Search

Growth factors are known to appear during wound healing. We hypothesized that growth factors would also appear during the healing process of a rotator cuff tear. We determined the expression of various growth factors during healing of acute rotator cuff tears in the rabbit. We made a full-thickness defect in the supraspinatus tendon of 27 Japanese white rabbits. The shoulders were harvested on days 1, 3, 5, 7, 9, 11, 14, 21, and 28 postoperatively (n = 3 at each time point). We assessed the expression of basic fibroblast growth factor, insulin-like growth factor 1, platelet-derived growth factor, and transforming growth factor beta. Basic fibroblast growth factor appeared with its peak on days 7 and 9, insulin-like growth factor 1 appeared with its peak on day 5, platelet-derived growth factor appeared with a mild expression between days 7 and 14, and transforming growth factor beta appeared with constant mild expression throughout the observation period. It is likely that each of these growth factors plays a role in the early phase of healing of the supraspinatus tendon in rabbits.

To clarify the relationship between the vertebral level reached by the thumb and the internal rotation angle of the humerus, 7 shoulders in healthy volunteers were examined by use of an electromagnetic tracking device. Measurements were repeated in the hanging-arm position with the thumb pointing anteriorly and at the buttock, sacrum, and each vertebral level up to T6. From the hanging-arm position to the buttock, 54.3% of internal rotation occurred (mean, 39.8 degrees ), and from the buttock to the sacrum, 11.7% occurred (mean, 8.6 degrees ). In total, 66% of internal rotation occurred from the hanging-arm position to the sacrum. Above the sacrum, the contribution of elbow flexion to the level of the vertebral spine became much greater, and internal rotation of the shoulder did not change significantly above the T12 level. We recommend that the level of the thumb below the buttock be subdivided for more accurate assessment of internal rotation.

The purpose of this study was to investigate the histopathology, including apoptosis, in the supraspinatus tendon with stage II subacromial impingement. Samples from the critical zone of the supraspinatus tendon were obtained from 5 patients with subacromial impingement syndrome and 10 autopsy cases without shoulder diseases as controls. Three-micrometer-thick sections were cut and stained with hematoxylin-eosin (H-E) for routine histologic examination. Apoptosis was detected by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL) method and single-stranded deoxyribonucleic acid (ssDNA) assay in which the frequency of the apoptotic cells was expressed by the apoptotic index. Control supraspinatus tendons showed normal morphology, whereas supraspinatus tendons from shoulders with impingement showed significant mucoid degeneration. Correspondingly, few apoptotic cells were observed in control tendons, whereas a large number of apoptotic cells were observed in the degenerative area of tendons from impingement shoulders. The apoptotic indices were significantly higher in the impingement shoulders (ssDNA, 18.84% +/- 1.75%; TUNEL, 24.92% +/- 2.79%) than in the control shoulders (ssDNA, 5.22% +/- 1.30%; TUNEL, 7.01% +/- 1.05%) (P = .04 for ssDNA and P = .017 for TUNEL). Mechanical impingement seems to cause tendon degeneration and apoptosis of the tendon cells in the supraspinatus tendon in stage II impingement.

It is known that thinning and lengthening of the subscapularis tendon occur in shoulders with recurrent anterior dislocation. However, no studies have been performed to quantify the morphologic changes of the subscapularis tendon under such conditions. We retrospectively measured the thickness and cross-sectional area of the subscapularis tendon by use of magnetic resonance imaging in 22 shoulders in 11 patients with unilateral recurrent anterior dislocation of the shoulder. The contralateral shoulder in each patient served as a control. The thickness and cross-sectional area of the subscapularis on the affected side were smaller than those on the normal side (6.5 +/- 1.7 mm vs 8.0 +/- 1.9 mm, P = .001, and 388.6 +/- 120.0 mm 2 vs 547.9 +/- 128.5 mm 2 , P = .0001, respectively). We conclude that the subscapularis tendon undergoes an 18.7% decrease in thickness and a 29.1% decrease in cross-sectional area in shoulders with recurrent anterior dislocation.

We performed 2-dimensional finite element model analysis to estimate the mechanical environment of the supraspinatus tendon. The geometric shape of the finite element model was determined by magnetic resonance imaging of a normal human shoulder obtained at 0 degrees, 30 degrees, and 60 degrees of abduction, whereas the histologic location of noncalcified and calcified fibrocartilage was determined from a cadaveric specimen. The supraspinatus tendon was pulled proximally with the force of 10 N at 0 degrees, 53 N at 30 degrees, and 115 N at 60 degrees of abduction. The area of high principal stress maximum was observed on the articular side of the supraspinatus tendon, which shifted toward the insertion as the arm was abducted. High stress concentration on the articular side of the supraspinatus tendon near its insertion during arm elevation may explain the frequent occurrence of rotator cuff tears at this site.

This preliminary prospective study was conducted to determine whether immobilization with the arm in external rotation would decrease the rate of recurrence after initial traumatic anterior dislocation of the shoulder. Forty patients with initial shoulder dislocations were assigned to (1) conventional immobilization in internal rotation (IR group, n = 20) or (2) a new method of immobilization in external rotation (ER group, n = 20). The recurrence rate was 30% in the IR group and 0% in the ER group at a mean 15.5 months. The difference in recurrence rate was even greater among those who were aged less than 30 years (45% in the IR group and 0% in the ER group). Immobilization with the arm in external rotation is effective in reducing the rate of recurrence after initial dislocation of the shoulder.