Akagi's Line Research Articles

The Posterolateral Corner-Locked Technique Is Applicable in a Chinese Population Regarding the Tibial Component Rotation Alignment in Total Knee Arthroplasty.

Rotational malalignment between the femoral and tibial components in total knee arthroplasty (TKA) can affect clinical outcomes, but there is no consensus on how to best determine tibia tray orientation. The posterolateral corner-locked (PLCL) technique may be a new method. This study aims to assess the applicability of this technique in a Chinese population. Forty normal Chinese volunteers were recruited and underwent computed tomography (CT) of the lower limbs. Knee model reconstructions and simulated standard tibial osteotomy were conducted digitally. The transepicondylar axis (TEA), the Akagi line, and the line connecting the medial third of the tibial tubercle with the midpoint of the posterior cruciate ligament (PCL) were projected to the tibial cross-section and marked. The PLCL technique was applied using either symmetrical or asymmetrical tibial tray templates, and the anteroposterior (AP) axis of the tibial tray was marked. The angles between the TEA and these lines were calculated, and the statistical differences were analyzed. The angle between the TEA and the Akagi line and between the TEA and the line connecting the medial third of the tibial tubercle with the midpoint of the PCL were 96.90 ± 5.57 and 107.31 ± 5.95 degrees, respectively. The angles between the TEA and the AP axis of the symmetrical and the asymmetrical design tibial trays were 94.01 ± 4.21 and 96.65 ± 4.70 degrees, respectively. Except for the Akagi line and AP axis of the asymmetrical tibial tray, statistical differences were found between all lines (p < 0.05). The PLCL technique is principally suitable for Chinese patients requiring TKA when using the tibial component referred to in this study, although it may result in slight external rotation.

The original Akagi line is the most reliable: a systematic review of landmarks for rotational alignment of the tibial component in TKA.

There is no present consensus on the most reliable anatomical landmarks or axes for tibial rotational alignment in total knee arthroplasty (TKA). The goal was therefore to review the literature and compare accuracy and repeatability of different axes for tibial baseplate rotation in TKA. Medline and Embase were searched for articles that reported accuracy in terms of error or discrepancy from the trans-epicondylar axes (TEA), and/or repeatability in terms of intraclass correlation coefficient, of one or more axes used for tibial baseplate rotation in TKA. Twenty-one articles met criteria, and their data were extracted and tabulated. The selected articles evaluated 15 different axes, 13 for reliability, 12 for repeatability. The lowest errors or discrepancies from the projected TEA were reported for the original 'Akagi line' (posterior cruciate ligament posteriorly to medial border of tibial tuberosity), its variant using the sulcus of the tibial spines as anterior landmark, as well as the anterior tibial border and the curve-on-curve technique. The best inter-observer repeatabilities were reported for 'Akagi line' variants that use the geometric centre of the tibial plateau posteriorly and the medial border of the tibial tuberosity, or the medial sixth of the patellar tendon anteriorly. Considering accuracy and repeatability simultaneously, only two axes were found to satisfy both criteria consistently: the original 'Akagi line' and the anterior tibial border. Because of the small number of studies found, the collected evidence remains insufficient to recommend reference axes for intra-operative rotational alignment of the tibial baseplate in TKA. A combination of two or more anatomical landmarks or projected axes could be used to ensure adequate tibial baseplate rotation, while considering individual patient morphology and implant design to optimize knee kinematics and prevent prosthetic overhang. Level IV, systematic review of level III and IV studies.

Bony landmarks with tibial cutting surface are useful to avoid rotational mismatch in total knee arthroplasty.

The purpose of this study was to define various anteroposterior axes of the tibial component as references and to evaluate their accuracy and variability using virtual surgery. It was hypothesized that (1) Akagi's Line could result in high accuracy and low variability in varus osteoarthritic knees; (2) anteroposterior axes defined by using the tibial bony cutting surface as a landmark might be good substitutes for Akagi's Line; and (3) extra-articular bony landmarks might influence the variability of the anteroposterior axis. Three-dimensional bone models were reconstructed from the preoperative computed tomography data of 111 osteoarthritic knees with varus deformities. Seven different anteroposterior axes of the tibial component were defined: Akagi's Line, Axis MED, Axis 1/6MED, Axis 1/3MED, Axis of Oval Shape, Axis of Anterior Crest, and Axis Second Metatarsus. The rotational mismatch angle was measured between the tibial anteroposterior axis and the line perpendicular to the transepicondylar axis projected on the cutting surface (positive value: external rotation of the tibial anteroposterior axis). The average rotational mismatch angles (referring to the projected anatomical/surgical epicondylar axes) were - 2.7° ± 5.8°/1.0° ± 6.0° (Akagi's Line), - 4.2° ± 7.7°/- 0.5° ± 7.8°, 2.9° ± 7.2°/6.6° ± 7.2°, 9.8° ± 7.0°/13.5° ± 6.8° (Axis MED, Axis 1/6MED, Axis 1/3MED), - 5.1° ± 7.9°/- 1.4° ± 7.8° (Axis of Oval Shape), and 19.3 ± 9.5°/23.0° ± 9.6°, - 2.0° ± 11.3°/1.7° ± 11.4° (Axis Anterior Crest, Axis Second Metatarsus), respectively. Akagi's Line provided the best accuracy and least variability in varus osteoarthritic knees. Axis 1/6MED and Axis MED are good substitutes for Akagi's Line due to the difficulty of identifying the attachment site of the posterior cruciate ligament after the proximal tibia has been cut. Extra-articular bony landmarks should not be used for alignment due to their high variability. This study will aid surgeons in choosing the proper anteroposterior axis of the tibial component to reduce rotational mismatch and thus achieve good clinical knee outcomes. III.

Reliability evaluation of inter-eminence line, Akagi and Dalury lines for intraoperative tibial rotation: An osteology-based study

BackgroundThis large osteology study examined the reliability, reproducibility and correlation between previously described tibial tray rotation alignment lines (including Akagi and Dalury lines). In addition, it described a novel inter-eminence line utilising the tibial plateau inter-condylar eminences as a landmark. MethodsA total of 214 post-medieval (18–19th centuries) skeletal tibia were examined. The inter/intra-observer variation and correlation between reference lines were measured. ResultsInter-observer reproducibility was excellent and there were no differences between Akagi, Dalury, and inter-eminence lines. Similarly, intra-observer reliability was excellent for Akagi, Dalury, and inter-eminence lines. Qualitative review of tibial inter-condylar eminences suggested that these could be easily identifiable. When taking the medial angle from a medial–lateral reference line, the Akagi line showed a mean of 96.90° (±10.27), inter-eminence line 94.52° (±12.84), and Dalury line 88.06° (±11.75). The angle produced by the Dalury line was significantly different from both the Akagi and inter-eminence lines (P≤0.001). The Akagi line and inter-eminence line showed a strong correlation (r=0.74). The Dalury line showed a weaker correlation with both the Akagi line (r=0.69) and inter-eminence line (r=0.40). ConclusionThis study suggested that tibial rotation lines showed excellent intra/inter-observer reliability and reproducibility. The novel and easily drawn inter-eminence line showed strong correlation with the Akagi line and could be used for tibial tray rotational alignment in total knee arthroplasty.

Combined CT-based and image-free navigation systems in TKA reduces postoperative outliers of rotational alignment of the tibial component.

Rotational malpositioning of the tibial component can lead to poor functional outcome in TKA. Although various surgical techniques have been proposed, precise rotational placement of the tibial component was difficult to accomplish even with the use of a navigation system. The purpose of this study is to assess whether combined CT-based and image-free navigation systems replicate accurately the rotational alignment of tibial component that was preoperatively planned on CT, compared with the conventional method. We compared the number of outliers for rotational alignment of the tibial component using combined CT-based and image-free navigation systems (navigated group) with those of conventional method (conventional group). Seventy-two TKAs were performed between May 2012 and December 2014. In the navigated group, the anteroposterior axis was prepared using CT-based navigation system and the tibial component was positioned under control of the navigation. In the conventional group, the tibial component was placed with reference to the Akagi line that was determined visually. Fisher's exact probability test was performed to evaluate the results. There was a significant difference between the two groups with regard to the number of outliers: 3 outliers in the navigated group compared with 12 outliers in the conventional group (P < 0.01). We concluded that combined CT-based and image-free navigation systems decreased the number of rotational outliers of tibial component, and was helpful for the replication of the accurate rotational alignment of the tibial component that was preoperatively planned.

Tibial shaft anatomy differs between Caucasians and East Asian individuals.

The orientation and distance from the shaft of the femur and tibia to the articular surface centre is important for performing total knee arthroplasty (TKA) with cementless stems. It is important to understand anatomic differences between races to match the tibial and femoral shaft axis to the knee articular surface. Thus, the purpose of this study was to compare knee morphology between Caucasian and East Asian individuals to determine the optimal placement of tibial and femoral stems. A retrospective study was conducted on a matched cohort of 50 East Asians (21F, 29M) and 50 Caucasians (21F, 29M) by age and gender. CT scans were obtained in healthy volunteers using<2-mm slices. The distance from the proximal tibial diaphysis axis to the tibial plateau centre and the distance from the distal femoral diaphysis axis to the centre of distal femoral articular surface were measured separately. Tibial measurements were taken using Akagi's anteroposterior (AP) axis and the widest mediolateral (ML) diameter, and femoral measurements were based on Whiteside's line and the surgical epicondylar axis. The ML distance between the tibial shaft centre and Akagi's line was significantly higher for Asians (9.9±2.7mm, Caucasians 7.7±3.1mm, p<0.001). The distance between the femoral shaft centre and Whiteside's line was lower, although not significantly different (Asians 1.9±1.0mm, Caucasians 2.2±1.1mm, n.s.). However, there were no differences in the AP dimension for the femur or tibia comparing Asians to Caucasians in both tibial side (Asians 10.6±3.3mm vs. Caucasians 10.9±4.0mm) and femoral side (Asians 18.1±1.7mm vs. Caucasians 17.5±1.6mm). East Asian individuals have more offset in the ML dimension for the tibia. This finding is clinical relevant, as this dimensional difference should be taken into consideration when designing primary and revision TKA stemmed tibial implants for East Asian individuals. Case-control study, Level III.

The fibular head projection is of limited use as a radiographic landmark in preoperative planning of total knee arthroplasty.

The projection of the fibular head is recommended as a quality indicator of a correct radiographic projection. However, this landmark has yet to be sufficiently validated. The MRIs of 334 knee joints were included. On the MRIs, the distance between the FH and lateral tibial cortical bone was simulated in projections parallel to surgically relevant axes. Then, the Pearson correlation coefficient between the distance of the FH to the lateral tibial cortical bone and the projection plane causing this was determined. A projection of the knee joint perpendicular to Akagi's line projected the center of the fibular head on average 4.8±2.9mm laterally of the tibial cortical bone, parallel to the maximum mediolateral axis of the tibia 7.5±3.4mm, parallel to the posterior condylar axis 5.6±3.6mm and parallel to the surgical epicondylar axis 6.1±3.5mm laterally of the tibial cortical bone. An almost linear correlation was seen, with 1.9° tilting of the projection plane per mm change in distance between the fibular head and tibial cortical bone. At the same time, the interindividual scatter was over 60°. The rule of thumb for a partial overlap of the fibular head by the tibia in the case of a correct antero-posterior projection plane was also confirmed. However, a considerable interindividual variability of the position of the FH was found, which limits a conclusion regarding the quality of the radiographic projection on the basis of the position of the fibular head.

The relationship between the midpoints connecting the tibial attachments of the anterior and posterior cruciate ligaments and the transepicondylar axis: In vivo three-dimensional measurement in the Chinese population

BackgroundTo determine the relationship between the midpoints connecting the tibial attachments of the anterior and posterior cruciate ligament (ACL and PCL, APCL line) and the transepicondylar axis (TEA) in normal healthy Chinese, as well as the comparison with other rotational lines. MethodsLeft knees of 17 male and 15 female healthy Chinese volunteers were scanned by magnetic resonance imaging (MRI) and computer tomography (CT) respectively. 3D contours of each knee, the tibial attachments of ACL, PCL, the medial and lateral collateral ligaments were reconstructed separately from CT and MRI data. Using an iterative closest point algorithm, we superimposed them individually. The APCL line, the tibial posterior condylar line (PC line), the medial third of the tibial tubercle (1/3 line), the Akagi's line, and the midsulcus of the tibial spine (Midsulcus line), the clinical and surgical TEA (CTEA and STEA) were determined. The paired intersection angles of them were measured. ResultsThe mean angle CTEA with APCL line, Akagi's line, Midsulcus line, 1/3 line, and PC line, respectively, was 90.3°±2.9°, 95.0°±3.0°, 94.0°±3.9°, 102.4°±2.7°, and 87.1°±3.0°. The APCL–CTEA was significant different than other angles (p<0.001). The mean angle STEA to the above lines, respectively, was 94.8°±3.1°, 99.4°±3.1°, 98.5°±4.0°, 106.9°±2.9°, and 91.6°±3.2°. The PC line-STEA was significantly different than other angles (p<0.05). ConclusionsAPCL line was the closest perpendicular to the CTEA in normal Chinese subjects comparing with other rotational lines.

Tibial component rotation during the unicompartmental knee arthroplasty: is the anterior superior iliac spine an appropriate landmark?

No "ideal" landmark for tibial component rotation in medial unicompartmental knee arthroplasty (UKA) has been suggested by a biomechanical and clinical study. The aim of this study was to investigate whether the anterior superior iliac spine (ASIS) could provide a consistent rotational landmark of the tibial component during mobile-bearing medial UKA using computed tomography (CT). During sagittal tibial resection, we utilized the ASIS as a rotational landmark. In 47 knees that underwent postoperative CT scans after medial UKA, the tibial component position was assessed by drawing a line tangential to the lateral wall of the tibial component. Rotation of the tibial component was measured using two reference lines: a line perpendicular to the posterior cortical rim of the tibia (angle α) and Akagi's line (angle β). Instant bearing position and posterior cruciate ligament (PCL) fossa involvement were also evaluated. External rotation of the tibial component relative to each reference line was considered positive values. The mean α and β angles were 8.0°±6.1° (range -4.0 to 24.3) and 8.7°±4.8° (range 1.9-25.2), respectively. Fourteen knees (29.8%) showed PCL fossa involvement of the tibial resection margin. One bearing showed complete 180° rotation at 2weeks postoperatively. Due to the wide variation and inherent difficulty of identifying the ASIS during the operation, it is not recommended for guidance of sagittal tibial resection during medial UKA. In cases of inappropriate tibia component rotation, risk of PE bearing spinning and iatrogenic PCL injury should be reminded after medial UKA. IV.

Inaccurate rotational component position in image-free navigated unicompartmental knee arthroplasty

Background/ObjectiveThe success of unicompartmental knee arthroplasty (UKA) is highly dependent on the accuracy of component and leg alignment. Computer-assisted surgery is gaining popularity in total knee arthroplasty with numerous studies reporting improved accuracy and decreased variability in implant position and postoperative limb alignment compared with conventional techniques. However, literature evaluating the accuracy of computer-navigated UKA is limited. Therefore, this study aimed to investigate the accuracy of component positions in navigated UKA using a three-dimensional (3D) image-matching system. To the best of our knowledge, this study is the first to evaluate the accuracy of implant-placement position in UKA using 3D image-matching systems. MethodsTwenty-three knees in 22 patients (9 men, 13 women) underwent computer-assisted UKA performed by a senior surgeon from 2011 to 2013. All surgeries were performed with measured resection techniques using an image-free-navigation system. We recorded the coronal, sagittal, and rotational bone-resection angles towards the mechanical axis in the distal femur and proximal tibia using image-free navigation intraoperatively. The coronal, sagittal, and rotational alignments of the femoral and tibial components were also measured using the 3D image-matching system, and the accuracy of the navigated UKA was evaluated. The rotational alignment of the femur and tibia was defined as surgical epicondylar axis and Akagi's line, and a deviation over 3° from the AA was defined as an outlier. ResultsWe observed coronal outliers for the femoral component in four of the 23 patients, and for the tibial component in three of the 23 patients. We also observed sagittal outliers for the femoral component in five of 23 patients, and for the tibial component in three of the 23 patients. Twenty-two tibial components were placed in external rotation relative to the rotational reference line. ConclusionIn both coronal and sagittal alignments, there were a definite proportion of outliers. The ratio of outliers in rotational alignment was especially higher than that in coronal and sagittal alignments. In UKA, the identification of bony landmarks is difficult because of the small operation field. Therefore, careful surface mapping of particular bony landmarks is necessary, and it is not enough to use image-free navigation system in UKA.

Restoration of the anatomic position during a meniscal allograft transplantation using pre-existing landmarks.

Accurate sizing and positioning of a meniscal allograft is an important factor for successful outcomes of meniscal allograft transplantation. The objectives of this study were (1) to search a proper rotational landmark, (2) to determine the sagittal slope of meniscus, and, thus (3) to determine the meniscal positioning. A total of 121 consecutive patients who underwent magnetic resonance imaging in the 3months prior to the beginning of the study were selected. To assess the meniscal rotation, rotation 0° line of the meniscus was defined as a line connecting the center of the anterior and the posterior horn of the medial and lateral meniscus, respectively. At this level, four possible reference lines were compared: Akagi line, line perpendicular to the largest mediolateral dimension (LMLD), line between the medial border of the patellar tendon and the apex of the medial tibial spine (PTMS), and line between the lateral border of the patellar tendon and the apex of the lateral tibial spine. To assess the meniscal slope, the slope of the insertional area, meniscal and bony slopes at the mid-plateau area were compared. Akagi line was significantly different with a true meniscal rotation (line connecting between centers of the anterior and posterior horns) in both medial and lateral meniscus (p<0.01 and p<0.01). LMLD was significantly different in the lateral meniscus (p<0.01), however, no statistical difference was observed in the medial meniscus (n.s.). PTMS was not different in the medial meniscus (n.s.), however, it was different in the lateral meniscus (p<0.01). On the medial side, significant statistical difference was observed between insertional and bony slope (p<0.01) and between meniscal and bony slope (p<0.01). On the lateral side, comparison of three slopes showed significant statistical differences (p<0.01-p=0.03). Line between patellar tendon and tibial spine was a good reference line for a meniscal rotation in the medial meniscus. Among previously introduced reference lines, LMLD showed approximity with a true meniscal rotation. The slope between tibial insertion and mid-portion was significantly different in the lateral meniscus.

Clinical faceoff: Neutrally versus kinematically aligned TKA.

While the number of primary TKAs completed in the United States is expected to increase dramatically in the years to come, approximately 20% of patients undergoing primary TKA are dissatisfied with the procedure [5, 11]. As such, substantial healthcare resources have been devoted to the development and use of patient-specific instrumentation (PSI), computer navigation, robotics, and other tools that help achieve a neutrally aligned TKA in the coronal plane [1, 2, 14]. On the other hand, some investigators support a different approach: The concept of a kinematically aligned TKA [6, 8–10]. In general terms, a neutrally aligned TKA cuts the distal femur and proximal tibia 90° to the respective mechanical axes, while a kinematically aligned TKA incorporates 3° of varus into the tibia and an additional 3° of valgus into the femur. However, there remains considerable controversy in this area, in large measure because of a relative paucity of research comparing the approaches. As such, I have invited two internationally known experts to discuss these two approaches to obtaining a well-aligned TKA – the neutrally aligned and kinematically aligned techniques.

Reliability of Intra-articular Rotational Axes at Standard Tibial Resection Level and Effect of Resecting Distally.

We determine the most reliable tibial intra-articular axis for rotational alignment of the tibial component at the standard resection level and at a distal resection level. The angles between the surgical transepicondylar axis and posterior condylar line, perpendicular to Akagi line, tibial anterior condylar line (ACL), and tibial maximum mediolateral line were measured at the standard resection level and 5 mm distal to the standard resection level. All axes exhibited relatively large standard deviations and ranges at the standard and distal resection level. t-test showed that there was a statistically significant difference (p < 0.05) for all the axes between the two resection levels, while only ACL showed a statistically significant difference (p = 0.047) with the equality of variance F-test. Akagi line exhibited good interobserver and intraobserver reliabilities but must be used with caution. Intra-articular axes are not reliable for tibial component alignment.

Rotational Alignment Landmarks in Primary Total Knee Arthroplasty

ABSTRACT Purpose We hypothesized that the anterior tibial surface curvature is a more reliable landmark for correct tibial component rotational positioning in TKA respect to the ‘Akagi’ line and the medial third of the tibial tubercle. Methods Three independent investigators reviewed 124 knee MRI scans, identifying independently the femoral transepicondylar axis (TEA), the femoral posterior condylar axis (PCA), a line connecting the middle of the posterior cruciate ligament and the medial edge of the patellar tendon attachment (Akagi's line), the medial third of the tibial tubercle and the anterior tibial surface curvature. The most appropriate tibial baseplate tracing for the NexGen Total Knee System (Zimmer, Warsaw, USA) was superimposed matching the anterior tibial cortex with its anterior surface. At this point, the rotation of the tibial plate tracing was calculated in respect to the TEA, the medial third of the tibial tubercle line, the Akagi's line and the PCA. Customized software was created and used for analysis of the MRI datasets. Results: The investigators agreed on the localization of the Akagi's line in 64% of the cases within 3° and in 85% of the cases within 5° (minimum –16°, maximum –7°): this landmark might lead to internal rotation of the tibial component. The observers agreed on the localization of the medial third of the tibial tubercle in 29% of the cases within 3° and, in 70% of the cases, within 5° (minimum –4°, maximum +4°): this landmark might lead to external rotation of the tibial component. The investigators agreed on the localization of the anterior tibial surface curvature in 89% of the cases within 3° and in 99% of the cases within 5° (minimum –1°, maximum +4°): component alignment along the anterior cortex guaranteed full matching ±3° to the epicondylar axis in 75% of the knees. Conclusion Alignment of the tibial component, when based on the anterior tibial surface, was more reliable and easier identifiable than either the Akagi's line or the medial third of the tibial tubercle. Level of evidence Level 3 (Retrospective cohort study). Indelli PF, Baldini A, Manfredini L, Marcucci M. Rotational Alignment Landmarks in Primary Total Knee Arthroplasty. The Duke Orthop J 2014;4(1):8-12.

Accuracy of anatomical references used for rotational alignment of tibial component in total knee arthroplasty

This study aimed to research which was the most reliable of the four techniques based on local anatomic markers used to determine tibial component rotation in total knee arthroplasty, and whether the markers varied in knees with varus deformity. The study included 33 knees with a normal anatomic axis and 32 knees with a varus deformity and osteoarthritis. On the MR images, the femoral transepicondylar axis (TEA) was determined and transposed to the standard tibial resection level. At this level, four axes were drawn on the axial sections: tibial posterior condylar line (PC), tibial plateau anterior line (AC), a vertical line (AA) drawn to Akagi's line, and the maximal mediolateral distance (MMLD). The relationships of these lines and the transposed TEA were compared between two groups. In all the knees, the mean values of the PC, AA, and MMLD axes compared to TEA reference were 5.5° ± 5.7 (mean ± SD), 7° ± 3.2, and 6.7° ± 8.1 internal rotation, respectively, and the AC axis was 8.9° ± 6.7 external rotation. In the AC, AA, and MMLD axes, the change occured because of varus deformity was statistically meaningful. For all the observers, the axis with the least SD and the most accuracy was the AA axis. Of the four axes used to determine tibial component rotation, only the PC axis is not affected by varus deformity, and the least affected axis according to the observers was the AA axis, and thus the AA and PC axes can be used for guidance in determining the rotation of the tibial component. Prognostic studies-investigating natural history and evaluating the effect of a patient characteristic: High-quality prospective cohort study with >80% follow-up, and all patients enrolled at same time point in disease, Level I.

Evaluation of tibial rotational alignment in total knee arthroplasty: a cadaver study

Various techniques exist for establishing tibial rotational alignment during total knee arthroplasty (TKA). The purpose of this study is to establish the most precise and reproducible method to assess tibial component rotational alignment during TKA by comparing the flexion-extension technique (ROM) and the Posterior-lateral Corner Locked Technique (PLCL). Twenty posterior stabilized TKAs were performed on cadavers. The rotation angles of the tibial components obtained using the two techniques were evaluated. The tibial component rotation axis obtained using the ROM technique and the PLCL method averaged, respectively, 0.35 degrees (+ or - 4.2 degrees ) externally rotated and 0.34 degrees (+ or - 3 degrees ) internally rotated to the Akagi line. No significant differences between the two methods were found and a high correlation exists between the two techniques (Pearson's coefficient = 0.88). The ROM and PLCL techniques are both precise and reproducible methods to assess tibial component rotation during TKA. However, while the ROM technique is dependent on the correct positioning of the femoral component and the soft tissue balancing, the PCLC method is easier if a complete visualization of the posterior-lateral corner of the cut tibial plateau is achieved.

Rotational Position of Femoral and Tibial Components in TKA Using the Femoral Transepicondylar Axis

Proper femoral and tibial component rotational positioning in TKA is critical for outcomes. Several rotational landmarks are frequently used with different advantages and limitations. We wondered whether coronal axes in the tibia and femur based on the transepicondylar axis in the femur would correlate with anteroposterior deformity. We obtained computed tomography scans of 100 patients with arthritis before they underwent TKA. We measured the posterior condylar angle on the femoral side and the angle between Akagi's line and perpendicular to the projection of the femoral transepicondylar axis on the tibial side. On the femoral side, we found a linear relationship between the posterior condylar angle and coronal deformity with valgus knees having a larger angle than varus knees, ie, gradual external rotation increased with increased coronal deformity from varus to valgus. On the tibial side, the angle between Akagi's line and the perpendicular line to the femoral transepicondylar axis was on average approximately 0 degrees , but we observed substantial interindividual variability without any relationship to gender or deformity. A preoperative computed tomography scan was a useful, simple, and relatively inexpensive tool to identify relevant anatomy and to adjust rotational positioning. We do not, however, recommend routine use because on the femoral side, we found a relationship between rotational landmarks and coronal deformity.