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Improved knee kinematics after intraoperative soft tissue balanceing by computer assisted knee arthroplasty
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Journal o f Biomechanics 2006, Vol. 39 (Suppl 1)
approaches. In particular, we are focusing on the use of magnetic resonance (MR) images for planning, and on tracked ultrasound for intraoperative registration. These two elements increase the amount of information to surgeon, while reducing the invasiveness and radiation exposure. Combined with the miniature electromagnetic tracking sensors, this approach offers a minimally invasive solution that can be applied beyond ACL procedure. The key to using MR images for planning and navigation is in fast and highly automatic image segmentation. We have developed a statistical atlas based segmentation that allows segmentation of the femur and tibia within several minutes. The segmentation is initialized by coarsely registering the atlas mean to the MR images and then iterated over the atlas pose and principal components weights until an optimal fit is found. Once the MR image is segmented, it is used to preoperatively plan the ligament insertion tunnels and to register the plan to the surgical site. Ultrasound-based intraoperative registration enables the navigation in the environment of minimal exposure, because no direct contact with the bone is required. A tracked ultrasound probe is used to collect the bone profiles which are then automatically segmented and registered to the MR-derived surface model. Current laboratory and cadaver tests yield the registration accuracy in the order of 1 degree, which is sufficient for clinical use.
4689 We-Th, no. 21 (P62) Alignment before and after component implantation in navigated TKA A. Ensini 1, E Catani 1,2, L. Bianchi 1, A. Leardini 2, S. Giannini 1,2. 1V/Divisione Clinica Qrtopedica, 2Laboratorio di Analisi del Movimento, Istituti Qrtopedici Rizzoli, Bologna, Italy
Introduction: In navigation-assisted surgery of TKA, femoral and tibial anatomical frames are defined from anatomical landmarks, and these are targeted, by adjusting position and orientation of the bone saw guides accordingly, for final prosthesis component alignments. However, this drives bone sawing only, and then bone and cement preparation and component implantation are performed manually. In this study, final component alignments were compares intra-operatively with the corresponding original resection planes to quantify the effect of these critical manual procedures. Methods: Fifty Scorpio (Stryker-Howmedica) TKAs were analyzed during the operation performed following the recommendations of the Stryker Knee Navigation System (Stryker-Navigation, USA), which implies trackers attached through bone screws to the distal femur and proximal tibia and to the bone saw guides, and an 'anatomical survey' to define the anatomical frames to be targeted. Orientation of the bone resection planes in the frontal plane for the femur and in the frontal and sagittal planes for the tibia were recorded, by means of an instrumented probe and with a 0.50 resolution. Then, component implantation was performed fully and these orientations were recorded again. Results: The angular differences between pre- and post-implantation were as large as 30 in 4 TKAs. In the frontal plane of the femur, and in the frontal and sagittal planes of the tibia, differences larger than 10 were observed respectively in 42%, 28%, 62% of the patients. Considering that 10 is the claimed achievable accuracy of the navigation system, and that the correct alignment goal was achieved at the resection planes, these figures reveal that in a considerable number of patients the benefit obtained by navigation are then lost by the manual procedures implied in component implantation. These results put also concerns in the several post-operative statistical papers which compare conventional and navigated TKAs. 5921 We-Th, no. 22 (P62) A navigated procedure for kinematic evaluations during knee surgery S. Martelli, S. Zaffagnini, S. Bignozzi, N. Lopomo. Rizzoli Institutes, Lab. Biomeccanica, Bologna, Italy This study describes a novel method for an accurate and rapid evaluation of joint kinematics during reconstructions of anterior cruciate ligament (ACL) using a navigation system, a custom software and an optimized elaboration process to quantify knee laxity during manual kinematic manouvers. The intervention is performed with a standard approach and equipment and the navigated procedure is performed after tunnel preparation according to the following steps: (1) two reference frames of the optical Iocalizer are fixed to femur and tibia in the surgical incisions; the surgeon acquires external anatomical landmark for computing a joint coordinate system; (2) kinematic tests, such as drawer test or internal-external stress, are recorded and the resulting knee laxity is displayed on screen. The performances of this protocol were estimated by experimental validation of 70 volunteers undergoing ACL reconstruction. Tests of inter-operator repeatability were performed by a senior surgeon repeating the tests 4 times in 30 cases; inter-operator repeatability was estimated comparing 3 surgeons (2 expert and 1 non-expert) 40 cases. The proposed method is fast (10 minutes of additional surgical time), has a short learning curve (5 cases), is scarcely invasive, both for patients and for surgical technique. The computation of laxity-stability showed a intra-surgeon repeatability of 1.50 for varus-valgus rotation, 30 for internal-external rotation,
Poster Presentations and 2mm for antero-posterior displacement both when comparing experts surgeons or expert and non-expert ones. The inter-operator repeatability is 0.80 for varus-valgus rotation, 1.60 for internal-external rotation, and 0.8 mm for antero-posterior displacement This method represents a reliable quantitative evaluation of knee kinematics for surgical applications, is flexible and suitable for all standard kinematic measurements and provide an immediate feedback to the surgeon, therefore it could improve the present clinical assessment of the knee motion during surgery. 6682 We-Th, no. 23 (P62) Improved knee kinematics after intraoperative soft tissue balanceing by computer assisted knee arthroplasty M. Bhattacharyya, B. Gerber. University Hospital Lewisham, London, UK Failure to restore mediolateral soft tissue balance and flexion extension gap cause postoperative instability and early failure of total knee arthrplasty. We aim to critically look into our result of soft tissue balance in total knee arthroplasty using Orthopilot Navigation system intraoperatively. Design: Prospective clinical study over three years [2003-2005]. Methods and Materials: 35 knees with axial malalignment with non correctable varus deformity of mean 15 and valgus 18 degrees were operated for primary knee osteoarthritis or rheumatoid, were analysed. Mean preoperative arc of motion was less than 85 degrees. Results: Axial malalignment were corrected in all knees. We found all components were ± 3 degrees varus/valgus deviation. Mean posterior tibial slope was 4 degrees. We achieved average range of motion 0-129 intraoperatively. Conclusion: Precise surgical reconstruction of mechanical axis of the knee and accuracy of the alignment of the components were achieved with Orthopilot navigation system. Although surgical time is longer mean [25 minutes] than conventional manual implantation, correction of alignment may reduce the risk of wear of the polyethylene and thereby early revision surgery. We need long term result to verify the benefit for the patients. 5488 We-Th, no. 24 (P62) Non-rigid alignment of preoperative MRI, fMRI and DT-MRI with intraoperative MRI to enhance visualization and navigation in image-guided neurosurgery N. Archip, O. Clatz, S. Whalen, D. Kacher, F. Jolesz, A. Golby, P.M. Black, S.K. Warfield. Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA In the treatment of patients with low grade gliomas, a number of studies now suggest that achieving gross total tumor resection increases survival rates. Intraoperative MRI enables detection of residual tumor and enables increased tumor resection volume. Tumors nearby eloquent cortex or functionally significant white matter fiber tracts pose a significant difficulty in achieving gross total tumor resection, while avoiding postoperative neurological deficits. Recent studies have indicated that diffusion tensor imaging and functional imaging enable the delineation of critical brain structures and hence facilitates identification of the margin for resection that increases tumor volume resection while preserving critical tissue. In this work we examine the utility of a non-rigid registration algorithm in compensating for the deformation of the brain that occurs during tumor resection, and project preoperatively acquired fMRI and DT-MRI into the intraoperative configuration of the brain. Functional MRI and high spatial resolution DT-MRI, together with MPRAGE and T2w structural MRI was acquired at 3 T prior to 11 neurosurgery cases. Both SPGR and T2w images were acquired with a 0.5 T magnet on several occasions during each procedure. The alignment of the preoperative data to the intraoperative data was carried out during the surgery. Quantitative assessment of the alignment accuracy was carried out. A method based on edge detection was used to estimate corresponding boundary positions. The registration accuracy of each two structural MRI is measured based on the 95% Hausdorff distance between points of the edges. Overall, the mean error for the non-rigid registration accuracy was 1.82 mm while the ratio between the mean rigid registration error and the mean nonrigid registration error is 4.58. This demonstrates that non-rigid registration can achieve an alignment accuracy 4.58 times better than commonly used rigid registration. The major contribution of the presented work is the demonstration of rigid and non-rigid alignment of the pre-operative fMRI and DTI with intra-operative 0.5T MRI achieved during the neurosurgery.
Journal o f Biomechanics 2006, Vol. 39 (Suppl 1)
approaches. In particular, we are focusing on the use of magnetic resonance (MR) images for planning, and on tracked ultrasound for intraoperative registration. These two elements increase the amount of information to surgeon, while reducing the invasiveness and radiation exposure. Combined with the miniature electromagnetic tracking sensors, this approach offers a minimally invasive solution that can be applied beyond ACL procedure. The key to using MR images for planning and navigation is in fast and highly automatic image segmentation. We have developed a statistical atlas based segmentation that allows segmentation of the femur and tibia within several minutes. The segmentation is initialized by coarsely registering the atlas mean to the MR images and then iterated over the atlas pose and principal components weights until an optimal fit is found. Once the MR image is segmented, it is used to preoperatively plan the ligament insertion tunnels and to register the plan to the surgical site. Ultrasound-based intraoperative registration enables the navigation in the environment of minimal exposure, because no direct contact with the bone is required. A tracked ultrasound probe is used to collect the bone profiles which are then automatically segmented and registered to the MR-derived surface model. Current laboratory and cadaver tests yield the registration accuracy in the order of 1 degree, which is sufficient for clinical use.
4689 We-Th, no. 21 (P62) Alignment before and after component implantation in navigated TKA A. Ensini 1, E Catani 1,2, L. Bianchi 1, A. Leardini 2, S. Giannini 1,2. 1V/Divisione Clinica Qrtopedica, 2Laboratorio di Analisi del Movimento, Istituti Qrtopedici Rizzoli, Bologna, Italy
Introduction: In navigation-assisted surgery of TKA, femoral and tibial anatomical frames are defined from anatomical landmarks, and these are targeted, by adjusting position and orientation of the bone saw guides accordingly, for final prosthesis component alignments. However, this drives bone sawing only, and then bone and cement preparation and component implantation are performed manually. In this study, final component alignments were compares intra-operatively with the corresponding original resection planes to quantify the effect of these critical manual procedures. Methods: Fifty Scorpio (Stryker-Howmedica) TKAs were analyzed during the operation performed following the recommendations of the Stryker Knee Navigation System (Stryker-Navigation, USA), which implies trackers attached through bone screws to the distal femur and proximal tibia and to the bone saw guides, and an 'anatomical survey' to define the anatomical frames to be targeted. Orientation of the bone resection planes in the frontal plane for the femur and in the frontal and sagittal planes for the tibia were recorded, by means of an instrumented probe and with a 0.50 resolution. Then, component implantation was performed fully and these orientations were recorded again. Results: The angular differences between pre- and post-implantation were as large as 30 in 4 TKAs. In the frontal plane of the femur, and in the frontal and sagittal planes of the tibia, differences larger than 10 were observed respectively in 42%, 28%, 62% of the patients. Considering that 10 is the claimed achievable accuracy of the navigation system, and that the correct alignment goal was achieved at the resection planes, these figures reveal that in a considerable number of patients the benefit obtained by navigation are then lost by the manual procedures implied in component implantation. These results put also concerns in the several post-operative statistical papers which compare conventional and navigated TKAs. 5921 We-Th, no. 22 (P62) A navigated procedure for kinematic evaluations during knee surgery S. Martelli, S. Zaffagnini, S. Bignozzi, N. Lopomo. Rizzoli Institutes, Lab. Biomeccanica, Bologna, Italy This study describes a novel method for an accurate and rapid evaluation of joint kinematics during reconstructions of anterior cruciate ligament (ACL) using a navigation system, a custom software and an optimized elaboration process to quantify knee laxity during manual kinematic manouvers. The intervention is performed with a standard approach and equipment and the navigated procedure is performed after tunnel preparation according to the following steps: (1) two reference frames of the optical Iocalizer are fixed to femur and tibia in the surgical incisions; the surgeon acquires external anatomical landmark for computing a joint coordinate system; (2) kinematic tests, such as drawer test or internal-external stress, are recorded and the resulting knee laxity is displayed on screen. The performances of this protocol were estimated by experimental validation of 70 volunteers undergoing ACL reconstruction. Tests of inter-operator repeatability were performed by a senior surgeon repeating the tests 4 times in 30 cases; inter-operator repeatability was estimated comparing 3 surgeons (2 expert and 1 non-expert) 40 cases. The proposed method is fast (10 minutes of additional surgical time), has a short learning curve (5 cases), is scarcely invasive, both for patients and for surgical technique. The computation of laxity-stability showed a intra-surgeon repeatability of 1.50 for varus-valgus rotation, 30 for internal-external rotation,
Poster Presentations and 2mm for antero-posterior displacement both when comparing experts surgeons or expert and non-expert ones. The inter-operator repeatability is 0.80 for varus-valgus rotation, 1.60 for internal-external rotation, and 0.8 mm for antero-posterior displacement This method represents a reliable quantitative evaluation of knee kinematics for surgical applications, is flexible and suitable for all standard kinematic measurements and provide an immediate feedback to the surgeon, therefore it could improve the present clinical assessment of the knee motion during surgery. 6682 We-Th, no. 23 (P62) Improved knee kinematics after intraoperative soft tissue balanceing by computer assisted knee arthroplasty M. Bhattacharyya, B. Gerber. University Hospital Lewisham, London, UK Failure to restore mediolateral soft tissue balance and flexion extension gap cause postoperative instability and early failure of total knee arthrplasty. We aim to critically look into our result of soft tissue balance in total knee arthroplasty using Orthopilot Navigation system intraoperatively. Design: Prospective clinical study over three years [2003-2005]. Methods and Materials: 35 knees with axial malalignment with non correctable varus deformity of mean 15 and valgus 18 degrees were operated for primary knee osteoarthritis or rheumatoid, were analysed. Mean preoperative arc of motion was less than 85 degrees. Results: Axial malalignment were corrected in all knees. We found all components were ± 3 degrees varus/valgus deviation. Mean posterior tibial slope was 4 degrees. We achieved average range of motion 0-129 intraoperatively. Conclusion: Precise surgical reconstruction of mechanical axis of the knee and accuracy of the alignment of the components were achieved with Orthopilot navigation system. Although surgical time is longer mean [25 minutes] than conventional manual implantation, correction of alignment may reduce the risk of wear of the polyethylene and thereby early revision surgery. We need long term result to verify the benefit for the patients. 5488 We-Th, no. 24 (P62) Non-rigid alignment of preoperative MRI, fMRI and DT-MRI with intraoperative MRI to enhance visualization and navigation in image-guided neurosurgery N. Archip, O. Clatz, S. Whalen, D. Kacher, F. Jolesz, A. Golby, P.M. Black, S.K. Warfield. Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA In the treatment of patients with low grade gliomas, a number of studies now suggest that achieving gross total tumor resection increases survival rates. Intraoperative MRI enables detection of residual tumor and enables increased tumor resection volume. Tumors nearby eloquent cortex or functionally significant white matter fiber tracts pose a significant difficulty in achieving gross total tumor resection, while avoiding postoperative neurological deficits. Recent studies have indicated that diffusion tensor imaging and functional imaging enable the delineation of critical brain structures and hence facilitates identification of the margin for resection that increases tumor volume resection while preserving critical tissue. In this work we examine the utility of a non-rigid registration algorithm in compensating for the deformation of the brain that occurs during tumor resection, and project preoperatively acquired fMRI and DT-MRI into the intraoperative configuration of the brain. Functional MRI and high spatial resolution DT-MRI, together with MPRAGE and T2w structural MRI was acquired at 3 T prior to 11 neurosurgery cases. Both SPGR and T2w images were acquired with a 0.5 T magnet on several occasions during each procedure. The alignment of the preoperative data to the intraoperative data was carried out during the surgery. Quantitative assessment of the alignment accuracy was carried out. A method based on edge detection was used to estimate corresponding boundary positions. The registration accuracy of each two structural MRI is measured based on the 95% Hausdorff distance between points of the edges. Overall, the mean error for the non-rigid registration accuracy was 1.82 mm while the ratio between the mean rigid registration error and the mean nonrigid registration error is 4.58. This demonstrates that non-rigid registration can achieve an alignment accuracy 4.58 times better than commonly used rigid registration. The major contribution of the presented work is the demonstration of rigid and non-rigid alignment of the pre-operative fMRI and DTI with intra-operative 0.5T MRI achieved during the neurosurgery.