A modular cage may prevent endplate damage and improve spinal deformity correction.

Area of Science:

• Spinal Surgery
• Biomechanics
• Orthopedic Implants

Background:

• Anterior lumbar interbody fusion (ALIF) commonly uses monobloc cages inserted with impact.
• Three-part modular cages are a newer alternative designed to reduce impact forces and endplate damage.
• Modular cages aim to improve lordosis correction during ALIF procedures.

Purpose of the Study:

• To compare the endplate damage and lordosis angle achieved by monobloc versus modular stand-alone cages in ALIF.
• To evaluate the impact of cage type on bone fragmentation and sagittal balance restoration.
• To assess the efficacy of AI-based lordosis angle measurements in evaluating surgical outcomes.

Main Methods:

• Human lumbar motion segments (L2-L3, L4-L5) were used for in vitro implantation simulation (n=12).
• Procedures included discectomy followed by implantation of either monobloc or modular cages.
• Macroscopic imaging, microcomputed tomography (micro-CT), and AI-based lordosis measurements were performed to assess endplate damage and angle correction.

Main Results:

• Both cage types caused mid-level damage (29%), but modular cages resulted in more low-damage instances (13% vs. 17% for monobloc).
• Bone fragmentation was significantly higher in the monobloc group (71%) compared to the modular group.
• Modular cages achieved a greater median lordosis of 21.3° versus 19.5° for monobloc cages, a 34% increase.

Conclusions:

• Endplate damage is present with both monobloc and modular ALIF cages, but modular designs reduce severe bone fragmentation.
• Bone fragmentation negatively impacts the achievable lordosis angle, potentially hindering sagittal balance restoration.
• Newer implantation techniques and modular cage designs are crucial for optimizing lordosis and patient outcomes in ALIF.