Vertebral pedicle anatomy in relation to pedicle screw fixation: a cadaverstudy

New techniques to stabilize and correct the thoracic and lumbar spine have been developed in recent years. In view of the wide variety and complexity of fixation devices, the optimum configuration of spinal instrumentation sy stems needs to be defined. Linear and angular measurements of both vertebra l pedicles were made in ten complete: thoracic and lumbar cadaveric spines using callipers and a goniometer. The Vertical interpedicular distance grad ually increased along the spine up to L5. The transverse interpedicular dis tance was larger at both ends of the spine. Pedicular height gradually incr eased from T1 to L5, plateauing between T3 and T9, being widest at the thor acolumbar junction. Pedicular width was greatest at the three junctional re gions of the spine. The sagittal pedicular angle decreased along the length of the spine to zero at L5. The transverse pedicular angle decreased from T1 to T12 and then increased to L5. Of the pedicular measurements only widt h limits the diameter of fixation screws. The vertical interpedicular dista nce determines the distance between the holes of plates, while the length o f the transfixator is related to the transverse interpedicular distance. Th e pedicular angles enable triangulation of screws and determine the stabili ty of the fixation.