Adjacent Intervertebral Disk Height Decrease Phenomenon After Single-Level Transforaminal Lumbar Interbody Fusion of the Lumbar Spine.

BACKGROUND:The increase of intradiskal pressure on the upper segment resulting from intervertebral distraction after lumbar intervertebral fusion decreases intervertebral height and aggravates degeneration. However, the incidence rate and risk factors of the adjacent intervertebral disk height decrease phenomenon have not been studied. The purpose of this study was to identify the incidence rate and risk factors of the adjacent intervertebral disk height decrease phenomenon after single-level transforaminal lumbar interbody fusion (TLIF) of the lumbar spine. METHODS:A retrospection of 68 patients who underwent L4-5 TLIF. Patient age, sex, and body mass index were collected. Lumbar lordosis, facet sagittalization, Pfirrmann classification, L4-5 distraction height, and L3-4 reduction height were evaluated by radiologic image. The patients were divided into 2 groups based on whether their L3-4 intervertebral height decreased. RESULTS:Forty of 68 patients (58.8%) had L3-4 intervertebral height decrease. The patients' mean age was 62.05 ± 10.90 years in the L3-4 intervertebral height decrease positive (IHDP) group, significantly higher than the 56.14 ± 12.06 years in the L3-4 intervertebral height decrease negative (IHDN) group (P = 0.039). The mean facet sagittalization angle in the IHDP group was 67.5° ± 20.36°, significantly larger than the 55.43° ± 14.97° in the IHDN group (P = 0.010). The preoperative lumbar lordosis was significantly higher in the IHDP group (P = 0.049). No significant effects of other factors on L3-4 height decrease were observed (P > 0.05). CONCLUSIONS:Distraction of the L4-5 intervertebral space by cage insertion leads to a reduced height on the adjacent L3-4 segment in some patients. In addition, the decrease in L3-4 intervertebral height resulting from L4-5 distraction was correlated with age, preoperative lumbar lordosis, and facet joint sagittalization.