The deltotrapezial fascia stabilizes the AC-joint and its reconstruction restores the horizontal stability in AC-joint separations: a biomechanical comparison

Various techniques are available for the reconstruction of acromioclavicular joint (ACJ) dislocations, with the main focus being on restoration of the AC capsule or coracoclavicular ligaments. Recent research has underlined the significance of the deltotrapezial fascia (DTF) and related muscles as dynamic stabilizers of the ACJ. The Hypothesis was that a reconstruction of the DTF increases the stability of the ACJ in the horizontal plane more than a complete transection of the fascia, while not restoring the stability of the native state. Reconstruction of the DTF increases the stability of the ACJ in the horizontal plane more than a complete transection of the fascia, while not restoring the stability of the native state. Five pairs of human cadaveric shoulders including the torsos were included in the study and underwent cyclic anterior-posterior loading using an electromechanical testing machine. The shoulders were put into 3 groups: group N (n = 10): native ACJ; group T (n = 10): ACJ with transected DTF; group R (n = 10): ACJ with reconstruction of the DTF after transection. The dislocation was recorded with a 3D optical measuring system. Group N showed a mean horizontal displacement of 2.94 mm (±1.26), group T showed a mean anterior displacement of 3.33 mm (±1.37), and group R showed a mean anterior displacement of 2.95 mm (±1.08). The mean anterior displacement for group T was significantly higher after every measured number of cycles compared with groups N and R. There was no significant difference in mean anterior displacement between groups N and R. The transection of the DTF results in significantly reduced stability in the horizontal plane of the ACJ. A reconstruction of the DTF restores the stability of the native ACJ in the horizontal plane. Further clinical and biomechanical investigations should focus on reconstruction techniques of the DTF.