Hip arthroplasty involves removing a diseased hip joint and replacing it with an artificial joint. In one procedure, commonly referred to as a total hip replacement, the head of the femur is removed and a femoral stem having a femoral head prosthesis end is positioned within the end of the bone. The femoral head is received within a prosthetic cup positioned within the acetabulum. While it has been shown that total hip replacement surgery is effective for some patients, a total hip replacement surgical procedure may cause neuromuscular damage. Furthermore, removing the end of the femur may cause bleeding problems, infection, or other complications that are not desirable.
Therefore, an alternative hip replacement surgical procedure was developed in which the head of the femur is resurfaced, as opposed to being removed in a total hip replacement surgery, to receive a femoral head prosthetic.
Since the head of the femur is not removed, the femur resurfacing procedure may be better suited for some patients in which removal of the end of the femur may cause complications or restrict future mobility.
During a hip resurfacing procedure, the head of a femur 10 is reshaped to receive a femoral head prosthetic (not shown). Historically, the procedure utilizes three separate cutting tools to reshape the head of the femur 10 into a desired form as shown in FIG. 4. In a first step, a sleeve cutter 12, an example of which is illustrated in FIG. 1, is used to form a cylindrical shape at the head of the femur 10. After the cylindrical shape has been formed using the sleeve cutter 12, a plan cutter 14, an example of which is illustrated in FIG. 2, is used to create a planar surface at the proximal end of the femur 10. Finally, a chamfer cutter 16, an example of which is illustrated in FIG. 3, is used to impart a chamfered surface on the head of the femur 10. The resultant reshaped femur, shown in FIG. 4, is now ready to receive a femoral head prosthetic that is positioned over the end of the reshaped femur 10.
Use of the three separate cutters 12, 14, 16 during this bone reshaping procedure is not ideal. Each cutting tool requires proper positioning and alignment with respect to the bone 10 to ensure proper fit and function of the femoral head prosthesis. Utilization of three separate cutting tools creates an inherent risk that the tools might not be properly positioned and aligned with respect to the cut created by the prior tool. Therefore, there is a possibility that the head of the femur might not be properly shaped for proper positioning of the femoral head prosthetic. For example, these traditional cutting tools generally require the use of a handle to interface the cutting tool with a drive shaft that imparts rotation to the cutting blade. This interface between the handle and the cutting tool may not be secure. Therefore, because the handle may not be adequately positioned and secured to the cutting tool, the cutting surface of the tool may be askew from its proper position or the cutting surface may shift during use. Therefore, possible misalignment between the handle and the cutting instrument may result in an improperly shaped femur.
In addition, a slight misalignment in positioning the cutting surface of the cutting tool to the bone by the surgeon of any one of the three prior art cutting tools, could also result in an improperly shaped femur, thereby leading to poor positioning of the femoral head prosthesis. In either case, an improperly fit femoral head prosthesis may negatively affect patient mobility and also require that the patient undergo additional surgical procedures to correct the misalignment.
The cutting tool of the present invention addresses these deficiencies by providing a tool that is capable of reshaping the head of the femur in one cutting motion at one time. That is in contrast to using three separate tools of the prior art. According to the present invention, the desired form of the reshaped femur (FIG. 4) is obtained by incorporating different cutting blades into one tool. Therefore, the possibility of incorrectly reshaping the end of the femur as a result of misalignment of the cutting blades to the bone is reduced. As a result, the possibility of an improperly fit femoral head prosthesis is minimized and patient mobility is improved.