114 - In vitro Biomechanical Study to Quantify Range of Motion: Three Level...

#114 In vitro Biomechanical Study to Quantify Range of Motion: Three Level Rigid, Dynamic Stabilization, and Dynamic Stabilization Combined with Rigid Constructs

Basic Sciences-Research

Poster Presented by: J. Lee

Author(s):

J.K. Lee (1)
J. Gomez (1)
C. Michelsen (1)
Y. Kim (1)
M. Moldavsky (2)
S.R. Chinthakunta (2)
S. Khalil (2)

(1) NewYork-Presbyterian Hospital, Columbia University Medical Center, New York, NY, USA
(2) Globus Medical, Audubon, PA, USA

Abstract

Introduction: The use of dynamic stabilization (DS) through minimally invasive techniques has the potential to combine the biomechanical advantages of less stiff instrumentation and minimal muscle trauma compared to open surgical techniques. Range of motion (ROM) was measured for three level rigid, rigid combined with DS, and DS constructs.

Methods: Seven thawed cadaveric specimens were prepared from T12 to S1 and tested in a six degree of freedom machine. A load control protocol of 7.5Nm at a rate of 1.5º/sec was applied in flexion-extension (FE), lateral bending (LB) and axial rotation (AR). TRANSITION® (Globus Medical, Audubon, PA) was used for rigid combined with DS, and DS constructs. REVERE® (Globus Medical) was used for the rigid constructs. ROM was measured from L3-S1.

The following constructs were tested: 1) intact; 2) L3-S1 rigid (3R); 3) L3-L4 dynamic and L4-S1 Rigid (1D-2R); 4) L3-L5 dynamic and L5-S1 Rigid (2D-1R); and 5) L3-S1 dynamic (3D). Data was normalized to the intact (100%) and a one-way repeated measures ANOVA with Tukeys post hoc test was used to determine statistical significance.

Results: In FE, ROM for 3R, 1D-2R, 2D-1R, and 3D significantly decreased ROM to 17±9%, 19±7%, 23±8% and 26±7%, respectively compared to intact, (p≤0.05). ROM for 2D 1R and 3D was significantly (p≤0.05) more than 3R, and ROM for 3D was significantly (p≤0.05) more than 1D 2R.

In LB, ROM for 3R, 1D-2R, 2D-1R, and 3D significantly decreased ROM to 8±3%, 12±3%, 13±2% and 15±3%, respectively compared to intact. ROM for 1D-2R, 2D-1R and 3D was significantly (p≤0.05) more than 3R, and ROM for 3D was significantly (p≤0.05) more than 1D 2R.

In AR, the ROM for 3R, 1D-2R, 2D-1R, and 3D decreased ROM to 39±16%, 53±18%, 74±18% and 85±18%, respectively compared to intact. The 3R, 1D-2R, and 2D-1R constructs significantly reduced mean ROM compared to intact (p≤0.05). ROM increased for DS constructs 1D-2R, 2R-1D, and 3D compared to the rigid construct ROM at 3R. ROM for 2D-1R and 3D was significantly more than 1D-2R ROM (p≤0.05).

Conclusion: All constructs provided stability by reducing motion below the intact state. Increasing the number of dynamic stabilization levels in a three level construct significantly increases motion in all loading modes. Dynamic stabilization is shown to allow for more flexibility than rigid rods and at the same time reducing motion, compared to intact, across three levels.

Figure 1: L3-S1 Normalized ROM