Incidence of posterior shoulder instability and trends in surgical reconstruction: a 22-year population-based study

Biomechanics and Pathoanatomy of Posterior Shoulder Instability

Posterior glenohumeral instability represents a wide spectrum of pathoanatomic processes. A key consideration is the interplay between the posterior capsulolabral complex and the osseous anatomy of the glenoid and humeral head. Stability is dependent upon both the presence of soft tissue pathology (eg, tears to the posteroinferior labrum or posterior band of the inferior glenohumeral ligament, glenoid bone loss, reverse Hill Sachs lesions, and pathologic glenoid retroversion or dysplasia) and dynamic stabilizing forces. This review highlights unique pathoanatomic features of posterior shoulder instability and associated biomechanics that may exist in patients with posterior glenohumeral instability.

Osteochondral allografts for the treatment of shoulder instability

Aims

To systematically review the predominant complication rates and changes to patient-reported outcome measures (PROMs) following osteochondral allograft (OCA) transplantation for shoulder instability.

Methods

This systematic review, following PRISMA guidelines and registered in PROSPERO, involved a comprehensive literature search using PubMed, Embase, Web of Science, and Scopus. Key search terms included "allograft", "shoulder", "humerus", and "glenoid". The review encompassed 37 studies with 456 patients, focusing on primary outcomes like failure rates and secondary outcomes such as PROMs and functional test results.

Results

A meta-analysis of primary outcomes across 17 studies revealed a dislocation rate of 5.1% and an increase in reoperation rates from 9.3% to 13.7% post-publication bias adjustment. There was also a noted rise in conversion to total shoulder arthroplasty and incidence of osteoarthritis/osteonecrosis over longer follow-up periods. Patient-reported outcomes and functional tests generally showed improvement, albeit with notable variability across studies. A concerning observation was the consistent presence of allograft resorption, with rates ranging from 33% to 80%. Comparative studies highlighted similar efficacy between distal tibial allografts and Latarjet procedures in most respects, with some differences in specific tests.

Conclusion

OCA transplantation presents a promising treatment option for shoulder instability, effectively addressing both glenoid and humeral head defects with favourable patient-reported outcomes. These findings advocate for the inclusion of OCA transplantation in treatment protocols for shoulder instability, while also emphasizing the need for further high-quality, long-term research to better understand the procedure's efficacy profile.

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.

Batter's Shoulder: Diagnosis, Management, and Outcomes

Batter's shoulder is characterized by posterior shoulder instability in the lead (front) shoulder of a batting athlete. This most commonly occurs as a discrete event, particularly a swing and miss at an outside pitch, which leads to an episode of shoulder subluxation. A thorough history and physical examination is key to diagnosis, with patients feeling pain and instability of the lead shoulder when attempting the baseball swing or during pushing-type activities, as well as positive posterior labral signs in tests such as the Kim, jerk, and modified dynamic labral shear tests. Magnetic resonance imaging can confirm the diagnosis of posterior labral tear and may show concomitant pathologies such as a reverse Hill-Sachs lesion. Nonsurgical treatment is directed at rotator cuff and scapular strengthening; however, arthroscopic posterior labral repair is often required for definitive stabilization. Overall, this is a relatively rare diagnosis, but outcomes of surgical repair are favorable with high satisfaction and rates of return to competition.

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

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

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.

Posterior Compression Test: a Provocative Test for Detecting Posterior Labral Tears

Purpose

The purpose is to assess the diagnostic accuracy of a provocative test coined as the 'posterior compression test' (PCT) in those with the suspected posterior labral tear or lesion.

Methods

A total of 515 'arthroscopic labral repairs' were identified between April 2013 and September 2020. Excluding those with concomitant shoulder pathologies, and only including those with pre-operative documentation of the PCT and/or the Jerk test, 191 patients were included. For the purposes of the analyses, the patients were divided into 'non-posterior' labral tear group which included the anterior labral tears and/or the superior labral anterior-to-posterior (SLAP) tears, versus 'any posterior' labral tear group which included the isolated posterior labral tears, the SLAP tears with posterior extension and the pan-labral tears.

Results

When the PCT was performed for the isolated posterior labral tears, the sensitivity was 92.6% with the specificity of 86.5%. The positive predictive value and negative predictive value were 71.4-97%, respectively. The Jerk test's sensitivity was 77.8% but when the two tests were combined, the sensitivity increased up to 96.3%. The combined sensitivity with the Jerk test was still up to 94.6% with the AUC (area under curve) /ROC (receiver operator characteristic) at 0.855. Low 'false-positive' rate with the PCT was observed when the test was performed for the 'non-posterior' labral group, with the sensitivity of 13.5%.

Conclusions

The posterior compression test correlated well with the arthroscopic diagnoses in a subset of patients with suspected posterior labral pathology, possibly by means of direct stimulation.

Level of Evidence

III; Diagnostic Study.

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.

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.

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.

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.

Shoulder Dislocation Incidence and Risk Factors-Rural vs. Urban Populations of Poland

(1) Background: The aim of this study was to analyze the incidence of shoulder dislocation and to estimate non-modifiable risk factors in rural and urban subgroups in Poland. (2) Methods: The study covered the entire Polish population, divided into urban and rural subgroups and observed between 1 January 2014 and 31 December 2014. The study population consisted of Polish patients with a diagnosis of shoulder dislocation (S43.0) in accordance with the International Statistical Classification of Diseases and Related Health Problems (ICD-10). Records were obtained from the public health care provider National Health Found (Narodowy Fundusz Zdrowia, NFZ). Based on these data, we assessed shoulder dislocation incidence and risk rates, stratifying the study sample by sex, age and place of residence (rural or urban) using the Central Statistical Office (GUS) personal territorial code (TERYT). (3) The incidence was 25.97/100,000 person-years in rural areas and 25.62/100,000 person-years in urban areas. We did not find significant differences in the incidence between the two subgroups. The highest incidence (75.12/100,000 person-years) and the highest risk for shoulder dislocation were found among subjects 80+ years old living in urban areas. Furthermore, men in the third decade of their life living in urban areas showed the highest risk (OR = 7.8, 95% CI; 6.44-9.45, p < 0.001). In both subgroups, the likelihood of shoulder dislocation was significantly lower for the female sex and among children ≤9 years old. However, girls living in rural areas presented with a significantly higher likelihood for dislocation compared with their peers living in urban environments. (4) Conclusions: No significant difference in the incidence rate of shoulder dislocation between Polish residents living in rural and urban areas emerged. The highest incidence was observed among female subjects 80+ years old living in urban environments. The highest risk was found among men in the third decade of their life living in urban areas. In addition, girls in the first decade of their life living in rural areas had more shoulder dislocations than girls living in urban environments. Shoulder dislocation is dominant in female subjects aged 70-79 living in rural areas and in females 80+ years old living in urban areas.

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.

Arthroscopic Posterior Labral Repair and Capsular Closure via Single Working Portal for Posterior Shoulder Instability

Posterior shoulder instability (PSI) is a relatively less common form of instability that frequently affects young overhead or contact athletes. The etiology of PSI may be traumatic or atraumatic, with establishment of the diagnosis being more difficult in cases of atraumatic instability. Surgical management of PSI has evolved from open techniques to arthroscopic techniques. Posterior stabilization has commonly been performed with 2 posterior working portals with the patient in the lateral decubitus position. The objective of this Technical Note is to describe a technique for posterior labral repair using all-suture anchors with the patient in the beach-chair position via 1 working portal with capsular closure.

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.

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.

Variability of glenoid labral tear patterns: a study of 280 sequential surgical cases

BACKGROUND

Glenoid labrum tears are a common cause of shoulder pain and instability and tear patterns have historically been ascribed into categorical descriptions such as anterior, posterior, and superior labral tears (SLAP [superior labrum anterior and posterior]) with multiple subtypes. Although often quoted as representing no more than 10% of instabilities, posterior shoulder instability may be more common than previously recognized. The purpose of this study was to review observed labral tear patterns and compare incidence and morphologies to historical descriptions.

METHODS

All patients undergoing arthroscopic or open labral repair (Current Procedural Terminology codes 29806, 29807, 23455, 23460, 23462, 23465) by 2 fellowship-trained shoulder surgeons from July 2012 to May 2019 were retrospectively reviewed. Labral tears were categorized into 3 groups: exclusively anterior to the midline of the glenoid, exclusively posterior, and those crossing the midline of the glenoid. Chief complaint, mechanism of injury, hand dominance, preoperative MRI interpretation by surgeon, and independent radiologist were analyzed for each tear type.

RESULTS

During the 7-year period, 280 patients underwent arthroscopic or open labral repair. Sixty percent of tears were traumatic, with dislocation being the most common traumatic mechanism at 31.4%. Ten distinct tear patterns were identified: 3 types of 90° tears (anteroinferior, posteroinferior, and posterosuperior), 4 types of 180° tears (anterior, posterior, inferior, and SLAP), 2 types of 270° tears (anteroinferior and anterosuperior), and 360° labral tears. A total of 134 tears (47.9%) were classified as posterior, and 72 tears (25.7%) were anterior. Seventy-four tears (26.4%) were combined anterior-posterior tears. Labral tears involving some portion of the posterior labrum constituted 74% of tears. A significant association between tear location and primary complaint (P < .001) was noted. Patients with anterior tears complained of only instability in 62.5% of cases, and only pain in 22%. Patients with posterior labral tears complained primarily of pain in 68% of cases, and instability in 21%. There was an accurate preoperative diagnosis given by both radiologists and surgeons on 30% (n = 63) of the tears.

CONCLUSION

There is a wide variety of labral tear patterns identified at the time of surgery, and the incidence of posterior labral tears is higher than previously described. Isolated Bankart lesions are relatively rare and are often associated with more extensive labral lesions. Patients with posterior labral pathology more often complain of pain rather than instability, whereas patients with anterior labral tears more often complain of instability.

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

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

Incidence of Posterior Shoulder Instability in the United States Military: Demographic Considerations From a High-Risk Population

BACKGROUND

Relatively little is known about the true incidence of posterior shoulder instability in the United States.

PURPOSE/HYPOTHESIS

The purpose of this study was to characterize the incidence of posterior shoulder instability in the US military population and to examine which characteristics place these patients at highest risk. We hypothesized that the rate of posterior instability in this cohort of patients would be higher than previously reported.

STUDY DESIGN

Descriptive epidemiology study.

METHODS

All initial cases of posterior shoulder dislocation and subluxation in the Defense Medical Epidemiology Database were screened between 2016 and 2018 using the relevant International Classification of Diseases-Tenth Revision-Clinical Modification codes. Incidences were calculated, and multivariate Poisson regression was used to calculate adjusted rate ratios for the effects of sex, race, age, military service branch, rank, and year.

RESULTS

The overall unadjusted incidence was 0.032 per 1000 person-years for posterior dislocations, 0.064 per 1000 person-years for posterior subluxations, and 0.096 per 1000 person-years for all cases of posterior shoulder instability. The total incidence of all shoulder instability was 1.84 per 1000 person-years, with posterior shoulder instability accounting for 5.2% of total cases. For posterior subluxation, significant differences between groups were found in the unadjusted and adjusted rate ratio (ARR) for sex (ARR, 3.31; 95% CI, 1.85-5.93 for men), race (ARR, 0.458; 95% CI, 0.294-0.714 for Black servicemembers and ARR, 0.632; 95% CI, 0.421-0.948 for servicemembers of other race), age (ARR, 3.69; 95% CI, 1.56-8.70 for patients aged 30-34 years), and military service branch (ARR, 0.663; 95% CI, 0.460-0.955 for Air Force servicemembers). For posterior shoulder dislocations, a significant difference was found only between men and women (ARR, 4.55; 95% CI, 1.85-11.2 for men).

CONCLUSION

The incidence of posterior shoulder instability among US military personnel is higher than previously reported in the general US population, with a majority of cases due to subluxation. This increased incidence is likely reflective of a young and highly active population along with improvements in awareness and diagnosis of posterior instability in recent years.

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.

Arthroscopic "Bone Block Cerclage" Technique for Posterior Shoulder Instability

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

Posterior shoulder instability: a systematic review

INTRODUCTION

This review aims to provide information on outcomes of surgical procedures for soft tissue or bony glenoid and/or humeral abnormalities in case of posterior shoulder instability.

SOURCE OF DATA

A systematic review of the literature according to the PRISMA guidelines was performed. A comprehensive search of PubMed, Medline, CINAHL, Cochrane, Embase, Ovid and Google Scholar databases using various combinations of the keywords 'shoulder', 'posterior instability', 'dislocation', 'reversed bony bankart', 'reversed Hill Sachs', and 'capsulolabral' was performed.

AREAS OF AGREEMENT

A total of 847 shoulders in 810 patients were included. A redislocation event occurred in 33 (8.7%) of 411 shoulders with soft tissue abnormalities and in 12 (9.1%) of 132 shoulders with bony abnormalities of the glenoid, humeral head or both.

AREAS OF CONTROVERSY

The optimal treatment modalities for posterior shoulder dislocation remain to be defined.

GROWING POINTS

Operative stabilization for posterior shoulder instability should be lesion-specific and should correct all components of the posterior instability.

AREAS TIMELY FOR DEVELOPING RESEARCH

Future prospective studies should aim to establish the optimal treatment modalities for posterior shoulder instability.

Posterior Shoulder Instability: Surgical Outcomes and Risk of Failure in Adolescence

BACKGROUND

Arthroscopic capsulolabral reconstruction has proven to be effective in treating posterior shoulder instability. Few studies have examined the risk factors that may contribute to poor outcomes in the adolescent population.

PURPOSE

To identify risk factors for surgical failure by comparing anatomic and subjective variations in children who underwent surgical intervention for posterior shoulder instability.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

All patients undergoing arthroscopic shoulder surgery at one institution between 2011 and 2018 were reviewed. Patients >18 years old at presentation and those with Ehlers-Danlos syndrome were excluded. Posterior instability was defined as unidirectional subluxation on posterior drawer testing while under anesthesia. Two-year minimum follow-up was required, but those whose treatment failed earlier were included for calculation purposes. Demographics and intraoperative findings were recorded, as were Single Assessment Numeric Evaluation (SANE) scoring, Pediatric and Adolescent Shoulder Survey (PASS), and the short version of the Disabilities of the Arm, Shoulder and Hand (QuickDASH) results. Major complication was defined as revision arthroscopy or redislocation, and minor complications included self-reporting a poor outcome score (eg, SANE score <65).

RESULTS

A total of 48 children (23 girls and 25 boys) met criteria, with a mean age of 16.5 years (range, 12.4-17.9 years) and a mean follow-up of 3.75 years. Fifteen (31.3%) patients had a complication by our criteria, including 12.5% with surgical failures; regarding major complications, boys were treated successfully 96% of the time and girls 78% of the time (P = .049). Of the anatomic and subjective variables tested, only younger age (P≤ .001) and presentation type (P < .05) were correlated with complications. SANE scores differed significantly (P < .002) by presentation type, with mean scores of 52 (trauma), 94 (recurrent instability), and 81 (pain). QuickDASH scores demonstrated patients with a history of trauma (mean, 37), instability (mean, 9), and pain (mean, 11).

CONCLUSION

Adolescents treated surgically for posterior shoulder instability are at risk of treatment failure (when including outcome scores), and it appears that patients of female sex, younger age, and traumatic presentation are at the highest risk to require revision surgery or experience continued limitations secondary to their shoulder.

Editorial Commentary: Nonoperative Treatments Seem Unreliable in Posterior Shoulder Instability, But Let's Take a Closer Look

Nonoperative treatment has been the initial treatment of choice in posterior shoulder instability. However, not much clinical data are available in the literature, and so many issues about nonoperative treatment, such as rehabilitation protocols, specific indications, expected outcomes, and predictable factors affecting outcomes, still remain unclear. With a paucity of clinical and no long-term data, shoulder surgeons need to wait a bit more to establish the optimal treatment strategy for posterior shoulder instability.