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Table of Contents
Year : 2018  |  Volume : 11  |  Issue : 4  |  Page : 151-154

The shoulder-pacemaker treatment for functional posterior shoulder instability

Department of Shoulder and Elbow Surgery, Center for Musculoskeletal Surgery, Charité - Universitätsmedizin Berlin, Cambus Virchow Klinikum, Berlin, Germany

Date of Web Publication9-Nov-2018

Correspondence Address:
Prof. Philipp Moroder
Augustenburgerplatz 1, 13353, Berlin
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/HMJ.HMJ_79_18

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Functional posterior shoulder instability (Polar Type III) can lead to posterior subluxation and/or dislocation during shoulder movement. Disturbed activation of external rotators and periscapular muscles generating a force imbalance in the shoulder can result in instability, weakness and pain as the leading symptoms patients present. Recommended conservative treatment is often ineffective, alternative surgical treatment may diminish function even further and aggravate pain. The implementation of the Shoulder-Pacemaker was evaluated in a prospective clinical trial. Patients suffering from functional posterior shoulder instability refractory to previous treatment options should regain glenohumeral shoulder stability after our conservative therapeutic training regime with the Shoulder-Pacemaker. 19 cases with therapy-resistant functional posterior shoulder instability had been included in the Shoulder-Pacemaker therapy-concept. Previously all patients were treated unsuccessfully with at least 3 months of regular physiotherapy. Failed surgical stabilization attempts were not an exclusion criterion. Prior to treatment, a fluoroscopy was performed for diagnosis assurance as well as the evaluation of current MR-Imaging for excluding structural defects. The Shoulder-Pacemaker therapy consisted of a 3- to 6- weeks conservative treatment regime with electric muscle stimulation and regular physiotherapy. For longitudinal evaluation of shoulder function, a specifically developed questionnaire including SSV, ROWE and WOSI score was assessed. After treatment, all patients were very satisfied and fully recommended the Shoulder-Pacemaker therapy. All cases improved in all scores assessed and patients had been able to return to physically demanding and even sporting activities. Patients with completed 3-month follow-up achieved a Rowe score of 92 ± 14, SSV of 95 ± 6%, and WOSI score of 372 ± 181 [Figure 1]. In 2 out of 19 cases the training was not completed because of lack of compliance. No complications were observed. The Shoulder-Pacemaker therapy is a very effective treatment option in patients with functional posterior shoulder instability. Even if previous conservative or surgical stabilization attempts failed, the Shoulder-Pacemaker therapy successfully re-established glenohumeral stability and seems to have a long-lasting effect. Because of the short time of follow up, these results remain preliminary.

Keywords: Shoulder instability, shoulder-pacemaker, therapy concept

How to cite this article:
Moroder P, Danzinger V. The shoulder-pacemaker treatment for functional posterior shoulder instability. Hamdan Med J 2018;11:151-4

How to cite this URL:
Moroder P, Danzinger V. The shoulder-pacemaker treatment for functional posterior shoulder instability. Hamdan Med J [serial online] 2018 [cited 2023 Mar 30];11:151-4. Available from: http://www.hamdanjournal.org/text.asp?2018/11/4/151/245134

  Introduction Top

Generally, active stabilisation of the shoulder joint by muscles of the rotator cuff and periscapular muscles prevents a pathological increased movement of the humeral head. A disturbed muscle activation pattern in terms of a force imbalance of the shoulder-stabilising muscles can result in severe functional shoulder instability and is mostly associated with excessive posterior translation of the humeral head, leading to posterior subluxation and/or dislocation every time the arm passes a particular phase of shoulder movement.[1],[2],[3],[4] Patients suffering from functional shoulder instability report various symptoms. Loss in range of motion, characteristically in elevation and abduction; pain during motion; weakness; blockage and a strong feeling of instability are the main limitations endured. Distinction between a deliberately voluntary posterior displacement of the humeral head, also referred as ‘party trick movement’, and restraining involuntary shoulder instability is crucial, as both could occur in patients suffering from functional posterior shoulder instability.[2],[5] The majority of patients develop their symptoms during childhood or adolescence and suffer from a restricted shoulder function for an extensive period of time.[6] Therefore, emotional stress as well as stigmatisation due to their striking shoulder condition can also occur and should not be overlooked in very young patients.[7] Surgical as well as conservative treatment options often fail to achieve a satisfying outcome in patients suffering from functional shoulder instability. Regular physiotherapy is commonly recommended, and some specialised therapy units treating functional shoulder instability using techniques of intensive inpatient training with tactile biofeedback are described in literature, but they are hardly available in clinical routine.[2] Surgical stabilisation attempts are not recommended as there are no structural defects which could be addressed, often resulting in additional pain and further limitation of shoulder function.[2],[3],[4] Although the last treatment alternative of skilful neglect in terms of a symptomatic therapy has been proposed, it is often not accepted well by the patients.[1]

In a pilot study with our so-called shoulder-pacemaker therapy, we showed that patients suffering from functional posterior shoulder instability could benefit from electric muscle stimulation and were able to re-establish glenohumeral shoulder stability in previously untreatable patients.[7]

Based on our pilot project, we aimed to evaluate the shoulder-pacemaker therapy as a clinical trial in patients suffering from functional posterior shoulder instability where previous conservative or surgical stabilisation attempts have failed. Negatively selected patients participated in a 3- to 6-week prospective trial consisting of the shoulder-pacemaker training regime with regular physiotherapy. We longitudinally assessed the subjective and objective outcome parameters to analyse the effect of this new treatment concept.

  Materials and Methods Top

Patient cohort

Nineteen cases of functional posterior shoulder instability have been included since 2017 (recruiting still ongoining). Prior to the therapeutical training protocol with the shoulder pacemaker, all patients were assessed clinically. All patients suffered from recurrent posterior subluxations and/or dislocation during flexion and/or abduction of the affected shoulder. Additionally, 11 patients could demonstrate a deliberate posterior displacement of their affected shoulder. For exact analysis of the pathological posterior component, a dynamic fluoroscopy has been accomplished prior to the treatment confirming the direction of functional posterior instability. To exclude structural defects of soft-tissue and bony structures, the current magnetic resonance imaging had been assessed. Our cohort consisted of seven men and five women, with a mean age of 21 years (range: 15–32 years). Four patients suffered from shoulder instability in their dominant side; in only one, the non-dominant side was affected and bilateral shoulder instability occurred in seven patients. The mean duration of enduring the first symptoms until participating in the shoulder pacemaker treatment was 5 years (3 months–12 years). As an inclusion criterion, conventional physiotherapy had been attempted in all cases without success. Further, surgical intervention had been performed in three patients. All patients avoided sporting and physical activities because of their severe shoulder restrictions.

Training protocol

The shoulder pacemaker training regime involved regular therapy units including electric muscle stimulation and common physiotherapy. All patients had to participate in a 3-week training programme and had to complete three sessions per week. The therapeutic training regime with the shoulder pacemaker was prolonged for another 3 weeks if symptoms or signs of involuntary posterior shoulder instability persisted. Each therapy unit consisted of 30 min of training with the shoulder pacemaker-activating hypoactive periscapular muscles and external rotators while performing motion exercises. Our shoulder pacemaker concept involved concentric, eccentric and functional movement exercises. In the following 30 min, all patients had to complete the strengthening exercises commonly used in physiotherapy but without the shoulder pacemaker attached. The ensuing strengthening exercises had been selected according to standardised conservative treatment approaches which prior to our clinical intervention had shown to be ineffective in these patients. The stimulation intensity and movement complexity were continually raised throughout the shoulder pacemaker treatment according to the patients’ progress.

Technical background

Electric muscle stimulation uses an electric current to stimulate the selected muscles through transcutaneous electrodes. This transcutaneous electric current can initiate an action potential in electrically excitable cells, such as nerve and muscle cells. Consequently, a nerve impulse or muscle contraction is induced through rectangular compensated direct current. In this shoulder pacemaker treatment, a battery-powered muscle stimulator with a frequency of 35 Hz resulting in tonic contractions of the selected muscle groups was applied. One electrode was used to trigger periscapular muscles medial to the margo medialis of the scapula and another one was used to activate the external rotators of the shoulder [Figure 1]. The highest amount of current that the patients were able to tolerate without pain or muscle ache was used for training purposes.
Figure 1: Placement of the shoulder pacemaker electrodes to achieve a tonic contraction of external rotators and scapula retractors

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Data acquisition

Shoulder function was assessed regularly including a specifically developed questionnaire. Included time points were prior to training, every week during the training, as well as 2 weeks, 4 weeks and 3 months after the training. Outcome scores commonly used in recent studies to assess shoulder function, disability and quality of life as well as pain in patients suffering from shoulder instability had been analysed including the Subjective Shoulder Value, the Rowe Score and the Western Ontario Shoulder Instability Index (WOSI) score. Additionally, macroscopically visible muscle activation patterns and changes in the shoulder contour as signs of dislocation were video documented throughout our clinical intervention.

Ethical considerations

All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975 (in its most recently amended version). Informed consent was obtained from all patients included in the study. Additional informed consent was obtained from all patients for whom identifying information is included in this article. An approval of the local Ethical Committee was obtained prior to the beginning of the study.

  Results Top

Analysing the preliminary results of our still ongoing longitudinal evaluation of patients showed a rapid improvement in all outcome scores. Patients with completed 3-month follow-up after the end of our training protocol achieved an average Rowe score of 92 ± 14 [Figure 2], an average Subjective Shoulder Value of 95 ± 6% [Figure 3] and an average WOSI score of 372 ± 181 [Figure 4].
Figure 2: Change in Rowe score over the course of the training period (1–3 sessions) and the follow-up period (2-week to 3-month follow-up)

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Figure 3: Change in Subjective Shoulder Value over the course of the training period (1–3 sessions) and the follow-up period (2-week to 3-month follow-up)

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Figure 4: Change in Western Ontario Shoulder Instability Index score over the course of the training period (1–3 sessions) and the follow-up period (2-week to 3-month follow-up)

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The majority of cases included had been able to end the shoulder pacemaker training regime after 3 weeks only. Three patients had to extend the clinical intervention for another 3 weeks of training. One suffered from a minor traumatic accident and demanded to prolong the treatment, and the other two patients demonstrated signs of persisting subluxation during end-range abduction. Highly shoulder-demanding activities including volleyball, handball and mixed martial arts could be practiced once again by the patients after a long period of abstinence due to their pathology. In 2 out of 19 cases, the training was not fully completed because of the lack of compliance.

  Discussion Top

Our goal of this prospective clinical trial was to assess the implementation of the shoulder pacemaker therapy in conventionally available conservative treatment protocols. Even if patients were treated unsuccessfully with physiotherapy or surgical interventions prior to the shoulder pacemaker therapy, our preliminary results demonstrated major improvements in all the scores evaluated.

Using electric muscle stimulation to activate hypoactive periscapular and shoulder-stabilising muscles seemed to successfully re-establish glenohumeral stability, even in a negatively selected cohort of patients suffering from functional posterior shoulder instability for a long period of time. Up to 3-month follow-up, the shoulder pacemaker treatment seems to have a remaining effect in eliminating an involuntary excessive posterior translation of the humeral head during shoulder movement after only 3 to 6 weeks of application in most of the patients included. The outcome scores we used were significantly higher than those prior to treatment and all patients had been able to return to physically demanding and even athletic activities. Furthermore, all patients were very satisfied and fully recommended the shoulder pacemaker therapy. No relevant complications were observed during this clinical trial. After the first training session, slight muscle ache occurred in some cases. Nevertheless, our so far collected data remain preliminary due to the follow-up of only 3 months and the small number of available cases.

A recent study used dynamic electromyography to assess the aberrant muscle activation pattern in patients suffering from recurrent shoulder instability. The authors concluded that the key muscles of the shoulder joint, such as the external rotator musculus infraspinatus and the internal rotator muscle latissimus dorsi, were inappropriately inactive in 25% and more active in 80% of patients with posterior shoulder instability, respectively. Further, they surmised that the excess medial rotation of the glenohumeral joint and downward depression of the scapula could result in posterior translation and displacement of the humeral head but could have been prevented through resisted external rotation and abduction during elevation of the arm.[4] Moreover, scapula dyskinesia, also referred as scapula winging, is commonly observed in patients suffering from posterior subluxations in terms of a reversed scapula action, with the inferior angle winging out. Sometimes, even a ‘jerky’ pattern of the scapula can occur instead of the usual smooth fashion of movement.[2]

A conservative plan of treatment described by Takwale et al. showed improvements in patients suffering from recurrent posterior shoulder instability by using the principles of careful explanation, visual analysis of the abnormal muscle couple and programme of retraining of the muscle pattern carried out by specific trained physiotherapists in an inpatient setting. With mainly tactile feedback, they aimed for controlling abnormal primary movement patterns and inhibiting hyperactive muscles through strengthening the antagonists. Even after 2 years, 82% of their patients had gained freedom from their symptoms without relapse.[2] On the other hand, an inpatient therapeutic training regime realised by highly specialised physiotherapist for functional shoulder instability is usually not available and the presented results so far were not repeatable in clinical routine. In contrast, the shoulder pacemaker is easy to implement into the setting of conventional physiotherapy and improvements can be achieved surprisingly fast.

To summarise, patients suffering from functional posterior shoulder instability, even refractory to previous conservative or surgical interventions, seem to quickly regain lasting shoulder stability through the shoulder pacemaker therapy.

Financial support and sponsorship


Conflicts of interest

PD Dr. Med. Univ. Philipp Moroder is consultant for NCS who is developing an electrical muscle stimulator called the shoulder pacemaker.

  References Top

Kuroda S, Sumiyoshi T, Moriishi J, Maruta K, Ishige N. The natural course of atraumatic shoulder instability. J Shoulder Elbow Surg 2001;10:100-4.  Back to cited text no. 1
Takwale VJ, Calvert P, Rattue H. Involuntary positional instability of the shoulder in adolescents and young adults. Is there any benefit from treatment? J Bone Joint Surg Br 2000;82:719-23.  Back to cited text no. 2
Jaggi A, Lambert S. Rehabilitation for shoulder instability. Br J Sports Med 2010;44:333-40.  Back to cited text no. 3
Jaggi A, Noorani A, Malone A, Cowan J, Lambert S, Bayley I, et al. Muscle activation patterns in patients with recurrent shoulder instability. Int J Shoulder Surg 2012;6:101-7.  Back to cited text no. 4
[PUBMED]  [Full text]  
Lewis A, Kitamura T, Bayley JI. (ii) The classification of shoulder instability: New light through old windows! Curr Orthopaed 2004;18:97-108.  Back to cited text no. 5
Huber H, Gerber C. Voluntary subluxation of the shoulder in children. A long-term follow-up study of 36 shoulders. J Bone Joint Surg Br 1994;76:118-22.  Back to cited text no. 6
Moroder P, Minkus M, Böhm E, Danzinger V, Gerhardt C, Scheibel M, et al. Use of shoulder pacemaker for treatment of functional shoulder instability: Proof of concept. Obere Extrem 2017;12:103-8.  Back to cited text no. 7


  [Figure 1], [Figure 2], [Figure 3], [Figure 4]


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