Analysis of predisposing factors in elderly people with type II odontoid fracture.

BACKGROUND CONTEXT

Type II odontoid fracture is the most frequent individual fracture in elderly people. An older person usually sustains a Type II odontoid fracture in a fall from standing or a seated height. A relationship between osteoarthritis in the upper cervical spine and Type II odontoid fracture has been reported. However, to our knowledge, few reports have investigated statistically whether disproportionate degeneration between joints influences the susceptibility to fracture.

PURPOSE

The purpose of this study was to assess predisposition to Type II odontoid fracture in the elderly.

STUDY DESIGN

Retrospective review of elderly patients sustained Type II odontoid fracture and other axis fractures.

PATIENT SAMPLE

Thirty-eight patients aged 65 years and older with axis fractures.

OUTCOME MEASURES

Evaluation of computed tomography findings by focusing on osteoporosis and the disproportion in degeneration between each of the upper cervical joints (atlantooccipital, atlantoodontoid, and lateral atlantoaxial joints).

METHODS

Seventeen patients had a Type II odontoid fracture, and 21 patients had other axis fractures. Using the computed tomography findings, we classified osteoporosis at the dens-body junction and the severity of degenerative changes in the atlantoodontoid, atlantooccipital, and lateral atlantoaxial joints as none, mild, moderate, or severe. The proportion of patients with moderate or severe osteoporosis and degenerative changes in each joint and that of patients with disproportionate degenerative changes between joints (difference in grade of ≥2 levels between joints) were compared statistically. The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this article.

RESULTS

Patients with osteoporosis and with disproportionate degenerative changes between the atlantoodontoid and lateral atlantoaxial joints were significantly more likely to have a Type II odontoid fracture than other axis fractures. These two factors were also assessed in multivariate logistic analysis. The disproportionate degenerative change between the atlantoodontoid and lateral atlantoaxial joint remained significant, even after adjusting for osteoporosis.

CONCLUSIONS

Older patients with the dens fixed to the atlas because of degeneration of the atlantoodontoid joint and a smooth lateral atlantoaxial joint seem to sustain Type II odontoid fractures because, during a simple fall, the rotation of the head produces torque force on the osteoporotic dens-body junction, which acts as the rotatory center. The presence of the disproportionate osteoarthritic degeneration between the atlantoodontoid and lateral atlantoaxial joints predisposes older people to a Type II odontoid fracture.