Comparison of pressure effects on adjacent disk levels after 2-level lumbar constructs: fusion, hybrid, and total...

With increasing advocacy for the use of TDR procedure as a surgical alternative to fusion in the management of lumbar DDD, intradiskal pressures at the adjacent levels of spine have generated considerable interest. The common belief is that adjacent-level disk pressures will be lower after a TDR as opposed to conventional fusion. The aim of this study is to present the effect of different constructs on adjacent-level disk pressures in lumbar spine. We hypothesized that the adjacent-segment disk pressures after 1- and 2-level TDR and/or a fusion-TDR hybrid procedure will show significant variance within physiological range of motion.

Six adult spine segments T12-S1 with intact ligaments were harvested from cadavers and held firmly in a specially designed fixture. Intradiskal pressures, in motions of flexion, extension, and lateral bending, at L2-L3 and L3-L4 were measured using needle transducers after 2-level TDR L4 through S1, hybrid procedure, and 2-level fusion L4-S1 with femoral ring allograft and pedicle screws.

The pressures with lateral bending were not significantly lower than those with flexion and extension at both levels (P = .18). Although TDR and hybrid specimens recorded slightly lower pressures specifically during lateral bending, no statistical difference in pressures could be detected when movements were combined with various procedures.

Contrary to the assumed hypothesis, the pressures at the adjacent-level disks (L3-4 and L2-3) did not depend upon the stabilization procedure (2-level disk replacement, hybrid, or 2-level fusion) performed after 2-level diskectomy in the lumbosacral spine.