The ISOBAR TTL semi-strong dynamic internal fixation system was developed in 1997 by Scient,X. The dynamic bar of the system consists of a controlled micro-movement joint with a superimposed titanium ring with ±2 mm longitudinal displacement and ±2. 3-dimensional mobility, acting as a “shock absorber” in the adjacent area of the fusion. The system is designed to: (1) distribute stresses, protect the implant, and maintain intervertebral height and mobility; (2) prevent further degeneration of the adjacent pathological disc superior to the fused segment; and (3) reduce stress occlusion and accelerate intervertebral fusion. At present, the ISOBAR TTL semi-strong dynamic internal fixation system is mainly used in the following two ways: ( 1) single-segment non-fusion semi-strong dynamic fixation, which is indicated for single-segment instability, including primary small joint instability, discogenic instability and medical instability associated with spinal stenosis. ( 2) Single-segment fusion and strong fixation with semi-strong dynamic fixation of the adjacent segment, which is indicated for two-segment lesions of the lumbar spine, with fusion in the inferior position and only mild degeneration of the adjacent disc nucleus pulposus in the superior position, without clinical symptoms and without removal of the nucleus pulposus. This “fusion fixation + dynamic fixation of the adjacent segment” is also the most commonly used surgical approach in clinical practice. After surgery, the patient retains good lumbar mobility.