1 Introduction topenlarge
A4 injuries are axial compression injuries and involve a fracture of the posterior wall of the vertebral body and both the superior and inferior end plates. Due to axial compression forces, vertical fracture of the lamina is usually present and does not indicate a tension band failure.
In cases where neurological deficit is observed and compression of the spinal canal is assumed, decompression has to be performed. It should be understood that this is a step that can also result in deterioration of neurology unless very meticulously performed.
Decompression can be performed anteriorly or posteriorly. Posteriorly, decompression can be indirect or direct. Indirect decompression may be tried before performing direct decompression. Please refer to Decompression techniques for a detailed discussion of indications for posterior decompression techniques.
2 Closed reduction topenlarge
Primary reduction is performed by positioning of the patient onto a frame to create lordosis.
3 Reduction with pedicle screws topenlarge
Due to the fact that bilateral instrumentation is necessary in all cases, all steps described below are repeated on the opposite side, unless described otherwise.
Pedicle screw insertion
Most A4 fractures are associated with significant comminution of the vertebral body and hence may require PSSF-IS (posterior short segment fixation with intermediate screws) or combined posterior-anterior fixation.
Pedicle screws are inserted into the vertebrae cephalad and caudal to the fracture level on both sides. Mono- or polyaxial, top- or side loading screws can be used in any combination. ( Pedicle Screw Insertion)
The contouring of the rod depends on the site of the fracture following the natural curvature of the spine. A rod contoured in mild kyphosis is chosen for fractures from T1-T10. A straight or a slightly lordotic rod is chosen for fractures from T11-L1 as illustrated, and a rod contoured to lordosis is chosen for lumbar fractures.
The rods are introduced to the distal screw heads on both sides and tightened.
The rod is then inserted into the proximal screw heads without tightening.
If it is decided to perform an indirect decompression, this is done at this stage. If indirect decompression proves to be insufficient, a direct decompression eg, posterior or transpedicular decompression are undertaken. Refer to the Posterior Decompression techniques for detailed instructions. ( Posterior Decompression)
With the help of a distractor, the proximal screws are distracted along the rod. This is done on both sides simultaneously.
The screw heads are tightened with the inner nuts to secure the reduction achieved.
The final construct is shown from a lateral view.
4 Fusion top
Although fusion was routinely performed for all spinal fractures, its indications are now being restricted to fractures that are highly unstable.
Nonfusion fixations can be performed for A3, A4, and B1 type injuries. Fusion is routinely performed for A2, B2, B3 and all C injuries as they are unstable injuries with extensive soft tissue and ligamentous disruption.
For nonfusion surgeries, the facet joint capsule is preserved during the entire procedure.
The screws can be removed after 9 months once the fracture has healed.