ABC classification of posterior shoulder instability

SECEC Didier Patte Prize 2023: the ABC classification of posterior shoulder instability

BACKGROUND

The ABC classification has recently been proposed as a comprehensive classification system for posterior shoulder instability (PSI). The purpose of this study was to analyze the comprehensiveness as well as inter-rater and intrarater reliability of the ABC classification.

METHODS

All consecutive patients presenting with unidirectional PSI from June 2019 to June 2021 were included in a prospective study. No patients were excluded, leaving a consecutive series of 100 cases of PSI in 91 patients. All recorded clinical and imaging data were used to create anonymized clinical case vignettes, which were evaluated twice according to the ABC classification at the end of the recruitment period in random sequential order by 4 independent raters (2 experienced shoulder surgeons and 2 orthopedic residents) to analyze the comprehensiveness as well as inter-rater and intrarater reliability of the ABC classification for PSI and to describe differences in characteristics among subtypes. Group A was defined as a first-time singular PSI event <3 months in the past regardless of etiology and is further subdivided into type 1 and type 2 depending on the occurrence of a subluxation (A1) or dislocation (A2). Group B comprises recurrent dynamic PSI regardless of time since onset and is further subdivided by the cause of instability into functional (B1) and structural (B2) dynamic PSI. Group C includes chronic static PSI with posterior humeral decentering that can be either constitutional (C1) or acquired (C2).

RESULTS

None of the cases was deemed unsuitable to be classified based on the proposed system by the observers. After consensus agreement between the 2 expert raters, 16 cases were attributed to group A (8 type A1 and 8 type A2); 64, to group B (33 type B1 and 31 type B2); and 20, to group C (11 type C1 and 9 type C2). The expert raters agreed on the classification subtypes in 99% and 96% of the cases during the first rating and second rating, respectively (intraclass correlation coefficients [ICCs], 0.998 and 0.99, respectively). The intraobserver reliability was excellent for both raters. The beginners reached the same conclusion as the consensus agreement in 94% of the cases (ICC, 0.99) and 89% of the cases (ICC, 0.97) during the first round and 94% each (ICC, 0.97) during the second round. The intraobserver reliability was excellent for both beginners. Overall, discrepancies between raters were found between groups B1 and B2 (n = 14), groups B2 and C2 (n = 4), groups B1 and C1 (n = 1), and groups A1 and B2 (n = 1). In general, each subtype showed distinctive clinical and imaging characteristics that facilitated the diagnosis.

CONCLUSION

The presented ABC classification for PSI is a comprehensive classification with a high reliability and reproducibility. However, a gradual transition and potential progression between the subtypes of PSI must be considered. The reliable distinction between different subtypes of PSI based on etiology and pathomechanism provides a standardized basis for future investigations on treatment recommendations.

Posterior Shoulder Instability, Part I-Diagnosis, Nonoperative Management, and Labral Repair for Posterior Shoulder Instability-An International Expert Delphi Consensus Statement

PURPOSE

To establish consensus statements on the diagnosis, nonoperative management, and labral repair for posterior shoulder instability.

METHODS

A consensus process on the treatment of posterior shoulder instability was conducted, with 71 shoulder/sports surgeons from 12 countries participating on the basis of their level of expertise in the field. Experts were assigned to 1 of 6 working groups defined by specific subtopics within posterior shoulder instability. Consensus was defined as achieving 80% to 89% agreement, whereas strong consensus was defined as 90% to 99% agreement, and unanimous consensus was indicated by 100% agreement with a proposed statement.

RESULTS

Unanimous agreement was reached on the indications for nonoperative management and labral repair, which include whether patients had primary or recurrent instability, with symptoms/functional limitations, and whether there was other underlying pathology, or patient's preference to avoid or delay surgery. In addition, there was unanimous agreement that recurrence rates can be diminished by attention to detail, appropriate indication and assessment of risk factors, recognition of abnormalities in glenohumeral morphology, careful capsulolabral debridement and reattachment, small anchors with inferior placement and multiple fixation points that create a bumper with the labrum, treatment of concomitant pathologies, and a well-defined rehabilitation protocol with strict postoperative immobilization.

CONCLUSIONS

The study group achieved strong or unanimous consensus on 63% of statements related to the diagnosis, nonoperative treatment, and labrum repair for posterior shoulder instability. The statements that achieved unanimous consensus were the relative indications for nonoperative management, and the relative indications for labral repair, as well as the steps to minimize complications for labral repair. There was no consensus on whether an arthrogram is needed when performing advanced imaging, the role of corticosteroids/orthobiologics in nonoperative management, whether a posteroinferior portal is required.

LEVEL OF EVIDENCE

Level V, expert opinion.

Diagnosis and treatment of posterior shoulder instability based on the ABC classification

Posterior shoulder instability (PSI) is less common than anterior shoulder instability, accounting for 2-12% of total shoulder instability cases. However, a much higher frequency of PSI has been recently indicated, suggesting that PSI accounts for up to 24% of all young and active patients who are surgically treated for shoulder instability. This differentiation might be explained due to the frequent misinterpretation of vague symptoms, as PSI does not necessarily present as a recurrent posterior instability event, but often also as mere shoulder pain during exertion, limited range of motion, or even as yet asymptomatic concomitant finding. In order to optimize current treatment, it is crucial to identify the various clinical presentations and often unspecific symptoms of PSI, ascertain the causal instability mechanism, and accurately diagnose the subgroup of PSI. This review should guide the reader to correctly identify PSI, providing diagnostic criteria and treatment strategies.

Arthroscopic Posterior Bone Block Stabilization Using a Tricortical Autograft of the Ipsilateral Scapular Spine

Posterior bone grafting represents an emerging therapeutic approach for addressing recurrent instability in the posterior shoulder, particularly when coupled with substantial glenoid bone loss. Although not as prevalent as anterior instability, recent years have witnessed the development of numerous open and arthroscopic bony reconstruction methods. A technical gold standard for posterior bone grafting remains undefined, leading to ongoing advancements in bone grafting techniques. In response to past challenges associated with screw fixation, metal-free arthroscopic fixation procedures have been introduced to the realm of bone grafting. These metal-free methods often entail intricate transglenoid drilling, which poses potential surgical complexities and risks to both posterior and anterior soft tissues, as well as neurovascular structures. Therefore, we introduce an arthroscopic approach to posterior bone grafting using PEEK (polyether ether ketone) anchors with interconnected sutures and a scapular spine autograft. This method overcomes previous hurdles by facilitating the restoration of the posterior glenoid bone stock with precise positioning and secure fixation of the tricortical scapular spine bone autograft.

Differences in Osseous Shoulder Morphology, Scapulothoracic Orientation, and Muscle Volume in Patients With Constitutional Static Posterior Shoulder Instability (Type C1) Compared With Healthy Controls

BACKGROUND

Constitutional static posterior humeral decentering (type C1 according to ABC Classification) has been recognized as a pre-osteoarthritic deformity that may lead to early-onset posterior decentering osteoarthritis at a young age. Therefore, it is important to identify possible associations of this pathologic shoulder condition to find more effective treatment options.

PURPOSE

To perform a comprehensive analysis of all parameters reported to be associated with a C1 shoulder-including the osseous shoulder morphology, scapulothoracic orientation, and the muscle volume of the shoulder girdle in a single patient cohort.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

A retrospective, comparative study was conducted analyzing 17 C1 shoulders in 10 patients who underwent magnetic resonance imaging (MRI) with the complete depiction of the trunk from the base of the skull to the iliac crest, including both humeri. The mean age of the patients was 33.5 years, and all patients were men. To measure and compare the osseous shoulder morphology (glenoid version, glenoid offset, humeral torsion, anterior acromial coverage, posterior acromial coverage, posterior acromial height, and posterior acromial tilt) and scapulothoracic orientation (scapular protraction, scapular internal rotation, scapular upward rotation, scapular translation, scapular tilt, and thoracic kyphosis), these patients were matched 1 to 4 according their age, sex, and affected side with shoulder-healthy patients who had received positron emission tomography (PET)-computed tomography. To measure and compare the muscle volume of the shoulder girdle (subscapularis, infraspinatus/teres minor, supraspinatus, trapezius, deltoid, latissimus dorsi/teres major, pectoralis major, and pectoralis minor), patients were matched 1 to 2 with patients who had received PET-MRI. Patients with visible pathologies of the upper extremities were excluded.

RESULTS

The C1 group had a significantly higher glenoid retroversion, increased anterior glenoid offset, reduced humeral retrotorsion, increased anterior acromial coverage, reduced posterior acromial coverage, increased posterior acromial height, and increased posterior acromial tilt compared with controls (P < .05). Decreased humeral retrotorsion showed significant correlation with higher glenoid retroversion (r = -0.742; P < .001) and higher anterior glenoid offset (r = -0.757; P < .001). Significant differences were found regarding less scapular upward rotation, less scapular tilt, and less thoracic kyphosis in the C1 group (P < .05). The muscle volume of the trapezius and deltoid was significantly higher in the C1 group (P < .05).

CONCLUSION

Patients with C1 shoulders differ from healthy controls regarding osseous scapular and humeral morphology, scapulothoracic orientation, and shoulder girdle muscle distribution. These differences may be crucial in understanding the delicate balance of glenohumeral centering.

Management of Bone Loss in Posterior Glenohumeral Shoulder Instability: Current Concepts

» Posterior glenohumeral instability is relatively uncommon compared with anterior instability, but is becoming an increasingly recognized and surgically managed shoulder pathology.» Soft-tissue stabilization alone may not be sufficient in patients who present with substantial bone loss to the posterior glenoid and/or the anterior humeral head.» For posterior glenoid defects, posterior glenoid osteoarticular augmentation can be used, and posterior glenoid opening wedge osteotomy can be considered in cases of posterior instability with pathologic retroversion.» For humeral head lesions, several surgical treatment options are available including subscapularis transposition into the humeral head defect, autograft or allograft reconstruction, humeral rotation osteotomy, and shoulder arthroplasty.

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

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.

Bone loss in shoulder instability: putting it all together

Glenohumeral bone loss is frequently observed in cases of recurrent anterior and posterior shoulder instability and represents a risk factor for failure of nonoperative treatment. Patients with suspected glenoid or humeral bone loss in the setting of recurrent instability should be evaluated with a thorough history and physical examination, as well as advanced imaging including computed tomography (CT) and/or magnetic resonance imaging (MRI). In cases of both anterior and posterior instability, the magnitude and location of bone loss should be determined, as well as the relationship between the glenoid track (GT) and any humeral defects. While the degree and pattern of osseous deficiency help guide treatment, patient-specific risk factors for recurrent instability must also be considered when determining patient management. Treatment options for subcritical anterior bone loss include labral repair and capsular plication, while more severe deficiency should prompt consideration of bony augmentation including coracoid transfer or free bone block procedures. Concomitant humeral lesions are treated according to the degree of engagement with the glenoid rim and may be addressed with soft tissue remplissage or bony augmentation procedures. While critical and subcritical thresholds of glenoid bone loss guide the management of anterior instability, such thresholds are less defined in the setting of posterior instability. Furthermore, current treatment algorithms are limited by a lack of long-term comparative studies. Future high-quality studies as well as possible modifications in indications and surgical technique are required to elucidate the optimal treatment of anterior, posterior, and bipolar glenohumeral bone loss in the setting of recurrent shoulder instability.

Arthroscopic Posterior Bankart Repair Using the Wilmington Portal to Facilitate Suture Anchor Implantation

Posterior shoulder instability (PSI) accounts for 2% to 10% of all shoulder instability, with recurrent posterior subluxation being the most common type. One of the most important risk factors is the presence of an anterior humeral notch (so-called reverse Hill-Sachs lesion), and the most common lesion in PSI is a posterior labral lesion. When conservative treatment fails, surgery is recommended to provide long-term stability, manage pain, and enable a return to previous activity levels. Most posterior labral tears are treated by an arthroscopic posterior Bankart procedure. Visualization of the posterior aspect of the glenohumeral joint is technically challenging in this procedure. The instrumental portal is also a matter of concern because there is no rotator interval posteriorly for cannula placement. The purpose of this article is to propose a technique using a secondary posterolateral Wilmington instrumental portal to perform easy and reproducible placement of the posterior suture anchor at a 45° angle to the glenoid rim. We recommend implementing this technique in patients with painful PSI or with a type B2 lesion according to the Moroder classification.

Arthroscopic Posterior Capsulolabral Repair With Suture-First Versus Anchor-First Technique in Patients With Posterior Shoulder Instability (Type B2): Clinical Midterm Follow-up

Background

Isolated soft tissue injuries of the posterior capsulolabral complex can be addressed arthroscopically, with various anchor systems available for repair.

Purpose

To evaluate clinical and patient-reported outcomes after arthroscopic capsulolabral repair in patients with posterior shoulder instability (PSI) and to compare differences in outcomes between patients treated with a suture-first technique (PushLock anchor) and an anchor-first technique (FiberTak all-suture anchor).

Study Design

Cohort study; Level of evidence, 3.

Methods

Included were 32 patients with dynamic structural PSI (type B2 according to the ABC classification) treated with an arthroscopic posterior capsulolabral repair. After a mean follow-up time of 4.8 ± 3.4 years (range, 2-11) patients were evaluated clinically, and standardized outcome scores were obtained for the Subjective Shoulder Value (SSV), the Western Ontario Shoulder Instability Index (WOSI), Rowe, Kerlan-Jobe Orthopaedic Clinic (KJOC), patient satisfaction (0-5 [best]), and pain on a visual analog scale (VAS; 0-10 [worst]).

Results

The overall satisfaction level with the outcome of the surgery was 4.6 ± 0.5 (range, 4-5). No patient suffered from instability events. The mean VAS level for pain was 0.4 ± 0.9 (range, 0-4) at rest and 1.9 ± 2.0 (range, 0-6) during motion. The mean SSV was 80 ± 17 (range, 30-100), the mean postoperative WOSI score 75% ± 19% (range, 18-98), the mean Rowe score 78 ± 20 (range, 10-100), and the mean KJOC score was 81 ± 18 (range, 40-100) for the entire cohort. There was no significant difference between the techniques with regard to range of motion, strength, or clinical outcome scores.

Conclusion

Arthroscopic posterior capsulolabral repair was a satisfactory method to treat structural PSI type B2 with regard to stability, pain relief, and functional restoration. The majority of patients had good outcomes. No differences in outcomes were observed between the anchor-first and suture-first techniques.

Patient-specific risk profile associated with early-onset primary osteoarthritis of the shoulder: is it really primary?

INTRODUCTION

Although age is considered to be the major risk factor of primary glenohumeral osteoarthritis (GOA), younger population may suffer from degenerative changes of the shoulder joint without evidence of any leading cause. The purpose of this study was to investigate the risk profile in young patients suffering from presumably primary GOA.

METHODS

A consecutive group of 47 patients undergoing primary shoulder arthroplasty for early-onset GOA below the age of 60 years at time of surgery was retrospectively identified and prospectively evaluated. Patients with identifiable cause for GOA (secondary GOA) were excluded. The resulting 32 patients (mean age 52 ± 7 years; 17 male, 15 female) with primary GOA were matched by age (± 3 years) and gender to 32 healthy controls (mean age 53 ± 7 years; 17 male, 15 female). Demographic data and patient-related risk factors were assessed and compared among both groups to identify extrinsic risk factors for primary GOA. Patients were further subdivided into a group with concentric GOA (group A) and a group with eccentric GOA (group B) to perform a subgroup analysis.

RESULTS

Patients had a significantly higher BMI (p = 0.017), were more likely to be smokers (p < 0.001) and to have systematic diseases such as hypertension (p = 0.007) and polyarthritis (p < 0.001) and a higher Shoulder Activity Level (SAL) (p < 0.001) when compared to healthy controls. Furthermore, group B had a significantly higher SAL not only compared to healthy controls but also to group A, including activities such as combat sport (p = 0.048) and weightlifting (p = 0.01).

CONCLUSIONS

Several patient-specific risk factors are associated with primary GOA in the young population, as well as highly shoulder demanding activities in the development of eccentric GOA. Consequently, a subset of young patients with eccentric primary GOA could in reality be secondary due to a muscular imbalance between internal and external rotators caused by improper weight training.

LEVEL OF EVIDENCE

III, Case-Control study.

Arthroscopic Posterior Articular Coverage and Shift (PACS) Procedure for Treatment of Preosteoarthritic Constitutional Static Posterior Shoulder Instability (Type C1)

BACKGROUND

Different joint-preserving techniques for treatment of preosteoarthritic, constitutional static (type C1) posterior shoulder instability (PSI) have been proposed, including posterior glenoid open wedge osteotomy and bone graft augmentation. However, the techniques are demanding, the reported complication and reoperation rates are high, and posterior decentering cannot reliably be reversed.

PURPOSE

To assess the clinical and radiological longitudinal outcomes of patients with type C1 PSI after arthroscopic posterior articular coverage and shift (PACS) surgery.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

We performed a retrospective analysis of a prospective database with longitudinal follow-up including 14 shoulders in 13 patients who underwent an arthroscopic PACS procedure for symptomatic preosteoarthritic constitutional static posterior instability (type C1) with previous failed nonoperative treatment. Patients were clinically evaluated before surgery and at 3, 6, 12, and 24 months postoperatively in terms of satisfaction and pain levels as well as standardized physical examination, Subjective Shoulder Value (SSV), Western Ontario Shoulder Instability Index (WOSI) score, Constant score, and Rowe score. Preoperative, postoperative, and follow-up magnetic resonance imaging scans were obtained in all patients. A paired 2-sample t test was used to compare changes in continuous variable parameters over time. Correlation analyses were performed using the Pearson correlation coefficient.

RESULTS

All outcome scores and the pain level improved significantly from preoperatively to postoperatively, and the improvement was sustained over the follow-up period of 2 years (pain level, 6.4 preoperatively vs 3.3 at 2 years, P < .001; SSV, 40 vs 70, P = .001; WOSI, 33 vs 56, P = .001; Constant, 70 vs 79, P = .049; Rowe, 52 vs 76, P < .001). The mean glenohumeral and scapulohumeral subluxation indices were significantly lower in the early postoperative period compared with preoperative measurements (glenohumeral, 52% ± 6% vs 58% ± 10%, P = .02; scapulohumeral, 70% ± 8%; vs 77% ± 9%, P = .002, respectively); however, they returned to baseline values at follow-up (57% ± 7% vs 58% ± 10%, P = .7; 75% ± 6% vs 77% ± 9%, P = .4, respectively). A high scapulohumeral subluxation index, excessive glenoid retroversion, and increased posterior positioning of the humeral head in relation to scapular blade axis and older age were correlated with worse clinical outcomes.

CONCLUSION

Over the follow-up period of 2 years, the PACS procedure significantly improved outcome scores in patients who had preosteoarthritic constitutional static posterior shoulder instability, especially in younger patients with less severe glenoid retroversion and posterior decentering of the humeral head. However, similar to other techniques, the PACS procedure needs to be considered a symptomatic therapy that does not reverse the underlying cause or stop the progressive pathology.

Comprehensive management of posterior shoulder instability: diagnosis, indications, and technique for arthroscopic bone block augmentation

Recurrent posterior glenohumeral instability is an entity that demands a high clinical suspicion and a detailed study for a correct approach and treatment. Its classification must consider its biomechanics, whether it is due to functional muscular imbalance or to structural changes, volition, and intentionality.

Due to its varied clinical presentations and different structural alterations, ranging from capsule-labral lesions and bone defects to glenoid dysplasia and retroversion, the different treatment alternatives available have historically had a high incidence of failure.

A detailed radiographic assessment, with both CT and MRI, with a precise assessment of glenoid and humeral bone defects and of glenoid morphology, is mandatory.

Physiotherapy focused on periscapular muscle reeducation and external rotator strengthening is always the first line of treatment. When conservative treatment fails, surgical treatment must be guided by the structural lesions present, ranging from soft tissue repair to posterior bone block techniques to restore or increase the articular surface.

Bone block procedures are indicated in cases of recurrent posterior instability after the failure of conservative treatment or soft tissue techniques, as well as symptomatic demonstrable nonintentional instability, presence of a posterior glenoid defect >10%, increased glenoid retroversion between 10 and 25°, and posterior rim dysplasia. Bone block fixation techniques that avoid screws and metal allow for satisfactory initial clinical results in a safe and reproducible way.

An algorithm for the approach and treatment of recurrent posterior glenohumeral instability is presented, as well as the author’s preferred surgical technique for arthroscopic posterior bone block.

Conservative treatment of acute traumatic posterior shoulder dislocations (Type A) is a viable option especially in patients with centred joint, low gamma angle, and middle or old age

PURPOSE

Purpose of this study was to evaluate the mid- to long-term outcome after conservatively treated first-time posterior shoulder dislocations and to determine structural defects associated with failure.

METHODS

In this multi-centric retrospective study, 29 shoulders in 28 patients with first-time acute posterior shoulder dislocation (Type A1 or A2 according to the ABC classification) and available cross-sectional imaging were included. Outcome scores as well as radiological and magnetic resonance imaging were obtained at a mean follow-up of 8.3 ± 2.7 years (minimum: 5 years). The association of structural defects with redislocation, need for secondary surgery, and inferior clinical outcomes were analysed.

RESULTS

Redislocation occurred in six (21%) shoulders and nine shoulders (31%) underwent secondary surgery due to persistent symptoms. The posttraumatic posterior glenohumeral subluxation was higher in the redislocation group compared to the no redislocation group; however, statistical significance was not reached (61.9 ± 12.5% vs. 50.6 ± 6.4%). Furthermore, a higher adapted gamma angle was observed in the failed conservative treatment group versus the conservative treatment group, similarly without statistically significant difference (97.8° ± 7.2°, vs. 93.3° ± 9.7°). The adapted gamma angle was higher than 90° in all patients of failed conservative therapy and the redislocation group. An older age at the time of dislocation showed a significant correlation with better clinical outcomes (SSV: r = 0.543, p = 0.02; ROWE: r = 0.418, p = 0.035 and WOSI: r = 0.478, p = 0.045). Posterior glenohumeral subluxation after trauma correlated with a worse WOSI (r = - 0.59, p = 0.02) and follow-up posterior glenohumeral decentring (r = 0.68, p = 0.007). The gamma angle (r = 0.396, p = 0.039) and depth of the reverse Hill-Sachs lesion (r = 0.437, p = 0.023) correlated significantly with the grade of osteoarthritis at follow-up.

CONCLUSION

Conservative treatment is a viable option in patients with an acute traumatic posterior shoulder dislocation with good outcome after mid- and long-term follow-up especially in patients with centred joint, low gamma angle, and middle or old age.

LEVEL OF EVIDENCE

IV.

Treatment of chronic locked posterior dislocation of the shoulder with the modified McLaughlin procedure

BACKGROUND

Locked posterior dislocation of the shoulder (LPDS) is a challenging condition for the orthopedic surgeon. The problem with cases of chronic LPDS is that they may result in worse clinical outcomes because the size of the reverse Hill-Sachs lesion and cartilage damage can increase over time. Multiple treatment strategies have been reported in the literature for the treatment of chronic cases. The purpose of this study was to report our experience with the modified McLaughlin technique for the treatment of chronic LPDS and evaluate the mid- and long-term functional outcomes.

METHODS

This was a retrospective single-center study including a consecutive series of 10 patients who underwent the modified McLaughlin procedure for the treatment of chronic LPDS. The time between dislocation and treatment ranged from 6 weeks to 14 months (mean, 20.9 weeks). Postoperative imaging and functional evaluation were performed with a minimum of 2 years' follow-up (range, 24-110 months). Functional outcomes were assessed by means of a visual analog scale score for pain and patient satisfaction regarding the operation, the Constant-Murley score, and the University of California, Los Angeles shoulder rating scale.

RESULTS

The mean follow-up period was 59.4 months (range, 24-110 months). Range of motion improved significantly after surgery: Mean forward flexion improved from 71° ± 5° to 126°± 37° (P < .001), mean external rotation improved from 7°± 7° to 52° ± 18° (P = .012), and mean internal rotation improved from gluteal region ± 1 vertebral level to L1 ± 4 vertebral levels (P = .001). Functional outcome measures demonstrated significant improvements: The mean Constant-Murley score improved from 22 ± 2.4 (range, 20-26) to 65 ± 21.5 (P < .001); the mean University of California, Los Angeles score improved from 9.8 ± 1.3 (range, 8-12) to 27 ± 9.7 (P < .001); and the mean visual analog scale score improved from 4.6 ± 0.8 (range, 3-6) to 2.4 ± 2.3 (P < .001). Of the patients, 8 (80%) were satisfied with the procedure. The 2 remaining cases had a delay from injury to diagnosis > 6 months and evolved with poor functional outcomes and severe glenohumeral degenerative joint disease. There were no cases of recurrent dislocation, infection, or neurologic injury during the follow-up.

CONCLUSION

Our study findings demonstrated that the modified McLaughlin procedure showed good results over a 2-year minimum follow-up period. The clinical outcomes of this procedure are worse when there is a delay from injury to diagnosis > 6 months.

The Cartilage Wear Index: A new evaluation method to improve patient selection in surgical treatment of recurrent posterior glenohumeral instability

Background

The purpose of this study was to validate glenoid cartilage lesions as a negative prognostic factor and to define a new image-based preoperative evaluation method to identify surgical candidates for arthroscopic labral refixation with suture anchors in posterior shoulder instability.

Methods

Twenty-six patients who underwent arthroscopic posterior labral repair for shoulder instability were evaluated. Only patients with structural dynamic posterior instability were included. We evaluated on preoperative magnetic resonance arthrogram: glenoid version, humeral head subluxation, type of capsular insertion, and the cartilage lesions using the new Cartilage Wear Index (CWI). Two subgroups were analyzed with regard to the preoperative CWI and shoulder outcome scores: Single Assessment Numerical Evaluation (SANE) and Western Ontario Shoulder Instability Index (WOSI).

Results

The median age at operation was 28 (interquartile range = 21-33) years. Median overall postoperative outcome assessment demonstrated a SANE of 90 and a WOSI of 385. The median CWI was 1.02. Subgroup analysis revealed worse median WOSI and SANE scores in patients with a CWI >1.02 and a strong correlation between a high preoperative CWI and a higher postoperative WOSI score (R = 0.58; P = .038).

Conclusion

The CWI can be useful to identify patients who might obtain better outcomes when treated with arthroscopic labral repair in posterior shoulder instability.

Joint Preserving Treatment of Chronic Locked Posterior Shoulder Dislocation by Means of Combined Humeral Allograft Reconstruction and Posterior Glenoid Autograft Augmentation

Chronic locked posterior shoulder dislocations are challenging to treat and often warrant total shoulder arthroplasty. While joint preserving treatment is preferable in young patients, surgical techniques to treat this pathology have rarely been described in the literature. This technical note presents the treatment of a 30-year-old male patient with a chronic locked posterior shoulder dislocation by means of combined humeral allograft reconstruction and posterior glenoid autograft augmentation. Restoration of the spheric humeral head surface was obtained using a fresh-frozen femoral allograft fixed with two reabsorbable screws. Due to the intraoperatively persistent posterior instability after humeral reconstruction, the posterior glenoid was augmented with a tricortical iliac crest autograft, which was fixed with two metal screws. This treatment strategy resulted in a full range of motion and a centered stable shoulder joint at one-year follow-up. Therefore, the procedure of segmental reconstruction of the humeral head with a fresh-frozen allograft combined with a posterior glenoid augmentation with an iliac crest bone autograft is a joint-preserving treatment alternative to shoulder arthroplasty in young patients when humeral head reconstruction alone does not suffice.

Traumatische posteriore Luxation als seltene Ursache einer multidirektionalen Schulterinstabilität im Profisport

Die multidirektionale Instabilität der Schulter als Folge einer traumatischen posterioren Luxation ist selten und in der Literatur nur unzureichend beschrieben. Hier präsentiert wird der Fall eines 28-jährigen Anschiebers aus dem deutschen Bob-Olympia-Kader, der eine weichteilige multidirektionale Instabilität in Folge einer traumatischen posterioren Luxation beim Mountainbiken erlitt. Die Stabilisierung des Schultergelenks erfolgte arthroskopisch mittels kombinierter anteriorer und posteriorer Labrumrefixation.

Glenoid vault and humeral head alignment in relation to the scapular blade axis in young patients with pre-osteoarthritic static posterior subluxation of the humeral head

BACKGROUND

Static posterior subluxation of the humeral head is a pre-osteoarthritic deformity preceding posterior erosion in young patients. Its etiology remains unknown. The aim of this study was to analyze the differences in scapular morphology between young patients with pre-osteoarthritic static posterior subluxation of the humeral head and healthy controls with a centered humeral head.

METHODS

We performed a retrospective analysis of all patients with pre-osteoarthritic static posterior subluxation of the humeral head who were treated in our institution between January 2018 and November 2019. Fourteen shoulders in 12 patients were included in this study and then matched according their age, sex, and affected side with controls. Computed tomography images of both groups were compared in the standardized axial imaging plane for differences in scapular morphology. The following parameters were measured: glenoid version relative to the Friedman line and scapular blade axis, scapulohumeral and glenohumeral subluxation index, and neck angle, as well as glenoid and humeral offset.

RESULTS

The patients in the subluxation group showed significantly higher scapulohumeral and glenohumeral subluxation indexes than controls (0.76 vs. 0.55 [P < .0001] and 0.58 vs. 0.51 [P = .016], respectively). The mean measurements of glenoid version according to the Friedman line and relative to the scapular blade axis were significantly higher in the subluxation group than in controls (19° vs. 4° [P < .0001]and 14° vs. 2° [P = .0002], respectively). The glenoid vault was significantly more anteriorly positioned with respect to the scapular blade axis in the subluxation group than in controls (neck angle, 166° vs. 173° [P = .0003]; glenoid offset, 9.2 mm vs. 4.6 mm [P = .0005]). The midpoint of the humeral head showed a posterior offset with respect to the scapular blade axis in the subluxation group, whereas controls had an anteriorly placed midpoint of the humeral head (-2 mm vs. 3.1 mm, P = .01). A higher scapulohumeral subluxation index showed significant correlations with an increased anterior offset of the glenoid vault (increased glenoid offset: r = 0.493, P = .008 and decreased neck angle: r = -0.554, P = .002), a posterior humeral offset (r = -0.775, P < .0001), and excessive glenoid retroversion measured by both methods (Friedman line: r = 0.852, P < .0001; scapular blade axis: r = 0.803, P < .0001). A higher glenohumeral subluxation index also correlated significantly with an increased anterior offset of the glenoid vault (increased glenoid offset: r = 0.403, P = .034; decreased neck angle: r = -0.406, P = .032) and posterior humeral offset (r = -0.502, P = .006).

CONCLUSION

Young patients with pre-osteoarthritic static posterior subluxation of the humeral head have significant constitutional differences in scapular morphology in terms of an increased anterior glenoid offset, excessive glenoid retroversion, and increased posterior humeral offset in relation to the scapular blade compared with healthy matched controls.

Arthroscopic Knotless Subscapularis Bridge Technique for Reverse Hill-Sachs Lesion With Posterior Shoulder Instability

Posterior shoulder dislocations are an uncommon cause of glenohumeral instability; they are frequently missed and are associated with humeral head defects and capsulolabral lesions. Despite surgical treatment often being mandatory, there is still no standardized treatment for anterior impaction fractures of the humeral head (reverse Hill-Sachs lesions). Arthroscopic surgery is typically indicated, with a tendency toward resorting to knotless techniques in recent years. We present a method for the treatment of posterior shoulder dislocations with engaging reverse Hill-Sachs lesions that achieves full defect coverage using an arthroscopic all-in-the-box knotless subscapularis bridge technique with 2 anchors-with one crossing the subscapularis tendon and the other embracing it-along with posterior capsulolabral complex restoration. This promising technique is a potentially superior alternative for the treatment of these lesions that can also be used in the presence of concomitant partial subscapularis tears.

Arthroscopic "Bone Block Cerclage" Technique for Posterior Shoulder Instability

Many open and arthroscopic techniques have been described to treat posterior glenohumeral instability. Multifactorial features of posterior shoulder instability pathoanatomy and varied patient characteristics have challenged the understanding of this condition and have led to dissimilar results, without a strong consensus for the most adequate technique to treat it. We describe an arthroscopic anatomical metal-free posterior glenoid reconstruction technique, using a tricortical iliac crest allograft with 2 ultra-high strength sutures (FiberTape Cerclage System; Arthrex, Naples, FL) with concomitant posterior capsulolabral complex reconstruction procedure.

Shoulder-Pacemaker Treatment Concept for Posterior Positional Functional Shoulder Instability: A Prospective Clinical Trial

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.

Characteristics of functional shoulder instability

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 = .002, Rowe Score: P = .001, Subjective Shoulder Value: P = .001) and regarding functional impairment (shoulder stability: P < .001, daily activities: P = .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.

An anatomic study on the origin of the long head of the triceps brachii

Background

Posterior shoulder instability was reported to be more common than had been previously reported. However, the detailed morphology of the origin of the long head of the triceps brachii (LHT), which is located at the posteroinferior part of the glenohumeral joint and associated with the stability of the head of the humerus, has been unknown. The purpose of the current study was to clarify the detailed morphology of the origin of the LHT.

Methods

A total of 64 specimens from 36 cadavers (11 males and 25 females) were used. After dissecting the origin of the LHT in 54 specimens of 27 cadavers, the width of the origin of the LHT was measured with a caliper by 2 observers. The origin of the LHT was also investigated histologically in 18 specimens. Sections were analyzed with Masson’s trichrome staining and Safranin O staining.

Results

Some fibers of the LHT originated more from the cranial area than from the infraglenoid tubercle and descended along the posterior rim of the glenoid cavity. The width of the origin on the dorsal surface of the scapula was 31.2 mm. The origin from the bone had a developed uncalcified fibrocartilage histologically. In addition, the LHT was fused with the glenohumeral joint capsule and was attached to the glenoid labrum directly.

Conclusions

The LHT could affect the glenohumeral joint capsule or the glenoid labrum because of their connections to each other and be associated with the posterior shoulder instability indirectly.

Epidemiology of the Frequency, Etiology, Direction, and Severity (FEDS) system for classifying glenohumeral instability

HYPOTHESIS

The purpose of this multicenter epidemiologic study was to determine the distribution of patients within the Frequency, Etiology, Direction, and Severity (FEDS) classification system to determine which categories are of clinical importance.

METHODS

Shoulder instability patients were identified using International Classification of Diseases, Ninth Revision coding data from 3 separate institutions from 2005-2010. Data were collected retrospectively. Details of instability were recorded in accordance with the FEDS classification system. Each patient was assigned a classification within the FEDS system. After all patients were assigned to a group, each group was individually analyzed and compared with the other groups.

RESULTS

There are a total of 36 possible combinations within the FEDS system. Only 16 categories were represented by at least 1% of our patient population. Six categories captured at least 5% of all patients with shoulder instability. Only 2 categories represented greater than 10% of the population: solitary, traumatic, anterior dislocation, with 95 patients (24.8%), and occasional, traumatic, anterior dislocation, with 63 patients (16.4%).

CONCLUSIONS

There are 16 categories within the FEDS classification that are clinically significant. Solitary, traumatic, anterior dislocation and occasional, traumatic, anterior dislocation were the most frequently observed in our cohort.

Anterior shoulder dislocation and concomitant fracture of the greater tuberosity: Clinical and radiological results

Background

Recurrence rates after primary traumatic shoulder dislocation are distinctly high. We hypothesized that concomitant isolated fractures of the greater tuberosity are associated with low rates of persistent instability but decreased range of motion.

Methods

Between 2007 and 2013, 66 consecutive shoulders in 64 patients were treated for primary shoulder dislocation combined with an isolated fracture of the greater tuberosity with either a nonsurgical (48 shoulders, 72.7%) or surgical (18 shoulders, 27.3%) treatment approach. In all, 55 cases (83.3%) were available for clinical follow-up examination after an average of 59.0 ± 20.7 months (range: 25–96 months) and of these, 48 (72.7%) patients consented to radiological evaluation to determine healing and position of the greater tuberosity.

Results

The mean range of motion of the affected shoulder was significantly decreased by 9° of elevation (p = 0.016), 11° of abduction (p = 0.048), 9° of external rotation in 0° of abduction (p = 0.005), and 10° of external rotation in 90° of abduction (p = 0.001), compared with the unaffected shoulder. The mean WOSI score was 373 ± 486 points, the mean Constant and Murley score was 75.1 ± 19.4 points, and the mean Rowe score was 83 ± 20 points. Three cases (5.5%) of re-dislocation were reported among the cohort, all of them were due to a relevant trauma. Radiological evaluation revealed anatomically healed fragments in 31 shoulders (65%), dislocation of the fragment in ten shoulders (21%), impaction into the humeral head in four shoulders (8%), and absorption in three shoulders (6%).

Conclusion

A concomitant isolated fracture of the greater tuberosity leads to low recurrence rates along with a significant decrease in range of motion after primary traumatic anterior shoulder dislocation.

[The ABC guide for the treatment of posterior shoulder instability]

BACKGROUND

Posterior glenohumeral instability (PGHI) is an often unrecognized or misdiagnosed type of shoulder instability due to its heterogenic clinical and radiological presentation.

CLASSIFICATION

The ABC classification for PGHI is based on the different pathomechanisms and recommended treatment standards and is therefore a guide to finding the correct diagnosis and therapy for affected patients. There are different types of PGHI: A (first time), B (dynamic), C (static). These groups are further classified based on pathomechanical principles: A1: subluxation, A2: dislocation; B1: functional, B2: structural; C1: constitutional, C2: acquired.

THERAPY

In patients with type 1 PGHI (A1, B1, C1) conservative treatment is recommended while in patients with type 2 PGHI (A2, B2, C2) surgical treatment can be considered based on structural defects, clinical symptoms, chronicity, age, functional demand, and patient-specific health status. In addition it has to be considered, that there is the possibility of coexisting or overlapping subtypes as well as the chance of progression from one category into another over time.

[Diagnostics and treatment of posterior shoulder instability]

Posterior shoulder instability has a markedly lower incidence than anterior shoulder instability. It has a wide spectrum of clinical symptom manifestations and the overwhelming number of patients lack a traumatic primary dislocation. In addition to a detailed medical history, a specific clinical examination with the help of standardized provocation tests is essential for the diagnostics. For the detection of structural posterior capsule and labral lesions in cases of chronic courses, magnetic resonance imaging (MRI) should be used with an intra-articular contrast agent. Relevant bony defects of the humeral head (reverse Sachs-Hill lesion) are frequent, whereas critical posterior defects of glenoid cavity are relatively rare. Both lesions should be quantified using 3D computed tomography. The choice of therapeutic procedure should be based on the underlying pathology of the defect. Conservative therapy is useful in patients with scapular dyskinesis, voluntary dislocation and pathological muscle patterning. In isolated soft tissue pathologies, arthroscopic labrum fixation and capsule plication are the standard treatment. In the case of insufficient soft tissue relations or critical posterior glenoid defects, bony stabilization of the glenoid using an iliac crest bone graft is the recommended therapy.

Use of shoulder pacemaker for treatment of functional shoulder instability: Proof of concept

Background

Functional 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.

Objectives

The 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 methods

Three 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.

Results

No 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.

Conclusion

The 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 online

The 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