Objective. The aim of this study was to evaluate the shape of patella relative to the femoral epicondylar axis and to find sex differences. Materials and methods. Computed tomography (CT) images of 100 knees with tibiofemoral osteoarthritis in 100 patients were prospectively collected. All patients were diagnosed as varus-type osteoarthritis with no destructive patellar deformity. Fifty patients were male and 50 female. The average male age was 70.8±14.6 (mean ± SD) years and the average female age was 73.3±6.7 years. Forty nine knees were right and 51 knees were left. The average height of males was 162.6±7.4 cm and that of females 149.6±5.7 cm. Males were significantly taller than females. The CT scan was performed with 2mm-interval slices in the vertical plane to the long axis of femoral shaft. Every CT image was examined to determine the maximum distance between the medial and lateral femoral epicondyle (inter-epicondylar distance, IED) along the epicondylar axis. The maximum patellar width and thickness were also measured at the image which had these maximum distances, while patellar cartilage thickness in anteroposterior diameter was not measured in this study. For evaluating the patellar size, each measured value was divided by IED and calculated each ratio. The ratio of patellar width to patellar thickness was also calculated. All parameters were compared between males and females. Statistical software Statview ver.5.0 (SAS Institute Inc.) was used for all analyses with significance being set at the 5% level. Results. Measured values are presented on Table 1. The average IED, patellar width and patellar thickness of males were all significantly larger than those of females. As shown in Table 2, by contrast, each ratio to IED was almost the same between the sexes and there were no significant differences. The ratio of patellar width to patellar thickness was 46.7±2.6% in males and 46.6±2.9% in females. Discussion. Although some studies have assessed the actual measurement values of patella, no prior study, to our knowledge, has morphologically evaluated the patella relative to the femur. This is the first study to investigate the configuration and location of patella relative to femoral epicondylar axis. Our results showed the configuration of patella relative to the femoral epicondylar axis was the same between sexes. The patellar width is approximately 56% and TGD is approximately 39% of IED. The most common complications after the surgery are related to patellofemoral problems. The ideal thickness of the resurfaced patella has not been clearly investigated. Patellar disabilities are associated with both decreased and increased patellar thickness— a thin patella could lead to anteroposterior patellar instability and a thick patella could increase the risk of stiffness of the knee and patellar subluxation. Therefore, it is desirable to restore the original patellar thickness during surgery. The results of current study showed that the ratio of patellar width to the patellar thickness was about 47%, which is useful to determine the thickness of patella during surgeries for severely damaged knees or revision surgeries

Introduction. The assumption that symmetric extension-flexion gaps improve the femoral condyle lift-off phenomenon and the patellofemoral joint congruity in total knee arthroplasty (TKA) is now widely accepted. Conventional understanding of knee kinematics suggests that the femoral component should be rotationally aligned parallel to the surgical epicondylar axis (SEA). On the other hand, the theory of the balanced gap technique suggests the knee be balanced in extension and flexion to achieve proper kinematics and stability of the knee without reference to fixed bony landmarks. The purpose of our study was to evaluate the relationship between rotation alignment of the femoral component and postoperative flexion gap balance, and the femoral rotational alignment in relation to the tibial mechanical axis in patients when implanted using a balanced gap technique. Materials and Methods. The subjects presented 53 consecutive osteoarthritic (OA) varus knees underwent primary Posterior-Stabilised (PS) -TKA (NexGen LPS-flex, Zimmer). All subjects completed written informed consent. The patient population was composed of 7 men and 35 women with a mean age of 72.5 ± 8.3 years. The average height, weight, BMI, weight-bearing FTA, and the patella height (Insall-Salvati ratio: T/P ratio) were 151.7 ± 7.7 cm, 62.6 ± 11.8 kg, 27.2 ± 4.5, 184.9 ± 5.9° and 0.93 ± 0.14 respectively. All procedures were performed through a medial parapatellar approach and a balanced gap technique used a newly developed versatile tensor device which can measure the medial and lateral gaps individually and make use of the balanced gap technique guide with patellofemoral joint reduction, which had been introduced in 56. th. ORS 2010. Pre- and post-operatively, a condylar twist angle (CTA) was evaluated using computed tomography (CT). To assess the postoperative flexion gap balance, a condylar lift-off angle (LOA) was evaluated using the epicondylar view radiographs by adding a 1.5 kg weight at the ankle. Coronal alignment of the tibial component in reference to the tibial mechanical axis (angle θ) was evaluated using plain AP radiography. Data were expressed as mean ± SD and analysed with Stat View version 5.0. Results. Extension gap was well balanced within 3 mm in all cases. The average of the preoperative CTA, the postoperative CTA, the LOA and the angle θ. were 6.0 ± 1.5°, 1.2 ± 2.4°, 0.8 ± 1.4° and 89.7 ± 1.2° respectively. No significant correlation was observed in between the postoperative CTA, the LOA and the angle θ. The degree of the clinical epicondylar axis (CEA) to the tibial machanical axis was 90.1 ± 2.9°. Only one knee needed lateral retinaculum release, because of poor patella tracking evaluated by no thumb test or one stitch method. Discussion. This study demonstrated that our balanced gap technique, using a newly developed tensor device, achieved good patellofemoral joint congruity and balanced flexion gaps postoperatively. Rotation alignment of the femoral component was slight internal rotation in reference to the CEA but not parallel to the SEA. Conclusion. The CEA was perpendicular to the tibial mechanical axis in PS-TKA with well balanced extension-flexion gap achieved by a balanced gap technique

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

The anterior curve of the tibial plateau cortex represents a realiable and reproducible landmark which may help aligning the tibial component with the femoral component and the extensor mechanism. Few studies analyzed the tibial component rotational alignment during total knee arthroplasty. Malrotation can affect both patello-femoral and tibio-femoral postoperative function. We evaluated the rotational relationship between femur and tibia, and we investigated which tibial landmark consistently matches the rotation of the femoral epicondylar axis in full extension (Fig 1). Axial magnetic resonance images of 124 normal knees (statistical power 1-beta=0.8) were analyzed separately by three authors. Scanograms were obtained with the knee in full extension and with the long axis of the foot (second metatarsal bone) aligned on the neutral sagittal plane. The surgical epicondylar axis was drawn and projected over the proximal tibia and tibial tuberosity slices. Multiple anatomical tibial rotational landmarks were drawn and symmetric tibial component digital templates of different sizes were aligned according to each landmark. Alignment of the virtual tibial components was then compared to that of the projected femoral epicondylar axis (Fig 2). The best antero-posterior line to achieve rotational matching between the components was drawn on the proximal tibia slice of each patient. Results of rotation (positive = external rotation, negative = internal) relative to the epicondylar axis were (Fig 3): (a) Medial third-to the middle third of the tibial tubercle 1.2°+/−5.7, (b) Akagi's line (centre of the posterior cruciate ligament tibial insertion to the most medial part of the tibial tubercle) -11.5+/−6.5, (c) The anterior curved tibial plateau cortex (curve-on-curve matching between the tibial template and the anterior cortex) 1.0+/−2.9. Intraclass correlation coefficient resulted 0.923, 0,881, and 0.949 for the Akagi's line, Middle third of tibial tubercle, and the curve-on-curve reference respectively. The anterior curve of the tibial plateau cortex represents a realiable and reproducible landmark which may help aligning the tibial component with the femoral component and the extensor mechanism (Fig 4, 5)

INTRODUCTION. Mechanical alignment in TKA introduces significant anatomic modifications for many individuals, which may result in unequal medial-lateral or flexion-extension bone resections. The objective of this study was to calculate bone resection thicknesses and resulting gap sizes, simulating a measured resection mechanical alignment technique for TKA. METHODS. Measured resection mechanical alignment bone resections were simulated on 1000 consecutive lower limb CT-Scans from patients undergoing TKA. Bone resections were simulated to reproduce the following measured resection mechanical alignment surgical technique. The distal femoral and proximal tibial cuts were perpendicular to the mechanical axis, setting the resection depth at 8mm from the most distal femoral condyle and from the most proximal tibial plateau (Figure 1). If the resection of the contralateral side was <0mm, the resection level was increased such that the minimum resection was 0mm. An 8mm resection thickness was based on an implant size of 10mm (bone +2mm of cartilage). Femoral rotation was aligned with either the trans-epicondylar axis or with 3 degrees of external rotation to the posterior condyles. After simulation of the bone cuts, media-lateral gap difference and flexion-extension gaps difference were calculated. The gap sizes were calculated as the sum of the femoral and tibial bone resections, with a target bone resection of 16mm (+ cartilage corresponding to the implant thickness). RESULTS. For both the varus and valgus knees, the created gaps in the medial and lateral compartments were reduced in the vast majority of cases (<16mm). The insufficient lateral condyle resection distalises the lateral joint surface by a mean of 2.1mm for the varus and 4.4mm for the valgus knees. The insufficient medial tibial plateau resection proximalises the medial joint surface by 3.3mm for the varus and 1.2mm for the valgus knees. Medio-lateral gap imbalances in the extension space of more than 2mm) occurred in 25% of varus and 54% of valgus knees and significant imbalances of more than 5mm were present in up to 8% of varus and 19% of valgus knees. Higher medio-lateral gap imbalances in the flexion space were created with trans epicondylar axis versus 3 degrees to the posterior condyles (p<0.001). Using trans epicondylar axis, only 49% of varus and 18% of valgus knees had less than 3mm of imbalance in both media-lateral and flexion-extension gaps together. DISCUSSION AND CONCLUSION. A systematic use of the tested measured resection mechanical alignment technique for TKA leads to many cases with medio-lateral or flexion-extension gap asymmetries. Some medio-lateral imbalances may not be correctable surgically and may results in TKA instability. Other versions of the mechanical alignment technique or other alignment methods that better reproduce knee anatomies should be explored. For any figures or tables, please contact the authors directly

The cornerstone to proper ligament balancing in TKR is correct varus and valgus alignment in flexion and extension. For alignment in the extended position, fixed anatomic landmarks such as the intramedullary canal of the femur and long axis of the tibia are accepted. When the joint surface is resected at an angle of 5 degrees to 7 degrees valgus to the medullary canal of the femur and perpendicular to the long axis of the tibia, the joint surfaces are perpendicular to the mechanical axis of the lower extremity, and roughly parallel to the epicondylar axis. In the flexed position, anatomic landmarks are equally important for varus-valgus alignment. Incorrect varus-valgus alignment in flexion not only malaligns the long axes of the femur and tibia, but also incorrectly positions the patellar groove both in flexion and extension. Finding suitable landmarks for varus-valgus alignment has led to efforts to use the posterior femoral condyles, epicondylar axis, and anteroposterior (AP) axis of the femur. The posterior femoral condyles provide excellent rotational alignment landmarks if the femoral joint surface has not been worn or otherwise distorted by developmental abnormalities or the arthritic process. However, as with the distal surfaces, the posterior femoral condylar surfaces sometimes are damaged or hypoplastic (more commonly in the valgus than in the varus knee) and cannot serve as reliable anatomic guides for alignment. The epicondylar axis is anatomically inconsistent and in all cases other than revision total knee arthroplasty with severe bone loss, is unreliable for varus-valgus alignment in flexion just as it is in extension. The AP axis, defined by the lateral border of the posterior cruciate ligament posteriorly and the deepest part of the patellar groove anteriorly, is highly consistent, and always lies within the median sagittal plane that bisects the lower extremity, passing through the hip, knee, and ankle. When the articular surfaces are resected perpendicular to the AP axis, they are perpendicular to the AP plane, and the extremity can function normally in this plane throughout the arc of flexion

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

The cornerstone to correct ligament balancing is correct varus and valgus alignment in flexion and extension. For alignment in the extended position, fixed anatomic landmarks such as the intramedullary canal of the femur and long axis of the tibia are accepted. When the joint surface is resected at an angle of 5° to 7° valgus to the medullary canal of the femur and perpendicular to the long axis of the tibia, the joint surfaces are perpendicular to the mechanical axis of the lower extremity, and roughly parallel to the epicondylar axis. In the flexed position, anatomic landmarks are equally important for varus-valgus alignment. Incorrect varus-valgus alignment in flexion not only malaligns the long axes of the femur and tibia, but also incorrectly positions the patellar groove both in flexion and extension. Finding suitable landmarks for varus-valgus alignment has led to efforts to use the posterior femoral condyles, epicondylar axis, and anteroposterior (AP) axis of the femur. The posterior femoral condyles often are not reliable rotational alignment landmarks because the femoral joint surface has been worn or otherwise distorted by developmental abnormalities or the arthritic process. As with the distal surfaces, the posterior femoral condylar surfaces sometimes are damaged or hypoplastic (more commonly in the valgus than in the varus knee) and cannot serve as reliable anatomic guides for alignment. The epicondylar axis is anatomically inconsistent and in all cases other than revision total knee arthroplasty with severe bone loss, is unreliable for varus-valgus alignment in flexion just as it is in extension. The AP axis, defined by the centre of the intercondylar notch posteriorly and the deepest part of the patellar groove anteriorly, is highly consistent, and always lies within the median sagittal plane that bisects the lower extremity, passing through the hip, knee, and ankle. When the articular surfaces are resected perpendicular to the AP axis, they are perpendicular to the AP plane, and the extremity can function normally in this plane throughout the arc of flexion. Once the knee is set up in correct alignment, ligament balancing can be done with simple procedures based on basic anatomy. Anterior structures tighten in flexion, and posterior structures tighten in extension. Release of tight structures in a controlled fashion completes the aligned and balanced knee

Introduction. The Walch Type B2 glenoid has the hallmark features of posteroinferior glenoid erosion, retroversion, and posterior humeral head subluxation. Although our understanding of the pathoanatomy of bone loss and its evolution in Type B's has improved, the etiology remains unclear. Furthermore, the morphology of the humerus in Walch B types has not been studied. The purpose of this imaging based anthropometric study was to examine the humeral torsion in Walch Type B2 shoulders. We hypothesized that there would be a compensatory decrease in humeral retroversion in Walch B2 glenoids. Methods. Three-dimensional models of the full length humerus were generated from computed tomography data of normal cadaveric (n = 59) and Walch Type B shoulders (n = 59). An anatomical coordinate system referencing the medial and lateral epicondyles was created for each model. A simulated humeral head osteotomy plane was created and used to determine humeral version relative to the epicondylar axis and the head-neck angle. Measurements were repeated by two experienced fellowship-trained shoulder surgeons to determine inter-rater reliability. Glenoid parameters (version, inclination and 2D critical shoulder angle) and posterior humeral head subluxation were calculated in the Type B group to determine the pathologic glenohumeral relationship. Two-way ANOVAs compared group and sex within humeral version and head-neck angle, and intra-class correlation coefficients (ICCs) with a 2-way random effects model and absolute agreement were used for inter-rater reliability. Results. There were statistically significant differences in humeral version between normal and Type B shoulders (p < .001) and between males and females within the normal group (p = .043). Normal shoulders had a humeral retroversion of 36±12°, while the Walch Type B group had a humeral retroversion of 14±9° relative to the epicondylar axis. For head-neck angle, there were no significant differences between sexes (p = .854), or between normal and Type B shoulders when grouped by sex (p = .433). In the Type B group, the mean glenoid version was 22±7°, glenoid inclination was 8±6°, 2D critical shoulder angle was 30±5° and humeral head subluxation was 80±9%. Inter-rater reliability showed fair agreement between the two experienced observers for head-neck angle (ICC = .562; 95% CI: -.28 to .809) and excellent agreement for humeral version (ICC = .962;.913 to .983). Although only fair agreement was found between observers in head-neck angle ICC, the difference in mean angle was only 2°. Discussion. Although much time and effort has been spent understanding and managing Type B2 glenoids, little attention has been paid to investigating associated humeral contributions to the Type B shoulder. Our results indicate that the humeral retroversion in Type B shoulders is significantly lower than in normals. These findings have several implications, including, helping to understanding the etiology of the B2, the unknown effects of arbitrarily selecting higher version angles for the humeral component, and the unknown effects of altered version on glenohumeral joint stability, loading and implant survivorship post-arthroplasty. Our results also raise an important question, whether it is best to reconstruct Type B humeral component version to pathologic version or to non-pathologic population means

Correct rotational alignment of the femoral component is one of the most important elements in successful total knee arthroplasty. The surgical epicondylar axis is a well-known reliable landmark for a total knee arthorplasy. However, sometimes it is difficult for surgeon to define where a sulcus is, thus, hard to define a surgical epicondylar axis during a surgery. This Study evaluated the new reference of axis “Lateral Condylar Axis (LCA)” for the distal femur. The LCA is defined by the angle between the surgical epicondyalr axis and the Lateral Condylar Axis. To evaluate the consistency of this angle through ages, genders and femoral-tibia angle, this study also measured the angles between the surgical epicondylar and the anteroposterior asix and the surgical epicondylar and the posterior condaylar axis. By evaluating out the correlations and comparing the figure between measurements using the Student test, this study suggests that the Lateral Condylar Axis is a reliable landmark to properly rotate the femoral component and is easier to define during a surgery. The 59 knees out of 41 patients data was measured in 2011 – 2012

Introduction:. Conventional understanding of knee kinematics suggests that the femoral component should be rotationally aligned parallel to the surgical epicondylar axis (SEA). In contrast, the balanced gap technique suggests the knee be balanced in extension and flexion to achieve proper kinematics and stability of the knee without reference to fixed bony landmarks. To investigate the functional flexion-extension axis (FFEA) when a balanced gap technique was used in the posterior-stabilized total knee arthroplasty (PS-TKA), the relationships between rotational alignment of the femoral component to the postoperative flexion gap balance and to the tibial mechanical axis were evaluated radiographically. Materials and Methods:. In this prospective study, 63 consecutive knees in 50 patients were included with medial osteoarthritis undergoing a primary PS-TKA (NexGen LPS-Flex, fixed surface, Zimmer; Warsaw, USA). All subjects completed written informed consent. The patient population was composed of 8 men and 42 women with a mean age of 73.0 ± 7.7 years. The average height, weight, BMI, weight-bearing femorotibial mechanical angle (FTMA), condylar twist angle (CTA), and the patella height (T/P ratio) were 150.9 ± 7.2 cm, 62.3 ± 10.1 kg, 27.3 ± 4.0 kg/m. 2. , 167.8 ± 5.5°, 5.9 ± 1.6° and 0.94 ± 0.15, respectively. All procedures were performed through a medial parapatellar approach and a balanced gap technique used a newly developed versatile tensor device. Pre- and post-operatively, the CTA was evaluated using computed tomography (CT). To assess the postoperative flexion gap balance, a condylar lift-off angle (LOA) was evaluated using the epicondylar view radiographs. The FTMA and coronal alignment of the tibial component in reference to the tibial mechanical axis (angle β) were evaluated using plain AP radiography. The FFEA (angle θ) of the knee was calculated as the following; (angle β) + (post-operative CTA) – (LOA). Correlations were analyzed with Pearson's correlation coefficient. Predictive variables were analyzed utilizing Stepwise regression. A value of p < 0.05 was considered significant. Results:. Only two knees (3.2%) needed a lateral retinaculum release due to poor patella tracking. The average post-operative FTMA, angle β, LOA, and CTA were 178.7 ± 3.0°, 89.6 ± 1.3°, 0.7 ± 1.5°, and 1.3 ± 2.3°, respectively. The average angle θ was 90.2 ± 2.8°, significantly correlating with the post-operative CTA (r = 0.77), angle β (r = 0.42) and the LOA (r=–0.37). Moreover, the predictive variables of the angle θ was the following, 68.41 + 1.04 × (post-operative CTA) + 0.12 × (post-operative FTMA) – 0.93 × (LOA). (R. 2. = 0.805). Discussion:. This study demonstrated that the clinical epicondylar axis (CEA) was closely perpendicular to the tibial mechanical axis in PS-TKA with well balanced extension-flexion gap achieved by the balanced gap technique. This result also suggests the possibility of that the femoral component which is rotationally aligned parallel to the CEA would make the flexion balance better when an anatomical measured resection technique is used in a PS-TKA. Conclusion:. The functional flexion-extension axis in a PS-TKA with well balanced extension-flexion gap closely approximates the clinical epicondylar axis

Background. Total knee arthroplasty (TKA) is a cost-effective surgical procedure for degenerative knee disease and has good long-term results. However, these results are not always related to patient satisfaction and functional outcome. With an increasing demand of surgeons and patients on functioning of total knee implants, the need for adequate objective outcome measures is high. Imaging of the knee is commonly used in clinical practice and research to objectively measure many different outcome parameters concerning the implant, such as alignment and complications.1 However, techniques on comparison of the sagittal contour of the knee before and after implant placement are scarce. Goal. To develop and describe a standardized method for measuring the sagittal contour of the implant in a 3D model of the knee before and after implant placement. Methods. Images of the static knee of a subject are obtained in-vivo using fluoroscopy over a 180° sweep at 15 frames per second (MultiDiagnost Eleva, Philips, The Netherlands). A 3D model of the knee is constructed in accompanying software (3D-RX, Philips, The Netherlands) and is subsequently imported in OsiriX imaging software (Pixmeo, Switzerland). In Osirix, a reproducible coordinate system is obtained using the bone stub axis and the anatomical epicondylar axis as references [Fig. 1]. We quantified the sagittal contour of the distal femur in two parameters: the flexion angle of femoral component and the sagittal profile of the implant. To measure the flexion angle, the image is located in the midtrochlear plane. The angle is measured between the bone stub axis and the neutral line of the femoral component [Fig. 2]. To measure the sagittal profile of the distal femur, the lengths of three lines connecting the anatomical epicondylar axis of the distal femur and the outer border of the femur/prosthesis are summed. This is done both anterior and posterior [Fig. 3]. These profiles are measured in planes of the lateral and medial condyle and of the midtrochlear plane. Due to the reproducible coordinate system, the profiles can be compared for the knee before and after implant placement. Conclusion. Using fluoroscopy and readily available 3D imaging software we have developed a technique for measuring valuable parameters concerning implant placement in TKA. This technique can be used for scientific purposes concerning comparison of the knee before and after implant placement and to study its effect on functional and biomechanical outcome after TKA

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

Background. Humeral version is the twist angle of the humeral head relative to the distal humerus. Pre-operatively, it is most commonly measured referencing the transepicondylar axis, although various techniques are described in literature (Matsumura et al. 2014, Edelson 1999, Boileau et al., 2008). Accurate estimation of the version angle is important for humeral head osteotomy in preparation for shoulder arthroplasty, as deviations from native version can result in prosthesis malalignment. Most humeral head osteotomy guides instruct the surgeon to reference the ulnar axis with the elbow flexed at 90°. Average version values have been reported at 17.6° relative to the transepicondylar axis and 28.8° relative to the ulnar axis (Hernigou, Duparc, and Hernigou 2014), although it is highly variable and has been reported to range from 10° to 55° (Pearl and Volk 1999). These studies used 2D CT images; however, 2D has been shown to be unreliable for many glenohumeral measurements (Terrier 2015, Jacxsens 2015, Budge 2011). Three-dimensional (3D) modeling is now widely available and may improve the accuracy of version measurements. This study evaluated the effects of sex and measurement system on 3D version measurements made using the transepicondylar and ulnar axis methods, and additionally a flexion-extension axis commonly used in biomechanics. Methods. Computed tomography (CT) scans of 51 cadaveric shoulders (26 male, 25 female; 32 left) were converted to 3D models using medical imaging software. The ulna was reduced to 90° flexion to replicate the arm position during intra-operative version measurement. Geometry was extracted to determine landmarks and co-ordinate systems for the humeral long axis, epicondylar axis, flexion-extension axis (centered through the capitellum and trochlear groove), and ulnar long axis. An anatomic humeral head cut plane was placed at the head-neck junction of all shoulders by a fellowship trained shoulder surgeon. Retroversion was measured with custom Matlab code that analysed the humeral head cut plane relative to a reference system based on the long axis of the humerus and each elbow axis. Effects of measurement systems were analyzed using separate 1-way RM ANOVAs for males and females. Sex differences were analyzed using unpaired t-tests for each measurement system. Results. Changing the measurement reference significantly affected version (p<0.001). The ulnar axis method consistently resulted in higher measured version than either flexion-extension axis (males 9±1°, females 14±1°, p<0.001) or epicondylar axis (males 8±1°, females 12±1°, p<0.001). See Figure 1. Version in males (38±11°) was 7° greater than females (31±12°) when referencing the flexion-extension axis (p=0.048). Conclusion. Different measurement systems produce different values of version. This is important for humeral osteotomies; if version is assessed using the epicondyles pre-operatively and subsequently by the ulna intra-operatively, then the osteotomy will be approximately 10° over-retroverted. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

Introduction. Radiographs and computed tomography (CT) images are used for the preoperative planning in total knee arthroplasty (TKA), however, these two-dimensional (2D) measurements are affected easily by limb position and scanning direction relative to three-dimensional (3D) bone model analyses. The purpose of our study was to compare these measurements to evaluate the factors affecting the difference. Patients and Methods. A total of 75 osteoarthritis knees before primary TKA were assessed. The full-length weight-bearing anteroposterior radiograph and CT slices were used for the 2D measurement. Three-dimensional measurement used 3D bone model reconstructed from the CT data and the coordinate system as the previous reports (Figure 1). We measured FVA (femoral valgus angle), CRA (the angle between the posterior condylar line <PC-L> and the clinical epicondylar axis <CEA>), and SRA (the angle between the PC-L and the surgical epicondylar axis <SEA>). Intra- and inter-observer reliabilities were assessed by intraclass correlation coefficients (ICC), and the differences between the 2D and the 3D measurements (Differences) were evaluated. In addition, we evaluated whether preoperative factors (preoperative extension angle, HKA, BMI and CT scanning direction) affected the differences between the 3D and the 2D measurements. Computer simulation was used to examine the influences of CT scanning direction. Results. The ICC and the mean values with 2D and 3D measurements were shown in Table 1. The mean Differences were 0.2 ± 1.2° in FVA, 0.7 ± 2.1° in CRA and 0.7 ± 1.8° in SRA. Nine percentage in CRA and 13% in SRA had over 3 degrees of the Differences. There were no significant correlations between these factors and the Difference, however, the 3D simulation showed a significant difference of CRA between the scanning direction in varus/valgus and the neutral condition (varus: p<0.001, valgus: p<0.001) (Figure 2). Discussion. From our study, the 3D measurements were highly reliable. In the 2D measurements, the rotational measurements showed less interobserver reliability because of the difficulty of picking the same CT plane and the same position of femoral bony landmarks between observers. The mean Differences were small, however, the range was large and almost10% of our cases were over 3 degrees which can induce the malalignment of the component in spite of the precise bone cutting. Particularly, smaller values of the CRA and SRA with the 2D measurement have a risk of internal-rotated position of the femoral component. Preoperative osteoarthritis knees have flexion contractures, valgus, and femoral torsion. The 3D measurements are useful to avoid the different evaluation from the CT scanning situation

We proposed the substitute anteroposterior (sAP) line of the tibia for medial unicompartmental knee arthroplasty (UKA), which connects the medial border of the patellar tendon at the articular surface level and the medial intercondylar tubercle of the tibia. However, it has not been shown that referencing this line improves the rotational alignment of the components. Therefore, in this study, we investigated whether the tibial component could be implanted perpendicular to the SEA by referencing the sAP line and whether referencing the sAP line could reduce the rotational mismatch between the femoral and the tibial components. Postoperative computed tomography datasets from 60 lower limbs in 57 Japanese patients with medial UKA were used. Among these, 30 knees were operated using the sAP line for AP reference and other 30 knees using the medial intercondylar ridge (MIR) line. First, the angle between the AP orientation of the tibial component and the surgical epicondylar axis (SEA) was measured. Then, the rotational mismatch angle between the components was measured. The tibial and femoral components placed referencing the sAP line were externally rotated 90.7°±3.2° and 91°±7.7° relative to the SEA, respectively, those referencing the MIR line were 94.9°±8.5° and 91.2°±7.7°, respectively. When referencing the sAP line, the orientation of the component was more perpendicular to the SEA (Student t-test, unpaired, P = .016) and rotational variability of the tibial component was significantly smaller (F test, P < 0 .0001). The rotational mismatch angle when referencing the sAP line and the MIR line was 0.3°±8.3°and −3.8°±6.7°, respectively. Referencing the sAP line significantly reduced the rotational mismatch between the components (Student t-test, unpaired, P = .045). Referencing the sAP line in the medial UKA may be useful to determine the AP orientation of the tibial component

Surgeon-performed periarticular injection and anesthesiologist-performed femoral nerve or adductor canal block with local anesthetic have been used in multimodal pain management for total knee arthroplasty (TKA) patients. Anesthesiologist-performed adductor canal blocks are costly, time consuming, and may be unreliable. We investigated the feasibility of a surgeon-performed saphenous nerve (“adductor-canal”) block from within the knee joint. A retrospective analysis of 94 thigh-knee MRI studies was performed to determine the relationship between the width of the distal femur at the epicondylar axis and the proximal location of the saphenous nerve after its exit from the adductor canal and separation from the superficial femoral artery. After obtaining these data, TKA resections and trial component implantation were performed, using a medial parapatellar approach, in 11 fresh cadaveric lower extremity specimens. Using a blunt tip 1.5cm needle, we injected 10 ml each of two different colored solutions at two different intra-articular medial injection locations, and after 30 minutes, dissected the femoral and saphenous nerve and femoral artery from the hip to the knee to determine the location of the injections. Based upon the MRI analysis, the saphenous nerve was located (and had exited the adductor canal) at a mean of 1.5 times the epicondylar width in females, and mean 1.3 times the epicondylar width in males, proximal to the medial epicondyle. After placement of TKA trial components and injection, the proximal injection site solution bathed the saphenous nerve in 8 of 11 specimens. The proximal blunt needle and solution was adjacent, but did not puncture, the femoral artery and vein in only one specimen. This study suggests that a surgeon-performed injection of the saphenous nerve from within the knee is a feasible procedure. This technique may be a useful alternative to ultrasound guided block. A trial comparing surgeon and anesthesiologist-performed nerve block should be considered to determine the clinical efficacy of this procedure. Our anecdotal use of this intra-articular injection over the past year has been favorable. Newer, extended release anesthetic agents should be investigated with this technique

Purpose. Tibial and femoral component overhang in total knee arthroplasty (TKA) is a source of pain, thus is it important to understand anatomic differences between races to minimize overhang by matching the tibial and femoral shaft axis to the knee articular surface. Thus, this study compared knee morphology between Caucasian and East Asian individuals to determine the optimal placement of tibial and femoral stems. Methods. 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 <2mm slices. The distance from the proximal tibial diaphysis axis to the tibial plateau center was measured, and the distance from the distal femoral diaphysis axis to the center of distal femoral articular surface was measured. Tibial measurements were made using Akagi's AP axis and the widest ML diameter, and femoral measurements were based on Whiteside's line and the surgical epicondylar axis. Results. The ML distance between the tibial shaft center and Akagi line was significantly higher for Asians (9.9mm±2.7, Caucasians 7.7mm±3.1, p<0.001). The distance between the femoral shaft center and Whiteside line was lower, although not significantly different (Asians 1.9mm±1.0, Caucasians 2.2mm±1.1, p=0.11). However, there were no differences in the AP dimension for the femur or tibia comparing Asians to Caucasians. Conclusion. East Asian individuals have more offset in the ML dimension for the tibia. This should be taken into consideration when designing primary and revision TKA stemmed tibial implants for East Asian patients

Deformity correction is a fundamental goal in total knee arthroplasty. Severe valgus deformities often present the surgeon with a complex challenge. These deformities are associated with abnormal bone anatomy, ligament laxity and soft tissue contractures. Distorted bone anatomy is due to bone loss on the lateral femoral condyle, especially posteriorly. To a lesser extent bone loss occurs from the lateral tibia plateau. The AP axis (Whiteside's Line) or epicondylar axis must be used as a rotational landmark in the severely valgus knee. Gap balancing techniques can be helpful in the severely valgus knee, but good extension balance must be obtained before setting femoral rotation with this technique. Coronal alignment is generally corrected to neutral or 2- to 3-degree overcorrection to mild mechanical varus to unload the attenuated medial ligaments. The goal of soft tissue releases is to obtain rectangular flexion and extension gaps. Soft tissue releases involve the IT band, posterolateral corner/arcuate complex, posterior capsule, LCL, and popliteus tendon. Assessment of which structures is made and then releases are performed. In general, pie crust release of the IT band is sufficient for mild deformity. More severe deformities require release of the posterolateral corner / arcuate and posterior capsule. I prefer a pie crust technique, while Ranawat has described the use of electrocautery to perform these posterior/ posterolateral releases. In most cases the LCL is not released, however, this can be released from the lateral epicondyle, if necessary. Good ligament balance can be obtained in most cases, however, some cases with severe medial ligament attenuation require additional ligament constraint such as a constrained condylar implant

Deformity correction is a fundamental goal in total knee arthroplasty. Severe valgus deformities often present the surgeon with a complex challenge. These deformities are associated with abnormal bone anatomy, ligament laxity and soft tissue contractures. Distorted bone anatomy is due to bone loss on the lateral femoral condyle, especially posteriorly. To a lesser extent bone loss occurs from the lateral tibia plateau. The AP Axis (Whiteside's Line) or Epicondylar axis must be used as a rotational landmark in the severely valgus knee. Gap balancing techniques can be helpful in the severely valgus knee, but good extension balance must be obtained before setting femoral rotation with this technique. Coronal alignment is generally corrected to neutral or 2- to 3-degree overcorrection to mild mechanical varus to unload the attenuated medial ligaments. The goal of soft tissue releases is to obtain rectangular flexion and extension gaps. Soft tissue releases involve the IT band, Posterolateral Corner/Arcuate Complex, Posterior Capsule, LCL, and Popliteus Tendon. Assessment of which structures is made and then releases are performed. In general Pie Crust release of the ITB is sufficient for mild deformity. More severe deformities require release of the Posterolateral Corner/Arcuate Complex and Posterior Capsule. I prefer a pie crust technique, while Ranawat has described the use of electrocautery to perform these posterior/ posterolateral releases. In most cases the LCL is not released, however, this can be released from the lateral epicondyle, if necessary. Good ligament balance can be obtained in most cases, however, some cases with severe medial ligament attenuation require additional ligament constraint such as a constrained condylar implant