Neer Award 1999. Overuse activity injures the supraspinatus tendon in an animal model: a histologic and biomechanical study.

Overuse activity has been implicated as an etiologic factor in injury to the rotator cuff and to the supraspinatus tendon in particular. Due in part to the lack of an appropriate animal model, expex85ental studies have not addressed this issue. With the use of a rat model, we measured the effects of an overuse running regimen on 36 Sprague-Dawley rats after 4 (n = 12), 8 (n = 12), or 16 (n = 12) weeks of exercise and compared them with a control group of rats (n = 10) who were allowed normal cage activity.

Ligamentous restraints to external rotation of the humerus in the late-cocking phase of throwing. A cadaveric biomechanical investigation.

The late-cocking phase of throwing is characterized by extreme external rotation of the abducted arm; repeated stress in this position is a potential source of glenohumeral joint laxity. To determine the ligamentous restraints for external rotation in this position, 20 cadaver shoulders (mean age, 65 +/- 16 years) were dissected, leaving the rotator cuff tendons, coracoacromial ligament, glenohumeral capsule and ligaments, and coracohumeral ligament intact. The combined superior and middle glenohumeral ligaments, anterior band of the inferior glenohumeral ligament, and the entire inferior glenohumeral ligament were marked with sutures during arthroscopy.

Effect of compressive loading on chondrocyte differentiation in agarose cultures of chick limb-bud cells.

It is well established that mechanical loading is important to homeostasis of cartilage tissue, and growing evidence suggests that it influences cartilage differentiation as well. Whereas the effect of mechanical forces on chondrocyte biosynthesis and gene expression has been vigorously investigated, the effect of the mechanical environment on chondrocyte differentiation has received little attention. The long-term objective of this research is to investigate the regulatory role of mechanical loading in cell differentiation.

A quantitative investigation of structure-function relationships in a tendon fascicle model.

These studies sought to investigate quantitative relationships between the complex composite structure and mechanical properties of tendon. The isolated mouse tail tendon fascicle was chosen as an appropriate model for these so-called "structure-function" investigations. Specifically, collagen fibril diameters and mechanical properties were measured in fascicles from immature (3 week) control, adult (8 week) control, and adult (8 week) MovI3 transgenic mice.

Animal models of tendon and ligament injuries for tissue engineering applications.

Improved methods are needed for prevention and treatment of injuries to the musculoskeletal soft tissues. Tissue engineering techniques have led to more effective clinical protocols for treating these injuries. Improvement of tissue healing through the addition of biologic factors, and the development of biologically active tissue engineered replacements, are two promising areas of research.

Rotator cuff defect healing: a biomechanical and histologic analysis in an animal model.

Rotator cuff tears are one of the most common causes of pain and disability in the upper extremity. With the use of an animal model, we studied the healing response of a controlled defect in the normal supraspinatus tendon and in a tendon with a reduced intrinsic healing capacity. In 36 Sprague-Dawley rats, defects (2 mm x 2 mm) were created in the supraspinatus tendons bilaterally.

The effects of overuse combined with intrinsic or extrinsic alterations in an animal model of rotator cuff tendinosis.

An in vivo animal model was used to evaluate overuse and overuse plus intrinsic tendon injury or extrinsic tendon compression in the development of rotator cuff injury. Forty-four male Sprague-Dawley rats were divided into groups of 22. Each left shoulder received an intrinsic or extrinsic injury plus overuse (treadmill running), and each right shoulder received only overuse.

The mechanism of creation of superior labrum, anterior, and posterior lesions in a dynamic biomechanical model of the shoulder: the role of inferior subluxation.

Lesions of the superior glenoid labrum are a source of shoulder disease. However, the mechanisms of injury to this region are unknown, and controversy exists regarding the role of shoulder instability in creation of this lesion. With a cadaver model that simulates physiologic rotator cuff forces and produces traction on the biceps tendon, the creation of type II superior labrum, anterior, and posterior (SLAP) lesions and the role of glenohumeral subluxation were investigated: Left and right shoulders from each of 8 paired cadavers (age 62 +/- 7.

Active and passive factors in inferior glenohumeral stabilization: a biomechanical model.

This study examines the stabilizing factors of the glenohumeral joint against inferior translation over a range of subluxations. Factors examined included the glenohumeral capsular ligaments, the coracohumeral ligament, the rotator cuff forces, and the long head of the biceps force. Simulated muscle forces were applied to eight shoulder specimens with the arm near 0 degrees abduction.

Posterior glenohumeral subluxation: active and passive stabilization in a biomechanical model.

Unlabelled: We examined the role of the glenohumeral and coracohumeral ligaments as well as the forces provided by the rotator cuff muscles, the long head of the biceps, the anterior and middle deltoids, and the pectoralis major in the stabilization of the glenohumeral joint in the posterior direction. Simulated muscle forces were mechanically applied to eight shoulder specimens. The humeroscapular position for testing simulated the 90-degree forward-flexion (humerothoracic) position used clinically for the so-called jerk test, which is the most clinically important position with regard to posterior instability of the shoulder.

Biomechanics of the rotator cuff.

Thorough understanding of rotator cuff mechanics is important for effective treatment and/or prevention of cuff injuries. This understanding is achieved through knowledge of normal cuff structure and mechanics. Only then, can the effects of injuries and pathologic processes on normal cuff function be carefuly assessed.

Development and use of an animal model for investigations on rotator cuff disease.

Although both intrinsic and extrinsic factors have been implicated in the cause of rotator cuff disease, previous studies have not been designed to test hypotheses of this disease, partly because of the lack of an appropriate animal model. Thirty-three animals were evaluated according to a 34 item checklist of criteria to determine their appropriateness as an animal model for investigations on the rotator cuff. Only the rat shoulder satisfactorily fulfilled all criteria, with a prominent supraspinatus tendon passing under an enclosed arch.

Coracoacromial ligament: in situ load and viscoelastic properties in rotator cuff disease.

The coracoacromial ligament plays a role in rotator cuff disease. The changes in the in situ load and viscoelastic properties of the coracoacromial ligament in shoulders with rotator cuff tears were evaluated. Coracoacromial ligaments from 16 cadaveric shoulders (8 with rotator cuff tears, 8 without tears) were evaluated via biomechanical testing of bone ligament bone specimens.

Inferior glenohumeral ligament: geometric and strain-rate dependent properties.

The inferior glenohumeral ligament (IGHL) is an important structure for maintaining shoulder stability. This study was aimed at determining the geometric and anatomic characteristics of the IGHL and its tensile properties at a higher strain rate than previously tested. Eight fresh-frozen human cadaver shoulders (average age 69 years, age range 62 to 73 years) from four female and four male cadavers were used to harvest bone-ligament-bone specimens from the three regions of the IGHL (superior band, anterior axillary pouch, and posterior axillary pouch).

Anterior glenohumeral stabilization factors: progressive effects in a biomechanical model.

The aim of this study was to evaluate the anterior stabilizing factors of the glenohumeral joint over a range of translations. The stabilizers examined included the capsular ligaments, the coracohumeral ligament, the rotator cuff muscles, and the long head of the biceps. Simulated muscle forces were applied to eight shoulder specimens to produce 90 degrees of total elevation of the arm in the scapular plane.

Contact areas in the thumb carpometacarpal joint.

The thumb carpometacarpal joint is a common site of osteoarthritis. It has been hypothesized that peaks of localized stress on the dorsoradial or volar-ulnar regions, or both, of the articular surfaces of the trapezium and metacarpal lead to erosion of cartilage and may be responsible for the progression of the disease. The objective of this study was to determine the contact areas in this joint under the functional position of lateral (key) pinch and in the extremes of range of motion of the joint.

Excursion of the rotator cuff under the acromion. Patterns of subacromial contact.

Nine fresh-frozen, human cadaveric shoulders were elevated in the scapular plane in two different humeral rotations by applying forces along action lines of rotator cuff and deltoid muscles. Stereophotogrammetry determined possible regions of subacromial contact using a proximity criterion; radiographs measured acromiohumeral interval and position of greater tuberosity. Contact starts at the anterolateral edge of the acromion at 0 degrees of elevation; it shifts medially with arm elevation.

A new optical system for the determination of deformations and strains: calibration characteristics and experimental results.

Many types of optical strain measurement systems have been used for the determination of deformations and strains in soft biological tissues. The purpose of this investigation is to report a new optical strain measurement system developed in our laboratory which offers distinct advantages over systems developed in the past. Our optical strain system has demonstrated excellent performance in calibration and experimental tests.

Computer simulation of glenohumeral and patellofemoral subluxation. Estimating pathological articular contact.

Analytic stereophotogrammetry and an interactive computer graphics program were used to obtain first order assessments of joint contact patterns in patellofemoral and glenohumeral joints, simulating normal and abnormal articulations. Precise (90 microns accuracy) computer graphic representations of the humeral head, glenoid, patella, and femoral articular surfaces were obtained from cadaver knees and shoulders. These surface representations were then manipulated into an articulated position, and joint contact areas computed by a proximity criterion.

Geometric and mechanical properties of the coracoacromial ligament and their relationship to rotator cuff disease.

One of the most common causes of pain and disability in the upper limb is inflammation of the rotator cuff tendons. When no significant bony abnormality exists in the surrounding structures, the coracoacromial ligament has been implicated as a possible cause of impingement on the cuff tendons. Geometric and mechanical properties of 20 coracoacromial ligaments, 10 from shoulders with rotator cuff tears and 10 from normal shoulders, were accurately determined.

A stereophotogrammetric method for determining in situ contact areas in diarthrodial joints, and a comparison with other methods.

Determination of contact areas in diarthrodial joints is necessary for understanding the state of stress within the articular cartilage layers and the supporting bony structures. The present study describes the use of a stereophotogrammetry (SPG) system [Huiskes et al., J.

Articular geometry of the glenohumeral joint.

Little quantitative data exists defining the true shape of the humeral head and glenoid articular surfaces. This study uses a precise stereophotogrammetry (SPG) technique and provides highly accurate quantitative results for determining the three-dimensional geometry of glenohumeral joint articular surfaces, including their "sphericity", surface areas, cartilage thickness, and the difference in these quantities between the genders. Results indicate that glenohumeral joint surfaces may be approximated by a section of a sphere with small deviations from sphericity of less than 1% of the radius.

Quantitation of in situ contact areas at the glenohumeral joint: a biomechanical study.

Glenohumeral arthritis may result from abnormal articular mechanics, and shoulder reconstructive procedures often rely implicitly on the belief that the restoration of normal articular mechanics is required to obtain satisfactory clinical results. Despite this, limited knowledge of normal or pathologic glenohumeral joint articular mechanics and contact is available. This study uses a stereophotogrammetry technique to determine contact areas in normal cadaver glenohumeral joints with intact ligaments and capsule through a large range of motion using simulated forces of the four rotator cuff muscles and three deltoid heads.

Tensile properties of the inferior glenohumeral ligament.

The tensile properties of the inferior glenohumeral ligament have been determined in 16 freshly frozen cadaver shoulders. The inferior glenohumeral ligament was divided into three anatomical regions: a superior band, an anterior axillary pouch, and a posterior axillary pouch. This yielded 48 bone-ligament-bone specimens, which were tested to failure in uniaxial tension.

The relationship of acromial architecture to rotator cuff disease.

Variations in the architecture of the coracoacromial arch can lead to a clinically symptomatic rotator cuff lesion. Differences in the development and morphology of the acromion, and the presence of anterior acromial spurs and inferior acromioclavicular osteophytes decrease the volume of the subacromial space, leading to impingement. Recent anatomic, radiographic, biomechanical, and SPG studies have confirmed these architectural variations and their effects on the contents of the subacromial space.