Characteristics of functional shoulder instability

Abstract

Background: Pathologic activation pattern of muscles can cause shoulder instability. We propose to call this pathology functional shoulder instability (FSI). The purpose of this prospective study was to provide an in-detail description of the characteristics of FSI. Methods: In the year 2017, a total of 36 consecutive cases of FSI presenting to our outpatient clinic were prospectively collected. Diagnostic investigation included a pathology-specific questionnaire, standardized clinical scores, clinical examination, psychological evaluation, video and dynamic fluoroscopy documentation of the instability mechanism, as well as magnetic resonance imaging (MRI). In a final reviewing process, the material from all collected cases was evaluated and, according to the observed pattern, different subtypes of FSI were determined and compared. Results: Based on the pathomechanism, positional FSI (78%) was distinguished from nonpositional FSI (22%). Controllable positional FSI was observed in 6% of all cases and noncontrollable positional FSI in 72%, whereas controllable and noncontrollable nonpositional FSI were each detected in 11% of the cases. The different subtypes of FSI showed significant differences in all clinical scores (Western Ontario Shoulder Instability Index: P ¼ .002, Rowe Score: P ¼ .001, Subjective Shoulder Value: P ¼ .001) and regarding functional impairment (shoulder stability: P < .001, daily activities: P ¼ .001, sports activities: P < .001). Seventy-eight percent had posterior, 17% anterior, and 6% multidirectional instability. Although several patients showed constitutional glenoid shape alterations or soft tissue hyperlaxity, only few patients with acquired minor structural defects were observed. Conclusion: FSI can be classified into 4 subtypes based on pathomechanism and volitional control. Depending on the subtype, patients show different degrees of functional impairment. The majority of patients suffer from unidirectional posterior FSI. Level of evidence: Level IV; Case Series; Prognosis Study Ó 2019 The Author(s). This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/). Keywords: Shoulder instability; functional shoulder instability; voluntary shoulder instability; positional shoulder instability; noncontrollable shoulder instability; multidirectional shoulder instability; posterior shoulder instability; anterior shoulder instability This study was performed at

Delphi survey on conventional conservative treatment of functional posterior shoulder instability

“…Finally, it must be stated that the success of a dedicated exercise program depends on the correct diagnosis. There-fore, it is of crucial importance to clearly distinguish posterior FSI from posterior instability caused by structural defects and to identify the true direction of instability, which is not always as easy as it seems [15,17].…”

“…Shoulder instability can be caused either by structural defects such as bony or soft tissue lesions or by pathological activation patterns of the rotator cuff and periscapular musculature [6]. In contrast tostructural shoulderinstability, this type of instability has been described as "functional shoulder instability" (FSI; [15]). While anterior instability is more common in patients with structural defects, many patients with FSI suffer from posterior instability [15].…”

“…In contrast tostructural shoulderinstability, this type of instability has been described as "functional shoulder instability" (FSI; [15]). While anterior instability is more common in patients with structural defects, many patients with FSI suffer from posterior instability [15]. The ABC classification for posterior shoulder instability (PSI) distinguishes between functional posterior shoulder instability (B1) and structural posterior shoulder instability (B2; [16]).…”

“…The ABC classification for posterior shoulder instability (PSI) distinguishes between functional posterior shoulder instability (B1) and structural posterior shoulder instability (B2; [16]). Functional PSI can either be a controllable or a non-controllable condition depending on the patient's ability towillfullycontrol the instability episodes [15].…”

The efficacy of a phone assistance nursing program for functional outcomes in patients after shoulder instability surgery

“…Shoulder instability is one of the most familiar clinical manifestations of sports trauma. [ 1 , 2 ] The structure of glenohumeral joint is unstable, which is the most common dislocation joint. [ 3 ] The dislocation of anterior shoulder is the most familiar type, which accounts for 90%.…”