Supraspinatus Tendons Have Different Mechanical Properties Across Sex.

Sex differences in the mechanical properties of different musculoskeletal tissues and their impact on tendon function and disease are becoming increasingly recognized. Tendon mechanical properties are influenced by the presence or absence of sex hormones and these effects appear to be tendon- or ligament-specific. The objective of this study was to determine how sex and hormone differences in rats affect supraspinatus tendon and muscle properties. We hypothesized that male supraspinatus tendons would have increased cross-sectional area but no differences in tendon material properties or muscle composition when compared to supraspinatus tendons from female or ovariectomized (OVX) female rats. Uninjured supraspinatus tendons and muscles from male, female, and OVX female rats were collected and mechanical and histological properties were determined. Our analysis demonstrated decreased dynamic modulus and increased hysteresis and cross-sectional area in male tendons. We found that male tendons exhibited decreased dynamic modulus (during low strain frequency sweep and high strain fatigue loading), increased hysteresis, and increased cross-sectional area compared to female and OVX female tendons. Despite robust mechanical differences, tendon cell density and shape, and muscle composition remained unchanged between groups. Interestingly, these differences were unique compared to previously reported sex differences in rat Achilles tendons, which further supports the concept that the effect of sex on tendon varies anatomically. These differences may partially provide a mechanistic explanation for the increased rate of acute supraspinatus tendon ruptures seen in young males.

Aging leads to inferior Achilles tendon mechanics and altered ankle function in rodents.

Spontaneous rupture of the Achilles tendon is increasingly common in the middle aged population. However, the cause for the particularly high incidence of injury in this age group is not well understood. Therefore, the objective of this study was to identify age-specific differences in the Achilles tendon-muscle complex using an animal model. Functional measures were performed in vivo and tissues were harvested following euthanasia for mechanical, structural, and histological analysis from young, middle aged, and old rats. Numerous alterations in tendon properties were detected across age groups, including inferior material properties (maximum stress, modulus) with increasing age. Differences in function were also observed, as older animals exhibited increased ankle joint passive stiffness and decreased propulsion force during locomotion. Macroscale differences in tendon organization were not observed, although cell density and nuclear shape did vary between age groups. Muscle fiber size and type distribution were not notably affected by age, indicating that other factors may be more responsible for age-specific Achilles tendon rupture rates. This study improves our understanding of the role of aging in Achilles tendon biomechanics and ankle function, and helps provide a potential explanation for the disparate incidence of Achilles tendon ruptures in varying age groups.

Ground reaction forces are more sensitive gait measures than temporal parameters in rodents following rotator cuff injury.

Gait analysis is a quantitative, non-invasive technique that can be used to investigate functional changes in animal models of musculoskeletal disease. Changes in ground reaction forces following injury have been observed that coincide with differences in tissue mechanical and histological properties during healing. However, measurement of these kinetic gait parameters can be laborious compared to the simpler and less time-consuming analysis of temporal gait parameters alone. We compared the sensitivity of temporal and kinetic gait parameters in detecting functional changes following rotator cuff injury in rats. Although these parameters were strongly correlated, temporal measures were unable to detect greater than 50% of the functional gait differences between injured and uninjured animals identified simultaneously by ground reaction forces. Regression analysis was used to predict ground reaction forces from temporal parameters. This model improved the ability of temporal parameters to identify known functional changes, but only when these differences were large in magnitude (i.e., between injured vs. uninjured animals, but not between different post-operative treatments). The results of this study suggest that ground reaction forces are more sensitive measures of limb/joint function than temporal parameters following rotator cuff injury in rats. Therefore, although gait analysis systems without force plates are typically efficient and easy to use, they may be most appropriate for use when major functional changes are expected.

Males have Inferior Achilles Tendon Material Properties Compared to Females in a Rodent Model.

The Achilles tendon is the most commonly ruptured tendon in the human body. Numerous studies have reported incidence of these injuries to be upwards of five times as common in men than women. Therefore, the objective of this study was to investigate the sex- and hormone-specific differences between Achilles tendon and muscle between female, ovariectomized female (ovarian hormone deficient), and male rats. Uninjured tissues were collected from all groups for mechanical, structural, and histological analysis. Our results showed that while cross-sectional area and failure load were increased in male tendons, female tendons exhibited superior tendon material properties and decreased muscle fiber size. Specifically, linear and dynamic moduli were increased while viscoelastic properties (e.g., hysteresis, percent relaxation) were decreased in female tendons, suggesting greater resistance to deformation under load and more efficient energy transfer, respectively. No differences were identified in tendon organization, cell shape, cellularity, or proteoglycan content. Additionally, no differences in muscle fiber type distribution were observed between groups. In conclusion, inferior tendon mechanical properties and increased muscle fiber size may explain the increased susceptibility for Achilles tendon injury observed clinically in men compared to women.

Effectiveness of coronary stent deployment without predilation.

The feasibility of coronary stenting without predilation is demonstrated in 240 patients. In all, 249 stents were placed. Primary implantation was successful in 93% of cases. In 17 lesions the stents could not be advanced through the stenotic lesion. The unexpanded stents were removed through the guiding catheter, and stenting was performed after prediction. Minor complications (side branch compromise and intimal dissection), which were successfully treated, occurred in 26 patients (10.6%).

Coronary stent deployment without predilation: prevention of complications of venous graft angioplasty.

Saphenous vein graft stenting without predilation may potentially decrease procedural complications such as distal embolization and no-reflow phenomenon. In this report the authors describe the deployment of stents (three Wallstents, one Palmaz-Schatz, one Multilink, and one NIR) without predilation in five patients with unstable angina pectoris due to high-grade stenosis in old saphenous vein grafts. Stent deployment was successful in all patients without procedure-related complications. Stenting without predilation appears to be feasible in old bypass grafts with significant stenosis. The potential of this new stenting technique to reduce the risk of stenting complications should be tested by a randomized trial.

One-year clinical and echocardiographic follow-up of patients with congestive cardiomyopathy treated with captopril compared to placebo.

The beneficial hemodynamic and clinical effects of angiotensin-converting enzyme (ACE) inhibition in patients with severe congestive heart failure has recently been documented in large-scale studies. This mode of therapy when added to digitalis and diuretics improves survival. To evaluate the clinical effect and the changes in cardiac dimensions of captopril compared to placebo we followed 50 patients with severe congestive heart failure over 1 year using echo-Doppler cardiography. After randomization, 25 patients were started on captopril and 25 patients on placebo. At baseline and at 6 and 12 months, each patient underwent exercise tolerance test, radionuclide angiography to estimate left and right ventricular ejection fraction, M mode and two-dimensional echocardiography and Doppler cardiography to calculate cardiac dimensions and stroke volumes. During follow-up two patients in the captopril group and four in the placebo group died. Due to clinical deterioration nine patients in the placebo group had to be started on open-label captopril. Treatment with captopril was associated with a more significant improvement in functional class and exercise duration compared to placebo. Forward stroke volume estimated from Doppler echocardiography increased significantly by captopril from 47 +/- 3 to 55 +/- 3 ml and decreased in the placebo-treated patients from 49 +/- 5 to 44 +/- 4 ml. This improvement was associated with a trend towards reduced heart rate by captopril. Left ventricular end diastolic volume tended to increase in the placebo group and did not change in the captopril group. Calculated mitral regurgitant volume at 6 and 12 months tended to be lower in the captopril-treated patients. Thus captopril therapy proved efficacious in patients with severe congestive heart failure and resulted in increased forward stroke volume; it may have a beneficial effect on cardiac dimensions and on mitral regurgitation.

Left ventricular filling dynamics by Doppler echocardiography in dilated cardiomyopathy: one-year follow-up in patients treated with captopril compared to placebo.

The role of impaired diastolic function in determining the pathophysiology of congestive cardiomyopathy was only recently appreciated. In the present study, echocardiography and Doppler cardiography were used to determine changes in cardiac size and transmitral filling dynamics over a 1-year period in patients with congestive cardiomyopathy and determine the effect of captopril on these changes. The study population consisted of 27 patients with congestive heart failure in spite of therapy with digitalis and diuretics (NYHA class 3.2). Fifteen patients were started on placebo and 12 on captopril. Noninvasive evaluation was performed at 6-month intervals. Left ventricular size and left ventricular ejection fraction did not change significantly in either group. Forward stroke volume improved significantly only in patients on captopril compared to placebo (p < 0.05). No significant changes in transmitral flow dynamics were observed in the placebo group whereas the captopril-treated group showed a decrease in the peak velocity, flow velocity integral and rate of rapid filling wave (E) and an increase in the peak, integral and rate of filling during atrial contraction (A). The E/A ratio did not change significantly over time in the placebo group, whereas a reduction in the ratio was noted in the captopril-treated patients. These changes are sustained over 1 year with concomitant improvement in stroke volume, exercise duration and functional class.

Initial and long-term results with the CrossFlex stent--data from a national registry.

The Cordis CrossFlex trade mark stent is a balloon expandable helical coil made of stainless steel. OBJECTIVE: To assess the short- and long-term safety and efficacy of this stent by conducting a multi-center national registry. METHODS: One hundred and sixteen stents were implanted in 109 patients (mean age 59 3 10 years, 95 males). The lesions were classified as type B2 or C in 56 patients (51%). Successful deployment was achieved in 103 patients (94.5%). Failure was due to damage to the stent (two patients) or inability to reach the lesion (four patients). High-pressure deployment (>14 atm) was used in 68% of cases. RESULTS: Edge dissections occurred in nine patients after high-pressure deployment and necessitated implantation of a second stent. One patient with a large acute myocardial infarction died during hospitalization. Side branch occlusion occurred in five patients (4.6%). Subacute thrombosis occurred in two patients (1.8%) during the first four weeks. During a six-month follow-up period, 18 patients (16.5%) were rehospitalized with recurrent angina. Fifteen patients had coronary angiography and 13 (12.1%) needed additional target lesion revascularization (TLR). Twelve patients required a second PTCA for in-stent restenosis, and one needed a coronary artery bypass graft operation. CONCLUSIONS: The CrossFlex coronary stent can successfully be used in complex coronary lesions, with few short-term complications and a low TLR rate. Operators should be aware of the possibility of edge dissection during high-pressure implantation.