1. Field of the Invention
The present invention relates to apparatus used in the cutting and breaking of bones in certain medical procedures.
2. Description of the Related Art
Certain medical procedures require the surgeon to break a bone. Examples of these procedures are bone lengthening operations that require the insertion of a bone lengthening device or other prosthesis. The conventional manner of performing this operation usually requires removing the bone marrow in the center of the bone by drilling through one end of the bone down its longitudinal axis to create a cavity in the bone marrow in which the bone lengthening nail or prosthesis is to be fit.
After this cavity has been drilled, holes are generally drilled perpendicular to the bone at the site where the bone is to be broken. Once the holes are drilled, a chisel is inserted into this region and driven through the bone section and twisted to cause the bone section to break.
The bone lengthening nail is then inserted into the cavity so that the upper portion is lodged in one-half of the broken bone and the lower portion of the nail is lodged in the lower portion of the broken bone. The nail is periodically lengthened in order to lengthen the bone, which heals itself through a knitting process. This bone breaking procedure is an excessively invasive procedure, requiring drilling the holes in the bone and inserting the chisel blade to actually create the fracture.
Moreover, fractures made by this procedure tend to be irregular and fragmented, making the bone more difficult to realign once the bone lengthening device is inserted into the bone marrow cavity.
Thus, there is a need for a bone breaking apparatus that will provide an internally-created cut or stress concentration so that the resulting bone break is regular and easy to realign once a bone lengthening device is inserted into the cavity.
In an alternative procedure, a bone saw is placed within the bone marrow cavity and the bone cut radially from within. However, the cutting depth cannot be controlled so that the depth of the cut can vary according to the thickness of the bone. Therefore, a single cut of uniform depth is made, where the depth of the cut is limited by the thinnest portion of the bone in order to prevent damaging the periosteum and surrounding soft tissue at the thinnest point by cutting deeper. While the thinnest portion of the bone may be cut completely through, there are other areas which are only partially cut. Additionally, this type of saw is incapable of cutting the bone along its length.
Further, such bone saws cannot be used for cutting the femur head due to their large size and limited angular motion. In particular, features such as air inlet and exhaust hoses limit the angle to which the cutter head can be moved.