Humeral head translation decreases with muscle loading
ABSTRACT This study was conducted to determine the effect of in vitro passive and active loading on humeral head translation during glenohumeral abduction. A shoulder simulator produced unconstrained active abduction of the humerus in 8 specimens. Loading of the supraspinatus, subscapularis, infraspinatus/teres minor, and anterior, middle, and posterior deltoid muscles was simulated by use of 4 different sets of loading ratios. Significantly greater translations of the humeral head occurred both in 3 dimensions (P < .001) and in the sagittal plane (P < .005) during passive motion when compared with active motion from 30 degrees to 70 degrees of abduction. In the sagittal plane, passive abduction experienced a resultant translation of 3.8 +/- 1.0 mm whereas the active loading ratios averaged 2.3 +/- 1.0 mm. There were no significant differences in the translations that were produced by the 4 sets of muscle-loading ratios used to achieve active motions. This study emphasizes the importance of the musculature in maintaining normal ball-and-socket kinematics of the shoulder.
- Plasma Process-Induced Damage, 1997., 2nd International Symposium on; 06/1997
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ABSTRACT: This study compared the effect of a computer-assisted and a traditional surgical technique on the kinematics of the glenohumeral joint during passive abduction after hemiarthroplasty of the shoulder for the treatment of fractures. We used seven pairs of fresh-frozen cadaver shoulders to create simulated four-part fractures of the proximal humerus, which were then reconstructed with hemiarthroplasty and reattachment of the tuberosities. The specimens were randomised, so that one from each pair was repaired using the computer-assisted technique, whereas a traditional hemiarthroplasty without navigation was performed in the contralateral shoulder. Kinematic data were obtained using an electromagnetic tracking device. The traditional technique resulted in posterior and inferior translation of the humeral head. No statistical differences were observed before or after computer-assisted surgery. Although it requires further improvement, the computer-assisted approach appears to allow glenohumeral kinematics to more closely replicate those of the native joint, potentially improving the function of the shoulder and extending the longevity of the prosthesis.The Bone & Joint Journal 10/2008; 90(9):1256-9. DOI:10.1302/0301-620X.90B9.20612 · 2.80 Impact Factor
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ABSTRACT: The purpose of this study was to establish if, in elite junior tennis players, there is a difference between the dominant and nondominant shoulders in the internal and external range of motion (ROM) of the shoulder and to examine the effect of taping the dominant shoulder on glenohumeral internal and external rotation ROM. Measurement of glenohumeral rotational ROM was performed on the dominant and nondominant shoulders in supine with the humerus abducted to 90 degrees. Training room at the New South Wales Institute of Sport tennis center, Homebush, New South Wales, Australia. Eleven asymptomatic male subjects and 10 asymptomatic female subjects from an elite junior training squad participated in the study. Humeral head repositioning with tape. Glenohumeral ROM. A statistically significant decrease in internal rotation for both the male and female groups between the dominant and nondominant shoulders, but only the female group had a significant increase in external rotation in the dominant compared with the nondominant shoulder. There was also a statistically significant increase in range between the tape and no tape conditions for each rotation condition. The specific application of tape to the glenohumeral joint can immediately increase rotational ROM in the dominant arm of tennis players.Clinical journal of sport medicine: official journal of the Canadian Academy of Sport Medicine 04/2009; 19(2):90-4. DOI:10.1097/JSM.0b013e31819b9cd1 · 2.01 Impact Factor