Introduction. Low dose technology of an EOS scanner allows mechanical axis radiographs to be produced using a continuously moving x-ray emitting a thin beam to form a single image which includes all three joints, without the need for stitching. The aim of this study was to identify necessary improvements to enable effective interpretation of the radiographs, and to assess whether the quality of the radiographs varied by production method compared to a previous audit of CR and DR radiographs. Materials and Methods. 8 domains were identified based on a previous audit using the acronym MECHANIC each defining the qualities required for a radiograph to meet the criteria. 100 mechanical axis radiographs produced using conventional and digital methods were analysed in the original study to assess how many radiographs met the described criteria. The same criteria were amended and used to assess 123 different mechanical axis radiographs in the follow up study following the introduction of the EOS scanner, in which 77 were produced using EOS and 46 were produced using conventional and digital methods. Results. The second study showed improvement in 2 of the 6 domains being assessed and the result remained the same in 1 domain, with a mean change of +2%. There was a large increase in the number of radiographs with impeccable stitching in the second study due to the use of the EOS scanner. When comparing the methods of production, there were a greater percentage of EOS radiographs meeting the criteria for each domain compared to conventional and digital radiographs. Those produced using the EOS scanner had a mean 0.83% more radiographs meeting the criteria per domain. Conclusions. The overall quality of mechanical axis radiographs being produced has increased, but varies largely between the 6 domains. The EOS produced radiographs overall were of a greater quality than those produced using conventional and digital methods, but still had areas which required significant improvement

The weight bearing axis of the limb goes from the pelvis to the ground and includes the hindfoot. However, the influence of hindfoot alignment on mechanical axis deviation and overall limb alignment after total knee arthroplasty (TKA) is unknown. This study aimed to assess the change in hindfoot alignment after TKA for knee osteoarthritis, the difference in mechanical axis deviation at the knee when calculated using the ground mechanical axis as compared to the conventional mechanical axis, and the effect of hindfoot alignment on the overall postoperative limb alignment after TKA. We evaluated the pre- and postoperative hip-knee-ankle (HKA) angle, conventional mechanical axis deviation (CMAD), ground mechanical axis deviation (GMAD), and tibiocalcaneal angle (TCA) in 125 patients who underwent 165 consecutive TKAs. Overall, the change in pre- and postoperative mean TCA was not significant (p=0.48) whereas it was significant (p=0.01) in knees with =15° deformity where the hindfoot valgus decreased by approximately 25%. Preoperatively, there was no significant difference between mean CMAD and mean GMAD whereas postoperatively the difference was significant (p=0.0001). Hindfoot valgus alignment of =10° was present in 22.5% of limbs and 29% limbs had a postoperative GMAD of =10 mm in spite of the limb alignment being restored to within 3° of neutral after TKA. Despite accurate restoration of limb alignment after TKA, as a result of persistent hindfoot valgus alignment the ground mechanical axis may pass lateral to the centre of the knee joint - with potential detrimental effects on bone, ligaments and implants

For a successful total knee arthroplasty (TKA) and long prosthesis lifespan, correct alignment of the implant components as well as proper soft tissue balancing are of major importance. In order to overcome weaknesses of existing imaging modalities for TKA planning such as radiation exposure and lack of soft tissue visualisation (X-ray and CT) and high cost, long acquisition times and geometric distortion (MRI), it is investigated if ultrasound (US) imaging is a suitable alternative. Currently, a reconstruction method of the bony knee morphology based on US imaging is developed at our research institute. For capturing the mechanical axis, being crucial for TKA planning, different approaches could be implemented. This work investigates whether a weight-bearing full leg X-ray registered with the local 3D-US knee dataset can be used for this purpose. Also, the impact of incorrect calibration data (i.e. uncalibrated X-rays) on the accuracy of the estimated mechanical axis is investigated. A 3D-2D projective, feature-based registration algorithm was used to spatially align the 3D US-based model to the 2D X-ray image before transferring the mechanical axis from the X-ray to the model. For validation, a CT-based local model and its projection were used and an initial error in translation and rotation was added. Also, calibration parameters such as the centre ray position and the source-to-image-detector distance were altered. The estimation error of the mechanical axis was less than 1°, the median error lower than 0.1° in the frontal plane. Even if the calibration data is not available, the accuracy remains sufficient for TKA planning. In this study, idealised 2D and 3D image information was used. In the future, this method should be tested using clinical X-ray images and 3D-US data

Background Computer navigation is increasingly being recognized as a valuable tool in restoring the mechanical axis post TKR. Its use is as yet not universal due to the costs involved, its availability and the fact that it can be cumbersome and time consuming to use. Additionally it requires the insertion of Schanz pins in the femur as well as the tibia which can be a matter of concern as regards stress fracture and infection. However, it is able to reliably locate the center of the femoral head which is an elusive landmark in the standard method. The center of the ankle involves registration for the medial and lateral malleoli which are subcutaneous and easily palpable. We decided to navigate only the distal femoral cut with a specialized navigation unit called Articular Surface Mounted navigation which does not require the insertion of additional pins through the femur or the tibia. We purposely did not use navigation for the rest of the bony cuts as all the other landmarks i.e. femoral epicondyles, tibial malleoli, and tuberosity etc are all easily palpable. This dramatically reduced the surgical time and increased its user friendliness. We are presenting our results. Aim. To analyse the radiographic results obtained with selective femoral navigation and compare with. standard navigational results from the literature. Non-navigated Knees form personal series. Materials and Methods. We have utilized the ASM navigation for distal femoral cut in 112 knees and obtained long X-rays (scanograms) and routine knee X-rays (AP, Lateral and skyline) to study the mechanical axis and component positioning. We measured the mechanical axis deviation, femoral and tibial angle on AP and lateral films and patellar tilt or subluxation on post-operative X-rays by a digital imaging programme called Image–J. (As suggested by the Knee Society roentgenographic Score). We have compared our results with other navigated series from literature and our own series of non-navigated knees. (113 knees) We also noted the surgical time to perform the operation and the occurrence of any complications. Results. Selective femoral navigation is able to restore the mechanical axis as reliably as other methods of navigation and more reliably than non-navigated knees. On an average, it adds less than 10 minutes to surgical time. Femoral angle, tibial angle patellar tilt and subluxation are similar in both navigated and non-navigated series. Navigation use was not associated with any increased complications and no complication could be ascribed to its use. Selective femoral navigation reduced the outliers in mechanical axis restoration when compared with standard femoral intrameduallry instrumentation. Discussion. Selective distal femoral navigation is a reliable tool in restoring mechanical axis post TKR. It is particularly valuable in knees that have pronounced femoral bowing

Tibial and femoral loosening are major causes for implant failure in total knee arthroplasty. Jefferey (1991) reported a significantly lower rate of loosening when varus or valgus was within 3 degrees of mechanical axis in an eight year follow up. Coulle (Dec1999) reported 48% unacceptable alignment in non-navigated knees and Reed (Aug 2002) reported 35% alignments deviating more than 3 degrees from mechanical axis when navigation was not used. We report our series of 286 navigated knee replacements using the Aesculap Search system (21 cases) and the Aesculap e-motion versions 4.2, 4.3 and 4.4 (265 cases) between April 2003 and December 2012 by the author (A.D) and analysed the correction achieved against the zero mechanical axis. Postoperative measurement of the angles on long length films was done in 23 cases. This matched with the intraoperative corrections achieved as studied using per-operative computer data stored for every case. We continued to use the data stored in the AESCULAP System to correlate the findings in the rest of the cases. The average mechanical axis achieved was 1.3 degrees. All cases had mechanical axes within 3 degrees. We were thus able to achieve a high level of correction of the mechanical axes predictable to achieve better clinical outcomes

INTRODUCTION. Recent studies indicated that the knee has a single flexion/extension axis but debated the location of this axis. The relationship of the flexion/extension axis in the coronal plane to the mechanical axis has received little attention. The purpose of this study was to investigate the relationship of the various axes and references with respect to the mechanical axis in the coronal plane. MATERIALS AND METHODS. Subjects were prospectively scanned into a Virtual Bone Database (Stryker Orthopaedics, Mahwah, NJ). Database is a collection of body CT scans from subjects collected globally. Only CT Scans that met the following qualifications were accepted: ≤1 mm voxels and had slice thickness that was equal to the spacing between the slices (≤ 1.0mm). For each CT Scan, a frontal plane was created through the 2 most posterior points of the medial/lateral condyles and the most posterior point of the trochanter. Then, a transverse plane was created perpendicular to the frontal plane and bisects the 2 most distal points on the medial/lateral condyles. Finally, a saggital plane was created that was perpendicular to the frontal and transversal planes. The following axes were identified: Mechanical Axis of the Femur (MAF) (line between the center of the femoral head and the center of the knee sulcus); Transepicondylar Axis Posterior Cylindrical Axis (PCA) (line between the Medial/Lateral Condylar Circle – best fit circle to three points identified on surface). Measurements made: Angle of MAF and the Joint-Line (Femoral Joint Angle), Angle of the MAF and the Transepicondylar Axis (Femoral TE Angle), and Angle of the MAF and the Posterior Cylindrical Axis (Femoral PC angle). Angles measuring 90° were neutral or perpendicular to the MAF. Angles measured <90° were valgus and >90° were varus. RESULTS. CT Scans from 519 knees were studied. The mean femoral joint angle was 86.1°±2.0°(Range:80.2°-92.2°). The mean TE angle was 88.8°±2.5°(Range:81.7°-98.4°). The mean Femoral PC angle was 87.9°±2.2°(Range:81.8°-94.0°). The average deviations from a neutral resection were 3.8°, 1.2° and 2.1° for the Femoral Joint Angle, Femoral TE Angle respectively. The mean Femoral Joint angle had the lowest variability, while the mean Femoral TE angle showed the largest. CONCLUSION. On average, the transepicondylar axis and the posterior cylindrical axis were approximately perpendicular to the mechanical axis in the coronal plane. Although surgeons do not align components in the coronal plane specifically to either axis, this data suggests that the average value is within the accepted ±3° range reported. The PCA values are closer to the values of the femoral joint line when compared to the TEA. The PCA may be a more reproducible landmark as it may be determined by either preoperative imaging or intraoperatively from instrumentation that references the distal/posterior surfaces. Further research is warranted

Introduction. The success of knee replacement surgery depends, in part, on restoration of the correct alignment of the leg with respect to the load-bearing vector passing from the hip to the ankle (the mechanical axis). Conventional thinking is that the correct angle of resection of the distal femur (Valgus Cut Angle, VCA) depends on femoral length or femoral offset, though femoral bowing, in addition to length and medial offset, may also have a significant influence on the VCA. We hypothesized that femoral bowing has a strong effect on the VCA necessary to restore physiologic alignment after arthroplasty or osteotomy. Methods. A total of 102 long-leg radiographs were obtained from patients scheduled for primary total knee arthroplasty. The patients on average were 41% male 59% female, 67.9 ± 11.1 years, 67.0 ± 4.7 in, 192 ± 43 lbs, and had a BMI of 29.7 ± 4.8. All radiographs were prepared with the feet placed in identical rotation and the patellae pointing forward, and were excluded if there was evidence of malrotation, as defined by (i) a difference in the medial head offsets of the right and left femur of >3mm, (ii) a difference in the width of the tibiofibular syndesmoses, or (iii) a difference in the rotation of one foot compared to the other. The following anatomic variables were measured on each radiograph: (i) the neck shaft angle (NSA) of the femur, (ii) the length of the femur, (iii) the length of the femoral shaft, (iv) the medial head offset, (v) the medial-lateral bow of the distal femur, (vi) the hip- knee axis angle, (vii) the mechanical axis deviation of the extremity at the knee, (viii) the medio-lateral bow of the tibia, and (ix) the valgus cut angle required to restore the mechanical axis to the center of the knee during surgery (VCA). Bivariate plots were constructed using the measurements thought to influence the VCA: femoral bowing, femoral offset, and length of femur. Multivariate regression was then used to find the variable that had the strongest effect on the VCA. Results. The bivariate plot of offset and VCA yielded an R2 of 0.02544 (p = 0.11) was not statistically significant. However, the bivariate plot of femoral length and VCA yielded an R2 of 0.1294 (p = 0.0002) showing significant correlation. Lastly, the bivariate plot of femoral bowing and VCA yielded an R2 of 0.59136 (p < 0.00001) demonstrating significant correlation (Figure 3). Multivariate analysis revealed that femoral bowing was the best predictor of VCA: VCA = 5.46–0.363 femoral bowing (°) + 0.106 Femoral offset (mm) − 0.010 femoral length (mm). Discussion. While clinicians performing knee replacements typically do not consider femoral bowing when selecting the valgus angle appropriate for each patient, our findings demonstrate that femoral bowing has a potent effect on VCA. The multivariate regression indicated that femoral bowing had the highest effect on VCA followed by offset and femoral length. These findings suggest that surgeons should consider measuring long alignment radiographs before performing a total knee arthroplasty

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:. 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

INTRODUCTION

Navigation systems have proved allowing performing measurement of the lower limb axis with a good accuracy, but the mandatory use of reference pins or screws limit their use to the operating room. The use of non-invasive navigation systems has been suggested to overcome this limitation. We conducted a prospective study to assess the validity of such a measurement system with non-invasive fixation of the reference arrays. The main goal was to compare this method with a standard, invasive navigation system requiring bony fixation of the arrays. The following hypothesis was tested: there will be a significant difference between the simultaneous measurement of the mechanical femoro-tibial angle by a standard navigation system and by the non-invasive navigation system.

Background. Total knee arthroplasty (TKA) was primarily considered a successful procedure, several new knee implants were introduced in recent years that seek to obtain improved stability and higher flexion. One of the implant, Vanguard XP. TM. BiCruciate retaining (BCR), Zinmmer-Biomet, USA recreates a specific kinematic model through the principle of normal joint. Patients and Method. An unselected consecutive series of sixty-two patients undergoing primary TKA using the cemented total knee system between August 2016 and April 2018 were studied. Twenty-seven knees was operated using Vanguard XP, subsequently thirty-five knees were received a TKA using cruciate retaining cemented total knee system FINE. TM. CR, Nakashimamedical, Japan. Postoperatively standing AP hip-to-ankle radiographs were obtained, from which the lower extremity mechanical axis, component angle were measured. The alignment goals were a neutral mechanical axis defined as a hip-to-ankle angle of 0°with the femoral and tibial components aligned perpendicular to the mechanical axis. The total operating time were quantified utilising an operating room database. The total operating time between TKAs performed with Vanguard XP BCR and those performed with FINE CR was compared in each group. All patients postoperatively was evaluated of clinical results the Japan Orthopedics Association(JOA) Knee scores. We evaluated femoral component posterior offset (PFCO) in both of two group. The maximal protrusion of the posterior condyle, posteriorly to the extension line parallel to the tibial shaft from the edge of the posterior tibial component was measured on true lateral radiographs. Results. The JOA Knee score of Vanguard XP BCR group was 86.5±4.7 points, and the score of FINE group was 82.7±5.9 points, there was no statistical significance between the two groups on the clinical score. The operative time in Vanguard XP BCR was 137.2±14.6 minutes and significantly more compared to the time of FINE group 111.3±11.9 minutes. The mechanical axis angle in Vanguard XP BCR group was −1.3°±2.7, while FINE CR group was −0.7°±3.2, there was no statistical significance. The number of outliers for mechanical axis angle was Vanguard XP BCR group 25%, the FINE group 24%, between the two groups there was no statistical significance. The mean value of the femoral component posterior offset ratio of Vanguard XP BCR was 14.4%±0.1. The mean value of the posterior offset ratio of FINE group was 16.7%±0.1, between the two groups there was statistical significance. Discussion. Bellemans et al. first defined the concept of posterior condylar offset. They demonstrated that the maximum active flexion possible was limited by direct impingement of the posterior aspect of the tibial component against the posterior aspect of the femur. However, the offset also reduces the extension gap. An enlarged posterior femoral component may reduce the extension gap due to posterior tissue tightness. In this study, the femoral component posterior offset ratio of Vanguard XP BCR was good results compared to the CR type FINE. Clinical results and the mechanical axis angle was good both of the group, but the operative time in Vanguard XP BCR was significantly more compared to the time of FINE group. Conclusion. Good early clinical results were obtained with Vanguard XP BCR knee implant, long-term follow-up studies are needed to confirm our findings

Introduction. To evaluate the results of correction of knee deformities based on deformity analysis in Achondroplasia, the commonest skeletal dysplasia as some have concomitant ligamentous deformities. Materials and Methods. Retrospective study from a prospective database (2007–2020) of achondroplasts who underwent growth modulation. Analysis of medical records with objective measurement of mechanical axis radiographs was done (Traumacad). Satisfactory alignment was defined as neutral to slightly varus (0–15 mm MAD) so that the MCL/LCL laxity is not revealed. Results. 23 patients, 41 limbs, 34 bilateral, 6 unilateral underwent multiple growth modulation procedures. 2 had valgus knees. 15 patients underwent proximal fibular epiphysiodesis in addition for LCL laxity with one isolated fibular epiphysiodesis. Mechanical axis deviation (MAD) improved or normalised in 16 patients (70%). 4 patients were still undergoing correction. 4 patients needed further surgery out of which 2 patients were over 13 years when growth modulation was attempted and 2 needed correction of ankle varus. JLCA improved/ normalised in 12 patients (75%) with evidence of indirect LCL tightening and no improvement was seen in 4. The rate of correction was MAD 0.61mm/month, LDFA 0.29°/month and MPTA 0.13°/month; expectedly lower in achondroplasia due to lower growth velocity. Conclusions. This study highlights the pathology, application of growth modulation as per deformity analysis unlike previous studies. Proximal fibular epiphysiodesis improves LCL laxity in a majority of these children and is a simple procedure compared to our published series with indirect LCL tightening with frames

Introduction. Neutral mechanical alignment in TKA has been shown to be an important consideration for survivorship, wear, and aseptic loosening. However, native knee anatomy is described by a joint line in 3° of varus, 2–3° of mechanical distal femoral valgus, and 2–3° of proximal tibia varus. Described kinematic planning methods replicate native joint alignment in extension without changing tibiofemoral alignment, but do not account for native alignment through a range of motion. An asymmetric TKA femoral component with a thicker medial femoral condyle and posterior condylar internal rotation paired with an asymmetric polyethylene insert aligns the joint line in 3° of varus while maintaining distal femoral and proximal tibial cuts perpendicular to mechanical axis. The asymmetric components recreate an anatomic varus joint line while avoiding tibiofemoral malalignment or femoral component internal rotation, a risk factor for patellofemoral maltracking. The study seeks to determine how many patients would be candidates for a kinematically planned knee without violating the principle of a neutral mechanical axis (0° ± 3°). Methods. A cohort comprised of 55 consecutive preoperative THA patients with asymptomatic knees and 55 consecutive preoperative primary unilateral TKA patients underwent simultaneous biplanar radiographic imaging. Full length coronal images from the thoracolumbar junction to the ankles were measured by two independent observers for the following: mechanical tibiofemoral angle (mTFA), mechanical lateral distal femoral angle (mLDFA), and mechanical medial proximal tibial angle (mMPTA). Patients who met the following conditions: mTFA 0°±3°; mLDFA 87°±3°; and mMPTA 87°±3°, were considered candidates for TKA with an asymmetric implant that would achieve a kinematic joint line and neutral mechanical axis. Similarly, patients with the following conditions: mTFA 0°±3°; mLDFA 90°±3°; and mMPTA 90°±3°, were considered candidates for TKA with a symmetric implant that would achieve a kinematic joint line and neutral mechanical axis. Results. In this cohort of 110 patients, the mean mTFA was 1° varus ± 5°, the mean mLDFA was 87° ± 3°, mMPTA 87°± 2°. The comparison of patients meeting each of the three conditions required for a TKA with a neutral mechanical axis and a kinematic joint line are outlined in Table 1. Conclusion. A TKA with kinematic 3° varus joint line and neutral mechanical axis was possible in 52% of patients using an asymmetric implant and 23% of patients using a symmetric implant. Previous descriptions of kinematic planning using standard TKA components required compromise of neutral mechanical axis alignment with detrimental effects on overall survivorship. Knee arthroplasty using an asymmetric implant may achieve the best of both worlds, neutral mechanical axis and a kinematic joint line, in a large percentage of patients

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. Intramedullary lengthening devices have been in use in older children with closed /open growth plates with good success. This study aims to present the early experience of the FITBONE nail since withdrawal of the PRECICE nail. Materials & Methods. Retrospective analysis of both antegrade and retrograde techniques were utilized. Only patients where union was achieved and full weight bearing commenced were included. The complication rate, length gained, distraction index, weight bearing index (WBI) as well as mechanical axes were analysed. Results. 14 (7 males, 7 females) of a total of 16 (7 males, 7 females) patients with a mean age of 16.9 years with varied diagnosis of LLD were analysed. The mean length gained was 38 mm with an average distraction index of 0,74 mm/day. WBI in these patients on average was 59,6 days/cm lengthened. 6 complications were observed, including two nonunions (successfully treated) and a knee subluxation. Mechanical axis deviation improved from 13,3 mm to 6 mm on average. Overall there has been a nonsignificant tendency for WBI to decrease (Spearman's rank correlation coefficient −0.47, p=0.08) with increasing number of cases done, while no correlation between length gained and WBI (−0.01, p=0.96, respectively) was observed. Some nuances will be discussed. Conclusions. Limb lengthening with the FITBONE nail is relatively safe and efficient, however no significant change was seen in the outcome with previous motorized nails

Introduction. The practice of limb lengthening using intramedullary nails has surged in popularity in recent years. Our study explores the relationship between femur lengthening and overall height gain in adults undergoing cosmetic limb lengthening with telescoping magnetic intramedullary lengthening nails (MILNs). Materials & Methods. Demographic information, pre- and postoperative radiographic data, and secondary outcomes, such as mechanical angles and sagittal alignment, were analyzed for 42 adult femurs MILNs (PRECICE 2, NuVasive, Inc.). Height was assessed with a digital stadiometer. Limb lengthening was defined as the amount of nail distraction seen on a calibrated weight bearing X-ray at consolidation. mLDFA, mMPTA, MAD, AMA, and femoral sagittal bow were evaluated as secondary outcomes. Results. Mean starting height was 163.5 cm (SD 10.4, range 137–179) Post -lengthening mean height increased to 171.1 cm (SD 10.1, range 146.7–185.3). Average height gain was 7.5 cm (SD 1.3 cm, range 5.1–9.5). Average femoral lengthening was 7.3 cm (SD 1.14, range 4.1–10.1). There were no statistically significant difference between height gain and femur lengthening. Secondary outcomes showed reductions in femoral sagittal bow and AMA. Conclusions. We conclude that measuring femur lengthening is a reliable and accurate method of measuring gained height in deformity-free patients undergoing limb lengthening. We further reason that straightening of both femoral and spinal sagittal bow counteracts potential lengthening loss over the anatomical axis, versus mechanical axis lengthening

Background. Variability in component alignment continues to be a major in total knee arthroplasty(TKA). In the long term, coronal plane malalignment has been associated with an increased risk of loosening, insatability, and wear. Recently portable navigation system(PNS) in TKA have been introduced. The goal of PNS are to improve the accuracy of post operative alignment and eliminate outlier cases. The aim of this study is to evaluate clinical results and quantify the coronal plane alignment between a group of patients who underwent TKA using PNS versus CT-free large-console navigation system. Patients and Method. An unselected consecutive series of ninety-four patients undergoing primary TKA using the cruciate retaining cemented total knee system between April 2012 and August 2015 were studied. Patients were included only if they were deemed to be candidates for a Cruciate retaining TKA. Patients were excluded if they had a flexion contracture greater than 40°, or severe valgus or varus deformity. Forty eight knees was operated a TKA with CT-free large-console navigation system(The OrthoPilot system; Aesculap, Tuttlingen, Germany). Subsequently forty six knees was received a TKA using portable navigation system (KneeAlign2. TM. ). Postoperatively standing AP hip-to-ankle radiographs were obtained, from which the lower extremity mechanical axis, component angle were measured. The alignment goals were a neutral mechanical axis defined as a hip-to-ankle angle of 0°with the femoral and tibial components aligned perpendicular to the mechanical axis. The total operating time were quantified utilising an operating room database. The total operating time between TKAs performed with CT-free navigation system and those performed with portable navigation system was compared in each group. All patients postoperatively was evaluated of clinical results the Japan Orthopedics Association(JOA) Knee scores. Results. The mechanical axis angle in PNS group was 0.8°, while the CT-free navigation system group was 1.6°and there was no statistical significance. The number of outliers for mechanical axis angle was PNS group 39.1%, the large-console navigation group 22.9%, between the two groups there was statistical significance. The operative time in PNS was 130.0 minutes and significantly less compared to the time of the large-console group 150.4 minutes. The JOA Knee score of navigation group was 83.9 points, and the score of PNS group was 81.0 points., there was no statistical significance between the two groups on the clinical score. Conclusion. portable navigation system improved operative time in TKA, this study demonstrates portable navigation system to obtain same angle of overall mechanical axis angle as large-console group navigation system

The emergence of patient specific instrumentation has seen an expansion from simple radiographs to plan total knee arthroplasty (TKA) with modern systems using computed tomography (CT) or magnetic resonance imaging scans. Concerns have emerged regarding accuracy of these non-weight bearing modalities to assess true mechanical axis. The aim of our study was to compare coronal alignment on full length standing AP imaging generated by the EOS acquisition system with the CT coronal scout image. Eligible patients underwent unilateral or bilateral primary TKA for osteoarthritis under the care of investigating surgeon between 2017 and 2022, with both EOS X-Ray Imaging Acquisition System and CT scans performed preoperatively. Coronal mechanical alignment was measured on the supine coronal scout CT scan and the standing HKA EOS. Pre-operative lower limb coronal alignment was assessed on 96 knees prior to TKA on the supine coronal scout CT scan and the standing HKA EOS. There were 56 males (56%), and 44 right knees (44%). The mean age was 68 years (range 53-90). The mean coronal alignment was 4.7 degrees (SD 5.3) on CT scan and 4.6 degrees (SD 6.2) on EOS (p=0.70). There was a strong positive correlation of coronal alignment on CT scan and EOS (pearson. 0.927, p=0.001). The mean difference between EOS and CT scan was 0.9 degrees (SD 2.4). Less than 3 degrees variation between measures was observed in 87% of knees. On linear regression for every 1° varus increase in CT HKA alignment, the EOS HKA alignment increased by 0.93° in varus orientation. The model explained 86% of the variability. CT demonstrates excellent reliability for assessing coronal lower limb alignment compared to EOS in osteoarthritic knees. This supports the routine use of CT to plan TKA without further weight bearing imaging in routine cases

A primary goal of revision Total Knee Arthroplasty (rTKA) is restoration of the Joint Line (JL) and Posterior Condylar Offsets (PCO). The presence of a native contralateral joint allows JL and PCO to be inferred in a way that could account for patient-specific anatomical variations more accurately than current techniques. This study assesses bilateral distal femoral symmetry in the context of defining targets for restoration of JL and PCO in rTKA. 566 pre-operative CTs for bilateral TKAs were segmented and landmarked by two engineers. Landmarks were taken on both femurs at the medial and lateral epicondyles, distal and posterior condyles and hip and femoral centres. These landmarks were used to calculate the distal and posterior offsets on the medial and lateral sides (MDO, MPO, LDO, LPO respectively), the lateral distal femoral angle (LDFA), TEA to PCA angle (TEAtoPCA) and anatomic to mechanical axis angle (AAtoMA). Mean bilateral differences in these measures were calculated and cases were categorised according to the amount of asymmetry. The database analysed included 54.9% (311) females with a mean population age of 68.8 (±7.8) years. The mean bilateral difference for each measure was: LDFA 1.4° (±1.0), TEAtoPCA 1.3° (±0.9), AAtoMA 0.5° (±0.5), MDO 1.4mm (±1.1), MPO 1.0mm (±0.8). The categorisation of asymmetry for each measure was: LDFA had 39.9% of cases with <1° bilateral difference and 92.4% with <3° bilateral difference, TEAtoPCA had 45.8% <1° and 96.6% <3°, AAtoMA had 85.7% <1° and 99.8% <3°, MDO had 46.2% <1mm and 90.3% <3mm, MPO had 57.0% <1mm and 97.9% <3mm. This study presents evidence supporting bilateral distal femoral symmetry. Using the contralateral anatomy to obtain estimates for JL and PCO in rTKA may result in improvements in intraoperative accuracy compared to current techniques and a more patient specific solution to operative planning

Inverse Kinematic Alignment (iKA) and Gap Balancing (GB) aim to achieve a balanced TKA via component alignment. However, iKA aims to recreate the native joint line versus resecting the tibia perpendicular to the mechanical axis. This study aims to compare how two alignment methods impact 1) gap balance and laxity throughout flexion and 2) the coronal plane alignment of the knee (CPAK). Two surgeons performed 75 robotic assisted iKA TKA's using a cruciate retaining implant. An anatomic tibial resection restored the native joint line. A digital joint tensioner measured laxity throughout flexion prior to femoral resection. Femoral component position was adjusted using predictive planning to optimize balance. After femoral resection, final joint laxity was collected. Planned GB (pGB) was simulated for all cases posthoc using a neutral tibial resection and adjusting femoral position to optimize balance. Differences in ML balance, laxity, and CPAK were compared between planned iKA (piKA) and pGB. ML balance and laxity were also compared between piKA and final (fiKA). piKA and pGB had similar ML balance and laxity, with mean differences <0.4mm. piKA more closely replicated native MPTA (Native=86.9±2.8°, piKA=87.8±1.8°, pGB=90±0°) and native LDFA (Native=87.5±2.7°, piKA=88.9±3°, pGB=90.8±3.5°). piKA planned for a more native CPAK distribution, with the most common types being II (22.7%), I (20%), III (18.7%), IV (18.7%) and V (18.7%). Most pGB knees were type V (28.4%), VII (37.8%), and III (16.2). fiKA and piKA had similar ML balance and laxity, however fiKA was more variable in midflexion and flexion (p<0.01). Although ML balance and laxity were similar between piKA and pGB, piKA better restored native joint line and CPAK type. The bulk of pGB knees were moved into types V, VII, and III due to the neutral tibial cut. Surgeons should be cognizant of how these differing alignment strategies affect knee phenotype