Background:. Varus or Valgus malpositioning of tibial prosthetic components in total knee replacement (TKR) surgery may lead to early failure due to increased polyethelene wear, soft tissue imbalancing, aseptic loosening and eventually revision surgery. Therefore, the clinical success of total knee arthroplasty (TKA) correlates with good component alignment. Conventional methods of coronal tibial alignment result in an acceptable range of prosthetic alignment in relation to the anatomical axis (tibial tangent angle). The measurement ranges from 90° ± 3°, but literature quotes that there is up to 27% of cases with coronal tibial alignment deviation of greater than 3°. Many studies show that the use of conventional intramedullary rod alignment versus extramedullary rod alignment gives similar results. The tibial alignment and overall prosthetic alignment in TKA has improved remarkably by using computerized navigation assisted surgery (CAS), with tibial tangent angle of 90° ± 3 in up to 97% of cases. However, the success of accurate tibial and femoral alignment depends on the surgeon and the data fed to the computer. Also long term results on survival rates of TKR using CAS is still pending. It is clear that assessing tibial alignment (ie. anatomical axis) with whatever method used faces challenges which will affect the tibial bony cuts and the final tibial tangent angle. To achieve a 90° tibial cut in relation to the anatomical axis we made use of fluoroscopy intra-operatively to assess the anatomical axis of the tibia and the correct alignment of the tibial cutting block. Methods:. TKR's were performed on 36 consecutive patients over a 4 month period. The aim was to assess the coronal tibial alignment of the tibial component intra-operatively using fuloroscopy. A conventional manual extramedullary alignment rod with its tibial cutting block was used and the final positioning was confirmed with an image intensifier. The tibial cutting block must be at 90° to the anatomical axis of the tibia. The rest of the TKR procedures were performed as routinely described. Post-operative radiographs were taken on the same day as the surgery and again at six week follow up visit when the tibial tangent angle was measured. Results:. The coronal tibial angulation was consistent at 0° in 32 knees with a 1°–2° deviation in 4 knees. Conclusion:. We conclude that the use of fluoroscopy intra-operatively can improve the tibial component alignment and thus decrease the cumulative errors which have significant and dramatic effects on the function and the longevity of the total knee prosthesis

Clinical success of total knee arthroplasty is correlated with correct orientation of the components. Controversy remains in the orthopaedic community as to whether the intramedullary or extramedullary tibial alignment guide is more accurate in the tibial cut. Is there any difference between intramedullary and extramedullary jigs to achieve better accuracy of the tibial components in total knee replacements?. A retrospective study done on 100 patients during the time period 2007 to 2010. The 100 knee replacements were done by the same surgeon, where 50 patients had the intramedullary tibial alignment guide and the other 50 had the extramedullary one. The tibiofemoral angle was measured pre-operatively as well as post operatively, the tibial alignment angle was measured post operatively then the results were statistically analysed using the SPSS. There was no significant difference between both groups regarding the tibial alignment angles. Both techniques proved accurate in producing an acceptable post operative tibial component alignment angle. We recommend orthopaedic surgeons choose either technique knowing that accuracy levels are similar. The debate between intramedullary and extramedullary tibial cutting jigs/guides/ devices continues and most orthopaedic surgeons will use their preferred technique and will continue to achieve good post operative results as we have found in our centre. Our study is rare due to the fact we have a single surgeon performing both techniques, therefore controlling for any surgical experience or operating technique differences

Background:. Conventional, extramedullary (EM) tibial alignment guides are only 65%–88% accurate in creating a tibial resection within 2° of perpendicular to the tibial mechanical axis in total knee arthroplasty (TKA). The purpose of this study was to compare the overall, tibial component alignment, and the surgeon's ability to achieve a specific, intraoperative goal for alignment between a portable, navigation system (KneeAlign™) and conventional, EM alignment guides. Methods:. One hundred patients were enrolled in a prospective, randomized controlled study. Fifty patients received a TKA using the KneeAlign™ to perform the tibial resection, and 50 patients an EM alignment guide. Standing AP hip-to-ankle radiographs and lateral knee-to-ankle radiographs were obtained at the first, postoperative visit. Results:. 95.7% of tibial components in the KneeAlign™ cohort were within 2° of perpendicular to the tibial mechanical axis, versus 68.1% in the conventional cohort (p < 0.001). 95.0% of the tibial components in the KneeAlign™ cohort were within 2° of a 3° posterior slope, versus 72.1% in the conventional cohort (p = 0.007). The absolute difference between the intraoperative goal (as recorded by the surgeon) and postoperative alignment for tibial component varus/valgus was 0.9° + 0.7° in the KneeAlign™cohort, versus 1.5° + 1.1° in the conventional cohort (p < 0.001). For posterior slope, the absolute difference was 0.9° + 1.2° in the KneeAlign™ cohort, versus 1.8° + 1.7° in the conventional cohort (p = 0.01). Conclusions:. A portable, navigation system improves tibial component alignment, and the surgeon's ability to achieve a specific, intraoperative goal, when compared to conventional, EM alignment guides in TKA. Level of Evidence: Level I, Prospective, randomized controlled study

Background:

The axis of the fibula in the sagittal plane are known as a landmark for the extramedullary guide in order to minimize posterior tibial slope measurement error in the conventional total knee arthroplasty (TKA). However, there are few anatomic studies about them. We also wondered if the fibula in the coronal plane could be reliable landmark for the alignment of the tibia. This study was conducted to confirm whether the fibula is reliable landmark in coronal and sagittal plane.

INTRODUCTION

The alignment of components in total knee arthroplasty (TKA) is perceived to be one of the most influential factors in determining the long-term outcomes. A contemporary debate exists regarding the choice of the alignment method. As a vast majority of the surgeons support the basis of the mechanical alignment philosophy (MA), others believe in the concept of anatomical alignment theory (AA) to closely match the anatomy of the femur and the tibia of the native knee [1]. This study was intended to evaluate the accuracy of achieving a planned tibial resection target using either the MA or AA methods.

Introduction and Aims. Sensor technology is seeing increased utility in joint arthroplasty, guiding surgeons in assessing the soft tissue envelope intra-operatively (OrthoSensor, FL, USA). Meanwhile, surgical navigation systems are also transforming, with the recent introduction of inertial measurement unit (IMU) based systems no longer requiring optical trackers and infrared camera systems in the operating room (i.e. OrthAlign, CA, USA). Both approaches have now been combined by embedding an IMU into an intercompartmental load sensor. As a result, the alignment of the tibial varus/valgus cut is now measured concurrently with the mediolateral tibiofemoral contact load magnitudes and locations. The wireless sensor is geometrically identical to the tibial insert trial and is placed on the tibial cutting plane after completing the proximal tibial cut. Subsequently, the knee is moved through a simple calibration maneuver, rotating the tibia around the heel. As a result, the sensor provides a direct assessment of the obtained tibial varus/valgus alignment. This study presents the validation of this measurement. Method. In an in-vitro setting, sensor-based alignment measurements were repeated for several simulated conditions. First, the tibia was cut in near-neutral alignment as guided by a traditional, marker-based surgical navigation system (Stryker, MI, USA). Subsequently, the sensor was inserted and a minimum of five repeated sensor measurements were performed. Following these measurements, a 3D printed shim was inserted between the sensor and the tibial cutting plane, introducing an additional 2 or 4 degrees of varus or valgus, with the measurements then being repeated. Again, for each condition, a minimum of five sensor measurements were performed. Following completion of the tests, a computed tomography (CT) scan of the tibia was obtained and reconstructed using open source software (3DSlicer). Results. By identifying anatomic landmarks on the 3D reconstructed tibia and fibula, the actual tibial coronal alignment of 0.43° valgus was obtained (Figure 1a), in close agreement with the one degree valgus alignment reported by the optical navigation system. Both reference values match well with the 1.16° valgus (SD: 0.91°) calculated by the IMU- based sensor system. When introducing the shims, the sensor consistently predicts the relative angular changes, with a maximum relative difference between the expected and measured condition of 1.29°. For each condition, the standard deviation remained small, with values ranging from 0.27° to 0.60° based on at least five repeated measures (Figure 1b). Conclusion. In conclusion, this paper demonstrates that sensor technology can be used to evaluate tibial coronal alignment, with an accuracy in line with available 3D measurement systems. The authors recognize however the need for further validation, currently being undertaken

INTRODUCTION. Cemented total knee arthroplasty (TKA) is a widely accepted treatment for end-stage knee osteoarthritis. During this procedure, the surgeon targets proper alignment of the leg and balanced flexion/extension gaps. However, the cement layer may impact the placement of the component, leading to changes in the mechanical alignment and gap size. The goal of the study was to assess the impact of cement layer on the tibial mechanical alignment and joint gap during cemented TKA. MATERIAL. Computer-assisted TKAs (ExactechGPS®, Blue-Ortho, Grenoble, FR) were performed by two fellowship trained orthorpaedic surgeons on five fresh-frozen non-arthritic pelvis-to-ankle cadaver legs. All the surgeries used a cemented cruciate retaining system (Optetrak Logic CR, Exactech, Gainesville, FL). After the bony resection, the proximal tibial resection plane was acquired by manually pressing an instrumented checker onto the resected tibial surface (resection plane). Once the prosthesis was implanted through standard cementing techniques, the top surface of the implanted tibial component was probed and recorded using an instrumented probe. A best fit plane was then calculated from the probed points and offset by the thickness of the prosthesis, representing the bottom plane of the component (component plane). The deviation of component alignment caused by the cement layer was calculated as the coronal and sagittal projection of the three-dimensional angle between the resection plane and the component plane. The deviation of the component height, reflecting a change in the joint gap, was assessed as the distance between the two planes calculated at the lowest points on the medial and lateral compartments of the proximal tibial surface. Statistical significance was defined as p≤0.05. RESULTS. The differences in alignment and component height between the tibial component placement and the ideal placement based on the bony resection are presented in Table 1. The magnitude of deviation in alignment was 1.2±0.9° for varus/valgus and 1.7±0.7° for posterior slope, with a tendency towards valgus (−0.2±1.6°) and reduced posterior slope (0.6±1.9°). The lateral compartment (2.4±0.9mm) had a generally higher increase in the height of the component compared to the medial compartment (1.0±0.9mm), the difference was close to being statistically significant (p=0.055). DISCUSSION. The finding of this study demonstrated that standard cement fixation during TKA may potentially influence the alignment and position of the tibial component. The formed cement layer generally results in elevated height, slightly more varus tibial alignment (overall limb valgus alignment) and less posterior slope in the implanted component. The results on the alignment are comparable to a previous study by Catani et al. [1]. More than 2°/2mm of deviation was found in the sagittal alignment (2 out of 5 knees), and medial (1 out of 5 knees) and lateral (3 out of 5 knees) component height, which may clinically impact the joint gap [2]. The varus/valgus alignment deviation found was clinically acceptable (≤3°). However when combined with other surgical variables, the accumulated impact on the alignment may warrant more investigation

Introduction. Using the tibial extramedullary guide needs meticulous attention to accurately align the tray in total knee arthroplasty (TKA). We previously reported the risk for varus tray alignment if the anteroposterior (AP) axis of the ankle was used for the rotational direction of the guide. The purpose of our study was to determine whether aligning the rotational direction of the guide to the AP axis of the proximal tibia reduced the incidence of varus tray alignment when compared to aligning the rotational direction of the guide to the AP axis of the ankle. Materials and Methods. Clinical Study. A total of 80 osteoarthritis (OA) knees after posterior stabilized TKA were recruited in this study. From 2002 to 2004, the rotational alignment of the guide was adjusted to the AP axis of the ankle (Method A: Figure 1, N = 40 knees). After 2005, the rotational alignment of the guide was adjusted to the AP axis of the proximal tibia (Method B: Figure 1, N = 40 knees). The AP axis of the proximal tibia was defined as the line connecting the middle of the attachment of the PCL and the medial third border of the attachment of the patellar tendon. The guide was set at a level of 10 mm distal to the lateral articular surface. Postoperative alignment was compared between the two groups using full-lengthanteroposterior radiograph. Computer simulation. Computer simulation was performed to determine the effect of ankle rotation on tibial tray alignment, using three-dimensional bone and skin model reconstructed from CT images of 75 OA knees (Figure 2). The position of the distal end of the guide in Method B was evaluated on the coronal plane perpendicular to the AP axis of the proximal tibia and of the ankle respectively. <Displacement> was the distance from the distal end of the guide to the midpoint-malleolar points (+: medial position). <Distance ratio> was the ratio of <Displacement> dividing by the entire width of the malleolar. Results. The results of the postoperative alignment for both methods from the clinical study are shown in Table 1. The number of the knees with more than 3 degrees of varus aligned tibial component significantly decreased with the Method B from the Method A. The computer simulation showed that the position of the guide varied great among individuals in the direction of the AP axis of the ankle joint. Discussion. When an extramedullary alignment guide is used in TKA, a rotational mismatch between the proximal part of the tibia and the ankle joint can induce a varus alignment of the tibial component. Computer simulation also supported our conclusion that the surgeon should not evaluate the distal end of the guide in the direction of the ankle joint to minimize the effects of anatomic variation for proper coronal alignment

Introduction

It has been reported that the tibial articular surface of coronal aligment is parallel to the floor in the whole-leg standing radiographs of the normal knee. The purposes of this study are to investigate the relationship between the tibial articular surface and the ground on the whole-leg standing radiographs after total knee arthroplasty(TKA).

Although optimal alignment is essential for improved function and implant longevity after TKA, we have less bony landmarks of tibia relative to femur. Trans-malleolar axis (TMA) is a reference line of distal tibia in the axial plane, which externally rotated relative to a ML axis of proximal tibia. We originally defined another reference axis associated with the orientation of tibial plafond, and then measured tibial torsion in the 3D-coordinate system.

Three-dimensional CAD models of 20 tibiae were reconstructed based on pre-operative CT data from OA patients (16 females and 4 males, 73.8 ± 6.9 years old). TMA was a line connecting each apex of medial and lateral malleolus. The plafond axis (PLA) that we originally defined in this study was a line connecting each midpoint of medial and lateral margin of talocrural facet. In terms of interobserver correlation coefficiency and mean errors of the designated points to define those axes, TMA was found out to be 0.982, 3.14 ± 0.47 mm (medial), and 0.988, 4.88 ± 0.59 mm (lateral). Those of PLA were 0.997, 1.97 ± 0.53 mm (medial), and 0.995, 2.02 ± 0.44 mm (lateral). The tibial torsion was 16.3 ± 6.3°with reference to TMA, and 10.2 ± 8.4°to PLA.

Based on these results, as for the rotational reference axis in the axial plain of distal tibia, we consider the plafond axis to be another reliable and reproducible axis, which is expected to be applicable in preoperative planning in TKA to reduce outliers of coronal alignment.

Introduction. Varus alignment in total knee replacement (TKR) results in a larger portion of the joint load carried by the medial compartment. [1]. Increased burden on the medial compartment could negatively impact the implant fixation, especially for cementless TKR that requires bone ingrowth. Our aim was to quantify the effect varus alignment on the bone-implant interaction of cementless tibial baseplates. To this end, we evaluated the bone-implant micromotion and the amount of bone at risk of failure. [2,3]. Methods. Finite element models (Fig.1) were developed from pre-operative CT scans of the tibiae of 11 female patients with osteoarthritis (age: 58–77 years). We sought to compare two loading conditions from Smith et al.;. [1]. these corresponded to a mechanically aligned knee and a knee with 4° of varus. Consequently, we virtually implanted each model with a two-peg cementless baseplate following two tibial alignment strategies: mechanical alignment (i.e., perpendicular to the tibial mechanical axis) and 2° tibial varus alignment (the femoral resection accounts for additional 2° varus). The baseplate was modeled as solid titanium (E=114.3 GPa; v=0.33). The pegs and a 1.2 mm layer on the bone-contact surface were modeled as 3D-printed porous titanium (E=1.1 GPa; v=0.3). Bone material properties were non-homogeneous, determined from the CT scans using relationships specific to the proximal tibia. [2,4]. The bone-implant interface was modelled as frictional with friction coefficients for solid and porous titanium of 0.6 and 1.1, respectively. The tibia was fixed 77 mm distal to the resection. For mechanical alignment, instrumented TKR loads previously measured in vivo. [5]. were applied to the top of the baseplate throughout level gait in 2% intervals (Fig.1a). For varus alignment, the varus/valgus moment was modified to match the ratio of medial-lateral force distribution from Smith et al. [1]. (Fig.1b). Results. For both alignments and all bones, the largest micromotion and amount of bone at risk of failure occurred during mid stance, at 16% of gait (Figs.2,3). Peak micromotion, located at the antero-lateral edge of the baseplate, was 153±32 µm and 273±48 µm for mechanical and varus alignment, respectively. The area of the baseplate with micromotion above 40 µm (the threshold for bone ingrowth. [3]. ) was 28±5% and 41±4% for mechanical and varus alignment, respectively. The amount of bone at risk of failure at the bone-implant interface was 0.5±0.3% and 0.8±0.3% for the mechanical and varus alignment, respectively. Discussion. The peak micromotion and the baseplate area with micromotion above 40 µm increased with varus alignment compared to mechanical alignment. Furthermore, the amount of bone at risk of failure, although small for both alignments, was greater for varus alignment. These results suggest that varus alignment, consisting of a combination of femoral and tibial alignment, may negatively impact bone ingrowth and increase the risk of bone failure for cementless tibial baseplates of this TKR design

Various types of tibial alignment guides exist, the results in performing the tibial resection in total knee arthroplasty (TKA) are more or less than we desired. In addition, it is difficult to estimate the accuracy of tibial component alignment with radiograph because it is difficult to get true frontal and lateral view. In this study, we use new tibial alignment guide and estimate tibial component alignment by using postoperative CT scan. 30 knees underwent TKA using an accelerometer-based, portable navigation device (KneeAlign 2) and postoperative CT scans were obtained. Postoperative CT scans of the lower limbs analysed by 3D digital template system (Athena), demonstrated that 96.6% of the tibial components were placed within 90°± 2°to the mechanical axis in the coronal plane, and 96.6% of the components were placed within 3°± 2°to the mechanical axis in the sagittal plane. As a result of this study, an accelerometer-based, portable navigation device can expect to decrease outliers in tibial component alignment

The iASSIST system is a portable, accelerometer base with electronic navigation used for total knee arthroplasty (TKA) which guides the surgeon to align and validate bone resection during the surgical procedure. The purpose of this study was to compare the radiological outcome between accelerometer base iASSIST system and the conventional system. Method. A prospective study between two group of 36 patients (50 TKA) of primary osteoarthritis of the knee who underwent TKA using iASSIST ™ or conventional method (25 TKA in each group) from January 2018 to December 2019. A single surgeon performs all operations with the same instrumentation and same surgical approach. Pre-operative and postoperative management protocol are same for both groups. All patients had standardized scanogram (full leg radiogram) performed post operatively to determine mechanical axis of lower limb, femoral and tibial component alignment. Result. There was no significant difference between the 2 groups for Age, Gender, Body mass index, Laterality and Preoperative mechanical axis(p>0.05). There was no difference in proportion of outliers for mechanical axis (p=0.91), Coronal femoral component alignment angle (p=0.08), Coronal tibial component alignment angle (p=1.0). The mean duration of surgery, postoperative drop in Hb, number of blood transfusion didn't show significant difference between 2 groups (p>0.05). Conclusion. Our study concludes that despite being a useful guidance tool during TKA, iASSIST does not show any difference in limb alignment (mechanical axis), Tibial and femoral component alignment when compared with the conventional method

Introduction. Component position and overall limb alignment following total knee arthroplasty (TKA) have been shown to influence prosthetic survivorship and clinical outcomes. Robotic-assisted (RA) total knee arthroplasty has demonstrated improved accuracy to plan in cadaver studies compared to conventionally instrumented (manual) TKA, but less clinical evidence has been reported. The objective of this study was to compare the three-dimensional accuracy to plan of RATKA with manual TKA for overall limb alignment and component position. Methods. A non-randomized, prospective multi-center clinical study was conducted to compare RATKA and manual TKA at 4 U.S. centers between July 2016 and August 2018. Computed tomography (CT) scans obtained approximately 6 weeks post-operatively were analyzed using anatomical landmarks. Absolute deviation from surgical plans were defined as the absolute value of the difference between the CT measurements and surgeons’ operative plan for overall limb, femoral and tibial component mechanical varus/valgus alignment, tibial component posterior slope, and femoral component internal/external rotation. We tested the differences of absolute deviation from plan between manual and RATKA groups using stratified Wilcoxon tests, which controlled for study center and accounted for skewed distributions of the absolute values. Alpha was 0.05 two-sided. At the time of this abstract, data collections were completed for two centers (52 manual and 58 RATKA). Results. Comparing absolute deviation from plan between groups, RATKA demonstrated clear benefits for tibial component alignment (median absolute deviation from plan: 1.5° vs. 0.8°, manual vs RATKA, p<.001), tibial slope (2.7° vs. 1.1°, manual vs RATKA, p<.001), and femoral component rotation (1.4° vs. 0.9°, manual vs RATKA, p<0.02). Femoral component and overall limb alignment accuracy were comparable (p>0.10). Discussion and Conclusions. In this study, compared to manual TKA, RATKA cases were 47% more accurate for tibial component alignment, 59% more accurate for tibial slope, and 36% more accurate for femoral component rotation (percent differences of median absolute deviations from plan). Further clinical data is needed to study the longer-term benefits of robotic technologies. Nevertheless, this study supports improved accuracy to plan utilizing RATKA compared to manual TKA. For any figures or tables, please contact authors directly

A prospective randomized trial on 128 patients with end-stage osteoarthritis was conducted to assess the accuracy of patient-specific guides. In cohort A (n = 64), patient- specific guides from four different manufacturers (Subgroup A1 Signature ®, A2 Trumatch ®, A3 Visionaire ® and A4 PSI ®) were used to guide the bone cuts. Surgical navigation was used as an intraoperative control for outliers. In cohort B (n = 64), conventional instrumentation was used. All patients of cohorts A and B underwent a postoperative full-leg standing X-ray and CT scan for measuring overall coronal alignment of the limb and three-planar alignment of the femoral and the tibial component. Three-planar alignment was the primary endpoint. Deviation of more than three degrees from the target in any plane, as measured with surgical navigation or radiologic imaging, was defined as an outlier. In 14 patients (22%) of cohort A, the use of the patient-specific guide was abandoned because of outliers in more than one plane. In 18 patients (28%), a correction of the position indicated by the guide, was made in at least one plane. A change in cranial-caudal position was most common. Cohort A and B showed a similar percentage of outliers in long-leg coronal alignment (24.6%, 28.1%, p = 0.69), femoral coronal alignment (6.6%, 14.1%, p = 0.24) and femoral axial alignment (23%, 17.2%, p = 0.50). Cohort A had more outliers in coronal tibial alignment (14.6%) and sagittal tibial alignment (21.3%) than cohort B (3.1%, p = 0.03 and 3.1%, p = 0.002, respectively). These data indicate that patient specific guides do not improve accuracy in total knee arthroplasty

Computer-assisted orthopaedic surgery (CAOS) improves mechanical alignment and the accuracy of surgical cuts in the context of total knee arthroplasty. A simplified, CAOS enhanced instrumentation system was assessed to determine if the same effects could be achieved through the use of a less intrusive system. Two cohorts of surgeons (experienced and trainees) performed a series of total knee arthroplasty resections in knee models with and without navigation-enhanced instrumentation. The percentage of resections that deviated from the planned cut by more than 2°or 2mm (outliers) was determined by post-resection advanced imaging for six unique outcome metrics. Within each experience level, the use of the CAOS enhanced system significantly reduced the total percentage of outliers as compared to conventional instrumentation (Figure 1). The experienced users improved from 35% to 4% outliers overall (p < .001) and the trainees from 34% to 10% outliers (p < .001). Comparing across experience levels, the experienced surgeons performed significantly better in only a single resection metric with conventional instrumentation (Figure 2A), varus/valgus tibial alignment, with 8.3% outliers compared to the trainee's 63% outliers (p = .004). The use of CAOS enhanced instrumentation eliminated any differences between the two user groups for all measured resections (Figure 2B). Comparing CAOS enhanced to conventional instrumentation specifically between anatomical deformity types revealed that there is significant improvement (p < .05) with the use of enhanced instrumentation for all three deformity types (Figure 3). These results suggest that non-intrusive CAOS enhanced instrumentation is a viable alternative to conventional instrumentation with possible benefits. This trial also demonstrates that additional experience may not correlate to improved surgical accuracy, and outliers may be less a result of individual surgeon ability or specific anatomic deformities, and more so related to limitations of the instrumentation used or other yet unidentified factors

Robotic-assisted technology in total knee arthroplasty (TKA) aims to increase implantation accuracy, with real-time data being used to estimate intraoperative component alignment. Postoperatively, Perth computed tomography (CT) protocol is a valid measurement technique in determining both femoral and tibial component alignments. The aim of this study was to evaluate the accuracy of intraoperative component alignment by robotic-assisted TKA through CT validation. A total of 33 patients underwent TKA using the MAKO robotic-assisted TKA system. Intraoperative measurements of both femoral and tibial component placements, as well as limb alignment as determined by the MAKO software were recorded. Independent postoperative Perth CT protocol was obtained (n.29) and compared with intraoperative values. Mean absolute difference between intraoperative and postoperative measurements for the femoral component were 1.17 degrees (1.10) in the coronal plane, 1.79 degrees (1.12) in the sagittal plane, and 1.90 degrees (1.88) in the transverse plane. Mean absolute difference between intraoperative and postoperative measurements for the tibial component were 1.03 degrees (0.76) in the coronal plane and 1.78 degrees (1.20) in the sagittal plane. Mean absolute difference of limb alignment was 1.29 degrees (1.25), with 93.10% of measurements within 3 degrees of postoperative CT measurements. Overall, intraoperatively measured component alignment as estimated by the MAKO robotic-assisted TKA system is comparable to CT-based measurements

Long-term implant survivorship in total knee arthroplasty (TKA) depends on the alignment of the tibial and femoral components, as well as on the mechanical alignment of the leg. Computer navigation improves component and limb alignment in TKA compared to the manual technique. However, its use is often associated with an increase in surgical time. We aimed to evaluate the use of adjustable cutting blocks (ACB) in navigated TKA. We hypothesised that the use of ACB would (1) improve tibial and femoral component positioning; (2) improve postoperative mechanical leg alignment; and (3) decrease tourniquet time, when compared to conventional cutting blocks (CCB). This was a retrospective cohort study of 94 navigated primary TKA. Patients were classified into two groups according to whether the surgery had been performed using ACB or CCB. There were sixty-four patients in the CCB group and 30 patients in the ACB group. Charts were reviewed to obtain the following data: age, gender, body mass index (BMI), tourniquet time and operated side. Pre- and postoperative standing full-leg radiographs and lateral radiographs were reviewed. Mean coronal femoral alignment for the CCB group was 0.8® varus (SD = 1.95®) and for the ACB group it was 1.1® varus (SD = 1.5®) (P = 0.12). Mean coronal tibial alignment for the CCB group was 0.1® valgus (SD = 1.3®) and for the ACB group it was 0.5® varus (SD = 1.01) (P = 0.15). Sagittal tibial alignment was a mean 0.5® of anterior slope (SD = 2.9®) for the CCB group and 0.7® anterior slope (SD = 2.5®) for the ACB group (P = 0.38). Preoperatively, the CCB group had a mean mechanical alignment of 1.8® varus (SD = 9.6®), while the ACB group had a mean 1.8® varus (SD = 9.37®) (P = 0.88). After surgery, mechanical leg alignment for the CCB group improved to a mean 0.7® varus (SD = 2.7®) (P = 0.0001), while the ACB group improved to 1.8® varus (SD = 1.7®) (P<0.0001). There was significantly less variability in postoperative mechanical alignment in the ACB group (P = 0.0091). Mean tourniquet time for the CCB group was 91 minutes (SD = 17.7 minutes). The ACB group a mean tourniquet time of 76 minutes (SD = 16.7 minutes) (P = 0.01). In the multiple linear regression model, the use of an ACB reduced tourniquet time by 16.8 minutes (P = 0.001). Adjustable cutting blocks for TKA significantly reduced postoperative mechanical alignment variability and tourniquet time compared to conventional navigated instrumentation, while providing equal or better component alignment

Introduction. Robotics have been applied to total knee arthroplasty (TKA) to improve surgical precision in component placement and joint function restoration. The purpose of this study was to evaluate prosthetic component alignment in robotic arm-assisted (RA)-TKA performed with functional alignment and intraoperative fine-tuning, aiming for symmetric medial and lateral gaps in flexion/extension. It was hypothesized that functionally aligned RA-TKA the femoral and tibial cuts would be performed in line with the preoperative joint line orientation. Methods. Between September 2018 and January 2020, 81 RA cruciate retaining (CR) and posterior stabilized (PS) TKAs were performed at a single center. Preoperative radiographs were obtained, and measures were performed according to Paley's. Preoperatively, cuts were planned based on radiographic epiphyseal anatomies and respecting ±3° boundaries from neutral coronal alignment. Intraoperatively, the tibial and femoral cuts were modified based on the individual soft tissue-guided fine-tuning, aiming for symmetric medial and lateral gaps in flexion/extension. Robotic data were recorded. Results. A total of 56 RA-TKAs performed on varus knees were taken into account. On average, the tibial component was placed at 1.9° varus (SD 0.7) and 3.3° (SD 1.0) in the coronal and sagittal planes, respectively. The average femoral component alignment, based on the soft tissue tensioning with spoons, resulted as follows: 0.7° varus (SD 1.7) in the coronal plane and 1.8° (SD 2.1) of external rotation relative to surgical transepicondylar axis in the transverse plane. A statistically significant linear direct relationship was demonstrated between radiographic epiphyseal femoral and tibial coronal alignment and femoral (r=0.3, p<0.05) and tibial (r=0.3, p<0.01) coronal cuts, resepctively. Conclusion. Functionally aligned RA-TKA performed in varus knees, aiming for ligaments’ preservation and balanced flexion/extension gaps, provided joint line respecting femoral and tibial cuts on the coronal plane

INTRODUCTION. To obtain appropriate joint gap and soft tissue balance, and to correct the lower limb alignment are important factor to achieve success of total knee arthroplasty (TKA). A variety of computer-assisted navigation systems have been developed to implant the component accurately during TKA. Although, the effects of the navigation system on the joint gap and soft tissue balance are unclear. The purpose of the present study was to investigate the influence of accelerometer-based portable navigation system on the intraoperative joint gap and soft tissue balance. METHODS. Between March 2014 and March 2015, 36 consecutive primary TKAs were performed using a mobile-bearing posterior stabilized (PS) TKA (Vanguard RP; Biomet) for varus osteoarthritis. Of the 36 knees, 26 knees using the accelerometer-based portable computer navigation system (KneeAlign2; OrthAlign) (N group), and 10 knees using conventional alignment guide (femur side; intramedullary rod, tibia side; extramedullary guide) (C group). The intraoperative joint gap and soft tissue balance were measured using tensor device throughout a full range of motion (0°, 30°, 45°, 60°, 90°, 120°and full flexion) at 120N of distraction force. The postoperative component coronal alignment was measured with standing anteroposterior hip-to-ankle radiographs. RESULTS. The mean joint gaps at each flexion angle were maintained constant in N group, and there was a tendency of the joint gap at midflexion ranges to increase in C group. The joint gaps at 30°and 45°of flexion angle in C group were significantly larger than that of in N group. The mean soft tissue balance at 0°of flexion was significantly varus in N group than that of in C group. Postoperatively, in N group, the mean femoral component alignment was valgus 0.1°± 1.3°(range, varus 2°- valgus 3°), the mean tibial component alignment was valgus 1.1°± 1.7°(range, varus 1°- valgus 3°) to the coronal mechanical axis. In C group, the mean femoral component alignment was varus 2.3°± 1.9°(range, varus 6°- valgus 1°), the mean tibial component alignment was valgus 2.0°± 1.3°(range, 0°- valgus 5°) to the coronal mechanical axis. There was statistically significant difference in femoral component alignment, there was no statistically significant difference in tibial component alignment. DISCUSSION AND CONCLUSION. The present study demonstrated that navigation-assisted TKA was prevented the joint gaps from increasing at 30°and 45°of flexion. However, it was difficult to achieve soft tissue balance at extension. In conventional TKA, the femoral component alignment was usually varus. In contrast, accelerometer-based portable navigation system is superior to implant the femoral component accurately. However, there were several cases that femoral component alignment is valgus because of a variation in the accuracy of this navigation system. Surgeons should be aware of difficulty to accomplish all of appropriate joint gap and soft tissue balance, and lower limb alignment in navigation-assisted TKA