Biomedical subjects

Louis J Soslowsky

Publications and source records attributed to Louis J Soslowsky.

31 records · Page 2Linked to original sources

PubMed2003

Failure of the biceps superior labral complex: a cadaveric biomechanical investigation comparing the late cocking and early deceleration positions of throwing.

PURPOSE: The goal of the study was to determine which position of the throwing motion, late-cocking or early deceleration, was more likely to produce lesions of the biceps superior labral complex. TYPE OF STUDY: Cadaveric biomechanical model. METHODS: Ten paired cadaver shoulders were prepared and mounted on a custom testing apparatus in 60 degrees glenohumeral abduction with the humerus in the plane of the scapula. All specimens were loaded with 100 cycles of subfailure external rotation torque (7.9 N-m) with 22 N applied to the rotator cuff tendons and long head of the biceps tendon. One of each pair of specimens was randomly tested in a late cocking position for throwing (>125 degrees external rotation, 60 degrees glenohumeral abduction, in the plane of the scapula). The other was tested in a position of early deceleration (80 degrees external rotation, 60 degrees glenohumeral abduction, 16 degrees horizontal adduction). The biceps was loaded to failure with the shoulder fixed in these positions. The specimens were then examined by 2 experienced shoulder surgeons, blinded to the test protocol, to assess for the presence of a type II SLAP lesion. RESULTS: Failure of the biceps superior labral complex occurred at the superior glenoid in 9 of 10 specimens in the late cocking position and in 2 of 10 specimens in the early deceleration position (P =.055). Five specimens developed type II SLAP lesions, with more in the late cocking position (4 of 10) than in the early deceleration position (1 of 10; P =.12). Load to failure was significantly less for the late cocking position (289 +/- 39 N) than for the early deceleration position (346 +/- 40 N; P =.004). CONCLUSIONS: These results suggest that the late cocking position may contribute to biceps-superolabral complex injuries in the thrower's shoulder.

Adult↗

PubMed2003

Effect of altered matrix proteins on quasilinear viscoelastic properties in transgenic mouse tail tendons.

Tendons have complex mechanical behaviors that are viscoelastic, nonlinear, and anisotropic. It is widely held that these behaviors are provided for by the tissue's composition and structure. However, little data are available to quantify such structure-function relationships. This study quantified tendon mechanical behaviors, including viscoelasticity and nonlinearity, for groups of mice that were genetically engineered for altered extracellular matrix proteins. Uniaxial tensile stress-relaxation experiments were performed on tail tendon fascicles from the following groups: eight week old decorin knockout, eight week old reduced type I collagen, three week old control, and eight week old control. Data were fit using Fung's quasilinear viscoelastic model, where the model parameters represent the linear viscoelastic and nonlinear elastic response. The viscoelastic properties demonstrated a larger and faster stress relaxation for the decorin knockout and a smaller and slower stress relaxation for the three week control. The elastic parameter, A, in the eight week control group was significantly greater than in the collagen reduction and three week control groups. This study provides quantitative evidence for structure-function relationships in tendon, including the role of proteoglycan in viscoelasticity. Future studies should directly correlate composition and structure with tendon mechanics for the design and evaluation of tissue-engineered constructs or tendon repairs.

Animals↗

PubMed2003

Regenerative versus reparative healing in tendon: a study of biomechanical and histological properties in fetal sheep.

Previous studies have shown fetal tissues heal in a regenerative fashion without scar formation. The objective of this study is to compare the healing properties of adult and fetal tendons. Time-mated pregnant ewes at 80-85 days of gestation were utilized. A partial, midsubstance tenotomy was performed in the lateral extensor fetal tendons, and analogous tenotomies were created in the maternal limbs. One week after injury, the fetal and adult animals were sacrificed, and tendons were histologically and mechanically evaluated. Immunohistochemical staining for transforming growth factor beta isoform 1 (TGF-beta1) was performed. Histologically, a gap with granulation tissue and inflammatory cells was visible in the site of wounding in the adult tendons. In the fetal tendons, no abnormalities were noted in the wound, with reconstitution of collagen architecture. TGF-beta1 expression was low in fetal but upregulated in the adult wounds. No significant differences were found in the biomechanical properties between groups. We identified regenerative healing properties in injured fetal tendon, while adult tendon tissue healed reparatively with scar formation. Fetal tendons demonstrated a limited recovery of mechanical properties after injury that was no better than that of the adult tendons at seven days. A better understanding of the mechanisms of fetal healing may lead to novel therapeutic strategies in the clinical setting.

Aging↗

PubMed2002

Intratendinous strain fields of the intact supraspinatus tendon: the effect of glenohumeral joint position and tendon region.

Rotator cuff tears are a common shoulder pathology and are hypothesized to relate to excessive tissue deformation. Few data exist, however, describing deformation of the rotator cuff as an intact, functional unit. Our purpose was to determine regional variations of intratendinous rotator cuff strain over a range of clinically relevant joint positions. A novel, MRI-based technique was utilized to quantify intratendinous strains in cadaveric shoulder specimens at 15 degrees, 30 degrees, 45 degrees, and 60 degrees of glenohumeral abduction in the scapular plane. The strain data were grouped into superior, middle, and inferior locations across the region where most rotator cuff tears occur clinically. A repeated measures ANOVA assessed the effects of joint position and tendon region on intratendinous strain. Few differences in intratendinous strain existed across tendon regions, but joint position had a pronounced effect. Specifically, intratendinous strain increased with increasing joint angle, and the 60 degrees strain was significantly greater than the 15 degrees strain across all tendon regions. These data suggest that joint position plays a larger role in rotator cuff mechanics than previously believed. Future studies will utilize this technique for quantifying intratendinous strain to assess the effects of partial-thickness rotator cuff tears.

Adult↗

PubMed2002

Effect of implant design on the cyclic loading properties of mini suture anchors in carpal bones.

Mini suture anchors are commonly used in hand surgery involving attachment of soft tissue to bone. There are few data on the biomechanical behavior of these implants under physiologic conditions. Commercially available mini anchors were inserted into the carpal bones of fresh-frozen cadaver wrists. Anchors were divided into threaded and pronged types according to design. The anchors were cyclically loaded. Pronged anchors (1.3 and 2.1 mm) failed at a range of 199 to 5,155 cycles. Threaded anchors (2.5 and 2.8 mm) consistently completed 40,000 cycles without failure. Before failure pronged anchors displaced on average 5.1 mm and threaded anchors displaced on average 0.01 mm. The pronged implants failed because of either prong fatigue or fracture; the threaded anchors remained structurally intact. The larger threaded suture anchors seem to have superior biomechanical properties than smaller pronged anchors.

Aged↗

PubMed2002

Interplay of the static and dynamic restraints in glenohumeral instability.

Anterior glenohumeral instability is a common, yet complicated orthopaedic disorder. During the past few years, basic science research has improved the understanding of the glenohumeral joint stabilizing systems. The current authors review new contributions specifically detailing study of the interplay between the static and dynamic restraints. Simulation of the shoulder muscles in a recent study also has manifested the powerful contribution of the joint reaction force to concavity-compression. Continued advances, such as these, will improve the understanding, and allow better outcome, in treatment of glenohumeral instability.

Biomechanical Phenomena↗

PubMed2002

Rotator cuff tendinosis in an animal model: role of extrinsic and overuse factors.

The rat shoulder animal model has been used previously to study the role of intrinsic injury (modeled as an acute insult to the tendon), extrinsic injury (modeled as external subacromial impingement), and overuse factors on rotator cuff tendinosis. These studies demonstrated that it is possible to produce rotator cuff tendinosis with any one of these factors in isolation. The current study uses the rat shoulder model to study the roles of extrinsic compression, overuse, and overuse in combination with extrinsic compression, on the development of rotator cuff tendinosis. The results of this study demonstrate that the injury created by overuse plus extrinsic compression is greater than the injuries created by overuse or extrinsic compression alone, particularly when important biomechanical variables are considered. While ineffective in causing a change in supraspinatus tendon properties in animals with normal cage activity, extrinsic compression had a significant and dramatic effect when it was combined with overuse activity. Without an additional factor, such as overhead activity, the extrinsic compression alone may be insufficient to cause tendinosis. The results of the present study support the role of multiple factors in the etiology of some rotator cuff injuries.

Animals↗

PubMedDate not supplied

External rotation of the glenohumeral joint: ligament restraints and muscle effects in the neutral and abducted positions.

External rotation of the glenohumeral joint is important in a variety of pathologic states, yet the ligamentous restraints to external rotation have not been thoroughly investigated and the muscle effects have received even less attention. The purpose of this study was to investigate the ligamentous restraints and muscle effects limiting external rotation of the glenohumeral joint in a biomechanical cadaveric model. External rotation torque was applied to the humeri of 15 shoulders mounted in the supine position in a custom fixture while varying rotator cuff and biceps loads in 15 degrees and 60 degrees of glenohumeral abduction. A randomly chosen ligament (coracohumeral ligament [CHL], combined superior and middle glenohumeral ligaments [S+M], anterior band of the inferior glenohumeral ligament [AB], entire inferior glenohumeral ligament [IGHL], or posterior capsule [PC]) was cut, and testing was repeated (n = 3 for each ligament). Torque data were collected every 3 degrees through the entire range of external rotation. Individual muscles were loaded with 22.2 N (designated as a standard state) and were compared with loads of 0, 11.1, and 44.5 N. Alterations in muscle loads were analyzed with a residual maximum likelihood-based repeated-measures model. Ligament effects were analyzed by use of analysis of variance with Tukey correction. In the neutral position, each ligament except the PC significantly affected the torque required for external rotation, with IGHL > CHL > AB > S+M. In this position, loading the subscapularis to 44.5 N significantly increased the torque required to externally rotate the shoulder whereas unloading it significantly decreased the torque required. In the 60 degrees abducted position, each ligament except the PC significantly affected the torque required for external rotation, with IGHL > AB > S+M > CHL. In this position, loading the biceps or subscapularis to 44.5 N significantly increased the torque required to externally rotate the shoulder as rotation increased whereas unloading it significantly decreased the torque required as rotation increased. This work demonstrates that the glenohumeral joint capsule behaves as a cylinder with many regions serving as restraints to external rotation. In addition, the long head of the biceps has an important role as a dynamic restraint to external rotation in the abducted shoulder. This is a new function attributed to the biceps and reinforces the role of external rotation in the generation of biceps and superior labral pathology.

Biomechanical Phenomena↗

PubMedDate not supplied

Inflammatory and angiogenic mRNA levels are altered in a supraspinatus tendon overuse animal model.

Shoulder overuse injuries, especially those to the supraspinatus tendon of the rotator cuff, are common musculoskeletal disorders. Unfortunately, little is known about the disease etiology and pathogenesis. The objective of this study was to determine the levels of specific inflammatory and angiogenic markers in a rat supraspinatus tendon overuse injury model. We hypothesized that inflammation would not be present early in the overuse protocol. Conversely, we hypothesized that the overuse protocol would result in increased angiogenesis early. Increases in five-lipoxygenase activating protein, cyclooxygenase-2, vascular endothelial growth factor, and von Willebrand factor were evaluated by use of reverse transcription-polymerase chain reaction from 1 day through 16 weeks of treadmill running (overuse protocol). These results provide important information on the role of angiogenesis and inflammation in the disease process. Future studies will further evaluate the mechanisms of the disease process as well as potential targeted treatment modalities.

5-Lipoxygenase-Activating Proteins↗

PubMedDate not supplied

Supraspinatus tendon composition remains altered long after tendon detachment.

Most rotator cuff surgery is performed on chronic tears, but changes in the composition of chronically torn tendons remain poorly understood. In this study we surgically created supraspinatus tears in the rat and analyzed the composition of the tendon over time using immunohistochemistry. We found that collagen types I and XII were greatly increased initially after injury and then decreased with time. Collagen type III was detected and persisted in the scar for months. Decorin and biglycan were increased initially and then decreased, although decorin remained elevated from normal for months after injury. Aggrecan and collagen type II were detected in small amounts after detachment, which was associated with the expression of sulfated glycosaminoglycans. These alterations were similar to those seen in human studies. As the quality of the tendon is an important factor in repair, these findings may partially explain why chronic tears heal differently than acute tears.

Animals↗

PubMedDate not supplied

The effect of fibrin clot on healing rat supraspinatus tendon defects.

The possibility that fibrin clot, with its chemotactic and mitogenic factors, might improve the healing of a defect in the rat supraspinatus tendon was evaluated. Bilateral defects were surgically created in the rat supraspinatus tendon near the humeral insertion. One defect in each rat was filled with fibrin clot from a donor animal while the other side acted as a control. The tendons were evaluated at 3, 6, and 12 weeks. On histologic evaluation persistent defects were seen at all time points, whereas the healing tissue became less cellular with better collagen organization over time. Fibrin clot remained in the healing defects of treated shoulders at early time points. Biomechanically, there was improvement of properties over time, but they did not approach those of normal tendon by 12 weeks. There was no effect from addition of the fibrin clot except at 3 weeks, where it led to a decrease in material properties.

Animals↗

PubMedDate not supplied

Intratendinous strain fields of the supraspinatus tendon: effect of a surgically created articular-surface rotator cuff tear.

Articular-surface partial-thickness rotator cuff tears play a significant role in shoulder pathology, but the role of the articular-surface tissue is poorly understood. This investigation assessed the effect of an articular-surface partial-thickness rotator cuff tear on intratendinous strain fields. A magnetic resonance imaging-based technique quantified intratendinous strains in healthy cadaveric shoulders at 15 degrees, 30 degrees, 45 degrees, and 60 degrees of glenohumeral abduction. A second set of magnetic resonance images was acquired after an articular-surface partial-thickness tear was created arthroscopically. Measures of strain were grouped into 3 tendon regions. A 3-factor analysis of variance assessed the effects of joint position, tendon region, and tendon tear. Intratendinous strains were influenced significantly by joint position, but few differences existed between tendon regions. The articular-surface partial-thickness tear increased intratendinous strain for all joint positions except 15 degrees. The results lend insight into the mechanical behavior of the normal and pathologic rotator cuff.

Adult↗

PubMedDate not supplied

Neer Award 2001: nonrecoverable strain fields of the anteroinferior glenohumeral capsule under subluxation.

Although tears of the glenohumeral capsule have been observed in anteroinferior instability, prefailure, nonrecoverable deformation is suspected but has not been shown to exist after shoulder subluxation. The inferior glenohumeral ligament in the anteroinferior capsule (AIC) is a primary stabilizer in anteroinferior instability. The aim of this study was to examine the nonrecoverable strain field of the AIC due to shoulder subluxation. Nonrecoverable strains were calculated between a nominal strain state and a postsubluxed state. AIC marker coordinates were reconstructed from stereoradiographs, and strains were calculated from these coordinates. Nonrecoverable strain was shown to develop, varying from 3% to 7% through a range of joint subluxation. High strain tended to occur on the glenoid side of the AIC. Interestingly, strains were generally not oriented along major ligamentous bands. This is the first study to quantify planar nonrecoverable strain fields in the glenohumeral joint capsule.

Adult↗