Biomechanics of an integrated interbody device versus ACDF anterior locking plate in a single-level cervical spine fusion construct.
BACKGROUND
No profile, integrated interbody cages are designed to act as implants for cervical spine fusion, which obviates the need for additional internal fixation, combining the functionality of an interbody device and the stabilizing benefits of an anterior cervical plate. Biomechanical data are needed to determine if integrated interbody constructs afford similar stability to anterior plating in single-level cervical spine fusion constructs.


OBJECTIVE
The purpose of this study was to biomechanically quantify the acute stabilizing effect conferred by a single low-profile device design with three integrated screws ("anchored cage"), and compare the range of motion reductions to those conferred by a standard four-hole rigid anterior plate following instrumentation at the C5-C6 level. We hypothesized that the anchored cage would confer comparable postoperative segmental rigidity to the cage and anterior plate construct.


METHODS
Biomechanical laboratory study of human cadaveric spines.


METHODS
Seven human cadaveric cervical spines (C3-C7) were biomechanically evaluated using a nondestructive, nonconstraining, pure-moment loading protocol with loads applied in flexion, extension, lateral bending (right+left), and axial rotation (left+right) for the intact and instrumented conditions. Range of motion (ROM) at the instrumented level was the primary biomechanical outcome. Spines were loaded quasi-statically up to 1.5 N-m in 0.5 N-m increments and ROM at the C5-C6 index level was recorded. Each specimen was tested in the following conditions: 1. Intact 2. Discectomy+anchored cage (STA) 3. Anchored cage (screws removed)+anterior locking plate (ALP) 4. Anchored cage only, without screws or plates (CO) RESULTS: ROM at the C5-C6 level was not statistically different in any motion plane between the STA and ALP treatment conditions (p>.407). STA demonstrated significant reductions in flexion/extension, lateral bending, and axial rotation ROM when compared with the CO condition (p<.022).


CONCLUSIONS
In this in vitro biomechanical study, the anchored cage with three integrated screws afforded biomechanical stability comparable to that of the standard interbody cage+anterior plate cervical spine fusion approach. Due to its low profile design, this anchored cage device may avoid morbidities associated with standard anterior plating, such as dysphagia.
Department of Orthopaedics and Sports Medicine, University of South Florida, 13220 USF Laurel Dr, Tampa, FL 33612, USA.
Matthew I
MI
Stein
Phillip Spiegel Orthopaedic Research Laboratory, Foundation for Orthopaedic Research and Education, 13020 N. Telecom Parkway, Tampa, FL 33637, USA.
Aniruddh N
AN
Nayak
Phillip Spiegel Orthopaedic Research Laboratory, Foundation for Orthopaedic Research and Education, 13020 N. Telecom Parkway, Tampa, FL 33637, USA.
Roger B
RB
Gaskins
Phillip Spiegel Orthopaedic Research Laboratory, Foundation for Orthopaedic Research and Education, 13020 N. Telecom Parkway, Tampa, FL 33637, USA.
Andres F
AF
Cabezas
Phillip Spiegel Orthopaedic Research Laboratory, Foundation for Orthopaedic Research and Education, 13020 N. Telecom Parkway, Tampa, FL 33637, USA. Electronic address: bsantoni@foreonline.org.
Brandon G
BG
Santoni
Center for Spinal Disorders, Florida Orthopaedic Institute, 13020 N. Telecom Parkway, Tampa, FL 33637, USA.
Antonio E
AE
Castellvi
D001696:Biomechanical Phenomena; D001863:Bone Screws; D002574:Cervical Vertebrae / Q000601:surgery*; D005260:Female; D006801:Humans; D016268:Internal Fixators; D008297:Male; D008422:Materials Testing; D008875:Middle Aged; D016059:Range of Motion, Articular; D013123:Spinal Fusion / Q000295:instrumentation* / Q000379:methods
ACDF; Anterior locking plate; Biomechanical evaluation; Cervical spine; No-profile interbody device