Obtaining a balanced flexion gap with correct femoral component rotation is one of the prerequisites for a successful outcome after total knee replacement (TKR). Different techniques for achieving this have been described. In this study we prospectively compared gap-balancing versus measured resection in terms of reliability and accuracy for femoral component rotation in 96 primary TKRs performed in 96 patients using the Journey system. In 48 patients (18 men and 30 women) with a mean age of 65 years (45 to 85) a tensor device was used to determine rotation. In the second group of 48 patients (14 men and 34 women) with a mean age of 64 years (41 to 86), an ‘adapted’ measured resection technique was used, taking into account the native rotational geometry of the femur as measured on a pre-operative CT scan.

Both groups systematically reproduced a similar external rotation of the femoral component relative to the surgical transepicondylar axis: 2.4° (sd 2.5) in the gap-balancing group and 1.7° (sd 2.1) in the measured resection group (p = 0.134). Both gap-balancing and adapted measured resection techniques proved equally reliable and accurate in determining femoral component rotation after TKR. There was a tendency towards more external rotation in the gap-balancing group, but this difference was not statistically significant (p = 0.134). The number of outliers for our ‘adapted’ measured resection technique was much lower than reported in the literature.

Purpose. The complication of patellofemoral compartment was quite often in total knee arthroplasty. One of the impotant factors in these complications would be the femoral component rotation in TKA. To determine the rotation of the femoral component, the reference of the surgical epicondylar axis (SEA), posterior condylar axis (PCA), AP axis with three dimensional model achieved from computed tomography data were considered. There are some limitations with pre-oprerative CT-based planning such as radio exposure, cost, time and detection of the depth of cartilage. We evaluate the determination of the femoral component rotation with image-free registration method to compare with three-dimensional template system. Material and Methods. Thirty six knees were evaluated to determine the femoral component rotation. The reference points were marked to measure the PCA (posterior condylar axis), SEA (surgical transepicondylar axis), and APA (anteroposterior axis, Whiteside line) intra-operatively and calculated the angle from PCA to SEA and PCA to APA with Image free navigation system (BrainLAB). Those knees were preoperatively evaluated the angle deviation from SEA to PCA with three dimensional template system. These angle deviations, which suggested the femoral component rotation obtained from preoperative template system, were statistically compared with the femoral rotation angle in clinical situation. Results. The mean angle from PCA to SEA was external rotated 2.7 degrees (SD=1.8 degrees) with the template system. During image- free system in TKA, the mean angle from PCA to SEA was external rotated 2.2 degrees (SD=4.5 degrees), and the mean angle from APA to SEA was 0.5 degrees (SD=4.4 degrees). Discussion. The preoperative 3 dimensional template system showed the small ranges and standard deviations in PCA and SEA even when the residual cartilage of the surface at the femur was not considered to evaluate. Meanwhile, the three reference axes obtained from image free navigation system showed the large amount of deviations and thus the variability in these references was difficult to decide the rotation of the femoral component. Now navigation system provided the appropriate gap balance during knee motion. This gap-navigation technique would be one of the keys to obtain the proper rotation of the component

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,

Introduction. Proper femoral component rotation is a crucial factor in successful total knee arthroplasty (TKA). Femoral component rotation using anatomic landmarks has traditionally been established by referencing the transepicondylar axis (TEA), Whiteside's Line (WSL), or the posterior condylar axis (PCA). TEA is thought to best approximate the flexion-axis of the knee, however WSL or PCA are commonly used as surrogates of the TEA in the operating room due to their accessibility. The relationship of these anatomic landmarks has been previously investigated in anatomic and computed tomography based studies. The relatively few knees evaluated have limited the power of these studies. Patient Specific Instrumentation (PSI) utilizing magnetic resonance imaging (MRI) is an emerging technology in total knee replacement. The purpose of this study was to use magnetic resonance imaging based planning software to assess the relationship of WSL and PCA to the TEA and to determine if the relationships were influenced by the magnitude of the pre-operative coronal deformity. Methods. Five hundred sixty total knee replacements were performed in 510 patients utilizing PSI. The Materialize preoperative planning software was utilized to determine the rotational relationships of TEA, WSL, and PCA (Fig 1). The coronal plane deformity of each patient was also evaluated utilizing the MRI-based imaging and planning software. Results. The WSL is externally rotated by 90.36 degrees (SD ±2.3 degrees) compared to the TEA and the PCA is 2.38 degrees (SD ±1.6 degrees) internally rotated compared to the TEA in the overall population (p<0.001). The relationship of WSL to TEA has more variability than the relationship of PCA to TEA. In the overall population only 77% of WSL and 74% of PCA based resection will be within 2 degrees of the TEA. The PCA is more internally rotated in females and in valgus knees (P<0.001) however is not affected by the degree of valgus deformity (p = 0.211). Discussion. Femoral component rotation is determined based on one of three axis options. Classic studies have shown that the TEA is perpendicular to the WSL and the PCA is 3 degrees internally rotated to the TEA. However, there is wide variation in the relationships. Our MRI based evaluation shows that both WSL and PCA approximate the TEA in valgus knees regardless of the degree of deformity. Our study also shows that on average the PCA is 2.38 degrees internally rotated compared to the TEA, not the previously assumed 3 degrees. Our study indicates that the PCA is more internally rotated compared to the TEA in female patients and patients with valgus deformity. Males with varus knees may only require a 2 degree internal rotation correction rather than the historically established 3 degrees. WSL also shows more variability in its relationship to the TEA compared to the PCA. Advanced imaging can assist surgeons in assessing their options for femoral component rotation in TKA. Our data indicates that the relationships of axis options and historical assumptions may need to be reassessed as imaging technology advances

The purpose of this study was to evaluate the femoral component rotation in a small subset of patients who had developed arthrofibrosis after mobile-bearing total knee arthroplasty (TKA). Arthrofibrosis was defined as flexion less than 90 degrees or a flexion contracture greater than 10 degrees following TKA. From a consecutive cohort of 3,058 mobile-bearing TKAs, 49 (1.6%) patients were diagnosed as having arthrofibrosis, of which 38 (86%) could be recruited for clinical assessment. Femoral rotation of a control group of 38 asymptomatic TKA patients matched for age, gender, and body mass index was also evaluated. The surgical epicondylar axis was compared with the posterior condylar axis for the femoral prosthesis. Femoral components in the arthrofibrosis group were significantly internally rotated by a mean of 4.7 degrees (SD 2.2 degrees, range 10 degrees internal to 1 degrees external). In the control group, the femoral component had a mean 0.3 degrees internal rotation (SD 2.3 degrees, range 4 degrees internal to 6 degrees external). Following mobile-bearing TKA, there is a significant correlation between internal femoral component rotation and chronic arthrofibrosis

Purpose. To assesment of geometric center of knee as a reference for femoral component rotation in primary total knee arthroplasty. 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. Postoperative geometric center of knee was assessed by taking CT scan. Results. The mean PCA was around 5° with geometric knee centre axis and 9° in TEA. No postoperative patellar maltracking was seen. Anterior knee pain was present in 7% patients. No postop infection is noted. Alignment ranging from 3° to 12° external rotation. Conclusion. Geometric centre of knee is most accurate measure for referencing of femoral component rotation, as compared TEA, which can lead to excessive external rotation. Key words – Geometric centre of knee, total knee arthroplasty, femoral component rotation

This study was to assess the accuracy of fixed posterior condylar referencing cutting blocks to the accuracy of combined epicondylar/AP axis referencing in femoral component rotation using a computer navigation system. Seventy-five consecutive patients undergoing TKRs were randomized into two groups. The first received femoral component rotation by a computerized method that combined the epicondylar axis and Whitesides AP axis measurements to determine rotation. The second group had a zero or three-degree posterior referencing external rotation block, depending on which was closest to the epicondylar axis. All patients underwent axial CT scans of the distal femur to determine component rotation around the surgical epicondylar axis. Femoral component alignment with the combined method as compared to fixed posterior alignment guides is statistically improved (p=0.001). In the posterior referencing group 43% were correctly rotated to the epicondylar axis but another 43% were malrotated by 3 degrees or more. The mean malrotation was 1.72 degrees (range 0–5) In the combined group 82% were correctly rotated and 11% were malrotated by 3 degrees or more. The mean malrotation was 0.51 degrees (range 0–4). Conclusion: A combined computerized method of using the surgical epicondylar axis and Whitesides AP axis produces superior results when aiming for neutral femoral component rotation. Fixed posterior referencing blocks will produce errors in malrotation in over 50% of cases

Introduction. Most surgeons utilize one of three axis options in conventional total knee arthroplasty (TKA), the transepicondylar axis (TEA), Whiteside's line (WSL) or the posterior condylar axis (PCA) with an external rotation correction factor. Each option has limitations and no clear algorithm has been determined for which option to use and when. Many surgeons believe the TEA to be the gold standard for determining rotation however it can be difficult to access intraoperatively. WSL and PCA have been used as surrogates for determining axial rotation in conventional TKA but may also be prone to error. MRI based preoperative planning systems overcome intraoperative limitations while accounting for the individual anatomy of each patient, thus helping optimize femoral component rotation. The goal of this study was to examine if coronal plane deformity had any effect on the relationship of conventional referencing options such as WSL and PCA to the TEA. Methods. Utilizing a preoperative planning software based on MRI, we compared the preoperative posterior femoral condyle resections for three different axis options in 176 TKA. The difference in bone resection amount was used to determine the rotational differences between the axis options in all knees. Assuming that the TEA was the ideal rotational axis, we compared the TEA to both WSL and PCA. A 1-sample t-test and paired t-test were then used to determine if there was a significant rotational difference between the various axis options when accounting for degree and direction of preoperative deformity in the coronal plane. Results. In the overall population of 176 knees (42 valgus, 134 varus), neither WSL or PCA approximated the TEA accurately (p=0.016 and 0.001). In valgus deformity, WSL was found to approximate the TEA (p=0.68) better than the PCA (p=0.21). Minor varus deformity (< 3 degrees) favored the use of PCA (0.53) while moderate varus deformity (3–6 degrees) favored use of WSL (p=0.76). Severe varus (>6 degrees) deformity favored use of PCA due to lower variability. For complete results see Figure 2. Conclusion. Based on MRI data, our study indicates that preoperative coronal plane deformity should help determine the specific referencing option utilized for femoral component rotation in TKA. Broad application of either WSL or the PCA to all patients regardless of preoperative deformity did not accurately approximate TEA in femoral component rotation. Rather, analysis of the degree and direction of preoperative coronal plane deformity indicates that WSL and PCA should be used in specific scenarios to approximate the TEA. When WSL or PCA either both approximate or do not approximate the TEA, we recommend using the option with a lower standard deviation, and thus less variability. Although this MRI based technology is not in widespread use, we believe our findings (Figure 1) can assist the majority of surgeons determine when to use WSL or the PCA based on preoperative coronal plane deformity

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. 11%–19% of patients are unsatisfied with outcomes from Total Knee Arthroplasty (TKA). This may be due to problems of alignment or soft-tissue balancing. In TKA, often a neutral mechanical axis is established followed by soft tissue releases to balance and match the flexion/extension gaps with the distal femoral and proximal tibial resections at right angles to the mechanical axis. Potential issues with establishment of soft tissue balance are due to associated structures such as bone tissue of the knee, the static (or passive) stabilizers of the joint (medial and lateral collateral ligaments, capsule, and anterior and posterior cruciate ligaments), and the dynamic (or active) stabilizers around the knee. An optimized balance among these systems is crucial to the successful outcome of a TKA. Additionally, the importance of correct femoral rotation has been well documented due to its effect on patella alignment and flexion instability, range of motion, and polyethylene wear. There are several methods used in TKA procedures to establish femoral component rotation. The more prominent ones are a conventional method of referencing to the posterior condylar axis with a standard external rotation of 3° (PCR), anterior-posterior line or “Whiteside's line” (AP axis), transepicondylar axis (TEA) (Figure 1), and the gap balancing technique, however, it is not yet clear, which method is superior for femoral rotational component alignment. In the current study, we sought to investigate an alternative method based on soft-tissue, dynamic knee balancing (DKB) while using an alternative analysis approach. DKB dictates femoral component rotation on the basis of ligament balance and force measures. DKB has become more prominent in TKA surgeries. While retaining ligament balance in TKA, it is possible that this technique also leads to higher precision of rotational alignment to the anatomical axis. The primary objective of this study was to compare efficiency of DKB versus other methods for rotational implant alignment based on post-surgery computed tomography (CT). Methods. 31 patients underwent computer-navigated total knee arthroplasty for osteoarthritis with femoral rotation established via a flexion gap balance device (Synvasive eLibra). Alternative, hypothetical alignments were assessed based on anatomical landmarks during the surgery. Postoperative computed tomography (CT) scans were analyzed to investigate post-surgery rotational alignment. Repeated measures ANOVA and Cochran's Q test were utilized to test differences between the DKB method and the other techniques. Results. Significant differences were observed between the DKB method and TEA method (p=0.02), between DKB and AP method (p=0.04), and DKB and PCR method (p=0.02): The DKB method showed the lowest rotational deviation from CT-determined true anatomical TEA (aTEA)(Figure 2). The DKB method established femoral rotation within ±3 more often than the other techniques (Figure 3), further analysis revealed a significant proportional difference between DKB and PCR method (p=0.01), between DKB and TEA (p=0.02) and DKB and AP (p=0.04). Conclusions. DKB showed promising results in our study regarding femoral rotation accuracy in comparison to other methods. DKB may be a valuable tool due to its ability to establish soft-tissue balance in addition to high accuracy of femoral rotation

This study measured the three bony axes usually used for femoral component rotation in total knee arthroplasty and compared the accuracy and repeatability of different measurement techniques. Fresh cadaveric limbs (n=6) were used. Three observers (student, trainee and consultant) identified the posterior condylar (PCA), anteroposterior (AP) and the transepicondylar (TEA) axes, using a computer navigation system to record measurements. The AP axis was measured before and after being identified with an ink line. The TEA was measured by palpation of the epicondyles both before and after an incision was made in the medial and lateral gutters at the level of the epicondyles, allowing the index finger to be passed behind the gutters. In addition the true TEA was identified after dissection of all the soft tissues. Each measurement was repeated three times. For all axes and each observer the repeatability coefficient was calculated. The identification of the PCA was the most reliable (repeatability coefficient: 1.1°) followed by the AP after drawing the ink line (4.5°) then the AP before (5.7°) and lastly the TEA (12.3°) which showed no improvement with the incisions (13.0°). In general the inter-observer variability for each axis was small (average 3.3°, range 0.4° to 6°), being best for the consultant and worst for the student. In comparison to the true TEA, the recorded TEA and AP axis averaged within 1.5° whilst the PCA was consistently 2.8° or more internally rotated. This study echoed previous studies in demonstrating that palpating the PCA intra-operatively is highly precise but was prone to errors in representing the true TEA if there was asymmetrical condylar erosion. The TEA was highly variable irrespective of observer ability and experience. The line perpendicular line to the AP axis most closely paralleled the true TEA when measured after being identified with an ink line

Introduction. In total knee arthroplasty (TKA), the setting position of component and the angle influence surgical results. 3D matching evaluation method using the CT before and after operation was a useful method as a rating system after operation. The anterior femoral cortical line (AFCL) is an anatomical landmark for determining intraoperative femoral component rotation in total knee arthroplasty (Fig.1). Our aim in this study is to evaluate the effectiveness of the JIGEN (Jig Engaged 3D Pre-Operative Planning System for TKA) (LEXI, Japan) operation support system using AFCL. Patients and methods. We performed TKA used GENUS MB (Adler, Italy) by January, 2015 from October, 2013. As for 5 male knees, 37 woman knees, the operation average age were 68 years old. The operation was based on each insertion parameter of the rod in marrow provided by a preoperative plan by the JIGEN system and at first installed a target device in the femoral front and manufactured a insertion point and inserted a rod in the marrow to plan insertion depth (Figure 1). We performed CT photography of the whole lower limbs after operation like preoperation and femoral component setting was located after operation using evaluation software (LEXI, Japan) and evaluated it. Result. In the 3D evaluation, femoral components implanted less than 3 degrees were 98% in the coronal plane, 67% in the sagittal plane, and 79% in the axial plane (Figure 2). The rotational malposition of femoral component was found in the case that the distal femoral front was round. Conclusion. The JIGEN system is useful for operation support in TKA. AFCL has the advantages of easy access and because of its extra-articular position is not affected by articular cartilage or processes that destroy the joint (such as degeneration or osteolysis). We considered that the JIGEN system using AFCL can be effective for determining intraoperative femoral component rotation in TKA

Purpose: To assess the anterior femoral cortical line (AFCL) as an additional anatomical landmark for determining intraoperative femoral component rotation in total knee arthroplasty. The anterior femoral cortical line (AFCL) is an anatomical landmark which has been used by the senior author for 20 years to assess femoral rotation in over 4000 TKRs. The AFCL describes the alignment of the anterior cortex of the distal femur proximal to the trochlear articular cartilage. Methods: The AFCL was compared with the surgical epicondylar axis (SEA), anteroposterior axis (Whiteside’s line) and posterior condylar (PC) axis using 50 dry-bone cadaveric femora, 16 wet cadaveric specimens, 50 axial MRI scans and 58 TKR patients intra-operatively. Results: In the dry-bone and cadaveric femora (measuring relative to the SEA) the AFCL and Whiteside’s AP axis were 1° externally rotated and the PC axis was 1° internally rotated. With MRI (relative to the SEA) the AFCL was 8° internally rotated, Whiteside’s was 2° externally rotated and the PC axis was 3° internally rotated. In the clinical study (measuring relative to a perpendicular to Whiteside’s line alone) the AFCL was 4° degrees internally rotated, which equates to 2–3° of internal rotation relative to the SEA. Conclusion: The AFCL is another axis, completing the ‘compass points’ around the knee. It may prove particularly useful when one or all of the other reference axes are disturbed such as in revision TKR, lateral condylar hypoplasia or where there has been previous epicondylar trauma. We suggest building in 5° external rotation with respect to the anterior femoral cortical line when judging femoral component rotation

Purpose:. Accepted landmarks for determining femoral component rotation in total knee arthroplasty (TKA) include the posterior condyles, Whiteside’s line, arbitrary three to four degrees of external rotation, and transepicondylar axis (TEA). All methods require anatomical identification, which may be variable. The purpose of this study was to radiologically evaluate femoral component rotation (CT analysis) based on a method that references to the tibial shaft axis and balanced flexion tension without identification of femoral anatomical landmarks. Methods:. Out of a cohort of 3058 mobile bearing low contact stress TKA, CT scans of 38 randomly selected well functioning TKA were evaluated to determine femoral component positioning. Spiral CT scans of the femoral epicondylar region with four mm cuts were performed to accurately identify medial and lateral femoral epicondyles. Rotational alignment was measured in relation to the transepicondylar axis using CT-implemented software by two independent radiologists. Results:. Mean femoral rotational alignment was parallel to the TEA (average 0. 3 degrees internal rotation) ranging from six degrees internal to four degrees external rotation. All thirty-eight cases had satisfactory clinical results, range of motion of over 90°, and showed perfect patello-femoral tracking and patellar congruency on axial views. Conclusions:. Femoral rotation position based on tibial shaft axis and balanced flexion tension gap is patient specific, reproducible and results in predictable femoral rotational positioning and patella tracking. CT analysis in this study confirms that the tibial shaft axis method produces a consistent femoral component positioning that relates accurately to the TEA. Tibial shaft axis method avoids the need for arbitrary landmark identification, placing the femoral component predictably in an optimum position in relation to the tibia and patella. Address for correspondence: 
 . jgboldt@hotmail.com

Purpose:. Accepted landmarks for determining femoral component rotation in total knee arthroplasty (TKA) include the posterior condyles, Whiteside’s line, arbitrary three to four degrees of external rotation, and transepicondylar axis (TEA). All methods require anatomical identification, which may be variable. The purpose of this study was to radiologically evaluate femoral component rotation (CT analysis) based on a method that references to the tibial shaft axis and balanced flexion tension without identification of femoral anatomical landmarks. Methods:. Out of a cohort of 3058 mobile bearing low contact stress TKA, CT scans of 38 randomly selected well functioning TKA were evaluated to determine femoral component positioning. Spiral CT scans of the femoral epicondylar region with four mm cuts were performed to accurately identify medial and lateral femoral epicondyles. Rotational alignment was measured in relation to the transepicondylar axis using CT-implemented software by two independent radiologists. Results:. Mean femoral rotational alignment was parallel to the TEA (average 0. 3 degrees internal rotation) ranging from six degrees internal to four degrees external rotation. All thirty-eight cases had satisfactory clinical results, range of motion of over 90°, and showed perfect patello-femoral tracking and patellar congruency on axial views. Conclusions:. Femoral rotation position based on tibial shaft axis and balanced flexion tension gap is patient specific, reproducible and results in predictable femoral rotational positioning and patella tracking. CT analysis in this study confirms that the tibial shaft axis method produces a consistent femoral component positioning that relates accurately to the TEA. Tibial shaft axis method avoids the need for arbitrary landmark identification, placing the femoral component predictably in an optimum position in relation to the tibia and patella. Address for correspondence: 
 . jgboldt@hotmail.com

Achieving the correct amount of femoral component rotation has become the basic objective of surgical techniques in total knee arthroplasty and this can be done either with a measured resection technique or indirectly by flexion/extension gap equalization technique. We demonstrated the variabilities of the reference axes (PCA, WSL, TEA) when soft tissue tension was managed intraoperatively by navigation system. The mean angle of transepicondylar line, Whiteside’s line, posterior condylar line from the proximal tibia resection plane were 1.29 ± 3.67 (mean ± SD; range 7 to 10.5), 3.90 ± 4.17 (mean ± SD; range 3 to 15.5), −4.03 ± 2.71 (mean ± SD; range 9.5 to 1.0) respectively. Coefficient of variation(CV(%); std/mean × 100) were 283, 106, 67 respectively. Out of the 3 reference axes widely used for femoral component rotation, angles from proximal tibia resection plane to posterior condylar line showed the least range of variance

Background. Adequate rotation of femoral component in total knee arthroplasty(TKR) is mandatory for preventing numerous adverse sequelae. The transepicondylar axis has been a well-accepted reference for femoral component rotation in the measured resection technique. In this technique, measured resection is performed referenced off the tibial cut - perpendicular to the tibial mechanical axis with the knee in 90 ° of flexion. However, to the best of our knowledge, it is not known whether this technique apply well to a knee with tibia vara. This study evaluates the reliability of the transepicondylar axis as a rotational landmark in knees with tibia vara. Methods. We selected 101 osteoarthritis knees in 84 symptomatic patients(mean age: 69.24 ± 5.68) with proximal tibia vara (Group A). Group A was compared with 150 osteoarthritic knees without tibia vara in 122 symptomatic patients (mean age: 69.51 ± 6.01) (Group B). The guide line for selection of all these knees were based on the degree of tibia vara angle (TVA) which was formed by line perpendicular to epiphysis and by anatomical axis of the tibia - all measured in radiographs of the entire lower limb. Magnetic resonance imaging (MRI) axial images with most prominent part of both femoral condyles were used for measurement of transepicondylar axis(TE), anteroposterior axis(AP) and posterior condylar axis(PC). Results. The mean TVA of group A was 8.94° ± 3.11 and group B was 1.24° ± 0.85. The TE line in Group A showed 6.09 ° ± 1.43 of external rotation, relative to PC. This did not show statistical difference compared with 5.95 ° ± 1.58 in Group B (p=0.4717). The AP line in Group A showed 6.06 ° ± 1.93 of external rotation, relative to the line perpendicular to PC. This was statistically significant when compared to 5.44 ° ± 2.13 in Group B (p=0.020). Conclusion. There is no difference between knees without tibia vara compared those with tibia vara with regards to transepicondylar axis. In addition, both groups have almost identical external rotation of approximately 6 °. The AP axis was only approximately 0.5 ° difference between the two groups. The distal femoral geometry was not affected by tibia vara deformity, that is, there were no hypoplastic or hyperplastic deformities of medial femoral condyle in osteoarthritic knees with tibia vara. The use of transepicondylar axes in determining femoral rotation may produce flexion asymmetry in knees with proximal tibia vara. So, It should be pointed out that more attention should be paid on femoral component rotation and flexion gap balancing in knees with proximal tibial vara

The anterior femoral cortical line (AFCL) is an anatomical landmark which has been used by the senior author for 20 years to assess femoral rotation in over 4000 TKR's. The AFCL describes the alignment of the anterior cortex of the distal femur proximal to the trochlear articular cartilage. The AFCL was compared with the surgical epicondylar (SEA), anteroposterior (Whiteside's line) and posterior condylar (PC) axes using 50 dry-bone cadaveric femora, 16 wet cadaveric specimens, 50 axial MRI's and 58 TKR patients intra-operatively. In the dry-bone/cadaveric femora (measuring relative to the SEA the AFCL and Whiteside's AP axis were 1° externally rotated and the PC axis was 1° internally rotated. By MRI (relative to the SEA) the AFCL was 8° internally rotated, Whiteside's was 2° externally rotated and the PC axis was 3° internally rotated. In the clinical study (measuring relative to a perpendicular to Whiteside's line alone) the AFCL was 4° degrees internally rotated, which equates to 2-3° of internal rotation relative to the SEA. The AFCL is another axis, completing the ‘compass points’ around the knee. It may prove particularly useful when one or all of the other reference axes are disturbed such as in revision TKR, lateral condylar hypoplasia or where there has been previous epicondylar trauma. We suggest building in 5° external rotation with respect to the anterior femoral cortical line for femoral component rotation

Purpose of study The purpose of this study was to present the anterior femoral cortical line (AFCL) as a new anatomical landmark to aid the assessment of intra-operative femoral component rotation. The AFCL was compared with an established axis (the anteroposterior (AP) axis or Whiteside’s line) in both a cadaveric and clinical study. Methods Two points indicating the AP axis were identified and marked on 50 normal cadaveric femora. The AFCL was identified and marked with a rigid wire secured on the surface and the distal femur was photographed. A perpendicular to the AP axis was drawn on each image and the angle between this line and the AFCL was measured. 68 consecutive patients undergoing total knee arthroplasty for osteoarthritis of the knee were included in the clinical part of the study. After a routine exposure the AP axis was marked on each distal femur. The AFCL was identified and the anterior cortical cut was made parallel to this line. The angle between this cortical cut and the perpendicular to the AP axis was measured with a sterile goniometer. Results In the cadaveric study the AFCL was a mean 7.0 degrees internally rotated to the AP axis (SD = 5.1 degrees). In the clinical study in 8 patients it was impossible to draw the AP axis because of dysplasia or destruction of the trochlea by osteoarthrosis. In the remainder the mean difference between the anterior femoral cortical line and the AP axis was 1.5 degrees internally rotated (SD = 1.9 degrees) . Conclusion The anterior femoral cortical line has been shown in this study to be a useful clinical axis for assessing rotation of the femoral component and is without some of the disadvantages associated with other landmarks

Background: The purpose of this study was to assess the anterior femoral cortical line (AFCL) as an additional anatomical landmark for determining intraoperative femoral component rotation in total knee arthroplasty. The AFCL was compared with the Epicondylar axis, the anteroposterior (AP) axis (Whiteside’s line), and the posterior condylar axis. Dry bone, cadaver, MRI and intra-operative measurements were compared. Methods: Fifty dry bone femora, and 16 wet cadaveric specimens were assessed to identify the AFCL and this was compared against the 3 reference axes discussed above. Photographs were taken of the specimens with K-wires/marker pins secured to the reference axes and then a digital on-screen goniometer was used to determine the mean angular variations with respect to the Epipcondylar axis. In the clinical trial, 58 consecutive patients undergoing total knee arthroplasty were included. After a routine exposure the AP axis was marked on each distal femur. The AFCL was then identified and the anterior femoral cortical cut was made parallel to this line. The angle between this cortical cut and the perpendicular to the AP axis was measured using a sterile goniometer. In the MRI study, 50 axial knee images were assessed and the most appropriate slice/s determined in order to identify the AFCL and the other 3 reference axes and then their relationship was measured by an on-screen goniometer. Results: In the cadaveric study the AFCL was a mean 1° externally rotated to the epicondylar axis (SD = 5°), White-side’s line was 1° externally rotated (SD = 4°) and the posterior condylar axis was 1° internally rotated (SD = 2°). By MRI and with respect to the epicondylar axis, the AFCL was a mean 5° externally rotated (SD= 3), White-side’s Line was 1° externally rotated (SD = 2) and the posterior condylar axis was 3° internally rotated (SD = 2). In the clinical study in 8 patients it was impossible to draw the AP axis because of dysplasia or destruction of the trochlea by osteoarthrosis. In the remainder the mean difference between the anterior femoral cortical line and Whiteside’s AP axis was 4.1 degrees internally rotated (SD = 3.8°). The lateral release rate for this cohort was 4%. Conclusion: The anterior femoral cortical line provides an additional reference point, completing the ‘compass points’ around the knee. It has been shown in this study to be reliable in the laboratory, on MRI and in a clinical setting for assessing rotation of the femoral component. It may prove particularly useful when one or all of the other reference axes are disturbed such as in revision TKR, lateral condylar hypoplasia or where there has been previous epicondylar trauma