Background: Navigation allows for determination of the mechanical axis of the lower extremity. We evaluated the intra- and inter-observer reliability with an image-free navigation system and determined the accuracy of the navigation system to monitor changes in lower limb alignment as compared to alignment measured with a novel 3D CT method.

Methods: A total of 13 cadaver legs were used to evaluate the intra- and inter-observer registration reliability by three observers. Navigated HTOs were then performed on all legs and pre/postoperative values of the varus-valgus angles were recorded. Data were compared to equivalent measures obtained by 3D CT using intra-class correlation coefficients (ICCs).

Results: The ICCs for intra-observer varus-valgus reliability ranged from 0.756 to 0.922, inter-observer reliability was 0.644. ICCs for navigation-CT comparison were 0.784 for varus-valgus angle (pre-op), 0.846 (postop) and 0.873 (delta). Maximum differences in navigation-CT measurements in varus-valgus angle (delta) were 4.5° for all trials. There was poor reliability and accuracy in the axial plane (tibial rotation) as well as fair reliability and accuracy in the sagittal plane (tibial slope).

Conclusion: Image-free navigation is reliable for dynamic monitoring of coronal leg alignment but shows relevant limitations in determination of sagittal and axial plane alignment.

Aims

The aim of this study was to determine the association between knee alignment and the vertical orientation of the femoral neck in relation to the floor. This could be clinically important because changes of femoral neck orientation might alter chondral joint contact zones and joint reaction forces, potentially inducing problems like pain in pre-existing chondral degeneration. Further, the femoral neck orientation influences the ischiofemoral space and a small ischiofemoral distance can lead to impingement. We hypothesized that a valgus knee alignment is associated with a more vertical orientation of the femoral neck in standing position, compared to a varus knee. We further hypothesized that realignment surgery around the knee alters the vertical orientation of the femoral neck.

The radiologic and clinical results of High Tibial Osteotomies (HTO) strongly rely on the accuracy of correction, and inadequate intraoperative measurements of the leg axis can lead to over or under- correction. Over the past few years, navigation systems have been proven that navigation systems provide reliable real-time intro-operative information, may increase accuracy, and improves the precision of orthopaedic surgeries. We assessed the radiological and clinical results of navigation- assisted open wedge HTO versus conventional HTO at 24 months after surgery. A total of sixty-five open wedge HTOs were performed using navigation system and compared with forty-six open HTOs that had been performed using the conventional cable technique in terms of intraoperative leg axis assess. The Orthopilot navigation system (HTO version 1.3, B. Braun Aesculap, Tuttligen, Germany) used throughout the procedure of navigated open wedge HTO. The aim of the correction was to achieve of 3°of valgus (2–4°) on both method. For the radiological evaluation, postoperative leg axes were examined using weight bearing full-leg radiography obtained at postoperative two years after surgery. To assess correction accuracies, we compared mechanical tibiofemoral angles and intersections of the mechanical axis of the tibial plateau (%) in both groups. Outliers were defined as under-corrections of < 2° of valgus and as over-corrections of > 5° of valgus. The posterior slope of the proximal tibia was measured using the proximal tibial anatomical axis (PTAA) method. HSS (Hospital for Special Surgery) scores and ROMs (ranges of motion) were evaluated and all complications were recorded and surgical and radiation times were measured. Navigated HTOs corrected mechanical axes to 2.8° valgus (range −3.1∼5.3) with few outliers (9.5%), and maintained posterior slopes (8.5±2.3° preoperatively and 11.0±2.8° postoperatively) (P>0.05). In the conventional group, the mean valgus correction was satisfactory (2.2° valgus), but only 67.4% were within the required range (2∼5° valgus), and 26.1% of cases were under-corrected and 6.5% of cases were over-corrected. Posterior slope increased from 8.0° to 10.6° on average without significant change after surgery. Total fluoroscopic radiation time during navigated HTO was 8.1 seconds (5∼12s) as compared with 46.2 seconds (28∼64 s) during conventional HTO (p<0.05). The surgery time for navigated HTO was 11.2 minutes longer than for conventional HTO (55.5 minutes). No specific complications related to the navigation were encountered. At clinical follow up, mean HSS scores of the navigated HTO and conventional groups improved to 91.8 and 92.5 from preoperative values of 55.3 and 55.9, respectively (p>0.05), and all patients achieved full ROM. Navigation for HTO significantly improved the accuracy of postoperative leg axis, and decreased the variability of correction with fewer outliers, and without any complications. Moreover, it allows multi-plane measurements to be made, in the sagittal and transverse planes as well as the frontal plane intra-operatively in real time, compensates to some extent for preoperative planning shortcomings based on radiography, and significantly reduces radiation time

Introduction Correct postoperative leg alignment and stability of total knee prothesis over the full range of movement is one critical factor for successful TKA. This can only be achieved by correct implantation of prothesis and soft tissue handling. Still arthrotomy, surgical approach and handling of patella are discussed controversially. Materials and Methods In a cadaver specimen study we evaluated the influence of everted or subluxated patella on limb axis during balancing of the knee in three different standard surgical approaches. For each approach we operated five knees. Leg alignment was visualised by Ci CT-free DePuy/BrainLAB navigation system. First, physiological leg alignment was measured. Then the different approaches were performed and a.p. leg axis was first measured and compared as well with everted as with subluxed patella in extension and second in 90 degrees flexion. Results Eversion of patella leads to an alteration in leg axis compared to subluxed patella of 0.58 degrees (SD: 0.03, range: 0.54–0.6) limb axis in valgus direction in full extension. In 90 degrees flexion we found a mean deviation of leg axis of 0.48 degrees (SD: 0.11, range: 0.38–0.6) with everted patella compared to subluxed patella. Discussion The surgeon has to be aware of this falsifying influence of everted patella to the a.p. limb axis

Introduction: High tibial osteotomy is a recognised method of treatment for malalignment and osteoarthritis in young patients. Today computer aided surgery provides a chance to improve the existing techniques with a traceable planning and a higher degree of accuracy. Intraoperative use of fluoroscopy can be reduced and the results regarding leg axis can be improved. Method: In our department since two years nearly all patients with malalignment of the lower legs had osteotomies guided with a navigation system. We used the Medivison-Praxim system in five, the Orthopilot prototype software in 12 and the Brain LAB System in 15 patients. The most common operation type was an open wedge osteotomy of the proximal tibia. A single cut osteotomy to correct the torsion and valgus deformity after a distal femur fracture is also possible with the Brain LAB system. Stabilisation was achieved using a plate with head locking screws (Tomofix, Synthes). The degree of correction was controlled during the operation with the navigation system and compared with pre- and postoperative 2.5D ultrasound measurements to avoid projection errors of long standing x-rays. Results: In all cases the intraoperative analysis was possible with the navigation systems. In one case, the computer crashed down due to interference of the fluoroscopy machine. No surgical problems were noted due to computer guidance noted. Fluoroscopy was used in all cases to verify the implant position as well as the resection plane after inserting the k-wires for saw blade guidance. The additional time for navigation was about 15 minutes. The postoperative 2.5D ultrasound leg axis analysis showed a maximum of +/− 2° difference between the pre-, intra- and postoperative measurements. Discussion: The chance to track the patient’s leg geometry through the complete procedure until bone fixation is the main benefit of computer assistance. The chance of failure during reduction and fixation can also be minimised and potential misalignment can be improved immediately. In addition, like in navigated joint replacement, the result of the surgical treatment can be simulated and judged before any action; values can be influenced showing the consequence right away. The final result regarding the leg axis is determined not only by the computer guidance, but by the primary stability of the implant as well. The chosen Tomofix plate is supposed to provide highest initial stability. This first results show a promising increase of accuracy while radiation can be reduced. The actual values show that the main goal to increase the intraoperative accuracy in corrective osteotomies can be achieved with computer aided surgery

Introduction: Minimal-invasive techniques in total joint replacement are perceived to reduce soft tissue trauma. In TKR, reduced exposure during surgery bares the risk of component malpositioning. Therefore we have combined minimal invasive surgical techniques with non-CT based navigation in TKR. The purpose of this observational study is to describe first results of a controlled observational study comparing minimal invasive navigated total knee arthroplasty (MINI-NAV-TKR) to open navigated total knee arthroplasty (NAV-TKR) with respect to component positioning, surgery time and immediate postoperative complications. Materials and Methods: From June to September 2004, 26 MINI-NAV-TKR and 33 NAV-TKR have been performed by five surgeons in an unselected group of patients. In both groups, preoperative deformation of the mechanical leg axis was compared to postoperative mechanical leg axis using total one-leg standing radiographs. To control the safety and reproducibility of both procedures, time of surgery and postoperative complications were compared among both groups. Results: Given informed consent, 17 females and 9 males received 26 MINI-NAV-TKR, mean age was 71,06 years (ranging from 56,24 years to 84, 35 years), mean BMI was 28,8 kg/m2 and preoperative mechanical leg axis ranged from 18o varus to 16 o valgus. In NAV-TKR group, 12 males and 21 females at a mean age of 68,75 (range 51,97 to 86,73 years) received 33 TKR, mean BMI was 30,6 kg/m2 and preoperative mechanical axis ranged from 11 varus to 20 valgus. Postoperative radiographic leg alignment in the MINI-NAV-TKR group ranged from 1 degree valgus to 3 degree varus mechanical axis as compared to the NAV-TKR that ranged from 1 valgus to one outlayer of 4 degree varus. Time of surgery significantly differed among the groups (mean time Mini-NAV-TKR 115,23 min versus mean time NAV-TKR 98,15 minutes, p=0,002). In the MINI-NAV-TKR group 1 postoperative pin-infection and one conversion to an open procedure have been reported, in the NAV-TKR group 2 hematomas have been described. Conclusion: Despite increased mean time of surgery in the MINI-NAV-TKR group, component positioning and complications are comparable between both groups. These preliminary results indicate, that MINI-NAV-TKR combined with navigation is a safe and reproducible method

Long term successful results of high tibial osteotomy (HTO) strongly depend on the degree of correction, and inadequate intraoperative measurements of the leg axis can lead to under or over correction, and surgeons have to solve these problems based on personal experience. This study was undertaken to investigate and compare the clinical and radiological results of navigation assisted open wedge high tibial osteotomy (HTO) versus conventional HTO at 12 months after surgery, for unicompartmental gonarthrosis. Forty navigated open HTOs with an anterior opening gap of approximately 70% of the posterior gap were included and compared with forty open HTOs performed using the conventional cable technique in terms of intraoperative leg axis assess. Navigated HTOs corrected mechanical axes to 2.9° valgus (range 0.5–6.2) with few outliers (12.5%), and maintained posterior slopes (7.9±2.3° preoperatively and 8.3±2.8° postoperatively) (P> 0.05). However, in the conventional group, only 63% of cases were within the satisfactory range (valgus 2–5°), and tendencies toward undercorrection and an increase in posterior slope were observed. Clinically both groups showed satisfactory results. Navigated HTO significantly improved the accuracy of postoperative mechanical axis and decreased correction variabilities with fewer outliers

The accuracy of component implantation is an important factor affecting long term results of unicompartmental knee replacement (UKR), particularly, since overcorrection of the leg axis has been associated with an inferior patients outcome. This problem is aggravated when using a minimally invasive approach with a limited view. In a prospective study, two groups of 40 UKR each were operated either using a non-image-based navigation system or the conventional technique. Radiographic assessment of postoperative alignment was performed by postoperative long-leg coronal and lateral x-rays. The results revealed a significant difference between the two groups in favour of navigation with regard to the mechanical axis, as well as the coronal femoral and tibial alignment. In the computer assisted group 38/40 (95%) of UKR were in a range of 4 Degree to 0 degree varus (mechanical axis) compared with 29/40 (72,5%) in the conventional group. There was no significant difference between the groups concerning postoperative range of motion, blood loss and pain score. The only inconvenience was a lengthening of the operation time (20 min). Due to the limited exposure in minimal invasive unicompartmental TKA the navigation system is helpful in achieving a more precise component orientation. The danger of overcorrection is diminished by real time information about the leg axis at each step during the operation. This improvement could be related to a longer survival rate

Introduction: There is an ongoing discussion about potential risks and benefits of minimally invasive approaches (MIS) in total joint replacement. The aim of this study was to evaluate, whether a higher incidence of malalignments could be observed after minimally invasive navigated TKA and wether the results in the early postoperative period were better compared to standard approaches. Methods: A total of 50 patients were treated with a navigated (OrthoPilot 4.2) Columbus knee prosthesis (BBraun Aesculap, Germany). In 25 patients either a standard or a minimally invasive (mini-mid-vastus) approach was carried out. In both groups the same exclusion criteria for MIS were adopted. Initially during surgery (Nav1a) and finally after implantation of the original components (Nav1b) the mechanical leg axis, passive range of motion and stability were measured by navigation according to the common workflow of the system. After restarting the software the same parameters were evaluated once more in a second procedure (Nav2) by reacquisition of joint centers both kinematically and by anatomical landmark palpation with the original prosthesis already implanted. Nav2 was conducted independantly from the initial surgical procedure. To validate the intraoperative measurements additional pre- and postoperative long-leg-standing radiographs were made. During the the first 10 days postoperatively daily range of motion (ROM) and pain (VAS) were measured. Perioperative blood loss and complications were documented. Results were analyzed by student’s t-test. Results: Both groups were comparable with regard to preoperative demografic, radiologic and intraoperative data (Nav1a). There were no significant differences between the groups concerning intraoperative measurements of mechanical leg axis, passive range of motion and stability by Nav1b and Nav2. Additionally no differences were found for the alignment in the postoperative radiographs. The length of the skin incisions were significantly shorter in the minimally invasive group. Postoperative ROM was significantly higher and pain was significantly less intensive in the MIS group. Blood loss and complication rates were comparable. Discussion: If the exclusion criteria for MIS were accepted no differences regarding the quality of alignment, passive range of motion and ligament stability could be demonstrated between conventional and MIS navigated TKA. Patients with MIS navigated TKA performed superior in terms of early p.o. function and pain. From the authors point of view the technically demanding minimally invasive implantation of knee prostheses should be exclusively performed with support of navigation

Introduction: There is an ongoing discussion about potential risks and benefits of minimally invasive approaches (MIS) in total joint replacement. The aim of this study was to evaluate, whether a higher incidence of misalignments could be observed after minimally invasive navigated TKA and whether the results in the early postoperative period were better compared to standard approaches. Methods: A total of 50 patients were treated with a navigated (OrthoPilot 4.2) Columbus knee prosthesis (BBraun Aesculap, Tuttlingen, Germany). In 25 patients either a standard or a minimally invasive (mini-mid-vastus) approach was carried out. In both groups the same exclusion criteria for MIS were adopted. Initially during surgery (Nav1a) and finally after implantation of the original components (Nav1b) the mechanical leg axis, passive range of motion and stability were measured by navigation according the common workflow of the system. After restarting the software the same parameters were evaluated once more in a second procedure (Nav2) by reacquisition of joint centres both kinematically and by anatomical landmark palpation with the original prosthesis already implanted. Nav2 was conducted independently from the initial surgical procedure. To validate the intraoperative measurements additional pre- and postoperative long-leg-standing radiographs were made. During the first 10 days postoperatively daily range of motion (ROM) and pain (VAS) were measured. Perioperative blood loss and complications were documented. Results were analyzed by student’s t-test. Results: Both groups were comparable with regards to preoperative demographic, radiological and intraoperative data (Nav1a). There were no significant differences between the groups concerning intraoperative measurements of mechanical leg axis, passive range of motion and stability by Nav1b and Nav2. Additionally no differences were found for the alignment in the postoperative radiographs. The length of the skin incision was significantly shorter in the minimally invasive group. Postoperative ROM was significantly higher and pain was significantly less intensive in the MIS group. Blood loss and complication rates were comparable. Discussion: If the exclusion criteria for MIS were accepted no differences regarding the quality of alignment, passive range of motion and ligament stability could be demonstrated between conventional and MIS navigated TKA. Patients with MIS navigated TKA performed superior in terms of early postoperative function and pain. From the authors point of view the technically demanding minimally invasive implantation of the knee prosthesis should be exclusively performed with support of navigation

Introduction. Recent studies have challenged the concept that a single ‘correct’ alignment to standardised anatomical references is the primary driver of TKA performance with regards to patient satisfaction outcomes. Patient specific variations in musculoskeletal anatomy are one explanation for this. Virtual simulated environments such as rigid body modelling allow for the impact of component alignment and variable patient specific musculoskeletal anatomy to be studied simultaneously. This study aims to determine if the output kinematics derived from consideration of both postoperative component alignment and patient specific musculoskeletal modelling has predictive potential of Patient Reported Outcomes. Method. Landmarking of key anatomical points and 3D registration of implants was performed on 96 segmented post-operative CT scans of TKAs. Both femoral and tibia implant components were registered. Acadaver rig validated platform for generating patient specific rigid body musculoskeletal models was used to assess the resultant motions and contact forces through a 0 to 140 degree deep knee bend cycle. Resultant kinematics were segmented and tested for differentiation with and correlation to a 12 month postoperative Knee injury and Osteoarthritis Outcome Score (KOOS). Results. Significant negative correlations (p<0.05) were found between the postoperative KOOS symptoms score and the rollback occurring in midflexion, quadriceps force in mid flexion, patella shear force and patella tilt at 90 degrees of flexion. A significant positive correlation was found between lateral shit of the patella through flexion and the symptoms score. (p<0.05) When segmenting those KOOS scores performing in the lowest 20% of patients, both rollback and the three patella measurements have statistically significantly different means (t test, p<0.05). There were other trends present that are discernible but do not have linear correlations, as they are cross-dependant on other kinematic factors or are not linear in nature. When segmenting the varus/valgus angular change into those with a varus angular change from extension to full flexion between 0 and 4 degrees (long leg axis, not implant to implant) and those with either further varus change or a valgus change, a statistically significant difference of 7 points (p<0.05) in the postoperative KOOS pain score is observed. Likewise, measured rollback of no more than 6mm without roll forward scored 10 points higher (p<0.05) in the postoperative KOOS score. These two parameters form a ‘kinematic safe zone' of outcomes in which the postoperative KOOS score is 12 points higher (p<0.05). Conclusions. The study showed statistically significant correlations between kinematic factors in a simulation of postoperative TKA and post-operative KOOS scores. The kinematic factors so captured are the result of both the variation in implant position and the subject specific, variable musculoskeletal anatomy. The presence of a ‘kinematic safe zone' in the data suggests a subject specific optimisation target for any given individual patient and the opportunity to preoperatively determine a subject specific implant position target

Aim: Preliminary results and complications of AGC Total knee Arthroplasty with early results are presented. Materials and Methods: 51 AGC Total Knee Arthroplasties were undertaken between October 2005 and September 2006. There were 22 males and 28 females. Indication for Total Knee Arthroplasty was Primary and Traumatic Osteoarthris. Brain Lab Implant dedicated Navigation was used. Results: Outliers were significantly reduced. Complications including superficial infection, late rehabilitation, and stiffness are reported. No revision was undertaken. Tips and pearls regarding navigated Arthroplasty with reference to learning curve are discussed. Discussion: Each navigation system type has its advantages and disadvantages and can be used with minimally invasive surgery (MIS) total knee arthroplasty (TKA). In addition, concerns for computer glitches, training of personnel, extra time requirements, cost and ability to demonstrate improvements in technique and results are discussed. Conclusions: Navigated Knee Arthroplasty using AGC-Biomet implant is recommended. Early experience is reported. Salient features of early learning curve are discussed. The current paper shows how the anatomic approach can influence soft tissue tension and support the surgeon during release of soft tissues in leg axis deformities

Soft tissue management is a critical factor in total knee arthroplasty especially in valgus knees. The stepwise release has been based upon surgeon’s experience until now. Computer assisted surgery gained increasing scientific interest in recent times and allows the intraoperative measurement of leg axis and gap size in extension and flexion. We therefore aimed to analyse the effect of the sequential lateral soft tissue release and the resulting change in the a.p. limb axis on the one hand and the tibiofemoral gaps on the other hand as well in extension as in flexion in 8 cadaveric knees. Measurements were obtained using a CT-free navigation system. In extension the highest increase compared to the previous release step was found for the first (iliotibial band, p=0.002), second (popliteus muscle, p=0.0003), third (LCL, 0.007) and the sixth (entire PCL, p=0.001) release step. In 90° flexion all differences of the lateral release steps were statistically significant (p< 0.004). Massive progression of the lateral gap in flexion was found after the second (popliteus muscle, p=0.004) and third (LCL, 0.007) release step. Computer assisted surgery allows to measure the effect of each release step of the sequential lateral release sequence and helps the surgeon to asses the result better

Revision total knee replacement (TKR) is a challenging procedure, especially because most of the standard bony and ligamentous landmarks used during primary TKR are lost due to the index implantation. One might also assume that the conventional instruments, which rely on visual or anatomical alignments or intra-or extramedullary rods, are associated with significant higher variation of the leg axis correction, especially in cases with significant bone loss which prevents to control the exact location of the usual, relevant landmarks. Navigation system might address this issue. We are using an image-free system (ORTHOPILOT TM, AESCULAP, FRG) for routine implantation of primary TKR. The standard software was used for revision TKR. Registration of anatomic and cinematic data was performed with the index implant left in place. The components were then removed. New bone cuts as necessary were performed under the control of the navigation system. The size of the implants and their thickness was chosen after simulation of the residual laxities, and ligament balance was adapted to the simulation results. The system did not allow navigation for intramedullary stem extensions and any bone filling which may have been required. 60 navigated cases were compared with 30 conventional cases. We observed a significant improvement of all radiological items by navigated cases. Limb alignment was restored in 88% of the navigated cases and 73% of the conventional cases. The coronal orientation of the femoral component was acceptable in 92% of the navigated cases and 81% of the conventional cases. The coronal orientation of the tibial component was acceptable in 89% of the navigated cases and 73% of the conventional cases. The sagittal orientation of the tibial component was acceptable in 87% of the navigated cases and 71% of the conventional cases. Overall, 78% of the implants were oriented satisfactorily for the four criteria for navigated cases, and only 58% for conventional cases. The navigation system enables reaching the implantation goals for implant position in the large majority of cases, with a rate similar to that obtained for primary TKA. The rate of optimally implanted prosthesis was significantly higher with navigation than with conventional technique. The navigation system is a useful aid for these often difficult operations, where the visual information is often misleading

Computer based navigation system improved the accuracy of limb and component alignment and decreased the incidence of outliers. The majority of previous studies were based on the infrared navigation system. We evaluate the availability and accuracy of the electromagnectic(EM) navigation system in total knee arthroplasty. From July 2006 to January 2007, 40 patients (50 TKAs) with osteoarthritis were participated in this study. AxiEM(Medtronics) was used and Nexgen CR(26 cases), and Nexgen CR flex(24 cases) were used. We analyzed the failure mode of navigation (7 cases), operation time and radiologic results (limb and component alignment). Total registration time was 4 minutes 45 seconds in average (Range: 3 minutes 45 seconds – 6 minutes 55 seconds). Failures in clinical applications resulted from non-recognition of EM tracker or paddle by metallic interference in 4 cases and from informational changes during surgery by fixation loss or loosening of the tracker in 3 cases. Radiologically, the mechanical axis changed from −11.2±7.21 (Range: −25.8~3.1) to 1.0±1.25(Range: −2.1~4.0) and 1 case of outlier occurred (valgus 4°). Component alignment is measured as followed: 89.3±1.6° of Theta angle, 89.9±1.5° of Beta angle, 1.8±2.5° of Gamma angle, 86.1±2.9 of Delta angle°. There were no complications related to the EM navigation. The EM navigation system helped to achieve accurate alignment of component and lower leg axis without any complications. It had several advantages such as relatively less invasiveness in fitting small instruments, not disturbing operation field, no interrupted line of sight, portable use, and applicability to any implant. However, metallic interference may be still problematic. The EM navigation had advantages; less invasiveness, no disturbing operation field, no interrupted line of sight, portable use and applicability to any implants. But metallic interference may be still problematic

Revision TKR is a challenging procedure, especially because most of the standard bony and ligamentous landmarks are lost due to the primary implantation. However, as for primary TKR, restoration of the joint line, adequate limb axis correction and ligamentous stability are considered critical for the short- and long-term outcome of revision TKR. There is no available data about the range of tolerable leg alignment after revision TKR. However, it is logical to assume that the same range than after primary TKR might be accepted, that is ± 3° off the neutral alignment. One might also assume that the conventional instruments, which rely on visual or anatomical alignments or intra- or extramedullary rods, are associated with significant higher variation of the leg axis correction. We used an image-free system (ORTHOPILOT TM, AESCULAP, FRG) for routine implantation of primary TKA. The standard software was used for revision TKA. Registration of anatomic and kinematic data was performed with the index implant left in place. The components were then removed. New bone cuts as necessary were performed under the control of the navigation system. The size of the implants and their thickness was chosen after simulation of the residual laxities, and ligament balance was adapted to the simulation results. The system did not allow navigation for centromedullary stem extension and any bone filling which may have been required. This technique was used for 54 patients. The accuracy of implantation was assessed by measuring the limb alignment and orientation of the implants on the post-operative radiographs. Limb alignment was restored in 88%. The coronal orientation of the femoral component was acceptable in 92% of the cases. The coronal orientation of the tibial component was acceptable in 89% of the cases. The sagittal orientation of the tibial component was acceptable in 87% of the cases. Overall, 78% of the implants were oriented satisfactorily for the five criteria. The navigation system enables reaching the implantation objectives for implant position and ligament balance in the large majority of cases, with a rate similar to that obtained for primary TKA. The navigation system is a useful aid for these often difficult operations, where the visual information is often misleading. The navigation system used enables facilitated revision TKA

Computer based navigation system improved the accuracy of limb and component alignment and decreased the incidence of outliers. The majority of previous studies were based on the infrared navigation system. We evaluate the availability and accuracy of the electromagnectic(EM) navigation system in total knee arthroplasty. From July 2006 to January 2007, 40 patients (50 TKAs) with osteoarthritis were participated in this study. AxiEM(Medtronics) was used and Nexgen CR(26 cases), and Nexgen CR flex(24 cases) were used. We analyzed the failure mode of navigation (7 cases), operation time and radiologic results (limb and component alignment). Total registration time was 4 minutes 45 seconds in average (Range : 3 minutes 45 seconds ~ 6 minutes 55 seconds). Failures in clinical applications resulted from non-recognition of EM tracker or paddle by metallic interference in 4 cases and from informational changes during surgery by fixation loss or loosening of the tracker in 3 cases. Radiologically, the mechanical axis changed from −11.2±7.21 (Range : −25.8~3.1) to 1.0±1.25(Range : −2.1~4.0) and 1 case of outlier occurred (valgus 4°). Component alignment is measured as followed: 89.3±1.6° of Theta angle, 89.9±1.5° of Beta angle, 1.8±2.5° of Gamma angle, 86.1±2.9 of Delta angle°. There were no complications related to the EM navigation. The EM navigation system helped to achieve accurate alignment of component and lower leg axis without any complications. It had several advantages such as relatively less invasiveness in fitting small instruments, not disturbing operation field, no interrupted line of sight, portable use, and applicability to any implant. However, metallic interference may be still problematic. The EM navigation had advantages; less invasiveness, no disturbing operation field, no interrupted line of sight, portable use and applicability to any implants. But metallic interference may be still problematic

Malpositioning of the component of a total knee implant and malalignment of the leg is one of the significant factors for the outcome after Total Knee Arthroplasty. Previous studies have shown that the use of a navigation system can improve these. This article presents the initial results of a prospective and non-randomised study describing navigated implantation in TKA with special reference to soft tissue balancing in knees with posttraumatic deformity. The secondary objective is to found out reproducibility of the software. Methods: Since January 2004, 15 patients with post-traumatic arthrosis of the knee and axial malalignment of more than 15 degrees, pre operative arc of motion 75 degrees admitted to our senior author for TKA have been followed up prospectively. The data were collected over a period of 25 months. Apart from the usual clinical evaluations, no patients had CT of the leg prior to the operation & postoperatively. Intra-operative and peri-operative morbidity data were collected and blood loss measured. Results: A postoperative leg axis between 3 degrees varus and 3 degrees valgus was obtained in all of the navigated knees after soft tissue balancing. The alignment of the components using computer-assisted surgery in regard to femoral varus/valgus, femoral rotation, tibial varus/valgus, tibial posterior slope, tibial rotation are reproducible and consistent. Computer-assisted surgery took longer with a mean increase of 31 minutes for kinematic data acquition. Intraoperatively we achieved range of motion more than 120 degrees. No patient required manipulation postoperatively for improving range of motion. Conclusion: These results support that the precise surgical reconstruction of the mechanical axis of the knee and proper alignment of the component is achievable in patients who suffered posttraumatic deformities and secondary arthrosis by using an intraoperative navigation system. It has been mentioned in the literature that minor deviations in the insertion point of Intramedullary instrumentation during TKA may result in malalign-ment of several degrees [Nuno-Siebrecht 2000], which can be avoided with these soft ware

INTRODUCTION. Computer-aided systems have been developed recently in order to improve the precision of implantation of a total knee replacement (TKR). Several authors demonstrated that the accuracy of implantation of TKR was higher with the help of a navigation system in comparison to the conventional, manual technique. Theoretically, the clinical results and the survival rates should be improved. Our team was one of the first all over the world which decided to use routinely a navigation system for TKR. Prostheses designed with a mobile bearing polyethylene component allow an increased congruence between femoral and tibial gliding surface, and should decrease the risk of long-term polyethylene wear. We designed a prosthetic system with one of the highest congruence on the current market. These prostheses might be technically more demanding than more conventional designs, and involve specific complications like bearing luxation. Navigation systems might be helpful in this was as well. In the present study, we wanted to test clinically the theoretic advantages of these three specific points of our system (navigated implantation, mobile bearing and increased congruence) with a five-year clinical and radiological follow-up. MATERIAL AND METHODS. 128 patients were operated on at our Department with this TKR system between 2000, and were contacted for a five-year clinical and radiological follow-up. The clinical and functional results were evaluated according to the Knee Society Scoring System (KSS). The subjective results were analyzed with the Oxford Knee Score. The accuracy of implantation was assessed on post-operative long leg antero-posterior and lateral X-rays. The survival rate after 5 years was calculated according to the Kaplan-Meier technique. RESULTS. The mean clinical score was 87 points (maximum of 100 points). The mean pain score was 43 points (maximum of 50 points). The mean flexion angle was 118°, and 33% oft he patients were able to reach 130° of knee flexion or more. The mean functional score was 70 points (maximum of 100). The mean Oxford Score was 23 points (best score = 12 points, worst score = 60 points). An optimal correction of the coronal leg axis (less than 3° off the neutral axis) was obtained in 87% of the cases. 67% of the cases had an optimal implantation of both tibial and femoral implants on both coronal and sagittal planes. The Kaplan-Meier survival rate was 97.4% after 5 years. DISCUSSION. The present study confirmed the efficiency of the navigation system used on the accuracy of implantation. The clinical and functional results after 5 years were at least as good as those published after conventional implantation of uncongruent prostheses. The survival rate was comparable as well to the already accepted gold standards. We observed no complication directly related to the new prosthetic system. The mean flexion angle was better that the results we observed with the previously used fixed bearing system. The question of the polyethylene wear could not be assessed because of the too short follow-up period. An additional follow-up study is planned after 5 more years

Introduction: The hypothesis of this work is to demonstrate that the Flexible Flat Foot (FFF) in children is not affected for any kind of treatment. The objective is: 1.-Rate the evolution of FFF during growing. 2.- Evaluate the accuracy of diagnosis criterion. 3.-Appoint the optimal age to diagnose and treat the FFF. 4.- Evaluate the different kinds of treatment. Material and methods: 242 children of both sex, aged between 3 and 5 years old, diagnosed of flexible flat foot. We compare three groups of treatment during three years. One group were treated with orthopaedic shoes and internal wedges, other with inserts, and the third were a control group. We evaluated: Clinical findings: age, sex, flat foot family antecedents, weight, degree of flat foot, valgus of ankle, age of begin to walk, ligament hiperlaxity, vicious direction of leg axis and erosion of shoes. Radiological measurements: An astragalus-1°metatarsian, Moreau and Costa-Bartani, and astragalus-calcaneus divergence angles, valgus of ankle according Viladot system. We perform a walking test with an electronic baropodometer “PEL 38” with 20 children of every group. Results: An 85 % child of our series has been normalized with growing. The overweight and ligament hiper-laxity are the most predisponent family antecedents. The Jack Test is not a prognostic factor of FFF. The vicious direction of leg is not related with the FFF. The valgus of ankle is physiologic. X-ray are not reliable to diagnose a FFF in children, while the walking test give us dates about the dynamic behaviour of FFF. Conclusions. – The flexible flat foot in children is normally corrected with growing and is a normal step of foot evolution. – Diagnosis of flat foot must be made in static and dynamic form. – Best age to diagnose flexible flat foot in children is between 5 or 6 years old. – The treatment don’t modify the normal evolution of flexible flat foot in children