The intravertebral plate and cage system via lateral trajectory for lumbar interbody fusion is easy to implant, with few device-related issues however, it carries the risk of vascular surgery in lateral L5−S1 fusion; concern of titanium cage subsidence. These were the findings of a study presented by Jin Fu Lin, Sin-Chuan, Taiwan, at the NASS Annual Meeting in Orlando, USA.
The research aimed to compare the fusion rates between the new device and historical controls of stand-alone cage using the same surgeon, procedure and cage.
Researchers added a lateral intravertebral plane, neutralising residual motions and enhancing fusion. The plane is parallel to the coronal plane, using the vertebrae as the fulcrums, the force vectors of extension, axial rotation and shear are perpendicular to the plate, and resisted.
The Cage (Ti) rectangular has a lateral slot for the plate (no slot in control group) and intravertebral plate, a modified cervical plate (16mm wide). Lateral access to the L5−S1 disc: skin incision anterior to the iliac crest and iliolumbar versus divided and common iliac versus mobilised to expose lateral disc.
Follow up was every three months at first year then six months thereafter. Outcome was measured using Roland-Morris questionnaires, VAS and self-rated satisfaction. Fusion rate in study group was 94.2% and 81.9% in controls with p value <0.01. Mean anterior disc height significantly increased at postop and also loss of restored height at follow-up. Cage subsidence (loss >3mm of restored height) was 40.6%.
Mean hospital stay was 6.7 days (4-12). There were no major complications: neurovascular, deep infection and no vertebral damage by the device: collapse, endplate penetration. Plate lateral migration was > 3mm in 10 levels (14.5%) with cage subsidence; asymptomatic.
Biomechanical studies show stand-alone cage may resist flexion and lateral bending but not extension and axial rotation. Supplemental screw-based fixation raises device-related issues; the ideal rigidity for fusion is unknown.
Improved fusion rate implies the plate increased segmental stiffness. The device is easy to implant, with few device-related issues however, it carries the risk of vascular surgery in lateral L5−S1 fusion; concern of titanium cage subsidence. The results support the lateral plate theory, and the device seems to be a promising alternative in short-segment fusion, the study concluded.