Apparatus for manufacturing a bone dowel

Metal working – Plural diverse manufacturing apparatus including means for... – Type of machine

Reexamination Certificate

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Details

C029S02700R, C029S560000, C082S110000, C082S152000, C408S023000, C409S066000, C409S165000

Reexamination Certificate

active

06557226

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is related to the field of bone dowels, and more specifically devices and method designed to be used (e.g., in a sterile setting) to manufacture a bone dowel for use in spinal surgery.
2. Description of the Related Art
Clinical spinal fusion procedures using bone graft have been used for decades. Anterior cervical interbody fusion using cylindrical smooth bone grafts as spacers was reported by several authors by the mid-1950's. In 1985, threaded cylindrical bone dowels were reported by Vich, eliminating the need to hammer the dowels in place. In the use of these dowels, a cylindrical bed was drilled in the appropriate intervertebral bodies and the graft was then screwed into the opening. Bone grafts could be attained from iliac crests as described by Cloward or using a Kiel-surgibone heterologous graft. Threaded dowels were prepared with a sterilized die or with a small lathe.
U.S. Pat. No. 5,814,084 describes cortical bone dowels derived from cortices of bone diaphyses that may have a chamfered insertion end. The dowels described in the '084 patent may also include a canal derived from the intramedullary space of a diaphysial bone that retains the natural architecture of that region of the bone, and which can be packed with cancellous bone. The background section of the '084 patent provides a discussion of the development of the art. The '084 patent is incorporated herein by reference.
SUMMARY OF THE INVENTION
A device for manufacturing a bone dowel may include a machine base with one or more tracks in a surface thereof. In some embodiments, at least one track may be perpendicular to at least one other track. In this configuration, the machine base may include at least one perpendicular intersection of two or more tracks. The device may also include a rotary cutting tool module, configured to hold a rotary cutting tool and to slide in a track in the machine base. The device may also include one or more modules for holding a dowel, preferably configured such that the modules are configured to slide in the tracks in both parallel and perpendicular orientation to a rotary cutting tool module disposed in a track during use, thus enabling an operator to perform various cutting, drilling and milling operations on a dowel.
As is described herein, one or more modules may slide in the tracks in perpendicular or parallel orientation to a cutting tool during use. Although embodiments are described in which a machine base includes two tracks in perpendicular orientation, a machine base may also include two, three, or more tracks perpendicular to one or more tracks that may be configured to hold a cutting tool module, for example. In this way, more than one dowel module may be disposed on the machine base simultaneously or even sequentially in different tracks as needed to contact one or more cutting tools.
In one embodiment, a device for manufacturing a bone dowel in which a rotary cutting tool may be held in an appropriate position, and a module holding a dowel may be moved relative to the cutting tool in order to contact the rotary tool and shape the dowel to the desired size and configuration is described. In other embodiments, both the cutting tool and the dowel are held in modules that slide in tracks for controlled positioning and machining of the dowel. Other embodiments may include only one track, and a module holding a bone dowel may contain a sliding member configured to allow the dowel to be moved perpendicular to the cutting tool held in a module mounted in the track.
The devices disclosed herein offer certain advantages over more conventional dowel manufacturing devices, such as lathes, in which a motor is connected to a shaft or other device configured to turn the dowel, and an operator then contacts the dowel with a knife, a gouge, or other stationary tool. Dowels made on such a device are typically machined to size in a clean room and then a number of different sizes are packaged and frozen. A surgeon typically thaws a number of different sizes of dowels so that one can be chosen during surgery to best fit the need of the patient. Unfortunately, the dowels that are not used cannot be re-frozen and must be discarded. The devices disclosed herein, in contrast, can be used in the operating room during surgery. The use of high speed rotary cutting tools is, in fact, routine in certain surgical procedures in operating rooms and the present device is adaptable to those rotary cutting tools. The present devices, then, may be sterilized and used in surgery to produce a dowel of the needed size from a dowel blank, after the surgeon has determined the needed size. This reduces waste of human tissue and unnecessary expense, since only the single dowel blank need be thawed, rather than a selection of pre-sized dowels.
The terms dowel, bone dowel, dowel blank, and bone portion are interchangeably used to describe a portion of bone that has been cut from donor bone and is ready for, or in the process of, being manufactured using the devices described herein. The terms dowel and bone dowel may be used to describe the finished product of the manufacturing process.
In certain embodiments, the modules for holding a dowel include a collet module, including a base configured to slide in a track and a collet configured to hold a dowel such that an end of the dowel may contact the cutting tool during use. A collet may be configured to hold a dowel by one end such that the opposite end may contact the cutting tool. As used herein, a dowel may typically be cylindrically shaped, such that the dowel is defined by two ends separated by the height of the dowel. The height may also be described as the long axis of the dowel, and the circumference of the long axis as the circumferential portion of the dowel. A collet module may be configured to hold a dowel parallel to the base of the module, or perpendicular to the base. As described herein, parallel means that the long axis of the dowel is parallel with the track in which the base is held during use. In some embodiments, a collet module may be useful to machine an end of a dowel smooth by moving a dowel in a track perpendicular to the rotary cutting tool until an end contacts the cutting tool burr. The dowel may then be manually rotated to achieve a smooth end. The collet module may also be useful for drilling a center hole in an end of a dowel by moving the dowel held in the collet module in parallel orientation to a drill bit mounted on a rotary cutting tool held in a rotary tool module. Alternately, a center hole may be drilled in an end of a dowel held in the collet module by moving a rotary tool module holding the drill bit or burr mounted on a rotary cutting tool in parallel orientation to the collet module.
The modules for holding a dowel may also include a vise module including a base configured to slide in a track and a vise configured to hold a dowel along the length thereof such that an end of the dowel may contact a cutting tool during use. In some embodiments, a vise module may include a base configured to be mounted in a track and a vise configured to hold a dowel mounted on a sliding member configured to slide on the base perpendicular to the track. A vise module may include an opposed pair of jaw members configured to move together to press against an object held between the jaw members. In some embodiments, vise modules may include a groove or indention in one or both jaw members configured to conform to the circumferential portion, or the sides of the long axis of a dowel. The module may preferably be configured to hold a dowel perpendicular to the base such that an end of the dowel is free to be machined during use. The vise module may also be configured to hold a dowel securely against a force resulting from a cutting tool traveling across the face of an end and from a force resulting from a drilling tool boring into the face of an end. The vise module may be useful in cutting a groove or slot into an end of a dowel. Such a groove or

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