This invention relates generally to spinal surgery and, in particular, to methods and apparatus associated with the delivery of cement or biological materials to augment the strength of the vertebral body in osteoporotic or otherwise weakened bone conditions, in preparation for pedicle fixation.
Pedicle fixation into osteoporotic spine is tentative fixation at best, often leading to rapid, post operative loosening. Cement injection into the vertebral body (VB) has been utilized for osteoporotic compression fractures (vertebroplasty, kyphoplasty). Injection for augmentation of pedicle fixation is also done, utilizing the tapped pedicle screw hole as an access point.
Currently, however, there is no specific tool or safe system of injection/pressurization. Surgeons often use a cement-filled syringe with a large bore needle, or no needle at all. As such, cement cannot be placed under pressure into vertebral body utilizing a needle or syringe, thus affording minimal VB augmentation. Back flow risks cement flowing into the vertebral neural canal if the pedicle is medially violated. Retrograde flow out of the pedicle entry point may lead to spillage and cleanup problems.
With this background, there remains a need for delivery of cement or biological materials to augment the strength of the vertebral body in osteoporotic or otherwise weakened bone conditions, in preparation for pedicle fixation.
This invention resides in an inserter and associated method for improving the placement of a fastener into a bone. Although ideally suited to the placement of a pedicle screw into a vertebral body (VB), the apparatus and method are applicable to other bones and fasteners, pins, and the like.
In terms of apparatus, a preferred device according to the invention includes a cannulated body having a proximal end, a distal end, and a threaded section therebetween. The proximal end is shaped for rotational tightening by a wrench or other tool, and the distal end including a perforated nozzle. With such an arrangement, the distal end may be inserted into a bone and tightened at the proximal end so that cement and/or biologics may be injected into the bone through the cannulated body.
In the preferred embodiment, the proximal end includes a Lur-loc or other appropriate fitting to receive a cement-filled syringe. The device is also preferably disposable using, for example, clear plastic construction. The inserter may further including a member for sealing the nozzle relative to a bone. Such a member may be composed of a silatstic or other compressible material, or may be inflatable. At least the distal end of the device is preferably provided with varying diameters for different insertion sizes.
A method of fortifying a bone according to the invention to receive a fastener comprises the steps of drilling and tapping a hole in the bone. The inserter apparatus is advanced into the tapped hole, preferably through rotation. The process continues with injecting cement into the hole through the fastener, removing the inserter, and installing the fastener. According to the preferred protocol, the step of injecting cement into the hole through the fastener includes attaching a cement-filled syringe to the injector and depressing the syringe.
According to the invention, varying diameters will be available, each with a threaded waist matching a current commercial tap size, such as 4.5, 5.0, 5.5, and so forth, to engage and seal against the tapped pedicle channel. The tapered end 108 preferably includes a slight taper of smooth plastic, which functions as a guide for centralization, thereby more effectively plugging the pedicle/vertebral body interface. Radiopaque may be provided at the tip, the front of the plug, or elsewhere, to assist with radiological identification.
As shown in
When sufficient cement has been inserted, typically on the order of 2 cc's, the viscosity of excess cement may be checked on field, with the cement introducer 100 being removed when thickening initiates. As shown in
This application claims priority from U.S. Provisional Patent Application Ser. No. 60/500,630, filed Sep. 5, 2003, the entire content of which is incorporated herein by reference.
Number | Date | Country | |
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60500630 | Sep 2003 | US |