Posterior shoulder instability: does glenoid retroversion predict recurrence and contralateral instability?

The clinical impact of glenoid concavity and version on anterior shoulder stability

Background

In recent biomechanical studies, the importance of glenoid concavity and version for anterior shoulder stability has been highlighted. With this study, we aimed to assess their clinical relevance as stabilizing factors. We hypothesized that low glenoid concavity and low retroversion are associated with anterior glenohumeral instability.

Methods

In this single-center, retrospective case-control study, computed tomography scans of n = 34 patients following acute anteroinferior glenohumeral dislocation between 2015 and 2021 were included. Patients with glenoid fractures and pre-existing glenohumeral pathologies were excluded. In the control group, n = 68 polytrauma patients referred to our level-I-trauma center were included, who showed neither acute nor chronic glenohumeral pathologies. Both groups were matched age- and gender-specifically in a 2:1 ratio. Glenoid concavity was measured according to the bony shoulder stability ratio (BSSR) in anterior-posterior (AP) and superior-inferior (SI) direction. Version was measured by the glenoid vault method.

Results

The instability cohort presented with a lower BSSR (SI) compared to the control group (49.8% vs. 56.9%, P = .001). The BSSR (AP) did not differ significantly (30.2% vs. 33.7%, P = .163). A higher retroversion was seen in the instability cohort (-13.1° vs. -11.4°; P = .041). Subgroup analyses showed higher BSSR (SI) in ≥60-year-old patients compared to ≤30-year-old patients. BSSR (AP) and glenoid version did neither differ age- nor gender-specifically.

Conclusion

Glenoid concavity is a relevant factor for anterior shoulder stability in the clinical setting. In contrast to recent biomechanical studies, glenoid version appears to have only limited clinical impact on anterior stability. Regarding the individual treatment of anterior glenohumeral instability, glenoid concavity should be focused on as an essential bony stabilizing factor.

Good functional outcome but high rates of instability recurrence after posterior open-wedge glenoid osteotomy for the treatment of posterior shoulder instability with increased glenoid retroversion at mid-term follow-up

PURPOSE

To evaluate clinical, functional and radiological mid-term outcomes following posterior open-wedge glenoid osteotomy (POWGO) for the treatment of posterior shoulder instability (PSI) associated with increased glenoid retroversion.

METHODS

Patients who underwent POWGO for the treatment of symptomatic PSI with glenoid retroversion >10° and participated in a previous study assessing short-term outcomes were included after a minimum follow-up of 5 years. Clinical (Rowe score and physical examination) and functional outcomes (Oxford Shoulder Instability Score [OSIS] and visual analogue scale [VAS] for pain) were assessed. Preoperative versus follow-up magnetic resonance imaging (MRI) assessments were compared for changes in posterior humeral head subluxation (PHHS) and progression of osteoarthritis (shoulder osteoarthritis severity [SOAS] score).

RESULTS

Eight patients (nine shoulders) were included 92.0 months (88.0-109.5 months) post-operatively, of which seven patients (eight shoulders) underwent MRI. Shoulder function was good (Rowe score: 80.0 [76.3-91.3], OSIS: 41.0 [31.0-41.5]) and pain levels were low (VAS for pain: 3.0 [1.0-3.0]) at follow-up. Overall, the degree of PHHS did not change between preoperatively and follow-up (p > 0.05). Four shoulders demonstrated PHHS preoperatively, of which two had a centred humeral head at follow-up. Shoulder osteoarthritis progressed significantly (SOAS score: 17.0 [11.0-24.5] to 33.0 [31.0-45.0], p = 0.018). Residual PSI was evident in 75.0% of shoulders.

CONCLUSION

At mid-term follow-up, POWGO for PSI associated with increased glenoid retroversion led to good functional outcomes but failed to reliably restore posterior shoulder stability and prevent osteoarthritis progression.

LEVEL OF EVIDENCE

Level IV.

Nonoperative Treatment of Isolated Posterior Glenohumeral Instability in an Active Military Population: Effect of Glenoid and Acromial Morphology

BACKGROUND

Nonoperative management of posterior shoulder instability is common. However, limited data are available to assess the pathomorphologic factors associated with its failure.

PURPOSE/HYPOTHESIS

The purpose of this study was 2-fold: (1) to determine glenohumeral pathomorphologic features predictive of nonoperative management failure of posterior instability; and (2) to determine the relationship between nonoperative management failure and posterior glenoid bone loss (pGBL) progression. It was hypothesized that greater posterior acromial height (PAH) would adversely affect nonoperative survivorship and that shoulders treated nonoperatively would have pGBL progression compared with those undergoing surgical stabilization.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

This was a retrospective review of a consecutive series of patients with isolated posterior shoulder instability, defined as isolated posterior labral tear on magnetic resonance imaging (MRI) with corresponding physical examination findings, who underwent nonoperative management for 6 months and had no previous related surgical history. The primary outcome of interest was the failure of nonoperative management, defined as the inability to return to full military duty or requiring surgical intervention. The morphologic features assessed for association with nonoperative management failure included pGBL, glenoid version, acromial morphology, and posterior humeral head subluxation. We secondarily sought to determine the progression of pGBL on serial MRI scans. Cox proportional hazard analysis was used to evaluate risk factors for failure.

RESULTS

In this study, 42 of 90 (46.7%) patients had failed nonoperative management and went on to receive an arthroscopic stabilization procedure. The group with failed treatment demonstrated a greater humeral head subluxation ratio than those with successful nonoperative management (0.65 ± 0.2 vs 0.62 ± 0.2; P = .038). Cox proportional hazard analysis identified pGBL, greater PAH, less posterior acromial coverage, and posterior humeral subluxation as significant risk factors for failure. Of those with failed nonoperative management, 17 had repeat MRI scans at a mean of 488.2 ± 87 days after index MRI for comparison, demonstrating a statistically significant progression of pGBL (index MRI, 2.68% ± 1.71%) versus after nonoperative treatment failure (6.54% ± 1.59%; P = .003).

CONCLUSION

Failure occurred 47% of the time in patients who underwent nonoperative management for isolated posterior glenohumeral instability for a minimum of 6 months, and it was associated with a greater posterior humeral head subluxation, less posterior acromial coverage, greater PAH, and greater amounts of glenoid retroversion on index MRI. Additionally, those who had repeat MRI approximately 1 year after the index MRI demonstrated greater pGBL compared with the index MRI.

Posterior Glenoid Bone Grafting in the Setting of Excessive Glenoid Retroversion Does Not Provide Adequate Stability in a Cadaveric Posterior Instability Model

BACKGROUND

Excessive glenoid retroversion is a known risk factor for posterior shoulder instability and failure after soft tissue stabilization procedures. Whether excessive glenoid retroversion is a risk factor for failure after posterior glenoid bone grafting is unknown.

PURPOSE

To evaluate the biomechanical effectiveness of posterior iliac crest bone grafting (ICBG) for posterior shoulder instability with increasing glenoid retroversion.

STUDY DESIGN

Controlled laboratory study.

METHODS

Six fresh-frozen cadaveric shoulders had a posterior glenoid osteotomy allowing the glenoid retroversion to be set at 0°, 10°, and 20°. At these 3 preset angles, 4 conditions were simulated consecutively on the same specimen: (1) intact glenohumeral joint, (2) posterior Bankart lesion, (3) 20% posterior glenoid bone defect, and (4) posterior ICBG. Stability was evaluated in the jerk position (60° of glenohumeral anteflexion, 60° of internal rotation) by measuring (A) posterior humeral head (HH) translation (in mm) and (B) peak translational force (in N) necessary for translation of the HH over 25% of glenoid width.

RESULTS

At 0° of retroversion, the ICBG restored posterior HH translation and peak translational force to values comparable with those of the intact condition (P = .649 and P = .979, respectively). At 10° of retroversion, the ICBG restored the peak translational force to a value comparable with that of the intact condition (22.3 vs 24.7 N, respectively; P = .418) but showed a significant difference in posterior HH translation in comparison to the intact condition (4.5 vs 2.0 mm, respectively; P = .026). There was a significant increase in posterior HH translation and significant decrease in peak translational force with the ICBG at 20° of glenoid retroversion compared with the intact condition (posterior HH translation: 7.9 vs 2.0 mm, respectively; P < .006; peak translational force: 15.3 vs 24.7 N, respectively; P = .014).

CONCLUSION

In this cadaveric study, posterior ICBG was able to restore stability to a level comparable to that of the native condition at 0° and to some extent at 10° of retroversion. However, posterior ICBG was not able to provide adequate stability at 20° of glenoid retroversion.

CLINICAL RELEVANCE

Posterior glenoid bone grafting with ICBG should be used with caution when performed in isolation in the setting of posterior instability associated with glenoid bone loss and combined glenoid retroversion of >10°.

A Posterior Acromial Bone Block Augmentation Is Biomechanically Effective at Restoring the Force Required To Translate the Humeral Head Posteriorly in a Cadaveric, Posterior Glenohumeral Instability Model

PURPOSE

To assess the biomechanical utility of a posterior acromial bone block (PABB) for the treatment of posterior glenohumeral instability.

METHODS

Ten fresh-frozen cadaveric specimens were obtained based upon an a priori power analysis. A 2.5-cm scapular spine autograft was harvested from all shoulders. A custom robot device was used to apply a 50-N compressive force to the glenohumeral joint. The humeral head was translated 10 mm posteroinferiorly at 30 degrees from the center of the glenoid at a rate of 1.0 mm/s in 6 consecutive conditions: (1) intact specimen, (2) intact with PABB, (3) posterior capsulolabral tear, (4) addition of the PABB, (5) removal of the PABB and repair of the capsulolabral tear (LR), and (6) addition of the PABB with LR. The maximum force required to obtain this translation was recorded. Paired t tests were performed to compare relevant testing conditions.

RESULTS

Ten cadavers with a mean ± SD age of 54.4 ± 13.1 years and mean ± SD glenoid retroversion of 6.5 ± 1.0 degrees were studied. The PABB provided greater resistance force to humeral head translation compared to the instability state (instability, 29.3 ± 15.3 N vs PABB, 47.6 ± 21.0 N; P = .001; 95% confidence interval [CI], -27.6 to -10.0). When comparing PABB to LR, the PABB produced higher resistance force than LR alone (PABB, 47.6 ± 21.0 N; LR, 34.2 ± 20.5 N; P = .012; 95% CI, -23.4 to -4.1). An instability lesion treated with the PABB, with LR (P = .056; 95% CI, -0.30 to 20.4) or without LR (P = .351; 95% CI, -6.8 to 15.7), produced resistance forces similar to the intact specimen.

CONCLUSIONS

A PABB is biomechanically effective at restoring the force required to translate the humeral head posteriorly in a cadaveric, posterior glenohumeral instability model. A posterior acromial bone block is a biomechanically feasible option to consider in patients with recurrent posterior instability.

CLINICAL RELEVANCE

Augmentation of the posterior acromion may be a biomechanically feasible option to treat posterior shoulder instability.

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.

Rotator Cuff Tears to Shoulder Instability: The Relationship Between Acromial Morphology and Shoulder Pathology

» The acromion is a well-studied region of the scapula that has demonstrated substantial relationships to various shoulder pathologies.» Abnormal acromial morphology is associated with rotator cuff pathology, and our understanding of this risk factor inspired acromioplasty as an adjunctive treatment for rotator cuff tears.» The acromion is linked closely to shoulder kinematics and biomechanics, as it serves as the origin for the deltoid muscle.» In degenerative shoulder disease, eccentric glenohumeral osteoarthritis has been associated with a higher, flatter acromial roof.» Increasing literature is emerging connecting morphology of the acromion with shoulder instability.

Posterior Shoulder Instability but Not Anterior Shoulder Instability Is Related to Glenoid Version

Purpose

To assess and compare glenoid version in patients with anterior shoulder instability (ASI), posterior shoulder instability (PSI), and a control group.

Methods

The operative notes of all patients that had undergone arthroscopic shoulder instability repair between January 2017 and May 2022 were retrospectively reviewed. Magnetic resonance imaging scans were then analyzed, and glenoid version was measured by a single blinded observer. A P value <.05 was considered statistically significant.

Results

There were 100 patients included in the ASI group, 65 in PSI group, and 100 in the control group. The mean glenoid versions for the ASI group were -16°, -9.1°, and -9.2° for the vault version, simplified vault version, and chondrolabral version, respectively. The mean glenoid versions for the PSI group were -21°, -13.4°, and -16.6° for the vault version, simplified vault version, and chondrolabral version, respectively. The mean versions for the control group were -17.8°, -9.5°, and -9.8° for the vault version, simplified vault version and chondrolabral version, respectively. ANOVA testing and post hoc comparisons revealed the PSI group to be significantly more retroverted than both other groups P < .001. The ASI group's degree of glenoid version was not significantly different to that of the control P = .009.

Conclusion

Patients with PSI have a higher degree of retroversion in comparison to those with ASI and control. There is no significant difference in glenoid version among patients with ASI when compared with control.

Level of Evidence

Level III, retrospective comparative study.

Posterior Glenoid Bone Loss and Instability: An Evidence-based Approach to Diagnosis and Management

Posterior glenohumeral instability is an underappreciated cause of disability that may necessitate surgical intervention to allow functional glenoid restoration. However, posterior glenoid bone abnormalities, when sufficiently severe, may contribute to persistent instability despite a well-performed capsulolabral repair. Recognition and understanding of these lesions is critical to both surgical decision making and execution of the surgical plan. Numerous procedures have been described to address posterior instability including recent developments in arthroscopic grafting techniques. The purpose of this article was to provide an evidence-based strategy for diagnosis and management of posterior shoulder instability and glenoid bone loss.

Physical Therapy for the Treatment of Shoulder Instability

Shoulder instability is the separation of the humeral head from the glenoid. Injury to the static and dynamic stabilizers can result in instability. Anterior shoulder instability is the predominant form of instability. It is usually a result of trauma. Posterior shoulder instability often presents with an insidious onset of pain. Multidirectional instability of the shoulder is symptomatic laxity in more than one plane of motion. The primary goal of rehabilitation is to restore pain-free mobility, strength, and functioning. Rehabilitation implements range of motion and strengthening exercises to restore proprioceptive control and scapular kinematics.

Three-Dimensional Scapular Border Method for Glenoid Version Measurements

Variations among methods to measure glenoid version have created uncertainty regarding which method provides the most consistent measurements of morphology. Greater deformity may also make accurate depiction of the native morphology more challenging. This study examined 4 current methods (Friedman, corrected Friedman, Ganapathi-Iannotti, and Matsumura) and an experimental scapular border-derived coordinate system method, to compare measurement inconsistencies between methods and reference systems and assess the impact of glenoid deformity on measured glenoid version.

Methods

Three-dimensional scapulae were created from computed tomography (CT) scans of 74 shoulders that had undergone arthroplasty (28 A2, 22 B2, 10 B3, and 14 C glenoids) and 34 shoulders that had not undergone arthroplasty. Glenoid version measurements were made in Mimics using the 4 methods. For the experimental method, scapulae were reconstructed, and 3 orthogonal global coordinate planes (GCPs) were derived from the medial and lateral borders. Version was measured as the angle between the sagittal reference plane and an anterior-posterior glenoid vector. The intraclass correlation coefficient (ICC) was calculated for the Friedman and corrected Friedman methods. Inconsistencies were assessed for all methods using the interquartile range, mean and standard deviation, and repeated-measures analysis of variance. Concordance correlation coefficients (CCCs) were calculated to assess agreement among the methods.

Results

Scapular plane-based methods (experimental, Friedman, and corrected Friedman) yielded an average version between -10° and -12°, with average measurement differences among these methods of <2°. Vault methods (Ganapathi-Iannotti and Matsumura) overestimated or underestimated version by an average of 5° to 7° compared with scapular plane-based methods, and showed significant differences of >12° when compared with each other. Scapular plane-based methods maintained consistency with increasing deformity.

Conclusions

The other methods of version measurement using the scapular planes as the reference were highly comparable with the corrected Friedman method. However, when the reference plane was the glenoid vault, version measurements were inconsistent with scapular plane-based methods, which is attributed to differences in the reference systems. In surgical planning, the coordinate system utilized will impact version measurements, which can result in variations in the planned surgical solutions. Additionally, as glenoid deformity increases, this variation resulting from the utilization of different coordinate systems is magnified.

Biomechanical Analysis of Posterior Open-Wedge Osteotomy and Glenoid Concavity Reconstruction Using an Implant-Free, J-Shaped Iliac Crest Bone Graft

BACKGROUND

Posterior open-wedge osteotomy and glenoid reconstruction using a J-shaped iliac crest bone graft showed promising clinical results for the treatment of posterior instability with excessive glenoid retroversion and posteroinferior glenoid deficiency.

PURPOSE

To evaluate the biomechanical performance of the posterior J-shaped graft to restore glenoid retroversion and posteroinferior deficiency in a cadaveric shoulder instability model.

STUDY DESIGN

Controlled laboratory study.

METHODS

A posterior glenoid open-wedge osteotomy was performed in 6 fresh-frozen shoulders, allowing the glenoid retroversion to be set at 0°, 10°, and 20°. At each of these 3 preset angles of glenoid retroversion, the following conditions were simulated: (1) intact joint, (2) posterior Bankart lesion, (3) 20% posteroinferior glenoid deficiency, and (4) posterior J-shaped graft (at 0° of retroversion). With the humerus in the Jerk position (60° of glenohumeral anteflexion, 60° of internal rotation), stability was evaluated by measuring posterior humeral head (HH) translation (in mm) and peak translational force (in N) to translate the HH over 25% of the glenoid width. Glenohumeral contact patterns were measured using pressure-sensitive sensors. Fixation of the posterior J-graft was analyzed by recording graft micromovements during 3000 cycles of 5-mm anteroposterior HH translations.

RESULTS

Reconstructing the glenoid with a posterior J-graft to 0° of retroversion significantly increased stability compared with a posterior Bankart lesion and posteroinferior glenoid deficiency in all 3 preset degrees of retroversion (P < .05). There was no significant difference in joint stability comparing the posterior J-graft with an intact joint at 0° of retroversion. The posterior J-graft restored mean contact area and contact pressure comparable with that of the intact condition with 0° of retroversion (222 vs 223 mm2, P = .980; and 0.450 vs 0.550 MPa, P = .203). The mean total graft displacement after 3000 cycles of loading was 43 ± 84 µm, and the mean maximal mediolateral graft bending was 508 ± 488 µm.

CONCLUSION

Biomechanical analysis of the posterior J-graft demonstrated reliable restoration of initial glenohumeral joint stability, normalization of contact patterns comparable with that of an intact shoulder joint with neutral retroversion, and secure initial graft fixation in the cadaveric model.

CLINICAL RELEVANCE

This study confirms that the posterior J-graft can restore stability and glenohumeral loading conditions comparable with those of an intact shoulder.

How to Fashion the Bone Block for Reconstruction of the Glenoid in Anterior and Posterior Instability

BACKGROUND

Glenoid restoration techniques to address glenohumeral instability-induced anterior and posterior glenoid bone loss (AGBL and PGBL) often require reconstruction, but best-fit bone block (BFBB) modeling has not been developed.

PURPOSE

To provide glenoid bony reconstruction models for anterior and posterior instability of the shoulder using a bone loss instability cohort with high-fidelity 3-dimensional (3D) imaging.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

We reviewed consecutive patients indicated for operative stabilization who had posterior glenohumeral instability and suspected GBL who underwent 2-dimensional (2D) computed tomography (CT). Patients were matched by sex, laterality, and age to patients who underwent operative stabilization of anterior glenohumeral instability. Mimics software was used to convert all 2D CT scans into 3D models of the scapula. A BFBB model was designed to digitally reconstruct GBL and was used to predict the amount, anatomic configuration, and fixation configuration of bony reconstruction required in AGBL and PGBL.

RESULTS

The study included 30 patients with posterior instability and 30 patients with anterior instability; the participants' mean ± SD age was 28.8 ± 8.15 years (range, 16.0-51.0 years). Mean surface area of AGBL was 24.9% ± 7.7% (range, 14.7%-39.1%). Mean BFBB dimensions to reconstruct the anterior glenoid were determined to be a superior-inferior length of 23.9 ± 4.2 mm, anterior-posterior width of 6.4 ± 2.4 mm, and height of 1 cm. Mean angle of AGBL bone block interface relative to glenoid to reconstruct the native concavity was 79.4°± 5.9°. For PGBL, the mean surface area was 9.2% ± 5.6% (range, 3.0%-26.3%). Mean BFBB dimensions to reconstruct the posterior glenoid were a superior-inferior length of 21.9 ± 3.4 mm, width of 4.5 ± 2.3 mm, and height of 1 cm. The mean angle of PGBL bone block interface relative to the glenoid to reconstruct the native concavity was 38.6°± 14.3°. Orientation relative to the vertical glenoid axis was 77.2°± 13.8° in anterior reconstructions versus 105.9°± 10.9° in posterior reconstructions.

CONCLUSION

Patients with anterior instability required a more rectangular BFBB with a bone block-glenoid interface angle of 79°, whereas patients with posterior instability required a more trapezoidal, obtusely oriented BFBB with a bone block-glenoid interface angle of 39°. BFBBs for either AGBL or PGBL can be effectively designed, and their size and/or shape can be predicted based on approximate percentage of GBL.

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.

The Effect of Glenoid Version on Glenohumeral Instability

In recent years, an appreciation for the dynamic relationship between glenoid and humeral-sided bone loss and its importance to the pathomechanics of glenohumeral instability has substantially affected modern treatment algorithms. However, comparatively less attention has been paid to the influence of glenoid version on glenohumeral instability. Limited biomechanical data suggest that alterations in glenoid version may affect the forces necessary to destabilize the glenohumeral joint. However, this phenomenon has not been consistently corroborated by the results of clinical studies. Although increased glenoid retroversion may represent an independent risk factor for posterior glenohumeral instability, this relationship has not been reliably observed in the setting of anterior glenohumeral instability. Similarly, the effect of glenoid version on the failure rates of surgical stabilization procedures remains poorly understood.

Beach-Chair Versus Lateral Decubitus Positioning for Arthroscopic Posterior Shoulder Labral Repair: A Retrospective Comparison of Clinical and Patient-Reported Outcomes

BACKGROUND

Both beach-chair and lateral decubitus patient positioning are often utilized for shoulder arthroscopy, with each offering its unique advantages and disadvantages. The surgical position is often selected according to each surgeon's preference, with no clear superiority of one position over the other.

PURPOSE/HYPOTHESIS

The purpose was to compare clinical and patient-reported outcomes between patients who underwent arthroscopic posterior labral repair in the beach-chair versus the lateral decubitus position. We hypothesized that patient positioning would not affect clinical and patient-reported outcomes.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A list of all patients diagnosed with the Current Procedural Terminology codes 29806 and 29807 between 2015 and 2019 was obtained from the medical records. Patients were only included if arthroscopic posterior labral repair with or without concomitant superior labral anterior to posterior repair was confirmed. Data collected for eligible patients included the number of anchors used, perioperative and postoperative complications, redislocations, subjective instability, reoperation, and revision. Patients were also contacted to complete several patient-reported outcome surveys. Preoperative data, perioperative data, and postoperative outcomes were compared between patients who underwent surgery in the beach-chair versus lateral decubitus position.

RESULTS

Overall, 126 patients were included-69 patients underwent surgery in the lateral decubitus position and 57 in the beach-chair position-with a mean follow-up of 2.6 ± 1.7 years. There were no significant pre- or perioperative differences between groups. Rates of postoperative dislocations, subjective instability, reoperations, revisions, all complications, and return to sports rates also did not differ between groups (all, P > .05). Finally, there was no difference between groups regarding postoperative pain, function, and subjective instability scores (all, P > .05). Results of the multivariate regression analysis showed that increased age was a weak independent risk factor for subjective recurrent posterior shoulder instability (odds ratio, 1.04; P = .036).

CONCLUSION

Surgical positioning for arthroscopic posterior shoulder labral repair did not affect postoperative clinical and patient-reported outcomes. Both beach-chair and lateral decubitus position provided good outcomes for posterior shoulder labral repair, with an overall recurrence rate of 8.7%. Increased age was a weak independent risk factor for subjective recurrent instability.

Anterior and Posterior Glenoid Bone Loss In Patients Receiving Surgery for Glenohumeral Instability Is Not the Same: A Comparative 3-Dimensional Imaging Analysis

Background

Methods

Results

Conclusion

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

Background

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

Methods

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

Results

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

Conclusion

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

High Incidence of Anterior Shoulder Pain in Young Athletes Undergoing Arthroscopic Posterior Labral Repair for Posterior Shoulder Instability

Purpose

The purposes of this study were to determine the incidence of anterior shoulder pain in young athletes undergoing arthroscopic posterior labral repair for symptomatic unidirectional posterior shoulder instability and in patients with preoperative anterior shoulder pain treated without biceps tenodesis at the time of arthroscopic posterior labral repair who underwent a revision biceps tenodesis procedure at short-term follow up.

Methods

A retrospective review was performed at a single institution over a 24-month period. The study included young patients who underwent an arthroscopic posterior labral repair for symptomatic unidirectional posterior shoulder instability. The electronic medical record, magnetic resonance arthrograms, and arthroscopic images were reviewed to exclude patients with posterior labral tears with anterior labral tear or SLAP (superior labrum anterior-to-posterior) tear extension on advanced imaging and arthroscopic examination. Data collected included the presence of preoperative tenderness to palpation of the biceps tendon in the groove, the results of a preoperative Speed test, postoperative Subjective Shoulder Value, the presence of postoperative anterior shoulder pain, and the need for a secondary biceps tenodesis.

Results

We identified 65 patients who underwent arthroscopic labral repair for posterior shoulder instability. From this cohort, 26 patients with symptomatic unidirectional posterior shoulder instability underwent an arthroscopic posterior labral repair. The incidence of preoperative anterior shoulder pain with Zone 2 biceps groove tenderness and a positive Speed test was identified in 20 of 26 patients (76.9%). Of 26 patients, 5 (19%) had concomitant biceps tenodesis. The median postoperative Subjective Shoulder Value was 80 (interquartile range, 60-90) at median follow-up of 2.1 years. Of the 20 patients with preoperative anterior shoulder pain, 8 of 20 (40%) reported persistent anterior pain. One patient (4.7%) underwent a secondary biceps tenodesis.

Conclusions

There is a high incidence of anterior shoulder pain and Zone 2 biceps groove tenderness in patients undergoing isolated arthroscopic posterior labral repair for unidirectional posterior shoulder instability. At short-term follow-up, few patients required a secondary biceps tenodesis procedure; however, 30% of patients had persistent anterior shoulder pain.

Level of Evidence

Level IV, retrospective diagnostic case series.

Posterior Open-wedge Osteotomy and Glenoid Concavity Reconstruction Using an Implant-free, J-shaped Iliac Crest Bone Graft in Atraumatic Posterior Instability with Pathologic Glenoid Retroversion and Dysplasia: A Preliminary Report

BACKGROUND

Atraumatic posterior shoulder instability in patients with pathologic glenoid retroversion and dysplasia is an unsolved problem in shoulder surgery.

QUESTIONS/PURPOSES

In a preliminary study of a small group of patients with atraumatic posterior shoulder instability associated with glenoid retroversion ≥ 15° and glenoid dysplasia who underwent posterior open-wedge osteotomy and glenoid concavity reconstruction using an implant-free, J-shaped iliac crest bone graft, we asked: (1) What proportion of the patients had persistent apprehension? (2) What were the improvements in patient-reported shoulder scores? (3) What were the radiographic findings at short-term follow-up?

METHODS

Between 2016 and 2018, we treated seven patients for atraumatic posterior shoulder instability. We performed this intervention when posterior shoulder instability symptoms were unresponsive to physiotherapy for at least 6 months and when it was associated with glenoid retroversion ≥ 15° and dysplasia of the posteroinferior glenoid. All seven patients had a follow-up examination at a minimum of 2 years. The median (range) age at surgery was 27 years (16 to 45) and the median follow-up was 2.3 years (2 to 3). Apprehension was assessed by a positive posterior apprehension and/or posterior jerk test. Patient-reported shoulder scores were obtained and included the subjective shoulder value, obtained by chart review (and scored with 100% representing a normal shoulder; minimum clinically important difference [MCID] 12%), and the Constant pain scale score (with 15 points representing no pain; MCID 1.5 points). Radiographic measurements included glenohumeral arthropathy and posterior humeral head subluxation, bone graft union, correction of glenoid retroversion and glenoid concavity depth, as well as augmentation of glenoid surface area. All endpoints were assessed by individuals not involved in patient care.

RESULTS

In four of seven patients, posterior apprehension was positive, but none reported resubluxation. The preoperative subjective shoulder value (median [range] 40% [30% to 80%]) and Constant pain scale score (median 7 points [3 to 13]) were improved at latest follow-up (median subjective shoulder value 90% [70% to 100%]; p = 0.02; median Constant pain scale score 15 points [10 to 15]; p = 0.03). Posterior glenoid cartilage erosion was present in four patients (all four had Walch Type B1 glenoids) preoperatively and showed no progression until the final follow-up examination. The median (range) humeral head subluxation index decreased from 69% (54% to 85%) preoperatively to 55% (46% to 67%) postoperatively (p = 0.02), and in two of four patients with preoperative humeral head subluxation (> 65% subluxation), it was reversed to a centered humeral head. CT images showed union in all implant-free, J-shaped iliac crest bone grafts. The median preoperative retroversion was corrected from 16° (15° to 25°) to 0° postoperatively (-5° to 6°; p = 0.02), the median glenoid concavity depth was reconstructed from 0.3 mm (-0.7 to 1.6) preoperatively to 1.2 mm (1.1 to 3.1) postoperatively (p = 0.02), and the median preoperative glenoid surface area was increased by 20% (p = 0.02). No intraoperative or postoperative complications were recorded, and no reoperation was performed or is planned.

CONCLUSION

In this small, retrospective series of patients treated by experienced shoulder surgeons, a posterior J-bone graft procedure was able to reconstruct posterior glenoid morphology, correct glenoid retroversion, and improve posterior shoulder instability associated with pathologic glenoid retroversion and dysplasia, although four of seven patients had persistent posterior apprehension. Although no patients in this small series experienced complications, the size and complexity of this procedure make it likely that as more patients have it, some will develop complications; future studies will need to characterize the frequency and severity of those complications, and we recommend that this procedure be done only by experienced shoulder surgeons. The early results in these seven patients justify further study of this procedure for the proposed indication, but longer term follow-up is necessary to continue to assess whether it is advantageous to combine the reconstruction of posterior glenoid concavity with correction of pathological glenoid retroversion and increasing glenoid surface compared with traditional surgical techniques such as the posterior opening wedge osteotomy or simple posterior bone block procedures.

LEVEL OF EVIDENCE

Level IV, therapeutic study.

Rehabilitation Following Posterior Shoulder Stabilization

Posterior shoulder instability has been noted in recent reports to occur at a higher prevalence than originally believed, with many cases occurring in active populations. In most cases, primary surgical treatment for posterior shoulder instability-a posterior labral repair-is indicated for those patients who have failed conservative management and demonstrate persistent functional limitations. In order to optimize surgical success and return to a prior level of function, a comprehensive and focused rehabilitation program is crucial. Currently, there is a limited amount of literature focusing on rehabilitation after surgery for posterior instability. Therefore, the purpose of this clinical commentary is to present a post-surgical rehabilitation program for patients following posterior shoulder labral repair, with recommendations based upon best medical evidence.

LEVEL OF EVIDENCE

5.

Glenoid Pathology, Skeletal Immaturity, and Multiple Preoperative Instability Events Are Risk Factors for Recurrent Anterior Shoulder Instability After Arthroscopic Stabilization in Adolescent Athletes

PURPOSE

To identify risk factors for recurrent shoulder instability after arthroscopic stabilization in adolescent athletes.

METHODS

A retrospective case-control study was undertaken of all patients younger than 18 years undergoing arthroscopic shoulder stabilization for anterior instability between 2009 and 2016. Two patient cohorts were identified: (1) patients with recurrent instability (frank dislocations or subluxations) after arthroscopic stabilization and (2) an age- and sex-matched cohort of patients with no recurrent instability at a minimum of 2 years' follow-up from index surgery. Patient demographic, injury, radiographic, and surgical variables were recorded. Variables with P < .10 on univariate analysis were entered into a binary logistic multivariate regression analysis.

RESULTS

We identified 35 patients (20.5%) in whom arthroscopic stabilization failed at a mean of 1.2 ± 1.0 years after their index surgical procedure. A separate age- and sex-matched cohort of 35 patients with no evidence of recurrent instability was identified (mean follow-up, 5.4 ± 2.0 years; minimum follow-up, 2 years). Univariate analysis identified increased glenoid bone loss (P = .039), decreased glenoid retroversion (P = .024), and more than 1 instability event prior to surgery (P = .017) as significant risk factors for recurrent instability. Multivariate regression analysis revealed that glenoid retroversion less than 6°, skeletal immaturity, and more than 1 prior instability event significantly and independently predicted future recurrence. The risk of recurrence after arthroscopic stabilization was increased by 3 times in patients with 2 risk factors and by 4 times in patients with all 3 risk factors.

CONCLUSIONS

Anterior glenoid bone loss, glenoid version, skeletal immaturity, and multiple preoperative instability events are risk factors for failed arthroscopic stabilization in adolescent athletes with anterior instability.

LEVEL OF EVIDENCE

Level III, case-control study.

Decreased Glenoid Retroversion Is a Risk Factor for Failure of Primary Arthroscopic Bankart Repair in Individuals With Subcritical Bone Loss Versus No Bone Loss

PURPOSE

To determine whether glenoid retroversion is an independent risk factor for failure after arthroscopic Bankart repair.

METHODS

This was a retrospective review of patients with a minimum 2-year follow-up. In part 1 of the study, individuals with no glenoid bone loss on magnetic resonance imaging (MRI) and who failed arthroscopic Bankart repair (cases) were compared with individuals who did not fail Bankart repair (controls). In part 2 of the study, cases with subcritical (<20%) glenoid bone loss as measured on sagittal T1 MRI sequences who failed arthroscopic Bankart repair were compared with controls who did not. For each part of the study, glenoid version was measured using axial T2 MRI sequences. Positive angular measurements were designated to represent glenoid anteversion, whereas negative measurements were designated to represent glenoid retroversion. Independent t tests were conducted to determine the association between glenoid version and failure after arthroscopic Bankart repair.

RESULTS

There were 20 cases and 40 controls in part 1 of the study. In part 2, there were 19 cases and 21 controls. There was no difference in baseline characteristics between cases and controls. Among individuals with no glenoid bone loss, there was no difference in glenoid version between cases and controls (cases: 6.0° ± 8.1° vs controls: 5.1° ± 7.8°, P = .22). Among individuals with subcritical bone loss, cases (3.8° ± 4.4°) were associated with significantly less mean retroversion compared with controls (7.1° ± 2.8°, P = .0085). Decreased retroversion (odds ratio 1.34; 95% confidence interval 1.05-1.72, P = 20) was a significant independent predictor of failure using univariable logistic regression.

CONCLUSIONS

While glenoid retroversion is not associated with failure after arthroscopic Bankart repair in individuals with no glenoid bone loss, decreased retroversion is associated with failure in individuals with subcritical bone loss.

LEVEL OF EVIDENCE

Level 3: Retrospective review.

Does the posterior glenoid osteotomy reduce the rate of recurrence in patients with posterior shoulder instability - A systematic review

BACKGROUND

Posterior shoulder instability (PSI) is becoming an increasingly recognised condition. A number of different treatment modalities exist to treat PSI including arthroscopic or open surgeries when non-operative treatment has failed. The primary aim of this systematic review was to analyse the rate of recurrent instability after posterior glenoid osteotomy (PGO) for recurrent PSI, while secondary aim was to identify complication rate and the amount of retroversion correction.

PATIENTS AND METHODS

A review of the online databases MEDLINE and Embase was conducted on 1 November 2019 according to PRISMA guidelines. The review was registered prospectively in the PROSPERO database (Registration No. CRD42020161984). Clinical studies reporting either the recurrence rate, complications or amount of retroversion correction after PGO for PSI were included. The studies were appraised using the Methodological Index for Non-Randomized Studies (MINORS) tool.

RESULTS

The search strategy identified 9 studies eligible for inclusion. Of the 9 studies, 4 showed an improvement in retroversion with a mean change in retroversion of 10^o. All 9 studies reported on recurrence rate with an overall rate of 22%. Complications were discussed in only 7 of the studies with overall rate of 18.3%. The most common complication reported in the studies were degenerative changes of the glenohumeral joint (7.3%) and iatrogenic fractures (5.5%).

CONCLUSION

PGO is a viable option in patients with recurrent PSI that have increased retroversion and have failed non-operative or arthroscopic treatment. It does however carry a significant risk of complications.

LEVEL OF EVIDENCE

IV; Systematic review.

Arthroscopic Posterior Glenoid Reconstruction Using a Fresh Distal Tibia Allograft for Recurrent Posterior Instability

Posterior glenohumeral instability is a relatively uncommon cause of shoulder instability. Recurrent posterior instability with static posterior humeral head subluxation is often associated with critical glenoid bone loss. Unlike anterior instability, the amount of bone loss for posterior instability that requires surgical reconstruction remains a topic of debate. Several techniques have been described to treat critical bony defects in patients with recurrent posterior shoulder instability with the use of both autografts and allografts depending on the amount of bone loss present. Open posterior glenoid bone block procedure is associated with increased risk of complications and morbidity to the patient. As such, all-arthroscopic techniques have emerged with the advantage of allowing for the diagnosis and treatment of concomitant glenohumeral pathology and minimizing soft-tissue dissection through the posterior deltoid and rotator cuff muscles. Reported short-term outcomes of arthroscopic posterior bone block stabilization are promising; however, it remains a technically challenging procedure due to intra-articular graft insertion and subsequent fixation congruent to the posterior glenoid articular margin. We describe an all-arthroscopic technique using a fresh distal tibia allograft fixation using 2 partially threaded screws in conjunction with an arthroscopic Latarjet fixation set for a patient with recurrent posterior shoulder instability and associated glenoid bone loss.

Restoration of the Posterior Glenoid in Recurrent Posterior Shoulder Instability Using an Arthroscopically Placed Iliac Crest Bone Graft: A Computed Tomography-Based Analysis

Background

Posterior shoulder instability is uncommon, and its treatment is a challenging problem. An arthroscopically assisted technique for posterior iliac crest bone grafting (ICBG) has shown promising short- and long-term clinical results. Changes as shown on imaging scans after posterior ICBG for posterior shoulder instability have not been investigated in the recent literature.

Purpose

To evaluate changes on computed tomography (CT) after arthroscopically assisted posterior ICBG and to assess clinical outcomes.

Study Design

Case series; Level of evidence, 4.

Methods

Patients with preoperative CT scans and at least 2 postoperative CT scans with a minimum follow-up of 2 years were included in the evaluation. Of 49 initial patients, 17 (follow-up rate, 35%) met the inclusion criteria and were available for follow-up. We measured the glenoid version angle and the glenohumeral and scapulohumeral indices on the preoperative CT scans and compared them with measurements on the postoperative CT scans. Postoperatively, graft surface, resorption, and defect coverage were measured and compared with those at early follow-up (within 16 months) and final follow-up (mean ± SD, 6.6 ± 2.8 years).

Results

The mean preoperative glenoid version was -17° ± 13.5°, which was corrected to -9.9° ± 11.9° at final follow-up (P < .001). The humeral head was able to be recentered and reached normal values as indicated by the glenohumeral index (51.8% ± 6%; P = .042) and scapulohumeral index (59.6% ± 10.2%; P < .001) at final follow-up. Graft surface area decreased over the follow-up period, from 24% ± 9% of the glenoid surface at early follow-up to 17% ± 10% at final follow-up (P < .001). All clinical outcome scores had improved significantly. Progression of osteoarthritis was observed in 47% of the shoulders.

Conclusion

Arthroscopically assisted posterior ICBG restored reliable parameters as shown on CT scans, especially glenoid version and the posterior subluxation indices. Graft resorption was common and could be observed in all shoulders. Patient-reported clinical outcome scores were improved. Osteoarthritis progression in almost 50% of patients is concerning for the long-term success of this procedure.

Effect of Posterior Glenoid Bone Loss and Retroversion on Arthroscopic Posterior Glenohumeral Stabilization

BACKGROUND

Posterior glenohumeral instability is an increasingly recognized cause of shoulder instability, but little is known about the incidence or effect of posterior glenoid bone loss.

PURPOSE

To determine the incidence, characteristics, and failure rate of posterior glenoid deficiency in shoulders undergoing isolated arthroscopic posterior shoulder stabilization.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

All patients undergoing isolated posterior labral repair and glenoid-based capsulorrhaphy with suture anchors between 2008 and 2016 at a single institution were identified. Posterior bone deficiency was calculated per the best-fit circle method along the inferior two-thirds of the glenoid by 2 independent observers. Patients were divided into 2 groups: minimal (0%-13.5%) and moderate (>13.5%) posterior bone loss. The primary outcome was reoperation for any reason. The secondary outcomes were military separation and placement on permanent restricted duty attributed to the operative shoulder.

RESULTS

A total of 66 shoulders met the inclusion criteria, with 10 going on to reoperation after a median follow-up of 16 months (range, 14-144 months). Of the total shoulders, 86% (57/66) had ≤13.5% bone loss and 14% (9/66) had >13.5%. Patients with moderate posterior glenoid bone loss had significantly greater retroversion (-11.5° vs -4.3°; P = .01). Clinical failure requiring reoperation was seen in 10.5% of patients in the minimal bone deficiency group and 44.4% in the moderate group (P = .024). There was no difference between groups in rate of military separation or restricted duty. Patients with moderate posterior glenoid bone deficiency were more likely to be experiencing instability instead of pain on initial presentation (P < .001), were more likely to have a positive Jerk test result (P = .05), and had increased glenoid retroversion (P = .01).

CONCLUSION

In shoulders with moderate glenoid bone deficiency (>13.5%) and increased glenoid retroversion, posterior capsulolabral repair alone may result in higher reoperation rates than in shoulders without bone deficiency.

Glenoid version is associated with different labrum tear patterns in shoulder instability

BACKGROUND

Previous studies have evaluated glenoid version as a risk factor for anterior and posterior shoulder instability. However, the association of glenoid version with combined anterior-inferior-posterior (>180°) labrum injuries is unknown. The purpose of the present study was to investigate various parameters of glenoid morphology, including version, in >180° labral tears and to compare these values with isolated anterior and isolated posterior tears.

METHODS

Magnetic resonance imaging studies from a consecutive series of shoulder instability patients were reviewed by 3 independent observers to measure the parameters of glenoid morphology including superior-inferior and anterior-posterior diameter, diameter ratio, glenoid version using the glenoid vault method, and percentage of glenoid bone loss using the best-fit circle method. These parameters were compared between patients with anterior (group 1), posterior (group 2), and >180° labral tears (group 3). Interobserver reliability coefficients were calculated for all measurements assessed.

RESULTS

There were statistically significant differences for all group comparisons regarding the glenoid version, with group 2 having the most retroversion (19.9° ± 4.71°) followed by group 3 (14.21° ± 4.59°) and group 1 (11.24° ± 5.3°). Group 3 showed the lowest amount of glenoid bone loss; however, the group differences did not reach statistical significance. There was also no statistically significant group difference for the other measured parameters. Interobserver reliability was in the good to excellent range for all measurements.

CONCLUSIONS

Combined anterior-inferior-posterior labral tears are associated with an increased amount of glenoid retroversion compared with isolated anterior labral tears. Isolated posterior labral tears have the largest amount of glenoid retroversion of all tear patterns.

Posterior Shoulder Instability Classification, Assessment, and Management: An International Delphi Study

OBJECTIVE

To reach consensus among international shoulder experts on the most appropriate assessment and management strategies for posterior shoulder instability (PSI).

DESIGN

Delphi.

METHODS

In phase 1 of the study, we reviewed the literature, generated the Delphi items, created the survey, and identified clinical experts. In phase 2 of the study, clinical shoulder experts (physical therapists, orthopaedic surgeons, sports medicine physicians, and researchers) participated in a 3-round e-Delphi survey. For consensus, we required a minimum of 70% agreement per round. Descriptive statistics were used to present the characteristics of the respondents, the response rate of the experts in each round, and the consensus for PSI classification, assessment, and management.

RESULTS

Round 3 was completed by 47 individuals from 5 different countries. The response rate ranged from 57/70 (81%) to 47/50 (94%) per round. Respondents agreed on 3 subgroups to define PSI: traumatic (100% agreement), microtraumatic (98% agreement), and atraumatic (98% agreement).

CONCLUSION

International shoulder experts agreed that the clinical presentation, management strategy, and outcome expectations differ for traumatic, microtraumatic, and atraumatic PSI. Their recommendations provide a framework for managing these subgroups, with additional consideration of sport and work participation and subsequent risks. J Orthop Sports Phys Ther 2020;50(7):373-380. Epub 29 Apr 2020. doi:10.2519/jospt.2020.9225.

Glenoid retroversion is an important factor for humeral head centration and the biomechanics of posterior shoulder stability

PURPOSE

Glenoid retroversion is a known independent risk factor for recurrent posterior instability. The purpose was to investigate progressive angles of glenoid retroversion and their influence on humeral head centration and posterior translation with intact, detached, and repaired posterior labrum in a cadaveric human shoulder model.

METHODS

A total of 10 fresh-frozen human cadaveric shoulders were investigated for this study. After CT- canning, the glenoids were aligned parallel to the floor, with the capsule intact, and the humerus was fixed in 60° of abduction and neutral rotation. Version of the glenoid was created after wedge resection from posterior and fixed with an external fixator throughout the testing. Specimens underwent three conditions: intact, detached, and repaired posterior labrum, while version of the glenoid was set from + 5° anteversion to - 25° retroversion by 5° increments. Within the biomechanical setup, the glenohumeral joint was axially loaded (22 N) to center the joint. At 0° of glenoid version and intact labrum, the initial position was used as baseline and served as point zero of centerization. After cyclic preloading, posterior translation force (20 N) was then applied by a material testing machine, while start and endpoints of the scapula placed on an X-Y table were measured.

RESULTS

The decentralization of the humeral head at glenoid version angles of 5°, 10°, 15°, and 20° of retroversion and 5° of anteversion was significantly different (P < 0.001). Every increment of 5° of retroversion led to an additional decentralization of the humeral head overall by (average ± SD) 2.0 mm ± 0.3 in the intact and 2.0 mm ± 0.7 in the detached labrum condition. The repaired showed significantly lower posterior translation compared to the intact condition at 10° (P = 0.012) and 15° (P < 0.01) of retroversion. In addition, CT measured parameters (depth, diameter, and native version) of the glenoid showed no correlation with angle of dislocation of each specimen.

CONCLUSION

Bony alignment in terms of glenoid retroversion angle plays an important role in joint centration and posterior translation, especially in retroversion angles greater than 10°. Isolated posterior labrum repair has a significant effect on posterior translation in glenoid retroversion angles of 5° and 10°. Bony correction of glenoid version may be considered to address posterior shoulder instability with retroversion > 15°.

Characterization of Posterior Glenoid Bone Loss Morphology in Patients With Posterior Shoulder Instability

PURPOSE

To systemically describe posterior bone defects in the setting of posterior shoulder instability based on several parameters, including surface area, slope and version, defect height from the base of the glenoid, and extent of bone loss at equal intervals along the long axis of the fossa.

METHODS

A total of 40 young, active individuals with recurrent posterior shoulder instability and a bony injury confirmed on either computed tomography (n = 18; mean age, 26.3 ± 4.0 years) or magnetic resonance imaging (n = 22; mean age, 20.0 ± 4.9 years) were identified. The posterior glenoid bone defect was characterized using the following measures: (1) percentage of bone loss, (2) glenoid vault version, (3) slope of the posterior defect relative to the glenoid surface, (4) superior-inferior length of the defect, and (5) anterior-posterior width of the defect at 5 intervals along the glenoid fossa.

RESULTS

The mean age of the 40 patients was 22.9 ± 5.5 years (range, 14.9-35.5 years). The mean surface area of glenoid bone loss was 9.7% ± 4.7%. Glenoid version measured at 5 equal intervals along the inferior two-thirds of the glenoid was 12.8° ± 4.9°, 11.9° ± 5.0°, 10.1° ± 6.3°, 10.5° ± 6.5°, and 8.7° ± 7.2° from superior to inferior. The mean slope of the posterior defect relative to the glenoid fossa was 26.8° ± 11.5°. The mean superior-inferior height of the bony defect was 21.9 ± 0.4 mm. The anterior-posterior sloped width of the defect at 5 equal intervals along the glenoid fossa was 0.9 ± 1.5 mm, 2.8 ± 2.4 mm, 4.0 ± 1.7 mm, 4.0 ± 2.1 mm, and 2.9 ± 2.6 mm from superior to inferior. Low-grade (<10%) bone loss was diagnosed in most shoulders (23 of 40 evaluated), whereas 15 had moderate bone loss (10% to <20%) and 2 had high-grade bone loss (≥20%).

CONCLUSIONS

Posterior glenoid bone loss is characterized by a loss of posterior bony concavity, increased slope from anterior to posterior, and increased posterior version. The most anterior-posterior sloped width was quantified at the third and fourth intervals of 5 equal intervals from superior to inferior. This study highlights that patients with posterior instability have bone loss that is sloped relative to the glenoid fossa and suggests that management must be appropriately tailored given the distinctiveness of posterior bone loss.

LEVEL OF EVIDENCE

Level IV, case series.

Editorial Commentary: Open Posterior Shoulder Stabilization-When Is It Needed? Glenoid Bone Loss Patterns Are Not Created Equal

Posterior shoulder instability remains a poorly understood pathologic entity. Our current treatment algorithm of simple posterior shoulder instability is fairly straightforward, with most patients receiving arthroscopic capsulorrhaphy with labral repair. However, in those with a failed arthroscopic intervention and/or with bony pathology, the optimal treatment is much less clear. As we move forward to evaluate how to optimally treat these patients, it will be critical to better understand the bony pathologies, including those with true posterior glenoid bone loss versus glenoid retroversion. Using novel methods to identify, measure, and quantify the different glenoid morphologies will be the foundation for improving the treatment of these complex and poorly understood pathologies.

Posterior Acromial Morphology Is Significantly Associated with Posterior Shoulder Instability

BACKGROUND

The purpose of this paper was to determine whether acromial morphology influences anteroposterior shoulder stability. We hypothesized that a more horizontal and higher position of the acromion in the sagittal plane would be associated with posterior instability.

METHODS

In this retrospective study, patients with unidirectional posterior instability were age and sex-matched to a cohort of patients with unidirectional anterior instability. Both cohorts were compared with a control group of patients with no instability and no degenerative glenohumeral (rotator cuff and/or joint surface) or acromial changes. Measurements on radiographs included posterior acromial tilt, anterior and posterior acromial coverage (AAC and PAC), posterior acromial height (PAH), and the critical shoulder angle (CSA).

RESULTS

The number of patients enrolled in each instability group was 41, based on a priori power analysis. The control group consisted of 53 shoulders. Of the measured anatomic factors, PAH showed the most significant association with posterior instability (odds ratio [OR] = 1.8; p < 0.001) in the logistic regression model. PAH was significantly greater in the posterior instability group compared with the anterior instability group (30.9 versus 19.5 mm; p < 0.001). With a cutoff value of PAH of 23 mm, the OR for posterior instability was 39. Shoulders with posterior instability were also significantly different from normal shoulders with regard to PAH (p < 0.001), AAC (p < 0.001), and PAC (p < 0.001) whereas, in the shoulders with anterior instability, all of these values except the AAC (p = 0.011) did not differ from those of normal shoulders.

CONCLUSIONS

Specific acromial morphology is significantly associated with the direction of glenohumeral instability. In shoulders with posterior instability, the acromion is situated higher and is oriented more horizontally in the sagittal plane than in normal shoulders and those with anterior instability; this acromial position may provide less osseous restraint against posterior humeral head translation. A steep "Swiss chalet roof-type" acromion virtually excluded recurrent posterior instability in an albeit relatively small cohort of patients. Additional investigation is needed to determine the relevance of these findings for future treatment.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

ACR Appropriateness Criteria® Shoulder Pain-Traumatic

Traumatic shoulder pain is pain directly attributed to a traumatic event, either acute or chronic. This pain may be the result of either fracture (the clavicle, scapula, or proximal humerus) or soft-tissue injury (most commonly of the rotator cuff, acromioclavicular ligaments, or labroligamentous complex). Imaging assessment of traumatic shoulder pain begins with conventional radiography and, depending on physical examination findings, will require MRI or MR arthrography for assessment of soft-tissue injuries and CT for delineation of fracture planes. Ultrasound excels in assessment of rotator cuff injuries but has limited usefulness for assessment of the deep soft-tissues. CT angiography and conventional arteriography are helpful for assessment of vascular injury, and bone scintigraphy can be used in assessment of complex regional pain syndrome after traumatic shoulder injury. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Patient Positioning in Arthroscopic Management of Posterior-Inferior Shoulder Instability: A Systematic Review Comparing Beach Chair and Lateral Decubitus Approaches

PURPOSE

To analyze the available literature pertaining to clinical outcomes and complications of posterior-inferior shoulder stabilization performed arthroscopically in either the beach chair (BC) or lateral decubitus (LD) position.

METHODS

According to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), 3 databases (PubMed, EMBASE, and Medline) were searched up to January 2018 for English-language studies on posterior shoulder instability. Descriptive statistics are presented. The Methodological Index for Non-Randomized Studies (MINORS) scale was used to assess quality.

RESULTS

Twenty-five studies were included, examining 1,085 patients (n = 140 BC; n = 945 LD), of mean age 25.0 years, 27.1% female, and mean 3.1 years of follow-up. MINORS scores for BC and LD were 11.2 and 9.8, respectively. Regardless of positioning, patients did not differ across numerous outcomes and various surgical factors (e.g., number of portals, anchors, anchor types, concomitant pathology, or postoperative rehabilitation protocol). Postoperative patient satisfaction ranged from 85% to 87.5% and 93% to 100% for patients treated in BC and LD positions, respectively. Although not reported for BC, overall and preinjury return-to-play (RTP) rates in LD patients ranged from 72% to 100% and 55% to 100%, respectively, returning from 3 to 7.6 months postoperatively. Failure rates in the BC and LD positions ranged from 0% to 9.4% and 0% to 29%, respectively. There were no differences in reported incidences of neuropraxia, stroke, nonfatal pulmonary embolus, vision loss, cardiac arrest, or other positioning-related complications.

CONCLUSIONS

Arthroscopic management of posterior-inferior shoulder instability has a successful track record and minimal complication profile. Although patient positioning appears to influence results, with those treated in the LD position experiencing marginally higher patient satisfaction and failure rates, the current data prevent any conclusions being made regarding the superiority of one approach over another. As the clinical relevance of patient positioning remains to be determined, larger, higher-level study designs with long-term follow-up are required.

LEVEL OF EVIDENCE

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

The Influence of Bone Loss on Glenoid Version Measurement: A Computer-Modeled Cadaveric Analysis

PURPOSE

To characterize how increasing computed tomography (CT)-quantified glenoid bone loss influences measured version.

METHODS

Six embalmed cadaveric shoulders were used for this study. Glenoid bone defects were computer modeled in cadaveric shoulders; CT images were obtained and segmented using OsiriX software, creating 3-dimensional en face glenoids. Glenoid defects were made on CT images of intact glenoids superimposed with a glenoid clock face viewed en face to simulate anterior and posterior bone loss. Bony defects in various positions comprising 3%, 9.5%, and 19.5% were created posteriorly. Best-fit circles were superimposed to represent 10% and 25% defects anteriorly. Version was measured using the Friedman method.

RESULTS

The average glenoid version measured 4° of retroversion, 2° after 10% anterior bone loss, and neutral version in the 25% bone loss group. Version was significantly altered when we compared intact glenoids versus 10% and 25% anterior glenoid bone loss (P < .001). Increasing from 10% to 25% bone loss showed a significant difference in measured version (P = .025). Posterior defects from the 6:30 to 8:30 clock-face position averaged 4.6° of retroversion; from the 6:30 to 9:30 clock-face position, 6.2° of retroversion; and from the 6:30 to 10:30 clock-face position, 8.7° of retroversion. When comparing glenoid defects at the 6:30 to 8:30 clock-face position with those involving the 6:30 to 9:30 and 6:30 to 10:30 clock-face positions (P < .001), a 1° correction may be used for every 5% of bone loss to account for version changes seen with bone loss.

CONCLUSIONS

In this cadaveric analysis, glenoid version was altered in the setting of increasing posterior and anterior bone loss. A correction factor may be considered to account for this. When comparing glenoid defects at the 6:30 to 8:30 clock-face position with those involving the 6:30 to 9:30 and 6:30 to 10:30 clock-face positions (P < .001), a 1° correction may be used for every 5% of bone loss to account for version changes seen with bone loss.

CLINICAL RELEVANCE

This cadaveric study shows that glenoid bone loss alters glenoid version, as measured by CT, in a meaningful way. This information is important in managing anterior and posterior shoulder instability, and correction of measured version should be considered in this setting to provide an accurate and comprehensive evaluation.

Editorial Commentary: Bone Loss in Shoulder Instability Occurs in 3 Dimensions

The continued debate regarding the appropriate threshold to consider performing bony stabilization procedures in the treatment of shoulder instability has contributed to a recent boom of new research in this area. The contribution of both glenoid bone loss and version in predicting potential clinical failure after soft tissue stabilization is one of those topics. The authors of the featured study demonstrate the relationship between measured glenoid version and bone loss, which can assist us in our clinical decision making. To date, most measures of glenoid version have been reported based on analysis of 2 dimensions. However, with 2-dimensional analysis, bone loss may result in potentially errant measurement of version and require subsequent correction. Moreover, 3-dimensional analysis could result in a more nuanced understanding of the complexities of glenoid pathologic study in patients with shoulder instability.

Evidence-Based Review of Clinical Diagnostic Tests and Predictive Clinical Tests That Evaluate Response to Conservative Rehabilitation for Posterior Glenohumeral Instability: A Systematic Review

Context:

Posterior glenohumeral instability is poorly understood and can be challenging to recognize and evaluate. Using evidence-based clinical and predictive tests can assist clinicians in appropriate assessment and management.

Objective:

To review evidence-based clinical diagnostic tests for posterior glenohumeral instability and predictive tests that identify responders to conservative management.

Data Sources:

A comprehensive electronic bibliographic search was conducted using Embase, Ovid MEDLINE, PEDro, and CINAHL databases from their date of inception to February 2017.

Study Selection:

Studies were included for further review if they (1) reported on clinical diagnostic tests for posterior or posteroinferior instability of the glenohumeral joint, (2) assessed predictive clinical tests for posterior instability of the glenohumeral joint, and (3) were in English.

Study Design:

Systematic review.

Level of Evidence:

Level 4.

Data Extraction:

Data were extracted from the studies by 2 independent reviewers and included patient demographics and characteristics, index/reference test details (name and description of test), findings, and data available to calculate psychometric properties.

Results:

Five diagnostic and 2 predictive studies were selected for review. There was weak evidence for the use of the jerk test, Kim test, posterior impingement sign, and O’Brien test as stand-alone clinical tests for identifying posterior instability. Additionally, there was weak evidence to support the use of the painless jerk test and the hand squeeze sign as predictive tests for responders to conservative management. These findings are attributed to study design limitations, including small and/or nonrepresentative samples.

Conclusion:

Clustering of thorough history and physical examination findings, including the aforementioned tests, may identify those with posterior glenohumeral instability and assist in developing management strategies.

The Posterior Unstable Shoulder: Natural History, Clinical Evaluation and Imaging

Background:

There is a low incidence of posterior instability which is present in only 2% to 10% of all unstable shoulders. The posterior instable shoulder includes different manifestations like fixed dislocation, recurrent subluxation or dislocation.

Methods:

Research and online content related to posterior instability is reviewed. Natural history, clinical evaluation and imaging are described.

Results:

An awareness of the disorder, together with a thoughtful evaluation, beginning with the clinical history, usually leads to proper diagnosis. An appropriate physical exam, taking in account hyperlaxity and specific tests for posterior instability should be done.

Conclusion:

Posterior shoulder instability is an uncommon condition and is challenging to diagnose. There is not a single injury that is responsible for all cases of recurrent shoulder dislocation or subluxation, and the presence of soft tissue lesions or bone alterations should be evaluated, with the use of adequate simple radiology and multiplanar imaging.

Posterior Glenohumeral Instability: Evidence-based Treatment

Posterior glenohumeral instability is an increasingly important clinical finding in athletic patients. Over the last decade, basic and clinical research has improved our understanding of the pathoanatomy and biomechanics of this challenging disorder, as well as our ability to diagnose and appropriately treat it. Although recurrent posterior shoulder instability is not as common as anterior instability, it is prevalent among specific populations, including football and rugby players, and may be overlooked by clinicians who are unaware of the typical physical examination and radiographic findings.

Influence of the Labrum on Version and Diameter of the Glenoid: A Morphometric Study Using Magnetic Resonance Images

PURPOSE

To use magnetic resonance imaging to determine the influence of the labrum on both the osseous version and effective diameter of the glenoid.

METHODS

This was a retrospective, cross-sectional study of patients with shoulder pain who underwent MRI between February 2014 and February 2015. The morphology of the glenoid labrum and glenoid was scanned with a 3-T magnetic resonance imaging scanner, and variables were measured by use of IntelliSpace PACS Enterprise. Patients were included if they were aged between 18 and 40 years and the radiologist reported a normal glenohumeral joint or if they were young patients aged less than 30 years with acute traumatic isolated partial- or full-thickness tears of the rotator cuff with a history of symptoms of less than 3 months. A pilot study was conducted with 3 observers and 3 repeated measurements at intervals to determine the interobserver and intraobserver reliability. Data analysis included descriptive statistics of measured variables, as well as paired Student t tests to determine the relative difference between labral and osseous morphometric variables.

RESULTS

Excellent inter-rater reliability (0.95-0.96) and intrarater reliability (0.93-0.98) were obtained in the pilot study of 20 patients. The study population was composed of 100 patients with a mean age of 37.3 years (standard deviation [SD], 11.8 years), having a gender distribution of 56 male and 44 female patients; there were 53 right and 47 left shoulders. The glenoid osseous version measured -5.7° (SD, 5.3°), and the labral version measured -10° (SD, 5.5°); the glenoid osseous diameter measured 28.0 mm (SD, 3.3 mm), and the labral diameter measured 31.9 mm (SD, 3.2 mm). The labrum significantly increased the version by 4.3° (P = .001) and significantly increased the diameter by 3.9 mm (P = .001).

CONCLUSIONS

The results of this study showed that the labrum increased the effective glenoid version by 75% (4.3° of retroversion) and the effective glenoid diameter by 14% (3.9 mm).

LEVEL OF EVIDENCE

Level IV, prognostic case series.

Association of Traumatic and Atraumatic Posterior Shoulder Instability With Glenoid Retroversion and Outcomes After Arthroscopic Capsulolabral Repair

PURPOSE

To compare glenoid retroversion and functional outcomes between patients with traumatic onset of posterior shoulder instability (PSI) and patients with atraumatic onset of PSI.

METHODS

Patients with PSI who underwent arthroscopic posterior capsulolabral anchor repair, were active in sports, and had undergone surgery a minimum of 2 years earlier were included. Traumatic onset was defined as PSI that occurred after a trauma with the shoulder in adduction, flexion, and internal rotation in patients with no history of instability. Subjective evaluations were obtained with the American Shoulder and Elbow Surgeons (ASES); Quick Disabilities of the Arm, Shoulder and Hand; Single Assessment Numeric Evaluation (SANE); and Short Form 12 Physical Component Summary scores preoperatively and after a minimum 2-year follow-up postoperatively. Additional questions assessed return to sport and shoulder stability. Glenoid version was measured with a 2-dimensional glenoid vault method on magnetic resonance imaging.

RESULTS

A total of 41 shoulders in 38 patients were eligible for inclusion (3 female and 35 male patients; mean age, 27.6 years; age range, 13 to 66 years). Three patients refused participation, and 2 patients required subsequent surgery for failure. Postoperative outcomes were available for 32 of the remaining 36 shoulders (89%) with a mean follow-up of 4.1 years (range, 2.0 to 7.8 years; 20 atraumatic and 12 traumatic). The ASES score improved significantly in both groups (P < .03), whereas the SANE; Quick Disabilities of the Arm, Shoulder and Hand; and Short Form 12 Physical Component Summary scores only significantly improved for patients with traumatic PSI (P < .02). Baseline score-adjusted comparison between groups showed that the postoperative median ASES scores (atraumatic, 95.8; traumatic, 99.9) and SANE scores (atraumatic, 86.5; traumatic, 98.0) were significantly more improved in patients with traumatic PSI (P = .01 and P = .012, respectively). Atraumatic PSI was associated with significantly higher glenoid retroversion (-21.8° ± 4.2° vs -17.7° ± 5.5°, P = .032). There was no significant difference regarding return to sport (P = .375) or postoperative re-dislocations (P = .99) between the groups.

CONCLUSIONS

Atraumatic onset of PSI was associated with higher degrees of glenoid retroversion and less favorable functional outcomes of arthroscopic posterior capsulolabral anchor repair than traumatic PSI.

LEVEL OF EVIDENCE

Level III, retrospective case-control study.

Comparison of Glenoid Version and Posterior Humeral Subluxation in Patients With and Without Posterior Shoulder Instability

PURPOSE

To evaluate glenoid version and humeral subluxation on preoperative multiplanar imaging of patients who underwent surgery for posterior glenohumeral instability compared with a matched group of patients who had shoulder surgery for other pathology.

METHODS

All patients over a 2-year period who underwent surgery for posterior instability had preoperative magnetic resonance (MR) imaging or MR arthrogram reviewed. Patients undergoing shoulder surgery for reasons other than instability were identified as a control group and matched by sex, laterality, and age. Measurement of glenoid version and percentage of humeral subluxation was performed by 2 reviewers after completing a tutorial. Reviewers were blinded to diagnosis and to whether or not the patients were in the experimental or control group.

RESULTS

There were 41 patients in each group. The average glenoid version in the control group was 5.6° of retroversion (standard deviation [SD] 3.0), and the average humeral subluxation was 54% (SD 5.1%). In the experimental group, the average glenoid version was 8.1° of retroversion (SD 5.0). The average humeral subluxation in the experimental group was 56% (SD 6.8%). Student t test revealed a statistically significant difference in glenoid version (P = .009) but not humeral subluxation (P = .25). Intra- and inter-rater reliability was measured by the intraclass correlation coefficient and found to have an excellent Fleiss rating with regard to both measurements.

CONCLUSIONS

Glenoid retroversion is significantly increased in patients with symptomatic posterior labral tears compared with a control group. However, there was no statistically significant difference between the groups with regard to posterior humeral subluxation and, therefore, is not a reliable indicator of the presence or absence of symptomatic posterior shoulder instability.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Premorbid retroversion is significantly greater in type B2 glenoids

BACKGROUND

Posterior glenoid erosion is thought to be initiated by humeral head subluxation. However, it is unknown whether subluxation is entirely caused by soft-tissue instability and unbalanced muscle activity or whether osseous morphology is a contributing factor. We hypothesized that patients with posterior erosion may exhibit premorbid glenoid morphology that is inherently retroverted and inferiorly inclined compared with age-matched normal glenoids.

METHODS

This study examined 80 scapulae, evenly distributed between 2 groups: osteoarthritic with type B2 glenoids and age-matched normal glenoids. From 3-dimensional computed tomography reconstructions, version and inclination were measured from the anterior paleoglenoid region of the B2 glenoids, which is representative of the premorbid glenoid, and compared with measurements obtained from similar regions in the normal cohort.

RESULTS

The anterior paleoglenoid region of B2 glenoids was significantly (P < .001) more retroverted (-14° ± 6°) compared with similar regions in nonarthritic normal glenoids (-5° ± 5°). There were no significant differences (P = .166) in the glenoid inclination angle between type B2 glenoids (0° ± 6°) and nonarthritic normal glenoids (2° ± 5°). Negative values represent retroverted and inferiorly inclined glenoids.

DISCUSSION

Understanding premorbid glenoid morphologic variations may provide insight into the pathoanatomy of humeral head subluxation, osteoarthritis, and posterior glenoid erosion. The results of this study indicate that patients with type B2 osteoarthritic glenoids have significantly greater premorbid glenoid retroversion compared with nonarthritic normal glenoids, suggesting that this premorbid morphologic variation may be one contributing factor to posterior erosion.