- Email: [email protected]
Carpal tunnel syndrome—The role of the subsynovial connective tissue
$64
Journal of Biomechanics 2006, Vol. 39 (Suppl 1)
a combined computational and experimental methodology with a non-linear constitutive equation. Rectangular tissue samples (25 25mm 2) were excised from the axillary pouch and posterior region of the glenohumeral capsule of three fresh-frozen cadaveric shoulders and subjected to shear loading. Each tissue sample was tested parallel to the long axis of the anterior band of the inferior glenohumeral ligament (AB-IGHL). The forces and clamp displacements were input as boundary conditions to specimen-specific finite element models to simulate each experimental test. The glenohumeral capsule was represented with a hyperelastic isotropic constitutive model. Results demonstrated that there were no significant differences (p=0.45) between the average shear moduli of the axillary pouch and posterior regions when the tissue samples were loaded in shear, parallel to the long axis of the AB-IGHL. These results show greater similarities between regions of the glenohumeral capsule, as compared to prior studies. This may be attributed to the fact that this methodology analyzes both the toe region and linear region of the stress-strain curve, whereas other methodologies only analyzed the linear region. Therefore, the material properties and function of the axillary pouch and posterior capsule may be more similar than previously thought. References [1] Debski RE. JOR 1999; 17(5): 769-76.
6477 Tu, 11:30-11:45 (P18) The viscoelastic properties of human hamstring tendons X. Zhang, M. Curran, S.D. Abramowitch, S.L-'~ Woo. Musculoskeletal
Research Center, Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA Introduction: Fifty percent of anterior cruciate ligament (ACL) reconstructions use semitendinosus and gracilis tendons as autografts. Quantitative data on the viscoelastic behaviors of these tendons can aid clinicians in graft selection. The objective of this study was to investigate the difference of viscoelastic properties of semitendinosus and gracilis tendons, and variation of these properties along their length. Methods: The semitendinosus and gracilis tendons were obtained from ten fresh-frozen cadaveric knees (55.6±8.1 years) and separated into proximal and distal halves. Each half was cut into a dog-bone shape with an aspect ratio of 10 (width: 3 mm). Specimens underwent a lhr static stress relaxation test (at ~>2% strain), lhr of recovery, and a cyclic stress relaxation test (30 cycles). The QLV theory of professor Fung [1] was utilized to model the static stress relaxation data. The five constants (A,B,C,'r 1,'r2) were obtained by curvefitting the entire strain history [2], and validated by predicting the results of the cyclic stress relaxation test. The constants were then compared using a paired t-test (p < 0.025 due to a Bonferroni adjustment for multiple comparisons). Results: It was found that the viscoelastic properties of gracilis tendon was relatively uniform along its length (p >0.05). The proximal half of semitendinosus tendon, however, dissipated more energy (constant C: 0.083±0.031 vs. 0.051 ±0.017), which corresponded to a greater percentage of stress relaxation compared to its distal half. Comparison between tendons revealed that the proximal half of semitendinosus tendon had a smaller initial slope of the stressstrain curve (AxB: 163.3±88.2 MPa vs. 251.5±112.0 MPa) and dissipated more energy than that of gracilis tendon (constant C: 0.054±0.021). There were no significant differences detected for nonlinearity (B), or constants governing early and late relaxation ('r 1,'r2). Discussion: Nonhomogeneous viscoelastic properties were found along the length of the semitendinosus tendon, which may be attributed to the longer portion of the semitendinosus tendon residing in the musculotendinous junction compared to the gracilis tendon. References [1] Fung. Biomechanics 1972; 181-208. [2] Abramowitch and Woo. JBME 2004; 126: 92-97.
4381 Mo, 16:00-16:15 (P12) Carpal tunnel s y n d r o m e - The role of the subsynovial connective tissue P.C. Amadio, A.M. Ettema, K.-N. An, C. Zhao, L.E. Wold, J. Oh, S. Oh.
Orthopedics Biomechanics Laboratory, Mayo Clinic, Rochester, MN, USA Carpal tunnel syndrome (CTS) is the most common compression neuropathy, yet the cause of the compression is in most cases idiopathic. The most common clinical finding associated with the nerve compression is non-inflammatory fibrosis of the subsynovial connective tissue (SSCT) which surrounds the flexor tendons in the carpal canal. The normal SSCT has a multi-layer gliding mechanism, reminiscent of a series of sleeves around the tendon, with each successive sleeve being connected to its neighbors with fine collagenous fibers. We have conducted a series of experiments which have outlined the pathology, kinematics and material properties of the SSCT in normal individuals and in individuals with CTS, and have identified specific features within the SSCT of individuals with CTS that suggest that injury to the SSCT
Oral Presentations may play a role in the etiology of CTS. Specifically, we have identified evidence of a shearing injury of the SSCT, with fibrosis, and obliteration of the gliding, sleeve-like mechanism, being greatest close to the tendon, and with greater degrees of fibrosis being observed in more severe cases of CTS. This fibrosis is associated with tethering of the SSCT to the underlying tendon, which may increase the work of finger movement in patients with CTS, and impair differential finger movement. Based on these observations, we propose a vicious cycle of SSCT injury and repair as a working hypothesis of the etiology of CTS, and have developed a rabbit model to test this hypothesis in vivo. 5408 Tu, 12:00-12:15 (P18) Ultrasound palpation sensor for the measurement of tissue thickness and elasticity of transverse carpal ligament '~P. Zheng 1, Z.M. Li 2, A.P.C. Choi 1, M.H. Lu 1, Q.H. Huang 1. 1Department of
Health Technology and Informatics, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR, China, 2Hand Research Laboratory, Department of Orthopaedics, University of Pittsburgh, USA One of the symptoms of carpal tunnel syndrome is the stiffening of the carpal tunnel region. Traditional manual palpation has been used in the clinical practise for the assessment of the tunnel stiffness, but in a qualitative and subjective manner. Recently, some investigators have introduced various indentation methods to make objective and quantitative measurement for the tissues at the carpal tunnel region. However, both manual palpation and traditional indentation could not differentiate the stiffness of the tunnel from the soft tissues covering the tunnel. Tissue ultrasound palpation sensor (TUPS) [1] can provide a feasible solution for quantitative and objective measurement of tissue stiffness not only for a single tissue block but also for tissues with multiple layers. TUPS is comprised of an ultrasound transducer together with a load cell to form the finger-sized probe. The probe is used to push against the soft tissue surface to measure the thickness and elasticity of the soft tissues. TUPS has been successfully applied to the assessment of various human tissues. Recently, we have improved TUPS, which can now be linked to personal computer (PC) via universal serial bus (USB) and provide a better user-interface. In this paper, we introduce the recent application of TUPS for the assessment of the transverse carpal ligament and other tissues. The tissues at the carpal tunnel regions of five normal male subjects were tested using TUPS. The results showed that the average thickness of the tissues covering the carpal tunnel ligament and the tunnel region was 7.98±1.05mm and 9.59±1.12mm, respectively. Under a compression force of 20N applied by a cylindrical ultrasound indentor with a diameter of 9 mm, the stiffness of the soft tissue layer and the tunnel region was 6.72±2.10 N/mm and 15.63±8.42 N/mm, respectively. It is expected that TUPS can be a potential tool for non-invasive assessment of carpal tunnel syndrome. References [1] Zheng YP, Mak AFT. An ultrasound indentation system for biomechanical properties assessment of soft tissues in-vivo. IEEE Transactions on Biomedical Engineering 1996; 43(9): 912-918.
4530 Tu, 12:15-12:30 (P18) Non-invasive strain measurements of ligaments and tendons via acoustoelastic analysis of ultrasonic waves R. Vanderby, H. Kobayashi. Dept. of Orthopedics and Rehabilitation,
University of Wisconsin-Madison, Wisconsin, USA Many techniques have been proposed to measured in-vivo strain in ligaments and tendons [1]. Most, however, are invasive and require the surgical implantation of a measurement gauge. Others are non-invasive but they require a relatively large system that is not practical for strain measurements in the field. Acoustoelasticity (AE) is a theory that describes changes in acoustic characteristics when a medium is deformed due to its strain dependent stiffness. AE has been intensively studied in engineering materials [2]. More recently, AE has been observed in biological tissues that are nearly incompressible and can sustain large nonlinear deformations [3,4]. The studies however failed to describe the phenomenon within the framework of AE, in part because they assumed tissue incompressibility. In the present study, we use AE theory to develop a non-invasive method to measure functional tissue strain. We therefore developed rigorous AE analysis for nearly incompressible materials including biological tissues [5,6]. We also developed novel ultrasound-based, non-invasive techniques to identity tissue properties and applied strains in stretched tissues simultaneously. Ultrasound echo signals are transmitted and received by small external transducer that is transverse to the stretched tissue. From each reflected wave signal measured at several unknown strain levels, reflection coefficients (ratio of incident wave to reflected wave) and wave travel times through thickness are measured. From these parameters, the applied strain and tissue properties are evaluated simultaneously via AE. In this study, a new technique is applied to stretched porcine digital flexor tendons and the strains are successfully evaluated.
Journal of Biomechanics 2006, Vol. 39 (Suppl 1)
a combined computational and experimental methodology with a non-linear constitutive equation. Rectangular tissue samples (25 25mm 2) were excised from the axillary pouch and posterior region of the glenohumeral capsule of three fresh-frozen cadaveric shoulders and subjected to shear loading. Each tissue sample was tested parallel to the long axis of the anterior band of the inferior glenohumeral ligament (AB-IGHL). The forces and clamp displacements were input as boundary conditions to specimen-specific finite element models to simulate each experimental test. The glenohumeral capsule was represented with a hyperelastic isotropic constitutive model. Results demonstrated that there were no significant differences (p=0.45) between the average shear moduli of the axillary pouch and posterior regions when the tissue samples were loaded in shear, parallel to the long axis of the AB-IGHL. These results show greater similarities between regions of the glenohumeral capsule, as compared to prior studies. This may be attributed to the fact that this methodology analyzes both the toe region and linear region of the stress-strain curve, whereas other methodologies only analyzed the linear region. Therefore, the material properties and function of the axillary pouch and posterior capsule may be more similar than previously thought. References [1] Debski RE. JOR 1999; 17(5): 769-76.
6477 Tu, 11:30-11:45 (P18) The viscoelastic properties of human hamstring tendons X. Zhang, M. Curran, S.D. Abramowitch, S.L-'~ Woo. Musculoskeletal
Research Center, Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA Introduction: Fifty percent of anterior cruciate ligament (ACL) reconstructions use semitendinosus and gracilis tendons as autografts. Quantitative data on the viscoelastic behaviors of these tendons can aid clinicians in graft selection. The objective of this study was to investigate the difference of viscoelastic properties of semitendinosus and gracilis tendons, and variation of these properties along their length. Methods: The semitendinosus and gracilis tendons were obtained from ten fresh-frozen cadaveric knees (55.6±8.1 years) and separated into proximal and distal halves. Each half was cut into a dog-bone shape with an aspect ratio of 10 (width: 3 mm). Specimens underwent a lhr static stress relaxation test (at ~>2% strain), lhr of recovery, and a cyclic stress relaxation test (30 cycles). The QLV theory of professor Fung [1] was utilized to model the static stress relaxation data. The five constants (A,B,C,'r 1,'r2) were obtained by curvefitting the entire strain history [2], and validated by predicting the results of the cyclic stress relaxation test. The constants were then compared using a paired t-test (p < 0.025 due to a Bonferroni adjustment for multiple comparisons). Results: It was found that the viscoelastic properties of gracilis tendon was relatively uniform along its length (p >0.05). The proximal half of semitendinosus tendon, however, dissipated more energy (constant C: 0.083±0.031 vs. 0.051 ±0.017), which corresponded to a greater percentage of stress relaxation compared to its distal half. Comparison between tendons revealed that the proximal half of semitendinosus tendon had a smaller initial slope of the stressstrain curve (AxB: 163.3±88.2 MPa vs. 251.5±112.0 MPa) and dissipated more energy than that of gracilis tendon (constant C: 0.054±0.021). There were no significant differences detected for nonlinearity (B), or constants governing early and late relaxation ('r 1,'r2). Discussion: Nonhomogeneous viscoelastic properties were found along the length of the semitendinosus tendon, which may be attributed to the longer portion of the semitendinosus tendon residing in the musculotendinous junction compared to the gracilis tendon. References [1] Fung. Biomechanics 1972; 181-208. [2] Abramowitch and Woo. JBME 2004; 126: 92-97.
4381 Mo, 16:00-16:15 (P12) Carpal tunnel s y n d r o m e - The role of the subsynovial connective tissue P.C. Amadio, A.M. Ettema, K.-N. An, C. Zhao, L.E. Wold, J. Oh, S. Oh.
Orthopedics Biomechanics Laboratory, Mayo Clinic, Rochester, MN, USA Carpal tunnel syndrome (CTS) is the most common compression neuropathy, yet the cause of the compression is in most cases idiopathic. The most common clinical finding associated with the nerve compression is non-inflammatory fibrosis of the subsynovial connective tissue (SSCT) which surrounds the flexor tendons in the carpal canal. The normal SSCT has a multi-layer gliding mechanism, reminiscent of a series of sleeves around the tendon, with each successive sleeve being connected to its neighbors with fine collagenous fibers. We have conducted a series of experiments which have outlined the pathology, kinematics and material properties of the SSCT in normal individuals and in individuals with CTS, and have identified specific features within the SSCT of individuals with CTS that suggest that injury to the SSCT
Oral Presentations may play a role in the etiology of CTS. Specifically, we have identified evidence of a shearing injury of the SSCT, with fibrosis, and obliteration of the gliding, sleeve-like mechanism, being greatest close to the tendon, and with greater degrees of fibrosis being observed in more severe cases of CTS. This fibrosis is associated with tethering of the SSCT to the underlying tendon, which may increase the work of finger movement in patients with CTS, and impair differential finger movement. Based on these observations, we propose a vicious cycle of SSCT injury and repair as a working hypothesis of the etiology of CTS, and have developed a rabbit model to test this hypothesis in vivo. 5408 Tu, 12:00-12:15 (P18) Ultrasound palpation sensor for the measurement of tissue thickness and elasticity of transverse carpal ligament '~P. Zheng 1, Z.M. Li 2, A.P.C. Choi 1, M.H. Lu 1, Q.H. Huang 1. 1Department of
Health Technology and Informatics, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR, China, 2Hand Research Laboratory, Department of Orthopaedics, University of Pittsburgh, USA One of the symptoms of carpal tunnel syndrome is the stiffening of the carpal tunnel region. Traditional manual palpation has been used in the clinical practise for the assessment of the tunnel stiffness, but in a qualitative and subjective manner. Recently, some investigators have introduced various indentation methods to make objective and quantitative measurement for the tissues at the carpal tunnel region. However, both manual palpation and traditional indentation could not differentiate the stiffness of the tunnel from the soft tissues covering the tunnel. Tissue ultrasound palpation sensor (TUPS) [1] can provide a feasible solution for quantitative and objective measurement of tissue stiffness not only for a single tissue block but also for tissues with multiple layers. TUPS is comprised of an ultrasound transducer together with a load cell to form the finger-sized probe. The probe is used to push against the soft tissue surface to measure the thickness and elasticity of the soft tissues. TUPS has been successfully applied to the assessment of various human tissues. Recently, we have improved TUPS, which can now be linked to personal computer (PC) via universal serial bus (USB) and provide a better user-interface. In this paper, we introduce the recent application of TUPS for the assessment of the transverse carpal ligament and other tissues. The tissues at the carpal tunnel regions of five normal male subjects were tested using TUPS. The results showed that the average thickness of the tissues covering the carpal tunnel ligament and the tunnel region was 7.98±1.05mm and 9.59±1.12mm, respectively. Under a compression force of 20N applied by a cylindrical ultrasound indentor with a diameter of 9 mm, the stiffness of the soft tissue layer and the tunnel region was 6.72±2.10 N/mm and 15.63±8.42 N/mm, respectively. It is expected that TUPS can be a potential tool for non-invasive assessment of carpal tunnel syndrome. References [1] Zheng YP, Mak AFT. An ultrasound indentation system for biomechanical properties assessment of soft tissues in-vivo. IEEE Transactions on Biomedical Engineering 1996; 43(9): 912-918.
4530 Tu, 12:15-12:30 (P18) Non-invasive strain measurements of ligaments and tendons via acoustoelastic analysis of ultrasonic waves R. Vanderby, H. Kobayashi. Dept. of Orthopedics and Rehabilitation,
University of Wisconsin-Madison, Wisconsin, USA Many techniques have been proposed to measured in-vivo strain in ligaments and tendons [1]. Most, however, are invasive and require the surgical implantation of a measurement gauge. Others are non-invasive but they require a relatively large system that is not practical for strain measurements in the field. Acoustoelasticity (AE) is a theory that describes changes in acoustic characteristics when a medium is deformed due to its strain dependent stiffness. AE has been intensively studied in engineering materials [2]. More recently, AE has been observed in biological tissues that are nearly incompressible and can sustain large nonlinear deformations [3,4]. The studies however failed to describe the phenomenon within the framework of AE, in part because they assumed tissue incompressibility. In the present study, we use AE theory to develop a non-invasive method to measure functional tissue strain. We therefore developed rigorous AE analysis for nearly incompressible materials including biological tissues [5,6]. We also developed novel ultrasound-based, non-invasive techniques to identity tissue properties and applied strains in stretched tissues simultaneously. Ultrasound echo signals are transmitted and received by small external transducer that is transverse to the stretched tissue. From each reflected wave signal measured at several unknown strain levels, reflection coefficients (ratio of incident wave to reflected wave) and wave travel times through thickness are measured. From these parameters, the applied strain and tissue properties are evaluated simultaneously via AE. In this study, a new technique is applied to stretched porcine digital flexor tendons and the strains are successfully evaluated.