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Quantifying shoulder rotation weakness in patients with shoulder impingement.
Timothy F Tyler1, Rachael C Nahow, Stephen J Nicholas
1Nicholas Institute of Sports Medicine and Athletic Trauma, Lenox Hill Hospital, 130 E. 77th Street, New York, NY 10021, USA.
Journal of Shoulder and Elbow Surgery
|December 13, 2005
Summary
Handheld dynamometer (HHD) testing reveals significant shoulder strength deficits in patients with impingement, even when manual muscle testing appears normal. This method is crucial for identifying subtle weakness missed by isokinetic testing.
Area of Science:
- Orthopedics
- Sports Medicine
- Rehabilitation Science
Background:
- Shoulder impingement syndrome is a common cause of shoulder pain and dysfunction.
- Manual muscle testing (MMT) is frequently used to assess shoulder strength, but may not detect subtle deficits.
- Isokinetic testing is a common objective measure of muscle strength, but its sensitivity in detecting deficits in certain shoulder positions and movements is debated.
Purpose of the Study:
- To determine if strength deficits in shoulder internal and external rotators can be detected in individuals with and without shoulder impingement using handheld dynamometry (HHD) and isokinetic testing.
- To compare the sensitivity of HHD and isokinetic testing in identifying strength deficits in various shoulder positions and velocities.
- To investigate strength differences between dominant and non-dominant arms in healthy individuals.
Main Methods:
- Seventeen patients with shoulder impingement and 22 healthy control subjects participated.
- Shoulder strength of internal and external rotators was assessed using HHD and isokinetic dynamometry at 60°/s and 180°/s.
- Testing was performed in the scapular plane and a 90° abduction/90° external rotation (90-90) position.
- Strength deficits were calculated by comparing involved/uninvolved limbs (patients) and dominant/non-dominant limbs (controls).
Main Results:
- Patients with shoulder impingement exhibited a significant 28% deficit in external rotator strength at the 90-90 position when tested with HHD (P < .01), which was not detected by isokinetic testing (0% deficit, P = .99).
- Healthy control subjects showed greater internal rotator strength in their dominant arm compared to the non-dominant arm, evident with HHD in both the 90-90 position (11% deficit, P < .01) and scapular plane (7% deficit, P < .05).
- HHD testing identified strength deficits not apparent with isokinetic testing, particularly in the 90-90 position.
Conclusions:
- Handheld dynamometry is a valuable tool for quantifying shoulder strength deficits that may be missed by standard manual muscle testing and isokinetic testing.
- Clinicians can utilize HHD to identify subtle weakness in shoulder rotators, potentially leading to earlier and more accurate diagnosis and treatment of shoulder conditions.
- The findings highlight the importance of using sensitive objective measures like HHD in the assessment of shoulder strength, especially in the context of impingement and for differentiating limb dominance effects.