Method and instruments for percutaneous arthroscopic disc removal, bone biopsy and fixation of the vertebral

Abstract

The insertion points for guide pins used in percutaneous vertebral fixation by pedicle screw are determined by establishing an approach path on a CT image, measuring on the CT image the distance from the intersection of the approach path and the skin of the patient's back to the patient's midline, and marking off the corresponding distance while visualizing the patient by anteroposterior fluoroscopy. An longitudinally expansible pedicle screw comprises a shaft with bone-engaging threads on a distal portion, machine screw threads on a proximal portion, and a tubular extension having wrench-engageable holes on a proximal face, and internal threads engaging the machine screw threads on the proximal portion of the shaft. An oval cannula accommodates an arthroscope and forceps simultaneously for intervertebral disc surgery.

I claim: 
     
       1. A cannula assembly for use in arthroscopic spinal surgery comprising:
 a guide sleeve having a passage therethrough; 
 a first obturator located within the passage of the guide sleeve; 
 a cannula having a wall of uniform thickness, the wall defining a cylindrical inner passage having an oval cross section,; and 
 ana second obturator located within said cylindrical inner passage of said cannula, the obturator having a cylindrical outer wall with an oval cross-section and closely fittingconforming to the cylindrical inner passage of the cannula, the second obturator having an internal passage therethrough configured to receive the guide sleeve; 
 wherein the inner passage of the cannula is sized and configured to allow a plurality of instruments to extend through the passage simultaneously. 
 
     
     
       2. A cannula assembly according to  claim 1 , further comprising a trephine, wherein the obturator has an internal passage of the second obturator is sized for receiving a guide the trephine. 
     
     
       3. A cannula according to  claim 1 , wherein the cannula has proximal and distal end openings and the obturator has a blunt end projecting from the distal end opening of the cannula. 
     
     
       4. A method of spinal surgery comprising the steps of introducing percutaneously through the back of a patient a cannula assembly comprising a cannula having a wall of uniform thickness, the wall defining a cylindrical inner passage having an oval cross section, and an obturator located within said cylindrical inner passage, the obturator having a cylindrical outer wall with an oval cross-section and closely fitting the cylindrical inner passage of the cannula, removing the obturator, and introducing at least two instruments through the cannula whereby said at least two instruments extend through the cannula simultaneously. 
     
     
       5. A method of spinal surgery according to  claim 4 , in which a fenestration is formed in the annulus fibrosis of a vertebral disc of the patient, in which the cannula is inserted into the fenestration, in which said at least two instruments include an arthroscope and a forceps, and in which herniated disc material is removed from the disc by means of the forceps. 
     
     
       6. A method of spinal surgery comprising the steps of:
 inserting an elongated, hollow sleeve percutaneously toward an intervertebral disc of a patient posterolaterally, while the sleeve has an obturator extending through it;   removing the obturator from the sleeve, while leaving the sleeve in place;   passing over the sleeve an assembly comprising a cannula having an lumen with an oval cross-section and an obturator having an oval cross-section conforming to the lumen of the cannula, the obturator with the oval cross-section having a longitudinal passage for receiving the sleeve;   removing the obturator having the oval cross-section from the cannula, while leaving the cannula in place.   
     
     
       7. A method of spinal surgery according to  claim 6 , in which a fenestration is formed in the annulus fibrosis of said disc, and the cannula is inserted into the fenestration. 
     
     
       8. A method of spinal surgery according to  claim 6 , in which a trephine is passed through the cannula toward said intervertebral disc, a fenestration is formed in the annulus fibrosis of said disc by means of the trephine, and the cannula is inserted into the fenestration. 
     
     
       9. A method of spinal surgery according to  claim 6 , in which, prior to the removal of the obturator having the oval cross-section from the cannula, a trephine is passed through the longitudinal passage in the obturator toward said intervertebral disc, and a fenestration is formed in the annulus fibrosis of said disc by means of the trephine, and after the removal of the obturator having the oval cross-section from the cannula, the cannula is inserted into the fenestration. 
     
     
       10. A method of spinal surgery according to  claim 6 , in which, after removal of the obturator having the oval cross-section from the cannula, at least two instruments are introduced through the cannula whereby said at least two instruments extend through the cannula simultaneously. 
     
     
       11. A method of spinal surgery according to  claim 6 , in which, after removal of the obturator having the oval cross-section from the cannula, an arthroscope and a forceps are introduced through the cannula whereby the arthroscope and forceps extend through the cannula simultaneously, and herniated disc material is removed from the disc by means of the forceps. 
     
     
       12. A method of spinal surgery according to  claim 6 , in which a trephine is passed through the cannula toward said intervertebral disc, a fenestration is formed in the annulus fibrosis of said disc by means of the trephine, the cannula is inserted into the fenestration, and an arthroscope and a forceps are introduced through the cannula whereby the arthroscope and forceps extend through the cannula simultaneously, and herniated disc material is removed from the disc by means of the forceps. 
     
     
       13. A method of spinal surgery according to  claim 6 , in which, prior to the removal of the obturator having the oval cross-section from the cannula, a trephine is passed through the longitudinal passage in the obturator toward said intervertebral disc, a fenestration is formed in the annulus fibrosis of said disc by means of the trephine, and after the removal of the obturator having the oval cross-section from the cannula, the cannula is inserted into the fenestration, and an arthroscope and a forceps are introduced through the cannula whereby the arthroscope and forceps extend through the cannula simultaneously, and herniated disc material is removed from the disc by means of the forceps. 
     
     
       14. A method for accessing a spinal location of a patient, comprising:
 advancing a first tissue-displacing member to the spinal location;   advancing a guide member to the spinal location over the first tissue-displacing member;   inserting a second tissue-displacing member over the guide member, the second tissue-displacing member comprising an elongate body with a proximal end and a tapered distal end, the proximal end of the second tissue-displacing member once inserted being positioned outside the patient and the distal end of the second tissue-displacing member once inserted being positioned adjacent the spinal location; the elongate body having a substantially constant acircular outer circumference in lateral cross-section over a portion of the length of the elongate member in the patient; wherein the second tissue-displacing member defines an interior passage that runs the length of the elongate portion, the interior passage exiting the interior of the tissue-displacing member at the tapered end; and   advancing an elongate access device defining an interior passage to the spinal location over the second tissue-displacing member, the elongate access device dimensioned to provide surgical access to the spine.   
     
     
       15. The method of claim 14, wherein the tissue-displacing member has a major axis and a minor axis in lateral cross-section, wherein the major axis is larger than the minor axis. 
     
     
       16. The method of claim 14, wherein the tissue-displacing member has an oval cross-section. 
     
     
       17. The method of claim 14, wherein the guide member is a sleeve. 
     
     
       18. The method of claim 14, wherein the interior passage of the elongate access device is acircular. 
     
     
       19. The method of claim 14, wherein the interior passage of the elongate access device has a major axis and a minor axis in lateral cross-section, wherein the major axis is larger than the minor axis. 
     
     
       20. The method of claim 14, wherein the interior passage of the elongate access device is oval. 
     
     
       21. The method of claim 14, wherein the elongate access device is a cannula. 
     
     
       22. The method of claim 14, further comprising removing the first and second tissue-displacing members from the elongate access device and performing treatment through the access device. 
     
     
       23. The method of claim 22, wherein performing treatment comprises inserting multiple instruments simultaneously through the access device to the spinal location.