Am J Sports Med 1996 May;24(3):286-292
Department of Orthopaedic Surgery, University of Pittsburgh, Pennsylvania, USA.
We conducted this cadaveric study to define a biomechanical rationale for rotator cuff function in several deficiency states. A dynamic shoulder testing apparatus was used to examine change in middle deltoid muscle force and humeral translation associated with simulated rotator cuff tendon paralyses and various sizes of rotator cuff tears. Supraspinatus paralysis resulted in a significant increase (101%) in the middle deltoid force required to initiate abduction. This increase diminished to only 12% for full glenohumeral abduction. The glenohumeral joint maintained ball-and-socket kinematics during glenohumeral abduction in the scapular plane with an intact rotator cuff. No significant alterations in humeral translation occurred with a simulated supraspinatus paralysis, nor with 1-, 3-, and 5-cm rotator cuff tears, provided the infraspinatus tendon was functional. Global tears resulted in an inability to elevate beyond 25 degrees of glenohumeral abduction despite a threefold increase in middle deltoid force . These results validated the importance of the supraspinatus tendon during the initiation of abduction. Glenohumeral joint motion was not affected when the "transverse force couple" (subscapularis, infraspinatus, and teres minor tendons) remained intact. Significant changes in glenohumeral joint motion occurred only if paralysis or anatomic deficiency violated this force couple. Finally, this model confirmed that rotator cuff disease treatment must address function in addition to anatomy.
Clin Orthop 1994 Jul;304:84-90
Department of Orthopaedics, University of Wurzburg, Germany.
Although many clinical and experimental studies have been published on shoulder instability, little is known about the relationship between degenerative changes of the cranial part of the rotator cuff and shoulder instability. The fact that some cuff lesions cause few symptoms and do not progress, while others are not only incapacitating but also progress to massive ruptures and cuff arthropathy, is still not well understood. In this study the motion patterns of the intact joint, and changes induced by a division of the supraspinatus tendon alone or of the supra- and infraspinatus tendons, were investigated in cadaver specimens. The results demonstrate that a one tendon lesion does not influence the motion pattern, whereas a two tendon lesion induces significant changes compatible with instability of the glenohumeral joint.
Acta Orthop Scand 1984 Feb;55(1):52-56
Ninety-nine shoulders from 50 decreased with an average age of 73 years were dissected. There was a significant decrease in the thickness of the supraspinatus tendons with full thickness ruptures but not in partial ruptures. A highly significant increase in the length of the extramuscular supraspinatus tendon in shoulders with partial or full thickness supraspinatus ruptures was found. However, the total length of the supraspinatus aponeurosis was the same in shoulders with ruptures as in normal shoulders of the same age. This might indicate that the increase in length of the extramuscular portion of the tendon in ruptures is not caused by elongation of the tendon but is the result of muscular decay.
Acta Orthop Belg 1991;57(2):124-129
Orthopaedic Department, Heinrich-Heine University, Dusseldorf, Germany.
To evaluate the incidence of rotator cuff ruptures, we examined 122 autopsy specimens of the shoulder and compared our results with those reported in the literature. The incidence of partial tears in our study was 28.7%; the incidence of complete rupture was 30.3%. The frequency increased with age. We found no cuff rupture without supraspinatus tendon involvement. Very often, the cuff tear was bilateral. We do not share the opinion that the rupture of the rotator cuff is primarily an injury of men. We found a higher incidence in female than in male shoulders.
J Bone Joint Surg [Am] 1988 Sep;70(8):1224-1230
Department of Orthopaedic Surgery, Nara Medical University.
In 200 shoulders from cadavera, we studied the pathological changes on the undersurface of the acromion as associated with tears of the rotator cuff. After radiographic and histological analysis, we found that in the specimens that had a partial tear of the cuff the undersurface of the acromion was almost intact. Although a lesion in the anterior one-third of the undersurface of the acromion was always associated with a tear of the cuff, the reverse was not true. We concluded that the pathogenesis of most of the tears probably is a degenerative process.
J Bone Joint Surg Br 1995 Mar;77(2):296-298
Henry Ford Hospital, Detroit, Michigan 48202, USA.
We studied the integrity of the rotator cuff in both dominant and non-dominant shoulders of 90 asymptomatic adults between the ages of 30 and 99 years using ultrasound. The criteria for diagnosis had been validated on unembalmed cadaver specimens. We found no statistically significant difference in the incidence of impingement findings between dominant and non-dominant arms or between genders. The prevalence of partial- or full-thickness tears increased markedly after 50 years of age: these were present in over 50% of dominant shoulders in the seventh decade and in 80% of subjects over 80 years of age. Our results indicate that rotator-cuff lesions are a natural correlate of ageing, and are often present with no clinical symptoms. Treatment should be based on clinical findings and not on the results of imaging.
Clin Orthop 1993 Sep;294:103-110
Steadman Hawkins Clinic, Vail, Colorado.
The results of nonoperative management of 53 patients with full-thickness tears of the rotator cuff proven by arthroscopic examination was as follows. Patients were treated with nonsteroidal antiinflammatory medication, stretching, strengthening, and occasional steroid injections. Average age at presentation was 62.2 years. Patients were evaluated at an average of 7.6 years. Forty patients were male, and the dominant limb was involved in 40 cases. Thirty-four patients were reviewed by questionnaire and physical examination, whereas 19 patients were evaluated by telephone interview only. In 40 patients, the onset of symptoms was associated with an injury. In 12 patients, workmen's compensation was involved. At follow-up evaluation, the 34 shoulders that were available for examination were evaluated for pain, range of motion, strength, and function. Thirty-nine of the 53 patie nts (74%) assessed subjectively had only slight or no shoulder discomfort. Of the 28 shoulders presenting within three months of injury, 24 (86%) were rated as satisfactory at the time of latest evaluation. Of the 16 patients who initially had had shoulder pain for over 6 months, only nine (56%) were rated as satisfactory. Most patients showed improvement with regard to their ability to perform activities of daily living. Average active total elevation was 149 degrees compared with 121 degrees at initial presentation. Thirty-two of the 34 patients examined (94%) had evidence of weakness on muscle testing and 19 (56%) had demonstrable muscle atrophy.
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