Imaging of the Acromioclavicular Joint: Anatomy, Function, Pathologic Features, and Treatment

Double Fixation Technique for Acute Acromioclavicular Joint Dislocation Using the Two-Button Technique and Gracilis Autograft Reinforcement: A Case Report of an Elite Athlete Seeking a Rapid Return to Sports Activity

Acromioclavicular joint dislocation is a relatively common injury in the general population, especially in younger ages. Although acromioclavicular injuries are a well-studied topic, there are many controversies concerning not only the best way to treat them by operative or conservative methods but also determining the most effective fixation methods, providing better functional outcomes, faster rehabilitation protocols, fewer complications, and lower recurrence rates. In this case report, we present a case of type III acromioclavicular dislocation in a young athlete who was treated operatively using a double fixation technique, aiming to address these controversies and offer insights into the optimal management of such injuries.

Acromioclavicular joint separation: Controversies and treatment algorithm

In this article, we present an uptodate outline of acromioclavicular (AC) joint separation. A clear understanding of acromioclavicular joint injury in terms of the mechanism of injury, clinical picture, diagnostic imaging, and most updated surgical techniques used for the treatment can provide the best care for those patients. This article describes updated treatment strategies for AC separation, including type III AC separation which is known most controversial. Finally, we present a proposed treatment algorithm that can aid in the treatment of AC separation from the most updated evidence.

In Vivo Analysis of Acromioclavicular Kinematics and Distance During Multiplanar Humeral Elevation

BACKGROUND

Knowledge of acromioclavicular (AC) joint kinematics and distance may provide insight into the biomechanical function and development of new treatment methods. However, accurate data on in vivo AC kinematics and distance between the clavicle and acromion remain unknown.

PURPOSE/HYPOTHESIS

The purpose of this study was to investigate 3-dimensional AC kinematics and distance during arm elevation in abduction, scaption, and forward flexion in a healthy population. It was hypothesized that AC kinematics and distance would vary with the elevation angle and plane of the arm.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 19 shoulders of healthy participants were enrolled. AC kinematics and distance were investigated with a combined dual fluoroscopic imaging system and computed tomography. Rotation and translation of the AC joint were calculated. The AC distance was measured as the minimum distance between the medial border of the acromion and the articular surface of the distal clavicle (ASDC). The minimum distance point (MDP) ratio was defined as the length between the MDP and the posterior edge of the ASDC divided by the anterior-posterior length of the ASDC. AC kinematics and distance between different elevation planes and angles were compared.

RESULTS

Progressive internal rotation, upward rotation, and posterior tilt of the AC joint were observed in all elevation planes. The scapula rotated more upward relative to the clavicle in abduction than in scaption (P = .002) and flexion (P = .005). The arm elevation angle significantly affected translation of the AC joint. The acromion translated more laterally and more posteriorly in scaption than in abduction (P < .001). The AC distance decreased from the initial position to 75° in all planes and was significantly greater in flexion (P < .001). The MDP ratio significantly increased with the elevation angle (P < .001).

CONCLUSION

Progressive rotation and significant translation of the AC joint were observed in different elevation planes. The AC distance decreased with the elevation angle from the initial position to 75°. The minimum distance between the ASDC and the medial border of the acromion moved anteriorly as the shoulder elevation angle increased.

CLINICAL RELEVANCE

These results could serve as benchmark data for future studies aiming to improve the surgical treatment of AC joint abnormalities to restore optimal function.

Can We Control Lateral Shoulder Balance Through Proximal Thoracic Curve Correction in Lenke Type 2 Adolescent Idiopathic Scoliosis?

BACKGROUND

Proximal thoracic curve (PTC) correction has been considered to prevent lateral shoulder imbalance in Lenke Type 2 adolescent idiopathic scoliosis (AIS) patients; however, postoperative shoulder imbalance (PSI) commonly occurs despite these strategies with PTC correction. We investigated the hypothesis that PTC correction would not directly affect PSI in the majority of Lenke type 2 AIS cases. Furthermore, we investigated the risk factors for lateral PSI after corrective surgery.

METHODS

This study examined the records for AIS patients with Lenke type 2 who underwent corrective surgery and followed up for >2 years. Patients were categorized into PSI (-); radiologic shoulder height (RSH)<15 mm, and PSI (+); RSH≥15 mm. Repeated measures analysis of variance was performed at preoperatively, postoperatively, 1 month, and final follow-up. Postoperative lateral shoulder imbalance was predicted by the identification of univariate analysis and multivariate analysis.

RESULTS

Among the 151 patients reviewed, 29 (19.2%) showed PSI at final follow-up. Lateral shoulder balance parameters showed different directionalities between PSI (-) and (+) groups at postoperatively, 1 month, and final follow-up ( P <0.01 each). Preoperative PTC, middle thoracic curve (MTC) curve and MTC correction showed strong correlations with the RSH ( P =0.01, 0.03, and 0.04, respectively). However, PTC correction did not show a significant correlation with the RSH. Moreover, only a smaller MTC curve and larger MTC correction rate were related to lateral PSI in multivariate analysis.

CONCLUSIONS

In Lenke type 2 AIS curves, the MTC curve and its correction predominantly influence lateral shoulder imbalance after corrective surgery, irrespective of the PTC correction extent. Consequently, overemphasizing the correction of the PTC curve may not necessarily lead to an improved lateral shoulder balance. When MTC curve is smaller, surgeons should be more careful for MCT overcorrection leading to a lateral shoulder imbalance.

LEVEL OF EVIDENCE

Level III.

Tunnel-free acromioclavicular joint reconstruction is associated with improved initial reduction and higher patient satisfaction

Background

Many surgical techniques have been described for acromioclavicular (AC) joint reconstruction. Creation of bone tunnels through the clavicle or coracoid has been shown to be a risk factor for fracture. Use of an AC reconstruction technique that does not create bone tunnels may obviate this risk. This study aims to evaluate clinical outcomes of AC joint reconstruction using a tunnel-free technique compared to reconstruction using a cortical button and clavicular drill holes.

Methods

Consecutive patients who underwent AC joint reconstruction by a single surgeon in a subspecialty referral practice were included. One group of patients received cortical button fixation (button group), in which sutures were passed around the coracoid, brought up through a drill hole in the clavicle, and tied over a cortical button. The other group of patients received tunnel-free fixation, in which a self-locking tape suture was passed in a cerclage fashion around the base of the coracoid and the clavicle and tensioned with a tensioning device (cerclage group). Both groups underwent reconstruction of the coracoclavicular (CC) ligament and AC joint capsule using tibialis anterior allograft. Patient-reported outcome scores and satisfaction were collected and compared between groups. Radiographs were reviewed to evaluate CC ligament distance and loss of reduction.

Results

Twenty-two patients were included in the study (button n = 10, cerclage n = 12). Preoperative demographics and injury characteristics were not different between groups. Average radiographic follow-up was not different between groups (button: 231 days, cerclage: 105 days). Postoperative American Shoulder and Elbow Surgeons, visual analog scale, and Single Assessment Numeric Evaluation scores were similar between groups. Two postoperative clavicle fractures were sustained in the button group. These occurred through clavicular drill holes and were preceded by tunnel widening. No fractures occurred in the cerclage group. CC distance at initial follow-up was significantly less in the cerclage group (button: 11.2 ± 4.5 mm, cerclage: 7.0 ± 2.9 mm, P =.023). Loss of reduction was similar throughout the postoperative period (button: 4.3 ± 2.6 mm, cerclage: 4.8 ± 4.1 mm, P >.05. Forty percent of patients were unsatisfied with their clavicle after button fixation (n = 4/10), compared with zero after cerclage fixation (n = 0/12, P =.03). Reasons for dissatisfaction were fracture (n = 2) and persistent cosmetic deformity (n = 2).

Conclusion

Tunnel-free AC joint reconstruction is associated with improved initial radiographic appearance and patient satisfaction compared to single cortical button fixation. Postoperative clavicle fracture and persistent cosmetic deformity drive patient dissatisfaction, which may be minimized by avoiding clavicular drill holes and using a tensioned self-locking cerclage suture to improve initial reduction.

Management of Acromioclavicular Joint Injuries: A Historic Account

There has been a rapid evolution in best practice management of acromioclavicular (AC) joint injuries. AP, Zanca, scapular Y, and dynamic axillary radiographic views provide optimal visualization of the joint and may assess for the presence of horizontal AC instability. Severity of AC joint pathology is classified according to the 6-tier Rockwood scoring system. Over 160 surgical techniques have been described for AC joint repair and reconstruction in the last decade; as a result, determining the optimal treatment algorithm has become increasingly challenging secondary to the lack of consistently excellent clinical outcomes.

Acromioclavicular Joint Anatomy and Biomechanics: The Significance of Posterior Rotational and Translational Stability

The shoulder girdle extends from the sternoclavicular joint to the scapular stabilizing muscles posteriorly. It consists of 3 joints and 2 mobile regions. The shoulder girdle is statically stabilized by the acromioclavicular and coracoclavicular capsuloligamentous structures and dynamically stabilized by the trapezius, deltoid, and deltotrapezial fascia. During humerothoracic elevation, the clavicle elevates, protracts, and rotates posteriorly through the sternoclavicular joint while the scapula tilts posteriorly and rotates upward. The purpose of this article is to review the anatomy and biomechanics of the acromioclavicular joint and the shoulder girdle.

Dynamic evaluation of the sternoclavicular and acromioclavicular joints using an upright four-dimensional computed tomography

In the analysis of the shoulder complex, the sequential changes occurring in the sternoclavicular and acromioclavicular joints during active shoulder motion are challenging to track. This study aimed to investigate the in vivo sternoclavicular and acromioclavicular joint motions during active elevation, including the sequential changes in these joint spaces using upright four-dimensional computed tomography (4DCT). Bilateral shoulders of 12 healthy volunteers upright 4DCT were obtained during active elevation similar to a "hands up" motion. The sternoclavicular and acromioclavicular rotation angles, joint distances, and closest points on the clavicle relative to the thorax and scapula were evaluated during 10°-140° of humerothoracic elevation. During humerothoracic elevation, the clavicle elevated, retracted, and rotated posteriorly relative to the thorax, whereas the scapula rotated upwardly, internally, and posteriorly relative to the clavicle. All the sternoclavicular and acromioclavicular joint rotation angles were significantly different at ≥ 30°-50° of humerothoracic elevation compared with 10° of humerothoracic elevation. The mean sternoclavicular and acromioclavicular joint distances were 2.2 ± 1.1 mm and 1.6 ± 0.9 mm, respectively. The closest points were located on the anteroinferior part of the medial and lateral clavicle in the sternoclavicular and acromioclavicular joints, respectively. Significant differences were observed in the acromioclavicular joint distance and anterior/posterior movements of the closest points in the sternoclavicular and acromioclavicular joints compared with 10° of humerothoracic elevation. Our sternoclavicular and acromioclavicular closest point results indicate that the impingement tends to occur at the anteroinferior part of the medial and lateral aspects of the clavicle and may be related to osteoarthritis.

Physeal injuries of the clavicle: pediatric counterparts to adult acromioclavicular and sternoclavicular joint separations

The epiphyses at the medial and lateral ends of the clavicle are small, ossify relatively late, and may not fuse until early adulthood. Because of this unique anatomy, pediatric and young adult injuries that involve the clavicle often differ from the patterns typically seen in older adults. Clavicular trauma that affects the acromioclavicular joint laterally or sternoclavicular joint medially often results in a physeal fracture and as such, can go unrecognized or be mistaken for a joint dislocation. Radiographic assessment is challenging, particularly when the epiphysis is not yet ossified. However, MR imaging allows for visualization of the cartilage, periosteum and perichondrium, and ligaments of the affected joints. Lateral clavicle physeal injuries can be categorized by the Dameron and Rockwood system, the pediatric correlate to the Rockwood classification of adult acromioclavicular joint injuries. Medial clavicle physeal fractures, similar to adult sternoclavicular joint dislocations, may result in anterior or posterior displacement. Because of their great ability to heal and remodel, clavicular physeal fractures respond better to conservative management than true acromioclavicular or sternoclavicular joint dislocations. Therefore, it is essential to recognize the true nature of these injuries, as there are implications for successful treatment and appropriate prognosis.

A Sports Medicine Clinician's Guide to the Diagnosis and Management of Distal Clavicular Osteolysis

ABSTRACT

Weightlifting associated shoulder injuries have seen a dramatic rise in the last 20 years. Distal clavicular osteolysis, coined weightlifter's shoulder, is one such condition caused by repetitive microtrauma to the distal clavicle with subsequent, painful development of bony erosions and resorption of the distal clavicle. Diagnosis, treatment, and prevention of this condition can be challenging. In this article, we highlight evidence-based clinical recommendations for the diagnosis and management of distal clavicular osteolysis, including specific considerations for atraumatic and posttraumatic etiologies, to help clinicians better care for their patients. Activity modification and rehabilitation are the mainstays of the initial treatment. Adjuvant treatments, such as injections or surgery, may be required in refractory cases or in certain patient populations. Early recognition and treatment of weightlifter's shoulder is essential to prevent progression to acromioclavicular joint pathology or instability and to allow for continued participation in sport-specific activities.

Fractures of the limbs: basic concepts for the emergency department

Traumatic injuries of the limbs are very common and account for a large number of imaging examinations, especially in emergency departments. These injuries can often be resolved if they are recognized and treated appropriately. Their diagnosis requires a complete clinical assessment and the correct interpretation of the appropriate imaging tests. Radiologists play an important role, especially in diagnosing lesions that can go undetected. To this end, radiologists need to know the normal anatomy and its variants, the mechanisms of injury, and the indications for different imaging tests, among which plain-film X-rays are the main technique for the initial evaluation. This article aims to review the relevant characteristics of limb fractures in adults and of lesions that can be associated with these fractures, as well as how to describe them to ensure appropriate clinical management.

Acromioclavicular Joint Injuries in Sport

ABSTRACT

Sport-related shoulder injuries, including disruptions to the acromioclavicular joint (ACJ), are common. An ACJ injury is classified by the degree and direction of the clavicle displacement. Although the diagnosis can be made clinically, standard radiographic views are important to determine the severity of the ACJ disruption and assess for concurrent injuries. The majority of ACJ injuries can be managed nonoperatively; however, surgical treatment is indicated in some cases. Long-term outcomes are generally favorable for most ACJ injuries, and athletes generally return to sport without functional limitations. This article provides an in-depth discussion regarding all aspects of ACJ injuries, including clinically relevant anatomy, biomechanics, evaluation, treatment, and complications.

The Incidence of Symptomatic Mediastinal Compromise Following Medial Clavicle Fractures

Medial clavicle fractures pose a concern for mediastinal compromise because of their proximity to the sternoclavicular joint. However, the true incidence of this complication is unknown. The purpose of this study was to evaluate fracture configuration and determine the incidence of mediastinal compromise following medial clavicle fractures. A retrospective analysis of all patients treated for isolated medial one-third clavicle fractures at a single institution was performed. Patient demographics, the mechanism of injury, complications, and treatment were recorded. The fracture pattern and orientation were determined from a review of injury radiographs and computed tomography scans. The incidence of subsequent mediastinal compromise was then identified via a chart review. One hundred five patients were included for analysis. Twenty-two patients (20.8%) had computed tomography scans for review. The average age was 56 years, with 53% of patients being male. Sixty-eight percent of patients reported a high-energy mechanism of injury. No patients demonstrated evidence of mediastinal compression on physical examination. No patients required hospitalization for complications secondary to mediastinal compromise. Ninety percent (n=94) of patients were treated nonoperatively. Forty-three percent of fractures were nondisplaced. The remaining fractures demonstrated anterior or superior displacement of the lateral fragment, with a 0% incidence of posterior displacement. The most common indication for surgery was fracture displacement (n=10). A classification of medial clavicle fractures was developed using data from our cohort and a literature review. Medial clavicle fractures rarely demonstrate posterior displacement. Despite fracture proximity, mediastinal injury is exceedingly uncommon. [Orthopedics. 202X;XX(X):xx-xx.].

Morphology of the acromioclavicular-joint score (MAC)

INTRODUCTION

To date there is no generally accepted specific definition or classification of acromioclavicular (AC) joint osteoarthritis. The aim of this study is to analyze morphological parameters using magnetic resonance imaging (MRI) and to develop a scoring system as a basis for decision making to perform an AC-joint resection.

MATERIALS AND METHODS

In a retrospective-monocentric matched pair study, healthy and affected subjects were investigated using T2 MRI scans in the transverse plane. There were two groups, group 1 (n = 151) included healthy asymptomatic adults with no history of trauma. In group 2, we included n = 99 patients with symptomatic AC joints, who underwent arthroscopic AC-joint resection. The central and posterior joint space width and the AC angle were measured. Morphological changes such as cartilage degeneration, cysts and bone edema were noted. Malalignment of the joint was defined as: posterior joint space width < 2 mm in conjunction with an AC angle > 12°. A scoring system consisting of the measured morphologic factors was developed.

RESULTS

Symptomatic and asymptomatic patients showed significant differences in all measured items. We observed a significant difference in the MAC score for symptomatic and asymptomatic patients (mean 10.4 vs. 20.6, p = 0.0001). The ROC (receiver operator characteristic) analysis showed an excellent AUC of 0.899 (p = 0.001). The sensitivity of the MAC score was 0.81 and the specificity 0.86. The MAC score shows a significant moderate correlation with age (r = 0.358; p = 0.001). The correlation of age and the development of symptoms was only weak (r = 0.22, p = 0.001). Symptomatic patients showed significantly more frequent malalignment compared to asymptomatic patients (p = 0.001), but the positive predictive value that a patient with malalignment is also symptomatic is only 55%.

CONCLUSION

Patients with symptomatic AC joints showed a typical pattern of morphological changes on axial MRI scans with early posterior contact of the joint surfaces, reduction of joint space and malalignment as the basis for the development of a scoring system. The MAC score shows excellent test characteristics, and therefore, proved to be both an appropriate guidance for clinical practice as well as an excellent tool for comparative studies and is superior to the assessment of malalignment alone.

LEVEL OF EVIDENCE

Level IV, retrospective diagnostic study.

Shoulder adhesive capsulitis: can clinical data correlate with fat-suppressed T2 weighted MRI findings?

Background

Adhesive capsulitis (AC) of the shoulder or frozen shoulder is a debilitating condition characterized by progressive pain, stiffness and limited range of motion about the glenohumeral joint, the term (adhesive capsulitis) to describe the findings of chronic inflammation and fibrosis of the joint capsule, characterized by significant restriction of both active and passive shoulder motion that occurs in the absence of a known intrinsic shoulder disorder. The goal of the trial was to examine the association between clinical features (stages) and magnetic resonance imaging (MRI) findings in adhesive capsulitis of the shoulder.

Results

In our study, Regarding the diagnostic performance of shoulder MRI there is a statistically significant difference between degree of pain intensity according to Capsular thickening regarding humeral “mm” with p-value (p < 0.05). The highest value was found moderate and severe pain group (5.67 ± 1.39) compared to absent, minimal and mild pain group (4.42 ± 1.29), there was a statistically significant difference between two groups according to axillary recess regarding height “mm” with p-value (p < 0.05). The highest value was found absent, minimal and mild pain group (7.02 ± 2.68) compared to moderate and severe pain group (5.73 ± 2.25). There is no statistically significant association between pain intensity and MRI finding regarding capsular edema, extra capsular edema, obliteration of subcoracoid fat triangle, effusion of biceps tendon sheath, capsular thickening of glenoid (mm) and humeral portions of axillary recess and axillary recess width and height (mm), with p-value (p > 0.05 NS).

Conclusions

MRI is useful for assessing clinical impairment and predicting the clinical stage of adhesive capsulitis.

Concomitant coracoid base fracture and acromioclavicular joint disruption: A series of patients treated with a clavicle hook plate and review of the literature

INTRODUCTION

Concomitant acromioclavicular joint (ACJ) disruptions with coracoid base fractures are rare high energy injuries. The management of these injuries can be challenging. The aim of this study is to assess the functional and radiographic outcomes of a retrospective case series of patients presenting with concomitant ACJ and coracoid base injuries managed with a clavicle hook plate with subsequent hardware removal at a later stage.

METHODS

Six patients were identified for inclusion in the study. Radiographic and clinical data were available which allowed for collection of demographic information as well as classification of the fractures. Telephone consultation with patients allowed for collection of functional scores which included the Oxford shoulder score (OSS), QuickDASH (Q-DASH), Euroqol-5 Dimension (EQ-5D) and the SF-12 score.

RESULTS

All patients were male with a mean age of 39.8 years and a median follow-up period of 34 months. All patients underwent a successful operative procedure with a median time to union of 3.75 months. Good functional outcomes were reported by all patients: mean OSS 45.0, mean Q-DASH 4.8, mean EQ-VAS 82.8 and encouraging SF-12 scores (mean PCS 56.0, mean MCS 56.4).

CONCLUSION

The use of a lateral clavicle hook plate can achieve good healing and functional outcomes when managing patients with acromioclavicular joint disruptions associated with a coracoid base fracture.

Acromioclavicular Joint Injury and Repair

The acromioclavicular (AC) joint is commonly injured in athletes participating in contact and overhead throwing sports. Injuries range from simple sprains to complete ligamentous disruption, and they are classified by the established Rockwood grading system. High-grade injuries are associated with fractures around the AC joint and disruption of the superior shoulder suspensory complex, a ring of osseous and ligamentous structures at the superior aspect of the shoulder. Radiographs are the mainstay of imaging of the AC joint, with magnetic resonance imaging reserved for high-grade injuries to aid classification and plan surgical management. Low-grade AC joint injuries tend to be managed conservatively, but a wide range of surgical procedures have been described for higher grade injuries and fractures around the AC joint. This review illustrates the anatomy of the AC joint and surrounding structures, the imaging features of AC joint injury, and the most commonly performed methods of reconstruction and their complications.

The Role of the Trapezius in Stabilization of the Acromioclavicular Joint: A Biomechanical Evaluation

Background

Acromioclavicular joint (ACJ) injuries are common, and many are adequately treated nonoperatively. Biomechanical studies have mainly focused on static ligamentous stabilizers. Few studies have quantified ACJ stabilization provided by the trapezius.

Purpose/Hypothesis

To elucidate the stabilization provided by the trapezius to the ACJ during scapular internal and external rotation (protraction and retraction). It was hypothesized that sequential trapezial resection would result in increasing ACJ instability.

Study Design

Controlled laboratory study.

Methods

A biomechanical approach was pursued, with 10 cadaveric shoulders with the trapezius anatomically force loaded to normal. The trapezius was then serially transected over 8 trials, which alternated between clavicular defects (CD) and scapular defects (SD); each sequential defect consisted of 25% of the clavicular or scapular trapezial attachment. After each defect, specimens were tested with angle-controlled scapular internal and external rotation (12°) with rotary torque measurements to evaluate ACJ stability.

Results

The mean resistance in rotary torque for 12° of scapular internal rotation (protraction) with native specimens was 7.0 ± 2.0 N·m. Overall, internal rotation demonstrated a significant decrease in ACJ stability with trapezial injury (P < .001). Eight sequential defects resulted in the following significant percentage decreases in rotary torque from native internal rotation: 1.5% (25% CD; 0% SD), 5.6% (25% CD; 25% SD), 5.1% (50% CD; 25% SD), 6.5% (50% CD; 50% SD), 3.8% (75% CD; 50% SD), 7.1% (75% CD; 75% SD), 6.7% (100% CD; 75% SD), and 12.3% (100% CD 100% SD) (P < .001). The mean resistance in rotary torque for 12° of scapular external rotation (retraction) with native specimens was 7.1 ± 1.7 N·m. External rotation did not demonstrate a significant decrease in ACJ stability with trapezial injury (P = .596). The 8 sequential defects resulted in decreases in rotary torque from native external rotation of 0%, 3.8%, 4.0%, 3.2%, 3.5%, 3.4%, 4.2%, and 0.7%.

Conclusion

Trapezial injury resulted in increased instability in the setting of scapular internal rotation (protraction) of the ACJ.

Clinical Relevance

These findings validate the inclusion of deltotrapezial fascial injury consideration in the modified Rockwood classification system. Repair of the trapezial insertion on the ACJ may provide improved outcomes in the setting of ACJ reconstruction.

The effects of limb laterality and age on the inflammation and bone turnover of the acromioclavicular shoulder joint: 18 F-fluorodeoxyglucose and 18 F-sodium-fluoride-PET/computed tomography study

PURPOSE

The acromioclavicular (AC) joint is a common site of injury and degenerative changes such as osteoarthritis (OA) of the shoulder. Physical manifestations of OA are preceded by molecular changes, detection of which may enhance early prophylaxis and monitoring of disease progression. In this study, we investigate the use of 18 F-FDG and 18 F-NaF-PET/CT to assess the effects of limb laterality and age on the inflammation and bone turnover of the AC shoulder joint.

METHODS

We analyzed FDG and NaF-PET/CT scans of 41 females (mean age of 43.9 ± 14.2 years) and 45 males (mean age of 44.5 ± 13.8 years) using a semiquantitative technique based on predefined ROI.

RESULTS

There was a greater NaF uptake in the right side of the AC joint compared with the left in both females (left: 2.22 ± 1.00; right: 3.08 ± 1.18; P < 0.0001) and males (left: 2.57 ± 1.49; right: 2.99 ± 1.40; P = 0.003). No consistent correlation between age and NaF or FDG uptakes were found in both females and males. There was also a positive correlation between FDG and NaF uptakes in both left ( P = 0.01; r = 0.37) and right ( P = 0.0006; r = 0.53) AC joints of male subjects.

CONCLUSION

Our study is the first to reveal the varying effect of right-left limb laterality and aging on FDG and NaF uptake at the AC joint. Future studies correlating the history of shoulder trauma, pain, and degenerative change with FDG and NaF-PET/CT findings will be critical in the adoption of molecular imaging in the clinical setting.

Zero Echo Time Musculoskeletal MRI: Technique, Optimization, Applications, and Pitfalls

Zero echo time (ZTE) imaging is an MRI technique that produces images similar to those obtained with radiography or CT. In ZTE MRI, the very short T2 signal from the mineralized trabecular bone matrix and especially cortical bone-both of which have a low proton density (PD)-is sampled in a unique sequence setup. Additionally, the PD weighting of the ZTE sequence results in less contrast between soft tissues. Therefore, along with gray-scale inversion from black to white and vice versa, ZTE imaging provides excellent contrast between cortical bone and soft tissues similar to that of radiography and CT. However, despite isotropic or near-isotropic three-dimensional (3D) imaging capabilities of the ZTE sequence, spatial resolution in this technique is still inferior to that of radiography and CT, and 3D volume renderings are currently time-consuming and require postprocessing software that features segmentation and manual contouring. Optimization of ZTE MRI mostly entails adjustments of bandwidth, flip angle, field of view, and image matrix. A wide range of structural abnormalities and disease or healing processes in the musculoskeletal system are well delineated with ZTE MRI, including conditions that involve bone-based morphometric analyses (which aid diagnosis, help prognostication, and guide surgery), impaction, avulsion and stress fractures, loose bodies or erosions in and around joints, soft-tissue calcifications and ossifications, and bone tumors (including treatment response). The pitfalls of ZTE imaging include mimics of foci of calcification or ossification such as intra-articular gas and susceptibility artifacts from surgical materials and hemosiderin deposition, which can be avoided in many instances by cross-referencing images obtained with other MRI sequences. Online supplemental material is available for this article. ^©RSNA, 2022.

Anatomical variants of the acromioclavicular joint influence its visibility in the standard MRI protocol in patients aged 18-31 years

Purpose

Visualization of a structure in orthogonal planes is essential for correct radiological assessment. The aim was to assess the utility of the standard MRI protocol for the shoulder in the assessment of the acromioclavicular joint (ACJ).

Methods

A total of 204 MRI scans of the shoulder were re-reviewed. Visibility of the ACJ in orthogonal planes was assessed, and the type of acromion and the angle between the ACJ and the glenoid cavity were assessed by two observers.

Results

Agreement in the assessment of ACJ visibility was moderate to substantial. The ACJ was visible in the three anatomical views in 48% (confidence interval [CI] 95% = [41–54%]) of the examinations, and no significant difference regarding gender or age was noticed. The mean angle between the ACJ and the glenoid cavity was 41.12 deg. CI95% = (39.72, 42.53) in the axial plane, 33.39 deg. CI95% = (31.33, 35.45) in the coronal plane and 52.49 deg. CI95% = (50.10, 54.86) in the sagittal plane. When the ACJ was visible in the sagittal and axial planes, significant differences were noticed in the remaining planes (p < .05).

Conclusion

Anatomical variations of the ACJ influence its visibility in the standard MRI protocol for examining the shoulder, making this protocol insufficient for ACJ assessment in the examined population.

Imaging of traumatic shoulder injuries – Understanding the surgeon’s perspective

Imaging plays a key role in the assessment and management of traumatic shoulder injuries, and it is important to understand how the imaging details help guide orthopedic surgeons in determining the role for surgical treatment. Imaging is also crucial in preoperative planning, the longitudinal assessment after surgery and the identification of complications after treatment. This review discusses the mechanisms of injury, key imaging findings, therapeutic options and associated complications for the most common shoulder injuries, tailored to the orthopedic surgeon’s perspective.

Imaging Utilization Patterns and Injury Characteristics Associated with Electric Standing Scooters in a Major Urban Area

BACKGROUND

The recent proliferation of electric standing scooters in major urban areas of the United States has been accompanied by injuries of varying severity and nature, representing a growing public health concern.

OBJECTIVE

Our aim was to characterize imaging utilization patterns for injuries associated with electric scooter (e-scooter) use, including their initial emergency department (ED) management.

METHODS

We conducted a retrospective review of the electronic medical record for all patients presenting to affiliated EDs for e-scooter-related injuries between July 2018 and April 2020. Demographics, date and time of presentation, imaging study type, resultant injury, and procedural details were recorded.

RESULTS

Ninety-seven patients were included; mean age was 27.6 years. Of these, 55 patients (57%) had injuries identified on imaging and 40% of all imaging studies were positive. Most identified injuries (61%) were musculoskeletal, with a small number of neurological (2%) and genitourinary (1%) injuries. The highest prevalence of presentations occurred in August; most patients (72%) presented between 3 pm and 1 am and granular peaks were between 12 am and 1 am and 5 pm and 6 pm.

CONCLUSIONS

Patients presenting with e-scooter injuries have a high likelihood of injury to the radial head, nasal bone, and malleoli. Emergency physicians should be especially vigilant for injuries in these areas at presentation. Visceral injuries are uncommon but may be severe enough to warrant surgery.

Os acromiale may be a contraindication of the clavicle hook plate: case reports and literature review

Background

Os acromiale can be potentially missed or misdiagnosed as acromion fracture, and this can affect treatment determination if it is complicated with an ipsilateral shoulder injury. The clavicle hook plate is a widely used technique for distal clavicle injuries, leading to transacromial erosion, particularly when in the presence of os acromiale.

Case presentation

A 70-year-old man and a 78-year-old man who had limited mobility and severe pain in their right shoulders following falls attended the emergency center. Both patients were diagnosed with os acromiale with CT or MRI and acute distal clavicle fracture or acromioclavicular joint dislocation. Following a comprehensive evaluation, os acromiale may limit the application of a clavicle hook plate due to potential transacromial erosion. The distal clavicle fracture with ipsilateral os acromiale received treatment with a volar radius locking T plate, and the acromioclavicular joint dislocation with ipsilateral os acromiale was reconstructed using suture anchors. Both yielded satisfactory outcomes and voided transacromial erosion.

Conclusions

Ipsilateral os acromiale may be a relative contraindication to the clavicle hook plate. An axillary lateral radiograph is recommended to detect potential os acromiale in patients using a hook plate.

Revising the modified Neer classification for distal clavicle fractures: Description and reliability

BACKGROUND

The modified Neer classification is the most widely used classification system for distal clavicle fractures. However, it provides limited information for treatment decisions. The objective of this study was to revise the modified Neer classification to make it more suitable for treatment decision-making.

HYPOTHESIS

The revised version of the modified Neer classification has good intra- and interobserver agreements and provides an instructive treating algorithm.

STUDY DESIGN

Cohort study METHODS: Six observers, including three experienced shoulder specialists and three junior orthopaedic residents, independently reviewed plain radiographs of 52 patients with distal clavicle fractures. They were asked to classify the fracture types according to the modified Neer classification and our revised new classification separately to determine treatment approaches for each patient. Images were mirrored and randomized to verify the intraobserver agreement. Reliabilities were measured using the Fleiss kappa values.

RESULTS

Both the modified Neer classification and our revised version had near perfect intraobserver agreement (κ values: 0.87-1.00), whereas our revised Neer classification had a better interobserver agreement (κ values: 0.78 vs. 0.70, z = 4.70, p < 0.01) and stronger relevance to treatment decisions (coefficient of contingency: 0.70 vs. 0.44).

CONCLUSION

Our study demonstrated a near-perfect intraobserver and substantial interobserver agreement of the revised new classification, indicating that our revised new classification was better than the modified Neer classification. Meanwhile, our revised classification brought few disputes in treatment selection.

CLINICAL RELEVANCE

The modified Neer classification was revised to make it more accurate and suitable for guiding treatment.

TYPE OF STUDY

Study of diagnostic test LEVEL OF STUDY: Level II.

Triple-Endobutton and clavicular hook: A propensity score matching analysis

We retrospectively analyzed the clinical data of 635 patients with acute acromioclavicular dislocation, who underwent surgery in our hospital between May 2014 and June 2020. Patients were divided into group A (clavicular hook plate) and group B (Triple-Endobutton plates via double-incision). The propensity score analysis using one to one match was performed for comparisons. We obtained 292 matched patients’ data. The matched preoperative clinical characteristics were a balance between the two groups. All clinical parameters showed insignificant differences (P > 0.05). Compared with group A, group B has longer operative time (P < 0.001) and more blood loss (P < 0.001); however, the mean incision length (P < 0.001) and length of hospitalization (P < 0.001) were shorter in group B than in the group A. The mean VAS in group B were significantly lower than in group A at each time point (P < 0.001), and the UCLA shoulder score was higher in the group B. The CMS scores were also higher in group B than in group A, including before removal and 12 weeks after removal (P < 0.001). The clinical efficacy of the double-incision Triple-Endobutton plate is better than the clavicular hook plate technology, and achieves anatomical reduction by reconstructing coracoclavicular ligament.

Nonanatomic and Suture-Based Coracoclavicular Joint Stabilization Techniques Provide Adequate Stability at a Lower Cost of Implants in Biomechanical Studies When Compared With Anatomic Techniques: A Systematic Review and Meta-Analysis

Purpose

To compare the stability and cost of the used implants in nonanatomic and anatomic acromioclavicular joint repair/reconstruction (ACCR) techniques tested in cadaveric shoulder biomechanical studies during the last decade.

Methods

A systematic review and meta-analysis were performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and prospectively registered in PROSPERO. Two independent reviewers searched PubMed, Embase, and Virtual Health Library databases. Studies evaluating 3-direction stability under 70-N loads and load-to-failure protocols with servohydraulic testing systems were included. A meta-analysis of the mean differences of anterior, posterior, and superior direction; relative stability value in 3 directions; superior direction load-to-failure; stability/cost index; and load-to-failure/cost index was performed using a continuous random-effects model and 95% confidence interval.

Results

Eighteen articles were included. Both non-ACCR and ACCR techniques exceeded the minimum acceptable threshold of stability and load-to-failure. ACCR techniques were biomechanically better in terms of anterior stability (P = .04) and relative stability value (mean difference 64.08%, P = .015). However, supraphysiological stability and failure loads were achieved with non-ACCR techniques at a lower cost of implants. Techniques combining 2 clavicular tunnels separated by at least 10 mm, a mean of 2 sutures, and/or suture tapes had the greatest stability/cost index and load-to-failure/cost index among the included techniques (confidence interval 99%).

Conclusions

Non-ACCR and ACCR techniques exceeded the minimum acceptable threshold of stability and failure loads in controlled biomechanical testing. However, non-ACCR and techniques combining 2 clavicular tunnels separated by at least 10 mm, a mean of 2 sutures, and/or suture tapes provide supraphysiologic stability and failure loads at a lower cost of implants.

Clinical Relevance

Non-ACCR and suture-based techniques may provide more cost-effective and greater value treatment for acromioclavicular joint injury and could be considered in the surgical management of normal activity individuals and cost-sensitive populations.