Patent Application
20110009907
The present invention relates to a method for spinal fixation of vertebral structure from a posterior direction through pedicles.
A number of conditions can result in damage or deterioration of one or more intervertebral discs of the human spine. For example, a disc may become damaged by external injury or degenerative disc disease due to advanced age in combination with other factors.
One type of surgery which has benefitted patients with disc problems is fusion of the vertebrae adjacent the disc. In this surgery, the natural disc is replaced with a spacer and the vertebrae are fixed relative to one another.
There are several approaches to insert this spacer: anterior, posterior, posterior lateral, lateral, oblique or axial approaches. The anterior approach can be dangerous because it necessitates surgical involvement of the two major blood vessels, the vena cava and the aorta. Anterior insertion requires spreading the abdominal muscles and the aorta and vena cava in order to gain access to the vertebrae and the disc. Because rupture of either of the vena cava or aorta is life-threatening, such surgery requires the attendance of both a vascular surgeon as well as a spinal surgeon. The posterior, posterior lateral, and lateral approaches involve the risk of nerve impingement that may cause neural damage and even paralysis. The oblique approach requires very precise insertion that involves the risk of pedicle violation, and unlike aspects of the invention described hereinbelow, does not allow 360 degree fixation combined with a pedicle-screw-based posterior fixation system. The axial approach is limited to the S1-L5 pathologies.
In certain situations, it would be desirable to have stiffening, stabilization or spinal fixation systems for the spinal column that include intervertebral plates or spacers as well as pedicle screws fixed in the vertebrae and connected to each other via a connecting rod, such that the distances and arrangement of the vertebrae can be aligned and fixed relative to each other. This would provide a more rigid construct, and reduce moment loads transfer to the vertebrae and the instrumentation.
The present invention seeks to provide a spinal fixation system, described more in detail hereinbelow, wherein a mechanical supportive fastener is used to fix adjacent vertebrae and is introduced from a posterior entry path through the pedicles as for pedicle screws.
The mechanical supportive fastener may be, without limitation, a threaded fastener (e.g., a screw), an expandable fastener, or an injectable fastener. In one embodiment of the invention, the mechanical supportive fastener is used independently of any other fastening device, and is implanted with a dedicated instrumentation/delivery system. In another embodiment of the invention, the mechanical supportive fastener is combined with posterior lateral pedicle screws fixed together with bars or rods (posterior lateral fixation—PLF) to provide a 360 degree fixation system.
Any of the mechanical supportive fasteners of the invention (e.g., screw, expandable and injectable) can be installed as single device through one pedicle in a central portion of the spinal structure, or as a symmetric two-sided system through two pedicles. The system of the invention can be installed through the pedicles of the superior or the inferior levels (e.g., through the L4 pedicles or L5 pedicles in L4-5 fusion).
In another embodiment of the invention, the mechanical fastener is connected at the adjacent level to an anterior fastener, which provides a much more rigid construct in PLF (for example, double locking of the mechanical fastener with the pedicle screws).
There is provided in accordance with a non-limiting embodiment of the present invention a method including affixing an anterior mechanical supportive fastener to anterior portions of adjacent spinal structure by introducing the fastener from a posterior portion of a vertebra and passing the fastener through a curved path to the anterior portions and fastening the fastener to the anterior portions. The fastener may be introduced through a pedicle at the posterior portion of the vertebra.
In accordance with one embodiment of the present invention the fastener is a threaded fastener and fastening the fastener includes turning the fastener to tighten the fastener.
In accordance with another embodiment of the present invention the fastener is an expandable fastener having an expandable portion and fastening the fastener includes turning the fastener to expand the expandable portion outwards.
In accordance with yet another embodiment of the present invention the fastener is an injectable fastener having an expandable portion that is fillable and expandable outwards with a fluid and fastening the fastener includes injecting fluid into the expandable portion to expand the expandable portion outwards.
In accordance with an embodiment of the present invention pedicle screws are affixed in at least one of the adjacent vertebrae, and a connecting rod is secured between heads of the pedicle screws.
In accordance with an embodiment of the present invention the threaded fastener is fastened with a flexible screwdriver. Alternatively, the threaded fastener is fastened with a flexible shaft, which serves as an elastic joint for transferring turning torque to the fastener.
In accordance with an embodiment of the present invention the method further includes connecting the fastener to the pedicle screw.
The present invention will be understood and appreciated more fully from the following detailed description taken in conjunction with the drawings in which:
Reference is now made to
The mechanical supportive fastener is referred to as an anterior mechanical supportive fastener because it fastens natural and/or artificial spinal structure located at anterior portions of the vertebrae, but the fastener is introduced from a posterior location.
In accordance with an embodiment of the present invention, the anterior mechanical supportive fastener is affixed through the same entry point as a pedicle screw 14. This avoids the dangerous anterior access to the vertebrae and the disc, with no risk for nerve root impingement or damage to the vena cava or aorta. In the embodiment of
As seen in
In one embodiment, pedicle screws 14, having polyaxial swivel heads 16 (seen in
In the embodiment of
Fastener 32 may be turned as above with a flexible screwdriver.
Reference is now made to
Reference is now made to
In accordance with other embodiments of the invention, other options are possible. For example, screws may be inserted in a similar approach to improve the fixation of an interbody fixation cage that was previously inserted in any of the optional approaches described above. As another example, screws may be inserted in a similar approach to fix the endplates of an artificial disc prosthesis that was previously inserted in any of the optional approaches. These screws would penetrate only through one vertebra endplate and fixate the adjacent prosthesis endplate.
It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove. Rather the scope of the present invention includes both combinations and subcombinations of the features described hereinabove as well as modifications and variations thereof which would occur to a person of skill in the art upon reading the foregoing description and which are not in the prior art.
