gms | German Medical Science

Objectives: The synergistic effect of the AC capsule and CC ligaments for AC joint stability have gained recent importance. Current biomechanical and clinical studies show the benefit of a combined reconstruction. The best configuration of such repair of the capsule is still unknown. The hypothesis was that techniques which reconstruct the capsular structures anatomically provide the highest resistance against translational and rotational stresses.

Methods: 30 cadaveric shoulders were used. After complete capsulotomy one of five published AC capsule suture configurations were installed and tested. 4 configurations were used: 1) anterior; 2) superior; 3) posterior; 4) O-frame; 5) X-frame. Followed by dissection of the CC ligaments and CC reconstruction (suture button system). Stability was tested under rotational and horizontal translation. A servohydraulic testing system (MTS Systems Corp) was used for testing. Posterior translation, rotation, and displacement of the lateral clavicle (3D optical measuring system) in relation to the center of rotation were measured. Torque and axial forces required to rotate and translate the clavicle were recorded.

Results and conclusion:

Translation: All suture configurations were able to significantly increase the resistance force to 71% ± 33 compared to the native (p=0.01). Values closest to native were seen for the anterior suture configuration 91% ± 38 and lowest values were present in the superior suture configurations (64% ± 17) without significant differences (p=0.73). AC capsule augmentation combined with CC ligament reconstruction showed the highest percentage of resistance force 101% ± 35 with no significant difference to the native specimen (p=1.0).

Rotation: All AC suture constructs were able to significantly increase the resistance force back to 32% ± 23 (p=0.01) against rotational stress. Closest to native values were seen for the X-framed construct with 42% ± 25 and lowest values were archived with the posterior suture configurations group averaging 21% ± 20 without showing any significant change between repair configurations (p=0.63). The combined AC- and CC ligament reconstruction achieved again the highest percentage of regained resistance force (37% ± 29), but remaining significantly weaker than native (p=0.01). The final construct was strongest when the anterior suture construct 49% ± 32 was installed and weakest for the superior suture construct 29% ± 31 without significant differences between any of the groups (p=0.28).

Stability of the AC joint could significantly be improved by all techniques. Individual tendencies were observed (with non signif., advantages for the reconstruction of the anterior capsular structures). If combined with CC repair, native stability could be restored. A combined stabilization therefore restores the native stability against translational and rotational stress best but configuration can be chosen according to surgeons preference.