Sonic screw
A screw for fixation of, for example, a fracture having a hollow shaft, a first outer thread and radial openings at its distal end, and a second outer thread and an inner engagement portion at its proximal end. The second outer thread is adapted to engage with a tissue protection sleeve. The inner engagement portion is adapted to fit to a driving end of a driving tool. By way of this, forces in axial or radial direction may be applied to the screw by the sleeve, and forces in rotational direction may be applied by the driving tool. Therefore, the screw can be installed accurately at the intended site in an object.
1. A sonic screw system comprising:
a. a monolithic bone screw extending along a central longitudinal axis for implantation into a bone for fixation of a fracture, the monolithic bone screw includes a partially threaded distal shaft portion, a radially outwardly extending collar, an externally threaded proximal shaft portion, and a through bore extending along the central longitudinal axis of the monolithic bone screw through the distal shaft portion, the collar and the proximal shaft portion;
said partially threaded distal shaft portion extends along the central longitudinal axis from a distal tip of the bone screw to said radially outwardly extending collar, and said distal shaft portion having a first externally threaded portion extending along the central longitudinal axis from the tip towards the collar, and a second externally unthreaded portion extending along the central longitudinal axis from the threaded portion to the collar, said first portion has a first maximum diameter and includes a plurality of radial openings connecting the through bore with the external threads;
said radially outwardly extending collar is located on a proximal end of the distal shaft portion and having a second maximum diameter, and the collar has a distal part-spherical surface facing towards the distal tip and a proximal inwardly tapering surface facing towards the proximal shaft portion, the collar forms an annular surface between the distal shaft portion and the proximal shaft portion;
said externally threaded proximal shaft portion extending along the central longitudinal axis from the collar to a proximal end of the bone screw said proximal shaft portion is externally threaded and having a third maximum diameter, said second maximum diameter is greater than the first and third maximum diameters; and the third maximum diameter is greater than the first maximum diameter, and said proximal shaft portion includes an inner tool engagement socket at the proximal end of the bone screw having non-circular torque transmitting surface;
b. a polymer pin made of a thermoplastic fluidizable material which is fluidizable by applying ultrasound energy, said through bore includes a step adjacent the distal tip, said step has a narrower diameter than a diameter of the through bore, such that the polymer pin is seated on the step when being inserted into the through bore of the shaft;
c. a driving tool having a driving tip shaped to engage with the inner tool engagement socket at the proximal end of the screw;
d. a hollow tissue protection sleeve extending longitudinally from a distal end to a proximal end, said distal end of the sleeve includes an inner threaded portion, the inner threaded portion being configured to engage the external thread of the proximal shaft portion, and said proximal end of the sleeve includes a gripping portion diametrically enlarged relative to the distal end of the sleeve, such that, when engaged they form a screw-sleeve assembly with greater length than an entire length of the bone screw, the tissue protection sleeve includes a longitudinal channel extending therethrough being configured to partially accommodate the driving tool, the hollow tissue protection sleeve distal end outer surface located adjacent the annular collar surface when assembled to the screw, the sleeve distal end outer surface tapering inwardly to a diameter not greater than the second maximum diameter, and configured to abut the tapering surface of the collar;
e. an augmentation tool including a sonotrode for fluidizing the polymer pin material of the polymer pin, wherein the augmentation tool is configured to be mounted on the proximal end of the tissue protection sleeve, and the sonotrode configured to extend through the channel of the protection sleeve and in the through bore of the bone screw to and contacts a proximal end of the polymer pin when the pin is seated on the step in the through bore of the bone screw and configured to transmit an ultrasonic vibration to the polymer pin; and
wherein the protection sleeve is configured to connect with the bone screw to facilitate the introduction of the driver and the sonotrode therethrough without interfering with surrounding tissue.
2. The system according to claim 1 , wherein the inner tool engagement socket of the screw is formed to fit with a hexagonal or torx screw driver.