Posterior Lumbar Interbody Fusion versus Dynamic Hybrid Instrumentation: A Prospective Randomized Clinical Trial

The purpose of this study was to assess the radiologic and clinical outcomes after lumbar fusion intervention and to compare the established posterior lumbar interbody fusion (PLIF) technique and dynamic hybrid instrumentation (topping off).

In this prospective randomized trial, all patients who presented with degenerative changes to the lumbar spine (L2-S1) were included and randomized in 2 groups: patients who underwent the 360°-fusion procedure in PLIF (group 1: control group) and those patients who underwent fusion surgery with additional hybrid instrumentation (Dynesys-Transition-Optima [Zimmer Spine Inc., Denver, Colorado, USA]) cranial to the rigid fixed segment (group 2: intervention group). Patients' demographics were documented and follow-up visits were conducted after 6 weeks and then stepwise after 6 up to 36 months. Each follow-up visit included assessment of quality of life and pain using specific questionnaires (Core Outcome Measurements Index, Short-Form 36, and Oswestry Disability Index) as well as radiologic evaluation with the focus on the adjacent level alteration.

Fifteen patients per group met the inclusion criteria, and after 36 months, the loss to follow-up was 20%. At the maximum follow-up time, the overall risk for adjacent segment degeneration was substantial (i.e., 24.14%), independent of the surgical procedure. Material failure was observed in 17.24%. Although no significant difference was observed between both groups, all patients presented with postoperative improvement regarding the clinical scores.

The present study cannot support the safety of dynamic hybrid devices in those cases if the reduction of adjacent segment degeneration is the main target, especially regarding the reported implant failure rates and the similar clinical outcomes between the both groups.