The Effect of an Expandable Lordotic Interbody Implant to a Fixed Lordotic Interbody Implant in Minimally Invasive Spine Surgery: Its Effect on Sagittal Alignment and Restoration of Disc Height and Foraminal Heights

Presented at SMISS Annual Forum 2018
By Donald Kucharzyk DO
With Dushan Budimir BS,

Disclosures: Donald Kucharzyk DO B; Life Spine, SeaSpine, Orthofix/Stryker, Medicrea, Biomet/Zimmer, Benvenue, Precision Spine, SurGenTec. C; Life Spine, Orthofix/Stryker, Precision Spine, Zyga, Biomet/Zimmer. F; Precision Spine Dushan Budimir BS None,

Introduction:

Minimally Invasive Surgery (MIS) has seen tremendous change with greater emphasis on interbody technologies in the re-establishment of sagittal alignment, disc height restoration and fusion in the absence of a true posterolateral fusion. The goal to minimize muscle damage while still correcting all the pathologies and re-establishing sagittal balance. As technologies have evolved focus has been on the designs of the interbody implants from that of the classic PLIF to an Oblique design as well as Fixed versus Expandable with varying degrees of lordosis but also with the ability to expand the implant in-situ to achieve greater correction and customization.

Aims/Objectives:

With this one must look at the role of a fixed degree and sized implant on sagittal balance, alignment and fusion compared to an expandable implant in terms of these similar parameters. An expandable implant ProLift allows one to insert the implant via a MIS approach and upon deployment achieve up to 15 degrees of lordosis with up to 16mm of height with uniform distraction across the endplate with even distribution of forces to prevent endplate violation and subsidence.

Methods:

Retrospective study was performed to compare an Expandable Oblique Implant (EOI) versus a Fixed Oblique Implant (FOI) performed in a MIS approach. All patients were evaluated for the effect on anterior/posterior disc heights, average disc heights, segmental lordosis, foraminal height, subsidence and fusion. 50 patients in each group were evaluated with followed to one year.

Results:

Anterior disc height: EOI pre 7.6mm post 15.7 change 106.6% FOI pre 10.3mm post 12.1 change 17.5% Posterior disc height EOI 2/9/370% FOI 10.3/12.1/17.5% Average disc height EOI 4.8/13.6/183.3% FOI 7.5/8.9/18.7% Lordotic angle EOI 5.6 degree/15/167.9% FOI 8.4/10.4.23.9% Foraminal height EOI 5.6mm/20.2/89.9% FOI 14.9/16.7/12.1% Subsidence EOI 1 FOI 9 Fusion EOI 95% FOI 73%

Conclusions:

The expandable ProLift outperformed the Fixed implant in all parameters with significant improvements seen due to the ability to uniformly distract across the disc space and customize it for the disc spaces. Allowing for ipsilateral and contralateral foraminal heights re-establishment and maintenance uniformly, avoiding abnormal tilting of the implant as seen with the fixed during its insertion and rotation sometimes being incomplete. This can lead to endplate violation seen more with the fixed and can lead to subsidence and nonunion. The expandable implant also allows one the ability to place larger volume of graft in and around and with the expansion affords post packing more readily than with the fixed implant.