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In young athletes, anterior shoulder instability is a prevalent condition. Because of high-energy traumas, contact athletes often suffer recurrent instability, bone loss and postoperative recurrences. Patients younger than 20 years, symptomatic for more than 6 months, with ≥ 2 dislocations, with off-track Hill-Sachs lesion, glenoid bone loss, ALPSA lesion, Instability Severity Index Score > 3, and Glenoid Track Instability Management Score > 3 are at higher risk of failure. In cases of multiple dislocations with critical or subcritical glenoid bone loss, notably in collision and contact athletes, the Latarjet procedure is widely recognized as the treatment of choice.

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PURPOSE OF REVIEW: The management options for anterior shoulder instability with minimal bone loss or with critical bone loss are well established. However, there is less clear evidence to guide management for patients with subcritical bone loss, the spectrum of pathology where soft tissue repair alone is prone to higher rates of failures. In this range of bone loss, likely around 13.5% to 20%, the goal of surgery is to restore function and stability while limiting morbidity. As with many procedures in the shoulder, this decision should be tailored to patient anatomy, functional goals, and risk factors. This article provides a review of our current understanding of subcritical bone loss and treatment strategies as well as innovations in management. RECENT FINDINGS: While surgeons have largely understood that restoration of anatomy is important to optimize outcomes after stabilization surgery, there is increasing evidence that reconstructing bony anatomy and addressing both osseous and soft tissue structures yields better results than either alone. Even in the setting of subcritical bone loss, there is likely a benefit to combined osseous augmentation with soft tissue management. Additionally, there is new evidence to support management of even on-track humeral lesions when the distance to dislocation is sufficiently small, particularly for athletes. Surgeons must balance bony and soft tissue restoration to achieve optimal outcomes for anterior instability with subcritical bone loss. There are still significant limitations in the literature and several emerging techniques for management will require further study to prove their long-term efficacy. Beyond surgery, there should be a focus on a collaborative treatment strategy with the surgeon, patient, and therapists to achieve high-level function and minimize recurrence.

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A proportion of patients with anterior glenohumeral instability present with bipolar bone loss comprising large Hill-Sachs lesions and substantial glenoid defect. These are surgically difficult cases to treat. We describe a novel surgical procedure of bulk size-matched osteochondral allograft reconstruction for massive Hill-Sachs lesions combined with the Latarjet procedure for these challenging cases.

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Studies have shown that glenoid- and humeral-sided bone loss may be present in up to 73-93% of individuals with recurrent anterior shoulder instability. As such, bone loss must be addressed appropriately, as the amount of bone loss drives surgical decision making and influences outcomes. Methods to describe and measure bone loss have changed over time. Originally, glenoid and humeral bone loss were viewed separately. However, the concepts of bipolar bone loss, the glenoid track (GT), and "on/off-track" lesions arose, highlighting the interplay between the two entities in contributing to recurrent instability. Classically, "off-track" lesions have been described as those Hill-Sachs interval (HSI) greater than the GT, and have been shown to result in higher rates of re-instability when addressed nonoperatively or with Bankart repair alone. More recently, further attention has been given to "on-track" lesions (HSI < GT). The new concept of "distance to dislocation" (DTD) has gained popularity. DTD is calculated as the difference between the GT and HSI, and literature evaluating DTD suggests that not all "on-track" lesions should be treated in the same manner. The purpose of this concept review article is twofold: (I) describe glenoid, humeral, and bipolar bone loss in the setting of anterior shoulder instability; and (II) elaborate on the new concept of "DTD" and its use in guidance of management.

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BACKGROUND: The glenoid track concept is used to determine preoperatively whether a Hill-Sachs defect is engaging or not. Currently, the glenoid track concept relies on measurements of bony structures as well as on the confines and elasticity of the rotator cuff as a reference point, which varies extensively among individuals and therefore limits the reliability and accuracy of this concept. PURPOSE: To evaluate the reliability of the global track concept, which determines the angular distance of the Hill-Sachs defect from the center of the articular surface of the humeral head as a new reference point with the help of an automated image analysis software and 3-dimensional analysis of the humeral head. STUDY DESIGN: Controlled laboratory study. METHODS: Computed tomography scans of 100 patients treated for anterior shoulder instability with different sizes of Hill-Sachs defects were evaluated manually by 2 orthopaedic surgeons independently using the software OsiriX as well as automatically by using a dedicated prototype software (ImFusion). Obtained manual and automated measurements included the Hill-Sachs length, Hill-Sachs width, and Hill-Sachs depth of the defect; the Hill-Sachs interval (HSI); and the glenoid width for the glenoid track concept, as well as the angular distance of the Hill-Sachs defect from the center of the articular surface of the humeral head (global track concept). The reliability of the different measurement techniques was compared by calculating intraclass correlation coefficients (ICCs). RESULTS: There was a significant difference for all obtained parameters comparing manual and automatic measurements. For manually obtained parameters, measurements referring to bony boundaries (glenoid width, Hill-Sachs length, and Hill-Sachs width) showed good to excellent agreement (ICC, 0.86, 0.82, and 0.62, respectively), while measurements referring to soft tissue boundaries (HSI and glenoid track; ICC, 0.56 and 0.53, respectively) or not directly identifiable reference points (center of articular surface and global track) only showed fair reliability (ICC middle excursion, 0.42). When the same parameters were measured with the help of an automated software, good reliability for the glenoid track concept and excellent reliability for the global track concept in the middle excursion were achieved. CONCLUSION: The present study showed that the more complex global track measurements of humeral defects are more reliable than the current standard HSI and glenoid track measurements. However, this is only true when automated software is used to perform the measurements. CLINICAL RELEVANCE: Future studies using the new proposed method in combination with an automated software need to be conducted to determine critical threshold values for defects prone to engagement.

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Posttraumatic instability accounts for more than 95% of all shoulder instabilities with the highest incidence in patients between 20 and 30 years of age. In this age group, lesions of the capsulolabral complex are the most common sequelae after the first shoulder dislocation. Typical acute findings are the Bankart and Perthes lesions and humeral avulsion of the glenohumeral ligament (HAGL). Chronic sequelae are anterior labroligamentous periosteal sleeve avulsion (ALPSA) lesions, and nonclassifiable lesions with deficient anterioinferior labrum and glenohumeral ligaments. Recently, quantification of Hill-Sachs and bony Bankart lesions with glenoid defects have become the focus of interest: bipolar bone loss has emerged to be one important factor of recurrent instability that has not been addressed during the first stabilizing operation. The glenoid track concept emphasizes the importance of bipolar bone loss, where the glenoid track refers to the contact area between the humeral head and the glenoid at the end-range of motion in abduction, extension and external rotation. Any lesion of the humeral head that extends beyond the glenoid track is considered high risk for engagement of the humeral head at the glenoid margin with subsequent dislocation. Both the Hill-Sachs interval and the glenoid track can be determined using computed tomography (CT) and magnetic resonance imaging and, thus, help to define the status of the shoulder (on-track vs. off-track), which is prerequisite for planning the appropriate operative procedure. Similar tendencies also exist for posttraumatic posterior instabilities which are much rarer.

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BACKGROUND: Although Hill-Sachs lesions (HSLs) are assumed to be influenced by glenoid characteristics in the context of bipolar bone loss, little is known about how glenoid concavity influences HSL morphology. PURPOSE: To investigate the relationship between the native glenoid depth and HSL morphological characteristics. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: Computed tomography images of bilateral shoulders from 151 consecutive patients with traumatic unilateral anterior shoulder instability were retrospectively reviewed. Patients were categorized into flat (<1 mm), moderate (1-2 mm), and deep (>2 mm) groups based on the native glenoid depth measured from the contralateral unaffected shoulder. The HSL morphological characteristics included size (depth, width, length, and volume), location (medial, superior, and inferior extent), and orientation (rim and center angle). The glenoid characteristics included diameter, depth, version, and bone loss. The patient, glenoid, and HSL morphological characteristics were compared among the 3 depth groups. Subsequently, the independent predictors of some critical HSL morphological characteristics were determined using multivariate stepwise regression. RESULTS: After exclusion of 55 patients, a total of 96 patients were enrolled and classified into the flat group (n = 31), moderate group (n = 35), and deep group (n = 30). Compared with those in the flat group, patients in the deep group were more likely to have dislocation (38.7% vs 93.3%; P = .009) at the primary instability and had a significantly larger number of dislocations (1.1 ± 1.0 vs 2.2 ± 1.8; P = .010); moreover, patients in the deep group had significantly deeper, wider, larger volume, more medialized HSLs and higher incidences of off-track HSLs (all P≤ .025). No significant differences were detected among the 3 groups in HSL length, vertical position, and orientation (all P≥ .064). After adjustment for various radiological and patient factors in the multivariate regression model, native glenoid depth remained the strongest independent predictor for HSL depth (ß = 0.346; P < .001), width (ß = 0.262; P = .009), volume (ß = 0.331; P = .001), and medialization (ß = -0.297; P = .003). CONCLUSION: The current study sheds light on the association between native glenoid depth and the morphology of HSLs in traumatic anterior shoulder instability. Native glenoid depth was independently and positively associated with HSL depth, width, volume, and medialization. Patients with deeper native glenoids were more likely to have off-track HSLs and thus require more attention in the process of diagnosis and treatment.

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PURPOSE: To evaluate long-term results after arthroscopic Bankart repair and Hill-Sachs remplissage (BHSR) in bipolar bone defects with less than 20% of glenoid bone loss (GBL) and to analyse risk factors for recurrent dislocation. METHODS: From 2009-2012, 43 patients with recurrent anterior shoulder instability were treated with BHSR. Inclusion criteria were GBL < 20% and minimum of 4-yearfollow-up. There were 35 males and 8 females with a mean age of 29 years (range 16-53). The mean ISIS score was 3.6 (range 2-6). Patients were evaluated for recurrence, range of motion and functional outcomes (Walch-Duplay and Rowe score). Post-operative MRI was performed at least 6 months after surgery to evaluate infraspinatus capsulotenodesis healing. Glenoid track was assessed retrospectively from pre-operative computed tomography. Mean follow-up was 7.3 years (range 4-11). RESULTS: At the last follow-up, good to excellent outcomes were reported in 86% of patients. Average post-operative Walch-Duplay was 87.9 (range 75-100) and ROWE 93.7 (range 70-100). Infraspinatus capsulotenodesis healing was achieved in 86%. The rate of recurrence and revision surgery was 9.3% and 13.9%, respectively. Recurrence was associated with higher ISIS score (p = 0.0191) and lower age at surgery (p = 0.0227). Four (9.3%) Hill-Sachs lesions were considered off-track. The presence of off-track Hill-Sachs was associated with higher risk of recurrence (p < 0.00001). CONCLUSION: Arthroscopic BHSR improves shoulder instability in the setting of bipolar bone defects with less than 20% of GBL. Patient-related factors and pre-operative glenoid track should be taken into consideration to reduce the risk of recurrence.

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Posterior glenohumeral instability is an increasingly common and challenging orthopaedic problem. While an arthroscopic soft tissue stabilization procedure (i.e., reverse Bankart repair) is effective in treating most cases of posterior instability, this procedure may be inadequate in shoulders with critical posterior glenoid bone loss (GBL), or in cases of an engaging reverse Hill-Sachs lesion. Thus, the purpose of the present manuscript was to report contemporary surgical approaches, techniques, and outcomes for the open treatment of glenoid or humeral head bone loss in posterior instability to help guide clinical decision making. Open osteoarticular augmentation procedures have emerged as a popular option to treat posterior bone loss, with bony auto- and allografts utilized from a variety of donor sites including iliac crest, scapular spine, acromion, distal clavicle, and distal tibia. The combination of glenoid retroversion and bone loss can be addressed with a posterior glenoid opening wedge osteotomy. Bipolar bone loss may be treated with a combination of the aforementioned techniques, in addition to a reverse remplissage, a modified McLaughlin procedure, or various arthroplasty-related options. Although short and mid-term outcomes are dependable, studies reporting long-term outcomes are sparse. Moreover, there is no current consensus regarding the most effective treatment of posterior shoulder instability in the setting of bone loss, and open surgical techniques continue to evolve. Further research is necessary to determine long-term effectiveness of these surgical options.

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PURPOSE OF REVIEW: The aim of this scoping review is to identify and summarize findings published in the literature over the past 5 years related to methods for assessment of bone loss in anterior shoulder instability. RECENT FINDINGS: Of the 113 clinical studies included in this review, 76 reported a cutoff for glenoid bone loss when determining the patients indicated for one of the many stabilization procedures investigated. Bone loss on the glenoid side was evaluated most commonly with three-dimensional computed tomography (3D CT), and either linear or surface area-based methods were employed with the use of a best-fit circle. When combined with plain CT, the two methods comprise up to 70% of the reported measurement techniques for glenoid bone loss (79 of 113 studies). On the humeral side, Hill-Sachs lesions were assessed more heterogeneously, though plain CT or 3D CT remained the methods of choice in the majority of studies (43 of 68, 63.2%). Lastly, the glenoid track was assessed by 27 of 113 studies (23.9%), again most commonly with 3D CT (13 studies) and plain CT (seven studies). The assessment of glenoid and humeral bone loss is essential to treatment decisions for patient with recurrent anterior shoulder instability. Glenoid bone loss is most commonly assessed using cross-sectional imaging, most often 3D CT, and some variation of a best-fit circle applied to the inferior portion of the glenoid. Hill-Sachs lesion assessment was also commonly done using three-dimensional imaging; however, there was more variability in assessment methods across studies and there is an obvious need to unify the approach to humeral bone loss assessment for the purposes of improving treatment decisions and to better assess on-track and off-track lesions.

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BACKGROUND: The presence of bone loss has important implications for the surgical treatment of patients with recurrent shoulder instability. The bony apprehension test (BAT) is a physical examination maneuver that was designed to improve specificity from the anterior apprehension test (AAT) in detecting critical bone loss. PURPOSE: The purpose of this study was to compare the BAT with the AAT and relocation test based on their abilities to predict critical bone loss. Several well-described criteria were utilized to capture critical (≥25%) and subcritical (≥13.5%) glenoid defects, as well as Hill-Sachs defects (≥19%). The ability of the BAT to predict bipolar bone loss was also assessed, as indicated by engaging Hill-Sachs defects and off-track lesions. STUDY DESIGN: Cohort study (diagnosis); Level of evidence, 1. METHODS: The study cohort included patients ≥18 years of age who were scheduled to undergo arthroscopic stabilization for traumatic anterior shoulder instability. Notable exclusion criteria included multidirectional shoulder instability, connective tissue disorders, and workers' compensation or litigation cases. Patients underwent physical examination immediately before surgery by the treating surgeon (ie, before the induction of anesthesia). Critical glenoid and humeral bone defects were measured on preoperative computed tomography scans. Hill-Sachs engagement and on- or off-track determination of bone loss were assessed arthroscopically and via computed tomography, respectively. RESULTS: A total of 52 patients were included in the study. In cases of subcritical glenoid bone loss (≥13.5%) and critical Hill-Sachs defects (≥19%), the BAT had good and fair specificity (82% and 72%, respectively) but poor sensitivity (40% and 39%). The BAT also had poor sensitivity (0%), specificity (67%), and positive predictive value (0%) for higher percentages of glenoid bone loss (≥25%). When engaging Hill-Sachs lesions were assessed, the BAT had excellent specificity (94%) and positive predictive value (94%) but poor sensitivity (43%) and negative predictive value (44%). Furthermore, the BAT performed poorly at predicting off-track humeral lesions. The AAT demonstrated 100% sensitivity and 0% specificity in detecting all measures of bone loss. CONCLUSION: The BAT performed poorly at identifying subcritical and critical bone loss and was not found to have any clinical value. Future work is needed to identify a physical examination test that could complement advanced imaging for preoperative assessment of critical bone loss.

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Bipolar glenohumeral bone loss is a challenging condition to address in patients with recurrent anterior shoulder instability. In this category of patients, most isolated soft-tissue procedures such as remplissage or infraspinatus capsulotenodesis are associated with high risk of failure and instability recurrence. Even bony procedures such as Latarjet may fail to provide absolute stability, and instability may eventually recur. For a better understanding of the cause of failure in this particular type of patient, we may refer to the glenoid track concept which has been described as a useful tool for surgical planning. In fact, Latarjet procedure alone may leave a place for engagement of the Hill-Sachs defect on the anterior glenoid resulting in an off-track situation and secondary glenohumeral instability. In this technical note, we present the combination of arthroscopic remplissage and an open Latarjet procedure to treat patients with bipolar glenohumeral bone loss with good results at 31-month follow-up. Our aim is to propose these techniques as a possible rescue procedure for highly unstable shoulders combining engaged Hill-Sachs lesion and glenoid bone loss of more than 25%. We believe this technique would be a good option for patients who present other risk factors of recurrence such as past medical history of epilepsy, laxity, and psychiatric illnesses.

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BACKGROUND: The investigation of Hill-Sachs and bony Bankart lesions continues to evolve. Patients with large bone lesions can present with a positive apprehension test even at ranges below 45° of abduction and external rotation of the shoulder. Modern concepts, such as glenoid track and quantification of glenoid bone loss, have been increasingly applied to shoulder instability. The objective of this study was to assess the correlation of the glenoid track and glenoid bone loss on the apprehension test conducted at 0°, 45°, and 90° of shoulder abduction. METHODS: Ninety-four shoulders of 90 patients with anterior glenohumeral instability were retrospectively assessed. The apprehension test was performed at 0°, 45°, and 90° of shoulder abduction. Computed tomography, magnetic resonance imaging, or magnetic resonance arthrogram scans were performed to calculate the glenoid track and glenoid bone loss. A descriptive analysis, an association analysis, and a logistic regression analysis were used in this study. Logistic regression analysis was used to assess the influence of glenoid track and glenoid bone loss when the apprehension test was positive in lower degrees of abduction. RESULTS: A positive apprehension test at 0°, 45°, and 90° of abduction revealed significant association with off-track lesions, glenoid bone losses greater than 13.5%, and bipolar bone lesions. Shoulders classified as off-track were 36.4 times more likely to test positive at 0°, 45°, and 90° than on-track shoulders. The logistic regression analysis revealed that the positive apprehension test at 0°, 45°, and 90° of abduction seems to be more influenced by off-track lesions than by glenoid bone loss greater than the 13.5% threshold. CONCLUSION: Shoulders with a positive apprehension test at 0°, 45°, and 90° are significantly associated with off-track lesions, bipolar bone lesions, and glenoid bone losses greater than 13.5%.

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BACKGROUND: The glenoid track is a useful tool to predict engagement and therefore the risk of recurrence of dislocation in the presence of Hill-Sachs and/or bony Bankart lesions. To assess the glenoid track preoperatively, only methods using 3-dimensional reconstruction (3DR) have been described, but these lack a standardized, reliable, and easy description. PURPOSE/HYPOTHESIS: The purpose was to evaluate a new method for determining the glenoid track using computed tomography (CT) scan with multiplanar reconstruction (MPR) in comparison with using 3DR images. Our hypothesis was that the MPR method would be easier to standardize and more reproducible. STUDY DESIGN: Cohort study (diagnosis); Level of evidence, 2. METHODS: A total of 52 patients whose arthro-CT scan revealed a Hill-Sachs lesion, whether in combination with a bony Bankart lesion or not, were included. Digital Imaging and Communications in Medicine data from the 52 CT scans were all analyzed using open source image analysis software. Glenoid width, with or without associated bony defect, and the Hill-Sachs interval (HSI) were measured on MPR as well as on 3DR images. All measurements obtained using both methods were directly compared and evaluated for intra- and interobserver reliability. RESULTS: In absolute values, only small differences were seen between the MPR and 3DR methods, amounting to a maximal difference of 0.07 cm for the HSI and 0.04 cm for the glenoid width. For glenoid measurements, both methods were similar. For humeral measurements, the MPR method demonstrated higher inter- and intraobserver reliability than did the 3DR method. CONCLUSION: The newly described MPR method for the assessment of the glenoid track and HSI is at least as accurate as the published 3DR method, with better intra- and interobserver reliability. Because MPRs are also easier to obtain, this method could be recommended in daily practice.

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BACKGROUND: Recurrence of glenohumeral joint instability after primary traumatic anterior instability is not rare, and bipolar bone loss is one of the most critical factors for recurrent instability, but the development process of bipolar bone defects is still unclear. PURPOSE: To investigate the development process of bipolar bone defects from primary to recurrent instability among shoulders with traumatic anterior instability evaluated at least twice by computed tomography (CT). STUDY DESIGN: Case series; Level of evidence, 4. METHODS: There were 44 patients (47 shoulders) with recurrence after primary instability in which bone morphology was evaluated by 3-dimensional reconstructed CT at primary instability (initial CT) and after recurrence. As CT was performed 3 times for 3 shoulders including primary injury and the second episode of instability (first recurrence), there were 50 CT evaluations. Morphological changes between the initial CT evaluation at primary instability and the second CT evaluation at first recurrence were investigated for 25 shoulders, with the mean interval since initial CT being 9.8 months (range, 2-23 months). Changes between initial CT evaluation and final CT evaluation after ≥2 recurrences were also investigated for 25 shoulders, while the mean number of instability episodes including primary instability was 8.0 (range, 3-40) and the mean interval since initial CT was 18.5 months (range, 5-56 months). RESULTS: At primary instability, the prevalence of Hill-Sachs lesions (66.0%) was almost double that of glenoid defects (34.0%), but their prevalence was different between shoulders with primary subluxation (42.3% and 23.8%, respectively) and those with primary dislocation (84.7% and 42.3%, respectively). After recurrence, glenoid defects became significantly more frequent (at first recurrence, 72%; after ≥2 recurrences, 76%), while Hill-Sachs lesions showed a smaller increase (88% and 80%, respectively), so there was no difference between the prevalence of the 2 lesions. The sizes of glenoid defects and Hill-Sachs lesions also enlarged after recurrence, and large bone defects were frequently recognized after recurrence. While bipolar bone loss was not so frequent at primary instability (29.8%), bipolar bone loss increased significantly after recurrence (at first recurrence, 72%; after ≥2 recurrences, 72%). All Hill-Sachs lesions were on track at primary instability, but off-track lesions were recognized in 3 of 47 shoulders (6.4%) after recurrence. CONCLUSION: In most shoulders with recurrent instability, a Hill-Sachs lesion developed first, followed by a glenoid defect, leading to bipolar bone loss. Off-track Hill-Sachs lesions were detected only after recurrence.

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BACKGROUND: There is increasing evidence to suggest that the amount of glenoid bone loss to indicate bone block procedures may be lower than previously thought, particularly in the presence of a Hill-Sachs defect. PURPOSE: To better establish treatment recommendations for anterior shoulder instability among patients with bipolar bone lesions. STUDY DESIGN: Systematic review and meta-analysis; Level of evidence, 4. METHODS: A systematic review of the literature was performed with PubMed, EMBASE, Cochrane Library, and Scopus databases according to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) guidelines. Studies evaluating outcomes of operative management in anterior shoulder instability that also reported glenoid bone loss in the presence of Hill-Sachs defects were included. Recurrence rates, glenoid bone loss, and humeral bone loss were pooled and analyzed with forest plots stratified by surgical procedure. Methods of quantification were analyzed for each article qualitatively. RESULTS: Thirteen articles were included in the final analysis, with a total of 778 patients. The mean ± SD age was 24.9 ± 8.6 years. The mean follow-up was 30.1 months (range, 11-240 months). Only 13 of 408 (3.2%) reviewed bipolar bone loss articles quantified humeral and/or glenoid bone loss. Latarjet procedures had the greatest glenoid bone loss (21.7%; 95% CI, 14.8%-28.6%), followed by Bankart repairs (13.1%; 95% CI, 9.0%-17.2%), and remplissage (11.7%; 95% CI, 5.5%-18.0%). Humeral bone loss was primarily reported as percentage bone loss (22.2%; 95% CI, 13.1%-31.3% in Bankart repairs and 31.7%; 95% CI, 21.6%-41.1% in Latarjet) or as volumetric defects (439.1 mm3; 95% CI, 336.3-541.9 mm3 in Bankart repairs and 366.0 mm3; 95% CI, 258.4-475.4 mm3 in remplissage). Recurrence rates were as follows: Bankart repairs, 19.5% (95% CI, 14.5%-25.8%); remplissage, 4.4% (95% CI, 1.3%-14.0%); and Latarjet, 8.7% (95% CI, 5.0%-14.7%). Bankart repairs were associated with significantly greater recurrence of instability in included articles (P = .013). CONCLUSION: There exists a need for universal and consistent preoperative measurement of humeral-sided bone loss. The presence of concomitant Hill-Sachs defects with glenoid pathology should warrant more aggressive operative management through use of bone block procedures. Previously established values of critical glenoid bone loss are not equally relevant in the presence of bipolar bone loss.

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BACKGROUND: The combination of a glenoid defect and a Hill-Sachs lesion in a shoulder with anterior instability has recently been termed "bipolar bone loss," but the prevalence and influence of this condition on postoperative recurrence after arthroscopic Bankart repair are still unclear. PURPOSE: To investigate bipolar bone loss in male athletes using a new scoring system and to evaluate its efficacy by comparing it with the glenoid track concept. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: The sizes of both lesions were evaluated retrospectively in 80 male athletes (85 shoulders) using computed tomography. The glenoid defects and the length, width, and depth of the Hill-Sachs lesions were classified into 5 size categories and were allocated scores from "0" for no defect to "4" for the largest defect. Patients were then classified into 5 classes according to the total score for both lesions: class 1, 0-1 point; class 2, 2 points; class 3, 3 points; class 4, 4 points; and class 5, ≥5 points. The prevalence of bipolar bone loss and postoperative recurrence rates for patients with at least 2 years of follow-up were compared among the classes. The recurrence rate for each class was also compared between shoulders with an off-track lesion and shoulders with an on-track lesion as well as among 3 sporting categories: rugby, American football, and other sports. RESULTS: Based on the combination of glenoid defect size and Hill-Sachs lesion length, the postoperative recurrence rate was 0% for shoulders in class 1, 12.5% for class 2, 33.3% for class 3, 28.6% for class 4, and 31.3% for class 5, while the recurrence rates were 0%, 16.7%, 28.6%, 27.3%, and 31.6%, respectively, for the combination of glenoid defect size and Hill-Sachs lesion width and 0%, 8.3%, 26.7%, 28.6%, and 35.3%, respectively, for the combination of glenoid defect size and Hill-Sachs lesion depth. Postoperative recurrence was frequently recognized regardless of the presence of off-track Hill-Sachs lesions. No recurrence was recognized in class 1 shoulders among rugby players, in classes 1 and 2 among American football players, and in classes 1 through 3 among other athletes based on the combination of glenoid defect size and Hill-Sachs lesion size. CONCLUSION: Our scoring system for bipolar bone loss was useful to evaluate the influence on postoperative recurrence in male athletes. The postoperative recurrence rate was influenced by the extent of bipolar bone loss and the sporting category regardless of the presence of off-track lesions.

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BACKGROUND: The risk of re-engagement of bipolar bone defects in posterior shoulder instability has not yet been investigated. HYPOTHESIS: Posterior glenoid defects can lead to the engagement of supposedly noncritical reverse Hill-Sachs lesions (RHSLs). STUDY DESIGN: Descriptive laboratory study. METHODS: In a retrospective multicenter study, 102 cases of posterior shoulder dislocations and resulting RHSLs were collected. Of these cases, all patients with available computed tomography (CT) scans, with a reduced shoulder joint, and without bony posterior glenoid rim defects or concomitant dislocated fractures of the humeral head were included. The gamma angle (measure of the critical size and localization of RHSLs) and the delta angle (measure of the degree of internal rotation necessary for engagement to occur) of the RHSLs were determined on standardized CT scans. Virtual posterior glenoid defects were created, and the effect of increasing defect size on the delta angle was determined. RESULTS: The mean gamma angle of the 19 patients included in this study was 94.5° (range, 69.7°-124.8°). After creation of the virtual posterior glenoid defects, a mean reduction of the delta angle by 2.3° ± 0.2° (range, 1.9°-2.9°) per millimeter defect was observed. The cumulative change in the delta angle showed a highly significant correlation with the absolute and relative size of the glenoid defect ( R = 0.982, P < .001 and R = 0.974, P < .001, respectively). CONCLUSION: Concomitant posterior glenoid defects might lead to the engagement of noncritical RHSLs. When measuring the gamma angle to identify critical RHSLs, posterior glenoid bone loss should be accounted for.

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OBJECTIVE: The purpose of this study was to determine whether the simultaneous MRI evaluation of Hill-Sachs lesions and glenoid bone loss by use of the on-track off-track method can be used to predict engagement during arthroscopy. MATERIALS AND METHODS: The records of 75 consecutively registered patients (60 male patients, 15 female patients) with a history of previous anterior shoulder instability who underwent preoperative MRI of the shoulder and arthroscopy at our institution were reviewed. A total of 76 MRI examinations were included. Two readers reviewed the MR images of each patient blindly and independently and used the on-track off-track method to predict engagement. These results were compared with the findings related to engagement seen during arthroscopy, which was performed by one of seven orthopedic surgeons. Statistical analyses included Fisher exact test, logistic regression, ROC analysis, and calculation of intraclass correlation coefficients. RESULTS: Using the on-track off-track technique of reading MR images, the reviewers correctly predicted 13 of the 18 engaging (off-track) lesions (sensitivity, 72.2%). Among the 58 shoulders that did not engage (on-track), they correctly predicted 51 (specificity, 87.9%). Overall, the accuracy of the on-track off-track method was 84.2% with a positive predictive value of 65.0% and negative predictive value of 91.1%. CONCLUSION: Our study showed that the on-track off-track method can be used in MRI to accurately assess the bipolar bone loss seen in patients with anterior shoulder instability for predicting the presence of engaging, or off-track, lesions. This information can be used preoperatively to help guide the type of stabilization procedure performed on patients with anterior shoulder instability.

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