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

Purpose The purpose of this study was to investigate the anatomical feasibility of a middle trapezius transfer below the acromion for treatment of irreparable supraspinatus tendon tears. Methods This study involved 20 human cadaveric shoulders in 10 full-body specimens. One shoulder in each specimen was dissected and assessed for muscle and tendon extent, force vectors, and distance to the neurovascular structures. The opposite shoulder was used to evaluate the surgical feasibility of the middle trapezius transfer via limited skin incisions along with an assessment of range of motion and risk of neurovascular injury following transfer. Results The harvested acromial insertion of the middle trapezius tendon showed an average muscle length of 11.7 ± 3.0 cm, tendon length of 2.7 ± 0.9 cm, footprint length of 4.3 ± 0.7 cm and footprint width of 1.4 ± 0.5 cm. The average angle between the non-transferred middle trapezius transfer and the supraspinatus was 33 ± 10° in the transversal plane and 34 ± 14° in the coronal plane. The mean distance from the acromion to the neurovascular bundle was 6.3 ± 1.3 cm (minimum: 4.0 cm). During surgical simulation there was sufficient excursion of the MTT without limitation of range of motion in a retracted scapular position but not in a protracted position. No injuries to the neurovascular structures were noted. Conclusion Transfer of the acromial portion of the middle trapezius for replacement of an irreparable supraspinatus seems to be feasible in terms of size, vector, excursion, mobility and safety. However, some concern regarding sufficiency of transfer excursion remains as scapula protraction can increase the pathway length of the transfer. Level of evidence Basic Science Study/Anatomical Study

BackgroundFunctional shoulder instability (polar type III) is caused by underactivity of rotator cuff and periscapular muscles, which leads to subluxation or dislocation during shoulder movement. While surgical treatment has shown no benefits, aggravates pain, and frequently diminishes function even further, conservative treatment is often ineffective as well.ObjectivesThe aim was to investigate the effectiveness of a “shoulder pacemaker” device that stimulates underactive muscles in patients with functional instability during shoulder movement in order to re-establish glenohumeral stability.Patients and methodsThree patients with unsuccessfully treated functional shoulder instability causing pain, emotional stress, as well as limitations during daily activities and sports participation were enrolled in this pilot project. The device was used to stimulate the external rotators of the shoulder and retractors of the scapula. Pain level, subjective shoulder instability, range of motion, visible aberrant muscle activation, and signs of dislocation were compared when the device was switched on and off.ResultsNo changes were observed when the device was attached but switched off. When the device was switched on, all patients were able to move their arms freely without pain, discomfort, or subjective or objective signs of instability. All patients rated this as an excellent experience and volunteered to train further with the device. No complications were observed.ConclusionThe electric stimulation of hypoactive rotator cuff and periscapular muscles by means of the shoulder pacemaker successfully re-establishes stability in patients with functional shoulder instability during the time of application. Video onlineThe online version of this article (doi: 10.1007/s11678-017-0399-z) contains the video: “The Shoulder-Pacemaker: treatment of functional shoulder instability with pathological muscle activation pattern”. Video by courtesy of P. Moroder, M. Minkus, E. Böhm, V. Danzinger, C. Gerhardt and M. Scheibel, Charité Universitätsmedizin Berlin 2017, all rights reserved

Background: Pathological muscle activation patterns of the external rotators and periscapular muscles can result in posterior positional functional shoulder instability (PP-FSI). In several patients, physical therapy and surgical treatment are not successful. Purpose: The shoulder-pacemaker treatment concept was evaluated prospectively in patients with PP-FSI and previously failed conventional therapy attempt. Study Design: Case series; Level of evidence, 4. Methods: A negative selection of 24 consecutive cases of noncontrollable PP-FSI in 16 patients with previously failed conventional therapy were included in this prospective study. The shoulder-pacemaker treatment consisted of an electrical muscle stimulation–based therapy protocol with 9 to 18 one-hour treatment sessions. Two patients were excluded because of nonadherence to the training schedule, leaving a final study cohort of 21 cases in 14 patients. Follow-up included assessment of clinical function, impairment during daily activities and sports, satisfaction, Western Ontario Shoulder Instability Index (WOSI), Rowe score, and Subjective Shoulder Value at 0 weeks, 2 weeks, 4 weeks, 3 months, 6 months, 12 months, and 24 months after intervention. Results: WOSI, Subjective Shoulder Value, and Rowe score showed a highly significant improvement at all time points of follow-up ( P < .001). Young age ( P = .005), low weight ( P = .019), shoulder activity level ( P = .003), unilateral affliction ( P = .046), and higher baseline WOSI score ( P = .04) were associated with a better treatment effect. Cases with increased glenoid retroversion, posterior scapulohumeral decentering, and dysplastic bony glenoid shape showed a trend toward shorter treatment effect duration. No complications during the intervention or follow-up period were observed. Conclusion: The shoulder-pacemaker therapy concept is an effective treatment with rapid improvement and sustained outcome over the course of 2 years in patients with noncontrollable PP-FSI with previously failed conventional treatment. Young and more athletic patients with lower weight and unilateral pathology respond best to the treatment.

Background: Head-split fractures are a subgroup of proximal humeral fractures in which the fracture line affects the articular surface. Limited data are available regarding outcomes and risk factors for failure following surgical treatment of this rare fracture type. Methods: Of 45 patients with head-split fractures identified, a total of 30 (67%) were included in this retrospective study, with a mean follow-up of 49 ± 18 months (range, 12 to 83 months). Of those 30, 24 were treated with open reduction and internal fixation (ORIF), 4 with reverse total shoulder arthroplasty (RTSA), and 2 with hemiarthroplasty. Subjective Shoulder Value, Simple Shoulder Test, Constant score, and biplanar radiographs were assessed. Fracture pattern, quality of reduction, eventual complications, revision procedures, and clinical failure (adjusted Constant score < 40) were analyzed, and risk factors for failure were calculated. Results: The overall complication rate was 83% (ORIF: 21 of 24 [88%]; RTSA: 3 of 4 [75%]; and hemiarthroplasty: 1 of 2 [50%]). The most common complications following ORIF were humeral head osteonecrosis (42%), malunion of the lesser tuberosity (33%), and screw protrusion (29%), whereas all complications following RTSA were related to tuberosity problems. Revision was performed in 7 of 24 (29%) of initial ORIF patients, and no revisions were performed in RTSA or hemiarthroplasty patients. Four patients (17%) who underwent primary ORIF underwent conversion to RTSA, and 3 patients (12.5%) had screw removal due to penetration. The overall clinical failure rate was 50% (ORIF: 12 of 24 [50%]; RTSA: 1 of 4 [25%]; and hemiarthroplasty: 2 of 2 [100%]). No significant association was found between preoperative factors and clinical failure. ORIF and primary RTSA showed higher average clinical outcome scores than primary hemiarthroplasty and secondary RTSA. In general, patients who required revision had worse Subjective Shoulder Value (p = 0.014), Simple Shoulder Test (p = 0.028), and adjusted Constant scores (p = 0.069). Conclusions: Head-split fractures of the humerus treated with ORIF showed high complication and revision rates. RTSA resulted in comparable clinical outcomes and complication rates; however, the complications associated with RTSA were mostly related to tuberosity problems, which in this small series did not require revision. Therefore, RTSA may be the most predictable treatment option for head-split fractures in elderly patients. Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete list of levels of evidence.