Introduction:. Appropriate transverse rotation of the tibial component is critical to achieving a balance of tibial coverage and proper tibio-femoral kinematics in total knee replacement (TKR), yet no consensus exists on the best anatomic references to determine rotation. Historically, surgeons have aligned the tibial component to the medial third of the tibial tubercle. 1. , but recent literature suggests this may externally rotate the tibial component relative to the femoral epicondylar axis (ECA) and that the medial border of the tubercle is more reliable. 2. Meanwhile, some TKR components are designed with asymmetry of the tibial tray assuming that maximizing component coverage of the resected tibia will result in proper alignment. The purpose of this study was to determine how different rotational landmarks and natural variation in osteoarthritic patient anatomy may affect asymmetry of the resected tibial plateau. Methods:. Pre-operative computed-tomography scans were collected from 14,791 TKR patients. The tibia and femur were segmented and anatomic landmarks identified: tibial mechanical axis, medial third and medial border of the tibial tubercle, PCL attachment site, and the surgical ECA of the femur. Virtual surgery was performed with an 8-mm resection (referencing the high side) made perpendicular to the tibial mechanical axis in the frontal plane, with 3° posterior slope, and transversely aligned with three different landmarks: the ECA, the medial border, and medial third of the tubercle. In each of these rotational alignments, the relative asymmetry of the medial and lateral plateaus was calculated (Medial AP/Lateral AP) (Fig. 1). Results:.
The “correct” rotational alignment and “normal” rotational alignment may not be the same position. Because of natural tibial plateau has average 3° varus but classical TKA method make tibial cut perpendicularly to tibial mechanical axis. Consequently femoral rotational compensation to 3° becomes necessary. While anatomical TKA method performed tibial cut in 3° varus. Then posterior femoral cut will be parallel to posterior condylar axis and component rotation theoretically should be aligned in natural anatomy. This study compares the rotational alignment between two methods. Study conducted on 80 navigated TKAs with modified gap technique. Intraoperative femoral rotation retrieved from navigation.
Introduction. Current pre-clinical testing is performed using knee wear simulators with standardized walking profiles. Differences in generated damage patterns to those observed on retrieved liners have been explained with the absence of activities other than walking, less severe loading conditions, and a discrepancy in the simulator's tibiofemoral contact mechanics and in vivo knee excursion. While it has been recognized that rotational alignment of the knee may also drive the location and shape of wear scars, to the best of our knowledge this parameter has not been investigated in knee simulator studies. Methods. Here, we use patient specific gait as input to the simulation to approximate the patient specific contact mechanics. Kinematic and kinetic input data was obtained from gait analysis of a patient with a MGII (Zimmer Inc.) prosthesis at 11 years post-op using the point cluster technique for tibiofemoral kinematics, and a mathematical model for internal force calculations. Using the identical type of prosthesis on the simulator, wear tests were conducted in displacement mode on a closed-loop controlled station. Because x-rays of the patient suggested an internal rotation of the tibial tray, it was varied form 0–10° and the effect on location and wear scar dimension was assessed. Results were compared with the retrieved liner (obtained after 13 years in vivo). Results. The simulator inputs generated from the gait data were compared with ISO 14243–3 (Figure 1). The first contact force peak of the patient was significantly lower, while second contact force peak similar to ISO. There were minimal differences in the flexion/extension profiles. For stance phase, the anterior/posterior translation and internal/external rotation kinematics did not show similar patterns, but they did fall within similar ranges from zero. There was little similarity for the swing phase. The total wear scar area of the retrieval was measured to be 919.8 mm. 2. The average total wear scar of the tested components was 853.0 ± 59.8 mm. 2. (p= 26.28%) The outcome values of the tested components compared to the retrieval are shown in Figure 2. All offsets produced a smaller wear scar than the retrieval, but the 7° offset produced the closest area which was within 1 mm. 2. of the retrieval. The 7° offset also had the closed centroid offset angle, which was within 0.2° of the retrieval (Figure 3). On the retrieval, a small wear scar was observed on the anterior- medial aspect of the intracondylar eminence (not shown). Among the tested components, the 7° and 10° offsets recreated damage at this location. Discussion.
Rotational or axial alignment is an important concept in total knee surgery. Malrotation of the femoral component can lead to patellofemoral maltracking, pain and stiffness. In reconstruction surgery of the knee, achievement of correct rotation is even more difficult because of the lack of anatomical landmarks. The linea aspera is often the only remaining landmark, but its reliability is questionable. Can custom-made 3D-guides help with rotational alignment of the knee after a wide resection of the distal femur?Introduction
Goal of research
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.
The purpose of this study is to investigate the relationship between the angles made by the reference axes on the computerized tomography (CT) images and comparison of the knee alignment between healthy young adults and patients who is scheduled to have total knee arthroplasty. This study was conducted in 102 patients with osteoarthritis of knee joint who underwent preoperative computerized tomography (CT). The control group included 50 patients having no arthritis who underwent CT of knee. Axial CT image of the distal femur were used to measure the angles among the the anteroposterior (AP) axis, the posterior condylar axis (PCA), clinical transepicondylar axis (cTEA) and the surgical transepicondylar axis (sTEA). Then, the differences in amounts of rotation between normal and osteoarthritic knee was evaluated.Purpose
Materials and Methods
To investigate the tibiofemoral rotational profiles during surgery in navigated posterior-stabilized (PS) total knee arthroplasty (TKA) and investigated the effect on postoperative maximum flexion angles. At first, twenty-five consecutive subjects (24 women and 1 man; age: mean, 77 years; range, 58–85 years) with varus osteoarthritis treated with navigated PS TKA (Triathlon, Stryker, Mahwah, NJ) were enrolled in this study. Kinematic parameters, including the tibiofemoral rotational angles from maximum extension to maximum flexion, were recorded thrice before and after PCL resections, and after implantation. The effect of PCL resection and component implantation on tibiofemoral rotational kinematics was statistically evaluated. Then, the effect of tibiofemoral rotational alignment changes on the postoperative maximum angles were retrospectively examined with 96 subjects (84 women, 12 men; average age, 76 years; age range, 56–88 years) who underwent primary TKA.Purpose
Materials and Methods
Rotational malalignment of the components in total knee arthroplasty has been linked to patellar maltracking, improper soft tissue balance, abnormal kinematics, premature wear of the polyethylene inlay, and subsequent clinical complications such as anterior knee pain (Barrack et al., 2001; Zihlmann et al., 2005; Lakstein at al., 2010). This study investigates an innovative image-based device that is designed to be used along with an intraoperative Isocentric (ISO-C) 3D imaging C-arm, and the conventional surgical instruments for positioning the femoral component at accurate rotational alignment angles. The new device was tested on 5 replica models of the femur (Sawbones). Zimmer NexGen total knee replacement instruments were used to prepare the bones. After making the distal transverse cut on the femurs, the trans-epicondylar-axis (TEA) were defined by a line connecting the medial and lateral epicondyles which were marked by holes on the bone models. The 4-in-1 cutting jig was placed and pinned to the bones with respect to the TEA considering 5 different planned rotational alignments: −10°, −5°, 0°, +5°, and +10° (minus sign indicating external and plus sign internal rotation). At this point, the jig was replaced by the alignment device using the head-less pins as the reference, and subsequently an Iso-c 3D image of the bone was acquired using Siemens ARCADIS Orbic C-arm. The image was automatically analyzed using custom software that determined the angle between the TEA and the reference pins (Fig 1). The difference between the angle read from the device and the planned angle was then used to correct the locations of the reference pins through a custom protractor device. Preparation of the bone was continued by placing the 4-in-1 jigs on the newly placed pins. Three-dimensional images of the bones after completion of the cuts were acquired, and the angle between the final cut surface and the TEA was determined.INTRODUCTION
METHODS
Rotational malalignment of the femoral component still causes patellofemoral complications that result in failures in total knee arthroplasty (TKA). To achieve correct rotational alignment, a couple of anatomical landmarks have been proposed. Theoretically, transepicondylar axis has been demonstrated as a reliable rotational reference line, however, intraoperative identification of the transepicondylar axis is challenging in some cases. Therefore, surgeons usually estimate the transepicondylar axis from posterior condylar axis (PCA) using twist angle determined by the preoperative X-rays and CT. While PCA is the most apparent landmark, radiographs are not able to detect posterior condylar cartilage. In most osteoarthritic knees, the cartilage thickness of the posterior condyle is different between medial and lateral condyles. The purpose of this study is to evaluate the effect of the posterior condylar cartilage on rotational alignment of the femoral component in large number of arthritic patients. Furthermore, we investigated whether the effect of posterior condylar cartilage is different between osteoarthritis (OA) and rheumatoid arthritis (RA). Ninety-nine OA knees and 36 RA knees were included. Detailed information is summarized in Table 1. All cases underwent TKA using navigation system. The institutional review board approved the study protocol and informed consent was obtained from each participants. To evaluate the effect of posterior condylar cartilage, we measured two different condylar twist angle (CTA) using navigation system and intraoperative fluoroscopy-based multi-planner reconstruction (MPR) images obtained by a mobile C-arm. To uniform the SEA in two different measuring systems, we temporary inserted a suture anchors in medial and lateral prominence. The CTA that does not include the posterior condylar cartilage (MPR CTA) is evaluated on MPR images and the CTA that does include the posterior condylar cartilage (Navi. CTA) is calculated by navigation system. The difference between these two angles corresponds to the effect of posterior condylar cartilage on the rotation of the femoral component (Fig. 1). The paired or unpaired t test was used to compare the obtained data. The statistics were performed using GraphPad Prism 6. A P value of 0.05 or less is considered as a significant difference.Objective
Methods
In total knee arthroplasty (TKA), rotational alignment of the femoral component is determined by the measured resection technique, in which anatomical landmarks serve as determinants, or by the gap balancing technique, in which the femoral component is positioned relative to the resected aspect of the tibia. The latter technique is considered logically more favorable for obtaining rectangular extension and flexion gaps. However, in patients with severe changes attributed to osteoarthritis and/or a severely limited range of motion, it is difficult to perform adequate posterior clearance (e.g. bone spur excision) before resecting the posterior femoral condyle, often causing unbalanced extension and flexion gaps after resection. Thus, the gap balancing technique is more technically demanding and requires higher skill. We employed a computed tomography (CT)-based navigation system to develop a simple and standardized surgical technique by performing two assessments: Assessment 1, we investigated the relationship between the position of the femoral component determined by the gap balancing technique and anatomical landmarks; and Assessment 2, we placed the femoral component at the position determined by the measured resection technique and within the acceptable gap-balanced range determined in Assessment 1. In Assessment 1, 18 knees with osteoarthritis were treated by posterior stabilized TKA for varus deformity. The extension-flexion balance after resection of the distal femoral condyle and the proximal tibia was within 3° in all cases. Posterior bone resection was performed parallel to the resected aspect of the tibia and at 90° of flexion under constant compression applied using a tensor. In other words, the rotational alignment of the femoral component was determined by the gap balancing technique, and its position relative to the posterior condylar axis (PCA) and clinical transepicondylar axis (CEA), which are landmarks in the measured resection technique, and the condylar twist angle (CTA; the angle between the CEA and PCA) were measured, and their relationships were quantitatively determined. The CTA, which was determined based on the preoperative CT data, was 4.7– 9.6° (mean, 7.05 ± 1.35°), while the aspect of the femoral resection was 3.0–8.3° externally rotated (mean, 5.6 ± 1.6°) to the PCA; a strong positive correlation was found between the rotational alignment of the femoral component and the CTA (p < 0.0001, R2 = 0.871). The aspect of the femoral resection was 0.3–2.6° internally rotated (mean, 1.4 ± 0.6°) to the CEA, and no correlation with the CTA was apparent. In Assessment 2, 39 knees with an extension-flexion balance ≤3° were examined to determine the internal-external rotation balance. Based on the results of Assessment 1, we employed the measured resection technique and placed the femoral component by rotationally aligning the target, which was 1.4° internally rotated to the CEA. The final rotational alignment of the femoral component was 2.0 ± 0.6° internally rotated to the CEA; the internal-external rotation balance at 90° of flexion was good and more toward external rotation by 0.72 ± 1.61°. The results demonstrated that the measured resection technique enables placement of the femoral component within an acceptable range of rotational alignment.
The purpose of this study was to determine the normal angle of rotation of the axis of each finger using digital image analysis, whether the rotation of the digits is symmetrical in the two hands of an individual, and the reliability of this method. Standardised digital photographic images were taken of thirty healthy volunteers. The palm of each hand was placed on a flat bench top with their fingers held in extension and adducted, to give an end-on image of all four fingers. Three independent observers analysed the images using Adobe Photoshop software. The rotational angle of each finger was defined as the angle created by a straight line connecting the radial and ulnar border of the nail plate and the bench top horizon. The three observers showed Inter-Rater Reliability of 92%. The mean angles of rotation were: Index 13°, Middle 10°, Ring 5°, Little 12°. The differences in angle of rotation of the index and middle finger between the left and right hand were statistically significant (p=0.003, and p=0.002 respectively), demonstrating asymmetry between the two sides. The differences in angle of rotation of the ring and little finger of the left and right hand were not significantly significant (p= 0.312 and p=0.716 respectively). In conclusion, symmetry was seen in the little and ring but not in the index and middle fingers. Digital image analysis provides a non-invasive and reproducible method of quantifying the rotation of normal fingers and may be of use as a diagnostic tool in the assessment and management of hand injuries.
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. 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.Introduction
Patients and methods
Rotational positioning of the femoral component during the realisation of a total knee arthroplasty is an important part of the surgical technique and remains a topic of discussion in the literature. The challenge of this positioning is important because it determines the anatomical result and its effect on the flexion gap and clinical outcome mainly through its impact on patellofemoral alignment. The intraoperative identification of the axis transepicondylar visually or by navigation is not reliable or reproducible. The empirical setting to 3 ° of external rotation, the procedure used to cut or dependent or independent is not adapted to the individual variability of knee surgery. Indeed, the angle formed by the posterior condylar axis and trans-epicondylar axis is subject to large individual variations. The authors propose a novel technique, using the navigation of the trochlea to determine the rotation of the femoral component. The principle is to consider the rotation of the femoral implant as “ideal” when it makes a perfect superposition of the prosthetic trochlea with the native bony trochlea on patellofemoral view at 60° when planning the femur. The bottom of the prosthetic trochlea is well aligned with the trochlea groove, identified during the trochlear morphing, itself perpendicular to the trans-epicondylar axis. The authors hope to encourage centering patellofemoral joint prosthesis, thus favoring the original kinematics of the extensor apparatus. The purpose of this study is to demonstrate firstly, that the navigation of the trochlea is a reliable and reproducible method to adjust the rotation of the femoral component relative to the trans-epicondylar axis taken as reference and the other, the rotation control by this method is not done at the expense of the balance gap in flexion. It is a bi-centric study prospective, nonrandomised, including continuously recruited 145 patients in two French centers. All patients were included in the year 2010 and have all been revised three months and one year of surgery. The average age of patients was 71 years [53, 88]. It was made no selection of patients who have all been included consecutively in the study and in the two centres. In all cases, the rotation of the femoral component was determined by intraoperative navigation of the trochlea. The authors compared the alpha angle (angular divergence between the plane and the posterior bicondylar plane and trans-epicondylar axis) obtained by this method and that calculated on a pre-or postoperative scan. The authors also measured the space between femur and tibia internal and external side in flexion (90°) to assess the impact on the balance in flexion. There is excellent agreement between the results obtained by the method of CT scan and the trochlear navigation technique. In addition, this technique allows us to achieve a quadrilateral space gap in flexion. The authors found large individual variation in the distal femoral epiphyseal torsion (angle alpha). They demonstrate that the navigation of the trochlea is a reliable and reproducible method to adjust the rotation of the femoral component relative to the trans-epicondylar axis taken as reference and provides, concomitantly, a quadrilateral space gap in flexion.
Rotational positioning of the femoral component during the realisation of a total knee arthroplasty is an important part of the surgical technique and remains a topic of discussion in the literature. The challenge of this positioning is important because it determines the anatomical result and its effect on the flexion gap and clinical outcome mainly through its impact on patellofemoral alignment. The intraoperative identification of the axis transepicondylar visually or by navigation is not reliable or reproducible. The empirical setting to 3 ° of external rotation, the procedure used to cut or dependent or independent is not adapted to the individual variability of knee surgery. Indeed, the angle formed by the posterior condylar axis and trans-epicondylar axis is subject to large individual variations. The authors propose a novel technique, using the navigation of the trochlea to determine the rotation of the femoral component. The principle is to consider the rotation of the femoral implant as “ideal” when it makes a perfect superposition of the prosthetic trochlea with the native bony trochlea on patellofemoral view at 60 ° when planning the femur. The bottom of the prosthetic trochlea is well aligned with the trochlea groove, identified during the trochlear morphing, itself perpendicular to the trans-epicondylar axis. The authors hope to encourage centering patellofemoral joint prosthesis, thus favouring the original kinematics of the extensor apparatus. The purpose of this study is to demonstrate firstly, that the navigation of the trochlea is a reliable and reproducible method to adjust the rotation of the femoral component relative to the trans-epicondylar axis taken as reference and the other, the rotation control by this method is not done at the expense of the balance gap in flexion. It is a bi-centric study prospective, nonrandomised, including continuously recruited 145 patients in two French centres. All patients were included in the year 2010 and have all been revised three months and one year of surgery. The average age of patients was 71 years [53, 88]. It was made no selection of patients who have all been included consecutively in the study and in the two centres. In all cases, the rotation of the femoral component was determined by intraoperative navigation of the trochlea. The authors compared the alpha angle (angular divergence between the plane and the posterior bicondylar plane and trans-epicondylar axis) obtained by this method and that calculated on a pre-or postoperative scan. The authors also measured the space between femur and tibia internal and external side in flexion (90°) to assess the impact on the balance in flexion. There is excellent agreement between the results obtained by the method of CT scan and the trochlear navigation technique. In addition, this technique allows to achieve a quadrilateral space gap in flexion. The authors found large individual variation in the distal femoral epiphyseal torsion (angle alpha). They demonstrate that the navigation of the trochlea is a reliable and reproducible method to adjust the rotation of the femoral component relative to the trans-epicondylar axis taken as reference and provides, concomitantly, a quadrilateral space gap in flexion.
Computer navigation has been shown to improve the accuracy of total knee replacement (TKR) when compared to intra or extra osseous referencing. Currently the surgical transepicondylar axis (TEA) is used to help determine femoral component rotation. This relies on the surgeon identifying medial and lateral epicondyles intra-operatively. This process has been shown to have a high variability and operator dependency. The functional flexion axis (FFA) of the femur is a kinematically derived reference axis which has previously been shown in a cadaveric model to correspond well with the transepicondylar axis. This study was therefore designed to evaluate its accuracy in vivo. 50 patients undergoing total knee replacement under the care of the three senior authors were prospectively recruited. A preoperative CT scan was obtained and the TEA evaluated by 2 independent clinicians. TKR was undertaken in the standard fashion using Stryker navigation. The FFA was derived at 3 time points during the procedure: pre-incision, post osseous registration and following component implantation. The deviations of the FFA and surgical TEA (surTEA) to the CT-derived TEA (ctTEA) was calculated and comparisons drawn between the 2 methods with respect to validity, as well as within and between-patient reproducibility. While the FFA results were highly correlated between pre and post-arthrotomy (r = 0.89), the post-incision FFA (−1.60+/−3.7) was significantly internally rotated (p<0.01) relative to the pre-incision FFA (−2.50+/−3.4). In addition the surgical TEA (−0.40+/−3.6) was significantly internally rotated (p = 0.02) relative to the post-incision FFA (1.80+/−3.7) for the combined data from all 2 surgeons. However, when examined individually, 1 of the 2 surgeons showed no significant difference between the FFA and TEA. In addition, the two methods demonstrated comparable between-patient variability in the knee axis, although surgeon-dependent patterns remained. The FFA has been shown to be of equivalent accuracy to the surgical TEA but surprisingly does not avoid its operator-dependency. Further evaluation of the FFA method with possible adjustments to the algorithm is warranted.
Malrotation of a femoral component is a cause of patellofemoral maltracking after total knee arthroplasty (TKA). We have developed a balanced gap technique in posterior stabilized total knee arthroplasty (PS-TKA) using an original tensor instrument. One of characteristics of this instrument is the ability to measure gaps even if there is a bone defect, because it has two paddles, and we can attach block augmentations. In addition it can measure the gap after a reduction of the patella with an offset mechanism. In the balanced gap technique, the femoral component rotation is decided by a tibial cut surface and ligaments balance using the tensor device. This study investigated retrospectively whether rotational alignment of femoral component rotation influenced patellofemoral joint congruency in PS- TKA. We evaluated the radiographs of 52 knees of 42 patients, who underwent TKA (NexGen LPS-Flex, fixed surface, Zimmer) by one surgeon (S.A.) for osteoarthritis or rheumatoid arthritis. All procedures were performed through a medial parapatellar approach and a balanced gap technique using a developed versatile tensor device. We measured lateral patella tilt and lateral patella shift at post-op. 6 months. To assess the rotational alignment of femoral component rotation, condylar twist angle (CTA) was measured, and to assess the postoperative flexion gap balance, a condylar lift-off angle (LOA) was measured using the epicondylar view radiographs.Introduction
Material and Methods
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. 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/m2, 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.Introduction:
Materials and Methods:
The relationships between the transepicondylar axis (TEA), Whiteside's line(WL), and posterior condylar axis (PCA) are commonly used to determine the rotational alignment of the femur in total knee arthroplasty (TKA). It has been previously reported that may be gender differences in the rotational and mechanical anatomy of the distal femur1. The aim of our study was to examine the distal femur in a large number of patients to report on any gender differences within the group. The MRIs of a large cohort of prospectively chosen patients (n= 217) were examined retrospectively in order to determine the rotational femoral alignment. Varus/valgus relationship of their knees prior to prosthesis insertion was also examined. Measurements pertained to femoral rotation (relationships between WL, TEA and PCA) and varus/valgus alignment were calculated directly from MRI studies by a single observer. Gender differences were examined using an unpaired students t-test. Averages and standard deviations are reported to within two significant figures. The posterior condylar axis was 2.6 ± 1.5 degrees relative to the transepicondylar axis and 91.8 ± 1.7 degrees relative to Whiteside's line. The varus to valgus ratio was 4.6 ± 5.9. Males in the group had a PCA of 2.4 ± 1.6 degrees relative to TEA compared to females in the group (2.8 ± 1.4 degrees). There was no significant difference between both groups (p=0.06). The PCA relative to WL was 92.1 ± 1.6 degrees for males compared to 91.6 ± 1.9 degrees for females with no significant difference between both groups (p=0.06). Finally, the varus to valgus ratio was 5 ± 5.7 for males compared to females (4.3 ± 6.2) with no statistical significance achieved between both groups (p=0.39). Our results show that there is no significant difference in the rotational anatomy and varus/valgus alignment between men and women in a large cohort. Interestingly, the large standard deviation for values pertaining to femoral rotational anatomy (>3 degrees) suggest a significant degree of variability between patients. Thus, operative planning embracing our findings may prove to be of great clinical benefit by advocating individualising operative treatment in TKA surgery.
Introduction. The importance of frontal and rotational alignment in total knee arthroplasty has been published. Together with conventional instrumentation, computer navigation has been used for many years now. The pro's and con's of navigation are well known since. Materials & Methods. We present the results of our first 200 total knee arthroplasties with a Patient Specific Instrument System, called Signature (Biomet). With this system an MRI of the hip, knee and ankle is performed. Based on these images, mechanical axis and rotational landmarks are decided. Preoperative planning and templating is done with a computer program. Alignment, rotation, slope, size, positioning and gaps are planned with the software. Based on this templating a femoral guide and a tibial guide are custom made (Materialise) for each patient that will allow only one unique fit and position. Both of these guides are no cutting guides but pinning guides. From that stage on Vanguard Total Knee (Biomet) is implanted with this system applying conventional surgical techniques and rules. Preoperative alignment was measured on standing full leg X-rays.
Introduction. Computed tomography (CT) based preoperative planning provides useful information for severe TKA and revision TKA cases, such as the amount of augmentation, length of stem extension and component alignment, to achieve correct alignment and joint line. In this study, we evaluated TKA alignment performed with CT preoperative planning. Materials and Methods. 7 primary TKAs for severe deformity and 3 revision TKAs were included. CT preoperative planning was performed with JIGEN (LEXI, Japan). Constrained condylar prosthesis (LCCK, Zimmer) were used in all case. For femoral component, axial alignment was decided by controlled IM rod insertion to femoral canal.
