HYPOTHESIS: Elevation of the arm during a dynamic scaption exercise will result in a progressive narrowing of the acromiohumeral interval (AHI); however, the addition of a load will not significantly affect the AHI in healthy baseball players. MATERIALS AND METHODS: Thirteen healthy baseball players performed a seated scaption exercise from 0 degrees to 90 degrees , with and without a normalized additional load. Dynamic AHI intervals were measured using digital fluoroscopic videos with the arm at the side, and at 30 degrees , 45 degrees , 60 degrees , and 75 degrees of humeral elevation. RESULTS: The mean AHI for unloaded and loaded scaption decreased significantly (P < .001) from the arm at the side (12.7 mm) until 45 degrees (4.9 mm), further changes in the mean AHI between 45 degrees , 60 degrees , and 75 degrees were not significantly different. Generally, loaded scaption resulted in smaller AHI values at 45 degrees , 60 degrees , and 75 degrees ; however, only the differences at 60 degrees (P = .005) and 75 degrees (P = .003) were significant. DISCUSSION: Narrowing of the AHI during dynamic motion was similar to previous reports of static AHI, with the exception of the trend towards widening of the AHI seen at 75 degrees during both conditions. The additional AHI narrowing observed at 60 degrees and 75 degrees during the loaded exercise may indicate that scapular positioning is more influential in this range. CONCLUSION: An additional AHI narrowing of 11% during loaded scaption, did not result in any clinical impingement during the exercise, but may have more serious implications in other healthy and pathologic populations.
展开▼
