Intervertebral fusion removes a considerable region of lumbar ligaments and muscles and increases degenerative diseases in adjacent segments. Therefore, an interspinous fixation device must be developed to overcome these drawbacks. The purpose of the present study is to design a lumbar spine interspinous fixation device that minimizes both tissue removal during interspinous fixation surgery and degenerative changes of adjacent lumbar segments after the surgery. The lumbar interspinous fixation device was designed by employing spike and ratchet structures in the device fixation part to minimize the removal of soft tissue during interspinous fixation surgery and to reduce the stress concentration after the surgery. The part connecting two spinous processes was designed as spring element to allowing normal lumbar behavior after the surgery. Finite element analysis was performed to design spring elements, confirm the structural stability of the fixation device, and compute the intervertebral disc pressure and flexion–extension motions of intact and defect lumbar vertebrae models that were validated in this study. The structural stability of the currently designed interspinous fixation device was confirmed. Under physiological loading conditions, the maximum displacement is 0.4 mm and the maximum stress is 173.5 MPa under the maximum load of 250 N, which accounts for 18.3% of the yield strength of the LIFD material (950 MPa). When the interspinous fixation device was inserted, the intervertebral disc pressure was reduced by 80–92% compared with the defect model that mimics intervertebral fusion. Both a significant reduction in the flexion motion (from 10.7° to 6.0°) up to the normal behavior and a minimal reduction in the extension motion (from − 4.6° to − 3.1°) were achieved, which is consistent with the main role of the LIFD reported in the literature. The interspinous fixation device designed in this work, which is structurally stable and can minimize the tissue removal during interspinous fixation surgery, can reduce the intervertebral disc pressure and maintain the normal lumbar behavior. Therefore, the device can minimize degenerative diseases in adjacent lumbar segments of lumbar vertebrae after the surgery.