Congenital Atlantoaxial Dislocation: Nature's Engineering Gone Wrong and Surgeon's Attempt to Rectify It.

Abstract

The C1-2 joint is unique and is responsible for more than 50% of the neck rotation. The joints have an ergonomic design that allows maximum motion without getting dislocated. It provides six degrees of freedom, the maximum being axial rotation, and is a marvel of nature's engineering. The morphometry of lateral masses of C1 and C2 joints was analyzed to explain the possible movements despite minor variations. The normal morphometry was compared with the joints of individuals with congenital atlantoaxial dislocation. The structural flaws were assessed to understand the forces leading to dislocation in various planes. The surgical correction of such flaws and engineering involved has been discussed. The joints of patients with congenital atlantoaxial dislocation are deformed and the lateral masses are trapezoidal as compared to the cuboidal lateral masses of normal individuals. The orientation of joints decides the direction and rate of slip of C1 over C2. Surgical correction of the joints is possible by drilling them, aiding in reduction, and preventing redislocation. The construct needs to be as close to the C1-2 joints as possible. Studying the engineering in naturally occurring joints gives us a chance to understand the dynamics of the abnormal ones. Correcting the deformed joints to near-normal ones makes realignment possible in all planes and helps in understanding the best construct to fuse them. Mimicking the naturally occurring joints can help us in developing prosthesis for C1-2 arthroplasty.