OrthoPilot System Research Articles

Computer-assisted navigation in ACL reconstruction improves anatomic tunnel placement with similar clinical outcomes

BackgroundWhile the use of navigation systems in anterior cruciate ligament (ACL) reconstruction theoretically improves tunnel placement accuracy and clinical outcomes, the existing literature remains inconclusive. We aimed to evaluate the potential benefits of navigated ACL reconstruction on tunnel placement and clinical outcomes. MethodsIn this retrospective study, we evaluated a cohort of patients who underwent conventional or navigated (OrthoPilot system) primary ACL reconstruction at our institution from June 2004 to October 2009. Anteroposterior and lateral radiographic knee assessments were evaluated to assess postoperative tunnel positioning. Clinical outcomes, including the International Knee Documentation Committee classification, Lysholm score, and Tegner score, were evaluated preoperatively and 1-year postoperatively. Radiographic and clinical outcomes were compared and analysed using independent 2-sample t-tests and Chi-square tests. ResultsSixty patients met the inclusion criteria and were included for analysis, comprising of 26 navigated and 34 conventional reconstructions. Postoperative radiographs showed no differences in tibial tunnel position between both groups, but a significantly smaller deviation from the recommended position in the navigated group (navigated: 5.96 %; conventional: 7.92 %; p = 0.008). Femoral tunnel placements in the navigated group were significantly more perpendicularly away from the Blumensaat line (navigated: 38.90 %; conventional: 31.94 %; p = 0.001), with a greater deviation from recommended position (navigated: 11.00 %; conventional: 6.94 %; p = 0.009). There were no differences in 1-year postoperative clinical outcomes (p > 0.05). ConclusionNavigated ACL reconstruction resulted in a more anatomic femoral tunnel placement and similar clinical outcomes as conventional reconstruction. Further research should be conducted to clarify the potential biomechanical and clinical impacts of navigated ACL reconstruction.

Validation of a CT-free navigation system for the measurement of native acetabular alignment

Computer-assisted surgery is becoming more frequently used in the medical world. OrthoPilot™ Hip Suite CT-free navigation system (BBraun Aesculap, Tuttlingen, Germany) is one such computer-assisted navigation system used for total hip replacement surgery. The validity of OrthoPilot system remains to be determined independent of the manufacturer. The main aims of this study were to investigate the accuracy of OrthoPilot data while using surgical instruments and to confirm the suitability of the cup navigation algorithm. OrthoPilot was compared with the gold standard of a VICON movement analysis system. An aluminium pelvic phantom was machined with high accuracy to perform the experiments. Data were captured simultaneously from both OrthoPilot and VICON systems and acetabular angles were compared. Both systems produced comparable results for the distance between anatomical landmarks and acetabular angles. It can be concluded that data from the OrthoPilot system, if used correctly, are accurate enough for orthopaedic applications.

Differences in Measurement of Lower Limb Alignment Among Different Registration Methods of Navigation and Radiographs in TKA Using the OrthoPilot System

The purposes of this study were (1) to compare lower limb alignment measurements between radiographs and computer-assisted surgery and (2) to evaluate the discrepancy in lower limb alignment between computer-assisted surgery with a high tibial osteotomy protocol and computer-assisted surgery with a total knee arthroplasty (TKA) protocol in the same knee. Seventy-one TKAs were performed on patients with primary osteoarthritis using computer-assisted surgery. Preoperative lower limb alignment was measured using the mechanical axis during bipedal, weight-bearing, whole-leg anteroposterior radiography (measure 1). The intraoperative mechanical axis was measured with computer-assisted surgery according to the high tibial osteotomy protocol before joint exposure (measure 2). After changing the software and joint exposure, the intraoperative mechanical axis was measured with computer-assisted surgery according to TKA protocol (measure 3). After final TKA implantation, the lower limb mechanical axis was measured with computer-assisted surgery following the TKA protocol (measure 4). Postoperative lower limb alignment was measured using the mechanical axis on whole-leg standing anteroposterior radiographs (measure 5). The mechanical axis and median value from each group were compared. Factors affecting the mechanical axis measurement were also analyzed. The difference in the mechanical axis between measures 1 and 2, measures 1 and 3, and measures 2 and 3 was significant (P<.0001, <.0001, and =.0007, respectively). The difference between measures 4 and 5 was also significant (P<.0001). Factors affecting the mechanical axis measurement, such as age, height, weight, and range of motion, showed no correlation (R(2)=.07244 and adjusted R(2)=.01622). The pre- and postoperative radiological measurements of limb alignment using the mechanical axis were different from the intraoperative measurements with navigation.

Paper 115: Measuring the Position of the ACL Footprint with a Navigation System. Comparison with X-Ray, CT-Scan and Anatomic Measurements

Anterior cruciate ligament (ACL) reconstruction allows overall good results, but there is still a relevant rate of failure. It is well accepted that the main reason for ACL reconstruction failure is a misplacement of tibial or femoral tunnels. Conventional techniques rely mainly on surgical skill for intra-operative tunnel placement. It has been demonstrated that, even by experienced surgeons, there was a significant variation in the accuracy of tunnel placement with conventional techniques. Navigation systems might enhance the accuracy of ACL replacement. 10 cadaver knees with intact soft-tissue and without any intra-articular abnormalities were studied. We used a non image based navigation system (OrthoPilot ®, Aesculap, Tuttlingen, FRG). Localizers were fixed on bicortical screws on the distal femur and on the proximal tibia. Both cinematic and anatomic registration of the knee joint were performed by moving the knee joint in flexion-extension and palpating relevant intra- and extra-articular landmarks with a navigated stylus. The most anterior, posterior, medial and lateral point of both tibial and femoral attachment of the ACL were marked with metallic pins. The navigated stylus was positioned on these points, and the system recorded its position in comparison to the bone contours. Subsequently, we performed conventional plain AP and lateral X-rays and a CT-scan, and measured the position of the pins in comparison to the bone contours. Finally, all measurements were made again with a caliper after disarticulating the knee joint. We calculated the center of the footprint as the mid-point between the four pins of both tibial and femoral attachment for each measurement technique. All measurements were expressed as percentages of the bone size to compensate for the different sizes. The results were analyzed with a Friedman test with post-hoc comparison, considering the anatomical measurements as the reference. The mean medio-lateral position of the tibial tunnel was (origin at the lateral tibial border): - 52% (SD 2%) for anatomical measurement; - 50% (SD 2%) for navigated measurement; - 49% (SD 2%) for CT measurement; - 51% (SD 2%) for X-ray measurement. The differences were globally significant (p<0.001); there was a significant difference between the reference and navigated and CT measurement techniques. The mean antero-posterior position of the tibial tunnel was (origin at the anterior tibial border): - 53% (SD 7%) for anatomical measurement; - 50% (SD 7%) for navigated measurement; - 50% (SD 7%) for CT measurement; - 50% (SD 7%) for X-ray measurement. The differences were globally significant (p=0.03); there was a significant difference between the reference and the radiological measurement technique. The mean proximo-distal position of the femoral tunnel was (origin at the distal femoral border): - 75% (SD 12%) for anatomical measurement; - 78% (SD 15%) for navigated measurement; - 80% (SD 11%) for CT measurement; - 74% (SD 12%) for X-ray measurement. The differences were globally significant (p=0.05); there was no significant difference between the reference and any measurement technique. The mean antero-posterior position of the femoral tunnel was (origin at the anterior femoral border): - 79% (SD 13%) for anatomical measurement; - 83% (SD 19%) for navigated measurement; - 85% (SD 14%) for CT measurement; - 77% (SD 15%) for X-ray measurement. The differences were globally significant (p<0.01); there was no significant difference between the reference and any measurement technique. Anatomical measurement of the location of the ACL footprint is the gold standard in an experimental situation. CT-scan measurement of the positioning of the ACL replacement tunnels is the gold standard in a clinical situation. X-ray measurement of the positioning of the ACL replacement tunnels is the most used technique in a clinical situation. Navigation might help improving the accuracy and the reproducibility of ACL replacement. However, the precision of each system has to be evaluated. The measurements by the OrthoPilot system were significantly different from the anatomical reference, but the difference appeared to be clinically not relevant. We concluded that this system allowed locating in a precise and accurate way the position of the ACL footprint on both tibial and femoral sides when compared to the reference techniques. This navigation system is precise and accurate for anatomical measurements in the knee joint. This should help the surgeon to define the placement of the tunnels according to anatomical landmarks during ACL replacement. The OrthoPilot navigation system is precise and accurate for anatomical measurement of the tunnel placement during ACL replacement.

Reliability of leg alignment using the OrthoPilot system depends on knee position: a cadaveric study

Despite the increase in clinical use of navigation systems in total knee arthroplasty, few studies have focused on the reproducibility of these systems. The aim of the present study was to assess the influence of knee position and observer experience on intra- and inter-observer agreement in limb alignment assessment with the OrthoPilot system. Limb alignment in the coronal plane and extension range of the knee were assessed in four embalmed cadaveric specimens by five independent observers and measurements were repeated four times to determine intra- and inter-observer agreement, expressed as intraclass correlation coefficients (ICCs). Additionally, navigation results were compared against figures from conventional measurement of leg alignment (ground truth). Intra- and inter-observer agreements were excellent for assessing the extension range (ICC, 0.97 and 0.95) and the coronal femuro-tibial axis in knee extension (ICC, 0.92 and 0.88) but were generally worse in knee flexion (ICC, 0.62 and 0.55). There was an increased tendency of intraobserver errors in observers with less clinical experience. Mean correlation with conventional measurements was fair (Spearman's rho 0.61). The OrthoPilot system showed excellent reproducibility for assessment of extension range and coronal limb alignment. However, assessments of coronal limb alignment in flexion were prone to error and caution should be taken when relying on these measurements.

Mini-invasive approach and navigation in total prosthesis of the hip

The anterior approach to the hip, initially described by Hueter, has been modified and used by Jean and Robert Judet since 1947 for fixing an acrylic prosthesis [1,2]. In 1993, Marc Siguier rendered this approach completely mini-invasive by avoiding any muscular desinsertion or sectioning of tendons [3]. When we learnt about the possibilities of using the navigation technique for a hip prosthesis using the Orthopilot system, we decided to combine these two innovations so as to induce a minimum of aggression and a maximum of security while fixing a hip prosthesis. A study carried out on the positioning of the acetabulum, with or without navigation, as well as a comparison between two navigation systems are mentioned in an attempt to validate the relevance of the frame of references.

(iii) The anterior cruciate ligament and navigation

Summary Here, we describe the current status of navigation systems used in anterior cruciate ligament surgery. Various systems of navigation are available; we use the Orthopilot system and the Praxim system daily. The goal of navigation is to help the surgeon to place the tibial and femoral tunnels in the correct position before drilling takes place. Thus, the ultimate goal is better positioning and isometry of the ligament graft in order to decrease the risk of adverse outcomes.

Computer-Assisted Navigation Increases Precision of Component Placement in Total Knee Arthroplasty

In our clinical study, 200 total knee arthroplasties were evaluated to compare the use of the OrthoPilot system with conventional mechanical instrumentation. Long-term outcome of total knee replacement depends mainly on the accuracy of implant positioning and restoration of the mechanical leg axis. Our experience was that navigation could achieve a greater degree of accuracy concerning the aforementioned aspects. Among 513 primary-inserted total knee replacements, 100 navigated knees were compared with 100 conventionally implanted knees after matching the two groups of patients by gender, body mass index, age, preoperative deformities, radiographic findings, and operating time. Three weeks after surgery, the radiographic results were significantly better in the computer-assisted group compared with the results in the conventional group when we assessed component positioning in four axes. Only the sagittal tibial component angle was not significantly different. Total knee arthroplasty using the OrthoPilot system led to increased precision of tibial and femoral component positioning in comparison with hand-guided replacement surgery. An additional 10 minutes of operating time was acceptable. Navigation-specific complications were not seen, and the number of outliers decreased. Because computer navigation in orthopaedics is a new technology, data regarding long-term outcomes are not available. Diagnostic study, Level II-1 (retrospective study). See the Guidelines for Authors for a complete description of levels of evidence.

Navigation in der Knieendoprothetik - vorläufige klinische Erfahrungen und prospektiv vergleichende Studie gegenüber konventioneller lmplantationstechnik

The efficiency of a computer-integrated instrumentation system in knee arthroplasty was evaluated and compared with a conventional instrumentation system. The OrthoPilot System defines the individual axis of the leg by means of an intraoperative kinematic analysis. LED's mounted on rigid bodies and screwed to the pelvis, femur and tibia are localized by a 3D infrared camera which is linked to a UNIX work station. The integrated calculation program leads to definition of the centres of hip, knee and ankle. Thereafter, LED-equipped alignment instruments allow definition of the femoral and tibial main resection planes. The first sixty cases were included in the study. In addition, thirty cases each were entered into an OrthoPilot group and in a similar conventional control group. The navigated cohort consists of cases one to thirty, thus enclosing the "learning curve". Leg axes and femoral and tibial angles were assessed radiographically at the three-months postoperative control. Radiological measurements of the OrthoPilot group were clearly superior to those of the manual group. The differences, however, were not statistically different in the parameters "mechanical axis", "femoral axis lat." and "tibial axis ap.". With regard to the parameter "tibial axis lat." a significant difference in favour of the navigation system was observed. The measurements of "femoral axis ap." were insignificantly better in the manual group. In general, a slight tendency towards valgus positioning of the femoral components when using the navigation system has to be discussed. Complications influencing the clinical outcome did not occur. Additional time for navigation is calculated in a range of ten to fifteen minutes. The OrthoPilot system clearly facilitates proper alignment of endoprosthetic components in femur and tibia. Generally, the obtained values representing endoprosthetic alignment are superior to conventional technique. Marked deviations from ideal alignment can almost be avoided by means of the navigation system. During the learning curve the OrthoPilot system gained in reliability and reproducability.

Computerised OrthoPilot system in arthroprosthesis surgery of the knee

The OrthoPilot computerised system assists surgeons in the implantation of total knee prostheses. The technique uses a computer to acquire, in the operating room, data on the anatomical axis of the lower limb where the prosthesis is to be implanted. This is accomplished by infrared transmission diodes which relate information on the size of the femur and on the deepest point of the tibial wear and tear. The software processes the data and provides the surgeon with indications for regulating the incision guides, perpendicular to the mechanical axis, for correcting axial deformities, and for correcting the slope of the prosthetic components. In addition, it gives the size of the femoral component, the height of the tibial incision, the femoral extrarotation and a constant control of the varus-valgus correction and of the pro- and recurvatum of the limb, in both extending and flexing movements.