A biomechanical comparison of subscapularis repair techniques in total shoulder arthroplasty: lesser tuberosity osteotomy versus subscapularis peel.

Background: The subscapularis peel (SP) and the lesser tuberosity osteotomy (LTO) are 2 common exposure techniques for total shoulder arthroplasty. Although some biomechanical studies have suggested a higher resistance to failure with the LTO, clinical studies have demonstrated no difference in repair failure or tendon healing. We hypothesized that there would be no difference in biomechanically tested repair strength between our SP technique and the previously tested LTO technique.

Effect of Arthroscopic Stabilization on In Vivo Glenohumeral Joint Motion and Clinical Outcomes in Patients With Anterior Instability.

Background: Glenohumeral joint (GHJ) dislocations are common, and the resulting shoulder instability is often treated with arthroscopic stabilization. These procedures result in favorable clinical outcomes, but abnormal GHJ motion may persist, which may place patients at risk for developing osteoarthritis. However, the effects of shoulder instability and arthroscopic stabilization on GHJ motion are not well understood.

Associations between in-vivo glenohumeral joint motion and morphology.

Joint morphology has a significant influence on joint motion and may contribute to the development of rotator cuff pathology, but the relationships between glenohumeral joint (GHJ) morphology and in-vivo GHJ motion are not well understood. The objectives of this study were to assess measures of joint morphology and their relationship with in-vivo joint motion in two populations: shoulders with intact rotator cuffs (n=48) and shoulders with rotator cuff pathology (n=36, including 5 symptomatic tears, 9 asymptomatic tears and 22 repaired tears). GHJ morphology was measured from CT-based three-dimensional models of the humerus and scapula.

Differences in glenohumeral joint morphology between patients with anterior shoulder instability and healthy, uninjured volunteers.

Background: Traumatic glenohumeral joint (GHJ) dislocations are common, resulting in significant shoulder disability and pain. Previous research indicates that bony morphology is associated with an increased risk of injury in other joints (eg, the knee), but the extent to which bony morphology is associated with traumatic GHJ dislocation is unknown. This study assessed GHJ morphology in patients with anterior GHJ instability and in a control population of healthy volunteers.

Dynamic in-vivo assessment of navicular drop while running in barefoot, minimalist, and motion control footwear conditions.

Running-related injuries are common and previous research has suggested that the magnitude and/or rate of pronation may contribute to the development of these injuries. Accurately and directly measuring pronation can be challenging, and therefore previous research has often relied on navicular drop (under both static and dynamic conditions) as an indirect assessment of pronation. The objectives of this study were to use dynamic, biplane X-ray imaging to assess the effects of three footwear conditions (barefoot, minimalist shoes, motion control shoes) on the magnitude and rate of navicular drop during running, and to determine the association between static and dynamic measures of navicular drop.

Exercise protocol induces muscle, tendon, and bone adaptations in the rat shoulder.

Background: a rat model of supraspinatus overuse has suggested mechanisms governing tendon degeneration; however, delineating which changes are pathologic or simply physiologic adaptations to increased loading remains a question. The objective of this study was to develop and characterize a rat exercise model that induces systemic and local shoulder adaptations without mechanical injury to the supraspinatus tendon.

Methods: exercise rats completed a treadmill training protocol for 12 weeks.

Effects of footwear on three-dimensional tibiotalar and subtalar joint motion during running.

Running is a popular form of recreation, but injuries are common and may be associated with abnormal joint motion. The objective of this study was to determine the effect of three footwear conditions - barefoot (BF), an ultraflexible training shoe (FREE), and a motion control shoe (MC) - on 3D foot and ankle motion. Dynamic, biplane radiographic images were acquired from 12 runners during overground running.

Associations among shoulder strength, glenohumeral joint motion, and clinical outcome after rotator cuff repair.

Rotator cuff tears are a common condition causing pain and disability, but the relationships among clinical measures of shoulder function and measures of glenohumeral joint (GHJ) function are not well known. In the study reported here, dynamic in vivo GHJ motion was measured during abduction from biplane radiographs in 22 rotator cuff repair (RCR) patients and 36 control subjects. Isometric shoulder strength was measured and clinical outcomes were assessed using the Western Ontario Rotator Cuff (WORC) Index.

Bracing improves clinical outcomes but does not affect the medial knee joint space in osteoarthritic patients during gait.

Purpose: Osteoarthritis (OA) of the knee is commonly treated through the use of medial compartment unloading braces which have been shown to improve clinical symptoms. The objective of this study was to assess the effects of a medial compartment unloading brace on biomechanical measurements and clinical outcomes. We hypothesized that brace usage would lead to increased medial joint space and improved clinical outcomes.

Intra-articular changes precede extra-articular changes in the biceps tendon after rotator cuff tears in a rat model.

Hypothesis: Biceps tendon pathology is common with rotator cuff tears. The mechanisms for biceps changes, and therefore its optimal treatment, are unknown. Our objective was to determine the effect of rotator cuff tears on regional biceps tendon pathology.

In vivo shoulder function after surgical repair of a torn rotator cuff: glenohumeral joint mechanics, shoulder strength, clinical outcomes, and their interaction.

Background: Surgical repair of a torn rotator cuff is based on the belief that repairing the tear is necessary to restore normal glenohumeral joint (GHJ) mechanics and achieve a satisfactory clinical outcome.

Hypothesis: Dynamic joint function is not completely restored by rotator cuff repair, thus compromising shoulder function and potentially leading to long-term disability.

Study Design: Controlled laboratory study and Case series; Level of evidence, 4.

Decreased loading after rotator cuff tears leads to improved biceps tendon properties in a rat model.

Background: The purpose of this study was to elucidate the mechanism of biceps tendon changes after rotator cuff tears. We hypothesized that increased loading on the biceps tendon after rotator cuff tears will result in further detrimental changes whereas decreased loading will result in increased organization and more normal tendon composition. In addition, we hypothesized that changes with altered loading will begin at the proximal insertion into bone and progress along the tendon length at later time points.

Biceps tendon properties worsen initially but improve over time following rotator cuff tears in a rat model.

Damage to the biceps tendon is often seen in conjunction with rotator cuff tears. However, controversy exists regarding its role in the shoulder and its optimal treatment. A previous study determined that biceps tendons were detrimentally affected in the presence of rotator cuff tears in the rat model and this damage worsened over time.

The effect of altered loading following rotator cuff tears in a rat model on the regional mechanical properties of the long head of the biceps tendon.

Biceps tendon pathology is a common clinical problem often seen in conjunction with rotator cuff tears. A previous study found detrimental changes to biceps tendons in the presence of rotator cuff tears in a rat model. Therefore, the objective of this study was to utilize this model along with models of altered loading to investigate the effect of altered loading on the initiation of these detrimental changes.

Exercise following a short immobilization period is detrimental to tendon properties and joint mechanics in a rat rotator cuff injury model.

Rotator cuff tears are a common clinical problem that can result in pain and disability. Previous studies in a rat model showed enhanced tendon to bone healing with postoperative immobilization. The objective of this study was to determine the effect of postimmobilization activity level on insertion site properties and joint mechanics in a rat model.

The effect of postoperative passive motion on rotator cuff healing in a rat model.

Background: Surgical repairs of torn rotator cuff tendons frequently fail. Immobilization has been shown to improve tissue mechanical properties in an animal model of rotator cuff repair, and passive motion has been shown to improve joint mechanics in animal models of flexor tendon repair. Our objective was to determine if daily passive motion would improve joint mechanics in comparison with continuous immobilization in a rat rotator cuff repair model.

Mechanical properties of the long-head of the biceps tendon are altered in the presence of rotator cuff tears in a rat model.

Rotator cuff tears are disabling conditions that result in changes in joint loading and functional deficiencies. Clinically, damage to the long-head of the biceps tendon has been found in conjunction with rotator cuff tears, and this damage is thought to increase with increasing tear size. Despite its importance, controversy exists regarding the optimal treatment for the biceps.

After rotator cuff repair, stiffness--but not the loss in range of motion--increased transiently for immobilized shoulders in a rat model.

Although rotator cuff repair is often successful at relieving pain, the repaired insertion site frequently fails. Mechanical properties of the repair improved when the shoulder was immobilized in an animal model, but joint stiffness and range of motion were not evaluated. The objective of this study was to measure rotational mechanics before and after shoulders were immobilized after cuff injury and repair, not immobilized after cuff injury and repair, and immobilized without injury and repair.

Monitoring metabolite gradients in the blood, liver, and tumor after induced hyperglycemia in rats with R3230 flank tumors using microdialysis and bioluminescence imaging.

Hypoxia is a common cause of reduced tumor response to treatment such as irradiation. The purpose of this study was to establish a method in a rat model that is clinically applicable to monitor the efficiency of glucose transport to both tumor and normal tissue following the induction of hyperglycemia. Female Fischer 344 rats bearing subcutaneous R3230 rat mammary adenocarcinomas received glucose (1 g/kg in 200 mg/ml Normosol) injected in the femoral vein with an infusion pump at a rate of 0.

Method for improved accuracy in endogenous urea recovery marker calibrations for microdialysis in tumors.

Introduction: Urea has been proposed as an endogenous recovery marker for microdialysis for absolute concentration calculations of analytes in microdialysis samples. Previously we demonstrated a linear relationship between urea concentrations in a rat mammary carcinoma and that in plasma, validating its use as a recovery marker for that particular tumor. In this paper, we have extended the validation to two other tumor lines, thereby providing confidence that the calibration is constant across tumor types.

Spatial heterogeneity and oxygen dependence of glucose consumption in R3230Ac and fibrosarcomas of the Fischer 344 rat.

To examine the oxygen-dependence of glucose consumption in solid tumors, we monitored gradients of glucose, lactate, and hypoxia in R3230Ac and FSA tumors growing in Fischer 344 rats. Bioluminescence imaging, detection of Hoechst 33342, and immunostaining of the hypoxia marker EF5 [2-8-N-(2,2,3,3,3-pentafluoropropyl)acetamide] were done in serial tumor slices. Glucose and lactate levels were also determined in liver and blood.