Abstract
Introduction
This study aims to improve the understanding of the anatomic variations along the thoracic and lumbar spine encountered during an all-posterior vertebrectomy, and reconstruction procedure. This information will help to improve our understanding of human spine anatomy and will allow better planning for a vertebral body replacement via either a transpedicular or costo-transversectomy approach, The major challenge to a total posterior approach vertebrectomy and vertebral body replacement in the thoracolumbar spine lies in the preservation of important neural structures.
Materials and Methods
Retrospective analysis of 100 normal MRI spinal studies (T1-L5) on sagittal T2 weighted MRI images were studied to quantify: 1) mid-sagittal vertebral body (VB) dimensions (anterior, midline and posterior vertebral body height); 2) midline VB and associated intervertebral discs height; 3) mean distance between adjacent spinal nerve roots (DNN) and mean distance between the inferior endplate of the superior vertebrae to its respective spinal nerve root (DNE) and 4) posterior approach expansion ratio (PAER).
Results
1) The mean anterior VB height gradually increased cranio-caudally from T1 to L5. The mean midline and posterior VB height showed a similar pattern up to L2. Mean posterior VB height was larger than the mean anterior VB height from T1 to L2, consistent with anterior wedging, and then measured less than the mean anterior VB height, indicating posterior wedging. 2) Midline VB and intervertebral disc height gradually increased from T1 to L4. 3) DNN and DNE were similar, whereby they gradually increased from T1 to L3. 5) Mean PAER varied between 1.69 (T12) and 2.27 (L5) depending on anatomic level.
Conclusions
The dimensions of the thoracic and lumbar vertebrae and discs vary greatly. Thus, any attempt at carrying out a VB replacement from a posterior approach should take into account the specifications at each spinal level.