Kinematic Alterations in the Shoulder Complex in Rockwood V Acromioclavicular Injuries During Humerothoracic and Scapulothoracic Movements: A Whole-Cadaver Study

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.

The V angle compliments radiographic assessment of acute acromioclavicular joint dislocations by differentiating between Rockwood types III versus V and by considering dynamic horizontal translation in coronal radiographs

PURPOSE

Acromioclavicular joint (ACJ) dislocations are usually graded radiographically according to Rockwood, but differentiation between Rockwood types III and V may be ambiguous. The potentially clinically relevant horizontal instability is barely addressed in coronal radiographs. It was hypothesized that a new radiologic parameter (V angle) would complement ACJ diagnostics on anteroposterior radiographs by differentiating between cases of Rockwood III and V while also considering the aspect of dynamic horizontal translation (DHT).

METHODS

Ninety-five patients with acute ACJ dislocations (Rockwood types III and V) were included retrospectively between 2017 and 2020. On anteroposterior views (weightbearing: n = 62, non-weight-bearing: n = 33), the coracoclavicular (CC) distance and the newly introduced V angle for assessing scapular orientation were measured bilaterally. This angle is referenced between the spinal column and a line crossing the superior scapular angle and the crossing point between the supraspinatus fossa and the medial base of the coracoid process, reported as the side-comparative difference (non-injured side *minus* injured side). DHT on Alexander views was divided into stable, partially unstable or completely unstable.

RESULTS

The V angle on the injured side alone (mean 50.0°; 95% confidence interval (CI), 48.6°-51.3°) showed no correlation with the side-comparative CC distance [%] (r = - 0.040; n.s.). Thus, the V angle on the non-injured side was considered, displaying a normal distribution (n.s.) with a mean of 58.0° (95% CI, 56.6°-59.4°). The side-comparative V angle showed a correlation with the side-comparative CC distance (r = 0.83; p < 0.001) and was able to differentiate between Rockwood types III (4.7°; 95% CI, 3.9°-5.5°; n = 39) and V (10.3°; 95% CI, 9.7°-11.0°; n = 56) (p < 0.001). A cut-off value of 7° had a 94.6% sensitivity and an 82.1% specificity (area under curve, AUC: 0.954; 95% CI, 0.915-0.994). The side-comparative V angle was greater for cases with complete DHT (8.7°; 95% CI, 7.9°-9.5°; n = 78) than for cases with partial DHT (4.8°; 95% CI, 3.3°-6.3°; n = 16) (p < 0.001). A cut-off value of 5° showed a sensitivity of 84.6% and a specificity of 66.7% (AUC 0.824; 95% CI, 0.725-0.924).

CONCLUSION

The scapular-based V angle on anteroposterior radiographs distinguishes between Rockwood types III and V as well as cases with partial or complete DHT.

STUDY DESIGN

Diagnostic study.

LEVEL OF EVIDENCE

Level II.

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.

Management of Acromioclavicular Injuries - Current Concepts

Introduction

Treatment of a patient with acromioclavicular joint (ACJ) injury remains challenging for orthopedic surgeons. To date, there is debate over the optimal management of ACJ injuries. This review provides an overview of assessment, treatment, and future perspectives for the treatment of and research into ACJ.

Material and Methods

A scoping literature review was performed. The search was built including the following terms: acromioclavicular joint injuries or dislocation, and pathophysiology, etiology, anatomy, treatment, and trauma mechanism. The papers with evidence levels 1-3 were included in the current narrative review.

Results

A total of 2242 potential relevant studies were identified in the searches. After removal of duplicates, 432 studies were screened on their titles and abstracts, resulting in 35 studies being included in the review, based on the eligibility criteria.

Conclusion

The management of acute and chronic ACJ injuries is not clarified in the current literature. However, there is currently insufficient high-level evidence for the overall treatment options for ACJ injuries. If surgical intervention is decided upon in consultation with the patient, the complications may not outweigh the benefits. The multitude of existing techniques is indicative of the uncertainty surrounding this issue, and no gold standard has yet been established for treatment methods. An ideal classification would include not only vertical and horizontal instability, but also the severity of kinematic alterations of the shoulder complex. This indicates the need for a new and improved diagnostic tool for the classification of ACJ injuries.

The German version of the Nottingham Clavicle Score is a reliable and valid patient-reported outcome measure to evaluate patients with clavicle and acromioclavicular pathologies

PURPOSE

The Nottingham Clavicle Score (NCS) is a patient-reported outcome measure developed to evaluate treatment results of clavicle, acromioclavicular and sternoclavicular joint pathologies. Valid, reliable and user-friendly translations of outcome measure instruments are needed to allow comparisons of international results. The aim of this cross-sectional study was to translate and adapt the NCS into German and evaluate the psychometric properties of the German version.

METHODS

The translation and cross-cultural adaptation of the NCS were completed using a 'translation-back translation" method and the final version was administered to 105 German-speaking patients. The psychometric properties of this version (NCS-G) were evaluated in terms of feasibility, reliability, validity and sensitivity to change.

RESULTS

No major differences occurred between the NCS translations into German and back into English, and no content- or linguistic-related difficulties were reported. The Cronbach's alpha for the NCS-G was 0.885, showing optimal internal consistency. The Intraclass Correlation Coefficient for test-retest reliability was 0.907 (95% CI 0.844-0.945), with a standard error of measurement of 5.59 points and a minimal detectable change of 15.50 points. The NCS-G showed moderate to strong correlation with all other investigated scales (Spearman correlation coefficient: qDASH: ρ =  - 0.751; OSS: ρ = 0.728; Imatani Score: ρ = 0.646; CMS: ρ = 0.621; VAS: ρ =  - 0.709). Good sensitivity to change was confirmed by an effect size of 1.17 (95% CI 0.89-1.47) and a standardized response mean of 1.23 (95% CI 0.98-1.45).

CONCLUSIONS

This study demonstrated that NCS-G is reliable, valid, reproducible and well accepted by patients, showing analogous psychometric properties to the original English version.

LEVEL OF EVIDENCE

Level III.

Konservative Therapie von Verletzungen des Akromioklavikulargelenks

Niedriggradige Verletzungen (Grad I und II nach Rockwood) des Akromioklavikulargelenks (ACG) können in den meisten Fällen mit gutem Outcome konservativ behandelt werden. Hierbei gibt es keine Methode der Immobilisation, welche sich als Überlegen herausgestellt hätte. Höhergradige Verletzungen (Grad IV und V), welche eine relevante Instabilität und konsekutiv häufig eine Dyskinesie des skapulothorakalen Rhythmus zur Folge haben, profitieren von einer chirurgischen Rekonstruktion. Kein Konsens trotz breiter akademischer Diskussion besteht bei Grad-III-Verletzungen. In Langzeitstudien und im Rahmen von Metaanalysen zeigten sich keine Vorteile eines operativen Vorgehens gegenüber der konservativen Behandlung nach 1 bis 2 Jahren, während einzelne Fallserien Vorteile in der anatomischen Rekonstruktion aufzeigten, insbesondere wenn für das ACG spezifische Outcome-Scores verwendet wurden. In Grenzfällen sollte das individuelle Arbeits- und Sportprofil, insbesondere regelmäßige Überkopfaktivität, in die therapeutische Entscheidungsfindung einfließen. Sowohl bei niedrig- wie auch hochgradigen Verletzungen des ACG kann durch eine fokussierte Therapie zur Verbesserung der skapulothorakalen Mobilität und Stabilität eine Skapuladyskinesie in vielen Fällen (gelegentlich auch ≥ Grad III nach Rockwood) vermieden oder erfolgreich behandelt werden.

Combined Vertical, Horizontal, and Rotational Acromioclavicular Joint Stabilization: "Closing the Circle" Technique

The biomechanical and anatomical complexity of the acromioclavicular joint makes its repair techniques particularly challenging. High rates of reduction subsidence and construction failures transversally affect both anatomic and nonanatomic repair techniques. The importance of addressing both vertical and horizontal instability has been highlighted in recent years. The authors aim to describe a surgical technique that combines vertical, horizontal, and rotational stabilization, in an attempt to restore the coracoacromioclavicular circle of stability.

Differences between Coracoclavicular, Acromioclavicular, or Combined Reconstruction Techniques on the Kinematics of the Shoulder Girdle

BACKGROUND

Although the coracoclavicular (CC) ligaments are classically reconstructed after acromioclavicular (AC) joint injuries, biomechanical studies over the past decade have indicated the importance of an additional reconstruction of the AC ligaments. To date, no kinematic study has investigated the kinematic differences between these reconstruction strategies.

PURPOSE

To evaluate the restoration of shoulder motion after an AC injury using a CC ligament, an AC ligament, or a combined reconstruction technique.

STUDY DESIGN

Controlled laboratory study.

METHODS

After creating a Rockwood grade V lesion in 14 cadaveric shoulders, the AC joint injury was treated with either a CC ligament reconstruction using a suspension device, an in situ AC ligament reconstruction using 2 coupled soft tissue anchors, or a combination of these 2 techniques. Joint motions were registered during humerothoracic elevation in the coronal plane and protraction in the intact shoulder in a Rockwood V lesion and after the 3 reconstruction strategies. An optical navigation system measured 3-dimensional rotation in the sternoclavicular and scapulothoracic joints, and both rotation and translation were analyzed in the AC joint.

RESULTS

In the sternoclavicular joint, the CC and combined reconstruction techniques adequately restored clavicular axial rotation, while the AC reconstruction technique showed a better correction of clavicular elevation. Scapulothoracic joint rotations were best restored by reconstructing the AC ligaments. In the AC joint, the relative tilting position and the lateral rotation of the scapula compared with the clavicle were best restored by the suspension device and combined reconstruction. The AC ligament reconstruction technique demonstrated a better restoration of the relative protracted position and resulted in a better correction of the translation of the scapula relative to the clavicle.

CONCLUSION

This study illustrates that there are kinematic differences between AC, CC, or combined ligament reconstruction strategies. Although each technique was able to restore different elements of the joint kinematics, none of the strategies completely restored the shoulder girdle to its preinjured state.

CLINICAL RELEVANCE

Humerothoracic movements after Rockwood V lesions are best restored using the CC reconstruction technique, and scapulothoracic movements are best restored using the AC ligament reconstruction technique.