CT evaluation of LIF curve entry side, local correction angle, and vertebral fracture for lumbar degenerative kyphoscoliosis

Abstract

Background: Lateral Interbody Fusion (LIF), which is minimally invasive, is rapidly spreading in spinal fusion for adult spinal deformities. We investigated which wedged-shape had an effect on the intervertebral coronal correction in lateral interbody fusion. Also we investigated the incidence of endplate and pedicle fractures.

Method: 14 cases (2 males, 12 females), 46 intervertebral space, 120 pedicles who performed lumbar anterior fusion using LIF. The intervertebral coronal angle between each vertebra was measured by preoperative and post operative CT. <Investigation 1> We divided each intervertebral space for two groups (Convex group: cage inserted from open wedge or Concave group: cage inserted from closed wedge) <Investigation 2> We divided each intervertebral space for two groups (HW group: a group with intervertebral angle of greator or equal 10° or LW group: a group with the angle less than 10°). We examine the correcting angle and the incidence of endplate and pedicle fractures. Statistical examination was performed using Fisher exact probability test and chi-square test.

Result: The endplate fractures occurred in 10 out of 46 intervertebral discs (22%) and the pedicle fracture occurred in 4 cases (3.3%) of 120 pedicles. The average correction angle of the convex group was 5.7 °, and the average correction angle of the concave group was 2.7 ° (p <0.001). The incidence of endplate fractures was 6 in 19 (32%) in the convex group and 3 out of 22 (14%) in the concave group (p >0.05). The incidence of pedicle fractures was 3 in 58 pedicles (5.2%) in the convex group and 1 in 62 pedicles (1.6%) in the concave group (p >0.05). The average correction angle for the HW group was 5.8 °, and the average correction angle for the LW group was 3.0 ° (p <0.01). The endplate fractures were 6 of 14 (43%) in the HW group and 4 of 32 (13%) in the LW group (p=0.046). Pedicle fractures occurred in 1 of 54 pedicles (1.9%) in the HW group and 3 of 66 pedicles in the LW group (4.5%) (p >0.05).

Discussion: A larger correction can be obtained by cage insertion from convex side with lumbar degenerative kyphoscoliosis. Also a larger correction can be obtained by cage insertion into large wedge but endplate fracture is more frequent. It is necessary to pay attention to postoperative correction loss due to endplate fractures in intervertebral vertebrae with strong wedge-shaped deformation.