Rotator Cuff Fatigue and Glenohumeral Kinematics in Participants Without Shoulder Dysfunction

Abstract

Context: Researchers have established that superior migration of the humeral head increases after fatigue of the rotator cuff muscles. In these studies, the investigators used imaging techniques to assess migration of the humeral head during statically held shoulder positions. Their results may not represent the amount of superior humeral head migration that occurs during dynamic arm elevation.Objective: To investigate the effect of rotator cuff fatigue on humeral head migration during dynamic concentric arm elevation (arm at the side [approximately 06] to 1356) in healthy individuals and to determine the test-retest reliability of digital fluoroscopic video for assessing glenohumeral migration.Design: Test-retest cohort study. Setting: Research laboratory.Patients or Other Participants: Twenty men (age 5 27.7 6 3.6 years, mass 5 81.5 6 11.8 kg) without shoulder disorders participated in this study.Intervention(s): Three digital fluoroscopic videos (2 prefatigue and 1 postfatigue) of arm elevation were collected at 30 Hz. The 2 prefatigue arm elevation trials were used to assess test-retest reliability with the arm at the side and at 456, 906, and 1356 of elevation. The prefatigue and postfatigue digital fluoroscopic videos were used to assess the effects of rotator cuff fatigue on glenohumeral migration. All measurements were taken in the right shoulder.Main Outcome Measure(s): The dependent measure was glenohumeral migration (in millimeters). We calculated the intraclass correlation coefficient and standard error of the measurement to assess the test-retest reliability. A 2 3 4 repeated-measures analysis of variance was used to assess the effects of fatigue on arm elevation at the 4 shoulder positions.Results: The test-retest reliability ranged from good to excellent (.77 to .92). Superior migration of the humeral head increased postfatigue (P , .001), regardless of angle.Conclusions: Digital fluoroscopic video assessment of shoulder kinematics provides a reliable tool for studying kinematics during arm elevation. Furthermore, superior migration of the humeral head during arm elevation increases with rotator cuff fatigue in individuals without shoulder dysfunction.Key Words: biomechanics, humeral head migration, imaging Key PointsN Superior migration of the humeral head increased during dynamic arm elevation after the supraspinatus, infraspinatus, and teres minor muscles of the rotator cuff were fatigued.N When used to analyze humeral head migration relative to the glenoid fossa, digital fluoroscopic video had good to excellent intrarater reliability.N Research is required to determine the influence of rotator cuff fatigue on glenohumeral migration in individuals with underlying shoulder disorders.

Dynamic In Vivo Glenohumeral Kinematics During Scapular Plane Abduction in Healthy Shoulders

“…One study demonstrated monotonic superior translation of the humeral head, 33 2 other studies observed the humerus moving first superiorly and then inferiorly during arm elevation, 10,20 and 3 others observed the humerus being essentially fixed with respect to the glenoid during arm elevation. 5,7,12 The absence of glenohumeral translation is surprising and counterintuitive, as one would expect the deltoid to produce superior humeral translation in the early abduction arc-the so-called "setting phase"-before the rotator cuff muscles stabilize the joint.…”

Osteokinematic analysis during shoulder abduction using the C-arm

“…In the group after the exercise, the superior translation of the humeral head was discovered (2.8 mm) in shoulder abduction from 0° to 90°, and inferior translation was discovered (0.3 mm) from 90° to 135° [26]. A later study also found that the superior translation of the humeral head was discovered (average, 0.79 mm) in shoulder abduction after the fatigue of the supraspinatus, infraspinatus, and teres minor muscles [35].…”

“…Another study found that the superior translation of the humeral head increases regardless of the angle [35]. Both studies investigated healthy participants without any shoulder disease.…”

“…Of the researchers, Poppen and Walker [5] defined the axis of the humerus and scapula using standard radiographs and analyzed the motion, accordingly. In most previous studies, images were shot in static positions, and dynamic glenohumeral arthrokinematics was not described [35]. In addition, because the two-dimensional (2D) radiographic approach was used in both of these studies, descriptions of humeral head translations were limited to static measures in the superior-inferior direction and were subject to possible projection errors [36].…”

The efficacy of functional supports in mediating the effects of exercise on shoulder joint position sense

“…In overhead sports such as tennis, badminton, vol- from a joint position sense (JPS) perspective [1]. As 7 such it may be considered as an aetiological risk fac-8 susceptible to a reduction in performance or indeed an 10 increased occurrence of injury.…”