Biomechanical effects of a novel standalone posterior lumbar facet joint stabilization device: an in vitro cadaveric study.

Objective: Although pedicle screw-rod (PSR) instrumentation remains the gold standard, it has complications, including pedicle breach and facet joint violation. There is current interest in facet joint stabilization with the potential to create a less invasive, natural arch of fixation that may avoid the complications of PSR instrumentation. This study examined the stabilizing potential of a novel facet joint fixation device for single-level (L4-L5) fixation in a human cadaveric model.

Methods: Six L3-S1 specimens were tested multidirectionally under pure moment loading (7.5 Nm) in 3 conditions: 1) intact, 2) L4-L5 facet fixation without screws, and 3) L4-L5 facet fixation with screws. L4-L5 intervertebral disc angles were measured radiographically. Range of motion (ROM) and disc angles were compared using repeated-measures analysis of variance analysis, with statistical significance p<0.05.

Results: Compared to the intact condition, L4-L5 bilateral facet fixation without or with screw fixation significantly reduced L4-L5 angular ROM in all directions (p≤0.003). No significant differences were observed in cranial and caudal adjacent-segment ROM (p≥0.08) except for L3-L4 fixation in extension, which exhibited small motion increases (0.12° without screws, 0.1° with screws) versus the intact condition (p≤0.003). No statistically significant differences were observed in disc angle values between the conditions (p=0.87).

Conclusions: Bilateral lumbar facet fixation with and without supplemental transfacet screw fixation provided significant stability. Cranial and caudal adjacent-level ROM was not influenced by facet fixation except for a slight increase in cranial segment motion during extension. Facet fixation did not alter the lordotic intervertebral disc angle at the instrumented level.