The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Charels Tonkin - One of the best experts on this subject based on the ideXlab platform.
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A 2 yr longitudinal radiographic study examining the effect of a bisphosphonate (risedronate) upon subchondral bone loss in osteoarthritic knee patients
Rheumatology, 2007Co-Authors: Chris J. Buckland-wright, E. A. Messent, C. O. Bingham, R. J. Ward, Charels TonkinAbstract:OBJECTIVES: To determine whether risedronate (RIS) slows down Trabecular bone loss in the medial compartment of the proximal tibia, a characteristic of patients with progressive knee osteoarthritis (OA). METHODS: Initially, 100 patients were randomly selected from each treatment group (each N approximately 300) comprising placebo and RIS 5 mg/day, 15 mg/day and 50 mg/week from a double blind, multi-centre, placebo-controlled, 2 yr investigation of OA knee patients in North America. Using fluoroscopic semi-flexed standard radiography, baseline and exit knee radiographs were digitized by laser scanner. Following computerized measurement of minimum medial compartment joint space width, each group was subdivided into joint space narrowing (JSN) non-progressor or JSN-progressor (JSN >or=0.6 mm measured at any point post-baseline). Computerized method of fractal signature analysis (FSA) quantified longitudinal changes separately in horizontal and vertical Trabeculae in region of interest (three-fourth width of tibial compartment x 6 mm height) in the medial compartment. Following the initial study, all JSN-progressor knees within the entire patient cohort (N = 1232) were similarly analysed. RESULTS: OA knees in JSN non-progressor group had a slight decrease in FSA for vertical and horizontal Trabeculae and showed no drug effect. In JSN-progressor knees, bone loss was greater in both placebo and RIS 5 mg/day groups compared with those in RIS 15 mg/day group in which Trabeculae were retained, and in the RIS 50 mg/week group in which the vertical Trabecular number increased significantly (P < 0.05). CONCLUSION: This preliminary study showed that patients with marked cartilage loss (JSN>or=0.6 mm) receiving RIS 15 mg/day retained vertical Trabecular structure, and those receiving RIS 50 mg/week increased vertical Trabecular number, thereby preserving the structural integrity of subchondral bone in knee OA.
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a 2 yr longitudinal radiographic study examining the effect of a bisphosphonate risedronate upon subchondral bone loss in osteoarthritic knee patients
Rheumatology, 2006Co-Authors: J C Bucklandwright, E. A. Messent, C. O. Bingham, R. J. Ward, Charels TonkinAbstract:Objectives. To determine whether risedronate (RIS) slows down Trabecular bone loss in the medial compartment of the proximal tibia, a characteristic of patients with progressive knee osteoarthritis (OA). Methods. Initially, 100 patients were randomly selected from each treatment group (each N� 300) comprising placebo and RIS 5 mg/day, 15 mg/day and 50 mg/week from a double blind, multi-centre, placebo-controlled, 2 yr investigation of OA knee patients in North America. Using fluoroscopic semi-flexed standard radiography, baseline and exit knee radiographs were digitized by laser scanner. Following computerized measurement of minimum medial compartment joint space width, each group was subdivided into joint space narrowing (JSN) non-progressor or JSN-progressor (JSN � 0.6 mm measured at any point postbaseline). Computerized method of fractal signature analysis (FSA) quantified longitudinal changes separately in horizontal and vertical Trabeculae in region of interest (three-fourth width of tibial compartment x 6 mm height) in the medial compartment. Following the initial study, all JSN-progressor knees within the entire patient cohort (N ¼ 1232) were similarly analysed. Results. OA knees in JSN non-progressor group had a slight decrease in FSA for vertical and horizontal Trabeculae and showed no drug effect. In JSN-progressor knees, bone loss was greater in both placebo and RIS 5 mg/day groups compared with those in RIS 15 mg/day group in which Trabeculae were retained, and in the RIS 50 mg/week group in which the vertical Trabecular number increased significantly (P < 0.05). Conclusion. This preliminary study showed that patients with marked cartilage loss (JSN� 0.6 mm) receiving RIS 15 mg/day retained vertical Trabecular structure, and those receiving RIS 50 mg/week increased vertical Trabecular number, thereby preserving the structural integrity of subchondral bone in knee OA.
E. A. Messent - One of the best experts on this subject based on the ideXlab platform.
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A 2 yr longitudinal radiographic study examining the effect of a bisphosphonate (risedronate) upon subchondral bone loss in osteoarthritic knee patients
Rheumatology, 2007Co-Authors: Chris J. Buckland-wright, E. A. Messent, C. O. Bingham, R. J. Ward, Charels TonkinAbstract:OBJECTIVES: To determine whether risedronate (RIS) slows down Trabecular bone loss in the medial compartment of the proximal tibia, a characteristic of patients with progressive knee osteoarthritis (OA). METHODS: Initially, 100 patients were randomly selected from each treatment group (each N approximately 300) comprising placebo and RIS 5 mg/day, 15 mg/day and 50 mg/week from a double blind, multi-centre, placebo-controlled, 2 yr investigation of OA knee patients in North America. Using fluoroscopic semi-flexed standard radiography, baseline and exit knee radiographs were digitized by laser scanner. Following computerized measurement of minimum medial compartment joint space width, each group was subdivided into joint space narrowing (JSN) non-progressor or JSN-progressor (JSN >or=0.6 mm measured at any point post-baseline). Computerized method of fractal signature analysis (FSA) quantified longitudinal changes separately in horizontal and vertical Trabeculae in region of interest (three-fourth width of tibial compartment x 6 mm height) in the medial compartment. Following the initial study, all JSN-progressor knees within the entire patient cohort (N = 1232) were similarly analysed. RESULTS: OA knees in JSN non-progressor group had a slight decrease in FSA for vertical and horizontal Trabeculae and showed no drug effect. In JSN-progressor knees, bone loss was greater in both placebo and RIS 5 mg/day groups compared with those in RIS 15 mg/day group in which Trabeculae were retained, and in the RIS 50 mg/week group in which the vertical Trabecular number increased significantly (P < 0.05). CONCLUSION: This preliminary study showed that patients with marked cartilage loss (JSN>or=0.6 mm) receiving RIS 15 mg/day retained vertical Trabecular structure, and those receiving RIS 50 mg/week increased vertical Trabecular number, thereby preserving the structural integrity of subchondral bone in knee OA.
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a 2 yr longitudinal radiographic study examining the effect of a bisphosphonate risedronate upon subchondral bone loss in osteoarthritic knee patients
Rheumatology, 2006Co-Authors: J C Bucklandwright, E. A. Messent, C. O. Bingham, R. J. Ward, Charels TonkinAbstract:Objectives. To determine whether risedronate (RIS) slows down Trabecular bone loss in the medial compartment of the proximal tibia, a characteristic of patients with progressive knee osteoarthritis (OA). Methods. Initially, 100 patients were randomly selected from each treatment group (each N� 300) comprising placebo and RIS 5 mg/day, 15 mg/day and 50 mg/week from a double blind, multi-centre, placebo-controlled, 2 yr investigation of OA knee patients in North America. Using fluoroscopic semi-flexed standard radiography, baseline and exit knee radiographs were digitized by laser scanner. Following computerized measurement of minimum medial compartment joint space width, each group was subdivided into joint space narrowing (JSN) non-progressor or JSN-progressor (JSN � 0.6 mm measured at any point postbaseline). Computerized method of fractal signature analysis (FSA) quantified longitudinal changes separately in horizontal and vertical Trabeculae in region of interest (three-fourth width of tibial compartment x 6 mm height) in the medial compartment. Following the initial study, all JSN-progressor knees within the entire patient cohort (N ¼ 1232) were similarly analysed. Results. OA knees in JSN non-progressor group had a slight decrease in FSA for vertical and horizontal Trabeculae and showed no drug effect. In JSN-progressor knees, bone loss was greater in both placebo and RIS 5 mg/day groups compared with those in RIS 15 mg/day group in which Trabeculae were retained, and in the RIS 50 mg/week group in which the vertical Trabecular number increased significantly (P < 0.05). Conclusion. This preliminary study showed that patients with marked cartilage loss (JSN� 0.6 mm) receiving RIS 15 mg/day retained vertical Trabecular structure, and those receiving RIS 50 mg/week increased vertical Trabecular number, thereby preserving the structural integrity of subchondral bone in knee OA.
C. O. Bingham - One of the best experts on this subject based on the ideXlab platform.
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A 2 yr longitudinal radiographic study examining the effect of a bisphosphonate (risedronate) upon subchondral bone loss in osteoarthritic knee patients
Rheumatology, 2007Co-Authors: Chris J. Buckland-wright, E. A. Messent, C. O. Bingham, R. J. Ward, Charels TonkinAbstract:OBJECTIVES: To determine whether risedronate (RIS) slows down Trabecular bone loss in the medial compartment of the proximal tibia, a characteristic of patients with progressive knee osteoarthritis (OA). METHODS: Initially, 100 patients were randomly selected from each treatment group (each N approximately 300) comprising placebo and RIS 5 mg/day, 15 mg/day and 50 mg/week from a double blind, multi-centre, placebo-controlled, 2 yr investigation of OA knee patients in North America. Using fluoroscopic semi-flexed standard radiography, baseline and exit knee radiographs were digitized by laser scanner. Following computerized measurement of minimum medial compartment joint space width, each group was subdivided into joint space narrowing (JSN) non-progressor or JSN-progressor (JSN >or=0.6 mm measured at any point post-baseline). Computerized method of fractal signature analysis (FSA) quantified longitudinal changes separately in horizontal and vertical Trabeculae in region of interest (three-fourth width of tibial compartment x 6 mm height) in the medial compartment. Following the initial study, all JSN-progressor knees within the entire patient cohort (N = 1232) were similarly analysed. RESULTS: OA knees in JSN non-progressor group had a slight decrease in FSA for vertical and horizontal Trabeculae and showed no drug effect. In JSN-progressor knees, bone loss was greater in both placebo and RIS 5 mg/day groups compared with those in RIS 15 mg/day group in which Trabeculae were retained, and in the RIS 50 mg/week group in which the vertical Trabecular number increased significantly (P < 0.05). CONCLUSION: This preliminary study showed that patients with marked cartilage loss (JSN>or=0.6 mm) receiving RIS 15 mg/day retained vertical Trabecular structure, and those receiving RIS 50 mg/week increased vertical Trabecular number, thereby preserving the structural integrity of subchondral bone in knee OA.
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a 2 yr longitudinal radiographic study examining the effect of a bisphosphonate risedronate upon subchondral bone loss in osteoarthritic knee patients
Rheumatology, 2006Co-Authors: J C Bucklandwright, E. A. Messent, C. O. Bingham, R. J. Ward, Charels TonkinAbstract:Objectives. To determine whether risedronate (RIS) slows down Trabecular bone loss in the medial compartment of the proximal tibia, a characteristic of patients with progressive knee osteoarthritis (OA). Methods. Initially, 100 patients were randomly selected from each treatment group (each N� 300) comprising placebo and RIS 5 mg/day, 15 mg/day and 50 mg/week from a double blind, multi-centre, placebo-controlled, 2 yr investigation of OA knee patients in North America. Using fluoroscopic semi-flexed standard radiography, baseline and exit knee radiographs were digitized by laser scanner. Following computerized measurement of minimum medial compartment joint space width, each group was subdivided into joint space narrowing (JSN) non-progressor or JSN-progressor (JSN � 0.6 mm measured at any point postbaseline). Computerized method of fractal signature analysis (FSA) quantified longitudinal changes separately in horizontal and vertical Trabeculae in region of interest (three-fourth width of tibial compartment x 6 mm height) in the medial compartment. Following the initial study, all JSN-progressor knees within the entire patient cohort (N ¼ 1232) were similarly analysed. Results. OA knees in JSN non-progressor group had a slight decrease in FSA for vertical and horizontal Trabeculae and showed no drug effect. In JSN-progressor knees, bone loss was greater in both placebo and RIS 5 mg/day groups compared with those in RIS 15 mg/day group in which Trabeculae were retained, and in the RIS 50 mg/week group in which the vertical Trabecular number increased significantly (P < 0.05). Conclusion. This preliminary study showed that patients with marked cartilage loss (JSN� 0.6 mm) receiving RIS 15 mg/day retained vertical Trabecular structure, and those receiving RIS 50 mg/week increased vertical Trabecular number, thereby preserving the structural integrity of subchondral bone in knee OA.
R. J. Ward - One of the best experts on this subject based on the ideXlab platform.
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A 2 yr longitudinal radiographic study examining the effect of a bisphosphonate (risedronate) upon subchondral bone loss in osteoarthritic knee patients
Rheumatology, 2007Co-Authors: Chris J. Buckland-wright, E. A. Messent, C. O. Bingham, R. J. Ward, Charels TonkinAbstract:OBJECTIVES: To determine whether risedronate (RIS) slows down Trabecular bone loss in the medial compartment of the proximal tibia, a characteristic of patients with progressive knee osteoarthritis (OA). METHODS: Initially, 100 patients were randomly selected from each treatment group (each N approximately 300) comprising placebo and RIS 5 mg/day, 15 mg/day and 50 mg/week from a double blind, multi-centre, placebo-controlled, 2 yr investigation of OA knee patients in North America. Using fluoroscopic semi-flexed standard radiography, baseline and exit knee radiographs were digitized by laser scanner. Following computerized measurement of minimum medial compartment joint space width, each group was subdivided into joint space narrowing (JSN) non-progressor or JSN-progressor (JSN >or=0.6 mm measured at any point post-baseline). Computerized method of fractal signature analysis (FSA) quantified longitudinal changes separately in horizontal and vertical Trabeculae in region of interest (three-fourth width of tibial compartment x 6 mm height) in the medial compartment. Following the initial study, all JSN-progressor knees within the entire patient cohort (N = 1232) were similarly analysed. RESULTS: OA knees in JSN non-progressor group had a slight decrease in FSA for vertical and horizontal Trabeculae and showed no drug effect. In JSN-progressor knees, bone loss was greater in both placebo and RIS 5 mg/day groups compared with those in RIS 15 mg/day group in which Trabeculae were retained, and in the RIS 50 mg/week group in which the vertical Trabecular number increased significantly (P < 0.05). CONCLUSION: This preliminary study showed that patients with marked cartilage loss (JSN>or=0.6 mm) receiving RIS 15 mg/day retained vertical Trabecular structure, and those receiving RIS 50 mg/week increased vertical Trabecular number, thereby preserving the structural integrity of subchondral bone in knee OA.
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a 2 yr longitudinal radiographic study examining the effect of a bisphosphonate risedronate upon subchondral bone loss in osteoarthritic knee patients
Rheumatology, 2006Co-Authors: J C Bucklandwright, E. A. Messent, C. O. Bingham, R. J. Ward, Charels TonkinAbstract:Objectives. To determine whether risedronate (RIS) slows down Trabecular bone loss in the medial compartment of the proximal tibia, a characteristic of patients with progressive knee osteoarthritis (OA). Methods. Initially, 100 patients were randomly selected from each treatment group (each N� 300) comprising placebo and RIS 5 mg/day, 15 mg/day and 50 mg/week from a double blind, multi-centre, placebo-controlled, 2 yr investigation of OA knee patients in North America. Using fluoroscopic semi-flexed standard radiography, baseline and exit knee radiographs were digitized by laser scanner. Following computerized measurement of minimum medial compartment joint space width, each group was subdivided into joint space narrowing (JSN) non-progressor or JSN-progressor (JSN � 0.6 mm measured at any point postbaseline). Computerized method of fractal signature analysis (FSA) quantified longitudinal changes separately in horizontal and vertical Trabeculae in region of interest (three-fourth width of tibial compartment x 6 mm height) in the medial compartment. Following the initial study, all JSN-progressor knees within the entire patient cohort (N ¼ 1232) were similarly analysed. Results. OA knees in JSN non-progressor group had a slight decrease in FSA for vertical and horizontal Trabeculae and showed no drug effect. In JSN-progressor knees, bone loss was greater in both placebo and RIS 5 mg/day groups compared with those in RIS 15 mg/day group in which Trabeculae were retained, and in the RIS 50 mg/week group in which the vertical Trabecular number increased significantly (P < 0.05). Conclusion. This preliminary study showed that patients with marked cartilage loss (JSN� 0.6 mm) receiving RIS 15 mg/day retained vertical Trabecular structure, and those receiving RIS 50 mg/week increased vertical Trabecular number, thereby preserving the structural integrity of subchondral bone in knee OA.
Rik Huiskes - One of the best experts on this subject based on the ideXlab platform.
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Effects of PTH treatment on tibial bone of ovariectomized rats assessed by in vivo micro-CT
Osteoporosis International, 2009Co-Authors: J. E. M. Brouwers, Bert Van Rietbergen, Rik HuiskesAbstract:Using in vivo microcomputed tomography (micro-CT), we found in parathyroid hormone (PTH)-treated osteopenic rats linear increases in cortical and Trabecular, due to increased Trabecular thickness and number, bone mass. Bone was formed in cavities, leading to restoral of nearly cleaved Trabeculae. For the first time, effects in PTH-treated rats were analyzed longitudinally. Introduction Our aims were to over time (1) determine changes in Trabecular thickness and number after PTH, (2) compare responses to PTH between the meta- and epiphysis, (3) determine effects of PTH on mineralization and mechanical properties, (4) determine locations of new bone formation due to PTH on a microlevel, and (5) determine the predictive value of bone structural properties for gain in bone mass after PTH. Methods Adult rats were divided into ovariectomy (OVX; n = 8), SHAM-OVX ( n = 8), and OVX and PTH treatment ( n = 9). Between weeks 8 and 14, PTH rats received daily subcutaneous PTH injections (60 μg/kg/day). At weeks 0, 8, 10, 12, and 14, in vivo micro-CT scans were made of the proximal and diaphyseal tibia. After sacrifice, all tibiae were tested in three-point bending. Results PTH increased bone volume fraction linearly over time in meta- and epiphysis, accompanied by increased Trabecular thickness in both and increased Trabecular number only in the latter one. CT-estimated mineralization increased in Trabecular and remained constant in cortical bone. Ultimate load and energy were increased and ultimate displacement and stiffness unaltered compared to SHAM rats. For those Trabeculae analyzed, bone was formed initially on places where it was most beneficial for increasing their strength and later on to all surfaces.
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a three dimensional digital image correlation technique for strain measurements in microstructures
Journal of Biomechanics, 2004Co-Authors: E Verhulp, Bert Van Rietbergen, Rik HuiskesAbstract:A three-dimensional digital image correlation technique is presented for strain measurements in open-cell structures such as Trabecular bone. The technique uses high-resolution computed tomography images for displacement measurements in the solid structure. In order to determine the local strain-state within single Trabeculae, a tetrahedronization method is used to fill the solid structure with tetrahedrae. Displacements are calculated at the nodes of the tetrahedrae. The displacement data is subsequently converted to a deformation tensor in each of the tetrahedral element centers with a least-squares estimation method. Because the Trabeculae are represented by a mesh, it is possible to deform this mesh according to the deformation tensor and, at the same time, visualize the calculated local strain in the deformed mesh with a finite element post-processing tool. In this way, the deformation of a single Trabecula from an aluminum foam sample was determined and validated with rendered images of the three-dimensional sample. A precision analysis showed that a rigid translation or rotation does not affect the accuracy. Typical values for the standard deviation in the displacement and strain components are 2.0 μm and 0.01, respectively. Presently, the precision limits the technique to strain measurements beyond the yield strain.
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Effect of mechanical set point of bone cells on mechanical control of Trabecular bone architecture.
Bone, 1998Co-Authors: Margriet G Mullender, Bert Van Rietbergen, Peter Rüegsegger, Rik HuiskesAbstract:The architecture of Trabecular bone is thought to be controlled by mechanosensitive bone cells, where hormones provide a background for their responses to mechanical signals. It has been suggested that, in osteoporosis, this response is hampered by changed hormonal levels, thereby increasing the mechanical set point of the cells, which would lead to bone loss. We have investigated if a temporary increase of the mechanical set point causes deterioration of Trabecular bone architecture, such as seen in osteoporosis. Furthermore, the effects of a changed loading pattern were investigated for the same reason. For this purpose, we used a computer simulation model, which was based on the regulation of bone architecture by mechanosensitive osteocytes. It was found that a temporary shift of the mechanical set point causes no lasting changes in architecture. Although an increase of the mechanical set point induces bone loss, the mechanism of bone loss (Trabecular thinning) differs from what is observed in osteoporosis (loss of whole Trabeculae). Hence, a change of the mechanical set point alone cannot explain bone loss as seen in osteoporosis. On the other hand, the removal of load components in a particular direction resulted in irreversible loss of whole Trabeculae. These results indicate that such temporary changes in loading patterns could be important risk factors for osteoporosis.
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Mechanical stability of Trabecular bone morphology as a measure for osteoporosis
Proceedings of 18th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 1996Co-Authors: H. Weinans, Bert Van Rietbergen, Rik HuiskesAbstract:A new technique for assessing the mechanical stability of Trabecular bone was introduced. This technique uses a full three dimensional reconstruction of a Trabecular bone specimen and a finite element model to calculate the local stress distribution within the Trabeculae. A little bone was artificially removed in the model at highly loaded locations and the changed stress distributions were determined. The changes in these distributions are indicative for the mechanical stability (change in fracture risk) of the Trabecular architecture with respect to small changes in mass. The authors propose that this method can be used to measure the mechanical efficacy of a Trabecular architecture in terms of fracture risk, thereby defining osteoporosis in a quantitative way.
