Synapse 4.0
Fig 1: The 4.0 mm titanium alloy rod is 50% stronger and 70% stiffer than existing 3.5 mm titanium alloy rods Posterior cervical fusion (PCF) surgery is often needed when patients require treatment of some typical spinal conditions, including degenerative disc disease, spondylosis, spinal stenosis, fracture, and tumor. Additionally, it can be an essential surgical option for revisions of seudarthrosis or failed previous surgery.
The goals of posterior cervical spine fusion surgery are to:
- Treat nerve and/or spinal cord impingement through decompression
- Achieve stabilization of spinal segments after fracture or trauma
- Correct deformity and maintain alignment
The implants and instruments available for surgery have continued to improve over time. Early techniques for posterior stabilization included use of wire or cable around affected bony structures, such as the lamina and/or spinous process. Posterior plate and screw constructs offered some additional stability and reduced potential complications, such as loosening of wiring, although screw placement and plate alignment remained difficult in many patients. The further development of multiangle screw and rod constructs offered surgeons the advantages of stable fixation and added flexibility for optimal placement.
Comprehensive instrumentation for occipital cervical thoracic surgery
The synapse system is an enhanced set of instruments and implants, including clamps, variable-axis screws, hooks, transconnectors, transverse bars and rods, designed for posterior stabilization of the upper spine. The implants provide the flexibility required to accommodate variations in patient anatomy.
Key to achieving this flexibility is the polyaxial screw implant. With angulation in all directions, the implant accommodates the most demanding surgical constructs, without the need for favored-angled or biased screws. The locking cap utilizes a square-thread design to eliminate cross-threading during final tightening.
Synapse is available in two rod diameter sizes of 3.5 and 4.0 mm, and the new synapse 4.0 system allows for interchangeable use between both 3.5 and 4.0 mm diameter rods. This allows the surgeon to decide intraoperatively on the rod stiffness and strength, depending on the anatomy of the patient and the indication.
The 4.0 mm titanium alloy rod [Ti 6Al 7Nb] is 50% stronger and 70% stiffer than the existing 3.5 mm titanium alloy rods. It is ideal for surgical indications, such as:
- Crossing the occipitocervical [OC] and/or cervicothoracic [CT] junctions
- Severe trauma cases resulting in gross spinal instability
- Tumor situations where significant bone resection has destabilized the spine segments
The system includes a top-loading transconnector which attaches to the polyaxial screws to provide additional construct torsional rigidity when required.
One of the best instrumentation features of the system is the simple and efficient threaded screwdriver which eliminates screw toggle during insertion and mechanically disengages the screw to eliminate sticking of the driver in the screw recess.
The synapse system is fully compatible with the OC fusion systems to provide comprehensive instrumentation throughout the occipital cervical thoracic [OCT] region.
Fig 2: Polyaxial screws have 100° of angulation in all directions 
Fig 3: The top-loading transconnector adds torsional rigidity to the construct
(Case provided by Rick Bransford, Seattle, USA)
A 28-year-old, 109 kg man was involved in a high-speed motor vehicle collision with C7-T1 jumped facet and T1 teardrop fracture. The patient had ASIA E with motor score of 100. He had failed closed reduction in the emergency room then was taken to OR emergently for open reduction and C5-T2 posterior segmental instrumentation with synapse 4.0. The patient did well postoperatively with no evidence of collapse or failure.
Synapse 4.0 was the ideal solution to treat this injury. This was a heavy patient with a highly unstable injury at the cervicothoracic junction. Synapse 4.0 enabled stabilization of his injury with a rigid construct. It has all the benefits of the 3.5 system but is more rigid and allowed use of one system as opposed to using the 3.5 system and a 6.0 rod system with the nuances of a tapered rod. The author was able to place C5 and C6 lateral mass screws utilizing the Magerl technique and C7, T1, and T2 pedicle screws.
Fig 1ab: Preoperative images 
Fig 2ab: Intraoperative images 
Fig 3ab: Postoperative CT scans 
Fig 4: Postoperative x-ray. In the US screws are only indicated from T1-T3 Hazards and labeling
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