The effects of pedicle screw adjustments on the anatomical reduction of thoracolumbar burst fractures

Abstract. The short segmental pedicle screw device is widely used for the decompression of neural elements and reduction of normal anatomy. Many biomechanical studies concerning proper decompression are available. However, no study has determined the optimal device adjustment for reduction of the burst fracture to the normal anatomy. In this study, cadaveric thoracolumbar spine specimens (T11–L3) with L1 burst fractures were studied. A pedicle screw device was attached to the pedicles of the T12 and L2 vertebrae. Spinal postural changes were determined due to a set of eight clinically relevant adjustments of the device. The adjustments were combinations of axial translation (distraction/compression) and extension. The adjustments caused varying changes in spinal posture. The sequence of applying the translation and extension had no effect on the spinal posture changes. The adjustment combining 5 mm distraction with 6° extension brought the burst fracture closest to the intact state, compared to all other adjustments. With this adjustment, on average the spine became 0.9 mm compressed and 2.0° lordotic, compared to the intact. The results of the study show that the device adjustments of axial translation and sagittal angulation can be applied in any sequence, with the same results. The combination of 5 mm distraction with 6° extension was the device adjustment that produced the closest anatomical reduction.

[1]  J F Kraus,et al.  Incidence of traumatic spinal cord lesions. , 1975, Journal of chronic diseases.

[2]  M. Panjabi,et al.  Functional radiographs of acute thoracolumbar burst fractures. A biomechanical study. , 1993, Spine.

[3]  W. Schlickewei,et al.  Ligamentotaxis with an internal spinal fixator for thoracolumbar fractures. , 1994, The Journal of bone and joint surgery. British volume.

[4]  M. Panjabi,et al.  Pedicle Screw Adjustments Affect Stability of Thoracolumbar Burst Fracture , 2001, Spine.

[5]  S. Yerby,et al.  Reinforcement of Thoracolumbar Burst Fractures With Calcium Phosphate Cement: A Biomechanical Study , 1998, Spine.

[6]  M Bernhardt,et al.  Segmental Analysis of the Sagittal Plane Alignment of the Normal Thoracic and Lumbar Spines and Thoracolumbar Junction , 1989, Spine.

[7]  J. Schlegel,et al.  The Role of Distraction in Improving the Space Available in the Lumbar Stenotic Canal and Foramen , 1994, Spine.

[8]  M. Panjabi,et al.  Thoracolumbar burst fracture. A biomechanical investigation of its multidirectional flexibility. , 1994, Spine.

[9]  S D Gertzbein,et al.  Scoliosis Research Society. Multicenter spine fracture study. , 1992, Spine.

[10]  M. Panjabi,et al.  The effects of pedicle screw adjustments on neural spaces in burst fracture surgery. , 2000, Spine.

[11]  M. Aebi,et al.  Stabilization of the Lower Thoracic and Lumbar Spine with the Internal Spinal Skeletal Fixation System: Indications, Techniques, and First Results of Treatment , 1987, Spine.

[12]  M M Panjabi,et al.  The onset and progression of spinal injury: a demonstration of neutral zone sensitivity. , 1992, Journal of biomechanics.

[13]  J W Frymoyer,et al.  An internal fixator for posterior application to short segments of the thoracic, lumbar, or lumbosacral spine. Design and testing. , 1986, Clinical orthopaedics and related research.

[14]  M M Panjabi,et al.  Dynamic canal encroachment during thoracolumbar burst fractures. , 1995, Journal of spinal disorders.

[15]  G R Istre,et al.  Epidemiology of traumatic spinal cord injury and acute hospitalization and rehabilitation charges for spinal cord injuries in Oklahoma, 1988-1990. , 1994, American journal of epidemiology.

[16]  G. Costanzo,et al.  Reciprocal Angulation of Vertebral Bodies in a Sagittal Plane: Approach to References for the Evaluation of Kyphosis and Lordosis , 1982, Spine.

[17]  B E Fredrickson,et al.  Reduction of the Intracanal Fragment in Experimental Burst Fractures , 1988, Spine.

[18]  S. Esses,et al.  Operative Treatment of Spinal Fractures with the AO Internal Fixator , 1991, Spine.

[19]  B. Cunningham,et al.  Experimental Study of Thoracolumbar Burst Fractures: A Radiographic and Biomechanical Analysis of Anterior and Posterior Instrumentation Systems , 1994, Spine.

[20]  R. Jackson,et al.  Radiographic Analysis of Sagittal Plane Alignment and Balance in Standing Volunteers and Patients with Low Back Pain Matched for Age, Sex, and Size: A Prospective Controlled Clinical Study , 1994, Spine.

[21]  M. Panjabi,et al.  Multidirectional Instability of the Thoracic Spine Due to Iatrogenic Pedicle Injuries During Transpedicular Fixation: A Biomechanical Investigation , 1997, Spine.

[22]  D. M. Donovan,et al.  Mechanics of Anatomic Reduction of Thoracolumbar Burst Fractures| Comparison of Distraction Versus Distraction Plus Lordosis, in the Anatomic Reduction of the Thoracolumbar Burst Fracture , 1993, Spine.

[23]  R. Lindsey,et al.  The Fixateur Interne in the Reduction and Stabilization of Thoracolumbar Spine Fractures in Patients with Neurologic Deficit , 1991, Spine.

[24]  P. Anderson,et al.  Biomechanics of Indirect Reduction of Bone Retropulsed Into the Spinal Canal in Vertebral Fracture , 1993, Spine.

[25]  A. Vasavada,et al.  Functional morphology of the spinal canal after endplate, wedge, and burst fractures. , 1997, Journal of spinal disorders.

[26]  F. Magerl,et al.  A new device for internal fixation of thoracolumbar and lumbar spine fractures: the ‘fixateur interne’ , 1985, Paraplegia.

[27]  L. Riley,et al.  The Ideal Amount of Lumbar Foraminal Distraction for Pedicle Screw Instrumentation , 1996, Spine.

[28]  W. Edwards,et al.  1992 Volvo Award in Experimental Studies Vertebral Burst Fractures: An Experimental, Morphologic, and Radiographic Study , 1992, Spine.