cases due to unclear PC line (SD 3.3°; range 3–16°). Discussion: Two kinds of TEAs are used for the reference of femoral rotation on the surgical TEA and the clinical TEA. Surgical TEA is a line connecting the sulcus of the medial epicondyle and the lateral epicondylar prominence (Berger 1993). The posterior condylar angle (PCA) is the angular measurement subtended by the surgical TEA and the posterior condylar line (PCL). The clinical TEA is a line connecting the medial and lateral epicondylar prominence. Clinical twist angle (CTA) is the angular measurement subtended by the clinical TEA and the PCL. The most prominent point of the medial epicondyle that is a landmark of CTA was much better identifiable than the medial sulcus for the landmark of PCA (Suter 2006). The sulcus of the medial epicondyle could only be identified in 53 % of the CT images, however, the most prominent point of the medial epicondyle in CT images was clearly discernible in all knees (Suter 2006). Yoshino et al. recommended the use of the CTA in planning for TKA. Even during surgery the determination of the sulcus is difficult by the palpation (). Medial sulcus become obscures in the severely deformed osteoarthritic knee (Yoshino). . Intra-operative palpation of the trans-epicondylar axis involved a mean of 5° intra- and inter-observer variations (Jenny 2004). Some authors reported that CTA was 3.6° ± 2.02, 3.58° in male and 3.62° in female during TKA (Poilvache), however, in CT study. Arima reported that CTA was 5.7°± 1.7, in cadaver study 4.4° in male and 6.4° in female. In our study, there was significant difference in gender of CTA. There has been only a few reports regarding the angle between the TEA and anterior trochlear line of the lateral and medial femoral condyles (trochleo-epicondylar angle). The line between the most anterior projections of the lateral and medial femoral condyle was called as trochlear line, was measured (Poilvache 1996), trochleo-epicondylar (surgical) angle was 4.95° ± 2.15, 4.4° in male, 5.38° in female during TKA. The mean value of the trochleo-epicondylar angle in CT view was 8.0°± 1.76 of internal rotation in all subjects, 8.8° in male, 7.3° in female, there was significant gender difference (Won). Our developed view is the first method of showing the trochleoepicondylar angle in plain radiography. Our results demonstrated trochleo-epicondylar angle using clinical epicondylar axis was 5.6° ± 2.85 of internal rotation in all subjects, 5.27° in male, 5.77° in female, there was no significant gender difference. Line drawing of posterior condylar line between medial and lateral condyle in osteoarthritic knee sometimes make error of the angle measurement because thickness of cartilage and wear of subchondral bone is not equal in the both side of the condyle. Our view is the first method that is able to examine both the CTA and trochleo-epicondylar angle simultaneously, simple, need not to use special instrument, and reveal reproducible. A minimally invasive operative method in TKA is reported to be effective and recommended in primary OA. However, the reference guide of the angle between PCA and TEA is sometimes difficult to set properly with the full contact of both condyles in the limited view of the non-open side, especially MIS TKA. In contrast, it is easy to set the guide or template properly for the trochlear line angle during the surgery because the anterior trochlear is completely visible. Surgeons should not use only one method of femoral rotational alignment and make appropriate adjustment in TKA (Olcott 2000). Then, we focused on the angle between the anterior trochlear line and TEA,. And we developed the simple method of the radiographic view that is able to evaluate the trochlear line and clinical epicondylar axis as the preoperative surgical planning. From our data, the trochlear line angle with a landmark of the anterior femoral condyle by our radiographic view was reproducible. Our method may be a possible one for determining the rotational alignment of the femoral component in total knee arthroplasty. Regarding the study of variability of these angles in several kinds of flexion angle of the knee and . Therefore, we are able to measure and evaluate both angles, and reduce the measurement error by double-checking the conventional CTA and trochlear line angle