Surgical cutting instrument

1. A surgical cutting instrument comprising:

a cannula having a proximal end and distal end defining a length dimension of said cannula and a central bore along the length of said cannula, said cannula further defining a cutting opening having a first cutting edge adjacent said distal end;

a handpiece for supporting said cannula at said proximal end;

a cutting member slidably disposed within said central bore of said cannula, said cutting member having a tubular cutting head portion sized to prevent said tubular cutting head from fully exiting said central bore through said cutting opening, said cutting head portion having a proximal and distal end, said distal end of said cutting head portion defining a second cutting edge, said cutting member also having a body portion between said proximal end of said cutting head portion and said proximal end of said cannula;

a connecting member within said handpiece for connecting said body portion of said cutting member to a source of reciprocating motion to reciprocate said cutting member within said cannula so that said second cutting edge traverses said first cutting edge; and

a sloped member separate from the cutting member that is disposed within said cannula, said sloped member defined by a proximal end and a distal end, whereby said sloped member is configured to angle upwardly from the proximal end to the distal end of the sloped member, said proximal end of the sloped member disposed proximally of the cutting opening such that the sloped member begins extending upwardly from the proximal end thereof at a location that is proximal of the cutting opening and wherein said sloped member is positioned relative to said cutting opening to guide said cutting head portion upwardly toward said cutting opening as said cutting head portion advances toward said distal end of said cannula thereby forming an essentially zero clearance between said first and second cutting edges and wherein said sloped member is an indentation protruding into said central bore of said cannula toward said cutting opening, said sloped member has a length extending along a portion of said cannula, a width perpendicular thereto, and a cross section along the width that is semicircular with an apex positioned opposite the cutting opening and centrally positioned along a width of the cutting opening.

2. The surgical cutting instrument according to claim 1 , wherein, said cutting member includes a hinge portion between said cutting head portion and said body portion to permit pivoting of said cutting head portion relative said body portion.

3. The surgical cutting instrument according to claim 1 , wherein said sloped member is diametrically opposite said cutting opening.

4. The surgical cutting instrument according to claim 1 , wherein:

said cutting opening is further defined by a proximal edge that is positioned opposite said cutting edge and toward said proximal end of said cannula, and

said sloped member is defined by a portion of said cannula that extends proximally from said proximal edge to said cutting edge of said cutting opening.

5. The surgical cutting instrument of claim 1 , wherein:

said central bore and said tubular cutting head define a running clearance dimension therebetween; and

said sloped member has a height extending into said central bore that is substantially equal to said running clearance dimension.

6. The surgical cutting instrument of claim 1 , wherein the sloped member is integral with the outer cannula.

7. The surgical cutting instrument of claim 1 , wherein sloped member uniformly increases to a predetermined height extending from the proximal end of the sloped member to the distal end of the sloped member.

8. The surgical cutting instrument of claim 1 , wherein the apex of the sloped member is positioned closer to a distal end of the cutting opening than a proximal end of the cutting opening.