Surgical method and apparatus for fusing adjacent bone structures

Claim 2

Surgical method of fusing adjacent vertebral bony structures, said method comprising the steps of (a) spreading apart the adjacent vertebral bony structures, and forming between said vertebral bony structures a lateral bore, which extends into the disc space between adjacent vertebral bony structures, with a female threat that penetrates into cancellous regions of the bony structures, (b) selecting an appropriately sized hollow cylindrical fusion cage which has an external, substantially continuous helical threat which defines a plurality of turns with a valley between adjacent turns and that is perforated in the valley between adjacent turns and that can mate with said female thread, (c) screwing the cage into said threaded bore, and (d) packing the cage with bone-inducing substance.

Claim 3

Method as defined in claim 1 wherein said threaded bore extends into the disc space between adjacent vertebrae, and prior to step (a) is the added step of spreading said vertebrae apart.

Claim 4

Method as defined in claim 1 wherein a second threaded bore is formed to extend into the opposite side of said disc space and parallel to said threaded bore, and steps (b), (c) and (d) are repeated to implant an identical fusion cage in said second threaded bore.

Claim 5

Method for surgically preparing two adjacent bony structures for implanting a hollow cylindrical fusion cage that has an external, substantially continuous helical thread which defines a plurality of turns with a valley between adjacent turns and that is perforated in the valley between adjacent turns of the thread, said method comprising the steps of: (a) drilling a pilot hole laterally between said bony structures, (b) inserting a pilot rod into the pilot hole, (c) fitting a hollow drill over the pilot rod, (d) with the hollow drill, enlarging said pilot hole to form a bore that penetrates into the cortical bone of each of said bony structures, and (e) tapping a female thread into the wall of said bore, the crown of which female thread penetrates into the cancellous portion of each of said bony structures, which female thread can mate with the helical thread of the fusion cage.

Claim 6

Method for surgically preparing two adjacent bony structures for implanting a hollow cylindrical fusion cage that has an external, substantially continuous helical thread which defines a plurality of turns with a valley between adjacent turns and that is perforated in the valley between adjacent turns of the thread, said method comprising the steps of: (a) drilling a pilot hole laterally between said bony structures, (b) inserting a pilot rod into the pilot hole, (c) fitting a hollow drill over the pilot rod, (d) with the hollow drill, enlarging said pilot hole to form a bore that penetrates into the cortical bone of each of said bony structures, and (e) tapping a female thread into the wall of said bore, the crown of which female thread penetrates into the cancellous portion of each of said bony structures, which female thread can mate with the helical thread of the fusion cage.

Claim 7

Method as defined in claim 4 wherein said bore extends laterally into the disc space between adjacent vertebrae.

Claim 8

Method as defined in claim 5 wherein steps (a) through (e) are repeated to form a second threaded bore parallel to the first, one on each side of the disc space.

Claim 9

Method as defined in claim 6 wherein each said female thread is formed in step (e) by hand tapping.

Claim 10

Method as defined in claim 4 and further comprising subsequent to step (e) the steps of: (f) screwing the fusion cage into said threaded bore, and (g) then filling the cage with bone-inducing substance.

Claim 11

Method as defined in claim 8 wherein the bone-inducing substance is cancellous bone chips.

Claim 12

Method for surgically preparing two adjacent vertebrae for implanting a hollow cylindrical fusion cage that has an external, substantially continuous helical thread which defines a plurality of turns with a valley between adjacent turns and that is perforated in the valley between adjacent turns of the thread, said method comprising the steps of: (a) cutting away ligaments to expose the site, (b) spreading the vertebrae apart, (c) nibbling away as much of the lamina as is necessary to access the site, (d) drilling a pilot hole laterally between said vertebrae of sufficiently small diameter to be self-seeking of the center of the disc space, (e) inserting a pilot rod into the pilot hole, (f) sliding over the pilot rod a hollow lamina drill to cut the spinous process and to score the lamina, (g) drilling to remove the lamina within the score then removing the hollow lamina drill and the pilot rod, (h) fitting into the resulting acruate opening in the lamina a C-retractor which has a split cylindrical sleeve of about the same diameter as the lamina drill and a handle extending from one end toward the upper end of the spine, (i) reinserting the pilot rod to rest on the bottom of the pilot hole, (j) sliding a hollow vertebral drill over the pilot rod and inside the sleeve of the C-retractor, (k) forming with the hollow drill a bore that penetrates into at least the cortical bone of each of said vertebrae, (l) removing the hollow drill, the pilot rod, and the cut bone, and (m) using the C-retractor as a guide, tapping a female thread, the crown of which extends into the cancellous bone of each of the vertebrae.

Claim 13

Method for surgically preparing two adjacent vertebrae for implanting a hollow cylindrical fusion cage that has an external, substantially continuous helical thread which defines a plurality of turns with a valley between adjacent turns and that is perforated in the valley between adjacent turns of the thread, said method comprising the steps of: (a) cutting away ligaments to expose the site, (b) spreading the vertebrae apart, (c) nibbling away as much of the lamina as is necessary to access the site, (d) drilling a pilot hole laterally between said vertebrae of sufficiently small diameter to be self-seeking of the center of the disc space, (e) inserting a pilot rod into the pilot hole, (f) sliding over the pilot rod a hollow lamina drill to cut the spinous process and to score the lamina, (g) drilling to remove the lamina within the score then removing the hollow lamina drill and the pilot rod, (h) fitting into the resulting acruate opening in the lamina a C-retractor which has a split cylindrical sleeve of about the same diameter as the lamina drill and a handle extending from one end toward the upper end of the spine, (i) reinserting the pilot rod to rest on the bottom of the pilot hole, (j) sliding a hollow vertebral drill over the pilot rod and inside the sleeve of the C-retractor, (k) forming with the hollow drill a bore that penetrates into at least the cortical bone of each of said vertebrae, (l) removing the hollow drill, the pilot rod, and the cut bone, and (m) using the C-retractor as a guide, tapping a female thread, the crown of which extends into the cancellous bone of each of the vertebrae.

Claim 14

Method as defined in claim 10 and comprising the added step of maneuvering aside the dura and nerve with said split cylindrical sleeve of the C-retractor.

Claim 15

Method as defined in claim 11 wherein the C-retractor is formed with spikes extending axially from one end of said cylindrical sleeve, said method comprising the added step of forcing at least one of said spikes into each of said adjacent vertebrae to anchor the C-retractor.