Shoulder strength following acromioclavicular injury

Area of Science:

• Orthopedics
• Sports Medicine
• Biomechanics

Background:

• Acromioclavicular (AC) joint injuries, particularly dislocations, are often managed nonoperatively.
• The potential for residual shoulder weakness after AC joint injury influences treatment decisions.
• Objective strength assessment is needed to determine optimal AC joint injury management.

Purpose of the Study:

• To quantitatively assess residual shoulder weakness after different treatments for AC joint injuries.
• To compare strength deficits between operative and nonoperative management of Grade III AC separations.
• To evaluate strength outcomes in Grade II AC sprains treated nonoperatively.

Main Methods:

• Utilized the Cybex II isokinetic dynamometer for objective shoulder strength testing.
• Tested 17 patients with Grade III AC separations (9 operative, 8 nonoperative) and 8 with Grade II AC sprains (all nonoperative).
• Measured strength at slow and fast speeds across various ranges of motion, comparing injured to uninjured shoulders.

Main Results:

• Nonoperatively treated Grade III AC separations exhibited no significant strength deficits.
• Surgically treated Grade III AC separations showed significant weakness (19.8%) in vertical abduction at fast speeds.
• Nonoperatively treated Grade II AC sprains demonstrated significant weakness (24.3%) in horizontal abduction at fast speeds.

Conclusions:

• Nonoperative management of Grade III AC separations preserves shoulder strength.
• Surgical treatment for Grade III AC injuries may lead to objective strength deficits.
• Conservative treatment for Grade II AC sprains can result in significant weakness, despite subjective reports of pain and stiffness in Grade III injuries treated nonoperatively.