In vivo study on three-dimensional structure of lumbar facet joints based on computerassisted medical image processing method / 医用生物力学

ABSTRACT

Objective To study three-dimensional feature of the thickness of subchondral cortical bone, the surface area and space width of the facet joints as well as its morphological characteristics and variation, and to compare the differences of these parameters in patients with low back pains and healthy people, based on three dimensional reconstruction images of the facet joints. Methods CT scanning from L1/2 to L5/S1 at supine position was performed on 90 subjects to obtain two-dimensional images of the facet joints and three-dimensional point-cloud data of the subchondral cortical bone, the surface area and space width of the facet joints after reconstruction. Distributions of these parameters between the superior and inferior facet joints and at different regions of the articular process were investigated, and differences of these parameters in lumbar segments, gender, age and symptoms were also compared. Results (1)At superior facet, the largest thickness was located at the cranial region, while at inferior facet, it was located at the caudal region. The thickness of subchondral cortical bone was significantly smaller at central region than at the other regions. A more obvious difference could be observed at the lower lumbar levels（L4/5, L5/S1）. (2)The average surface area of the facet joints was (173.2±3.6) mm2, and it was increased with the lumbar level and age increasing, especially at the L4/5 level and at the age of more than 40. The surface area of superior facet joints was significantly larger than that of inferior facet joints for patients with low back pains (except at L5/S1 level), who had an obviously larger surface area of the facet joints than healthy people. (3)The average thickness of space width of the facet joints was (1.46±0.08) mm, and it was decreased with age decreasing, especially at the age of more than 40. The female had significantly larger space width than the male, while patients with low back pains had significantly smaller space width. At each facet joint, the space at cranial region was significantly larger than that at caudal region, and it was also significantly larger at central region than at surrounding region. These differences were more obvious at the lower three lumbar levels. Conclusions Computer-assistant image processing and reconstruction analysis techniques can accurately measure the relative parameters of lumbar facet joints with complicated structure in three dimensional space. The feature of the facet joints was correlated with shape of the facet joint surface，stress on the joint and degeneration of the joint, so it was a reflection of adaptive changes in human body structure due to the long-term loading on the facet joint.