PRAXIM SELECT PEER-REVIEWED PUBLICATIONS
TOTAL KNEE RECONSTRUCTION
Navigated revision knee arthroplasty using a system designed for primary surgery.
Massin P, Boyer P, Pernin J, Jeanrot C.,
Comput Aided Surg. 2008 Jul;13(4):179-87.
While navigation is now recognized as an efficient tool for improving femoro-tibial alignment of primary knee prostheses, its use in revision surgery has not yet been fully evaluated. We describe a procedure based on a bone morphing acquisition performed on the surface of the original implants, followed by a dependant bone cut sequence (tibia first). Using the current system, a preoperative CT-scan measurement of the original femoral component was required. Knee balancing was achieved using spacer blocks, with the trial tibial component and the original femoral component still in place. Preliminary experience from 19 cases, some with severe bone loss requiring reconstruction, is reported. A retrospective comparison to 10 non-navigated revision cases performed concomitantly by the same operating surgeon was carried out. Although there was no significant difference in the number of outliers for the two series, navigation appeared to be a valuable aid in reconstructing both bone extremities, while controlling the level of the joint line. However, definitive validation requires further prospective and comparative investigations in larger series.
Clinical Results of Navigated Total Knee Arthroplasty in Patients with Posttraumatic Deformity and Arthrosis
A.P. Schulz, S. Magerlein, S Fuchs, A. Unger, L. Simon, B. Kienast, M. Faschingbauer and A. Paech,
Research Journal of Medical Sciences 1 (3): 178-182, 2007
Bone Morphing: 3D reconstruction without pre- or intra-operative imaging
E.Stindel, N.Perrin, JL.Briard, S.Lavallée, C.Lefevre, J.Troccaz,
Stiehl James B., Navigation and MIS in Orthopedic Surgery (Hardcover), Chapter 5, Springer, 2006
Navigated Total Knee Arthroplasty and the Surgetics Bone Morphing System
E.Stindel, JL.Briard, C.Plaskos, J.Troccaz,
Stiehl James B., Navigation and MIS in Orthopedic Surgery (Hardcover), Chapter 16, Springer, 2006
Detection of the center of the hip joint in computer-assisted surgery: an evaluation study of the Surgetics algorithm.
Stindel E, Gil D, Briard JL, Merloz P, Dubrana F, Lefevre C.
Comput Aided Surg. 2005 May;10(3):133-9.
OBJECTIVE: The aim of this paper is to assess the accuracy of an algorithm implemented by PRAXIM in the SURGETICS navigation station for detection of the hip center. This study will assess the robustness and accuracy of the algorithm in various clinical situations such as those involving non-sphericity of the femoral head, motion of the pelvis during hip center detection, and restricted range of motion. MATERIALS AND METHODS: The localization of the hip center, based on kinematics, relies on the recording of n successive positions of the femoral rigid body in the localizer reference system during a passive circumduction motion of the hip joint. Therefore, the shape of the clouds of points acquired may vary from one acquisition to the next. To allow a comprehensive study of the consequences of these variations for hip center detection, we developed a simulator to generate numerous clouds of points. Results given subsequently for each test are the values of the difference between the femoral mechanical axis computed with C(c), the computed hip center, and the same axis computed with C(o), the reference hip center. RESULTS: Test 1: Sensitivity to noise. The errors ranged from 3.33 E - 12 (SD 3.29E - 12) for a noise of 0 mm to 8.18E - 1 (SD - 7.05E - 1) for a noise of 15 mm. Test 2: Sensitivity to the shape of the acquisition motion. All trajectories gave an error < 1 degrees . Test 3: Sensitivity to restricted range of motion. No value > 1 degrees was found during this test. Test 4: Sensitivity to the distance between two points of the cloud. No value > 0.5 degrees was found during this test. Test 5: Sensitivity to the number of points included in the cloud. No value > 1 degrees was found during this test. CONCLUSIONS: The Surgetics algorithm is robust to noise, can compensate for pelvic motion, and can be used even in the case of restricted range of motion.
Bone Morphing versus freehand localization of anatomical landmarks: consequences for the reproducibility of implant positioning in total knee arthroplasty
Perrin N, Stindel E, Roux C.
Comput Aided Surg. 2005 Sep-Nov;10(5-6):301-9
OBJECTIVE: This study analyzed the influence of the acquisition method in image-free computer-assisted total knee arthroplasty (CAS-TKA), and the reproducibility of implant planning using BoneMorphing, a 3D morphometric model obtained by a 3D-to-3D elastic registration of statistical models to sparse point clouds acquired directly on the bone surface with a pointer. MATERIALS AND METHODS: Five surgeons (one expert, four trainees) each performed a CAS-TKA hybrid protocol based on morphometric models and landmarks on a cadaveric knee 10 times. In addition, several additional landmarks were digitized during each acquisition. The reproducibility of the implant positioning and sizing, as determined by an implant planning algorithm with morphometric models, was compared to direct digitization accuracy. RESULTS: Femoral and tibial implant positioning parameters with the hybrid protocol resulted in intra-surgeon standard deviations (SDs) of less than+/-1.4 degrees for rotation and 1.9 mm for translation for all surgeons in all directions except for tibial axial rotation (the only parameter determined by a digitized landmark and not recomputed in the 3D model). The variability in individual landmark digitization varied from 2 to 5 mm SD for certain landmarks, with ranges of 15-25 mm across all surgeons. The comparison study showed an improvement in femoral rotation reproducibility with the morphometric model when using the posterior condylar axis. Tibial implant reproducibility for each method was comparable, with the morphometric model giving better results in well-digitized areas such as the tibial plateau. CONCLUSION: A CAS-TKA protocol based on a deformed statistical model offers reproducible implant positioning. Some landmarks, such as distal condyles, show sufficient reproducibility in the direction of interest, while others, such as the anterior tibial tubercle, can lead to hazardous implant positioning. This should be taken into consideration when designing a CAS-TKA system with bony landmarks. In areas where a sufficient number of points have been digitized with good coverage, such as on the distal and posterior femoral condyles or the tibial plateau areas, the information derived from the 3D model is more accurate and reproducible than that derived from digitization. Good training and a guiding user interface are essential to guarantee coverage quality.
Computerised and technical navigation in total knee-arthroplasty
U. Böhling, H. Schamberger, U. Grittner, J. Scholz,
J Orthopaed Traumatol (2005) 6:69–75
The objective of the study was to evaluate the precision, concordance, practicability and the early clinical outcome of the use of a computerised navigation system in a comparative study with a group of 100 patients. Two groups of 50 patients each underwent implantation of a bicondylar knee prosthesis either by means of the freehand navigation system or by means of technical instrumentation. We found that the computerised navigation system provided a higher precision than the technically instrumented implantation: 94% of the prostheses implanted with the navigation system have an alignment within a range of -3° to 3° on of the Mikulicz line. Only 46% of the patients operated by means of the technical instrumentation reached this aspired result. Furthermore, the navigation system showed smaller ranges in the deviation of the aspired alignment. The radiological and computer-modeled alignment values differed both pre- and postoperatively, but to a larger extent before surgery. The varus or valgus deviations of the axis were more distinct radiologically under the weight of the patient’s body than in the computer model. The clinical outcome examined by the use of the HSS score after a mean followup of 7 months is good in both groups, and without significant differences. On average, the duration of surgery was 13 minutes longer in the computerised navigation group. We conclude that the benefit of the computerised navigation system is represented by the high improvement of precision. Achieving early clinical results identical to those in the technical instrumentation group, we expect a reduction of aseptic loosening in the computerised navigation group.
Knee Prosthesis navigation System
J.Sholtz, V.Makris, H.Schamberger, G.Panides,
Journal of Bone & Joint Surgery Br. 2004, 86-B:SUPP II; 181
Surgetics Total Knee Arthroplasty using Bone-Morphing-preliminary results based on 60 clinical cases
E.Stindel, JL.Briard, P.Merloz, F.Dubrana, S.Plaweski, C.Lefevre,
Proceedings of CAOS 2003, Marbella – Spain.
The bone morphing : 3D morphological data for Total Knee Arthroplasty
Stindel E., Briard J., Merloz P., Plaweski S., Dubrana F., Lefevre C., Troccaz J.
Computer-Aided Surgery 7(3) , (2002) 156-168
OBJECTIVE: The clinical outcome of a total knee arthroplasty (TKA) is mainly determined by the accuracy of the surgical procedure itself. To improve the final result, one must take into account (a) the alignment of the prosthesis with respect to the mechanical axis, and (b) the balance of the soft tissues. Therefore, morphologic data (such as the shape of the epiphysis) and geometric data are essential. We present a new method for performing TKA based on morphologic and geometric data without preoperative images. MATERIALS AND METHODS: The global method is based on the digitization of points with an optical 3D localizer. For the morphologic acquisitions, we use a method based on the registration of sparse point data with a 3D statistical deformable model. To build the mechanical axis, we use a kinematics method for the hip center and digitization of anatomical landmarks for the ankle centers. The knee center is not determined by digitization or kinematics of the knee, as this would not be accurate. The surgical planning relies totally on the soft-tissue balance, which is the key issue for a good kinematics result. RESULTS: We have used this system for 6 months in a randomized clinical trial involving 35 patients to date. For the first 11 patients that could be measured in the navigation group, the postoperative frontal alignment was within the range of 180 +/- 3 degrees. Fluoroscopic assessment of the soft-tissue balancing will be performed at the conclusion of an extended 2-year study to evaluate the results from a functional point of view. CONCLUSION: Bone Morphing is an accurate, fast, and user-friendly method that can provide morphologic as well as geometric data. We have introduced the important notion of soft-tissue balancing into the intraoperative planning step to optimize the kinematics as well as the anatomy. Therefore, this method should be considered as an alternative to the CT-based method.