Glenohumeral contact pressure in a simulated active compression test using cadaveric shoulders

Area of Science:

• Orthopedic biomechanics
• Shoulder joint anatomy
• Sports injury assessment

Background:

• The active compression test is used to diagnose superior labrum anterior and posterior (SLAP) lesions.
• Speculation exists that internal shoulder impingement causes a positive test.
• This study investigates glenohumeral contact pressures during the test.

Purpose of the Study:

• To evaluate the location of peak glenohumeral contact pressures during a simulated active compression test.
• To compare these pressures in cadavers with and without SLAP lesions.
• To understand the biomechanical factors influencing the test's positivity.

Main Methods:

• Utilized a cadaveric model with six specimens.
• Employed pressure sensors for glenohumeral contact and motion analysis for humeral head translation.
• Measured pressures and translations under varying deltoid and biceps loads, with and without simulated SLAP lesions.

Main Results:

• Peak contact pressure shifted from the anterior-inferior to the anterior-superior glenoid with increasing deltoid load.
• Deltoid loading caused posterior translation of the humeral head.
• Biceps loads counteracted deltoid pull only when exceeding it; SLAP lesions did not significantly affect translation or pressure location.

Conclusions:

• Posterior capsule tautness and anterior laxity during the test allow posterior humeral head translation.
• This shift in peak contact pressure to the superior glenoid may be responsible for a positive active compression test.
• SLAP lesions did not appear to be the primary cause of altered contact pressure location in this model.