Expandable Spinal Prosthesis

We, Geoffrey Harrison Galley, of Red Lodge, The Close, Totteridge London N20 8PJ, James Bernard Alliborte of 17 The Avenue, Radlett, Herts WD7 7DQ ₃ Mohammed Hamza HSIaE Noordeen of 42 Addϊson Rd, London W14 8JH, Benjamin. Anthony Taylor of Marshcrofi Farm, Marsthcroft Lane, Tring, Herts HP23 5QN and Stewart Kenneth Tucker of West Cottage, 21 Hampstead Lane, London N6 4RT, British subjects, do hereby declare this invention, which is described in and by the following statement.

This invention relates to "the insertion of one or more spacing means in the human vertebral column and is a further improved means of provision and insertion of such spacing means.

In another application by the same inventors (0502872.5), an improved means of achieving the desired separation of adjacent vertebral processes is provided in the form of a tapered segmented screw-like device -which can be deployed using minimally invasive surgical techniques known to those skilled in the surgical art. It is the object of the present invention to provide a further improved means of separating the adjacent vertebral processes which has a minimal cross-sectional profile during insertion so that both the time taken for the surgical procedure, and the trauma caused by the procedure, are further reduced. In addition, the manufacture of the present invention is less complex and

therefore less costly than that of the device described in the above mentioned previous application.

The present invention consists of a plurality of shaped members which are pivotally joined to each other and arranged, around a central screwed rod which is supported by a collar at one end and a threaded collar at the opposite end said collar and collar being located within the pivoting axis of the adjacent members forming each end of the device.

An embodiment of the device is now described with reference to Figures 1a, 1b, 1c, 2, 3a and 3b attached. Figure Ia represents a longitudinal cross sectional schematic view of the device in its pre-insertion or extended condition and Figure Ib represents the same view in the compressed condition following insertion between the adjacent spinous processes of adjacent vertebrae. Figure Ic shows a detail of the junction (23) in the central screwed rod (15) shown in Figures Ia and 1b. Figure 2 represents an orthogonal view of a junction between two adjacent members such as occurs at points B,C,D,E ,G,H,I and J shown on Figure Ib. Figure 3a shows the manner in which, the collar (11) and spring (18) referred to in the description are positioned between the members at the left hand end of the device (point A on Figure 1b) while Figure 3b shows the positioning of the threaded collar (14) and spring (18) within the members at the right hand end of the device (point F on Figure 1b ).

The ten members of the device shown as items 1-10 in Figure Ia are pivotally joined at

locations A to J in Figure Ib providing for an increase or decrease in the angle contained between adjacent members as may be required for the proper functioning of the device. As wulbe apparent from inspection of figures 2, 3a and 3b, the cross sectional dimensions of alternate adjacent members differ so that at each junction between said adjacent members one member may fit inside the other member.. The pivotal means provided at point A in Figure ITJ is shown in more detail in Figure 3 A and consists of a circular collar 11 provided at diametrically opposite sides with short rod like projections 12 which together provide a pivoting axle which passes through a small aperture 13 in either side of each of the two members located around said point A. The pivotal means provided at point F of Figure Ib is shown in more detail; in Figure 3B. Said pivotal means is similar to that provided at point A with the exception that said collar is replaced by a threaded collar 14 through which a centrally located screwed rod shown at 15 on figures Ia and Ib may be advanced or withdrawn. The pivotal means provided at all other junctions between adjacent members is shown in Figure 2 and comprises a cylindrical axle-pin 16 provided with concentric sections of different diameters to facilitate its _. retention within the small holes 17 provided in the respective adjacent members. A wire spring 18 is provided at each pivotal joint between said adjacent members so as to tension said members into an appropriate position during compression and extension of the device of the invention in the manner described herein.

The screwed rod 15 in figures Ia and Ib is provided at its left hand end with an unthreaded portion 19 to facilitate its rotating motion in the collar (11 in Figure 3 a) and a

terminating cap 20 to prevent its complete withdrawal through said collar. Said screwed rod is further provided with a stop nut 21 in figures Ia and 1b which is fixed at a permanent location on screwed, rod 15 by means of a transfixing pin (22 in Figure 1a) or other suitable means.

Said screwed rod is provided at point 23, shown to the right of stop nut 21 in Figure 1b, with a joint (shown in further detail in Figure 1c) which facilitates removal of the section of said screwed rod to the right of said joint. Detachment of one portion of said screwed rod from the other portion may be advantageously provided by means of a threaded portion of reduced diameter on one section of said screwed rod shown in Figure Ic at 23a which enters a matching socket 23b on the other section. Said screwed rod is further provided at the right hand end "with a shaped portion 24 for attachment of a driving tool which may be in the form of a catheter as shown at 25. on figures Ia and Ib.

Ih operation said driving tool is attached to said shaped portion (24) of said screwed rod (15) which is rotated so as to render the device into its expanded or stretched condition as shown in Figure Ia. The device with driving tool attached is now advanced down a previously inserted canula into the body of the patient and positioned between the spinous processes which require separation. The driving tool is then used to rotate said screwed rod in an anti-clockwise direction thereby compressing the device of the invention into the condition shown in Figure 1b. At this point the stop nut 21 engages with the threaded collar 14 to prevent further rotation of said screwed rod and to facilitate the detachment of

the section of said screwed rod to the right of joint 23 by continued rotation of said driving tool. Said driving tool may now be withdrawn from the body of the patient leaving the device of the invention located as desired in its compressed condition and between the spinous processes of the adjacent vertebrae.

The device and the components thereof may be manufactured from any materials which have been shown to be suitable for implantation in the human body. Such materials may if desired be coated or otherwise treated to reduce inflammation and or promote healing of insertion wounds using materials and methods known to those skilled in the art of production of medical prostheses. If the device is manufactured wholly from non-metallic components radio opaque materials may be advantageously incorporated in some or all of the components in order to render the device or parts thereof visible under fluoroscopy during the procedure for implantation in the human body.