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A few weeks ago, I was fortunate enough to get a private lesson in the state of posterior stabilization systems from Dr. Bertagnoli. He’s been developing the next generation system and started implanting them last April. (See news release below.)

The new system is called DSS for Dynamic Soft Stabilization. It’s similar to Dynesys in that it uses pedicle screws with a flexible spacer, but with many improvements. Dynesys spacers are of fixed length. Along with the very wide screw head spacing and the tight cord, this results in a somewhat rigid system with almost no motion in lateral bending. It accomplishes the design goals of allowing some continued motion while providing stabilization, but it does it in a way that does not allow anything close to the normal kinematics of the implanted levels. Because of this, the screw loading remains high and the stiff system can still transmit additional load to the adjacent segments.

The design goals for DSS included allowing more natural kinematics, but only in a neutral or ‘safe’ zone. For most of us, pain is generated when we weight the disc, or when we overload portions of the system by venturing into more extreme ranges of motion. (Bending, lifting, twisting.) If natural kinematics are maintained, but motion is maintained with the neutral zone, the system stays in the ‘safe’ range.

The DSS system is a modular design that includes the ‘soft’ module that provides flexibility not only in flexion and extension, but also in lateral bending. Allowing expansion in flexion and compression in extension, compound movements and lateral bending produces more normal kinematics than does Dynesys. This ‘softer’ system should provide reduced loading on adjacent segments compared to Dynesys and also reduced loading on the screws.

One of the most important features of DSS is the modular design. In addition to the flexible spacers, the DSS system includes rigid spacers for traditional fusion. With this modular system, multi-level procedures can easily mix fusion and soft stabilization. More importantly, if the soft stabilization must ultimately be revised to fusion, a small procedure to remove the flexible spacers and replace them with rigid ones will be all that is necessary. The screws… the other levels can all be left alone… just replace the appropriate segments. The easy revision promised for Dynesys is great in theory… not in practice.

This post is written from memory and a few brief notes. If I discover errors or items that should be explained more fully, I’ll post more. Remember… I’m not a doctor and I'm just sharing what I’ve learned. Take everything I say with a grain of salt.

Mark