Original ArticleAge-related changes in axial and sagittal orientation of the facet joints: Comparison with changes in degenerative spondylolisthesis
Introduction
Degenerative spondylolisthesis is common in the elderly population and is one of the most common indications for spinal surgery in older adults [1], [2]. The facet joints provide posterior mechanical support that protects the motion segments from anterior shear forces and from excessive rotation and flexion [3], [4]. Some researchers have reported that one of the causes of degenerative spondylolisthesis is degeneration of the facet joints, in particular sagittalization of the facet joints in the axial plane [5], [6], [7], [8], [9], [10]. Furthermore, there are studies suggesting that the facet joints become more sagittal in the axial plane with advancing age [10], [11]. Although a number of studies have investigated the orientation of the facet joints in the axial plane using computed tomography (CT) or magnetic resonance imaging (MRI), there is still limited information available on the orientation of the facet joints in the sagittal plane using these modalities [8], [10]. We hypothesized that it would be important to evaluate the orientation of the facet joints not only in the axial plane but also in the sagittal plane, given that the facet joints are three-dimensional structures. To our knowledge, CT reconstruction studies of the correlation between orientation of the facet joints in the axial and sagittal planes and age have not been reported.
The primary aim of this study was to clarify the relationship between orientation of the facet joints and age in both the axial and sagittal planes using CT. A secondary aim was to improve our understanding of changes in facet joint morphology by comparing a group of control subjects (without degenerative spondylolisthesis, spondylolysis, or spondylolytic spondylolisthesis) and a group of patients with degenerative spondylolisthesis.
Section snippets
Materials and methods
This research has been approved by the IRB of the authors’ affiliated institutions. In order to evaluate the general public, we identified 628 patients (excluding orthopedic outpatients) who had undergone abdominal and pelvic CT scanning between September 2010 and January 2012 at our hospital. Patients with a history of spondylolysis, spondylolytic spondylolisthesis, previous back surgery, or metastasis to the lumbar vertebra were excluded, leaving data for 568 patients of mean age 63 (range
Interobserver and intraobserver agreement
The both interobserver and intraobserver agreements for the facet joint angle measurement were excellent (axial plane; κ = 0.93 and κ = 0.90, respectively: sagittal plane; κ = 0.90 and κ = 0.87, respectively).
Facet joint orientation in the axial plane
The facet joint angles in the axial plane did not change with age in men (Fig. 2). However, the angles decreased with age in the lower lumbar spine in women, especially at L4/5 and L5/S1; there were statistically significant differences at L4/5 between the group aged ≤50 years and the
Discussion
The main findings of this study were as follows: the facet joint angles decreased significantly with increasing age at L4/5 and L5/S1 in the axial plane and at L3/4 and L4/5 in the sagittal plane in women; the facet joint angles decreased significantly with age at L4/5 in the sagittal plane in men; the facet joint angle most affected by age in women was L4/5; the facet joint angle in patients with degenerative spondylolisthesis was decreased in both the axial and sagittal planes and facet joint
Conclusions
This study showed that facet joint angle decreases with increasing age at L4/5 and L5/S1 in the axial plane in women, at L4/5 in the sagittal plane in men, and at L3/4 and L4/5 in the sagittal plane in women. Sagittalization and horizontalization of the facet joints was found in patients with degenerative spondylolisthesis. Facet joint tropism was greater at L4/5 in the axial plane in patients with degenerative spondylolisthesis than in controls.
Conflicts of interest
None.
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