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The stability of reconstruction methods after thoracolumbar total spondylectomy. An in vitro investigation
I Oda1, B W Cunningham, K Abumi
1Orthopaedic Biomechanics Laboratory, Union Memorial Hospital, Baltimore, Maryland, USA. ITRODA@aol.com
Study Design:
After total spondylectomy, five types of spinal reconstruction techniques were compared biomechanically.
Objectives:
To evaluate the stability provided by five reconstruction methods after total spondylectomy.
Summary Of Background Data:
Total spondylectomy presents a worst-case scenario for spinal reconstruction. However, few investigators have biomechanically investigated spinal reconstruction stability after total spondylectomy.
Methods:
Eight human cadaveric spines (T11-L5) were used. After intact analysis, a total spondylectomy was performed at L2 and reconstructed using Harms titanium mesh (Depuy-Motech, Warsaw, IN) as an anterior strut. Anterior, posterior, or circumferential instrumentation techniques were then performed using the Kaneda SR and ISOLA pedicle screw systems (AcroMed Corp., Cleveland, OH) as follows: 1) anterior instrumentation at L1-L3 with multisegmental posterior instrumentation at T12-L4 (AMP), 2) anterior instrumentation at L1-L3 with short posterior instrumentation at L1-L3 (ASP), 3) anterior instrumentation at L1-L3 (A), 4) multilevel posterior instrumentation at T12-L4 (MP), and 5) short posterior instrumentation at L1-L3 (SP). Nondestructive biomechanical testing was performed under axial compression, flexion-extension, and lateral bending loading modes.
Results:
Only circumferential instrumentation techniques (AMP, ASP) exhibited higher stiffness than the intact spine in all loading modes (P < 0.05). Short circumferential fixation provided more stability than did multilevel posterior instrumentation (P < 0.05). Multilevel posterior fixation provided more stiffness than did short posterior and anterior instrumentation alone (P < 0.05).
Conclusions:
Only circumferential fixation techniques provide more stability than the intact spine in all testing modes. Short circumferential instrumentation provides more stability than multilevel posterior instrumentation alone and requires fewer levels of spinal fusion.