Ligamentous and capsular restraints to anterior-posterior and superior-inferior laxity of the acromioclavicular joint: a biomechanical study

TY - JOUR

T1 - Ligamentous and capsular restraints to anterior-posterior and superior-inferior laxity of the acromioclavicular joint

T2 - a biomechanical study

AU - Lee, Jillian

AU - El-Daou, Hadi

AU - Alkoheji, Mohamed

AU - Carlos, Adrian

AU - Di Mascio, Livio

AU - Amis, Andrew

N1 - Publisher Copyright: © 2020 Journal of Shoulder and Elbow Surgery Board of Trustees

PY - 2021/6

Y1 - 2021/6

N2 - Background: Approximately 9% of shoulder girdle injuries involve the acromioclavicular joint (ACJ). There is no clear gold standard or consensus on surgical management of these injuries, in part perpetuated by our incomplete understanding of native ACJ biomechanics. We have therefore conducted a biomechanical study to assess the stabilizing structures of the ACJ in superior-inferior (SI) translation and anterior-posterior (AP) translation. Methods: Twenty fresh frozen cadaveric specimens were prepared and mounted onto a robotic arm. The intact native joint was tested in SI translation and AP translation under a 50-N displacing force. Each specimen was retested after sectioning of its stabilizing structures in the following order: investing fascia, ACJ capsular ligaments, trapezoid ligament, and conoid ligament. Their contributions to resisting ACJ displacements were calculated. Results: In the intact native ACJ, mean anterior displacement of the clavicle was 7.9 ± 4.3 mm, mean posterior displacement was 7.2 ± 2.6 mm, mean superior displacement was 5.8 ± 3.0 mm, and mean inferior displacement was 3.6 ± 2.6 mm. The conoid ligament was the primary stabilizer of superior displacement (45.6%). The ACJ capsular ligament was the primary stabilizer of inferior displacement (33.8%). The capsular ligament and conoid ligament contributed equally to anterior stability, with rates of 23% and 25.2%, respectively. The capsular ligament was the primary contributor to posterior stability (38.4%). Conclusion: The conoid ligament is the primary stabilizer of superior displacement of the clavicle at the ACJ and contributes significantly to AP stability. Consideration should be given to reconstruction of the ACJ capsular ligament for complete AP stability in high-grade and horizontally unstable ACJ injuries.

AB - Background: Approximately 9% of shoulder girdle injuries involve the acromioclavicular joint (ACJ). There is no clear gold standard or consensus on surgical management of these injuries, in part perpetuated by our incomplete understanding of native ACJ biomechanics. We have therefore conducted a biomechanical study to assess the stabilizing structures of the ACJ in superior-inferior (SI) translation and anterior-posterior (AP) translation. Methods: Twenty fresh frozen cadaveric specimens were prepared and mounted onto a robotic arm. The intact native joint was tested in SI translation and AP translation under a 50-N displacing force. Each specimen was retested after sectioning of its stabilizing structures in the following order: investing fascia, ACJ capsular ligaments, trapezoid ligament, and conoid ligament. Their contributions to resisting ACJ displacements were calculated. Results: In the intact native ACJ, mean anterior displacement of the clavicle was 7.9 ± 4.3 mm, mean posterior displacement was 7.2 ± 2.6 mm, mean superior displacement was 5.8 ± 3.0 mm, and mean inferior displacement was 3.6 ± 2.6 mm. The conoid ligament was the primary stabilizer of superior displacement (45.6%). The ACJ capsular ligament was the primary stabilizer of inferior displacement (33.8%). The capsular ligament and conoid ligament contributed equally to anterior stability, with rates of 23% and 25.2%, respectively. The capsular ligament was the primary contributor to posterior stability (38.4%). Conclusion: The conoid ligament is the primary stabilizer of superior displacement of the clavicle at the ACJ and contributes significantly to AP stability. Consideration should be given to reconstruction of the ACJ capsular ligament for complete AP stability in high-grade and horizontally unstable ACJ injuries.

KW - Acromioclavicular joint stability

KW - anterior-posterior laxity

KW - Basic Science Study

KW - Biomechanics

KW - capsular restraint

KW - coracoclavicular ligament

KW - robotic test

KW - superior-inferior

UR - http://www.scopus.com/inward/record.url?scp=85106346342&partnerID=8YFLogxK

U2 - 10.1016/j.jse.2020.09.006

DO - 10.1016/j.jse.2020.09.006

M3 - Article

C2 - 33010434

AN - SCOPUS:85106346342

SN - 1058-2746

VL - 30

SP - 1251

EP - 1256

JO - Journal of shoulder and elbow surgery

JF - Journal of shoulder and elbow surgery

IS - 6

ER -