Intervertebral disc prosthesis and instruments for locating same
United States Patent 1191 Froning 1 INTERVERTEBRAL DISC PROSTHESIS AND INSTRUMENTS FOR LOCATING SAME [76] Inventor: Edward C. Froning, 215 N San Mateo Dr., San Mateo, Calif. 94401 [22] Filed: Apr. 15, 1974 2 1] Appl. No.: 460,726  
 [52] U.S. Cl. 3/1; 128/92 C; 128/92 E; 128/303 R [51] Int. Cl A6 1/24; Afilb 17/00 [581 Field of Search 3/1. 36; 128/92 C. 92 CA. 128/92 R. 334 R. 92 E. 92 EA, 92 G. 303 R,  
 Primary Examiner-Ronald L. Frinks Atmrney, Agent. or Firm-Julian Caplan [451 Apr. 8, 1975 57 ABSTRACT A collapsible plastic bladder-like prosthesis of the same external form as the nucleus pulposis of an intervertebral disc has a stem through which liquid and/or plastic is introduced to inflate the prosthesis to natural form. The top and bottom have stud-like protrusions which fit into sockets which have been forced through the bony end plates of the bodies of adjacent vertebrae anchoring the prosthesis against slippage. To install the prosthesis, the first step is to insert a transparent tube to the situs with a projecting pin fitting into an adjacent vertebrae to hold the distal end against slippage. A cystoscope may be inserted through the tube to check its location. The degenerated nucleus pulposis of the natural disc is removed in pieces by a forceps inserted through the tube and an incision in the disc wall. The tube provides controlled depth of penetration of this forceps into the disc and acts as a safety feature against injury to blood vessels. nerves and other structures adjacent to the disc. The socket members are inserted through the tube by a specially formed forceps and forced into the adjacent vertebrac. The collapsed prosthesis is then inserted through the stem. the studs pushed into the sockets. Pressure may be adjusted over a period of time; and when finally determined. the stem is severed.  
 13 Claims, 9 Drawing Figures INTERVERTEBRAL DISC PROSTHESIS AND INSTRUMENTS FOR LOCATING SAME This invention relates to a new and improved intervertebral disc prosthesis and instruments for locating the same in place.  
  A principal purpose of the present invention is to provide a prosthesic replacement for a damaged intervertebral disc. The prosthesis resembles in plan view the nucleus pulposis of the natural disc which it replaces. Since no spine fusion is employed bending of the spine in a natural manner is not inhibited.  
  In the lumbar area the entry to the disc is laterally, thereby reducing the complexity and risk of intraspinal surgery traditionally employed. The danger of perforation of the nerve, dural sac, arteries and other organs is reduced. In cervical surgery, the approach is frontally and again the complexity and risk of the surgery is greatly reduced by avoiding transgression of the spinal canal.  
  A further principal purpose of the invention is the provision of means shielding the instruments which are used from the surrounding anatomy and thus damage to such anatomy, such as the cutting of nerves, is eliminated.  
  A still further purpose of the invention is the provision of anchoring means which prevent slippage of the prosthesis after applied.  
  A still further feature of the invention is the fact that the prosthesis is a hollow, flexible bladder-like member which is filled with a fluid and/or plastic under adjustable pressure. The pressure may be increased or decreased while the prosthesis is in place over a period of time to determine by trial and error the optimum pressure, and thereupon the stem of the prosthesis is removed. The optimum pressure is maintained over an indefinite period of time by providing an inflating fluid or plastic having properties for holding fluid or water under pressure normally occurring within the disc sufficient to avoid depletion of the inflating contents, a feature which would duplicate the feature of the normal disc. The inflatable prosthesis and its inflating contents will conform to electrical conductive or insulating properties found in the natural state.  
  Other objects of the present invention will become apparent upon reading the following specification and referring to the accompanying drawings in which similar characters of reference represent corresponding parts in each of the several views.  
 In the drawings:  
  FIG. 1 is a perspective view of the third and fourth lumbar vertebraes from the back and showing a tube and pin inserted.  
  FIG. 2 is a schematic sectional view showing tube and pin in place and also showing use of a forceps to remove the nucleus of the disc.  
  FIG. 3 is similar to FIG. 2 showing insertion of sockets in the upper and lower surfaces of the adjacent vertebrae.  
  FIG. 4 is a view similar to FIG. 2 showing insertion of the collapsed prosthesis.  
  FIG. 5 shows inflation of the prosthesis and the studs thereof fitting into the sockets.  
  FIG. 6 is a view similar to FIG. 1 showing the prosthesis in place.  
  FIG. 7 is an enlarged fragmentary view showing interfitting of stud and socket.  
  FIG. 8 is a schematic vertical sectional view of cervical vertebrae, showing the prosthesis in place.  
  FIG. 9 is an enlarged section view taken substantially along line 9-9 of FIG. 8.  
  A natural vertebral disc 12 comprises an outer annulus fibrosis l3 and an inner nucleus pulposis 14. The disc functions to permit flexible articulation of the adjacent vertebrae 11 and an internal resistance to flexion (or a bending torque) which lends intrinsic stability to this multisegmented column. The nucleus is removed in accordance with the method of the surgical treatment hereinafter described, preferably being removed by the method of chemonucleolysis an injection treatment with an enzyme such as chymopapain, a papaya derivative, which dissolves out the nucleus. It will be understood that the nucleus may be removed in other manners.  
  The body 16 of vertebrae 11 has concave upper and lower surfaces 17 with raised marginal edges 18. A layer of cartilage 19 covers the surfaces 17. Various processes 21 extend from body 16 and these shield the spinal cord 22 and provide attachment for muscles. Nerves 23 extend from cord 22 in the interstices ofthe processes 21.  
  The function of the present invention is to replace the nucleus 14 of a disc 12 with a prosthesis 46.  
  In replacing the lumbar intervertebral disc 12, a tube 31 is inserted laterally to a location abutting the injured disc 12. The tube 31 is inserted in such manner as to move out of the way the adjacent nerves 23. Tube 31 has a longitudinal hole 32 in its wall to receive a pin 33 having an outwardly curved sharpened point 34 which is imbedded in the adjacent vertebrae to secure the anterior of tube 31 in the desired location. To prevent excessive penetration of pin 33, a stop 56 slips over the pin 33 on the exterior of tube 31 and is held in place by set screw 57 so that point 34 projects from tube 31 the desired amount. Optionally, an instrument (not shown) is inserted through the bore into tube 31 to spread the adjacent vertebrae ll apart by tilting same as shown in FIG. 3, whereupon a second pin 33a is installed in a hole 32a diametrically opposite hole 32 and a second pin 330 having point 34a is driven into the vertebrae 11a holding the vertebrae in spread apart condition and affording greater space for the surgical treatment hereinafter described. Preferably, tube 31 is transparent or has a transparent window or is formed with a slot so that a cystoscope (not shown) may be inserted in the bore of tube 31 and the location of the tube relative to disc 12 and also relative to the nerve and adjacent anatomy may be checked.  
  The annulus 13 adjacent tube 31 is penetrated and a forceps 36 having pincers 37 at the anterior thereof is used to remove the remaining nucleus of disc 12. Thus a void 27 is created inside the annulus fibrosis of disc 12 into which the prosthesis 46 is subsequently installed.  
  A second forceps 38 having fitted ends 39 is used to insert socket members 41. Each socket member 41 has a peripheral flange 42 and a hollow pointed prong. Preferably the socket forming members 41 are inserted serially, the flange 42 being captured in one end 39 and inserted through the tube 31 into the void 27 in the disc 12. The prong 43 is imbedded through the cartilage l9 and bony end plate into the surface 17 of the adjacent vertebrae ll. Thereupon a second socket member 41 is installed in the opposite vertebrae in the same manner. Socket members 4] may be of ceramic, plastic, or autogenous bone material and are preferably opaque in radiology.  
  Prosthesis 46 is a hollow, bladder-like member having in expanded shape the appearance of the natural nucleus 14 of a natural disc 12. It has a wall approximately 0.040 inches in thickness and for a typical lumbar disc has a width on its major axis of 1.375 inches and on its minor axis of 0.800 inches. Projecting at an angle of approximately 45 relative to the major axis of the prosthesis is a stem 47 of 0. l 25 inches inside diameter tubing. Preferably a valve 48 is similar to a ball check valve is installed in the stem 47. On the top and bottom surfaces of prosthesis 46 are studs 49 preferably bulbous and integrally formed with the bladder of the prosthesis. The studs 49 are dimensioned to fit into the hollow prongs 43 of the socket members 41. The material of construction of prosthesis 46 preferably has certain characteristics. It has properties of holding fluid or water under pressure substantially duplicating the normal disc. It has electrical conductivity conforming to the normal disc. The fluid or plastic within the disc preferably has similar conductivity and is opaque in ra diology.  
  As viewed in H6. 6, the prosthesis 46 is installed through tube 31 flattened and preferably folded. The flattened condition may be best attained by evacuation of the bladder. After the prosthesis is in place in the void 27, the studs 49 are located in alignment with the hollow prongs 43, a probe being used for this purpose and the location being checked by television fluoroscopic radiography. To facilitate this operation. members 43 and 49 are preferably radio opaque. Thereupon. fluid is pumped through the stem 47 past the check valve 48 to expand the prosthesis to the condition shown in FIG. 5, filling the void 27 and functioning as a healthy nucleus 14 would function in a natural disc 12. The stem 47 may be left in place for some time, preferably terminating near the skin so that from time to time the amount of fluid may be increased or reduced until the desired pressure is determined by trial and error. Subsequently, the stem 47 may be cut off ad jacent the valve 48. Various fluids may be used to expand the prosthesis, but preferably one which offers a radio opague feature to assist in checking position by radiography.  
  Directing attention to FlGS. 8 and 9. use of prosthe ses 46b in cervical vertebrae is shown. The prosthesis is the same in structure and function, but of reduced size from that previously described.  
  However, installation is somewhat simplified. lncision is made frontally to one side of windpipe 53, the adjacent artery 51 and vein 52 being retracted. Thus use of tube 31 may not be advantageous in the neck.  
  The cervical vertebrae and prosthesis are marked with reference numerals as in the preceding modification. followed by subscript b.  
 What is claimed is;  
  l. A prosthesis for the nucleus pulposis of an intervertebral disc comprising a bladder-like member having a stern for insertion of liquid or plastic into said member, said member shaped to simulate said nucleus pulposis of a human disc and to fit within the annulus fibrosis of said disc and at least one stud on an exterior face of said member shaped to engage a socket forming member on one end of said disc formed for installation in the vertebrae along or below said disc.  
  2. A prosthesis according to claim 1 in which said bladder-like member is a thin-walled plastic member capable of being rolled up preliminary to installation formed of a material having approximately the electrical conductivity of a natural disc, and capable of holding fluid or water under pressure substantially duplicating the corresponding characteristics of a natural disc nucleus pulposis.  
  3. A prosthesis according to claim 2 in which said stud is radio opaque.  
  4. A prosthesis according to claim 1 which further comprises a valve in said stem.  
  5. A prosthesis according to claim 1 which further comprises material inserted through said stern substantially filling said bladder-like member, said material being radio opaque, said material being fluid or plastic.  
  6. A prosthesis according to claim 5 in which said material is radio opaque.  
  7. A prosthesis according to claim 1 which further comprises at least one socket forming member having a flange and shaped with a point to imbed said socketforming member into a vertebrae above or below said flange, said socket-forming member formed with a socket complementary to said stud.  
  8. A prosthesis according to claim 7 in which said socket-forming member is radio opaque.  
  9. In combinaton with a prosthesis of claim 1, a tube for surgically locating said prosthesis. said tube being transparent in at least a portion of its distal end for checking location of said tube with a cystoscope inserted into said tube, said tube having locating means operable from its proximal end to drive at least one pin at its distal end into a vertebrae to locate said tube fixed relative to a disc in which said prosthesis is to be installed.  
  10. The combination of claim 9 which further comprises a socket-forming member having a flange, a point and a socket complementary to said stud, and a forceps dimensioned to fit inside said tube and having one end formed to hold said flange for insertion of said point into an adjacent vertebrae by operation of said forceps.  
  11. The combination of claim 9 in which the wall of said tube is formed with a longitudinal hole and said locating means comprises a pin reciprocable in said hole and having a point in its distal end.  
  12. The combination of claim 11 in which the wall of said tube is formed with a second longitudinal hole diametrically opposite said first-mentioned hole and which further comprises a second pin in said second hole to locate said tube fixed relative to said first-mentioned vertebrae and a second vertebrae on the side of said disc opposite said first-mentioned vertebrae.  
  13. The combination of claim 9 which further comprises a stop and means adjustably securing said stop on said pin outside said tube to limit inward projection of said pin into said tube.