Posterior instability of the shoulder: diagnosis and management

Current Concepts in Assessment and Management of Failed Posterior Labral Repair

Recurrent posterior shoulder instability after primary repair is uncommon, but presents a challenging clinical scenario. Most revisions in failed labral repair were associated with glenoid bone morphology related to critical bone loss, retroversion, or dysplasia. A variety of treatment options exist which include revision labral repair with or without capsular plication, glenoid osteotomy, humeral rotational osteotomy, or glenoid bone augmentation. No single technique has been shown to be superior and each technique has strengths and limitations. Therefore, thoughtful evaluation and planning is critical to address each patient's individual pathology to maximize success after revision surgery.

Current Imaging of Anterior and Posterior Instability in the Athlete

In the evaluation of shoulder instability, recognition of relevant pathology on imaging is critical to planning a surgical treatment that minimizes the risk for recurrent instability. The purpose of this review is to (1) discuss the use of radiography, computed tomography, and MRI in evaluating shoulder instability and (2) demonstrate how various imaging modalities are useful in identifying critical pathologies in the shoulder that are relevant for treatment.

Magnetic resonance arthrography with positional manoeuvre for the diagnosis of synovial fold of posterior shoulder joint capsule

OBJECTIVES

The objective of this study is to prospectively assess the effectiveness of shoulder magnetic resonance (MR) arthrograms with positional manoeuvres in detecting posterior synovial folds.

METHODS

Two radiologists independently assessed all axial MR arthrograms in internal rotation, neutral position, and external rotation for the presence of a posterior synovial fold. The diagnostic performances of the MR arthrograms were then compared, with results validated through arthroscopy.

RESULTS

Arthroscopy was performed on 81 of the 150 patients included in the study. A posterior synovial fold was identified arthroscopically in eleven of these patients. Measurements of the posterior synovial fold obtained in external rotation and the neutral position of the arm showed a significant correlation with arthroscopic results (p < 0.05). For detecting the posterior synovial fold with arthroscopic correlation, the sensitivity and specificity values for observer 1 and observer 2 were 100-81.4% and 100-88.6%, respectively, for MR arthrograms in the neutral position; 100-52.9% and 100-62.9% for MR arthrograms in external rotation; and 100-95.7% and 81.8-98.6% for MR arthrograms in internal rotation. There was a fair agreement for MR arthrography in external rotation for detecting posterior synovial folds, while MR arthrograms in internal rotation and neutral position showed near-perfect and significant interobserver agreement.

CONCLUSION

The rotational positions of the humeral neck during MR arthrographic examination can influence the diagnostic specificity and sensitivity of axial MR arthrograms in detecting the posterior synovial fold.

CLINICAL RELEVANCE STATEMENT

The posterior synovial fold can mimic a posterior labral detachment. Therefore, its correct identification is crucial in order to avoid unnecessary surgical procedures.

KEY POINTS

Movement of the shoulder may introduce variability in MR arthrography appearance. Rotation of the humeral neck during MR arthrography can affect diagnoses in posterior synovial fold detection. Given that posterior synovial folds can imitate posterior labral detachment, their correct identification is crucial to avoid unnecessary surgical procedures.

Location of Shoulder Glenoid Labral Tears: A Study of 1763 Consecutive Patients

BACKGROUND

Anterior shoulder labral tearing has historically been considered the most common location of shoulder labral pathology. Recently, smaller studies have reported that posterior labral involvement may be more common than previously recognized.

PURPOSE

To examine the location of surgically repaired labral tears by a single surgeon over a consecutive 23-year period.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A total of 1763 consecutive patients who underwent arthroscopic or open shoulder labral repair by a single seniorsports medicine fellowship-trained orthopaedic surgeon between April 2000 and April 2023 were retrospectively reviewed. Current Procedural Terminology codes were used to identify patients, which included 29806, 29807, 29822, and 29823. Exclusion criteria included isolated shoulder manipulation or glenohumeral joint or labral debridement that did not include repair. Intraoperative glenoid labral tears observed were categorized into 7 broad categories: (1) anterior labral tears, (2) posterior labral tears, (3) superior labral anterior posterior (SLAP) type II tears (A, B, or C), (4) SLAP type V tears, (5) SLAP type VIII tears, or (6) circumferential labral tears (combined SLAP, anterior, and posterior labral tear). Shoulders diagnosed with multiple tear patterns (ie, anterior and posterior) were also noted.

RESULTS

During the 23-year period, 1763 patients underwent arthroscopic or open labral repair; they included 1295 male and 468 female patients, ranging in age from 12 to 70 years, with a mean age of 23.2 years and median age of 19 years. Overall, 28.4% of tears involved the anterior labrum, 64.9% involved the posterior labrum, and 59.6% involved the superior labrum. Regarding isolated tears, 9.3% were isolated anterior labral tears, 19.7% were isolated posterior labral tears, 11.5% involved the anterior and posterior labrum, 22.2% were isolated superior (SLAP type II-IV) tears, 3.63% were isolated SLAP type V tears, 29.8% were isolated SLAP type VIII tears, and 4.1% were circumferential tears.

CONCLUSION

Posterior shoulder labral tearing was more common than anterior tearing in a large consecutive series of 1763 patients who underwent surgical repair. This highlights the importance of posterior labral pathology, which sometimes may be overlooked because of more vague complaints, with pain and loss of function being the most common.

Editorial Commentary: A Delphi Expert Consensus Provides Clarity on Diagnosis, Treatment, Rehabilitation, and Return-to-Sports for Posterior Shoulder Instability

Posterior shoulder instability (PSI) is an uncommon condition, accounting for 2% to 12% of shoulder instability cases. However, PSI might be more common and possibly accounts for up to 24% of all young, active patients treated for shoulder instability. The etiology of PSI is complex and multifactorial, making accurate diagnosis, classification, and treatment challenging. The accurate diagnosis of PSI is problematic and varies with symptoms ranging from pain, decreased strength, or endurance to mechanical symptoms such as clicking or popping, and only a minority of patients present after a posterior shoulder dislocation. Appropriate imaging is necessary and should include radiographs and advanced imaging with magnetic resonance imaging, preferably magnetic resonance arthrography. The goal of treatment is to reduce pain, improve function, and prevent or reduce recurrence. Both surgical and conservative treatments are demanding, and both osseous and soft-tissue pathologies need to be addressed adequately. Typically, a conservative approach should be considered first for the first 6 months, with a focus on proprioceptive exercises, strengthening of the dynamic stabilizers, and improving scapulothoracic mechanics. The primary indication for surgery is recurrent symptoms. Controversies exist regarding the choice between open and arthroscopic stabilization of soft-tissue defects, the treatment of the McLaughlin lesion, and the management of osseous defects.

Outcomes of arthroscopic stabilization for posterior shoulder instability: a systematic review

BACKGROUND

Posterior shoulder instability makes up approximately 10% of all shoulder instability cases and its diagnosis and treatment is less well understood. Recently, however, there has been increased recognition of posterior instability and posterior stabilization. The purpose of this study was to systematically review the literature to ascertain the outcomes on arthroscopic stabilization of posterior shoulder instability.

METHODS

Two independent reviewers conducted a systematic literature search based on PRISMA guidelines, utilizing the MEDLINE database. Studies were eligible for inclusion if they reported postoperative outcomes for posterior shoulder instability following arthroscopic stabilization.

RESULTS

A total of 48 studies met inclusion criteria for review including 2307 shoulders. Majority of patients were male (83.3%), with an average age of 26.1 years and a mean follow-up of 46.8 months. The functional outcome score primarily utilized for postoperative assessment was the American Shoulder and Elbow Surgeons with an average of 84.77. Overall, 90.9% of patients reported being satisfied with their arthroscopic stabilization. Recurrent instability occurred in 7.4% of patients. The total revision rate was 5.2%. 16.6% of patients reported residual pain postoperatively. The rate of return to play was 86.4% with 68.0% of patients returning to play at the same or higher level of play.

CONCLUSION

Arthroscopic stabilization of posterior shoulder instability resulted in good outcomes with high patient satisfaction and low rates of recurrent instability, revisions, and residual pain.

The Kouvalchouk procedure vs. distal tibial allograft for treatment of posterior shoulder instability: the deltoid "hammock" effect exists

BACKGROUND

In 1993, Kouvalchouk described an acromial bone block with a pedicled deltoid flap for the treatment of posterior shoulder instability. This procedure provides a "double blocking" effect in that the acromial autograft restores posterior glenoid bone loss and the deltoid flap functions as a muscular "hammock" resembling the sling effect of the conjoint in the Latarjet procedure. The primary aim of this study was to compare the Kouvalchouk procedure to distal tibial allograft (DTA) reconstruction for the management of posterior shoulder instability with associated bone loss, while the secondary aim was to evaluate the deltoid hammock effect.

METHODS

Ten upper extremity cadavers were evaluated using a validated shoulder testing apparatus in 0° and 60° of glenohumeral abduction in the scapular plane. Testing was first performed on the normal shoulder state and was followed by the creation of a 20% posterior glenoid defect. Subsequently, the Kouvalchouk and DTA procedures were conducted. Forces of 0N, 5N, 10N, and 15N were applied to the posterior deltoid tendinous insertion on the Kouvalchouk graft along the physiological muscle line-of-action to evaluate the 'hammock" effect of this procedure. Testing was additionally performed on the Kouvalchouk bone graft with the deltoid muscle sectioned from its bony attachment. For all test states, a posteriorly directed force was applied to the humeral head perpendicular to the direction of the glenoid bone defect, with the associated translation quantified using an optical tracking system. The outcome variable was posterior translation of the humeral head at an applied force magnitude of 30N.

RESULTS

The Kouvalchouk procedure with the loaded deltoid flap (10N: P = .039 and 15N: P < .001) was significantly better at reducing posterior humeral head translation than the DTA. Overall, increased glenohumeral stability was observed with increased force applied to the posterior deltoid flap in the Kouvalchouk procedure. The 15 N Kouvalchouk was most effective at preventing posterior humeral translation, and the difference was statistically significant compared with the 20% glenoid defect (P = .003), detached Kouvalchouk (P < .001), and 0N Kouvalchouk (P < .001). The 15 N Kouvalchouk procedure restored posterior shoulder joint stability to near normal levels, such that it was not significantly different from the intact state (P = .203).

CONCLUSIONS

The Kouvalchouk procedure with load applied to the deltoid was found to be biomechanically superior to the DTA for the management of posterior shoulder instability with associated bone loss. Additionally, the results confirmed the presence and effectiveness of the deltoid "hammock" effect.

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.

Radiographic and Advanced Imaging Evaluation of Posterior Shoulder Instability

PURPOSE OF REVIEW

Posterior shoulder instability is an uncommon but important cause of shoulder dysfunction and pain which may occur as the result of seizure, high energy trauma, or repetitive stress related to occupational or sport-specific activities. This current review details the imaging approach to the patient with posterior shoulder instability and describes commonly associated soft tissue and bony pathologies identified by radiographs, CT, and MR imaging.

RECENT FINDINGS

Advances in MR imaging technology and techniques allow for more accurate evaluation of bone and soft tissue pathology associated with posterior shoulder instability while sparing patients exposure to radiation. Imaging can contribute significantly to the clinical management of patients with posterior shoulder instability by demonstrating the extent of associated injuries and identifying predisposing anatomic conditions. Radiologic evaluation should be guided by clinical history and physical examination, beginning with radiographs followed by CT and/or MRI for assessment of osseous and soft tissue pathology. Synthesis of a patient's clinical history, physical exam findings, and radiologic examinations should guide clinical management.

Two-Portal Arthroscopic Knotless All-Suture Anchor Posterior Labral Repair

Isolated posterior shoulder instability accounts for approximately 10% of shoulder instability cases. Patients may present after an acute trauma or with insidious onset and associated posterior shoulder pain. Knotless and all-suture anchor devices have become increasing popular and are often used in arthroscopic shoulder instability cases to avoid knot stacks and allow for the ability to re-tension the fixation. This technical note describes our technique for 2-portal posterior labral repair using knotless all-suture anchors with the patient in the lateral decubitus position.

Location and size of the reverse Hill-Sachs lesion in patients with traumatic posterior shoulder instability

BACKGROUND

In patients with traumatic posterior shoulder instability, little is known about the precise location and size of the reverse Hill-Sachs lesion.

METHODS

Forty-nine shoulders of 47 patients with traumatic posterior instability were included in this study based on the following inclusion criteria: (1) a primary or recurrent traumatic posterior shoulder dislocation and (2) the initial event being caused by trauma. Patients were excluded if they had (1) no history of trauma, (2) prior shoulder surgery, (3) no computed tomographic (CT) examination, or (4) were seizure cases. Three-dimensional images of the humerus reconstructed from CT images were reviewed using an image analysis software. The location and size of the reverse Hill-Sachs lesion were measured and described on a clock face on the humeral head.

RESULTS

The reverse Hill-Sachs lesion was observed in 25 of 49 shoulders (51%). The reverse Hill-Sachs lesions were located between 1:37 and 2:48. The depth of the reverse Hill-Sachs lesion (mean ± standard deviation) was 5.8 ± 2.2 mm. The extent of the reverse Hill-Sachs lesion was 35° ± 12°. The average orientation of the reverse Hill-Sachs lesion, represented by an angle measured from the 12 o'clock position, was 64° ± 12° and pointing toward 2:09 on a clock face. The mean length and width of reverse Hill-Sachs lesions were 9.7 ± 4.7 mm and 11.1 ± 3.6 mm, respectively.

CONCLUSION

The reverse Hill-Sachs lesion was a semicircular compression fracture located on the anteromedial aspect of the humeral head. Compared with shoulders with anterior shoulder instability, the humeral defect was smaller and located more inferiorly in shoulders with posterior instability.

The Perfect-Circle Technique Demonstrates Poor Inter-Rater Reliability in Measuring Posterior Glenoid Bone Loss on Magnetic Resonance Imaging

Purpose

To evaluate the reliability of the "perfect-circle" methodology for measurement of glenoid bone loss with magnetic resonance imaging (MRI) in patients with posterior glenohumeral instability.

Methods

A prospective chart review was performed on patients who underwent isolated arthroscopic posterior labral repairs in our institution's electronic medical records between January 1, 2021, and June 30, 2021. Inclusion criteria included isolated posterior shoulder instability with posterior labral repair and corroborated tears on MRI. A total of 9 raters, either sports or shoulder and elbow fellowship-trained orthopaedic surgeons, each evaluated the affected shoulder MRI scans twice, at over 2 weeks apart. Measurements followed the "perfect-circle" technique and included projected anterior-to-posterior (AP) glenoid diameter, amount of posterior bone loss, and percentage of posterior bone loss.

Results

Ten consecutive patients between the ages of 17 and 46 years with diagnosed posterior glenohumeral instability were selected. The average age was 28 ± 10 years, and 60% of patients were male. The patient's dominant arm was affected in 40%, and 50% of cases involved the right shoulder. The average glenoid diameter was 29.62 ± 3.69 mm, and the average measured bone loss was 2.8 ± 1.74 mm. The average percent posterior glenoid bone loss was 9.41 ± 5.78%. The inter-rater reliability was poor for the AP diameter and for the posterior glenoid bone loss with intraclass correlation coefficients at 0.30 (0.12-0.62) and 0.22 (0.07-0.54) respectively. The intrarater reliability was poor for AP diameter and moderate for posterior glenoid bone loss, with intraclass correlation coefficients at 0.41 (0.22-0.57) and 0.50 (0.33-0.64), respectively.

Conclusions

Using the "perfect-circle" technique for evaluating posterior glenohumeral bone loss has poor-to-moderate inter- and intrarater reliability from MRI.

Level of Evidence

Level IV, prospective diagnostic study.

Posterior Shoulder Instability and Glenoid Bone Loss: A Review and a Free Bone Graft Technique

Posterior glenoid bone loss (pGBL) is frequently associated with posterior shoulder instability. Posterior glenohumeral instability accounts for a small percentage of shoulder pathologies, and critical bone loss in posterior instability has not been well defined in the literature. Younger patient populations who participate in activities that repetitively stress the posterior stabilizing structures of the shoulder are more prone to developing posterior shoulder instability. A variety of surgical options have been described, ranging from isolated capsulolabral repair to glenoid osteotomy. Soft-tissue repair alone may be an inadequate treatment in cases of pGBL and places patients at a high risk of recurrence. Our preferred technique for posterior glenoid reconstruction in cases of pGBL involves the transfer of a free iliac crest bone graft onto the native glenoid. The graft is contoured to fit the osseous defect and secured to provide an extension of the glenoid track. In this study, we review pGBL in the setting of posterior instability and describe our technique in detail. Further long-term studies are needed to refine the indications for glenoid bone graft procedures and quantify what constitutes a critical pGBL.

Does glenoid version affect the post-operative clinical outcome after repair of posterior labral tear: A retrospective study

Introduction

Posterior shoulder instability and consequent labral tear have been predominantly associated with retroversion of the bony glenoid and chondrolabral version. However, literature concerning the degree of glenoid and chondrolabral version and clinical outcomes following labral repair is scarce.

Methods

A retrospective cohort study was undertaken among patients with posterior shoulder instability who had undergone arthroscopic isolated posterior labral repair. The MRI was used to assess the bony and labral variations of the glenoid using the Friedman method and further categorized as either anteverted or retroverted glenoid. American Shoulder and Elbow Surgeons (ASES), Oxford Shoulder Score (OSS), and Single Assessment Numeric Evaluation (SANE) scores were used to evaluate pre- and postoperative clinical outcomes at a minimum follow-up of one year.

Results

33 shoulder MRIs performed at our institution were available for radiographic analysis. Among the 33 shoulders that underwent posterior shoulder capsulolabral repair, 23 were available for clinical follow-up for at least one year (range, 12-108 months). The mean (±SD) labral version and bony version were -3.98 (±5.68) and -2.83 (±5.20), respectively. The mean (±SD) postoperative ASES, Oxford score, and SANE scores for all participants were 84.04 (±14.14), 43.38 (±3.81), and 78.57 (±17.40), respectively. However, the difference in clinical outcomes in patients with anteverted or retroverted glenoid versions was not statistically significant.

Conclusion

Our study concludes a strong correlation between posterior glenohumeral instability and higher degree of glenoid retroversion. Nevertheless, variations in the glenoid version appear to have no significant impact on clinical outcomes.

Level of study

Level IV, retrospective cohort.

No Difference in Recurrent Instability Between Knotted and Knotless Repair Techniques in Arthroscopic Treatment of Isolated Posterior Labral Tears: A Systematic Review

Purpose

To compare clinical failure, recurrent instability, patient-reported outcome measures (PROMs), and return to sport (RTS) between knotted and knotless fixation methods in arthroscopic posterior labral repair for isolated posterior shoulder instability (PSI).

Methods

Multiple databases were queried according to Preferred Reported Items for Systematic Reviews and Meta-Analyses guidelines for clinical studies with Level I to IV evidence, including knotted and knotless suture anchors for arthroscopic posterior labral repair. Combined anterior and posterior instability, multidirectional instability, SLAP injuries, unspecified repair techniques, majority open procedures, and revision surgery were excluded.

Results

Screening yielded 17 full-text articles reporting on 852 shoulders undergoing posterior labral repair. Recurrent instability ranged from 0% to 21%, and the rate of revision surgery ranged from 0% to 11% in knotted only, 0% in knotless only, and 2.0% to 8.1% in knotted and knotless studies. Six studies with both pre- and postoperative visual analog scale scores and 7 studies with both pre- and postoperative American Shoulder and Elbow Score scores all showed improvement in scores after intervention regardless of repair technique. Thirteen studies reported RTS or duty rates with a minimum of 79%.

Conclusions

Overall recurrent instability after posterior labral repair for isolated PSI was low with improvement in PROMs and favorable RTS rates regardless of fixation method. There was no clear difference in recurrent instability or revision surgery between knotted and knotless fixation methods for isolated posterior labral repair. However, the current literature is predominantly limited by Level III and IV evidence. The quality of literature and lack of standardization on the definition of clinical failure and recurrent instability among surgeons preclude any definitive conclusion regarding one clinically superior fixation method.

Level of Evidence

Level IV, systematic review of Level III and IV studies.

Diagnosing the direction of shoulder instability in rugby players

The muscular characteristics of rugby players may make diagnosing the direction of shoulder instability and labral pathology challenging. This study aimed to assess the accuracy of clinical examination and specifically instability tests, in diagnosing the direction of shoulder instability in rugby players. One-hundred-and-forty rugby players, who had undergone a shoulder stabilization procedure, over a 55-month period, were included in this study. The mean age was 21.5 years with 137 males. Data collected included clinical examination and intraoperative findings. The two were compared to calculate the diagnostic accuracy of special tests for instability. The Anterior Apprehension Test had good sensitivity (82.7%), specificity (100%) and PPV (100%) but poor NPV (55.8%). All posterior instability tests demonstrated a sensitivity of over 85%, but all had a specificity of 25% or less. In 83.6% of cases the direction of instability was correctly identified from history and examination. Anterior instability was correctly diagnosed in 78.9% of cases and posterior in 100.0%. The poor NPV of the anterior apprehension test suggests that clinicians should be suspicious of anterior instability in rugby shoulders even in the light of negative examination findings. Positive posterior instability tests are highly suggestive of posterior instability in rugby players.

Occult, Incomplete, and Complete Posterior Labral Tears Without Glenohumeral Instability on Imaging Underestimate Labral Detachment

PURPOSE

To introduce a classification of posterior labral tear and describe clinical characteristics, magnetic resonance imaging (MRI)/magnetic resonance arthrography (MRA) findings, arthroscopic findings, and outcomes after arthroscopic repair for patients with posterior labral tears without glenohumeral instability.

METHODS

Sixty patients with posterior labral tear who underwent arthroscopic repair were analyzed retrospectively. Patients with shoulder instability were excluded. Tear patterns were classified into 3 types; occult (type 1), incomplete (type 2), and complete (type 3) based on MRI/MRA studies. A visual analog scale score for pain, American Shoulder and Elbow Surgeons score, Single Assessment Numeric Evaluation score for satisfaction, and return to sports were evaluated at a minimum follow-up of 2 years. Computed tomography arthrography was performed at a year follow-up for assess labral healing. The diagnosis was confirmed in arthroscopy, and arthroscopic labral repair without capsular plication was performed.

RESULTS

The mean patient age was 30.4 ± 6.9 years, and all patients were male. Forty-four patients (73.3%) were participating in sports. MRI/MRA studies identified 10 patients with type 1, 18 with type 2, and 32 with type 3 tears. Type 1 tear patients showed a significantly longer symptom duration than those with type 3 (32.5 ± 17.2 vs 18.2 ± 17.1 months; P = .015). In arthroscopic findings, 70% of type 1 tear was confirmed as incomplete or complete tears. The American Shoulder and Elbow Surgeons score improved from 79.6 ± 10.3 to 98.1 ± 3.7, and pain was relieved from 2.4 ± 0.7 to 0.2 ± 0.5 at the last follow-up visit with high labral healing rate (95%). Thirty-nine (88.6%) patients returned to sports at preinjury levels.

CONCLUSIONS

In active young men with shoulder pain during daily activities or sports despite programmed conservative treatment, posterior labral tears should be considered even when MRI/MRA findings are ambiguous. Arthroscopic posterior labral repair without capsular plication provided satisfactory clinical outcomes and a high labral healing rate.

LEVEL OF EVIDENCE

Level Ⅳ, case series.

Establishing the Minimal Clinically Important Difference, Substantial Clinical Benefit, and Patient Acceptable Symptomatic State After Arthroscopic Posterior Labral Repair for Posterior Glenohumeral Instability

BACKGROUND

Posterior glenohumeral instability is an increasingly recognized cause of shoulder pain and dysfunction among young, active populations. Outcomes after posterior stabilization procedures are commonly assessed using patient-reported outcome measures including the Single Assessment Numeric Evaluation (SANE), the Rowe instability score, the American Shoulder and Elbow Surgeons (ASES) score, and the visual analog scale (VAS) for pain. The clinical significance thresholds for these measures after arthroscopic posterior labral repair (aPLR), however, remain undefined.

PURPOSE

We aimed to define the minimal clinically important difference (MCID), substantial clinical benefit (SCB), and patient acceptable symptomatic state (PASS) for the SANE, Rowe score, and ASES score as well as the VAS pain after aPLR. Additionally, we sought to determine preoperative factors predictive of reaching, as well as failing to reach, clinical significance.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

This study was a retrospective analysis of patient-reported outcome scores collected from patients who underwent aPLR between January 2011 and December 2018. To determine the clinically significant threshold that corresponded to achieving a meaningful outcome, the MCID, SCB, and PASS were calculated for the SANE, Rowe score, ASES score, and VAS pain utilizing either an anchor- or distribution-based method. Additionally, univariate and multivariate logistic regression analyses were performed to determine the factors associated with achieving, or not achieving, the MCID, SCB, and PASS.

RESULTS

A total of 73 patients with a mean follow-up of 82.55 ± 24.20 months were available for final analysis. MCID, SCB, and PASS values for the VAS pain were 1.10, 6, and 3, respectively; for the ASES score were 7.8, 34, and 80, respectively; for the SANE were 10.15, 33, and 85, respectively; and for the Rowe score were 11.3, 60, and 90, respectively. To meet the MCID, male sex (odds ratio [OR], 1.1639; P = .0293) was found to be a positive predictor for the VAS pain, and a lower preoperative SANE score (OR, 0.9939; P = .0003) was found to be a negative predictor for the SANE. Dominant arm involvement was associated with lower odds of achieving the PASS for the ASES score (OR, 0.7834; P = .0259) and VAS pain (OR, 0.7887; P = .0436). Patients who reported a history of shoulder trauma were more likely to reach the PASS for the SANE (OR, 1.3501; P = .0089), Rowe score (OR, 1.3938; P = .0052), and VAS pain (OR, 1.3507; P = .0104) as well as the SCB for the ASES score (OR, 1.2642; P = .0469) and SANE (OR, 1.2554; P = .0444). A higher preoperative VAS pain score was associated with higher odds of achieving the SCB for both the VAS pain (OR, 1.1653; P = .0110) and Rowe score (OR, 1.1282; P = .0175). Lastly, concomitant biceps tenodesis was associated with greater odds of achieving the SCB for the ASES score (OR, 1.3490; P = .0130) and reaching the PASS for the SANE (OR, 1.3825; P = .0038) and Rowe score (OR, 1.4040; P = .0035).

CONCLUSION

To our knowledge, this study is the first to define the MCID, SCB, and PASS for the ASES score, Rowe score, SANE, and VAS pain in patients undergoing aPLR. Furthermore, we found that patients who reported a history of shoulder trauma and those who underwent concomitant biceps tenodesis demonstrated a greater likelihood of achieving clinical significance. Dominant arm involvement was associated with lower odds of achieving clinical significance.

Arthroscopic posterior capsulolabral repair grants adequate outcomes in shoulders with posterior instability without glenoid cartilage lesions

INTRODUCTION

Posterior capsulolabral repair (posterior Bankart) is effective to restore shoulder stability and relieve pain, though a recent meta-analysis reported recurrent instability in 9.5% of patients, and that only 62.7% were able to resume sports. The purpose of this study was to assess the outcomes of arthroscopic posterior capsulolabral repair in a population of unselected patients, in terms of recurrence of instability, clinical scores, and return to sports.

METHODS

The authors retrospectively studied a consecutive series of 22 patients that underwent posterior capsulolabral repair between 2009 and 2019. Patients were assessed before posterior capsulolabral repair and at a minimum follow-up of 24 months, in terms of subjective shoulder value (SSV), Western Ontario Shoulder Instability Index (WOSI), as well as level of sport. Following surgery, all complications, reoperations or episodes of instability were noted.

RESULTS

The cohort comprised 21 men (95%) and 1 woman (5%), aged 38.8 ± 12.5 years (range 17-61) at index surgery. Of the 20 patients that performed sports, only 2 (10%) stopped sports after surgery, while 18 resumed their main sport (90%). At a follow-up of 65.4 ± 34.8 months (range 25-146), the SSV was 85.1 ± 14.7, pain on VAS was 1.9 ± 2.1, and the Constant-Murley score was 71.6 ± 17.9. Five patients had subjective instability without dislocation (23%). Nine patients (41%) had no pain (0 points), 6 patients (27%) had mild pain (1-2 points), 4 patients (18%) had moderate pain (3 points), while 3 patients (14%) had severe pain (5-8 points).

CONCLUSION

Arthroscopic posterior capsulolabral repair prevented recurrent dislocation in patients with posterior shoulder instability at a minimum follow-up of 2 years, despite persistent pain in 32%, and subjective instability in 23%. These complications were mainly observed in patients with work-related accidents and glenoid cartilage lesions.

LEVEL OF EVIDENCE

III, case series.

Editorial Commentary: Patients May Have Posterior Glenoid Labral Tears in the Absence of Instability or Magnetic Resonance Imaging Findings

Posterior labral tears occur more often than imagined 25 years ago. Although such tears are generally identified in patients with posterior shoulder instability, the spectrum of labral tears in patients without instability creates a challenging diagnosis. Both physical examination and magnetic resonance imaging interpretation are difficult. Pathology encompassing posterior labral tears without instability notably reveals differences compared with throwers with posterior labral tears and patients with posterior instability. Recent research has identified 3 tear types: occult (type 1), incomplete (type 2), and complete (type 3). Attention to diagnosis deserves critical attention, in addition to tailoring of repair techniques to address the appropriate conditions in the shoulder. Even in patients without posterior instability and with ambiguous magnetic resonance imaging or magnetic resonance arthrography findings, posterior shoulder pain during daily activities or sports may indicate a posterior labral tear. Arthroscopic posterior labral repair without capsular plication provides good clinical outcomes and high rates of return to sport and labral healing.

Favorable short-term outcomes of micronized allogenic cartilage scaffold for glenoid cartilage defects associated with posterior glenohumeral instability

Purpose

To determine clinical outcomes associated with micronized allogenic cartilage scaffold use for treatment of posterior glenoid cartilage defects at 2 years.

Study Design

Case series.

Methods

A retrospective analysis of prospectively collected data was performed on a consecutive series of patients who underwent arthroscopic treatment of a symptomatic posterior glenoid cartilage defect with micronized allogenic cartilage scaffold between January 2019 and December 2020. The primary outcome was subjective shoulder value (SSV) at latest follow-up. Secondary outcomes included visual analog scale (VAS), recurrence of instability, and range of motion (ROM).

Results

Seven patients, including 4 in the setting of primary posterior instability and 3 in the setting of recurrent symptoms after arthroscopic posterior glenohumeral stabilization, were included in the analysis with a mean follow up of 2.6 years (range, 2-3.7 years). Statistically significant improvements were seen in SSV (median = 40, interquartile range [IQR] = 40-50 before surgery; vs median = 85, IQR = 67.5-87.5 after surgery; P = .018) and VAS (median = 4, IQR = 4-6.3 before surgery; vs median = 1, IQR = 0-1.5 after surgery; P = .010). No significant differences were seen in ROM. There were no cases of recurrent instability or reoperation.

Conclusions

The use of micronized allogenic cartilage scaffold for glenoid cartilage defects is associated with clinical improvement at 2-year follow-up. This is the case when performed in conjunction with index posterior labral repair when there is a concomitant glenoid cartilage defect or when performed in the setting of persistent pain and mechanical symptoms after prior posterior labral repair.

Level of Evidence

Level IV, therapeutic case series.

Determining the True Incidence of Glenohumeral Instability Among Players in the National Football League: An Epidemiological Study of Non-Missed Time Shoulder Instability Injuries

Background

Shoulder instability encompasses a spectrum of glenohumeral pathology ranging from subluxation to dislocation. While dislocation frequently leads to removal from play, athletes are often able to play through subluxation. Previous research on glenohumeral instability among athletes has largely focused on missed-time injuries, which has likely disproportionately excluded subluxation injuries and underestimated the overall incidence of shoulder instability.

Purpose

To describe the epidemiology of shoulder instability injuries resulting in no missed time beyond the date of injury (non-missed time injuries) among athletes in the National Football League (NFL).

Study Design

Descriptive epidemiology study.

Methods

The NFL's electronic medical record was retrospectively reviewed to identify non-missed time shoulder instability injuries during the 2015 through 2019 seasons. For each injury, player age, player position, shoulder laterality, instability type, instability direction, injury timing, injury setting, and injury mechanism were recorded. For injuries that occurred during games, incidence rates were calculated based on time during the season as well as player position. The influence of player position on instability direction was also investigated.

Results

Of the 546 shoulder instability injuries documented during the study period, 162 were non-missed time injuries. The majority of non-missed time injuries were subluxations (97.4%), occurred during games (70.7%), and resulted from a contact mechanism (91.2%). The overall incidence rate of game-related instability was 1.6 injuries per 100,000 player-plays and was highest during the postseason (3.5 per 100,000 player-plays). The greatest proportion of non-missed time injuries occurred in defensive secondary players (28.4%) and offensive linemen (19.8%), while kickers/punters and defensive secondary players had the highest game incidence rates (5.5 and 2.1 per 100,000 player-plays, respectively). In terms of direction, 54.3% of instability events were posterior, 31.9% anterior, 8.5% multidirectional, and 5.3% inferior. Instability events were most often anterior among linebackers and wide receivers (50% and 100%, respectively), while posterior instability was most common in defensive linemen (66.7%), defensive secondary players (58.6%), quarterbacks (100.0%), running backs (55.6%), and tight ends (75.0%).

Conclusion

The majority of non-missed time shoulder instability injuries (97.4%) were subluxations, which were likely excluded from or underreported in previous shoulder instability studies due to the inherent difficulty of detecting and diagnosing shoulder subluxation.

Risk Factors for Glenoid Bone Loss in the Setting of Posterior Glenohumeral Instability

Background

Posterior instability has been reported to account for up to 24% of cases of shoulder instability in certain active populations. However, there is a paucity of data available regarding the risk factors associated with posterior glenoid bone loss.

Purpose

To characterize the epidemiology of, and risk factors associated with, glenoid bone loss within a cohort of patients who underwent primary arthroscopic shoulder stabilization for isolated posterior-type glenohumeral instability.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

This was a retrospective analysis of patients who underwent primary arthroscopic shoulder stabilization for posterior-type instability between January 2011 and December 2019. Preoperative magnetic resonance arthrograms were used to calculate posterior glenoid bone loss using a perfect circle technique. Patient characteristics and revision rates were obtained. Bone loss (both in millimeters and as a percentage) was compared between patients based on sex, age, arm dominance, sports participation, time to surgery, glenoid version, history of trauma, and number of anchors used for labral repair.

Results

Included were 112 patients with a mean age of 28.66 ± 10.07 years; 91 patients (81.25%) were found to have measurable bone loss. The mean bone loss was 2.46 ± 1.68 mm (8.98% ± 6.12%). Significantly greater bone loss was found in athletes versus nonathletes (10.09% ± 6.86 vs 7.44% ± 4.56; P = .0232), female versus male patients (11.17% ± 6.53 vs 8.17% ± 5.80; P = .0212), and patients dominant arm involvement versus nondominant arm involvement (10.26% ± 5.63 vs 7.07% ± 6.38; P = .0064). Multivariate regression analysis identified dominant arm involvement as an independent risk factor for bone loss (P = .0033), and dominant arm involvement (P = .0024) and athlete status (P = .0133) as risk factors for bone loss >13.5%. At the conclusion of the study period, 7 patients had experienced recurrent instability (6.25%).

Conclusion

The findings of this study are in alignment with existing data suggesting that posterior glenoid bone loss is highly prevalent in patients undergoing primary arthroscopic stabilization for posterior-type shoulder instability. Our results suggest that patients with dominant arm involvement are at risk for greater posterior glenoid bone loss. Athlete status and dominant arm involvement were identified as independent risk factors for bone loss >13.5%.

Utility of Talus Osteochondral Allograft Augmentation for Varying Hill-Sachs Lesion Sizes: A Cadaveric Study

Background

Humeral head reconstruction with fresh osteochondral allografts (OCA) serves as a potential treatment option for anatomic reconstruction. More specifically, talus OCA is a promising graft source because of its high congruency with a dense cartilaginous surface.

Purpose

To analyze the surface geometry of the talus OCA plug augmentation for the management of shoulder instability with varying sizes of Hill-Sachs lesions (HSLs).

Study Design

Controlled laboratory study.

Methods

Seven fresh-frozen cadaveric shoulders were tested in this study. The humeral heads were analyzed using actual patients' computed tomography scans. Surface laser scan analysis was performed on 7 testing states: (1) native state; (2) small HSL; (3) talus OCA augmentation for small HSL; (4) medium HSL; (5) talus OCA augmentation for medium HSL; (6) large HSL; and (7) talus OCA augmentation for large HSL. OCA plugs were harvested from the talus allograft and placed in the most medial and superior aspect of each HSL lesion. Surface congruency was calculated as the mean absolute error and the root mean squared error in the distance. A 1-way repeated-measures analysis of variance was performed to evaluate the effects of the difference in the HSL size and associated talus OCA plugs on surface congruency and the HSL surface area.

Results

The surface area analysis of the humeral head with the large (1469 ± 75 mm2), medium (1391 ± 81 mm2), and small (1230 ± 54 mm2) HSLs exhibited significantly higher surface areas than the native state (1007 ± 88 mm2; P < .001 for all sizes). The native state exhibited significantly lower surface areas as compared with after talus OCA augmentation for large HSLs (1235 ± 63 mm2; P < .001) but not for small or medium HSLs. Talus OCA augmentation yielded improved surface areas and congruency after treatment in small, medium, and large HSLs (P < .001).

Conclusion

Talus OCA plug augmentation restored surface area and congruency across all tested HSLs, and the surface area was best improved with the most common HSLs-small and medium.

Clinical Relevance

Talus OCA plugs may provide a viable option for restoring congruity of the shoulder in patients with recurrent anterior glenohumeral instability and an HSL.

Correlation of Acromial Morphology With Risk and Direction of Shoulder Instability: An MRI Study

BACKGROUND

The influence of bony morphology on the development of posterior shoulder instability is not well known.

PURPOSE

To determine if acromial morphology, as measured on magnetic resonance imaging (MRI), is associated with posterior or anterior shoulder instability.

DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

MRI measurements of posterior acromial coverage (PAC), posterior acromial height (PAH), posterior acromial tilt (PAT), and anterior acromial coverage (AAC) were completed for 3 separate matched groups who underwent surgical intervention: posterior instability, anterior instability, and a comparison group of patients who underwent arthroscopic surgery for snapping scapula. Inclusion criteria were patients with recurrent instability <40 years of age without multidirectional instability, glenoid bone loss >13.5%, or glenoid retroversion >10%.

RESULTS

Overall, 37 patients were included in each group. PAC was significantly less in the posterior instability group than in the anterior instability and comparison groups (68.3° vs 88.7° vs 81.7°; P < .001). PAH was significantly greater in the posterior group than in the anterior instability group (11.0 mm vs -0.1 mm; P < .001) and comparison group (0.7 mm; P < .001). There was no difference between the posterior and anterior groups in terms of PAT or AAC (P = .45 and P = .05, respectively). PAT was significantly smaller in the posterior instability group than the comparison group (55.2° vs 62.2°; P = .026). The anterior and comparison groups were not significantly different in PAH or PAT (P = .874 and P = .067, respectively) but were significantly different in AAC (P = .026).

CONCLUSION

A higher and flatter posterior acromion, as measured on preoperative MRI, appears to be associated with patients who require arthroscopic capsulolabral repair due to posterior shoulder instability. This information may help clinicians to both diagnose and predict the need for operative intervention for patients with posterior labral tears.

Humeral Head Reconstruction With Osteochondral Allograft: Bone Plug Optimization for Hill-Sachs Lesions Using CT-Based Computer Modeling Analysis

Background

Engaging Hill-Sachs lesions (HSLs) pose a significant risk for failure of surgical repair of recurrent anterior shoulder instability. Reconstruction with fresh osteochondral allograft (OCA) has been proposed as a treatment for large HSLs.

Purpose

To determine the optimal characteristics of talus OCA bone plugs in a computer-simulated HSL model.

Study Design

Descriptive laboratory study; Level of evidence, 6.

Methods

Included were 132 patients with recurrent anterior instability with visible HSLs; patients who had multidirectional instability or previous shoulder surgery were excluded. Three-dimensional computed tomography models were constructed, and a custom computer optimization algorithm was generated to maximize bone plug surface area at the most superior apex (superiorization) and minimize its position relative to the most medial margin of the HSL defect (medialization). The optimal number, diameter, medialization, and superiorization of the bone plug(s) were reported. Percentages of restored glenoid track width and conversion from off- to on-track HSLs after bone plug optimization were calculated.

Results

A total of 86 patients were included in the final analysis. Off-track lesions made up 19.7% of HSLs and, of these, the mean bone plug size was 9.9 ± 1.4 mm, with 2.2 mm ± 1.7 mm of medialization and 3.3 mm ± 2.9 mm of superiorization. The optimization identified 21% of HSLs requiring 1 bone plug, 65% requiring 2 plugs, and 14% requiring 3 plugs, with a mean overall coverage of 60%. The mean width of the restored HSLs was 68%, and all off-track HSLs (n = 17) were restored to on-track. A Jenks natural-breaks analysis calculated 3 ideal bone plug diameters of 8 mm (small), 10.4 mm (medium), and 12 mm (large) in order to convert this group of HSLs to on-track.

Conclusion

Using a custom computer algorithm, we have demonstrated the optimal talus OCA bone plug diameters for reconstructing HSLs to successfully restore the HSL track and, on average, 60% of the HSL surface area and 68% of the HSL width.

Clinical Relevance

Reconstructing HSLs with talus OCA is a promising treatment option with excellent fit and restoration of HSLs. This study will help guide surgeons to optimize OCA bone plugs from the humeral head, femoral head, and talus for varying sizes of HSLs.

Outcomes After Revision Posterior Shoulder Capsulolabral Repair in Adolescent Athletes

Background

Few studies have evaluated the outcomes of posterior arthroscopic capsulolabral repair in adolescents, especially with regard to outcomes after revision repair.

Hypothesis

Adolescent athletes who undergo revision arthroscopic posterior unidirectional capsulolabral repair will have similar outcomes and return to play when compared with adolescent athletes who underwent primary arthroscopic posterior unidirectional capsulolabral repair.

Study Design

Cohort study; Level of evidence, 3.

Methods

Data were reviewed from patients who underwent posterior shoulder stabilization between 2000 and 2019 and had a minimum follow-up of 2 years. Patients <11 and >19 years of age and those with multidirectional instability were excluded. Revision surgery was defined as repeat arthroscopic posterior capsular repair. The ability to return to sport (and level of sport), clinical outcomes scores (American Shoulder and Elbow Surgeons [ASES] and visual analog scale for pain), and patient-reported perception of range of motion, strength, and satisfaction were recorded. Comparisons between the primary and revision cohorts were made using the chi-square or the Mann-Whitney U test.

Results

Included were 180 adolescent patients (182 shoulders) who underwent a primary unidirectional posterior stabilization, with an average follow-up of 6.1 years. Of these patients, 17 patients required revision surgery (9.3% revision rate). At the final follow-up, patients who underwent revision surgery returned to sport at similar rates to those who did not (70.6% vs 85.9%; P = .095) and were similarly likely to return to their presurgery level of play (41.1% vs 23.7%; P = .10). The no-revision patients had higher ASES scores (76.1 vs 87.1; P = .007) as well as less pain and improved subjective range of motion scores. However, both groups had similar subjective strength scores, and both reported that surgical repair was satisfactory (no revision, 93.2% vs revision, 88.2%; P = .45).

Conclusion

Adolescent athletes had a low risk of revision surgery and frequently returned to play after arthroscopic posterior capsulolabral repair, often at a lower level of play. Those who required revision surgery had poorer outcome scores but still reported a high rate of satisfaction.

Trends in the surgical treatment of posterior shoulder instability in the United States from 2016 to 2020

Background

The purpose of this study was to describe trends in the incidence of open versus arthroscopic management of posterior shoulder instability (PSI) as well as the patients undergoing these procedures in the United States over time.

Methods

The PearlDiver Patient Records Database was utilized for this study. Cases of PSI and surgery were identified via the appropriate ICD-10-CM and CPT codes. Linear regression and two-sample Student's t-test were used to analyze incidence rates, procedure type, number of instability events, and patient age.

Results

A total of 5655 patients were identified as having PSI, undergoing a total of 686 capsulorraphies. The incidence of PSI treated surgically increased across the years of the study at a rate of 0.0293 per 100,000 person-years with an incidence in 2019-2020 greater than in 2016-2018 (p = 0.0151). Patients undergoing arthroscopic capsulorrhaphy were on average younger than those undergoing open capsulorrhaphy (p = 0.0021). Patients experienced a higher number of posterior instability events before open surgery compared to arthroscopic (p = 0.0274).

Discussion

The incidence of surgical treatment of PSI in the United States is steadily rising, with greater than 90% of cases being treated arthroscopically. Those undergoing arthroscopic posterior stabilization are both younger and face fewer instability events prior to surgery.

Prevalence and Risk Factors of Glenoid Bone Loss in Combined Shoulder Instability in Young, Active-Duty Military Patients

Background

US military servicemembers experience higher rates of posterior and combined-type instability as compared with their nonmilitary peers.

Purpose

(1) To determine the prevalence of glenoid bone loss (GBL) in young, active-duty military patients with combined-type shoulder instability who underwent operative shoulder stabilization; (2) to evaluate whether GBL is associated with differences in postoperative outcomes; and (3) to identify factors associated with larger defects.

Study Design

Case series; Level of evidence, 4.

Methods

This study included active-duty military patients who underwent primary surgical shoulder stabilization for combined anterior and posterior capsulolabral tears between January 2012 and December 2018. Preoperative magnetic resonance arthrograms were used to calculate anterior, posterior, and total GBL using the "perfect circle" technique. We recorded patient characteristics, revisions, complications, return to duty, range of motion, and scores on multiple outcome measures (visual analog scale for pain, Single Assessment Numeric Evaluation, American Shoulder and Elbow Surgeons, and Rowe). GBL prevalence was compared by time to surgery, glenoid version, history of trauma, and number of anchors used for labral repair. Outcome scores, return to active duty, and revision procedures were compared by degree of anterior or posterior GBL: <13.5% (mild) versus ≥13.5% (subcritical).

Results

GBL was noted in 28 (77.8%) of the 36 patients. Nineteen (52.8%) patients had anterior GBL, 18 (50.0%) had posterior, and 9 (25.0%) had combined. Four (11.1%) patients had subcritical anterior or posterior GBL. Increased posterior GBL was associated with history of trauma (P = .041), time to surgery >12 months (P = .024), and glenoid retroversion ≥9° (P = .010); increased total GBL was associated with longer time to surgery (P = .023) and labral repair requiring >4 anchors (P = .012); and increased anterior GBL was associated with labral repair requiring >4 anchors (P = .011). There were statistically significant improvements on all outcome measures, with no changes in range of motion postoperatively. No significant difference on any outcome score was observed between patients with mild and subcritical GBL.

Conclusion

In our analysis, 78% of patients had appreciable GBL, suggesting that GBL is highly prevalent in this patient population. Longer time to surgery, traumatic cause, significant glenoid retroversion, and large labral tears were identified as risk factors for increased GBL.

Biomechanical Evaluation of Posterior Shoulder Instability With a Clinically Relevant Posterior Glenoid Bone Loss Model

BACKGROUND

Existing biomechanical studies of posterior glenoid bone loss and labral pathology are limited by their use of anterior instability models, which differ in both orientation and morphology and have been performed in only a single, neutral arm position.

PURPOSE

To evaluate the biomechanical effectiveness of a posterior labral repair in the setting of a clinically relevant posterior bone loss model in various at-risk arm positions.

STUDY DESIGN

Controlled laboratory study.

METHODS

Ten fresh-frozen cadaveric shoulders were tested in 7 consecutive states using a 6 degrees of freedom robotic arm: (1) native, (2) posterior labral tear (6-9 o'clock), (3) posterior labral repair, (4) mean posterior glenoid bone loss (7%) with labral tear, (5) mean posterior glenoid bone loss with labral repair, (6) large posterior glenoid bone loss (28%) with labral tear, and (7) large posterior glenoid bone loss with labral repair. Bone loss was created using 3-dimensional printed computed tomography model templates. Biomechanical testing consisted of 75 N of posterior-inferior force and 75 N of compression at 60° and 90° of flexion and scaption. Posterior-inferior translation, lateral translation, and peak dislocation force were measured for each condition.

RESULTS

Labral repair significantly increased dislocation force independent of bone loss state between 10.1 and 14.8 N depending on arm position. Dislocation force significantly decreased between no bone loss and small bone loss (11.9-13.5 N), small bone loss and large bone loss (9.4-14.3 N), and no bone loss and large bone loss (21.2-26.5 N). Labral repair significantly decreased posterior-inferior translation compared with labral tear states by a range of 1.0 to 2.3 mm. In the native state, the shoulder was most unstable in 60° of scaption, with 29.9 ± 6.1-mm posterior-inferior translation.

CONCLUSION

Posterior labral repair improved stability of the glenohumeral joint, and even in smaller to medium amounts of posterior glenoid bone loss the glenohumeral stability was maintained with labral repair in this cadaveric model. However, a labral repair with large bone loss could not improve stability to the native state.

CLINICAL RELEVANCE

This study shows that larger amounts of posterior glenoid bone loss (>25%) may require bony augmentation for adequate stability.

Diagnosis of Posterior and Combined-Type Shoulder Instability: A 10-Year Cross-sectional Study From a Single Military Base

Background

Large variations exist in the reported frequency and etiology of posterior and combined shoulder instability in the active-duty military population.

Purpose

To compare imaging and clinical examination findings as well as reoperation rates between active-duty military patients who underwent surgery for anterior, posterior, and combined-type shoulder instability.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

A retrospective review was conducted on patients treated surgically for shoulder instability from a single military base from January 2010 to December 2019. Each case was characterized as isolated anterior, isolated posterior, or combined, according to arthroscopic findings. Information was collected on patient characteristics, history of trauma, time to surgery, associated pathological findings, and survivorship at a minimum 2-year follow-up.

Results

Overall, 416 patients (n = 394 men; n = 22 women), with a mean age of 29.1 years, underwent primary shoulder stabilization surgery during the study period. There were 158 patients (38%) with isolated anterior instability, 139 (33%) with isolated posterior instability, and 119 (29%) with combined instability. A history of trauma was more prevalent with isolated anterior instability (129 [81.7%]) than with either isolated posterior (95 [68.4%]) or combined instability (73 [61.3%]) (P = .047 and P = .001, respectively). Patients with anterior instability were significantly more likely to be diagnosed on the preoperative physical examination when compared with patients with posterior instability (93% vs 79.1%; P < .001) or combined instability (93% vs 75.6%; P < .001) and were also more likely to have a discrete labral tear detected on a preoperative magnetic resonance arthrogram than patients with posterior instability (82.9% vs 63.3%; P < .001). There was no significant difference in the rate of medical discharge or recurrent instability requiring reoperation between groups.

Conclusion

The study findings indicated that young, active-duty military patients are at increased risk for isolated posterior and combined-type shoulder instability, with posterior and combined instability collectively accounting for over 60% of instability cases in this cohort. Orthopaedic surgeons should be aware of instability when evaluating and treating young, active-duty military patients with shoulder pain, even in the absence of diagnostic physical examinations or imaging findings.

Posterior Labral Repair Using Knotless "All-Suture" Suture Anchors

Isolated posterior instability is well described but relatively uncommon, accounting for less than 10% of all shoulder instability cases. When nonoperative management fails, surgical outcomes demonstrate improved patient-reported outcomes with a high level of return to sport. Knotless suture anchor and "all-suture" suture anchor technology are now available and used for instability procedures in the shoulder. This technical description describes knotless "all-suture" suture anchor fixation for isolated posterior labral tears.

Outcomes of Revision Arthroscopic Posterior Labral Repair and Capsulorrhaphy: A Systematic Review

Background

Failure rates up to 14% have been reported after arthroscopic posterior capsulolabral repair. It is unknown if revision arthroscopic posterior capsulolabral stabilization has inferior restoration of stability and return to sport when compared with primary repair. Optimal management of failed posterior capsulolabral stabilization is unknown.

Purpose

To report outcomes of revision posterior capsulolabral repair and factors that contribute to failure and to determine optimal management of failed posterior stabilization procedures.

Study Design

Systematic review; Level of evidence, 4.

Methods

A computerized search of the PubMed, EMBASE, and Web of Science databases and manual screening of selected article reference lists were performed in January 2022. Randomized controlled trial, cohort, case-control, and case series studies reporting clinical outcomes of revision arthroscopic posterior capsulolabral repair were eligible. Patient characteristics, indications for revision, intraoperative findings, surgical techniques, and patient-reported outcomes were recorded. Owing to heterogeneity of reported outcomes, data were summarized and presented without pooled statistics.

Results

Only 3 of the 990 identified studies met inclusion criteria. The included studies encompassed 26 revision arthroscopic posterior capsulolabral repairs, with follow-up ranging from 2.3 to 5.3 years. The failed index procedure was arthroscopic capsulolabral repair with suture anchors (n = 22) or posterior thermal capsulorrhaphy (n = 4). The primary indications for revision were recurrent instability and pain. Six patients experienced recurrent instability after revision. Patient satisfaction ranged from 15% to 25%.

Conclusion

This systematic review of 3 studies demonstrated that the incidence of persistent pain and recurrent instability after revision arthroscopic posterior shoulder stabilization is common, and despite slight improvement in patient-reported outcomes, many patients are dissatisfied with their clinical outcomes. Revision arthroscopic posterior shoulder stabilization appears to have a significant failure rate, and there is need for additional prospective studies to help determine the best intervention for these patients.

Posterior Shoulder Instability in Tennis Players: Aetiology, Classification, Assessment and Management

Background

Micro-traumatic posterior shoulder instability (PSI) is an often missed and misdiagnosed pathology presenting in tennis players. The aetiology of micro-traumatic PSI in tennis players is multifactorial, including congenital factors, loss of strength and motor control, and sport-specific repetitive microtrauma. Repetitive forces placed on the dominant shoulder, particularly combinations of flexion, horizontal adduction, and internal rotation contribute to the microtrauma. These positions are characteristic for kick serves, backhand volleys, and the follow-through phase of forehands and serves. The aim of this clinical commentary is to present an overview of the aetiology, classification, clinical presentation, and treatment of micro-traumatic PSI, with a particular focus on tennis players.

Level of Evidence

5.

Lack of Consensus in Rehabilitation Protocols After Posterior Shoulder Stabilization

Background

Posterior shoulder instability is being identified and treated more frequently by orthopaedic providers. After posterior shoulder stabilization, long-term outcomes in function and mobility are largely dependent on the postoperative rehabilitation period. Thus, it is important to assess the consistency between protocols at different institutions.

Purpose/Hypothesis

The purpose of this study was to investigate the variability among rehabilitation protocols published by academic orthopaedic programs and their affiliates. It was hypothesized that there would be little consistency in the duration of immobilization, timing of functional milestones, and start dates of various exercises.

Study Design

Cross-sectional study.

Methods

Rehabilitation protocols after posterior shoulder stabilization that were published online from Accreditation Council for Graduate Medical Education (ACGME)-accredited orthopaedic surgery programs and their affiliates were evaluated for recommendations on immobilization, exercises, activities, range of motion (ROM), and return-to-sport goals.

Results

Of the 204 ACGME-accredited orthopaedic surgery programs, 22 programs and 17 program affiliates had publicly available rehabilitation protocols that were included for review. There were 37 programs (94.9%) that recommended the use of sling immobilization for a mean of 4.7 ± 1.8 weeks postoperatively. Active ROM of the elbow, wrist, and hand was the most common early ROM exercise to be recommended (36 programs; 92.3%). The goal of 90° passive external rotation demonstrated the widest range of recommended start dates (0-12 weeks postoperatively). Late ROM exercises and start dates varied between protocols, with the largest standard deviation found in achieving full active ROM (13.5 ± 3.6 weeks). Resistance exercises showed a wide range of recommended start dates. Bench presses and push-ups began, on average, at 13.1 ± 3.4 and 15.3 ± 3.2 weeks, respectively. Return to sport was recommended at 21.7 ± 3.6 weeks.

Conclusion

There was a high level of variability in postoperative rehabilitation protocols after posterior shoulder stabilization among orthopaedic programs and their affiliates, suggesting that a standard protocol for rehabilitation has yet to be established.

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.

Glenoid Bone Loss Pattern in Patients With Posterior Instability Versus Anterior Instability: A Matched Cohort Study

Background

The pattern of glenoid bone loss (GBL) in anterior glenohumeral instability is well described. It was recognized recently that posterior GBL after instability has a posteroinferior pattern.

Purpose/Hypothesis

The purpose of this study was to compare GBL patterns in a matched cohort of patients with anterior versus posterior glenohumeral instability. The hypothesis was that the GBL pattern in posterior instability would be more inferior than the GBL pattern in anterior instability.

Study Design

Cohort study; Level of evidence, 3.

Methods

In this multicenter retrospective study, 28 patients with posterior instability were matched with 28 patients with anterior instability by age, sex and number of instability events. GBL location was defined using a clockface model. Obliquity was defined as the angle between the long axis of the glenoid and a line tangent to the GBL. Superior and inferior GBL were measured as areas and defined relative to the equator. The primary outcome was the 2-dimensional characterization of posterior versus anterior GBL. The secondary outcome was a comparison of the posterior GBL patterns in traumatic and atraumatic instability mechanisms in an expanded cohort of 42 patients.

Results

The mean age of the matched cohorts (n = 56) was 25.2 ± 9.87 years. The median obliquity of GBL was 27.53° (interquartile range [IQR], 18.83°-47.38°) in the posterior cohort and 9.28° (IQR, 6.68°-15.75°) in the anterior cohort (P < .001). The mean superior-to-inferior bone loss ratio was 0.48 ± 0.51 in the posterior cohort and 0.80 ± 0.55 (P = .032) in the anterior cohort. In the expanded posterior instability cohort (n = 42), patients with traumatic injury mechanism (n = 22), had a similar GBL obliquity compared to patients with an atraumatic injury mechanism (n = 20) (mean, 27.73° [95% CI, 20.26°-35.20°] vs 32.20° [95% CI, 21.27°-43.14°], respectively) (P = .49).

Conclusion

Posterior GBL occurred more inferiorly and at an increased obliquity compared with anterior GBL. This pattern is consistent for traumatic and atraumatic posterior GBL. Bone loss along the equator may not be the most reliable predictor of posterior instability, and critical bone loss may be reached more rapidly than a model of loss along the equator may predict.

Dynamic Posterior Instability Test: A New Test for Posterior Glenohumeral Instability

Background

Recurrent posterior shoulder instability has become an increasingly recognized cause of shoulder disability, especially among athletes. The presentation can be vague and therefore its clinical diagnosis is often overlooked. Few diagnostic tests exist and these tests are difficult to perform in an anxious and apprehensive patient. Many also lack high specificity and do not effectively distinguish posterior labral tears from other shoulder pathologies. As a result, the authors worked to develop a new test, the dynamic posterior instability test (DPIT). The purpose of this study was to describe the DPIT as well as a modified DPIT test and to evaluate the accuracy of these tests in detecting posterior labral pathology. It was hypothesized that the dynamic posterior instability test (DPIT) would improve accuracy in the evaluation of posterior labral tears.

Methods

For a 9-month period, the DPIT and modified DPIT tests were performed on all patients evaluated for posterior instability of the shoulder. The records of all patients who had undergone a posterior labral repair (type VIII SLAP and posterior labral tears) were reviewed. The results of the DPIT and modified DPIT tests were compared to intra-operative findings. Anterior glenohumeral instability patients were also evaluated with these tests to serve as a control.

Results

Fifty-one patients had a positive and 3 patients had a negative DPIT test. Of the anterior instability patients, there was 1 positive and 19 negative test results. The sensitivity of the DPIT test was 94.4%, specificity 95%, the positive predictive value 0.98, and the negative predictive value 0.86. The results of the modified DPIT were the same as the DPIT test.

Conclusions

The DPIT and modified DPIT tests provide a valuable new tool when combined with history and other physical examination findings improve the accuracy of diagnosis of posterior shoulder instability.

Open and arthroscopic posterior bone block with iliac crest autograft for posterior shoulder instability - systematic review of clinical and radiological outcomes

INTRODUCTION

Posterior shoulder instability (PSI) is a rare and challenging pathology to manage. The aim of this review was to assess and compare whether open and arthroscopic iliac crest bone graft (ICBG) bone block procedures succeeded in improving functional and clinical outcomes as well as radiological outcomes of union and graft resorption.

HYPOTHESIS

We hypothesised that there will be no difference in recurrence rate and functional outcome between open and arthroscopic procedures but there will be a higher complication rate with open bone block procedures.

METHODS

A systematic review was conducted in accordance with PRISMA guidelines using the online databases MEDLINE and Embase. The review was registered on the PROSPERO database. Studies of open or arthroscopic ICBG bone block procedures reporting patient reported outcome measures, recurrence, complications and progression to osteoarthritis and radiological outcomes of graft union and resorption were selected. Studies were appraised using the Methodical index for non-randomised studies (MINORS) tool.

RESULTS

14 studies satisfied the inclusion criteria; five studies were arthroscopic and nine used open techniques. A total of 183 patients and 201 shoulders were included, mean age was 25 years range (14-75 years). Recurrent instability ranged from 0% to 12.5% for arthroscopic and 0% to 36.4% for open studies. Arthroscopic studies had statistically significant increases in numerous functional outcome scores but there was no evidence for similar improvements in open studies. Osteoarthritis at follow-up ranged from 12.5% to 47% in arthroscopic and 0% to 81.8% for open studies. Arthroscopic complication rate ranged from 6.7% to 75% compared to 0% to 80% for open studies. Majority of complications were metalware related requiring surgical intervention. Partial graft resorption ranged from 7.7-100% after arthroscopic and 4.8-100% after open procedures. High union rates were seen with both open and arthroscopic techniques.

CONCLUSION

This study highlights a lack of high-level evidence for arthroscopic and open posterior bone block procedures using ICBG to manage PSI. Functional and instability outcome scores showed significant improvement with arthroscopic ICBG bone block procedures however limited evidence was available for open studies. Metalwork related complications requiring revision and radiographic progression to osteoarthritis was high in both arthroscopic and open studies.

LEVEL OF EVIDENCE

IV, systematic review.

The Thumb Test: A Simple Physical Examination Maneuver for the Diagnosis of Symptomatic Posterior Shoulder Instability

Posterior shoulder instability is becoming increasingly recognized in young active patient populations. Diagnosing posterior instability can be challenging because patients commonly present with a complaint of pain without a history of a dislocation or subluxation event. Additionally, a posterior labral tear is not always clearly visualized on advanced imaging studies. As such, physical examination is critical to the diagnosis. We report a simple physical examination maneuver for the diagnosis of symptomatic posterior shoulder instability. The thumb test attempts to replicate a posterior bone block procedure, helping to re-establish stability and relieve pain. The examiner places his or her thumb over the posterior glenohumeral joint line while the patient actively forward elevates the affected arm overhead. Improvement in pain and stability with this maneuver is diagnostic for symptomatic posterior shoulder instability. This test augments current physical examination maneuvers to assist with correctly diagnosing posterior shoulder instability.

Arthroscopic Bone Block Procedure for Posterior Shoulder Instability: Updated Surgical Technique

Posterior shoulder instability is generally caused by traumatic posterior dislocations or repetitive microtrauma during sports or other activities and has an annual incidence rate of 4.64 per 100,000 person-years. Several surgical techniques to treat posterior shoulder instability have been described, including soft-tissue repair and both open and arthroscopic bone block procedures. However, even though patient-reported outcomes are commonly high, surgical procedures are associated with high complication and revision rates of up to 14% and 67%, respectively. In particular, accurate placement of the bone graft, screw orientation, and the treatment of concomitant lesions are considered challenging. Therefore, improvement of surgical techniques is desirable. This Technical Note describes an updated approach to the arthroscopic posterior bone block augmentation described by Lafosse et al. (2012), with tips and tricks on the harvest and positioning of the graft.

Prospective Evaluation of Posterior Glenoid Bone Loss After First-time and Recurrent Posterior Glenohumeral Instability Events

BACKGROUND

Although posterior glenohumeral instability is becoming an increasingly recognized cause of shoulder pain, the role of posterior glenoid bone loss on outcomes remains incompletely understood.

PURPOSES

To prospectively determine the amount of bone loss associated with posterior instability events and to determine predisposing factors based on preinstability imaging.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

A total of 1428 shoulders were evaluated prospectively for ≥4 years. At baseline, a subjective history of shoulder instability was ascertained for each patient, and bilateral noncontrast magnetic resonance imaging (MRI) scans of the shoulders were obtained regardless of any reported history of shoulder instability. The cohort was prospectively followed during the study period, and those who were diagnosed with posterior glenohumeral instability were identified. Postinjury MRI scans were obtained and compared with the screening MRI scans. Glenoid version, perfect-circle-based bone loss was measured for each patient's pre- and postinjury MRI scans using previously described methods.

RESULTS

Of the 1428 shoulders that were prospectively followed, 10 shoulders sustained a first-time posterior instability event and 3 shoulders sustained a recurrent posterior instability event. At baseline, 11 of 13 shoulders had some amount of glenoid dysplasia and/or bone loss. The change in glenoid bone loss was 5.4% along the axis of greatest loss (95% CI, 3.8%-7.0%; P = .009), 4.4% at the glenoid equator (95% CI, 2.7%-6.2%; P = .016), and 4.2% of total glenoid area (95% CI, 2.9%-5.3%; P = .002). Recurrent glenoid instability was associated with a greater amount of absolute bone loss along the axis of greatest loss compared with first-time instability (recurrent: 16.8% ± 1.1%; 95% CI, 14.6%-18.9%; first-time: 10.0% ± 1.5%; 95% CI, 7.0%-13.0%; P = .005). Baseline glenoid retroversion ≥10° was associated with a significantly greater percentage of bone loss along the axis of greatest loss (≥10° of retroversion: 13.5% ± 2.0%; 95% CI, 9.6%-17.4%; <10° of retroversion: 8.5% ± 0.8%; 95% CI, 7.0%-10.0%; P = .045).

CONCLUSIONS

Posterior glenohumeral instability events were associated with glenoid bone loss of 5%. The amount of glenoid bone loss after a recurrent posterior glenohumeral instability event was greater than that after first-time instability. Glenoid retroversion ≥10° was associated with a greater amount of posterior glenoid bone loss after a posterior instability event.

Arthroscopic Posterior Labral Repair in Active-Duty Military Patients: A Reliable Solution for an At-Risk Population, Regardless of Anchor Type

BACKGROUND

Active-duty servicemembers are a population at risk for the development of posterior shoulder instability. While short-term outcomes after arthroscopic posterior labral repair for posterior shoulder instability are promising, there is a paucity of longer term follow-up data for this procedure.

PURPOSES

The primary purpose was to report midterm outcomes after arthroscopic posterior labral repair in active-duty military patients for posterior shoulder instability without bone loss. The secondary purpose was to determine if outcomes varied between anchor types used.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Preoperative and postoperative outcomes, with a minimum 3-year follow-up, for a visual analog scale for pain, the Single Assessment Numeric Evaluation (SANE), the American Shoulder and Elbow Surgeons (ASES) score, and the Rowe score were collected and analyzed. A separate subgroup analysis was performed comparing the outcomes of patients who underwent repair with biocomposite anchors versus those who underwent repair with all-suture anchors.

RESULTS

A total of 73 patients with a mean follow-up of 82.55 ± 24.20 months met the inclusion criteria and were available for analysis. As a whole, the cohort demonstrated statistically and clinically significant improvements in outcome scores at final follow-up. Preoperative and postoperative range of motion did not vary significantly. While the difference in final outcome scores between the 2 anchor types did not reach statistical significance, a statistically significantly larger proportion of patients who underwent repair with all-suture anchors versus those who underwent repair with biocomposite anchors met the Patient Acceptable Symptom State for the SANE (97.14% vs 78.95%, respectively; P = .0180) and the ASES score (88.57% vs 68.42%, respectively; P = .0171). The proportion of patients who achieved the substantial clinical benefit or surpassed the minimal clinically important difference, however, did not vary by anchor type. Overall, 70 patients (95.89%) remained on active duty and were able to return to preinjury work and recreational activity levels. There were 3 patients (4.11%) who had recurrent posterior instability.

CONCLUSION

This population of active-duty servicemembers undergoing posterior labral repair for posterior labral instability without bone loss demonstrated a statistically and clinically significant improvement in midterm outcomes, a low recurrence rate, and a rate of return to active duty of 95.89%, regardless of the anchor type used.

Single-Portal Arthroscopic Posterior Capsulorrhaphy for Recurrent Shoulder Capsule Laxity and Instability

Arthroscopic stabilization for posterior shoulder instability is well documented in the literature, offering good to excellent clinical outcomes after injury with favorable return-to-sport and patient satisfaction rates. Posterior capsulorrhaphy addresses recurrent laxity by decreasing the size of the posterior capsule through arthroscopic placement of sutures, in addition to addressing posterior labral tears and any intra-articular pathology within the joint. This technical note describes an arthroscopic posterior capsulorrhaphy for recurrent posterior shoulder capsule laxity and instability in an active patient. This technique uses a single posterior working portal and 2 suture anchors to tighten the posterior capsule onto the intact labrum.

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.

Patient Age and Surgical Intervention as Risk Factors for the Development of Osteoarthritis After Posterior Shoulder Instability: A Population-Based Study

Background

Diagnosis and treatment of posterior shoulder instability (PSI) has improved with advances in imaging and surgical technique. However, the relationship between PSI and osteoarthritis (OA) remains unclear.

Purpose

To evaluate a population-based cohort to (1) determine the rate of symptomatic OA, (2) identify patient characteristic risk factors for OA, and (3) evaluate the effect of posterior capsulolabral repair on OA progression.

Study Design

Case-control study; Level of evidence, 3.

Methods

After review of 324 patient records, we included 115 patients (14 female, 101 male) diagnosed with PSI between January 1994 and July 2012 with an average follow-up of 12.5 years (range, 5-23 years). Medical records were reviewed for patient characteristics, injury characteristics, surgical details (if any), and radiographic progression of OA. Kaplan-Meier survival was used to estimate survival free of OA; characteristics associated with OA progression were determined via univariate Cox regression models, and associated 95% CIs and hazard ratios (HRs) are presented.

Results

Overall, 14% (16/115) of patients had radiographic progression of symptomatic glenohumeral arthritis, with 5-year survival of 88.3% (95% CI, 79.7%-97.3%). Older age at the time of instability diagnosis was associated with arthritis progression (10-year unit HR, 1.95; 95% CI, 1.26-3.03). Patients who underwent surgery demonstrated increased radiographic progression of OA (HR, 4.03; 95% CI, 1.23-13.23). There was a trend of increased OA in patients treated with labral debridement compared with repair despite lower baseline levels of OA; however, this difference was not statistically significant (P = .09).

Conclusion

Symptomatic glenohumeral arthritis is not seen routinely in patients with PSI. Although uncommon, an age of at least 30 years at the time of diagnosis and surgical intervention were identified as risk factors for developing symptomatic arthritis at long-term follow-up.

Posterior Glenoid Osteotomy With Capsulolabral Repair Improves Resistance Forces in a Critical Glenoid Bone Loss Model

Background:

There is no widespread consensus on the surgical treatment of posterior shoulder instability with critical posterior glenoid bone loss.

Hypothesis:

That opening posterior glenoid wedge osteotomy with soft tissue repair would improve the resistance forces of instability when compared with soft tissue repair alone in the setting of 20% critical bone lose.

Study Design:

Controlled laboratory study.

Methods:

Native glenoid retroversion was measured on 9 shoulders using computed tomography (CT) scans. The humerus was potted in 90° of forward flexion and 30° of internal rotation relative to the scapula, and a posterior dislocation was performed to create a posterior capsulolabral injury model. The specimens were each taken through a fixed sequence of testing: (1) posteroinferior capsulolabral tear, (2) no glenoid bone loss with posteroinferior capsulolabral repair, (3) 20% posterior glenoid bone loss with posteroinferior capsulolabral repair, and (4) 20% glenoid bone loss with posterior glenoid opening wedge osteotomy and posteroinferior capsulolabral repair. Bone loss was created using a sagittal saw. The resultant peak forces with 1 cm of posterior translation were measured. A 1-way repeated-measures analysis of variance was used to compare mean force values.

Results:

After the initial dislocation event, all shoulders had a resultant posterior capsulolabral injury. The resulting labral injury was extended from 6- to 9-o’clock in all specimens to homogenize the extent of injury. Repairing the capsulolabral complex in the 20% posterior glenoid bone loss group did not result in a statistically significant increase in resistance force compared with the labral deficient group (34.1 vs 22.2 N; P = .068). When 20% posterior bone loss was created, the posterior glenoid osteotomy with capsulolabral repair was significantly stronger (43.8 N) than the posterior repair alone both with (34.1 N) and without (31.8 N) bone loss (P = .008 and .045, respectively).

Conclusion:

In the setting of critical posterior glenoid bone loss, an opening wedge posterior glenoid osteotomy with capsulolabral repair improved resistance to posterior humeral translation significantly compared with capsulolabral repair alone.

Clinical Relevance:

The results of this biomechanical cadaveric study may aid in surgical planning for this complex patient population.

Return to Sport After Surgical Management of Posterior Shoulder Instability: A Systematic Review and Meta-analysis

BACKGROUND

Posterior shoulder instability accounts for a small proportion of all shoulder instability, although it can affect athletes of all types, from contact to overhead athletes. Surgical treatment is quite successful in these patients; however, the literature reports a wide range of rates of return to sport.

PURPOSE/HYPOTHESIS

The purpose was to determine the return-to-sport rates after surgical stabilization for posterior shoulder instability. It was hypothesized that patients would experience a high rate of return to sport.

STUDY DESIGN

Systematic review and meta-analysis; Level of evidence, 4.

METHODS

Embase, PubMed, and MEDLINE were searched for relevant literature from database inception until April 2020, and studies were screened by 2 reviewers independently and in duplicate for studies reporting rates of return to sport after surgical management of posterior shoulder instability. Demographic data as well as data on return to sport and functional outcomes were recorded. A meta-analysis of proportions was used to combine the rates of return to sport using a random effects model. A risk of bias was assessed for all included studies.

RESULTS

Overall, 32 studies met inclusion criteria and comprised 1100 patients (1153 shoulders) with a mean age of 22.8 years (range, 11-65) and a mean follow-up of 43.2 months (range, 10-228). The pooled rate of return to any level of sport was 88% (95% CI, 84%-92%; I² = 68.7%). In addition, the pooled rate of return to the preinjury level was 68% (95% CI, 60%-76%; I² = 79%). Moreover, the pooled return-to-sport rate for contact athletes was 94% (95% CI, 90%-97%; I² = 0%), while for throwing athletes it was 88% (95% CI, 83%-92%; I² = 0%).

CONCLUSION

Surgical management of posterior shoulder instability resulted in a high rate of return to sport, as well as significant pain reduction and functional improvement in most patients. However, only two-thirds of athletes can return to their preinjury levels of sport.

Nonoperative Management of Posterior Shoulder Instability: What Are the Long-Term Clinical Outcomes?

OBJECTIVE

To report the injury characteristics, radiographic findings, and long-term outcomes of nonoperative management for posterior shoulder instability (PSI).

DESIGN

A retrospective review of 143 patients with PSI using a large geographic database.

SETTING

Single county between January 1994 and July 2012.

PATIENTS

A clinical history and diagnosis of PSI, one confirmatory imaging study to support the diagnosis, and a minimum of 5 years follow-up were required for inclusion. Patients with seizure disorders, anterior-only instability, multidirectional instability, and superior labrum from anterior to posterior diagnosis were excluded.

INTERVENTIONS

Patients with PSI were managed nonoperatively or operatively.

MAIN OUTCOME MEASURES

Pain, recurrent instability, and progression into glenohumeral osteoarthritis at long-term follow-up.

RESULTS

One hundred fifteen patients were identified. Thirty-seven (32%) underwent nonoperative management. Twenty (54%) patients were diagnosed with posterior subluxation, 3 (8%) with a single dislocation, and 7 (19%) with multiple dislocations. Symptomatic progression of glenohumeral arthritis was observed in 8% (3) of patients. Pain improved in 46% (17) of patients and worsened in 19% (7). Recurrent instability and progression to osteoarthritis occurred in 15% (3/20) of patients with a traumatic instability event compared with 0% of atraumatic patients after nonoperative management (P = 0.234). Pain at follow-up was more common in nonoperative than operative patients (P = 0.017).

CONCLUSIONS

Nonoperative management is a viable option for many patients with posterior shoulder instability; however, many may continue to have posterior shoulder pain.