Vertical and Rotational Stiffness of Coracoclavicular Ligament Reconstruction: A Biomechanical Study of 3 Different Techniques

PURPOSE:

To compare the biomechanical stability of 3 different coracoclavicular reconstruction techniques under rotational and vertical loading using a cadaveric model.

METHODS:

12 cadaveric shoulders were used for testing. The native state was first tested then followed by 3 different reconstruction configurations using suture tapes and cortical buttons: coracoid loop (CL), single-bundle (SB), and double-bundle (DB). Superior displacement was measured by cycling an inferiorly directed force of 70N to the scapula. The rotational stiffness of the scapula was determined by cycling the scapula in rotational displacement control between 15° of internal and external rotation. The rotational stiffness of the clavicle was determined by rotating the clavicle around its long axis 20° anteriorly and 30° posteriorly in rotational displacement control. All measurements were captured over 10 cycles at a rate of 200 Hz.

RESULTS:

Both the CL and SB techniques demonstrated significantly less internal scapular rotation stiffness. (intact: 19.70± 9.07 cNm/deg, CL: 3.70± 2.63 cNm/deg, SB:4.30±2.66 cNm/deg, P <.001) External scapular rotation stiffness was significantly decreased in all techniques. (intact: 17.70± 4.43 cNm/deg, CL: 3.30± 1.37 cNm/deg, SB: 4.50± 1.56 cNm/deg, DB: 4.67± 1.99 cNm/deg, P< .001) The CL and SB reconstructions were significantly less stiff with regards to posterior rotation of the clavicle (intact: 5.60± 1.80 cNm/deg, CL: 2.90± 1.10 cNm/deg, SB: 1.40± 0.65 cNm/deg, P<.001). Anterior rotation stiffness of the clavicle was significantly lower in all of the reconstructions. (intact: 6.95± 1.90 cNm/deg, CL: 3.08± 0.84 cNm/deg, SB:3.64± 0.93 cNm/deg, DB: 4.48± 1.21 cNm/deg, P < .001) CONCLUSION: None of the described techniques provided equivalent rotational stability in all planes compared to the native state. DB reconstruction presented stiffness characteristics closest to the native state under cyclic loading during internal scapular and posterior clavicular rotation.

CLINICAL RELEVANCE:

Additional procedures such as tendon grafting or acromioclavicular ligament reconstruction may be required to control rotational stability.