Quantitative anatomic study of atlanto-odontoid joint and design of an artificial atlanto-odontoid joint for the orthopedic clinic.

OBJECTIVE

To observe and measure morphological parameters of the Chinese atlanto-odontoid joint anatomically in order to provide an anatomic data for designing artificial atlanto-odontoid joint used for substituting the destroyed atlanto-odontoid joint in the orthopedic clinic.

METHODS

The relative anatomic parameters of 32 sets of fresh Chinese adults'atlanto-odontoid joint specimens were measured with a digital caliper and a goniometer, including the width of anterior arch of atlas (AW), the thickness of atlas at the junction of anterior arch and lateral mass (AD), the thickness and height of anterior tubercle of atlas (AT and AH), the middle height, length and width of the lateral mass (MHL, L and LW), the height, transverse and anteroposterior distance of odontoid process (DH, DW and DD), the retroversion angle of odontoid process (beta degree),the facial angle of odontoid process (theta degree) and so on. The data were statistically analyzed in order to ascertain the morphological parameter ranges of artificial atlanto-odontoid joint. An artificial atlanto-odontoid joint was designed according to these data. The operations of anlanto-odontoid joint arthroplasty were conducted in 3 cases of adult cadaver specimens.

RESULTS

The width of AW was (20.45+/-1.53) mm, AD (3.91+/-1.32) mm, AT and AH (9.43+/-1.93)mm and (10.23+/-1.32) mm, respectively, MHL and LW (13.68+/-1.38) mm and (12.98+/-1.52) mm, respectively, DH (15.25+/-2.11) mm, DW and DD (9.69+/-1.38) mm and (11.26+/-1.02) mm, respectively, beta degree (12.23+/-4.27) degree, theta degree (65.48+/-2.17) degree. The prosthesis was composed of atlas part, axis part and accessories. Neither the vertebral artery nor the medulla oblongata was injured.

CONCLUSIONS

The design of artificial atlanto-odontoid joint is feasible according to these parameters. The artificial joint can not only rebuild the stability of atlanto-axial joint, but also reserve the rotation function between atlas and axis. Every part of the joint has their own parameter ranges in purpose to firm fixation, convenient operation and good motion without further injury. The prosthesis can be used for patients suffering from compression of medulla oblongata and resection of dens when it is required.