Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
2000-01-28
2001-07-10
Hirsch, Paul J. (Department: 3732)
Surgery
Instruments
Orthopedic instrumentation
C606S085000
Reexamination Certificate
active
06258093
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to the reamer cutting head for the surgical reamers used by surgeons during intramedullary reaming and other orthopedic procedures requiring the internal enlargement of bone central canals.
2. Brief Description of the Prior Art
Surgeons have for years used reamers during orthopedic surgery to enlarge intramedullary canals of long bones such as the femur, tibia and humerus. The purpose of this is for sizing or enlarging the canal for the acceptance for an intramedullary fixation device or total joint implant. This fixation device is usually a rod or tube inserted into the correctly sized canal and held in place with screws.
Intramedullary reaming is generally performed with a rotary cutting tool attached to a flexible shaft. Reamer cutting tools are mounted permanently to a flexible shaft or are interchangeable by means of an interlocking dove tail slot.
Prior to the reaming process a wire rod is inserted into the central canal as a guide for the reamer. The reamer and shaft each have an axial bore concentric with the axis of rotation. The reamer is passed over the rod and feed into the canal for enlarging. The canal is enlarged incrementally with a series of reamers, which increase in diameter by 0.5 mm. A separate interchangeable cutter head or complete cutter head/shaft assembly is required for each step. This requires that the reamer be extracted from the canal and slid off the guide wire. The next incremental cutter head or complete cutter head/shaft assembly is then passed over the wire and advanced into the canal. For an intramedullary nail this would entail approximately 9 or 10 interchanges.
The prior art cutting heads have been cylindrical, elliptical, ball or bullet shaped with a plurality of fluted spaced around the axis of rotation. Each flute has a cutting edge formed when a “V” groove is machined along its axis from the front tip to the rear end of the cutter. Generally, straight or helical “V” grooves are machined into the cutter in order to create a rake angle at the leading edge.
This “V” groove also serves as an area for chips and tissue after being cut from the internal surface of the bone canal. Such a cutter head is shown generally in U.S. Pat. No. 4,706,659 (Matthews et. al.) and U.S. Pat. No 4,751,922 (DiPietrolo) as a cutting head on a shaft but does not refer to the design of the cutting head. Borzone et. al. (U.S. Pat. No. 5,122,134) describe a cutting head having a series of circumferentially spaced flutes having a first section extending in a straight line from the leading edge of the cutter, a curved central portion formed as a section of a torus, and a second straight section back to the trailing edge of the cutting head.
The form of the “V” groove machined into the cutter creates the rake angle and cutting edge of the first flute and the trailing edge of the next adjacent flute. By varying this “V” angle and depth with respect to the number of flutes required, a constant circumferential width along the cutting surface is formed. This constant circumferential width generally starts at the front tip and extends to the rear end of the cutter. Each of the flutes has a cutting edge and when rotated, forms the cutting surface of the reamer. This cutting surface has a ground relief angle to enable it to cut freely.
The prior art reamer heads have been concerned with cutter binding in the bone canal and cutter retraction after binding. The general configuration of prior art reamer heads have not addressed the problems of heat generation, cutter force, intramedullary pressure and the quantity of cutter heads required to enlarge the intramedullary canal.
SUMMARY OF THE INVENTION
The invention provides a cutter head which reduces the cutting force. The cutter head increases the depth of cut or cutting length which can be obtained with the reamer head, thus reducing the number of reamers needed during the procedure, reducing hospital inventory cost, and reducing operative time of the procedure.
The invention provides a cutter head which counter acts the tendency of a high helix angle cutter to dig in or cut into the bone without clearing away the produced chips or debris.
The invention provides a cutter bead which reduces the intramedullary pressure ahead of the cutting head and reduce the risk of the patient developing vascular complications resulting from fat embolism.
The invention provides a cutter head that reduces the tendency of cutters to fail to clear chips and debris and to bind up inside the bone canal.
A cutting head for surgical reamers for use in enlarging the bore of the central medullary canal of a bone having a leading tip and a trailing end, connectable to a drive shaft, forming a length. The body has a circumference and at least a pair of flutes, formed by grooves, extending in at least one pattern, a predetermined distance along the length. Each of the flutes has at least one tooth with each tooth having a crest and a base adjacent the flute. The pattern of the grooves can follow a first helical path along its length. The helical path can be substantially constant over a major portion of its entire length, in relation to the axes or can have a constantly changing path. A second pattern can follow a second, contiguous helical path that has a second radial orientation to the axis.
The teeth can be formed from a sinusoidal wave form comprised of a continuous radius going from convex to concave, with each of the teeth having a predetermined pitch from the crest to the base. In another embodiment the crest the teeth on the first flute is offset axially by a predetermined distance from the teeth on the adjacent flutes. The offset can be determined by dividing the pitch on each flute by the number of flutes.
The cutting head can, in an alternate embodiment, have a notch within each of the flutes. The notch forms a pair of teeth, the crests of each of the teeth can have either a substantially equal radius or a different radius, depending upon the placement of the notch.
REFERENCES:
patent: 569285 (1896-10-01), Jacobs
patent: 4625725 (1986-12-01), Davison et al.
patent: 4706659 (1987-11-01), Mathews et al.
patent: 4751922 (1988-06-01), DiPietropolo
patent: 5122134 (1992-06-01), Borzone
patent: 5342365 (1994-08-01), Waldman
patent: 5376092 (1994-12-01), Hein et al.
patent: 5755719 (1998-05-01), Frieze et al.
patent: 5759185 (1998-06-01), Grinberg
patent: 1553078 (1990-03-01), None
patent: WO 90/07908 (1990-07-01), None
Edwards Garland U.
Krause William R.
Hirsch Paul J.
Parke Sheldon H.
LandOfFree
Surgical reamer cutter does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Surgical reamer cutter, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Surgical reamer cutter will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2491221