A biomechanical evaluation of restraints to posterior shoulder dislocation
1
ABSTRACTS 137 visualization of this area provides an unusual per- spective of the anatomical structures, which were not heretofore realized through open surgical pro- cedures. This study was undertaken to attempt to better define the arthroscopic anatomy of the sub- acromial space. Arthroscopic evaluation of the subacromial space of 10 fresh cadaver shoulders was followed by gross anatomical dissections. By doing so, we have better defined the confines of the subacromial space, the portions of the rotator cuff able to be visualized arthroscopically, as well as those areas that are "blind" to arthroscopic evaluation. In ad- dition, the anatomy of the coracoacromial ligament, the undersurface of the acromion, and the acromio- clavicular joint as viewed arthroscopically is pre- sented with gross anatomical correlation. We be- lieve that this information will help arthroscopists better understand the advantages as well as the lim- itations of arthroscopy of the subacromial space. A Biomechanical Evaluation of Restraints to Poste- rior Shoulder Dislocation. Stephen C. Weber and Richard B. Caspari. Sacramento, California, U.S.A. Unlike the knee, relatively few studies exist that critically evaluate the structures contributing to sta- bility of the glenohumeral joint, especially posteri- orly. We attempted to evaluate the biomechanics of posterior dislocation and the structures involved in traumatic posterior instability using in vitro testing of cadaver material. Nine fresh frozen cadaver shoulders were arthroscoped and roentgenograms obtained prior to testing to confirm that no intraar- ticular pathology existed. These were then mounted in an Instron 1122 testing device in 90° forward flexion, full adduction and internal rota- tion, and the humerus displaced posteriorly at a rate of 25.4 mm/min. Force/displacement curves were generated for each shoulder. After testing each shoulder had roentgenograms and arthro- scopic and subsequent open dissection. All shoulders were rendered clinically and radiographi- cally unstable posteriorly with testing. Osseous variation such as retroversion and glenohumeral index did not affect force/displacement curves. While clinical instability was produced with dis- placement of one-half of the diameter of the hu- meral head, force/displacement curves did not show an inflection point but continued a relatively straight line, implying a continuum between sub- luxation and dislocation, as has been noted clini- cally. All shoulders had posterior capsular injury when inspected, either posterior capsule or poste- rior Bankart lesions or both. Two osseous Bankart lesions were also created. No injury to the superior glenohumeral ligament was noted. Posterior insta- bility is most likely a continuum between subluxa- tion and dislocation with progressive injury to the posterior capsule, and attachments such as the la- bruin as the principal restraint to posterior dis- placement. The Pathology of the Frozen Shoulder: An Arthro- scopic Perspective. Gregory Uitvlugt, David A. De- trisac, and Lanny L. Johnson. East Lansing, Mich- igan, U.S.A. Diagnostic arthroscopy followed by gentle shoulder manipulation provided observations con- cerning the pathology of adhesive capsulitis ("frozen shoulder"). Thirty-one frozen shoulders underwent diag- nostic arthroscopy and fluid distention, followed by manipulation in 30 patients. One patient had bi- lateral shoulder involvement, but not concurrently. Patients had an average of 10 months' conservative treatment prior to arthroscopy. There were 17 women and 13 men, with average ages of 48 and 45 years, respectively. Sixteen right shoulders and 15 left shoulders were involved. At arthroscopy, no intraarticular adhesions, ar- ticular cartilage atrophy, or degenerative changes were noted. The principal arthroscopic finding was superior recess synovitis originating from the subscapularis bursa. Vascular synovitis of the rotator cuff and biceps tendon was observed less frequently, and was less severe. In 13 patients, arthroscopic inspection followed gentle manipulation. Hemorrhage in the anterior wall along its inferior aspect and along the inferior glenohumeral ligament was noted. No rotator cuff lesions were created. There was minimal operative morbidity and no complications. The pathologic process is inflammatory, origi- nating in the subscapularis bursa, and eventually affecting the entire capsule, resulting in global shoulder immobility. Arthroscopic Subacromial Decompression. James C. Esch, Leonard R. Ozerkis, James A. Helgager, Arthroscopy, Vol. 4, No. 2, 1988
Transcript of A biomechanical evaluation of restraints to posterior shoulder dislocation
ABSTRACTS 137
visualization of this area provides an unusual per- spective of the anatomical structures, which were not heretofore realized through open surgical pro- cedures. This study was undertaken to attempt to better define the arthroscopic anatomy of the sub- acromial space.
Arthroscopic evaluat ion of the subacromial space of 10 fresh cadaver shoulders was followed by gross anatomical dissections. By doing so, we have better defined the confines of the subacromial space, the portions of the rotator cuff able to be visualized arthroscopically, as well as those areas that are "blind" to arthroscopic evaluation. In ad- dition, the anatomy of the coracoacromial ligament, the undersurface of the acromion, and the acromio- clavicular joint as viewed arthroscopically is pre- sented with gross anatomical correlation. We be- lieve that this information will help arthroscopists better understand the advantages as well as the lim- itations of arthroscopy of the subacromial space.
A Biomechanical Evaluation of Restraints to Poste- rior Shoulder Dislocation. Stephen C. Weber and Richard B. Caspari. Sacramento , California, U.S.A.
Unlike the knee, relatively few studies exist that critically evaluate the structures contributing to sta- bility of the glenohumeral joint, especially posteri- orly. We attempted to evaluate the biomechanics of posterior dislocation and the structures involved in traumatic posterior instability using in vitro testing of cadaver material. Nine fresh frozen cadaver shoulders were arthroscoped and roentgenograms obtained prior to testing to confirm that no intraar- t icular pa tho logy exis ted. These were then mounted in an Instron 1122 testing device in 90 ° forward flexion, full adduction and internal rota- tion, and the humerus displaced posteriorly at a rate of 25.4 mm/min. Force/displacement curves were generated for each shoulder. After testing each shoulder had roentgenograms and arthro- scopic and subsequen t open dissect ion. All shoulders were rendered clinically and radiographi- cally unstable posteriorly with testing. Osseous variation such as retroversion and glenohumeral index did not affect force/displacement curves. While clinical instability was produced with dis- placement of one-half of the diameter of the hu- meral head, force/displacement curves did not show an inflection point but continued a relatively straight line, implying a continuum between sub-
luxation and dislocation, as has been noted clini- cally. All shoulders had posterior capsular injury when inspected, either posterior capsule or poste- rior Bankart lesions or both. Two osseous Bankart lesions were also created. No injury to the superior glenohumeral ligament was noted. Posterior insta- bility is most likely a continuum between subluxa- tion and dislocation with progressive injury to the posterior capsule, and attachments such as the la- bruin as the principal restraint to posterior dis- placement.
The Pathology of the Frozen Shoulder: An Arthro- scopic Perspective. Gregory Uitvlugt, David A. De- trisac, and Lanny L. Johnson. East Lansing, Mich- igan, U.S.A.
Diagnost ic a r t h roscopy fo l lowed by gent le shoulder manipulation provided observations con- cerning the pa tho logy of adhes ive capsul i t i s ("frozen shoulder").
Thirty-one frozen shoulders underwent diag- nostic arthroscopy and fluid distention, followed by manipulation in 30 patients. One patient had bi- lateral shoulder involvement, but not concurrently. Patients had an average of 10 months' conservative treatment prior to arthroscopy. There were 17 women and 13 men, with average ages of 48 and 45 years, respectively. Sixteen right shoulders and 15 left shoulders were involved.
At arthroscopy, no intraarticular adhesions, ar- ticular cartilage atrophy, or degenerative changes were noted.
The principal arthroscopic finding was superior recess synovitis originating from the subscapularis bursa. Vascular synovitis of the rotator cuff and biceps tendon was observed less frequently, and was less severe.
In 13 patients, arthroscopic inspection followed gentle manipulation. Hemorrhage in the anterior wall along its inferior aspect and along the inferior glenohumeral ligament was noted. No rotator cuff lesions were created.
There was minimal operative morbidity and no complications.
The pathologic process is inflammatory, origi- nating in the subscapularis bursa, and eventually affecting the entire capsule, resulting in global shoulder immobility.
Arthroscopic Subacromial Decompression. James C. Esch, Leonard R. Ozerkis, James A. Helgager,
Arthroscopy, Vol. 4, No. 2, 1988
