Neuromuscular Electrical Stimulation–Enhanced Physical Therapist Intervention for Functional Posterior Shoulder Instability (Type B1): A Multicenter Randomized Controlled Trial

Abstract Objective Functional posterior shoulder instability (FPSI) (type B1) is a severe type of instability, mainly in teenagers and young adults, that leads to loss of function, pain, and stigmatization among peers. An experimental nonsurgical treatment protocol based on neuromuscular electrical stimulation (NMES) showed very promising early results in the treatment of FPSI. The hypothesis of this study was that NMES-enhanced physical therapy leads to better outcomes than physical therapy alone as the current gold standard of treatment in patients with FPSI. Methods In this multicenter randomized controlled trial, patients with FPSI were randomly allocated in a 1:1 ratio to either 6 weeks of physical therapy or 6 weeks of physical therapy with simultaneous motion-triggered NMES. Baseline scores as well as outcome scores at 6 weeks, 3 months, 6 months, and 12 months after the intervention were obtained. The predefined primary outcome of this trial was the Western Ontario Shoulder Instability Index (WOSI) at the 3-month time point. Results Forty-nine patients were randomized and eligible for the trial. The group that received physical therapy with simultaneous motion-triggered NMES showed a significantly better main outcome measurement in terms of the 3-month WOSI score (64% [SD = 16%] vs 51% [SD = 24%]). Two-thirds of the patients from the physical therapist group crossed over to the group that received physical therapy with simultaneous motion-triggered NMES due to dissatisfaction after the 3-month follow-up and showed a significant increase in their WOSI score from 49% [SD = 8%] to 67% [SD = 24%]. The frequency of instability episodes showed a significant improvement in the group that received physical therapy with simultaneous motion-triggered NMES at the 3-month follow-up and beyond, while in the physical therapist group, no significant difference was observed. Conclusion The current study shows that NMES-enhanced physical therapy led to statistically significant and clinically relevant improvement in outcomes in the treatment of FPSI compared to conventional physical therapy alone—from which even patients with prior unsatisfactory results after conventional physical therapy can benefit. Impact Based on the results of this study, NMES-enhanced physical therapy is an effective new treatment option for FPSI, a severe type of shoulder instability. NMES-enhanced physical therapy should be preferred over conventional physical therapy for the treatment of patients with FPSI.

-Prior to the physiotherapeutic treatment, the required intensity of the electric current is specified.It is important to use the highest current intensity the patient can comfortably handle (it typically increases over the course of the treatment).
-The electrode is positioned in the area of the nerve supplying the hypoactive muscle.
Simultaneous stimulation of agonist and antagonist is to be avoided because of the resulting movement restriction.One electrode is placed inferior to the spina scapulae to stimulate the external rotators (M.infraspinatus, M. teres minor).The second electrode is placed medially to the margo medialis scapulae to stimulate the scapula retractors (M.trapezius, M. rhomboidei).
-Aim for an initial abduction-external rotation of the arm due to the electrical stimulation of external rotators and scapula retractors.If sharp pain occurs slightly vary the electrode positioning or decrease the stimulation energy for comfortable training.

Exercise program
of treatment per week over a period of six weeks -1 session of treatment = 60 minutes regular exercises -Exercises under therapeutic supervision focusing on external rotators and periscapular muscles in patients with functional posterior shoulder instability -Patient-specific, iterative increase of the difficulty and exercise complexity during the training (Level I-III) -Milestones: o Level I: Regain ROM and functional coordination, decrease pain of the shoulder and minimize the occurrence of instability events o Level II: Improve strength, coordination and proprioception (mild to moderate resistance, high repetition), no pain and full functional ROM established o Level III: Further strengthen and increase full dynamic shoulder function, return to patient oriented sports training Experimental intervention: Additional application of neuromuscular electrical stimulation (Neuralign System S, Alyve Medical) -The NMES device remains attached to the shoulder to stimulate hypoactive muscle groups during all exercises.

-
Elevation with lateral resistance ("Lateral wall slide") -Starting position: Patient with the affected arm against a wall -Exercise: Elevation, back of the hand facing the wall, 3x15-20 repetitions -Note: Start to 90° Flexion, slowly progress for pain free motion Exercise 1.2: Two-handed axial loaded elevation -Starting position Patient stands in front of the wall, feet in line with the hip joints, hand palms touching the wall and positioned in line with the shoulder joints -Exercise: Slowly sliding the hands up the wall, 3x15-20 repetitions -Note: Pain free motion, upright posture without increasing lumbar lordosis -Progression: Variable support for the hands (pillow/ball) Exercise 1.3: Prone retroflexion ("I") -Activation of the scapula stabilizers -Starting position: prone position, elbows extended, thumbs in external rotation -Exercise: Retroflexion and scapula retraction holding fully retracted position for 2-5 seconds, 3x15-20 repetitions Exercise 1.4: Prone shoulder external rotation in 20° abduction ("W") -Activation of the scapula stabilizers -Starting position: prone position, elbows flexed with shoulder in 20°abduction -Exercise: Raise arms and scapula retraction holding fully retracted position for 2-5 seconds, 3x15-20 repetitions Exercise 1.5: Isometric external rotation -Strengthening and activation of external rotators -Starting position: Elbows in 90° flexion, shoulder and hand in neutral position -Exercise: Hold isometric external rotation against a resistance band/Wall for 5-10 seconds, 3x15-20 repetitions Level II: Exercise 2.1: Elevation with resistance band -Starting position: Patient stands with the back facing the wall, feet positioned in line with hip joints, knees slightly flexed back and head are leaning against the wall, resistance band in both hands, thumbs point up -Exercise: Head and back are pushed towards the wall, neck is extended, active neutralization of lumbar lordosis.Flexion of both arms with simultaneous external rotation against a resistance band whilst sustaining core body tension, 3x15-20 repetitions -Note: Start to 90° flexion and progress to full ROM Exercise 2.2: Prone horizontal external rotation ("L") -Activation of the scapula stabilizers -Starting position: prone position, shoulder in 90° flexion and abduction, elbows 90° flexed, thumbs points upwards in external rotation -Exercise: External rotation and scapula retraction holding fully retracted position for 2-5 seconds, 3x15-20 repetitions Exercise 2.3: Prone horizontal abduction and external rotation ("T") -Activation of the scapula stabilizers 6 Starting position: prone position, shoulder in 90° flexion and abduction, elbows extended, thumbs points upwards in external rotation -Exercise: Raise arms and scapula retraction holding fully retracted position for 2-5 seconds, 3x15-20 repetitions Exercise 2.4: Concentric external rotation with trunk rotation -Concentric training of external rotators -Starting position: Elbows in 90° flexion and hands neutral, shoulder in 20° internal rotation, resistance band in one hand -Exercise: External rotation against a resistance band, 3x15-20 repetitions -Progression: Starting position in 90° abduction Exercise 2.5: Concentric external rotation in 90° abduction -Concentric training of external rotators -Starting position: Elbows in 90° flexion and abduction positioned on a stable surface, shoulder in 20° internal rotation, resistance band in one hand -Exercise: External rotation against a resistance band, 3x15-20 repetitions Exercise 2.6: Standing One-handed Row: -Starting position: Elbows extended with one hand on a stable surface, resistance band in one hand with anchor at height of feet -Exercise: Pull and scapula retraction ("elbow in back pocket") against a resistance band, 3x15-20 repetitions Exercise 2.7: Eccentric external rotation -Eccentric training of external rotators -Starting position: Elbows in 90° flexion and hands neutral, shoulder in external rotation, resistance band in one hand -Exercise: Slowly rotate internally, 3x15-20 repetitions Exercise 2.8: Wall Scapular Push Up -Starting position: Patient stands in front of the wall, feet in line with the hip joints, hand palms touching the wall and positioned in line with the shoulder joints, the scapulae are retracted -Exercise: Push-ups against the wall by means of shoulder protraction, 3x15-20 repetitions -Note: Elbows extended and pointing towards the ground -Progression: Unstable surface Exercise 2.9: Ball Wall Circles -Starting position: Patient holds a ball in the hand of the affected arm and leans against a wall in 90° abduction -Exercise: Lean body towards the wall whilst stabilizing the position of the hand on the ball, perform small circle motions, 3x15-20 repetitions Exercise 2.10: Contralateral arm raises with ipsilateral leg raise -Starting position: Patient holds a ball in the hand of the affected arm and leans against a wall -Exercise: The contralateral arm is raised, whilst stabilizing the position of the hand on the ball with the ipsilateral leg raised, 3x15-20 repetitions -Note: Activate hip/core in diagonal pattern Level III: Exercise 3.1: Pylometric exercises (two handed chest pass/overhead throwing) -Start with two handed exercises, 3x15-20 repetitions -Progression: Increased weighted medicine ball, faster and higher repetitions Exercise 3.2: Patient oriented sports training (POST) -Complex movement exercises (e.g. one handed throwing, boxing, dribbling) -Progression: Increased repetitions and complexity Exercise 3.3: Reverse Butterfly -Starting position: Arms in 90° abduction and 30° horizontal-flexion, elbows extended, thumbs point upwards, resistance band in both hands -Exercise: Bilateral horizontal extension of both arms and scapula retraction against a resistance band, 3x15-20 repetitions Exercise 3.4: Concentric low row -Starting position: feet positioned in line with hip joints, hips/trunk flexed, resistance band in both hands with anchor at height of feet -Exercise: Concentric low row motion with hips/trunk extension and scapula retraction, 3x15-20 repetitions Exercise 3.5: Diagonal external rotation -Starting position: Elbows in 90° flexion and hands neutral, shoulder in 20° internal rotation, resistance band in one hand -Exercise: Slowly rotate diagonal externally to reach 90° flexion and abduction with additional external trunk rotation, 3x15-20 repetitions Exercise 3.6: Scapular Push Up -Starting position: Push-up position, palms in line with the shoulder joints, shoulder retracted -Exercise: Push-ups with scapula protraction, 3x15-20 repetitions -Note: Elbows extended pointing towards the floor -Progression: Unstable surface

13
Supplementary Table.Comparison of the baseline characteristics of patients with and without an improvement of the Western Ontario Shoulder Instability Index (WOSI) in the neuromuscular electrical stimulation enhanced physiotherapy (NMES-PT) group that exceeds the minimally clinically important difference (MCID) of 10.4 % points.