Glenohumeral Biomechanics of Physical Therapy Mobilization Techniques

Physical therapists employ mobilization techniques for restoring range of motion. The objective was to develop a protocol for quantifying and comparing glenohumeral (GH) joint mobilization techniques performed by physical therapists in a human cadaveric model. Two different GH joint positions were investigated using grade IV non-oscillatory mobilizations. One right human cadaveric shoulder (Age:52, MALE) was procured. The scapula was mounted in an upright neutral position to a 6 axis load cell with the humerus freely suspended. GH motion was recorded in three dimensions. Rotator cuff muscle tone (subscapularis, supraspinatus, and teres minor/infraspinatus) was simulated using static 5 N loads. Two experienced physical therapists performed three sets of posterior (P), anterior (A) and inferior (I) glides from neutral and resting positions. Force and displacement measurements were collected at 20Hz and 10Hz, respectively, and used to determine GH three-dimensional stiffness. The mean three-dimensional stiffness values (N/mm) in neutral and resting positions were: Therapist One: A:1.87/2.28, P:1.43/3.62, I:0.83/1.08 and Therapist Two: A:1.87/1.81, P:1.24/6.66, I:0.98/0.71). Most notable differences between joint position and therapists occurred during posterior glide mobilization. In addition to studying other GH mobilization techniques the protocol can be used to determine structural tissue properties and/or measure effects of shoulder injuries on GH biomechanics.