Biomechanical comparison of short-segment posterior fixation including the fractured level and circumferential fixation for unstable burst fractures of the lumbar spine in a calf spine model.
OBJECTIVE There has been a transition from long- to short-segment instrumentation for unstable burst fractures to preserve motion segments. Circumferential fixation allows a stable short-segment construct, but the associated morbidity and complications are high. Posterior short-segment fixation spanning one level above and below the fractured vertebra has led to clinical failures. Augmentation of this method by including the fractured level in the posterior instrumentation has given promising clinical results. The purpose of this study is to compare the biomechanical stability of short-segment posterior fixation including the fractured level (SSPI) to circumferential fixation in thoracolumbar burst fractures. METHODS An unstable burst fracture was created in 10 fresh-frozen bovine thoracolumbar spine specimens, which were grouped into a Group A and a Group B. Group A specimens were instrumented with SSPI and Group B with circumferential fixation. Biomechanical characteristics including range of motion (ROM) and load-displacement curves were recorded for the intact and instrumented specimens using Universal Testing Device and stereophotogrammetry. RESULTS In Group A, ROM in flexion, extension, lateral flexion, and axial rotation was reduced by 46.9%, 52%, 49.3%, and 45.5%, respectively, compared with 58.1%, 46.5%, 66.6%, and 32.6% in Group B. Stiffness of the construct was increased by 77.8%, 59.8%, 67.8%, and 258.9% in flexion, extension, lateral flexion, and axial rotation, respectively, in Group A compared with 80.6%, 56.1%, 82.6%, and 121.2% in Group B; no statistical difference between the two groups was observed. CONCLUSIONS SSPI has comparable stiffness to that of circumferential fixation.
Spinal Disorders Surgery Unit, Department of Orthopaedics, Christian Medical College, Vellore, Tamil Nadu, India; and.
Azad
A
Sait
School of Biosciences and Technology and.
Nadipi Reddy
NR
Prabhav
Spinal Disorders Surgery Unit, Department of Orthopaedics, Christian Medical College, Vellore, Tamil Nadu, India; and.
Vijay
V
Sekharappa
Division of Photonics and Medical Physics, Vellore Institute of Technology, Vellore, Tamil Nadu, India.
Reshma
R
Rajan
Division of Photonics and Medical Physics, Vellore Institute of Technology, Vellore, Tamil Nadu, India.
N Arunai Nambi
NA
Raj
Spinal Disorders Surgery Unit, Department of Orthopaedics, Christian Medical College, Vellore, Tamil Nadu, India; and.
Kenny Samuel
KS
David
D000818:Animals; D001696:Biomechanical Phenomena; D002417:Cattle; D005593:Fracture Fixation, Internal / Q000379:methods*; D021621:Imaging, Three-Dimensional; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D009038:Motion; D016103:Spinal Fractures / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery; D014057:Tomography, X-Ray Computed
BMD = bone mineral density; LDC = load displacement curve; LSC = Load Sharing Classification; NP = neutral point; ROM = range of motion; SSPI = short-segment posterior fixation including the fractured level; biomechanical study; burst fracture; circumferential fixation; lumbar spine; posterior short-segment fixation