The Role of Cage Placement Angle in Optimizing Short-Term Clinical Outcomes in Lateral Lumbar Interbody Fusion

Objective: The purpose is to investigate the impact of cage angle on clinical outcomes and indirect decompression efficacy in patients undergoing lateral lumbar interbody fusion (LLIF).

Methods: A retrospective review was conducted on 87 patients with single-level lumbar degenerative disease who underwent LLIF. Patients were grouped based on the angle of cage placement: minimal (0°-5°), mild (>5° ≤ 15°), and severe (>15°). Clinical outcomes assessed included pain intensity, functional improvement, and complication rates. Magnetic resonance imaging evaluations included measurements of canal diameter and central canal area pre- and postoperatively. Patient-reported outcomes were also analyzed using the Japanese Orthopedic Association Back Pain Evaluation Questionnaire.

Results: Clinical and radiographic outcomes were significantly improved across all cage angle groups. Reductions in low back pain, leg pain, and numbness were significant in all groups, with no significant differences. Magnetic resonance imaging evaluations revealed significant increases in canal diameter and central canal area postoperatively, confirming effective indirect decompression. Japanese Orthopedic Association Back Pain Evaluation Questionnaire scores showed significant improvements in all domains, including low back pain, lumbar function, walking ability, social life function, and mental health. However, the severe angle group had higher rates of delayed cage subsidence. Complications such as transient motor weakness, thigh pain, numbness, and the need for revision surgery were consistent across groups, with no significant differences.

Conclusions: LLIF effectively treats LDD patients, providing significant short-term clinical and radiographic improvements regardless of cage angle. However, oblique cage placement increases the risk of cage subsidence, requiring careful surgical planning and postoperative following.