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Background: Shoulder instability is commonly observed in adolescents and young females, ranging from asymptomatic multidirectional instability (MDI) to symptomatic conditions. Patients with MDI often experience shoulder pain, muscle tension, and episodes of subluxation. This condition is associated with hypermobility spectrum disorder (HSD) and hypermobile Ehlers-Danlos syndrome (hEDS), both characterized by generalized joint laxity and recurrent joint dislocations, significantly affecting daily activities and athletic performance. Current literature lacks clarity on the actual humeral head displacement, shoulder joint kinetics, and muscle activity characteristics during movement in patients with MDI accompanied by HSD or hEDS. Additionally, the effects of electrical stimulation on different shoulder muscles and its impact on humeral head displacement in MDI patients remain to be validated.
Objective: The purposes of this study are to (1) examine whether patients with hEDS/HSD and MDI have increased humeral head translation compared to healthy controls during three isometric contraction ; (2) investigate the relationship between humeral head translation and associated muscle activity during three isometric exercises ; (3) examine the effect of NMES and NMCT to humerus/scapula muscles on humeral head translations in MDI patients with hEDS/HSD Outcome measurements: The primary outcomes include changes in acromiohumeral distance (AHD) or humeroglenoid distance (HGD) under four conditions (no stimulation, NMCT, BLH/Infraspinatus/MD stimulation, and SA stimulation) during three isometric contractions (shoulder flexion, horizontal adduction, and fully extended elbow holding weight).
The secondary outcomes assess muscle activation differences in BLH, infraspinatus, MD, UT, LT, and SA before and after NMCT.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| multidirectional instability with HSD | Experimental |
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| patients with multidirectional instability | Active Comparator |
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| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| neuromuscular eletrical stimulation | Behavioral | The GM300TE COMBO NMES (Gemore Technology Co., Ltd., New Taipei City, Taiwan), a portable machine with dual controllable channels and a manual switch, will be applied to the biceps long head, infraspinatus, middle deltoid, LT and SA. Muscle force generation is modulated by stimulated frequency, pulse width, and intensity [Bdaiwi et al., 2015]. It linearly increases with stimulated amplitude and pulse duration. The electronics of the unit creates the electrical impulses with an output frequency of 50 Hz and a pulse width of 300 microseconds. The synchronous (S) mode and asymmetrical rectangular wave-pulse will be used throughout the experiment following protocol from previous research (Bdaiwi, et al., 2015). The amplitude will be settled as muscle motor-level contraction with self-perception of maximal tolerable intensity. The time of tetanic stimulation is 7 seconds with 20-second intervals between stimulations to avoid muscle fatigue. The two circular electrodes are used on each muscl |
| Measure | Description | Time Frame |
|---|---|---|
| Western Ontario Shoulder Index (WOSI) | The Western Ontario Shoulder Instability Index (WOSI) is a patient-reported questionnaire used to evaluate shoulder-related quality of life in individuals with shoulder instability. The questionnaire includes items related to physical symptoms, sports and work function, lifestyle, and emotional well-being. Total scores range from 0 to 2100, with higher scores indicating greater impairment and poorer shoulder function. | At baseline, week 4, and week 8 after the intervention |
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Inclusion Criteria:
Patients with Multidirectional Shoulder Instability Must Meet the Following Conditions:
(A) Generalized Joint Hypermobility: Beighton score ≥ 4/9. (B) Shoulder Laxity Verified in at Least Two Directions During Clinical Examination (must meet A and B, or A and C): Inferior: Presence of a sulcus sign under the acromion or a positive Gagey hyperabduction test.
Anterior: Positive anterior load and shift test or active shoulder external rotation > 85 degrees or passive shoulder external rotation > 90 degrees.
Posterior: Positive posterior load and shift test or positive posterior jerk test.
(C) Shoulder Pain for at Least Three Months Before the Start of the Study. (D) Signs of Shoulder Instability in Daily Life Without a Traumatic Cause. (E) Ability to Raise the Arm Above 120 Degrees Without Experiencing Subluxation or Dislocation of the Shoulder.
Exclusion Criteria:
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| Name | Role | Phone | Extension | |
|---|---|---|---|---|
| Jiu Jenq Lin | Contact | 886233668126 | jiujlin@ntu.edu.tw |
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| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| School and graduate institution of physical therapy | Recruiting | Taipei | 100 | Taiwan |
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| neuromuscular control training | Behavioral | To ensure that the humeral head remains centered during the three specific isometric tasks, the examiner positioned the shoulder according to the direction of instability (anterior, inferior, or posterior) by placing the arm in 20° of shoulder flexion, 0° (neutral), or 10° of extension, respectively. In each position, the examiner gently applied a downward force on the upper arm in a horizontal direction, and the participant was instructed to gently resist the force. The goal was to guide the humeral head gradually toward the center of the glenoid, without excessive scapular movement. This training was directly supervised by a physical therapist, who provided verbal and tactile feedback to ensure correct movement execution (Figure 1). The physical therapist was also responsible for conducting the USG assessment. After a 5-minute familiarization session, participants performed the designated instability-specific isometric task for 3 repetitions. |
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