Biomedical subjects

Vincent M Wang

Publications and source records attributed to Vincent M Wang.

7 recordsLinked to original sources

PubMed2007

Novel procedure for high-fidelity tendon histology.

A novel method to obtain high-quality histologic sections of rat tendon for light microscopic study is presented. This approach utilizes non-deleterious dehydrating and clearing solvents and a hydrophobic acrylic (methyl methacrylate) resin. This methodology avoids processing and microtomy artifacts common with routine paraffin wax techniques and overcomes specimen size limitations associated with hydrophilic (e.g., glycol methacrylate) resin histologic methods. These novel histologic processing techniques facilitate the reliable assessment of tendons' cellular and matrix components and can be readily adapted to morphologic studies of damage, healing, and repair.

Acrylic Resins↗

PubMed2006

Variability in tendon and knee joint biomechanics among inbred mouse strains.

Hereditary factors are thought to be responsible for impaired tendon function and joint laxity. The present study investigated the genotypic variability of knee laxity and stiffness and tendon mechanical and geometric properties among 16-week-old female A/J, C57BL/6J (B6), and C3H/HeJ (C3H) inbred mice. In one group of mice, knee mechanics were quantified using a custom loading apparatus enabling translation of the tibia against a stationary femur. In a second group, flexor digitorum longus and Achilles tendons from the left hind limb underwent biomechanical testing, while those of the contralateral limb were analyzed histologically for determination of cross-sectional area. Our results demonstrate that tendon and joint mechanics varied significantly among the inbred mouse strains, indicating that biomechanical properties are genetically determined. A/J mouse knees exhibited greater laxity (p < 0.001) and lower stiffness (p < 0.001) compared to those of the B6 and C3H mice. The genotypic differences in whole joint properties were similar to those of the tendons' structural biomechanical traits. Although body mass did not differ (p > 0.2) among the three strains, significant genotypic differences were found at the whole tendon, material quality, and morphological levels of the tissue hierarchy. Furthermore, genetic regulation of tendon mechanical properties varied with anatomic site. Patterns of genotypic differences in tendon size were not consistent with those of biomechanical properties, suggesting that unique combinations of structural and compositional factors contribute to tendon growth, adaptation, and development. Therefore, the three inbred strains constitute a useful experimental model to elucidate genetic control of structure-function relationships in normal and healing tendons and ligaments.

Achilles Tendon↗

PubMed2005

Inhomogeneous mechanical behavior of the human supraspinatus tendon under uniaxial loading.

Disorders of the rotator cuff, particularly tears of the rotator cuff tendons, cause significant shoulder disability. Among numerous factors thought to be responsible for the initiation and progression of supraspinatus tears are those related to the tendon's biomechanical properties. We hypothesized that in supraspinatus tendons subjected to tensile loading a strain gradient (difference) exists between the articular and bursal tendon surfaces, that regional strain differences exist on each of these two tendon surfaces, and that tendon surface strains vary with glenohumeral abduction. To test these hypotheses, the intrinsic inhomogeneous deformational characteristics of the articular and bursal surfaces of eight intact human cadaveric supraspinatus tendons were studied at three glenohumeral abduction angles using a novel multiple strain measuring system which simultaneously recorded surface marker displacements on two opposing soft tissue surfaces. Under applied tensile loads, the articular surface exhibited greater strain at 22 degrees (7.4+/-2.6% vs. 1.3+/-0.7%, p=0.0002) and 63 degrees (6.4+/-1.6% vs. 2.7+/-1.2%, p=0.0001) whereas the bursal surface exhibited greater strain at 90 degrees (7.6+/-2.8% vs. 4.9+/-0.4%, p=0.013). At all abduction angles, insertion strains were higher than those of the mid-tendon and tendon-muscle junction regions. The existence of inhomogeneous surface strains in the intact supraspinatus tendon demonstrates that intratendinous shear occurs within the tendon. The higher strain on the articular side of the tendon, especially at the insertion region, suggests a propensity for tears to initiate in the articular tendinous zone.

Adult↗

PubMed2005

Comparison of glenohumeral mechanics following a capsular shift and anterior tightening.

BACKGROUND: Numerous surgical techniques have been developed to treat glenohumeral instability. Anterior tightening procedures have been associated with secondary glenohumeral osteoarthritis, unlike the anterior-inferior capsular shift procedure, which has been widely advocated as a more anatomical repair. The objective of the present study was to quantify glenohumeral joint translations, articular contact, and resultant forces in cadaveric specimens in order to compare the effects of unidirectional anterior tightening with those of the anterior-inferior capsular shift. METHODS: Six normal fresh-frozen cadaveric shoulders were tested on a custom rig with use of a coordinate-measuring machine to obtain kinematic measurements and a six-axis load transducer to measure resultant external joint forces. Shoulders were tested in the scapular plane in three configurations (normal anatomical, anterior tightening, and anterior-inferior capsular shift) and in three humeral rotations (neutral, internal, and external). Glenohumeral articular surface geometry was quantified with use of stereophotogrammetry for kinematic and contact analyses. Resultant joint forces were computed on the basis of digitized coordinates of tendon insertions and origins. RESULTS: Compared with the controls (maximum elevation, 167 degrees 8 degrees ), the anteriorly tightened specimens demonstrated loss of external rotation, significantly restricted maximum elevation (135 degrees 16 degrees , p = 0.002), posterior-inferior humeral head subluxation, and significantly greater posteriorly directed resultant forces at higher elevations (p < 0.05). In contrast, compared with the controls, the specimens that had been treated with the anterior-inferior capsular shift demonstrated a similar maximum elevation (159 degrees +/- 11 degrees , p = 0.8) without any apparent loss of external rotation and with reduced humeral translation. CONCLUSIONS: Anterior tightening adversely affects joint mechanics by decreasing joint stability, limiting both external rotation and arm elevation, and requiring greater posterior joint forces to attain maximum elevation. The anterior-inferior capsular shift improves joint stability while preserving external rotation with no significant loss of maximum elevation.

Adult↗

PubMedDate not supplied

Biomechanics of shoulder capsulorrhaphy procedures.

Nonanatomic capsulorrhaphy procedures and reconstructions used to treat shoulder instability create mechanical alterations to the glenohumeral joint that lead to eventual arthrosis. Current capsulorrhaphy procedures have evolved toward restoring normal anatomy and have stimulated relevant anatomic research. Analysis of the subscapularis insertion has demonstrated a superior tendinous insertion and an inferior muscular insertion with the inferior glenohumeral capsule consistently located beneath the muscular insertion of the subscapularis. In addition, 2 types of inferior humeral capsular attachments have been identified. The anterior capsular insertion may bifurcate into a superior internal fold adjacent to the articular cartilage and an inferior external fold on the humeral surgical neck. Alternatively, the capsule may insert over a broad area on the surgical neck. Therefore, releasing the muscular portion of the subscapularis and both capsular folds or the entire broad capsular insertion enhances proper shifting of the capsule during laterally based capsulorrhaphy procedures. Biomechanical studies allow direct study of the different parameters involved in capsulorrhaphy procedures, and several recent studies have improved our understanding. Anterior tightening procedures such as the Putti-Platt or Magnuson-Stack procedure, as well as a tight Bankart repair, result in a loss of external rotation and maximum elevation. Furthermore, this type of operative intervention creates greater posterior joint loads and abnormal posteroinferior humeral head subluxation, leading to pain and arthrosis. Anatomic capsulorrhaphy procedures produce more normal joint mechanics. Current and future studies will evaluate new arthroscopic capsulorrhaphy techniques.

Biomechanical Phenomena↗

PubMedDate not supplied

Biomechanical evaluation of a novel glenoid design in total shoulder arthroplasty.

The amount of articular curvature mismatch providing optimal performance in total shoulder arthroplasty (TSA) is unknown. The objectives of this study were to quantify glenohumeral joint mechanics before and after TSA and to compare the performance of 3 glenoid components: (1) nonconforming, (2) conforming, and (3) a novel design featuring a conforming center extending into a nonconforming periphery. Six fresh-frozen cadaveric shoulders (mean age, 43 years) were mechanically tested on a custom apparatus by use of simulated muscle forces and a coordinate-measuring machine to determine joint kinematics. B-spline models of the natural and prosthetic articular surfaces were generated, and joint contact was computed by use of a proximity criterion. During both centered ( P = .02) and eccentric ( P = .05) loading protocols, glenoid contact migrated posteriorly in conforming implants. No statistical differences in kinematics and contact were found among the nonconforming design, the new design, and the natural joint. Therefore, adding a central region of conformity does not compromise the ability of nonconforming TSA components to reduce rim loading.

Adult↗

PubMedDate not supplied

Pathomechanics of acquired shoulder instability: a basic science perspective.

Normal asymptomatic glenohumeral motion is dependent on the coordinated function of dynamic and static stabilizers. Data from both selective sectioning studies of the capsuloligamentous components and tensile testing of the inferior glenohumeral ligament have provided important insights into the in situ function of these structures. However, little is known regarding the mechanism of microdamage accumulation in acquired shoulder instability. Recent findings suggest that cyclic subfailure loading of the inferior glenohumeral ligament may induce gradual stretching of the anteroinferior capsule, compromising its capacity to restrain excessive humeral translations. Further studies elucidating the mechanism of load transmission in the capsule during physiologic arm motion, as well as data on the intrinsic healing response of the capsular ligaments, are required to more fully characterize the pathoetiology of acquired shoulder instability.

Biomechanical Phenomena↗