The insertion of pedicle screws into the spine for fixation has been commonly used for many years. In general, a set of implants is placed on both sides of the spinous process into the pedicles and the set on each side is connected by an individual rod. For example, in a single level fusion, whereby two vertebral bodies are intended to be fused together, four pedicle screws are used, two on each side of the spinous process. Each set of two is then connected by the rod. For multiple levels, more screws are used and connected by longer rods. The general technique is an open procedure, whereby the incision in the skin is long and spans the length of the affected area of the spine to be treated. As alternative to rod based systems, plating systems, where a plate forms the connector between two or more screws, has been used in the spine for a long time. Plating systems, such as those shown in U.S. Pat. No. 4,611,581 to Steffee and U.S. Pat. No. 4,887,595 to Heinig et al., use rigid plates to connect the screws placed within the pedicles. Rod-based systems are significantly more popular for fixation in the posterior lumbar spine due to the complexity of the anatomy.
The lumbar spine includes multiple vertebrae that, in a healthy spine, are flexibly held within a general S-curve. Each vertebra is a different size and different geometry. The pedicles on each vertebra, which are posts that extend from the vertebral body, vary in angle and distance apart from one vertebral body to the next. While a rod can be contoured or bent to meet the anatomy, this is extremely difficult, if not impossible to do well with a rigid plating system, as plates can be contoured to match the S curve, but resist contouring in other directions.
To avoid contouring, systems such as that covered under U.S. Pat. No. 6,379,354 by Rogozinski, break long plates into smaller plates that connect one pair of screws at a time. The system is difficult to use and requires significant implant inventory, as each link covers only one distance between two screws and has no adjustability. There are also other drawbacks such as overall system height and profile
Therefore, while these prior plating systems and surgical procedures can be suitable for limited usage to which they somewhat address, they are not suitable to providing an implant and surgical approach that can accurately and securely connect multiple screws together, adjust for anatomical variations, provide a low profile system, and significantly reduce the quantity of implant and instruments needed while reducing surgical complexity.
Thus, a need exists to overcome the problems with the prior art systems, designs, and processes as discussed above.