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

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BACKGROUND The role of post-reduction radiography in patients with shoulder dislocation remains controversial. Therefore, this retrospective study of 1076 cases of shoulder dislocation at a single center in Türkiye aimed to evaluate the role of post-reduction radiography in the detection of clinically significant fractures. MATERIAL AND METHODS Patients with radiographically confirmed anterior shoulder dislocation were included in the study, and their demographic data, mechanism of injury, pre- and post-reduction radiograph readings, reduction method, and patient outcome were recorded. The study analyzed patients who had pre- and post-reduction anterior-posterior and axillary shoulder radiographs. RESULTS During the 44-month study period, a total of 1076 patients were examined, and their pre- and post-reduction radiographs were reviewed by an independent radiologist. Of these patients, 27 (2.6%) had a fracture on their pre-reduction radiographs, while 32 (3.1%) had a fracture on their post-reduction radiographs. The difference between the 2 groups was not statistically significant (P=0.142). The study found that patients who did not undergo a post-reduction radiograph spent an average of 106 min in the emergency department, while patients who had the radiograph and were discharged spent an average of 237 min. The hospital stay of patients who had the radiograph was also significantly longer (P<0.01). CONCLUSIONS Our study supports that routine use of post-reduction radiographs in all cases of anterior shoulder dislocation may not be necessary and could potentially expose patients to unnecessary radiation exposure and healthcare costs. Shortening the examination time in the emergency department by not taking a follow-up radiograph will help prevent overcrowding.

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CASE: (1) A 69-year-old man sustained a proximal humeral fracture-dislocation. During emergency surgery, copious bleeding occurred. A pseudoaneurysm was identified 30 days postoperatively. (2) A 69-year-old man sustained a proximal humeral fracture and axillary artery injury. Physical examination demonstrated a cold but pink hand. Hemiarthroplasty and bypass vein grafting were performed. (3) An 86-year-old woman sustained a proximal humeral fracture and axillary artery injury. Her hand had turned cold and pale. Reverse shoulder arthroplasty and bypass vein grafting were performed. CONCLUSION: In cases of proximal humeral fractures with significant displacement, concomitant axillary artery injury must be assessed and if there is a high index of suspicion, prompt advanced imaging is necessary.

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BACKGROUND: Anterior shoulder dislocation (ASD) is a frequently observed musculoskeletal injury that is often encountered in the context of sports activities or as a result of trauma. Several magnetic resonance imaging (MRI) parameters have been previously investigated for the purpose of characterizing the anatomical features, which could potentially be responsible for the episodes of instability. These measurements have the potential to identify patients who are susceptible to dislocation. Consequently, ensuring the reliability and consistency of these measurements is crucial in the diagnosis and the management of athletic or traumatic shoulder injuries. METHODS: A group of four students, who had no previous experience in reading MRI series, were selected to perform radiographic measurements on specific parameters of MRI scans. These parameters were glenoid version, glenoid depth, glenoid width, humeral head diameter, humeral containing angle, and the ratio of humeral head diameter to glenoid diameter. The four participants conducted two distinct readings on a total of 28 sets of shoulder MRI scans. Simultaneously, the aforementioned measures were assessed by a consultant shoulder surgeon. RESULTS: A total of 1512 measurements were categorized into nine sets: eight from students' measurements (two per student) and one from the consultant. Intra-rater reliability assessed by the intra-class correlation (ICC) test indicated excellent or good reliability for all parameters (p < 0.05), with glenoid depth showing the highest (0.925) and humeral-containing angles the lowest (0.675) ICC value. Inter-rater correlation, also evaluated using ICC, demonstrated strong correlation (p < 0.05), with glenoid diameter having the highest ICC score (0.935) and glenoid depth the lowest (0.849). Agreement analysis, expressed by Cohen's Kappa test, revealed substantial agreement (p < 0.05) for all parameters, with humeral head diameter having the highest agreement (0.90) and humeral-containing angle the lowest (0.73). CONCLUSION: In this study, intra- and inter-rater MRI parameters are substantially concordant. Credibility comes from these reliability and agreement analyses' statistical significance. Glenoid diameter and depth are the most reliable intrarater and interrater, respectively. Best agreement was with the humeral-containing angle. These data demonstrate repeatability and clinical relevance. LEVEL OF EVIDENCE: Level IV.

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CASE: A 34-year-old man was a restrained passenger involved in a high-speed rollover motor vehicle crash. The patient sustained a type 5 AC joint separation, severely comminuted intra-articular glenoid fracture with extension to the coracoid process base, displaced open scapular body fracture, a posterior shoulder dislocation of the glenohumeral joint, and a 2-part proximal humerus fracture. CONCLUSION: To our knowledge, this is the first report describing this injury pattern involving the superior shoulder suspensory complex with an associated open proximal humerus fracture-dislocation.

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BACKGROUND: Management of acute shoulder dislocation in the emergency department (ED) is common. OBJECTIVE: This study describes the rate, risk factors, and length of stay (LOS) associated with shoulder dislocation reduction failure in the ED. METHODS: The study was a retrospective case-control study of patients 18 years and older presenting to the ED with acute shoulder dislocation who underwent attempted reduction. Patients with successful reduction on post-reduction first confirmatory imaging are compared with those requiring multiple attempts. RESULTS: Of 398 ED encounters when a shoulder reduction was attempted in the ED, 18.8% (75/398 [95% CI 15.2-22.9%]) required multiple reduction attempts. Patients with successful reduction on first confirmatory imaging were more commonly male (80.2% [95% CI 75.6-84.3%] vs. 68.0% [95% CI 56.8-77.8%]; p = 0.0220), discharged home from the ED (95.4% [95% CI 92.6-97.3%] vs. 84.0% [95% CI 74.4-91.0%]; p = 0.0004), reduced using a traction/countertraction technique (42.1% [95% CI 36.8-47.6%] vs. 29.3% [95% CI 19.9-40.4%]; p = 0.0415), and less likely to have a pre-reduction fracture (26.0% [95% CI 21.4-31.0%] vs. 45.3% [95% CI 34.4-56.7%]; p = 0.0010). Mean length of stay (LOS) for those with successful reduction on first confirmatory imaging was 2 hours and 8 minutes shorter than for those with more than one attempt (p < 0.001). CONCLUSIONS: The rate of failed first-pass reduction is higher than previously reported. Furthermore, the ED LOS was significantly longer in patients requiring multiple attempts. Knowledge of the failure rate and risk factors may raise physician awareness and guide future studies evaluating approaches for verification of reduction success.

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BACKGROUND: The extent of measurement errors of statistical shape models that predict native glenoid width based on glenoid height to subsequently determine the amount of anterior glenoid bone loss is unclear. Therefore, the aim of this study was to (1) create a statistical shape model based on glenoid height and width measured on 3-dimensional computed tomography (3D-CT) and determine the accuracy through measurement errors and (2) determine measurement errors of existing 3D-CT statistical shape models. MATERIALS AND METHODS: A retrospective cross-sectional study included all consecutive patients who underwent CT imaging before undergoing primary surgical treatment of traumatic anterior shoulder dislocation between 2007 and 2022 at the Tohoku University Hospital and affiliated hospitals. Patients were included when instability was unilateral and CT scans of both the injured and contralateral uninjured shoulder were available. 3D segmentations were created and glenoid height and width of the injured and contralateral uninjured side (gold standard) were measured. Accuracy was determined through measurement errors, which were defined as a percentage error deviation from native glenoid width (contralateral uninjured glenoid), calculated as follows: measurement error = [(estimated glenoid width with a statistical shape model - native glenoid width) / native glenoid width] × 100%. A linear regression analysis was performed to create a statistical shape model based on glenoid height according to the formula: native glenoid width = a × glenoid height + b. RESULTS: The diagnosis and procedure codes identified 105 patients, of which 69 (66%) were eligible for inclusion. Glenoid height demonstrated a very strong correlation (r = 0.80) with native glenoid width. The linear regression formula based on this cohort was as follows: native glenoid width = 0.75 × glenoid height - 0.61, and it demonstrated an absolute average measurement error of 5% ± 4%. The formulas by Giles et al, Chen et al and Rayes et al demonstrated absolute average measurement errors of 10% ± 7%, 6% ± 5%, and 9% ± 6%, respectively. CONCLUSION: Statistical shape models that estimate native glenoid width based on glenoid height demonstrate unacceptable measurement errors, despite a high correlation. Therefore, great caution is advised when using these models to determine glenoid bone loss percentage. To minimize errors caused by morphologic differences, preference goes to methods that use the contralateral side as reference.

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In unstable shoulders, excessive anteroinferior position of the humeral head relative to the glenoid can lead to a dislocation. Measuring humeral head position could therefore be valuable in quantifying shoulder laxity. The aim of this study was to measure (1) position of the humeral head relative to the glenoid and (2) joint space thickness during passive motion in unstable shoulders caused by traumatic anterior dislocations and in contralateral uninjured shoulders. A prospective cross-sectional CT-study was performed in patients with unilateral anterior shoulder instability. Patients underwent CT scanning of both injured and uninjured side in supine position (0° abduction and 0° external rotation) and in 60°, 90°, and 120° of abduction with 90° of external rotation without an external load. Subsequently, 3D virtual models were created of the humerus and the scapula to create a glenoid coordinate system to identify poster-anterior, inferior-superior, and lateral-medial position of the humeral head relative to the glenoid. Joint space thickness was defined as the average distance between the subchondral bone surfaces of the humeral head and glenoid. Fifteen consecutive patients were included. In supine position, the humeral head was positioned more anteriorly (p = 0.004), inferiorly (p = 0.019), and laterally (p = 0.021) in the injured compared to the uninjured shoulder. No differences were observed in any of the other positions. A joint-space thickness map, showing the bone-to-bone distances, identified the Hill-Sachs lesion footprint on the glenoid surface in external rotation and abduction, but no differences on average joint space thickness were observed in any position.

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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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BACKGROUND: The shoulder joint is the most commonly dislocated joint in the human body, and the recurrence rate exceeds 50% after nonsurgical treatment. Although surgical treatment reduces the recurrence rate, there is controversy regarding the optimal surgical approach. Previous studies suggest that the Latarjet procedure yields favourable outcomes for specific populations at risk of recurrence, such as competitive athletes with significant glenoid defects. However, most of the existing related research consists of nonrandomized controlled trials with small sample sizes, and there is a lack of strong evidence regarding the efficacy and safety of the Latarjet procedure. METHODS: The PubMed, Embase, Cochrane Library, and Web of Science databases were systematically searched. Athletes with ≥ 20% glenoid defects were selected for inclusion. The following data were extracted: general patient information, instability rates, return to sports (RTS) rates, imaging features (graft positioning rate and graft healing rate), functional assessments [Rowe score, Athletic Shoulder Outcome Scoring System(ASOSS), visual analogue scale (VAS), forward flexion function, and external rotation function], and complications. RESULTS: After excluding suspected duplicate cases, a total of 5 studies were included in this meta-analysis. The studies involved a total of 255 patients, including 237 males (93%) and 18 females (7%). The average age at the time of surgery was 25.4 ± 8.5 years. All the studies had a minimum follow-up period of 2 years, with an average follow-up time of 48.7 ± 18.9 months. The pooled rate of return to sport (RTS) was 94.3% (95% CI: 87.3%, 98.8%), and 86.1% (95% CI: 78.2%, 92.5%) of patients returned to their preoperative level of activity. The pooled redislocation rate was 1.1% (95% CI: 0%, 3.8%). Regarding the imaging results, the combined graft retention rate was 92.1% (95% CI: 88.1%, 95.5%), and the graft healing rate was 92.1% (95% CI: 88%, 95.4%). Postoperative functional evaluation revealed that the combined Rowe score, ASOSS score, and VAS score were 93.7 ± 6.5 points, 88.5 ± 4.4 points, and 1.1 ± 10 points, respectively. The forward flexion and external rotation angles were 170.9 ± 6.9 degrees and 65.6 ± 4.5 degrees, respectively. After excluding one study with unclear complications, the combined complication rate was 9.4% (95% CI: 1.0%, 23.6%). CONCLUSION: For athletes with shoulder instability and a total of ≥ 20% glenoid bone defects, the Latarjet procedure can achieve excellent functional outcomes, with the majority of patients returning to preoperative levels of sports activity. This procedure also leads to a low recurrence rate. Therefore, the Latarjet procedure has been proven to be a safe and effective treatment.

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BACKGROUND: To evaluate the outcome of shoulder arthroscopy-assisted implantation of three-dimensional (3D)-printed titanium pads for recurrent shoulder dislocation with glenoid bone defects. METHODS: From June 2019 to May 2020, the clinical efficacy of 3D printed titanium pad implantation assisted by shoulder arthroscopy, for the treatment of recurrent shoulder dislocations with shoulder glenoid defects was retrospectively analyzed. The American Shoulder and Elbow Surgeons (ASES) shoulder, Rowe, and Constant scores were recorded before surgery and at 3 months, 6 months, 1 year, and 2 years after surgery. 3D computed tomography (CT) and magnetic resonance imaging were used to evaluate the location of the glenoid pad, bone ingrowth, joint degeneration, and osteochondral damage. RESULTS: The mean age of the 12 patients was 21.4 (19-24) years and the mean follow-up time was 27.6 (24-35) months. The Visual Analog Scale score significantly improved from 5.67 ± 1.98 preoperatively to 0.83 ± 0.58 postoperatively (p = 0.012). The postoperative ASES score was significantly increased to 87.91 ± 3.47 compared with preoperative ASES score (46.79 ± 6.45) (p < 0.01). Rowe and Constant scores also improved from 22.5 ± 12.34 and 56.58 ± 7.59 preoperatively to 90.83 ± 4.69 and 90.17 ± 1.89 at 2 years postoperatively, respectively. CT performed 2 years after surgery showed that the pad perfectly replenished the bone-defective part of the shoulder glenoid and restored the articular surface curvature of the shoulder glenoid in the anterior-posterior direction, and the bone around the central riser of the pad was tightly united. Magnetic resonance imaging 2 years after surgery showed that the humeral head osteochondral bone was intact, and there was no obvious osteochondral damage. CONCLUSIONS: 3D printed titanium pads are a reliable, safe, and effective surgical procedure for treating recurrent shoulder dislocations with glenoid bone defects.

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BACKGROUND: Primary glenohumeral osteoarthritis is associated with both excessive posterior humeral subluxation (PHS) and excessive glenoid retroversion in 40% of cases. These morphometric abnormalities are a particular issue because they may be responsible for a deterioration in long-term clinical and radiologic outcomes. The aim of this study was to perform a computed tomographic (CT) analysis of patients who underwent total shoulder arthroplasty (TSA) for primary osteoarthritis (OA) with B2-, B3-, or C-type glenoids in whom an attempt was made to correct for excessive glenoid retroversion and excessive posterior humeral subluxation intraoperatively. MATERIAL: We performed a retrospective, single-center study including 62 TSA patients with a preoperative PHS of the glenohumeral joint (31 men, 31 women, 70 ± 9 years) between January 2000 and January 2014. Glenoids were classified as B2 (32 cases), B3 (13 cases), or C (17 cases). Glenoid retroversion was corrected by anterior asymmetric reaming. Patients were reviewed for clinical and CT scan assessment with a mean follow-up of 8.3 years (minimum 5 years). At final follow-up, the CT images were reconstructed in the scapular plane. A PHS index >65% defined persistence. RESULTS: The revision-free rate was estimated at 93%. Correlation between PHS and retroversion was moderate preoperatively (ρ = 0.58) and strong at final follow-up (ρ = 0.73). Postoperative CT scans on average showed a surgical correction of PHS compared to preoperatively (79% vs. 65% respectively, P < .05) and retroversion (20° vs. 10° respectively, P < .05). At final follow-up, 25 of 62 patients had a persistence in the 2-dimensional (2D) model and 41 of 62 in the corrected 2D model. Persistence of PHS had no influence on clinical outcomes but did demonstrate a significantly higher glenoid loosening rate (20% vs. 59%, P < .05). CONCLUSION: Correlation between PHS and retroversion was moderate preoperatively and strengthened at long-term follow-up. Anterior asymmetric reaming allowed for a surgical improvement of both PHS and retroversion, but it was not sufficient to maintain a correction over time. Glenoid loosening was more frequent in case of PHS persistence but seemingly without clinical relevance.

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BACKGROUND: The etiology of humeral posterior subluxation remains unknown, and it has been hypothesized that horizontal muscle imbalance could cause this condition. The objective of this study was to compare the ratio of anterior-to-posterior rotator cuff and deltoid muscle volume as a function of humeral subluxation and glenoid morphology when analyzed as a continuous variable in arthritic shoulders. METHODS: In total, 333 computed tomography scans of shoulders (273 arthritic shoulders and 60 healthy controls) were included in this study and were segmented automatically. For each muscle, the volume of muscle fibers without intramuscular fat was measured. The ratio between the volume of the subscapularis and the volume of the infraspinatus plus teres minor (AP ratio) and the ratio between the anterior and posterior deltoids (APdeltoid) were calculated. Statistical analyses were performed to determine whether a correlation could be found between these ratios and glenoid version, humeral subluxation, and/or glenoid type per the Walch classification. RESULTS: Within the arthritic cohort, no statistically significant difference in the AP ratio was found between type A glenoids (1.09 ± 0.22) and type B glenoids (1.03 ± 0.16, P = .09), type D glenoids (1.12 ± 0.27, P = .77), or type C glenoids (1.10 ± 0.19, P > .999). No correlation was found between the AP ratio and glenoid version (ρ = -0.0360, P = .55) or humeral subluxation (ρ = 0.076, P = .21). The APdeltoid ratio of type A glenoids (0.48 ± 0.15) was significantly greater than that of type B glenoids (0.35 ± 0.16, P < .01) and type C glenoids (0.21 ± 0.10, P < .01) but was not significantly different from that of type D glenoids (0.64 ± 0.34, P > .999). When evaluating both healthy control and arthritic shoulders, moderate correlations were found between the APdeltoid ratio and both glenoid version (ρ = 0.55, P < .01) and humeral subluxation (ρ = -0.61, P < .01). CONCLUSION: This in vitro study supports the use of software for fully automated 3-dimensional reconstruction of the 4 rotator cuff muscles and the deltoid. Compared with previous 2-dimensional computed tomography scan studies, our study did not find any correlation between the anteroposterior muscle volume ratio and glenoid parameters in arthritic shoulders. However, once deformity occurred, the observed APdeltoid ratio was lower with type B and C glenoids. These findings suggest that rotator cuff muscle imbalance may not be the precipitating etiology for the posterior humeral subluxation and secondary posterior glenoid erosion characteristic of Walch type B glenoids.

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BACKGROUND: The glenoid track concept for shoulder instability primarily describes the medial-lateral relationship between a Hill-Sachs lesion and the glenoid. However, the Hill-Sachs position in the craniocaudal dimension has not been thoroughly studied. HYPOTHESIS: Hill-Sachs lesions with greater inferior extension are associated with increased risk of recurrent instability after primary arthroscopic Bankart repair. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: The authors performed a retrospective analysis of patients with on-track Hill-Sachs lesions who underwent primary arthroscopic Bankart repair (without remplissage) between 2007 and 2019 and had a minimum 2-year follow-up. Recurrent instability was defined as recurrent dislocation or subluxation after the index procedure. The craniocaudal position of the Hill-Sachs lesion was measured against the midhumeral axis on sagittal magnetic resonance imaging (MRI) using either a Hill-Sachs bisecting line through the humeral head center (sagittal midpoint angle [SMA], a measure of Hill-Sachs craniocaudal position) or a line tangent to the inferior Hill-Sachs edge (lower-edge angle [LEA], a measure of Hill-Sachs caudal extension). Univariate and multivariate regression were used to determine the predictive value of both SMA and LEA for recurrent instability. RESULTS: In total, 176 patients were included with a mean age of 20.6 years, mean follow-up of 5.9 years, and contact sport participation of 69.3%. Of these patients, 42 (23.9%) experienced recurrent instability (30 dislocations, 12 subluxations) at a mean time of 1.7 years after surgery. Recurrent instability was found to be significantly associated with LEA >90° (ie, Hill-Sachs lesions extending below the humeral head equator), with an OR of 3.29 (P = .022). SMA predicted recurrent instability to a lesser degree (OR, 2.22; P = .052). Post hoc evaluation demonstrated that LEA >90° predicted recurrent dislocations (subset of recurrent instability) with an OR of 4.80 (P = .003). LEA and SMA were found to be collinear with Hill-Sachs interval and distance to dislocation, suggesting that greater LEA and SMA proportionally reflect lesion severity in both the craniocaudal and medial-lateral dimensions. CONCLUSION: Inferior extension of an otherwise on-track Hill-Sachs lesion is a highly predictive risk factor for recurrent instability after primary arthroscopic Bankart repair. Evaluation of Hill-Sachs extension below the humeral equator (inferior equatorial extension) on sagittal MRI is a clinically facile screening tool for higher-risk lesions with subcritical glenoid bone loss. This threshold for critical humeral bone loss may inform surgical stratification for procedures such as remplissage or other approaches for at-risk on-track lesions.

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PURPOSE: The Latarjet procedure is traditionally used to treat chronic anterior shoulder instability associated with glenoid bone loss. However, few series have analyzed outcomes in a female-only population. The objective of this study was to evaluate the clinical and radiological outcomes of a Latarjet bone block in this specific population. METHODS: This single-center retrospective study included 15 women (mean age 35 ± 11.3; 19-60) reviewed with a minimum follow-up of 2 years. The procedure was performed using the open bone block screw technique (n = 7) or by arthroscopy with cortical button (n = 8). Clinical evaluation was based on active range of motion measurements, Rowe and Walch-Duplay scores, and subjective shoulder value (SSV). Radiographic analysis explored bone block healing at the last follow-up. RESULTS: At a mean follow-up of 48 months (32-86), no recurrence was reported. The mean Rowe score was 91 points (70-100), Walch-Duplay 90 points (60-100), and SSV 87% (70-100). The active mobilities reached 169° (± 9°) in elevation, 57° (± 15°) in external rotation at side, and 89° (± 6°) in abduction. The return-to-sport rate was 91%. Five patients experienced persistent anterior pain, with screws requiring hardware removal in 2 (p = 0.02). Radiological assessment detected one case of nonunion (7%). CONCLUSION: Women treated with the Latarjet procedure experienced satisfactory midterm clinical outcomes. The arthroscopic technique using cortical button fixation seems to avoid residual anterior pain requiring hardware removal.

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INTRODUCTION: The Latarjet procedure treats anterior instability of the shoulder and is based on a triple anterior lock, where the conjoint tendon straps the lower third of the subscapularis muscle. Excessive posterior translation of the humeral head is a known risk factor for shoulder osteoarthritis. No in vivo study has investigated the effect of the bone block on the posterior static translation of the humeral epiphysis. The purpose of this study was to evaluate the effect of the bone block on the static posterior translation of the humeral head. The hypothesis was that this procedure increased this translation. MATERIALS AND METHODS: This retrospective study included patients treated arthroscopically for anterior shoulder instability by a double-button Latarjet. An independent examiner analyzed the CT scans preoperatively, at 15 days, and at least 6 months postoperatively according to a standardized protocol. The analysis focused on the position of the bone block in the axial and coronal planes relative to the glenoid. The posterior translation was automatically calculated using the Blueprint© planning software. RESULTS: Thirty-five patients were included with a mean age of 25 years (16-43), according to a 4M/1F sex ratio. The graft was perfectly flush to the subchondral bone in 63% (n=22) of cases and subequatorial in 91% (n=32). Preoperative posterior humeral translation was 52%. The mean immediate postoperative posterior humeral translation was 56%, and 57% at more than 6 months. The change in mean posterior humeral translation between preoperative/6 months was +0.94% [-20%; +12%] (p=0.29) and immediate postoperative/6 months +0.34% [-18%; +15%] (p=0.84). Gender, hypermobility and the axial position of the bone block did not influence the change in posterior humeral translation. The equatorial position of the bone block appeared to increase posterior humeral translation by +10%±5.2% [-0.427; 20.823] (p=0.07). CONCLUSION: This work refutes our initial hypothesis. The change in static posterior humeral translation after arthroscopic Latarjet bone block remains stable at more than 6 months of follow-up. This procedure does not alter the anatomical position of the humeral head in relation to the glenoid. On the other hand, a more cranial positioning of the bone block could have an influence. LEVEL OF EVIDENCE: IV.

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PURPOSE: Estimation of glenoid bone loss in CT scans following shoulder dislocation is required to determine the type of surgery needed to restore shoulder stability. This paper presents a novel automatic method for the computation of glenoid bone loss in CT scans. METHODS: The model-based method is a pipeline that consists of four steps: (1) computation of an oblique plane in the CT scan that best matches the glenoid face orientation; (2) selection of the glenoid oblique CT slice; (3) computation of the circle that best fits the posteroinferior glenoid contour; (4) quantification of the glenoid bone loss. The best-fit circle is computed with newly defined Glenoid Clock Circle Constraints. RESULTS: The pipeline and each of its steps were evaluated on 51 shoulder CT scans (44 patients). Ground truth oblique slice, best-fit circle, and glenoid bone loss measurements were obtained manually from three clinicians. The full pipeline yielded a mean absolute error (%) for the bone loss deficiency of 2.3 ± 2.9 mm (4.67 ± 3.32%). The mean oblique CT slice selection difference was 1.42 ± 1.32 slices, above the observer variability of 1.74 ± 1.82 slices. The glenoid bone loss deficiency measure (%) on the ground truth oblique glenoid CT slice has a mean average error of 0.54 ± 1.03 mm (4.76 ± 3.00%), close to the observer variability of 0.93 ± 1.40 mm (2.98 ± 4.97%). CONCLUSION: Our pipeline is the first fully automatic method for the quantitative analysis of glenoid bone loss in CT scans. The computed glenoid bone loss report may assist orthopedists in selecting and planning surgical shoulder dislocation procedures.

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Failure of closed reduction of anterior glenohumeral joint dislocation is infrequent. It can be secondary to osseous (e.g., fracture fragments or Hill-Sachs lesion) or soft tissue (e.g., labrum or rotator cuff tendon) impediments. Herein, we present a case of a prolonged irreducible glenohumeral joint secondary to a posterolaterally dislocated and incarcerated long head of the biceps tendon after an episode of anterior instability, highlight the utility of MR imaging for guiding management, and review the literature of this sporadic diagnosis.

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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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