Objectives The apparent relevance of the coracoclavicular ligaments (CCL) for the integrity
of the acromioclavicular (AC) joint have been subject to multiple studies over the
last decades. Only few attention has been given specifically to the anatomy and biomechanical
properties of the medial coracoclavicular ligament (MCCL). The aim of this study was
to evaluate the prevalence and biomechanical properties of the MCCL.
Methods Thirty-three cadaveric shoulder specimens were carefully prepared with thorough visualization
of the MCCL. The scapula and clavicle were then embedded in a custom-made device for
directional loading tests of the AC-joint. The acromioclavicular joint capsule was
dissected and preconditioning protocols with 10 cycles of 10N were performed. Loading
protocols were performed in the anterior, posterior and vertical directions with 50N
for CCL and 20N for MCCL, as well as load-to-failure protocols in the posterior and
vertical directions. The MCCL was tested in 14 of the specimens and the CCL were tested
in 19 specimen. Linear stiffness was calculated and the values were compared between
MCCL and CCL.
Results and Conclusion The MCCL was identified in 69 % (n=23) of the specimen and lacking in 10 cases, where
no ligamentous structure medial to the CCL was found or it was not distinguishable
from surrounding tissue. The mean stiffness of MCCL was found to be lower compared
to the CCL in all directions of the limited loading tests: vertical 4.7 (1.8-8.9)
N/mm MCCL vs. 16.4 (6.3-30.6) N/mm CCL; anterior 4.1
(0.9-6.0) N/mm MCCL vs. 8.5 (2.8-16.8) N/mm CCL; posterior 3.3 (0.7-5.9) N/mm MCCL
vs. 8.9 (0.6-13.9) N/mm CCL. The average ultimate load to failure was 42.2N (4.1-113.2N)
for the MCCL and 314.6N (138.7-712.6N) for the CCL.
According to our data, the MCCL is prevalent in the majority of the cases. The actual
prevalence might even be higher in a younger population without potential prior injuries
and/or degenerative changes than in the advanced age of the specimen. We found that
the MCCL could possibly have a lesser role in the physiological composition of the
AC-joint and in the posttraumatic restoration of function, though apparently not as
durable as the CCL.
Stichwörter acromioclavicular Joint, coracoclavicular ligaments, medial coracoclavicular ligament,
biomechanic
