498 - Resecting the Anterior Longitudinal Ligament Method during MIS Lateral...

#498 Resecting the Anterior Longitudinal Ligament Method during MIS Lateral Lumbar Interbody Fusion: Radiographic Analysis and Biomechanical Results Using an Integrated Spacer/Plate Interbody Reconstruction Device

General Session: Best Papers Session

Presented by: C. Kim

Author(s):

C. Kim (1)
B. Bucklen (2)
A. Muzumdar (2)
M. Moldavsky (2)
K. Raiszadeh (1)

(1) Spine Institute of San Diego, San Diego, CA, USA
(2) Globus Medical, Inc., Audubon, PA, USA

Abstract

The minimally invasive direct lateral lumbar interbody fusion (LLIF) technique provides a powerful means of correction for adult, degenerative conditions. Nevertheless, sagittal plane correction remains less dramatic. It is hypothesized that the anterior longitudinal ligament (ALL) acts as a tether that prevents lordosis correction.

The purpose of the study is to assess the biomechanical and radiographic consequences of ALL resection during the LLIF procedure, through a cadaveric study plus analysis of seven retrospective clinical cases. A cadaveric biomechanical study (L3-S1) was performed on four pilot specimen (with pre-existing L4-L5 degeneration) to assess construct stability in flexion-extension, lateral bending, and axial rotation using an interbody spacer with integrated plate/screw system (InterContinental, Globus Medical, Audubon, PA). Radiographic analysis was performed. Separately, seven clinical cases were retrospectively reviewed.

Compared to intact control, LLIF anterior device with an intact ALL (Group 1) displayed marked decreases in range of motion (ROM) in all planes (Fig. 1). With ALL resection, and a larger spacer, significant increase in construct motion was observed. Compared to Group 1, resection of the ALL led to motions which were 311%, 558%, and 1034% of Group 1. Additional anterior fixation using the integrated plate with screws, further reduced motion resulting in stability of 281, 353%, and 219% of Group 1. Radiographic analysis of cadaveric specimens showed dramatic improvement in lordosis correction with ALL resection. Compared to intact (7.9 degrees), lordosis correction was 11.5 degrees for Group 1 and 20.2 degrees for the integrated-plate group. Retrospective review of seven patients with ALL resection during the LLIF technique showed an average focal lordosis correction of 16.9 degrees (range 6-31).

Correction of lordosis using the LLIF technique can be improved with ALL resection. However, ALL resection leads to significant construct instability, and potential implant migration/dislodgement. This cadaveric study shows that the addition of an integrated anterior fixation system significantly improves construct stability Long-term studies of the LLIF technique with ALL resection can determine the efficacy of this new minimally invasive reconstructive strategy.

Fig. 1 Biomechanics Results of Lordosis and Motion