Die posteriore Schulterinstabilität (PSI) kann funktionelle Ursachen haben, die sich grundlegend von denen unterscheiden, die mit einer strukturellen Instabilität verbunden sind. Eine funktionelle PSI entsteht durch neuromuskuläre Fehlaktivierungsmuster anstelle von strukturellen Defiziten. Dieser Zustand weist ein komplexes klinisches Bild auf, das durch Symptome wie Schmerzen, Beschwerden bei Überkopfaktivitäten und Episoden von Subluxation oder vollständiger Luxation gekennzeichnet ist. Das Verständnis der verfügbaren Behandlungsmethoden für eine funktionelle PSI ist entscheidend für die Wiederherstellung der Funktion und die Vorbeugung von Rückfällen. Um die richtige Behandlung für eine posteriore Schulterinstabilität auszuwählen, ist es wichtig, zwischen einer strukturellen und einer funktionellen Instabilität zu differenzieren. Eine funktionelle Instabilität der hinteren Schulter erfordert einen sorgfältigen und vielschichtigen Ansatz bei der Diagnose und Behandlung. Ärzte müssen die entsprechenden Symptome erkennen und je nach Ursache eine entsprechende spezifische Therapie einleiten. Die Rehabilitation bleibt ein Eckpfeiler der Behandlung, wobei der Schwerpunkt weiterhin auf der Notwendigkeit individueller Rehabilitationsprogramme liegt, die die neuromuskulären Aktivierungsmuster verbessern. Für optimale Ergebnisse bei der Behandlung der funktionellen PSI gewinnt die Integration von fachkundigen physiotherapeutischen Ansätzen und moderner Technologie wie z. B. der funktionellen Elektrostimulation (FES) in der aktuellen orthopädischen Praxis zunehmend an Bedeutung. Ziel dieser Arbeit ist es, die entsprechenden Therapieoptionen zu beleuchten.

Outcomes of surgical treatment of partial-thickness rotator cuff tears (PTRCTs) are underreported. This study investigates (1) arthroscopic repair techniques for partial supraspinatus (SSP) tears and (2) outcomes based on tear location (articular-side vs. bursal-side vs. intratendinous) in a large multicenter cohort. As part of a cohort study across 19 centers (ARCR_Pred study), adult patients with primary arthroscopic repair of a PTRCT involving the SSP tendon were prospectively enrolled over an 18-month period beginning in June 2020, operated, and followed-up for 24 months. Tear location (articular-side, bursal-side, intratendinous) and surgical technique (tear completion, suture configuration) were documented. Functional (pain, strength, Range of Motion [ROM], Constant -Murley Score [CMS]) and patient-reported (Subjective Shoulder Value [SSV], quality of life [Eq. 5D utility]) outcomes were assessed at baseline, 6, 12, and 24 months. Adverse events were recorded through 24 months. Baseline factors affecting repair techniques were explored. Outcomes and adverse events were compared across tear locations. The ARCR_Pred cohort of 973 patients included 147 partial tears (15.7

Shoulder instability is increasingly prevalent among pediatric and adolescent populations due to growing participation in competitive sports at younger ages. However, the literature remains challenging to apply clinically, as it often fails to distinguish between different developmental stages, leading to potential overtreatment or undertreatment. This review aims to categorize types of shoulder instability in young patients, propose a diagnostic approach, and summarize current management strategies based on available evidence. Shoulder dislocations are rare in skeletally immature patients, with the highest risk observed in those aged 14–18 years. Younger children, particularly those under ten, are less prone to dislocations due to the relative strength of their ligaments compared to bone. Diagnosis relies on history, physical examination, and imaging modalities such as radiographs, computed tomography (CT), and magnetic resonance imaging (MRI). Special attention is required for functional posterior instability, which is frequently misdiagnosed. Treatment decisions—whether conservative or surgical—remain controversial. Conservative management, including immobilization and rehabilitation, is the first-line approach for primary anterior dislocations, particularly in children under 12. However, adolescents aged 12–16 face a high risk of recurrence, making early surgical stabilization a viable option. Arthroscopic stabilization is the preferred surgical technique, especially for athletes. In cases of recurrent instability with significant glenoid bone loss, the Latarjet procedure or iliac crest bone grafting may be indicated. Posterior instability, though rare, follows treatment principles similar to those in adults, with a primary emphasis on rehabilitation. Functional posterior instability responds well to neuromuscular electrical stimulation. Multidirectional instability, often associated with ligamentous laxity, is primarily managed nonoperatively, but surgical stabilization may be necessary if symptoms persist. In conclusion, pediatric shoulder instability is complex and requires an individualized approach. Understanding age-specific anatomical and physiological differences is crucial for optimizing treatment outcomes and preventing long-term complications. Level 5.

Abstract Purpose To evaluate the long‐term outcomes of arthroscopic Bankart repair with additional posteroinferior capsular plication in patients with anterior shoulder instability and hyperlaxity, and to compare the outcomes of posteroinferior capsular plication using suture‐only fixation versus suture anchor fixation. Methods In this retrospective study, patients were included who underwent arthroscopic Bankart repair and additional posteroinferior capsular plication for anterior shoulder instability and hyperlaxity (type B3) between 2006 and 2014 at our institution. Primary outcome was recurrent instability. Secondary outcomes were Subjective Shoulder Value (SSV), visual analog scale (VAS), Constant score (CS), Western Ontario Shoulder Instability Index (WOSI) and Rowe score, as well as return to sport. Results Of 54 included shoulders, 33 shoulders in 32 patients (61.1%) were evaluated after a mean follow‐up of 13.2 ± 2.3 years. The overall recurrence rate was 18.2% (6/33). The total revision rate was 9.1%, with two revisions due to recurrent instability and one due to posteroinferior knot impingement. The number of preoperative dislocations correlated negatively with the CS (ρ = −0.425, p = 0.019) and the WOSI (ρ = −0.471, p = 0.009). A total of 97% of all patients returned to sports, with 57.6% returning to 90%–100% of their preoperative sports activity. Posteroinferior capsular plication using suture‐only fixation was associated with a higher recurrence rate (3/6, 50%), compared to the use of suture anchor fixation (3/27, 11.1%; p = 0.025). Conclusion Arthroscopic Bankart repair combined with posteroinferior capsular plication provided durable long‐term shoulder function and reliable return to sport in patients with anterior instability and hyperlaxity. Performing the posteroinferior plication with suture anchor fixation might be associated with lower recurrence rates compared to suture‐only plication. Clinical outcomes declined with an increasing number of preoperative dislocations. Level of Evidence Level III, cohort study.

BACKGROUND:Surgical fixation of Rockwood type 5 acromioclavicular (AC) dislocations can restore coracoclavicular (CC) distance radiographically, but whether the CC ligaments regain their native morphology is unknown. PURPOSE:To evaluate postoperative CC ligament thickness on magnetic resonance imaging (MRI) compared with the contralateral side and to assess its relationship with functional outcomes. STUDY DESIGN:Cohort study; Level of evidence, 2. METHODS:A total of 46 patients (28 hook plate, 18 EndoButton) with ≥24 months of follow-up received bilateral radiographs and sagittal oblique MRI sequences. CC distance and conoid and trapezoid ligament thickness were measured, with contralateral shoulders serving as individualized controls. Functional outcomes included the visual analog scale, Constant, University of California Los Angeles, and Quick Disabilities of the Arm, Shoulder and Hand scores. RESULTS:Surgical shoulders showed increased CC distance and reduced trapezoid and total CC thickness, whereas conoid thickness was comparable to that of the contralateral side. Neither fixation method achieved complete restoration of CC ligament thickness. Functional scores were favorable across all patients, with no clinically relevant differences between fixation techniques. The overall rate of complications was similar between groups; however, complication patterns differed, with AC arthritis/osteolysis more common after hook plate fixation and implant-related complications more frequent after EndoButton fixation. Ligament thickness parameters did not correlate with patient-reported outcomes. CONCLUSION:To the authors' knowledge, this is the first contralateral-controlled MRI study to quantify CC ligament thickness after surgical treatment of Rockwood type 5 AC dislocations. Despite incomplete restoration of ligament morphology, functional recovery was favorable, suggesting that clinical recovery may not be strictly dependent on complete anatomic restoration.

Purpose The Shoulder Instability Registry (SIR) was established in 2019 to systematically capture and monitor outcomes following surgical treatment of shoulder instability (SI). The aim of this cohort profile is to describe the purpose, design, data structure and baseline characteristics of the SIR, and to outline how the registry supports longitudinal assessment of safety, functional recovery, quality of life and patient-reported outcomes after surgical treatment of SI.Participants The registry includes all patients treated surgically for SI. Data collection includes medical history of instability, surgical techniques and intraoperative findings. Clinical assessments include range of motion, instability-specific tests, hyperlaxity signs, Constant Score, subjective shoulder value and SI-specific scores such as the ROWE Score and the Western Ontario Shoulder Instability Index. Radiological evaluations included initial and follow-up imaging via X-rays and CT to assess bony lesions and SI-related arthropathy, as well as MRI for soft tissue injuries. Data are documented preoperatively, at 6 months and at 24 months postoperatively. Although the SIR is an observational cohort rather than a randomised clinical trial, treatment effectiveness is evaluated through longitudinal changes in validated patient-reported outcomes, clinical performance measures and imaging findings.Findings to date Between January 2019 and December 2024, 668 patients have been registered (mean age 31 years, 82% men, mean body mass index of 25). According to the American Association of Anesthesiology (ASA) Classification, 66% of patients were classified as ASA I, 33% as ASA II and only 1% as ASA III. 69% of admissions were due to accidents and 31% due to illness. Mean surgery duration was 75 min, and the median hospital stay was 2 days. 38% of patients were insured privately and had general insurance in 62%. 85% of cases were treated arthroscopically, and 15% were treated openly. Baseline clinical scores showed a mean Constant Score of 77 points, mean subjective shoulder value of 49%, mean ROWE Score of 46 points and mean Western Ontario Shoulder Instability Index of 53. Based on Gerber’s classification, 68% of cases were type B2, 29% B3, 2% B5 and fewer than 2% were classified as B4 or B1. 85% of cases suffered from anterior instability, while only 13% experienced posterior instability, the remaining 2% showed multidirectional instability. Among posterior cases, Moroder’s classification identified 58% as type B2, 19% as A2, 7% as A1, 6% as B1, 6% as C1 and 4% as C2. Regarding osteochondral lesions, 20% showed none, 31% showed a glenoid defect, 54% showed a Hill-Sachs lesion and 13% showed a cartilage defect. Scheibel’s classification identified glenoid defects as type 3a in 38% of cases, type 2 in 24%, type 1a in 13% of cases, type 3b in 11%, type 1b in 8% and type 1c in 5% of cases. Positive Gagey and Walch signs were observed in 29% and 27% of cases, respectively. Dislocations presented as primary events in 24% of cases, while 76% were recurrent. Surgical interventions included 459 (70%) Bankart repairs, 6 Bankart plus repairs (<1%) and 108 (16%) Remplissage procedures for soft tissue stabilisation. Bony reconstructions included 52 fragment fixations (8%), 41 coracoid transfers (6%) and 87 iliac crest bone grafts (13%). Additional pathologies were addressed in 533 cases (81%), while 38 cases required revision surgery.Future plans We will continue prospectively enrolling and monitoring patients that receive surgical treatment of SI. There are no current plans to halt the data collection in the near future, thereby consistently increasing the number of patients in the registry. A larger availability of data will additionally allow us to apply machine learning modelling and develop risk-prediction tools with the goal of aiding surgical decision making.

Clinicians rely on the assessment of joint range of motion to determine the necessity of clinical interventions and to track rehabilitation progress. They often perform visual assessments of these joint angles due to limited time for longer but more accurate methods. Markerless monocular human pose estimation methods could help reduce the workload of physicians in clinical practice, allow patients to conduct regular assessments remotely, and be used to provide reliable assessments in the absence of expert raters, but they have not been validated extensively on clinical populations. We measured the elbow flexion and extension ranges of motion of 46 patients with shoulder and elbow pathologies. These values were assessed by RTMW and HSMR, two different monocular pose estimation methods, and an experienced physician who performed visual assessments. A state-of-the-art passive-marker optical motion capture system was used as the reference system. For elbow flexion, HSMR outperformed visual assessment. HSMR had a higher concordance correlation coefficient of 0.92 and a lower minimal detectable change of 6.74° as determined by a concordance analysis and a linear mixed-effects model. Conversely, for elbow extension, visual assessment outperformed both markerless methods. RTMW was the best-performing markerless method with a concordance correlation coefficient of 0.83 and a minimal detectable change of 7.93°. Thus, HSMR represented a viable alternative to visual assessment for measuring elbow flexion range of motion in a clinical population, but neither RTMW nor HSMR offered an improvement over visual assessment for measuring elbow extension range of motion.

Background: Glenoid inclination influences glenohumeral biomechanics. Superior inclination has been associated with superior humeral head migration and the rocking-horse phenomenon in anatomic total shoulder arthroplasty (aTSA). While surgical correction of glenoid inclination has been extensively investigated, it remains unknown whether commercially available glenoid components incorporate intrinsic inclination as a design characteristic. Purpose: To quantify the intrinsic inclination of contemporary glenoid components used in aTSA. Methods: A cross-sectional three-dimensional geometric analysis was performed using a manufacturer-independent preoperative planning platform. All commercially available anatomic glenoid components contained within the mediCAD® 3D Shoulder implant library were evaluated. Glenoid component inclination was measured in the central coronal plane as the angle between the articular surface and the vertical reference plane of the virtual three-dimensional environment using a standardized measurement protocol. Additionally, implant height was measured for the available sizes of each system. Measurements were performed independently by two observers, and intra- and interobserver reliability was assessed using the intraclass correlation coefficient (ICC). Results: A total of 111 glenoid components representing 26 implant systems from 14 manufacturers were analyzed. The intra- and interobserver reliability for the inclination parameter was excellent (ICC = 0.89–0.99). Twenty of the 26 systems (76.9%) demonstrated neutral intrinsic inclination (0°), whereas six systems (23.1%) exhibited non-neutral inclination ranging from +1.9° (superior inclination) to −4.4° (inferior inclination). Within individual implant systems, inclination showed only minor variation across component sizes. Conclusion: Contemporary glenoid component designs differ only slightly in intrinsic inclination, as most systems exhibit a neutral (0°) inclination. Given the usual superior native glenoid inclination in osteoarthritic shoulders, neutral implant geometry alone may not always achieve the desired postoperative orientation without corrective reaming.

BACKGROUND:In reverse total shoulder arthroplasty (rTSA), glenoid component inclination critically influences complications and implant performance. Current literature predominantly advocates for neutral or 0° inclination referenced to the supraspinatus fossa in order to avoid superior tilt which may lead to loosening. However, the influence of resting scapular rotation (RSR) on the effectively obtained inclination relative to the global reference system (gravity) remains poorly defined. This study aims to address this gap by evaluating the impact of RSR on global glenoid component inclination following rTSA. METHODS:This retrospective cohort included 93 consecutive patients who underwent rTSA with 3D preoperative planning and patient-specific instrumentation (PSI) for baseplate placement targeting 0° inclination. Standardized pre- and postoperative true anteroposterior radiographs were obtained with a vertical plumb line aligned to gravity. Measured parameters included scapular rotation angle (SRA), humeral abduction resting angle (HARA), scapulohumeral abduction resting angle (S-HARA), glenoid inclination angle (GIA), global glenoid inclination (GGI), and arthroplasty scapulohumeral abduction resting angle (AS-HARA). Interrater reliability was assessed using intraclass correlation coefficients (ICC). The effect of preoperative RSR on postoperative GGI was evaluated. Correlations among radiographic parameters and associations with clinical outcomes at 9 and 26 weeks were analyzed using multiple regression. RESULTS:Interrater reliability for the measured parameters was excellent (ICC=0.953-0.989). SRA varied widely from 14° upward rotation to 42° downward rotation with a mean of -15±9°. Three reproducible SRA types were identified, which remained mostly constant postoperatively. Despite a targeted glenoid inclination angle of 0°, GGI differed significantly with a mean of -18±10° and a range from 1 to -53° (p<0.0001) and demonstrated a strong correlation with SRA (r=0.77). Preoperatively, S-HARA averaged 113±10° and HARA 7±8°; postoperatively, S-HARA 117±10°, HARA 7±8°, and AS-HARA 116±10°. At 9 weeks, higher postoperative AS-HARA and S-HARA were associated with better ASES Index Scores, whereas by 26 weeks patients had recovered regardless. CONCLUSION:Preoperative RSR varied substantially across the cohort. Consequently, the effective postoperative global glenoid component inclination ranged from downward to superior inclination depending on the scapula rotation angle, despite targeted glenoid inclination angle of 0° executed with PSI. Therefore, accounting for scapula rotation in terms of the global glenoid inclination when planning the glenoid component inclination seems warranted. The consistency of SRA before versus after rTSA allows its incorporation into personalized planning to avoid superior inclination in the global reference system, which may increase shear forces on the glenoid component and lead to a slower recovery.

BACKGROUND:Posterior shoulder instability (PSI) can be caused either by structural or by functional deficits. Functional PSI often arises from neuromuscular imbalances rather than identifiable structural deficiencies. SYMPTOMS:This condition presents a complex clinical picture characterized by symptoms such as pain, discomfort during overhead activities, and episodes of subluxation or full dislocation. THERAPY:Understanding the treatment modalities available for functional PSI is critical to restoring function and preventing recurrence. In order to select the right treatment for posterior shoulder instability, it is important to differentiate between structural and functional instability. Functional posterior shoulder instability demands a meticulous and multifaceted approach to diagnosis and management. Clinicians must be vigilant in recognizing the type of PSI and start an according targeted therapy. Rehabilitation remains a cornerstone of treatment, with ongoing emphasis on the need for individualized rehabilitation regimes that promote functional recovery and prevent recurrence. For optimal outcomes in managing functional PSI, an integration of expert physiotherapeutic approaches, modern technology, such as, for example, functional electrical stimulation (FES) continue to gain momentum in current orthopedic practice. AIM:The aim of this article is to display possible treatment options for functional posterior shoulder instability.

Aim:Shoulder dysfunction commonly limits daily activities and independence. Evaluation of shoulder range of motion (ROM) is essential for diagnosis, treatment planning, and rehabilitation. This study evaluated the validity and robustness of Maia, an artificial intelligence-based video analysis tool, compared with optical motion capture (OMC; gold standard) and visual estimation by a shoulder surgeon (standard of care, SOC). Methods:Thirty-six patients with unilateral shoulder conditions (rotator cuff lesions, instability or ligament rupture) performed shoulder movements. ROM was measured simultaneously using Maia, OMC and SOC. Criterion validity was assessed by comparing Maia and SOC to OMC. Robustness to small camera misalignment was evaluated by testing Maia under optimal and 10°-offset camera positions. Agreement was assessed using Bland-Altman limits of agreement (LOA) and linear mixed models. Results:Maia showed small mean differences relative to OMC and no significant measurement differences. In contrast, SOC overestimated ROM for flexion and internal rotation with the shoulder abducted to 90° (high internal rotation). Bland-Altman LOA for Maia were approximately ±20° for most movements and exceeded ±30° for internal rotation, indicating substantial variability at the individual level despite small average differences between methods. Maia's performance remained stable under small camera misalignment. Conclusion:Findings suggest Maia provides clinically useful shoulder ROM estimates under controlled conditions and may be suitable for longitudinal monitoring or telehealth applications, with limitations for internal rotation.

Background The labral complex plays a crucial role in shaping the glenoid fossa morphology, thereby enhancing passive joint stability. This study aimed to investigate the influence of the labrum on glenoid inclination, a key determinant for load distribution within the joint. In addition, the labral influence on glenoid concavity depth and radius of curvature in the supero-inferior plane was evaluated. Methods Forty-three patients (mean age: 42 years [range 21-64 years]; 35 males, 8 females) with acromioclavicular (AC)-joint dislocation and no glenohumeral pathologies, who received a full series of magnetic resonance imaging or magnetic resonance arthrography, were retrospectively included. For each patient, the glenoid surface inclination, concavity depth, and radius of curvature was measured and compared to their respective values of the bony glenoid. In addition, the bony humeral head radius was measured to evaluate the influence of the labrum on joint congruency. Paired t-tests were used to assess the differences between bony and glenoid surface inclination and concavity depth. Repeated measures analysis of variance and pairwise comparisons were made to compare radius of curvature measurements. The correlation between the bony glenoid inclination and its difference to glenoid surface inclination, as well as between the bony glenoid radius and its difference to glenoid surface radius, was analyzed. Results The bony glenoid inclination measured 7.1° ( ± 4.1° standard deviation [SD]), the glenoid surface inclination 1.6° ( ± 3.2° SD); the bony glenoid concavity depth measured 4.0 mm ( ± 0.8 mm SD), the glenoid surface concavity depth 7.1 mm ( ± 0.9 mm SD). The bony glenoid radius of curvature measured 33.4 mm ( ± 3.3 mm SD), the glenoid surface radius 25 mm ( ± 2.1 mm SD) and the humeral head radius 24.1 mm ( ± 1.7 mm SD). The labrum significantly decreased the glenoid fossa inclination by 5.5° (P < .001), significantly decreased the glenoid fossa radius by 8.4 mm (P < .001) and significantly increased the concavity depth by 3.2 mm (P < .001). There was a positive correlation between the bony glenoid inclination and its respective difference to the glenoid surface inclination (r = 0.71, P < .001). Also, there was a positive correlation between bony glenoid radius of curvature and its respective difference to the glenoid surface radius (r = 0.77, P < .001). Conclusion The labral complex decreases glenoid inclination and increases joint concavity and congruency in the supero-inferior plane. Differences between bony and surface glenoid measures were higher in individuals with increased superior bony inclination and larger bony radii, suggesting a compensatory role to the labrum for the underlying bony morphology.

AimsMachine learning (ML) holds significant promise in optimizing various aspects of total shoulder arthroplasty (TSA), potentially improving patient outcomes and enhancing surgical decision-making. The aim of this systematic review was to identify ML algorithms and evaluate their effectiveness, including those for predicting clinical outcomes and those used in image analysis.MethodsWe searched the PubMed, EMBASE, and Cochrane Central Register of Controlled Trials databases for studies applying ML algorithms in TSA. The analysis focused on dataset characteristics, relevant subspecialties, specific ML algorithms used, and their performance outcomes.ResultsFollowing the final screening process, 25 articles satisfied the eligibility criteria for our review. Of these, 60% focused on tabular data while the remaining 40% analyzed image data. Among them, 16 studies were dedicated to developing new models and nine used transfer learning to leverage existing pretrained models. Additionally, three of these models underwent external validation to confirm their reliability and effectiveness.ConclusionML algorithms used in TSA demonstrated fair to good performance, as evidenced by the reported metrics. Integrating these models into daily clinical practice could revolutionize TSA, enhancing both surgical precision and patient outcome predictions. Despite their potential, the lack of transparency and generalizability in many current models poses a significant challenge, limiting their clinical utility. Future research should prioritize addressing these limitations to truly propel the field forward and maximize the benefits of ML in enhancing patient care.Cite this article: Bone Jt Open 2025;6(2):126–134.

Background:Glenoid concavity plays a critical role in shoulder stability via the concavity-compression mechanism. While the bony glenoid concavity, quantified by the bony shoulder stability ratio (BSSR), is a known determinant of stability, the labrum also contributes to the overall glenoid concavity. It remains unclear whether the labrum compensates for reduced bony concavity in stable shoulders. This study aimed to investigate the relationship between labral and bony glenoid concavity implementing the labral shoulder stability ratio (LSSR) and BSSR, respectively. We hypothesized that shoulders with reduced bony concavity (lower BSSR) would demonstrate increased labral concavity (higher LSSR), suggesting a compensatory mechanism. Methods:In this retrospective imaging study, 36 patients (mean age: 26.7 years) undergoing shoulder computed tomography arthrography between January 2020 and December 2024 for noninstability indications were included. BSSR and LSSR were calculated from standardized axial computed tomography images using three-dimensional multiplanar reconstructions. Concavity depth and radius were measured on the bony and chondrolabral contours, and the respective stability ratios were calculated. Inter-rater reliability was assessed using Bland-Altman plots and Pearson correlation. Pearson correlation analysis and subgroup comparisons were conducted to assess the relationship between BSSR and LSSR. Results:The mean BSSR was 28.3% ± 11.1% (range: 10.2%-52.5%), and the mean LSSR was 77.9% ± 10.8% (range: 49.1%-100%). There was no significant correlation between BSSR and LSSR (r = 0.01, P = 1.000). A low positive correlation was observed between glenoid bone depth and labral depth (r = 0.33, P = .049), and no significant relationship was found between the radius of the bony and labral best-fit circles (r = -0.11, P = .515). Subgroup analysis comparing patients with low BSSR (≤25th percentile) vs. high BSSR (≥75th percentile) showed no significant difference in LSSR values (78.8% vs. 75.9%, P = .554). Inter-rater agreement was good for both BSSR and LSSR measurements. Conclusion:This study demonstrates that labral morphology does not compensate for reduced bony glenoid concavity in clinically stable shoulders. Contrary to our hypothesis, lower BSSR was not associated with increased labral concavity, and no inverse relationship was observed between bone and labral curvature.

Background:Acromioclavicular joint (ACJ) dislocations have been linked to altered scapulothoracic orientation and scapula dyskinesis, but research on three-dimensional (3D) changes in scapulothoracic orientation after such injury in vivo has not been described before. The aim of our pilot study was to analyze scapulothoracic orientation changes in patients with ACJ dislocations using three-dimensional computed tomographic (CT) image reconstruction. Methods:Patients with ACJ dislocations who underwent CT imaging were included retrospectively and consecutively. Minors and cases with spine, neurologic or systemic diseases, and shoulder girdle fractures were excluded. Each CT was performed in supine position with elbows rested on the scanning table and had to depict the complete shoulder girdle. After 3D image reconstruction, tilt, upward rotation, internal rotation, translation, and protraction of the scapula were measured based on three osseous landmarks: the glenoid (the deepest point of its concavity), the medial root of the scapular spine, and the inferior scapular angle. The healthy contralateral side was used as a paired control. ACJ dislocations were graded according to Rockwood (RW) on strict frontal CT image reconstruction, including the contralateral shoulder, where measurements were also performed to enable comparison. Cases were labeled as acute or chronic with a 3-week injury-to-diagnosis interval cut-off. Results:The mean age of the 14 patients (11 males and 3 females) was 38.6 ± 15.6 years (range, 18-71). Ten cases were defined as acute (RW types II: 1; III: 3; V: 6) and four as chronic (II: 1; III: 2; V: 1). On the injured side, the scapula showed more internal rotation (46.2° ± 5.3° vs. 42.1° ± 4.4°; P = .003), more scapular tilt (20.2° ± 4.6° vs. 17.9° ± 3.5°; P = .022), and less upward rotation (10.1° ± 3.6° vs. 12.0° ± 4.8°; P = .043). No difference between sides was found for scapular translation (P = .342) and scapular protraction (P = .385). There was a trend toward more internal rotation for RW type V injuries (P = .097). Conclusion:In this first 3D in vivo study, patients with ACJ dislocations displayed changes in scapulothoracic orientation in all planes. The scapula of the injured side was more internally rotated, forwardly tilted, and less upwardly rotated than on the healthy contralateral side.