Rotational malalignment in total knee arthroplasty (TKA) may lead to several complications. Transepicondylar axis has been accepted for a reference of femoral rotation. In contrast, standard reference of tibial rotation remains controversial. Currently, two techniques are widely used, the anatomical landmarks technique and the range-of-movement (ROM) technique. Fifty-one patients underwent posterior-stabilized TKA with center-post self-align ROM technique for tibial component placement. Laurin view radiograph and computer tomography (CT) were used to assess the prosthetic position. The rotational mismatch between tibial and femoral components was 2.00° ± 0.34° (range, 0.1°-5.8°). All TKA showed a tibiofemoral mismatch within 10° (range, 0.1° −5.8°). Intraoperative evaluation of patellar tracking by no-thumb test and the Laurin view showed normal range in 90%. We concluded that tibial component placement with center-post self-align technique in PS-TKA can produce good patellar tracking with acceptable range of tibiofemoral mismatch

Introduction. The Rotational alignment is an important factor for survival total knee Arthroplasty. Rotational malalignment causes knee pain, global instability, and wear of the polyethylene inlay. Also, the anterior cortex line was reported that more reliable and more easily identifiable landmark for correct tibial component alignment. The aims of the current study is to identify effect of inserting the tibial baseplate of using anterior cortex line landmark of TKA on stress/strain distributions within cortical bone and bone cement. Through the current study, final aim is to suggest an alternative position of tibia baseplate for reduction of TKA failures with surgical convenience. Materials and Method. A three-dimensional tibia FE model with TKA was generated based on a traditional TKA surgical guideline. Here, a commercialized TKA (LOSPA, Corentc, Korea) was considered corresponded to a patient specific tibia morphology. Tibia baseplate was positioned at anterior cortex line. Alternative two positions were also considered based on tibia tuberosity 1/3 line and tibia tuberosity end line known as a gold standard (Fig. 1-A). Loading and boundary conditions for the FE analysis were determined based on five activities of daily life of persons with TKA (Fig. 1-B). FE model was additionally validated comparing with an actual mechanical test. Results and Discussions. The, through comparing with strain distribution on the cortical bone measured from the actual mechanical test considering 0°, 30° 60°, 90°, 120° and 140° flexion with femoral rollback phenomenon (Fig. 2). Stress/strain on the cortical bone (medial region) of the proximal tibia for the baseplate positioned at anterior cortex line were a little better distributed than those at tibia tuberosity 1/3 line and tibia tuberosity end line although the stress/stain values were similar to each other (Fig. 3-A). Potential fracture risk of the bone cement for the baseplate positioned at anterior cortex line was lower than that at tibia tuberosity 1/3 line and tibia tuberosity end line, considering safety factor (N=3). Particularly, Potential fracture risk of the bone cement for the baseplate positioned at tibia tuberosity 1/3 line known as a gold standard was highest (over 20MPa for stair down activity) (Fig. 3-B). Conclusion. Our results suggested that anterior cortex line landmark was feasible to apply positioning method on the tibial baseplate in terms of mechanical characteristics which were compared to tibia tuberosity 1/3 line and tibia tuberosity end line known as a gold standard. This study may be valuable by suggesting for the first time an alternative baseplate position for reduction of TKA failures with surgical convenience

Objective. 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). Methods. 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. Results. The average MPR CTA in OA patients is 6.7 ± 2.1°, while the average MPR CTA in RA patients is 7.1 ± 2.0° (Fig 2A). On the other hand, the average Navi. CTA is 4.9 ± 2.1°, while the average Navi. CTA is 6.0 ± 2.1° (Fig. 2B). The difference of these two angles that corresponds to the cartilage remnant is 1.8 ± 1.4° in OA group and 1.1 ± 1.0° in RA groups. When we compared these angles between OA and RA population, the MPR CT – Navi CT was smaller in OA population than that of RA population (p < 0.05) (Fig. 2C). Conclusion. These results has demonstrated that twist angle measured on the X-rays or CT that does not include the cartilage would be overestimated compared to the true twist angle that includes cartilage in osteoarthritic knee. The effect of posterior condylar cartilage has less impact on femoral rotation in RA population

INTRODUCTION. 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. METHODS. 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. RESULTS. The results are listed in Fig 2. The rotational angle read from the image-based device showed misalignments in the range of 0.53° to 5.94° (RMS error=3.67°). After alignments were corrected, the final cut accuracy was in the range of 0.3° to 0.74° (RMS error=0.5°). DISCUSSION. The introduced device was very accurate (0.5°) in correcting the rotational alignment of the femoral component. The range of errors for defining the boney landmarks through palpation and visualization is expected to be much larger than was observed in this work (RMS error =3.67°), due to soft tissue obstructions and time pressure during surgery. This would highlight the value of the device even more. The introduced technology is expected to add about 5 to 10 minutes to the surgery at a safe radiation dose comparable to a round transatlantic flight. The surgeon and staff can keep a safe distance during the short imaging time. CONCLUSION. The introduced device provides a fast and safe tool for improving component alignments in total knee arthroplasty

Introduction:. Despite all the attention to new technologies and sophisticated implant designs, imperfect surgical technique remains a obstacle to improving the results of total knee replacement (TKR). On the tibial side, common errors which are known to contribute to post-operative instability and reduced function include internal rotation of the tibial tray, inadequate posterior slope, and excessive component varus or valgus. However, the prevalence of each error in surgeries performed by surgeons and trainees is unknown. The following study was undertaken to determine which of these errors occurs most frequently in trainees acquiring the surgical skills to perform TKR. Materials and Methods:. A total of 43 knee replacement procedures were performed by 11 surgical trainees (surgical students, residents and fellows) in a computerized training center. After initial instruction, each trainee performed a series of four TKR procedures in cadavers (n = 2) and bone replicas (n = 2) using a contemporary TKR instrument set and the assistance of an experienced surgical instructor. Prior to each procedure, computer models of each cadaver and/or bone replica tibia were prepared by reconstructing CT scans of each specimen. All training procedures were performed in a navigated operating room using a 12 camera motion analysis system (Motion Analysis Inc.) with a spatial resolution in all three orthogonal directions of ± 0.15 mm. The natural slope, varus/valgus alignment, and axial rotation of the proximal tibial surface were recorded prior to surgery and after placement of the tibial component. For evaluation of all data, acceptable limits for implantation were defined as: posterior slope: 0–10°; varus/valgus inclination of tibial resection: ± 3°; and external rotation: 0–10°. Results:. The tibial component was implanted with an average posterior slope of 3.4° ± 3.4°. In 83% of trials, the trainees cut the tibia with less posterior slope than intended (average shortfall: 2.0° ± 4.0°). In 14% of cases the tibial resection sloped anteriorly, whereas in another 5% the posterior slope exceeded 10°. The coronal alignment of the tibial osteotomy averaged 0.1° ± 2.9° of valgus, with 19% of components were implanted in more than 3° of valgus vs. 14% varus (>3°). The average rotational orientation of the tibial component was 5.4° ± 5.3° of external rotation. Overall, 21% of components were placed in internal rotation, and a further 29% in more than 10° of external rotation. Rotational malalignment of the tibial component was the most common error in technique encountered in the study population. Conclusion:. 1. Tibial preparation still presents significant difficulty to many less experienced surgeons, despite the use of modern instrumentation and careful didactic instruction. 2. The most prevalent error in tibial preparation in TKR is malrotation of the tibial component, especially in internal rotation. 3. The errors measured in the computerized bioskills lab replicate clinical cases often presenting with symptoms necessitating early revision. 4. Greater attention is needed to training of surgical skills and intraoperative assessment of sources of technical error, such as component position to improve clinical outcomes of TKR