Kai-nan An - Academia.edu (original) (raw)
Papers by Kai-nan An
Hand Clinics, Feb 1, 1997
Twenty-two fresh cadaver specimens were analyzed using a three-dimensional biplanar roentgenograp... more Twenty-two fresh cadaver specimens were analyzed using a three-dimensional biplanar roentgenographic kinematic technique to quantitate intercarpal motion. The large number of specimens provided substantial power to dramatically optimize the statistical significance of the measurements. It was confirmed that the bones of the distal carpal row behave as a single, functional unit with little intercarpal motion and are directly linked to movement of the third metacarpal. The scaphoid, lunate, and triquetrum exhibit significant "out of plane" motion, noted mainly in relation to the distal row bones. Measurable differences in the kinematics of the proximal row bones, relative to each other, were repeatedly defined.
The Journal of Hand Surgery, Jul 1, 1998
Ten cadaver digits were used to evaluate excursion resistance between a tendon and pulley after c... more Ten cadaver digits were used to evaluate excursion resistance between a tendon and pulley after completing 4 methods of pulley reconstruction (Bunnell's, Kleinert's, Lister's, and Karev's techniques). Five tissues (palmaris longus tendon, extensor digitorum tendon, flexor digitorum superficialis tendon, extensor retinaculum, and volar plate) were used to reconstruct the A2 pulley. Intrasynovial tissue sources (extensor retinaculum, volar plate, and flexor digitorum superficialis tendon) produced less excursion resistance than extrasynovial tissue sources (extensor digitorum tendon and palmaris longus tendon). The models using the extensor retinaculum and volar plate as reconstructive materials produced less excursion resistance than the normal A2 pulley, whereas the models using the palmaris longus tendon produced the highest excursion resistance. Bunnell's technique of pulley reconstruction produced less excursion resistance than Kleinert's technique with all 3 tissues tested. The results of the in vitro study of excursion resistance between the tendon and reconstructed pulley demonstrated that Lister's technique of pulley reconstruction using the extensor retinaculum produced the least resistance to tendon gliding.
Journal of Bone and Joint Surgery, American Volume, Apr 1, 2006
Background: Pathologic changes occur commonly in the subsynovial connective tissue in patients wi... more Background: Pathologic changes occur commonly in the subsynovial connective tissue in patients with carpal tunnel syndrome. The purposes of this study were to investigate the ultrastructural changes of the subsynovial connective tissue in these patients and compare them with the findings in cadaver controls. Methods: The diameter and density of collagen fibrils were measured by transmission electron microscopy in specimens of subsynovial connective tissue from ten patients with idiopathic carpal tunnel syndrome and from ten freshfrozen cadavers of individuals without known symptoms of carpal tunnel syndrome. Results: We noted deformed collagen fibrils with a spiraled appearance in the specimens from the patients. We also observed phagocytosis of elastin fibrils in all of those specimens. These changes were noted only rarely in the cadaver controls. The mean diameter (and standard deviation) of the collagen fibrils was 45.5 ± 8.0 nm in the control group and 54.8 ± 15.2 nm in the patient group (p < 0.05). The mean number of collagen fibrils per 0.04 µm 2 (density) was 201.38 ± 48.88 in the control group and 157.08 ± 54.38 in the patient group (p < 0.05). Conclusions: These ultrastructural findings suggest that subsynovial collagen in patients with carpal tunnel syndrome is structurally different from that in individuals without carpal tunnel syndrome, but the processes resulting in that abnormal morphology remain to be elucidated.
International Journal of Molecular Sciences, Sep 29, 2022
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Academic Radiology, Apr 1, 2014
Rationale and Objectives: Carpal tunnel syndrome (CTS) is the most common peripheral nerve entrap... more Rationale and Objectives: Carpal tunnel syndrome (CTS) is the most common peripheral nerve entrapment syndrome. Strong pinch or grip with wrist flexion has been considered a risk factor for CTS. Studying median nerve displacement during wrist movements may provide useful information about median nerve kinematic changes in CTS patients. The purpose of this study was to evaluate the deformability and mobility of the median nerve in CTS patients compared to healthy subjects. Materials and Methods: Dynamic ultrasound images were obtained in 20 affected wrists of 13 patients with CTS. Results were compared to complementary data obtained from both wrists of 10 healthy subjects reported in a previous study. Initial and final median nerve shape and position were measured and analyzed for six defined wrist movements. The deformation ratios for each movement were defined as the median nerve area, perimeter and circularity of the final position normalized by respective values assessed in the initial position. The median nerve displacement vector and magnitude were also calculated. Results: The deformation ratio for circularity was significant less in CTS patients compared to healthy subjects during wrist flexion (P<0.05). The mean vector of median nerve displacement during wrist flexion was significantly different between CTS patients and healthy subjects (P<0.05). The displacement magnitude of the median nerve was found to be less in CTS patients compared to healthy subjects during most movements, with the exception of wrist extension with fingers extended. Conclusions: CTS Patients differ from normal subjects with regard to mobility and deformability of the median nerve.
Bioengineering, May 17, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Proceedings of SPIE, Mar 12, 2013
It is often necessary to register partial objects in medical imaging. Due to limited FOV, the ent... more It is often necessary to register partial objects in medical imaging. Due to limited FOV, the entirety of an object cannot always be imaged. This study presents a novel application of an existing registration algorithm to this problem. The spin-image algorithm [1] creates pose-invariant representations of global shape with respect to individual mesh vertices. These 'spin-images,' are then compared for two different poses of the same object to establish correspondences and subsequently determine relative orientation of the poses. In this study, the spin-image algorithm is applied to 4DCT-derived capitate bone surfaces to assess the relative accuracy of registration with various amounts of geometry excluded. The limited longitudinal coverage under the 4DCT technique (38.4mm, [2]), results in partial views of the capitate when imaging wrist motions. This study assesses the ability of the spinimage algorithm to register partial bone surfaces by artificially restricting the capitate geometry available for registration. Under IRB approval, standard static CT and 4DCT scans were obtained on a patient. The capitate was segmented from the static CT and one phase of 4DCT in which the whole bone was available. Spin-image registration was performed between the static and 4DCT. Distal portions of the 4DCT capitate (10-70%) were then removed and registration was repeated. Registration accuracy was evaluated by angular errors and the percentage of sub-resolution fitting. It was determined that 60% of the distal capitate could be omitted without appreciable effect on registration accuracy using the spin-image algorithm (angular error < 1.5 degree, sub-resolution fitting > 98.4%).
Journal of Biomechanics, 2011
Carpal Tunnel Syndrome (CTS) is a nerve entrapment disease which has been extensively studied by ... more Carpal Tunnel Syndrome (CTS) is a nerve entrapment disease which has been extensively studied by the engineering and medical community. Although the direct cause is unknown, in vivo and in vitro medical research has shown that tendon excursion creates micro tears in the subsynovial connective tissue (SSCT) surrounding the tendon in the carpal tunnel. One proposed mechanism for the SSCT injury is shearing which is believed to cause fibrosis of the SSCT. Few studies have reported quantitative observations of SSCT response to mechanical loading. Our proposed model is a 2-D section that consists of an FDS tendon, interstitial SSCT and adjacent stationary tendons. We believe that developing this model will allow the most complete quantitative observations of SSCT response to mechanical loading reported thus far. Boundary conditions were applied to the FEA model to simulate single finger flexion. A velocity was applied to the FDS tendon in the model to match loading conditions of the documented cadaver wrist kinematics studies. The cadaveric and FEA displacement results were compared to investigate the magnitude of stiffness required for the SSCT section of the model. The relative motions between the model and cadavers matched more closely than the absolute displacements. Since cadaveric models do not allow identification of the SSCT layers, an FEA model will help determine the displacement and stress experienced by each SSCT layer. Thus, we believe this conceptual model is a first step in understanding how the SSCT layers are recruited during tendon excursion.
Journal of Medical and Biological Engineering
Few studies have described extents of subluxation, applied stresses, and assessing postures durin... more Few studies have described extents of subluxation, applied stresses, and assessing postures during trapeziometacarpal stressview radiography, which probably has led to unsatisfactory reliability of the Eaton classification for determining arthritis. To address this problem, this study examined the effects of applied forces and thumb position on levels of trapeziometacarpal subluxation during stress-view radiography. Thirty-two volunteers allowed our team to quantify their trapeziometacarpal subluxation ratio (TSR) via fluoroscopic images while stress was applied to their thumbs under 3 different positions (Stress_IP, Stress_MP, and Stress_KP). The results were recorded synchronously using a force transducer embedded in a custom stressview evaluation system (SvES). The differences in TSR under different stress levels and thumb positions and the relationships between TSRs and applied stresses on the joint were analyzed. The findings show acceptable reliability and validity with use of the SvES for trapeziometacarpal stress-view tests. There were significant correlations between applied stresses and TSRs (r = 0.8 − 0.989, P < 0.001), and different levels of applied stress significantly contributed to different TSRs. Assessing the thumb in various postures significantly influenced the TSRs and corresponding stresses. Although Stress_KP could produce larger forces, the greater TSRs were found under Stress_IP and Stress_MP conditions. This study clearly indicates relationships among the extents of subluxation, applied stresses, and assessing postures when trapeziometacarpal stress-view radiographs are performed with use of the SvES. These findings might provide information for further clinical or research use and should be useful as a basis for better understanding and precise diagnosis of joint mechanics.
Elasticity imaging phantoms are used to mimic human tissue as a means of testing and validating n... more Elasticity imaging phantoms are used to mimic human tissue as a means of testing and validating non-invasive techniques for measuring mechanical properties of human tissues. Limited studies of phantom stability have shown that phantom stiffness change over time when exposed to air. The goals of this study were to investigate how the physical and mechanical properties of elasticity imaging phantoms change with time and moisture state. Two moisture states were tested; a dry state where the phantom was exposed to open air and a wet state where the phantom was submerged in water for 480 minutes. Polyvinyl alcohol (PVA) phantoms (cylindrical shape) were used. The properties of the phantom were found using flat indentation tests and a test battery that included a precondition test, a 0.05 mm/s triangle test, a 5 mm/s triangle test and a ten-second ramp-and-hold relaxation test. This battery was done at multiple time points: 0, 15, 30, 45, 60, 120, 180, 240, 360 and 480 minutes. At each ti...
PLOS ONE, 2015
<p>Radiograph of fractured spine in L1 reveals SSPI+TEPPS instrumentation. Left, Lateral vi... more <p>Radiograph of fractured spine in L1 reveals SSPI+TEPPS instrumentation. Left, Lateral view shows the upper endplate pillar (1a) with its connector (2a) and the lower endplate pillar (1b) with its connector (2b). Right, Anteroposterior view shows the upper endplate pillar (1a) with its connector (2a) and the lower endplate pillar (1b) with its connector (2b).</p
PLOS ONE, 2015
<p>Mean peak moment applied to pedicle screws during flexion and lateral bending. Asterisk ... more <p>Mean peak moment applied to pedicle screws during flexion and lateral bending. Asterisk (*) indicates a significant difference from intact spine (<i>P</i> < .001). For expansion of abbreviations, see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0139592#pone.0139592.g007" target="_blank">Fig 7</a> legend.</p
Orthopaedic Journal of Sports Medicine, 2019
Aim: Compare the effect of Latarjet and Trillat procedures on glenohumeral stability and range of... more Aim: Compare the effect of Latarjet and Trillat procedures on glenohumeral stability and range of motion. Background: Little is known about the impact of the location of the sling effect on joint stability and range of motion. Methods: 12 cadaveric shoulders were cleaned of soft tissue except for the subscapularis, conjoined tendon, and anterior capsule. A custom-made apparatus generating anterior humeral translation and joint compression was used. The machine applied compression load in the medial direction. The subscapularis and conjoint tendon were loaded. Internal/external range of motion and joint stability were assessed at 0°, 30° and 60° glenohumeral abduction. Range of motion was assessed by rotating the humeral shaft. Joint stability was assessed at maximum external rotation, translating the humerus. Specimen were tested in five conditions: 1) intact shoulder, 2) 6-mm bony glenoid defect (20% defect) 3) Trillat procedure, 4) Latarjet procedure with subscapularis split at th...
Revue de Chirurgie Orthopédique et Traumatologique, 2018
Introduction Peu de choses sont connues sur l’effet de la localisation de l’effet hamac sur la st... more Introduction Peu de choses sont connues sur l’effet de la localisation de l’effet hamac sur la stabilite et la mobilite de l’articulation glenohumerale. Le but de cette etude biomecanique etait de comparer l’effet du tendon conjoint dans les interventions de Latarjet et de Trillat sur la stabilite et la mobilite glenohumerale. Materiel et methode Douze epaules cadaveriques ont ete utilisees dans cette etude. L’ensemble des tissus mous ont ete retires, si ce n’est le sous-scapulaire, le tendon conjoint et la capsule anterieure. Un systeme developpe specifiquement a ete mis en place permettant de realiser une translation anterieure de la tete humerale ainsi qu’une compression au niveau de l’articulation. Le sous-scapulaire et le tendon conjoint ont ete charges afin d’etudier l’effet de la contraction musculaire. Le degre de mobilite interne et externe de l’articulation et sa stabilite ont ete evalues 0–30 et 60° d’abduction. La mobilite etait evaluee en faisant des rotations au niveau de la diaphyse humerale, la stabilite a ete evaluee en rotation externe maximum, translation anterieure de la tete humerale. Les pieces anatomiques ont ete etudiees dans 5 conditions : – une epaule intacte ; – creation d’un defect de 6 mm au niveau de la glene (20 %) ; – intervention de Trillat ; – intervention de Latarjet avec un split du sous-scapulaire a la jonction tiers moyen-tiers superieur ; – intervention de Latarjet avec split du sous-scapulaire a la jonction tiers moyen, tiers inferieur. L’ensemble des mesures ont ete realisees 3 fois et analysees en les comparant les unes avec les autres de manieres statistiques. Resultat Les ratios de stabilites et la force necessaire a la luxation et etaient significativement les plus faibles dans le modele de defect osseux de la glene compare a toutes les autres positions de stabilites. Le niveau de localisation du split du sous-scapulaire n’a pas d’influence significative sur ces valeurs et aucune difference n’a pu etre retrouvee entre l’intervention de Trillat ou de Latarjet, quelle que soit sa position. Aucune difference n’a non plus ete retrouvee sur les limitations de rotation interne et rotation externe quelle que soit la technique de stabilisation realisee. Conclusion La stabilite articulaire et la mobilite articulaire ne sont pas modifiees par la localisation de l’effet hamac dans les interventions de Latarjet et Trillat. Ces deux techniques permettent d’obtenir une stabilisation de meme efficacite, meme lorsqu’il existe un defect glenoidien de 20 %.
Juntendo Medical Journal, 2015
Biomechanics is the study of the structure and function of biological mechanics. I went abroad to... more Biomechanics is the study of the structure and function of biological mechanics. I went abroad to the Mayo Clinic to learn biomechanics, and participated in the following research. Because the prediction of rotator cuff extensibility is clinically important for pre-surgical planning for rotator cuff repair, we determined the feasibility of B-mode ultrasound and Shear Wave Elastography (SWE) in predicting the extensibility of the rotator cuff muscle on cadaveric specimens with cuff tears of varying sizes. Eleven fresh frozen cadaveric shoulders were obtained, and the size of the rotator cuff tears was determined as follows: small, medium, large, massive, and intact/no tear. After the SWE modulus of the superficial and deep muscles was measured, the force applied to the supraspinatus tendon and displacement were recorded while the supraspinatus tendon was axially stretched. A regression analysis was preformed to investigate the association between tendon displacement and SWE modulus. There was a significant negative correlation between the displacement of the supraspinatus tendon and the SWE modulus of the superficial and deep muscles. SWE ultrasound may predict the extensibility of the supraspinatus musculotendinous unit, independent of the size of the supraspinatus tendon.
Advances in the Biomechanics of the Hand and Wrist, 1994
The scapholunate interosseous ligament normally connects the scaphoid and lunate carpal bones by ... more The scapholunate interosseous ligament normally connects the scaphoid and lunate carpal bones by spanning the proximal, dorsal and palmar margins of the scapholunate joint. It has been felt to be a critical structure for maintaining structural integrity within the proximal carpal row, and thus important in maintaining normal carpal mechanics.1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21 Complete disruption of the scapholunate ligament has been associated with a clinical condition of instability termed dorsal intercalated segmental instability (DISI), which is felt to be a precursor of advancing degenerative disease,11 but there is no clear concensus regarding the effects of partial scapholunate ligament disruption. In the laboratory, efforts have been made to study the kinematic influences of this ligament, however conflicting results have been published.2,18 Previous anatomic investigations have revealed the complexity of the interface between the scapholunate and radioscapholunate ligaments, but specific investigations of the scapholunate ligament anatomy have not been published.3 Additionally, material property studies have been carried out on the scapholunate ligament in two published studies.13,16 In both studies, distraction to failure was applied to the entire ligament, which may not represent physiologic failure. In order to obtain a better understanding of the role of the scapholunate ligament on the mechanics of the wrist and the relative contributions of the anatomic subregions of the ligament, we designed an investigation to evaluate the detailed gross and histologic anatomy and mechanical properties of the subregions of the scapholunate interosseous ligament.
Journal of Biomechanics, 2015
In this paper, we model a simplified glenohumeral joint as a cam-follower mechanism during experi... more In this paper, we model a simplified glenohumeral joint as a cam-follower mechanism during experimental simulated dislocation. Thus, humeral head trajectory and translational forces are predicted using only contact surface geometry and compressive forces as function inputs. We demonstrate this new interpretation of glenohumeral stability and verify the accuracy of the method by physically testing a custom-molded, idealized shoulder model and comparing data to the output of the 2D mathematical model. Comparison of translational forces between experimental and mathematical approaches resulted in r(2) of 0.88 and 0.90 for the small and large humeral head sizes, respectively. Comparison of the lateral displacement resulted in r(2) of 0.99 and 0.98 for the small and larger humeral head sizes, respectively. Comparing translational forces between experiments and the mathematical model when varying the compressive force to 30N, 60N, and 90N resulted in r(2) of 0.90, 0.82, and 0.89, respectively. The preliminary success of this study is motivation to introduce the effects of soft tissue such as cartilage and validation with a cadaver model. The use of simple mathematical models such as this aid in the set-up and understanding of experiments in stability research and avoid unnecessary depletion of cadaveric resources.
Functional Tissue Engineering
Hand Clinics, Feb 1, 1997
Twenty-two fresh cadaver specimens were analyzed using a three-dimensional biplanar roentgenograp... more Twenty-two fresh cadaver specimens were analyzed using a three-dimensional biplanar roentgenographic kinematic technique to quantitate intercarpal motion. The large number of specimens provided substantial power to dramatically optimize the statistical significance of the measurements. It was confirmed that the bones of the distal carpal row behave as a single, functional unit with little intercarpal motion and are directly linked to movement of the third metacarpal. The scaphoid, lunate, and triquetrum exhibit significant "out of plane" motion, noted mainly in relation to the distal row bones. Measurable differences in the kinematics of the proximal row bones, relative to each other, were repeatedly defined.
The Journal of Hand Surgery, Jul 1, 1998
Ten cadaver digits were used to evaluate excursion resistance between a tendon and pulley after c... more Ten cadaver digits were used to evaluate excursion resistance between a tendon and pulley after completing 4 methods of pulley reconstruction (Bunnell&amp;#39;s, Kleinert&amp;#39;s, Lister&amp;#39;s, and Karev&amp;#39;s techniques). Five tissues (palmaris longus tendon, extensor digitorum tendon, flexor digitorum superficialis tendon, extensor retinaculum, and volar plate) were used to reconstruct the A2 pulley. Intrasynovial tissue sources (extensor retinaculum, volar plate, and flexor digitorum superficialis tendon) produced less excursion resistance than extrasynovial tissue sources (extensor digitorum tendon and palmaris longus tendon). The models using the extensor retinaculum and volar plate as reconstructive materials produced less excursion resistance than the normal A2 pulley, whereas the models using the palmaris longus tendon produced the highest excursion resistance. Bunnell&amp;#39;s technique of pulley reconstruction produced less excursion resistance than Kleinert&amp;#39;s technique with all 3 tissues tested. The results of the in vitro study of excursion resistance between the tendon and reconstructed pulley demonstrated that Lister&amp;#39;s technique of pulley reconstruction using the extensor retinaculum produced the least resistance to tendon gliding.
Journal of Bone and Joint Surgery, American Volume, Apr 1, 2006
Background: Pathologic changes occur commonly in the subsynovial connective tissue in patients wi... more Background: Pathologic changes occur commonly in the subsynovial connective tissue in patients with carpal tunnel syndrome. The purposes of this study were to investigate the ultrastructural changes of the subsynovial connective tissue in these patients and compare them with the findings in cadaver controls. Methods: The diameter and density of collagen fibrils were measured by transmission electron microscopy in specimens of subsynovial connective tissue from ten patients with idiopathic carpal tunnel syndrome and from ten freshfrozen cadavers of individuals without known symptoms of carpal tunnel syndrome. Results: We noted deformed collagen fibrils with a spiraled appearance in the specimens from the patients. We also observed phagocytosis of elastin fibrils in all of those specimens. These changes were noted only rarely in the cadaver controls. The mean diameter (and standard deviation) of the collagen fibrils was 45.5 ± 8.0 nm in the control group and 54.8 ± 15.2 nm in the patient group (p < 0.05). The mean number of collagen fibrils per 0.04 µm 2 (density) was 201.38 ± 48.88 in the control group and 157.08 ± 54.38 in the patient group (p < 0.05). Conclusions: These ultrastructural findings suggest that subsynovial collagen in patients with carpal tunnel syndrome is structurally different from that in individuals without carpal tunnel syndrome, but the processes resulting in that abnormal morphology remain to be elucidated.
International Journal of Molecular Sciences, Sep 29, 2022
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Academic Radiology, Apr 1, 2014
Rationale and Objectives: Carpal tunnel syndrome (CTS) is the most common peripheral nerve entrap... more Rationale and Objectives: Carpal tunnel syndrome (CTS) is the most common peripheral nerve entrapment syndrome. Strong pinch or grip with wrist flexion has been considered a risk factor for CTS. Studying median nerve displacement during wrist movements may provide useful information about median nerve kinematic changes in CTS patients. The purpose of this study was to evaluate the deformability and mobility of the median nerve in CTS patients compared to healthy subjects. Materials and Methods: Dynamic ultrasound images were obtained in 20 affected wrists of 13 patients with CTS. Results were compared to complementary data obtained from both wrists of 10 healthy subjects reported in a previous study. Initial and final median nerve shape and position were measured and analyzed for six defined wrist movements. The deformation ratios for each movement were defined as the median nerve area, perimeter and circularity of the final position normalized by respective values assessed in the initial position. The median nerve displacement vector and magnitude were also calculated. Results: The deformation ratio for circularity was significant less in CTS patients compared to healthy subjects during wrist flexion (P<0.05). The mean vector of median nerve displacement during wrist flexion was significantly different between CTS patients and healthy subjects (P<0.05). The displacement magnitude of the median nerve was found to be less in CTS patients compared to healthy subjects during most movements, with the exception of wrist extension with fingers extended. Conclusions: CTS Patients differ from normal subjects with regard to mobility and deformability of the median nerve.
Bioengineering, May 17, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Proceedings of SPIE, Mar 12, 2013
It is often necessary to register partial objects in medical imaging. Due to limited FOV, the ent... more It is often necessary to register partial objects in medical imaging. Due to limited FOV, the entirety of an object cannot always be imaged. This study presents a novel application of an existing registration algorithm to this problem. The spin-image algorithm [1] creates pose-invariant representations of global shape with respect to individual mesh vertices. These 'spin-images,' are then compared for two different poses of the same object to establish correspondences and subsequently determine relative orientation of the poses. In this study, the spin-image algorithm is applied to 4DCT-derived capitate bone surfaces to assess the relative accuracy of registration with various amounts of geometry excluded. The limited longitudinal coverage under the 4DCT technique (38.4mm, [2]), results in partial views of the capitate when imaging wrist motions. This study assesses the ability of the spinimage algorithm to register partial bone surfaces by artificially restricting the capitate geometry available for registration. Under IRB approval, standard static CT and 4DCT scans were obtained on a patient. The capitate was segmented from the static CT and one phase of 4DCT in which the whole bone was available. Spin-image registration was performed between the static and 4DCT. Distal portions of the 4DCT capitate (10-70%) were then removed and registration was repeated. Registration accuracy was evaluated by angular errors and the percentage of sub-resolution fitting. It was determined that 60% of the distal capitate could be omitted without appreciable effect on registration accuracy using the spin-image algorithm (angular error < 1.5 degree, sub-resolution fitting > 98.4%).
Journal of Biomechanics, 2011
Carpal Tunnel Syndrome (CTS) is a nerve entrapment disease which has been extensively studied by ... more Carpal Tunnel Syndrome (CTS) is a nerve entrapment disease which has been extensively studied by the engineering and medical community. Although the direct cause is unknown, in vivo and in vitro medical research has shown that tendon excursion creates micro tears in the subsynovial connective tissue (SSCT) surrounding the tendon in the carpal tunnel. One proposed mechanism for the SSCT injury is shearing which is believed to cause fibrosis of the SSCT. Few studies have reported quantitative observations of SSCT response to mechanical loading. Our proposed model is a 2-D section that consists of an FDS tendon, interstitial SSCT and adjacent stationary tendons. We believe that developing this model will allow the most complete quantitative observations of SSCT response to mechanical loading reported thus far. Boundary conditions were applied to the FEA model to simulate single finger flexion. A velocity was applied to the FDS tendon in the model to match loading conditions of the documented cadaver wrist kinematics studies. The cadaveric and FEA displacement results were compared to investigate the magnitude of stiffness required for the SSCT section of the model. The relative motions between the model and cadavers matched more closely than the absolute displacements. Since cadaveric models do not allow identification of the SSCT layers, an FEA model will help determine the displacement and stress experienced by each SSCT layer. Thus, we believe this conceptual model is a first step in understanding how the SSCT layers are recruited during tendon excursion.
Journal of Medical and Biological Engineering
Few studies have described extents of subluxation, applied stresses, and assessing postures durin... more Few studies have described extents of subluxation, applied stresses, and assessing postures during trapeziometacarpal stressview radiography, which probably has led to unsatisfactory reliability of the Eaton classification for determining arthritis. To address this problem, this study examined the effects of applied forces and thumb position on levels of trapeziometacarpal subluxation during stress-view radiography. Thirty-two volunteers allowed our team to quantify their trapeziometacarpal subluxation ratio (TSR) via fluoroscopic images while stress was applied to their thumbs under 3 different positions (Stress_IP, Stress_MP, and Stress_KP). The results were recorded synchronously using a force transducer embedded in a custom stressview evaluation system (SvES). The differences in TSR under different stress levels and thumb positions and the relationships between TSRs and applied stresses on the joint were analyzed. The findings show acceptable reliability and validity with use of the SvES for trapeziometacarpal stress-view tests. There were significant correlations between applied stresses and TSRs (r = 0.8 − 0.989, P < 0.001), and different levels of applied stress significantly contributed to different TSRs. Assessing the thumb in various postures significantly influenced the TSRs and corresponding stresses. Although Stress_KP could produce larger forces, the greater TSRs were found under Stress_IP and Stress_MP conditions. This study clearly indicates relationships among the extents of subluxation, applied stresses, and assessing postures when trapeziometacarpal stress-view radiographs are performed with use of the SvES. These findings might provide information for further clinical or research use and should be useful as a basis for better understanding and precise diagnosis of joint mechanics.
Elasticity imaging phantoms are used to mimic human tissue as a means of testing and validating n... more Elasticity imaging phantoms are used to mimic human tissue as a means of testing and validating non-invasive techniques for measuring mechanical properties of human tissues. Limited studies of phantom stability have shown that phantom stiffness change over time when exposed to air. The goals of this study were to investigate how the physical and mechanical properties of elasticity imaging phantoms change with time and moisture state. Two moisture states were tested; a dry state where the phantom was exposed to open air and a wet state where the phantom was submerged in water for 480 minutes. Polyvinyl alcohol (PVA) phantoms (cylindrical shape) were used. The properties of the phantom were found using flat indentation tests and a test battery that included a precondition test, a 0.05 mm/s triangle test, a 5 mm/s triangle test and a ten-second ramp-and-hold relaxation test. This battery was done at multiple time points: 0, 15, 30, 45, 60, 120, 180, 240, 360 and 480 minutes. At each ti...
PLOS ONE, 2015
<p>Radiograph of fractured spine in L1 reveals SSPI+TEPPS instrumentation. Left, Lateral vi... more <p>Radiograph of fractured spine in L1 reveals SSPI+TEPPS instrumentation. Left, Lateral view shows the upper endplate pillar (1a) with its connector (2a) and the lower endplate pillar (1b) with its connector (2b). Right, Anteroposterior view shows the upper endplate pillar (1a) with its connector (2a) and the lower endplate pillar (1b) with its connector (2b).</p
PLOS ONE, 2015
<p>Mean peak moment applied to pedicle screws during flexion and lateral bending. Asterisk ... more <p>Mean peak moment applied to pedicle screws during flexion and lateral bending. Asterisk (*) indicates a significant difference from intact spine (<i>P</i> < .001). For expansion of abbreviations, see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0139592#pone.0139592.g007" target="_blank">Fig 7</a> legend.</p
Orthopaedic Journal of Sports Medicine, 2019
Aim: Compare the effect of Latarjet and Trillat procedures on glenohumeral stability and range of... more Aim: Compare the effect of Latarjet and Trillat procedures on glenohumeral stability and range of motion. Background: Little is known about the impact of the location of the sling effect on joint stability and range of motion. Methods: 12 cadaveric shoulders were cleaned of soft tissue except for the subscapularis, conjoined tendon, and anterior capsule. A custom-made apparatus generating anterior humeral translation and joint compression was used. The machine applied compression load in the medial direction. The subscapularis and conjoint tendon were loaded. Internal/external range of motion and joint stability were assessed at 0°, 30° and 60° glenohumeral abduction. Range of motion was assessed by rotating the humeral shaft. Joint stability was assessed at maximum external rotation, translating the humerus. Specimen were tested in five conditions: 1) intact shoulder, 2) 6-mm bony glenoid defect (20% defect) 3) Trillat procedure, 4) Latarjet procedure with subscapularis split at th...
Revue de Chirurgie Orthopédique et Traumatologique, 2018
Introduction Peu de choses sont connues sur l’effet de la localisation de l’effet hamac sur la st... more Introduction Peu de choses sont connues sur l’effet de la localisation de l’effet hamac sur la stabilite et la mobilite de l’articulation glenohumerale. Le but de cette etude biomecanique etait de comparer l’effet du tendon conjoint dans les interventions de Latarjet et de Trillat sur la stabilite et la mobilite glenohumerale. Materiel et methode Douze epaules cadaveriques ont ete utilisees dans cette etude. L’ensemble des tissus mous ont ete retires, si ce n’est le sous-scapulaire, le tendon conjoint et la capsule anterieure. Un systeme developpe specifiquement a ete mis en place permettant de realiser une translation anterieure de la tete humerale ainsi qu’une compression au niveau de l’articulation. Le sous-scapulaire et le tendon conjoint ont ete charges afin d’etudier l’effet de la contraction musculaire. Le degre de mobilite interne et externe de l’articulation et sa stabilite ont ete evalues 0–30 et 60° d’abduction. La mobilite etait evaluee en faisant des rotations au niveau de la diaphyse humerale, la stabilite a ete evaluee en rotation externe maximum, translation anterieure de la tete humerale. Les pieces anatomiques ont ete etudiees dans 5 conditions : – une epaule intacte ; – creation d’un defect de 6 mm au niveau de la glene (20 %) ; – intervention de Trillat ; – intervention de Latarjet avec un split du sous-scapulaire a la jonction tiers moyen-tiers superieur ; – intervention de Latarjet avec split du sous-scapulaire a la jonction tiers moyen, tiers inferieur. L’ensemble des mesures ont ete realisees 3 fois et analysees en les comparant les unes avec les autres de manieres statistiques. Resultat Les ratios de stabilites et la force necessaire a la luxation et etaient significativement les plus faibles dans le modele de defect osseux de la glene compare a toutes les autres positions de stabilites. Le niveau de localisation du split du sous-scapulaire n’a pas d’influence significative sur ces valeurs et aucune difference n’a pu etre retrouvee entre l’intervention de Trillat ou de Latarjet, quelle que soit sa position. Aucune difference n’a non plus ete retrouvee sur les limitations de rotation interne et rotation externe quelle que soit la technique de stabilisation realisee. Conclusion La stabilite articulaire et la mobilite articulaire ne sont pas modifiees par la localisation de l’effet hamac dans les interventions de Latarjet et Trillat. Ces deux techniques permettent d’obtenir une stabilisation de meme efficacite, meme lorsqu’il existe un defect glenoidien de 20 %.
Juntendo Medical Journal, 2015
Biomechanics is the study of the structure and function of biological mechanics. I went abroad to... more Biomechanics is the study of the structure and function of biological mechanics. I went abroad to the Mayo Clinic to learn biomechanics, and participated in the following research. Because the prediction of rotator cuff extensibility is clinically important for pre-surgical planning for rotator cuff repair, we determined the feasibility of B-mode ultrasound and Shear Wave Elastography (SWE) in predicting the extensibility of the rotator cuff muscle on cadaveric specimens with cuff tears of varying sizes. Eleven fresh frozen cadaveric shoulders were obtained, and the size of the rotator cuff tears was determined as follows: small, medium, large, massive, and intact/no tear. After the SWE modulus of the superficial and deep muscles was measured, the force applied to the supraspinatus tendon and displacement were recorded while the supraspinatus tendon was axially stretched. A regression analysis was preformed to investigate the association between tendon displacement and SWE modulus. There was a significant negative correlation between the displacement of the supraspinatus tendon and the SWE modulus of the superficial and deep muscles. SWE ultrasound may predict the extensibility of the supraspinatus musculotendinous unit, independent of the size of the supraspinatus tendon.
Advances in the Biomechanics of the Hand and Wrist, 1994
The scapholunate interosseous ligament normally connects the scaphoid and lunate carpal bones by ... more The scapholunate interosseous ligament normally connects the scaphoid and lunate carpal bones by spanning the proximal, dorsal and palmar margins of the scapholunate joint. It has been felt to be a critical structure for maintaining structural integrity within the proximal carpal row, and thus important in maintaining normal carpal mechanics.1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21 Complete disruption of the scapholunate ligament has been associated with a clinical condition of instability termed dorsal intercalated segmental instability (DISI), which is felt to be a precursor of advancing degenerative disease,11 but there is no clear concensus regarding the effects of partial scapholunate ligament disruption. In the laboratory, efforts have been made to study the kinematic influences of this ligament, however conflicting results have been published.2,18 Previous anatomic investigations have revealed the complexity of the interface between the scapholunate and radioscapholunate ligaments, but specific investigations of the scapholunate ligament anatomy have not been published.3 Additionally, material property studies have been carried out on the scapholunate ligament in two published studies.13,16 In both studies, distraction to failure was applied to the entire ligament, which may not represent physiologic failure. In order to obtain a better understanding of the role of the scapholunate ligament on the mechanics of the wrist and the relative contributions of the anatomic subregions of the ligament, we designed an investigation to evaluate the detailed gross and histologic anatomy and mechanical properties of the subregions of the scapholunate interosseous ligament.
Journal of Biomechanics, 2015
In this paper, we model a simplified glenohumeral joint as a cam-follower mechanism during experi... more In this paper, we model a simplified glenohumeral joint as a cam-follower mechanism during experimental simulated dislocation. Thus, humeral head trajectory and translational forces are predicted using only contact surface geometry and compressive forces as function inputs. We demonstrate this new interpretation of glenohumeral stability and verify the accuracy of the method by physically testing a custom-molded, idealized shoulder model and comparing data to the output of the 2D mathematical model. Comparison of translational forces between experimental and mathematical approaches resulted in r(2) of 0.88 and 0.90 for the small and large humeral head sizes, respectively. Comparison of the lateral displacement resulted in r(2) of 0.99 and 0.98 for the small and larger humeral head sizes, respectively. Comparing translational forces between experiments and the mathematical model when varying the compressive force to 30N, 60N, and 90N resulted in r(2) of 0.90, 0.82, and 0.89, respectively. The preliminary success of this study is motivation to introduce the effects of soft tissue such as cartilage and validation with a cadaver model. The use of simple mathematical models such as this aid in the set-up and understanding of experiments in stability research and avoid unnecessary depletion of cadaveric resources.
Functional Tissue Engineering