Biomechanical Effects of a Novel Standalone Posterior Lumbar Facet Joint Stabilization Device: An In Vitro Cadaveric Study.

OBJECTIVE

Although pedicle screw and rod instrumentation remains the gold standard method of posterior rod fixation, it is associated with 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 associated with pedicle screw and rod 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, with statistical significance set at P < 0.05.

RESULTS

Compared with 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.