Three-dimensional cortical and trabecular bone microstructure of the proximal ulna.

INTRODUCTION: The three-dimensional (3D) microstructure of the cortical and trabecular bone of the proximal ulna has not yet been described by means of high-resolution 3D imaging. An improved characterization can provide a better understanding of their relative contribution to resist impact load. The aim of this study is to describe the proximal ulna bone microstructure using micro-computed tomography (micro-CT) and relate it to gross morphology and function. MATERIALS AND METHODS: Five dry cadaveric human ulnae were scanned by micro-CT (17 µm/voxel, isotropic). Both qualitative and quantitative assessments were performed on sagittal image stacks. The cortical thickness of the trochlear notch and the trabecular bone microstructure were measured in the olecranon, bare area and coronoid. RESULTS: Groups of trabecular struts starting in the bare area, spanning towards the anterior and posterior side of the proximal ulna, were observed; within the coronoid, the trabeculae were orthogonal to the joint surface. Consistently among the ulnae, the coronoid showed the highest cortical thickness (1.66 ± 0.59 mm, p = 0.04) and the olecranon the lowest (0.33 ± 0.06 mm, p = 0.04). The bare area exhibited the highest bone volume fraction (BV/TV = 43.7 ± 22.4%), trabecular thickness (Tb.Th = 0.40 ± 0.09 mm) and lowest structure model index (SMI = - 0.28 ± 2.20, indicating plate-like structure), compared to the other regions (p = 0.04). CONCLUSIONS: Our microstructural results suggest that the bare area is the region where most of the loading of the proximal ulna is concentrated, whereas the coronoid, together with its anteromedial facet, is the most important bony stabilizer of the elbow joint. Studying the proximal ulna bone microstructure helps understanding its possible everyday mechanical loading conditions and potential fractures. LEVEL OF EVIDENCE: N.A.

Regional differences in the three-dimensional bone microstructure of the radial head: implications for observed fracture patterns.

INTRODUCTION: A characterization of the internal bone microstructure of the radial head could provide a better understanding of commonly occurring fracture patterns frequently involving the (antero)lateral quadrant, for which a clear explanation is still lacking. The aim of this study is to describe the radial head bone microstructure using micro-computed tomography (micro-CT) and to relate it to gross morphology, function and possible fracture patterns. MATERIALS AND METHODS: Dry cadaveric human radii were scanned by micro-CT (17 µm/pixel, isotropic). The trabecular bone microstructure was quantified on axial image stacks in four quadrants: the anterolateral (AL), posterolateral (PL), posteromedial (PM) and anteromedial (AM) quadrant. RESULTS: The AL and PL quadrants displayed the significantly lowest bone volume fraction and trabecular number (BV/TV range 12.3-25.1%, Tb.N range 0.73-1.16 mm-1) and highest trabecular separation (Tb.Sp range 0.59-0.82 mm), compared to the PM and AM quadrants (BV/TV range 19.9-36.9%, Tb.N range 0.96-1.61 mm-1, Tb.Sp range 0.45-0.74 mm) (p = 0.03). CONCLUSIONS: Our microstructural results suggest that the lateral side is the "weaker side", exhibiting lower bone volume faction, less trabeculae and higher trabecular separation, compared to the medial side. As the forearm is pronated during most falls, the underlying bone microstructure could explain commonly observed fracture patterns of the radial head, particularly more often involving the AL quadrant. If screw fixation in radial head fractures is considered, surgeons should take advantage of the "stronger" bone microstructure of the medial side of the radial head, should the fracture line allow this.

Long-Term Outcome of Surgical Treatment for Kienböck Disease Using an Articular-Based Classification.

PURPOSE: The aim of this study was to report the outcomes of surgery using the Bain and Begg articular-based classification for the treatment of Kienböck disease. METHODS: We identified and followed patients who had surgery for Kienböck disease between 1995 and 2014. Assessment included functional scoring using a modification of the Gartland and Werley score, pain levels, and grip strength. RESULTS: Thirty-one patients were operated on for Kienböck disease between 1995 and 2014. Twenty-seven patients were assessed (12 men and 15 women). Mean age at the index procedure was 45.1 years (range, 20-82 years). Median follow-up after the index procedure was 10 years (range, 2-18 years). On the Bain and Begg classification, 5 patients had grade 0, 4 had grade 1, 5 had grade 2a, 10 had grade 2b, 1 had grade 3, and 1 had grade 4. The median pain visual analog scale improved from a preoperative score of 5 (interquartile range [IQR], 5-6) to a postoperative score of 2 (IQR, 0-3). The median functional scores from the modified Gartland and Werley score improved from 67 (IQR, 57.0-78.5) to 97 (IQR, 90.0-97.0). Eighteen out of 20 working patients returned to the same level of work. There was a significant improvement in power grip and tip pinch following surgery. One patient required a secondary salvage procedure. No patient required a full wrist fusion or arthroplasty. CONCLUSIONS: This study confirms that the Bain and Begg arthroscopic classification and an articular-based approach to Kienböck disease provide a high probability of good long-term relief of pain and a minimal chance of requiring a salvage procedure. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.

Defining the proximity of the axillary nerve from defined anatomic landmarks: an in vivo magnetic resonance imaging study.

BACKGROUND: The location of the axillary nerve in the shoulder makes it vulnerable to traumatic or iatrogenic injury. Cadaveric studies have reported the location of the axillary nerve but are limited because of tissue compression, dehydration, and decay. Three-Tesla (T) magnetic resonance imaging (MRI) allows high anatomic resolution of neural structures. The aim of our study was to better define the location of the axillary nerve from defined bony surgical landmarks in vivo, using MRI scan. METHODS: Using MRI, we defined a number of anatomic points and measured the distance from these to the perineural fat surrounding the axillary nerve using simultaneous tracker lines on both images. Two observers were used. RESULTS: A total of 187 consecutive 3-T MRI shoulder scans were included. Mean age was 57.9 years (range 18-86). The axillary nerve was located at a mean of 14.1 mm inferior from the bony glenoid at the anterior border, 11.9 mm from the midpoint, and 12.0 mm from the posterior border. There was a significant difference between distance at the anterior border and midpoint (P < .001), and between the anterior and posterior borders (P < .001). The axillary nerve was located at a mean of 12.6 mm medial to the humeral shaft at the anterior border, 9.9 mm at the midpoint, and 8.6 mm from the posterior border. There was a significant difference between distance at the anterior border and midpoint (P = .008) and between the anterior and posterior borders (P = .002). The mean distance of the axillary nerve from the anterolateral edge of the acromion was 53.3 mm (95% confidence interval [CI] 52.3, 54.2; range 33.9-76.3). The mean distance of the axillary nerve from the inferior edge of the capsule was 2.7 mm (95% CI 2.9, 3.1; range 0.3-9.9). There was a positive correlation between humeral head diameter and axillary nerve distance from the inferior glenoid (R2 = 0.061, P < .001). There was a positive correlation between humeral head diameter and distance from the anterolateral edge of the acromion (R2 = 0.140, P < .001). CONCLUSION: Our study has defined the proximity of the axillary nerve from defined anatomic landmarks. The proximity of the axillary nerve to the inferior glenoid and medial humeral shaft changes as the axillary nerve passes from anterior to posterior. The distance of the axillary nerve from the anterolateral edge of the acromion remains relatively constant. Both sets of distances may be affected by humeral head size. The study has relevance to the shoulder surgeon when considering "safe zones" during arthroscopic or open surgery.

3D mapping of scaphoid fractures and comminution.

OBJECTIVE: Acute and subacute scaphoid fractures were assessed using 3D computer tomography (CT). The aims were to describe fracture morphology, to map fractures onto a 3D scaphoid model and to correlate this to scaphoid anatomy. MATERIALS AND METHODS: A retrospective, multicentre database search was performed to identify CT studies of acute and subacute scaphoid fractures. CT scans of scaphoid fractures less than 6 weeks from time of injury were included in this retrospective, multicentre study. CTs were segmented and converted into three-dimensional models. Following virtual fracture reduction, fractures were mapped onto a three-dimensional scaphoid model. RESULTS: Seventy-five CT scans were included. The median delay from injury to CT was 29 days. Most studies were in male patients (89%). Most fractures were comminuted (52%) or displaced (64%). A total of 73% of displaced fractures had concomitant comminution. Waist fractures had higher rates of comminution and displacement when compared with all other fractures. Comminution was located along the dorsal ridge and the volar scaphoid waist. CONCLUSION: Our study is the first to describe acute fracture morphology using 3D CT and to correlate comminution and displacement to fracture types. The dorsal ridge and volar waist need prudent assessment, especially in waist fractures.

Intrathoracic shoulder dislocation causing rupture of the right main bronchus.

An intrathoracic shoulder dislocation is a rare injury, usually the result of high-energy trauma [Hawkes et al. in Am J Orthop 43(4):E74-E78, 2014; Tsai et al. in Ann Thorac Cardiovasc Surg 20:592-594, 2014, in Rupprecht et al. Bull Emerg Trauma 5(3):212-214, 2017; Abellan et al. J Orthop Surg (Hong Kong)18(2):254-257, 2010]. It often occurs in conjunction with thoracic, pelvic, and long bone injuries. In addition, there is often significant injuries to the shoulder girdle and chest wall associated with neurovascular compromise [Abellan et al. J Orthop Surg (Hong Kong)18(2):254-257, 2010; Lin et al. JBJS Case Connect 6(1):e61, 2016]. Following a literature review, it appears that no cases have been reported of an intrathoracic shoulder dislocation associated with a rupture of the ipsilateral main bronchus. We present a case of a rupture of the right main bronchus that occurred due to high-energy impact and an associated intrathoracic right-shoulder fracture dislocation. Computed tomography identified diastasis of the ipsilateral first intercostal space, humeral head indentation in the hilum of the lung, and a pneumoarthrogram of the right glenohumeral joint.

A new radiographic view of the scaphotrapeziotrapezoid joint-a cadaveric study.

BACKGROUND: The scaphotrapeziotrapezoid joint (STTJ) has a complex osseous and ligamentous anatomy. Precise radiographic assessment is paramount when assessing osteoarthritic, post-traumatic, or post-operative patients. There has been no described technique to image the STTJ without any wrist movement, unobscured by the rest of the carpus. The aim of this study was to define an optimal radiographic method to assess the STTJ while maintaining the wrist in neutral position. METHODS: Computer tomography 3-D reconstructions of three uninjured wrists were initially used to determine an approximate beam angle. Serial radiographs of 12 cadaveric wrists were taken. The forearms were positioned in varying degrees of pronation and supination. The beam angle was concurrently adjusted to varying degrees of caudal tilt. From the images obtained, we assessed if the adjacent carpus obscured the view of the STTJ. RESULTS: Optimal STTJ imaging was in the semi-pronated wrist position with the X-ray beam tilted caudal. We found that the STTJ was best visualized at 48° supination from a fully pronated wrist and a caudal beam angle of 22°. CONCLUSIONS: The described wrist and beam orientation can aid in achieving an unobstructed view of the STTJ with little technical effort. This can aid in imaging ambulatory patients where symptoms prevent using other imaging techniques as well as patients in the operating room where imaging timing can be critical.

Use and outcome of 1,220 primary total elbow arthroplasties from the Australian Orthopaedic Association National Joint Arthroplasty Replacement Registry 2008-2018.

Background and purpose - The Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) was analyzed to determine trends in use of primary total elbow arthroplasty (TEA), the types of prostheses used, primary diagnoses, reasons for and types of revision, and whether the primary diagnosis or prosthesis design influenced the revision rate.Patients and methods - During 2008-2018, 1,220 primary TEA procedures were reported of which 140 TEAs were revised. Kaplan-Meier estimates of survivorship were used to describe the time to first revision and hazard ratios (HR) from Cox proportional hazard models, adjusted for age and sex, were used to compare revision rates.Results - The annual number of TEAs performed remained constant. The 3 most common diagnoses for primary TEA were fracture/dislocation (trauma) (36%), osteoarthritis (OA) (34%), and rheumatoid arthritis (RA) (26%). The cumulative percentage revision for all TEAs undertaken for any reason was 10%, 15%, and 19% at 3, 6, and 9 years. TEAs undertaken for OA had a higher revision rate compared with TEAs for trauma (HR = 1.8, 95% CI 1.1-3.0) and RA (HR = 2.0, CI 1.3-3.1). The Coonrad-Morrey (50%), Latitude (30%), Nexel (10%), and Discovery (9%) were the most used prosthesis designs. There was no difference in revision rates when these 4 designs were compared. The most common reasons for revision were infection (35%) and aseptic loosening (34%).Interpretation - The indications for primary and revision TEA in Australia are similar to those reported for other registries. Revision for trauma is lower than previously reported.

Is external fixation a better way than plaster to supplement K-wires in non-comminuted distal radius fractures?

BACKGROUND: Distal radius fractures represent about one-sixth of all fractures. There is still no consensus on the treatment of this fracture. We have several issues to assess and address; one of them is the fixation method. We tried to compare the effectiveness of two methods of stabilisation of distal radial fracture. Comparison between the techniques of Kirschner wire (K-wire) fixation with plaster and K-wire fixation with external fixation (Ex-Fix) was undertaken to assess which treatment modality gives better results in patients with distal radius fracture Frykman VII and VIII with no metaphyseal comminution. METHOD: Fifty-six patients were chosen randomly and then allocated to two different modalities of stabilisation randomly as well, they were followed up; three of them were lost to follow-up because of death and two moved away from the area. Fifty-one patients were randomised in two groups: 24 were treated with K-wire and spanning Ex-Fix supplementation and 27 were treated with K-wires and plaster. Patients were prospectively monitored following the operation with a minimum follow-up of 1 year. Measurement of range of motion was obtained after surgery. Visual Analogue Scale (VAS) scores for pain and satisfaction levels were also recorded. RESULTS: There was statistically significant difference in favour of the Ex-Fix patient group for pain (VAS, Ex-Fix group: mean 14.9; plaster group: mean 28.1) and satisfaction (Ex-Fix group: mean 89.7;plaster group: mean 76.3). Although one would expect that range of motion would be reduced in the Ex-Fix group, there were no statistically significant differences found, with the exception of supination where results were in favour of the Ex-Fix group (mean 54.4; plaster group: mean 45.2). CONCLUSION: In our study, xternal fixator (Ex-Fix) supplementation of K-wiring favoured patients with distal radius fracture, even though there was no metaphyseal comminution, and therefore is suggested in contrast to plaster supplementation.

Fracture line morphology of complex proximal humeral fractures.

BACKGROUND: The aim of this study was to assess proximal humeral fracture patterns using 3-dimensional computed tomography images and relate them to the normal osseous landmarks and soft-tissue attachments. METHODS: Forty-eight 3-dimensional computed tomography scans of proximal humeral fractures were retrospectively collected, and the fractures were transcribed onto proximal humeral templates. We analyzed the common location and orientation of the fracture lines, with a focus on fractures of the articular surface, tuberosities, metaphysis, and proximal diaphysis. These fractures were compared with the attachments of the rotator cuff and glenohumeral capsule. RESULTS: Fifty-two percent of the fractures involved the articular surface. No fractures passed through the bicipital groove, and fractures were more commonly found on the posterior lesser tuberosity and on the anterior greater tuberosity, coinciding with the intervals between the rotator cuff tendon insertions. Intracapsular fractures of the calcar were more common (68%) than extracapsular fractures (32%). On the anterolateral aspect of the proximal humerus, fractures radiated from the articular margin, vertically down through the tuberosity zone between the rotator cuff footprints, meeting horizontally oriented fractures in the metaphyseal zone. On the posterior aspect, vertical fractures from the tuberosity zone continued downward to the metaphyseal zone adjacent to the infraspinatus and teres minor footprints. CONCLUSIONS: Fractures of the proximal humerus follow characteristic patterns. Fractures frequently split the greater tuberosity and are closely related to the intervals of the rotator cuff attachments.

Shoulder Stiffness: Current Concepts and Concerns.

UNLABELLED: Shoulder stiffness can be caused by various etiologies such as immobilization, trauma, or surgical interventions. The Upper Extremity Committee of ISAKOS defined the term "frozen shoulder" as idiopathic stiff shoulder, that is, without a known cause. Secondary stiff shoulder is a term that should be used to describe shoulder stiffness with a known cause. The pathophysiology of frozen shoulder is capsular fibrosis and inflammation with chondrogenesis, but the cause is still unknown. Conservative treatment is the primary choice. Pain control by oral medication, intra-articular injections with or without joint distension, and physical therapy are commonly used. In cases with refractory stiffness, manipulation under anesthesia or arthroscopic capsular release may be indicated. Because of various potential risks of complications with manipulations, arthroscopic capsular release is preferred. After the capsular release, stepwise rehabilitation is mandatory to achieve satisfactory outcome. LEVEL OF EVIDENCE: Level V, evidence-based review.

Kienböck Disease: Moving Forward.

Over the past decade, a plethora of new information has been reported regarding etiology, natural history, classification, and treatment options for lunate osteonecrosis. New disease classifications have been described based on advanced imaging determination of lunate viability as well as a cartilage-based arthroscopic classification. Here we review the newest literature regarding Kienböck disease and present a new treatment algorithm that incorporates the traditional osseous classification system with a perfusion/viability classification and an articular cartilage-based classification.

Inferior angle of scapula fractures: a review of literature and evidence-based treatment guidelines.

BACKGROUND: Inferior angle of scapula (IAS) fractures are rare, with very few cases reported. They typically present with pain, loss of shoulder motion, and scapula winging. Operative and nonoperative treatments have been trialed with varying success. The aim of this study was to gather data relating to IAS fractures to develop evidence-based treatment guidelines as none are currently available. METHODS: A search was conducted of the PubMed and Google Scholar databases to identify cases of IAS fractures. Data collected about each case included age and gender of the patient, mechanism of injury, fracture displacement, treatment, and outcome. The authors report 2 additional IAS fracture cases. RESULTS: Ten cases were identified for inclusion in this study, 8 from the literature and 2 described by the authors. Of the 10 cases, 7 described displaced IAS fractures and 3 described undisplaced fractures. All displaced fractures treated nonoperatively resulted in a painful nonunion. All that underwent operative fixation, whether acutely or after failed nonoperative treatment, had resolution of pain and a good functional outcome. All undisplaced fractures were treated nonoperatively; 1 had persisting pain. Surgical exploration identified the fracture fragment attached to serratus anterior in 2 cases and attached to both serratus anterior and latissimus dorsi in 2 cases. DISCUSSION AND CONCLUSIONS: There are limited data available about IAS factures. From the cases reviewed, treatment recommendations include the following: (1) displaced IAS fractures should undergo operative fixation to prevent the development of a painful nonunion; (2) suture repair provides adequate fixation; and (3) undisplaced fractures have a variable outcome when treated nonoperatively.

The effect of lunate morphology on the 3-dimensional kinematics of the carpus.

PURPOSE: To assess carpal kinematics in various ranges of motion in 3 dimensions with respect to lunate morphology. METHODS: Eight cadaveric wrists (4 type I lunates, 4 type II lunates) were mounted into a customized platform that allowed controlled motion with 6 degrees of freedom. The wrists were moved through flexion-extension (15°-15°) and radioulnar deviation (RUD; 20°-20°). The relative motion of the radius, carpus, and third metacarpal were recorded using optical motion capture methods. RESULTS: Clear patterns of carpal motion were identified. Significantly greater motion occurred at the radiocarpal joint during flexion-extension of type I wrist than a type II wrist. The relative contributions of the midcarpal and radiocarpal articulations to movement of the wrist differed between the radial, the central, and the ulnar columns. During wrist flexion and extension, these contributions were determined by the lunate morphology, whereas during RUD, they were determined by the direction of wrist motion. The midcarpal articulations were relatively restricted during flexion and extension of a type II wrist. However, during RUD, the midcarpal joint of the central column became the dominant articulation. CONCLUSIONS: This study describes the effect of lunate morphology on 3-dimensional carpal kinematics during wrist flexion and extension. Despite the limited size of the motion arcs tested, the results represent an advance on the current understanding of this topic. CLINICAL RELEVANCE: Differences in carpal kinematics may explain the effect of lunate morphology on pathological changes within the carpus. Differences in carpal kinematics due to lunate morphology may have implications for the management of certain wrist conditions.

Medial grasping sutures significantly improve load to failure of the rotator cuff suture bridge repair.

BACKGROUND: The suture bridge (SB) transosseous-equivalent rotator cuff repair reduces re-tear rates compared with single-row or other double-row constructs. However, failure rates continue to be high, especially in large and massive tears. The aim of this study was to assess the biomechanical performance of a new SB repair with use of a medial grasping suture compared with the traditional SB repair. METHODS: Seven matched pairs of sheep infraspinatus tendons were randomly assigned to either SB or suture bridge with grasping suture (SBGS) repair. Each construct was subjected to cyclic loading and then loaded until failure under displacement control in a materials testing machine. Footprint displacement, ultimate load to failure, and mode of failure were assessed. RESULTS: The rotator cuff footprint displacement was less during tensile loading with the addition of the medial grasping suture. The ultimate load to failure was significantly greater for the SBGS repair group than for the SB repair group (334.0 N vs 79.8 N). The mode of failure was the tendon pulling off the footprint in all cases (type 1 tear). There were no failures in which the tendon tore at the medial row of anchors, leaving part of the tendon still on the footprint (type 2 tear). CONCLUSION: The addition of a medial grasping suture significantly improved the ultimate load to failure and reduced the footprint displacement of the SB rotator cuff repair in a biomechanical model.

Addressing the Central Band in Acute and Chronic Essex-Lopresti Injury: A Case Report and Technique Description.

CASE: A 34-year-old man was acutely treated with radial head arthroplasty and central band repair following Essex-Lopresti injury. A 38-year-old man presented with chronic longitudinal instability following failed radial head arthroplasty, which was performed for failed fixation. Treatment with revision radial head arthroplasty and central band reconstruction restored longitudinal stability. CONCLUSION: We have a low threshold to repair the central band in acute Essex-Lopresti injury with sufficient evidence of disruption. Nearly all chronic cases require central band reconstruction to restore longitudinal stability. We do not temporarily pin the DRUJ, and distal ulnar shortening is rarely indicated.

Biomechanical analysis of cadaveric wrists before and after MOTEC wrist arthroplasty using a hexapod robot.

This study compares wrist motion, biomechanical behaviour and radiographic parameters before and after total wrist arthroplasty using a fourth-generation spherical articulation prosthesis. A total of 10 cadaveric specimens were assessed using a hexapod Stewart platform robot. After arthroplasty, there were significant increases in both stiffness and phase angle of wrist motion across all planes of motion assessed. In three specimens, a sudden increase in moment was observed on load/displacement curves. Radiographically, carpal height increased by 14%, and the centre of rotation was displaced 11.1 mm proximally, 4.6 mm dorsally and 3.9 mm radially. This stretched the musculotendinous units, tightening the joint, while increasing the moment arm of the wrist flexors and decreasing the moment arm of the extensors, potentially important in the development of postoperative flexion contractures. Possible alterations in technique and/or implant design are considered to assist surgeons in achieving optimal clinical and survivorship outcomes.

Detection, classification, and characterization of proximal humerus fractures on plain radiographs.

Aims: The purpose of this study was to develop a convolutional neural network (CNN) for fracture detection, classification, and identification of greater tuberosity displacement ≥ 1 cm, neck-shaft angle (NSA) ≤ 100°, shaft translation, and articular fracture involvement, on plain radiographs. Methods: The CNN was trained and tested on radiographs sourced from 11 hospitals in Australia and externally validated on radiographs from the Netherlands. Each radiograph was paired with corresponding CT scans to serve as the reference standard based on dual independent evaluation by trained researchers and attending orthopaedic surgeons. Presence of a fracture, classification (non- to minimally displaced; two-part, multipart, and glenohumeral dislocation), and four characteristics were determined on 2D and 3D CT scans and subsequently allocated to each series of radiographs. Fracture characteristics included greater tuberosity displacement ≥ 1 cm, NSA ≤ 100°, shaft translation (0% to < 75%, 75% to 95%, > 95%), and the extent of articular involvement (0% to < 15%, 15% to 35%, or > 35%). Results: For detection and classification, the algorithm was trained on 1,709 radiographs (n = 803), tested on 567 radiographs (n = 244), and subsequently externally validated on 535 radiographs (n = 227). For characterization, healthy shoulders and glenohumeral dislocation were excluded. The overall accuracy for fracture detection was 94% (area under the receiver operating characteristic curve (AUC) = 0.98) and for classification 78% (AUC 0.68 to 0.93). Accuracy to detect greater tuberosity fracture displacement ≥ 1 cm was 35.0% (AUC 0.57). The CNN did not recognize NSAs ≤ 100° (AUC 0.42), nor fractures with ≥ 75% shaft translation (AUC 0.51 to 0.53), or with ≥ 15% articular involvement (AUC 0.48 to 0.49). For all objectives, the model's performance on the external dataset showed similar accuracy levels. Conclusion: CNNs proficiently rule out proximal humerus fractures on plain radiographs. Despite rigorous training methodology based on CT imaging with multi-rater consensus to serve as the reference standard, artificial intelligence-driven classification is insufficient for clinical implementation. The CNN exhibited poor diagnostic ability to detect greater tuberosity displacement ≥ 1 cm and failed to identify NSAs ≤ 100°, shaft translations, or articular fractures.

Anatomic study of the superior glenoid labrum.

The purpose of the study was to describe the normal anatomy of the glenoid labrum to help identification of pathology and guide surgical repair. Twenty dry bone scapulae and 19 cadaveric shoulders were examined. Light microscopy was performed on 12 radial slices through the glenoid. An external capsular circumferential ridge, 7-8 mm medial to the glenoid rim marks the attachment of the capsule. A separate internal labral circumferential ridge 4 mm central to the glenoid rim marks the interface between the labrum and articular cartilage. A superior-posterior facet was found consistently on the glenoid. Two thirds of the long head of biceps arises from the supraglenoid tubercle, 6.6 mm from the glenoid face, the remainder from the labrum. The superior labrum is concave and is loosely attached to the articular cartilage and glenoid rim. Clefts and foramens are common superiorly. In contrast the anterior-inferior labrum is convex, attaches 4 mm central to the glenoid rim and has a strong attachment to articular cartilage and bone. Sublabral clefts, recesses, and holes are common, but only in the superior-anterior labrum. Lesions in other regions of the labrum are potentially pathological. A complex superior labrum tear that extends to involve the biceps anchor, should have the biceps anchor repaired to the supraglenoid tubercle (mean 6.6 mm off the glenoid face) and the labrum be repaired to the glenoid rim. The anteroinferior labrum should be repaired 4 mm onto the glenoid face. This study will aid in identifying pathological labral lesions and guide anatomic repairs.