A New Hip Replacement Design Incorporating a Curvilinear Collar

Jay A. Mandell, Dennis R. Carter, Gary S. Beaupré, and David J. Schurman

Objectives: One of the most important innovations in orthopaedics in the last 40 years is total joint replacement. Total hip replacement has been referred to as "the most successful orthopaedic procedure." Hip replacement is considered the treatment of choice for painful, end-stage arthritis and more than 150,000 procedures are performed in the United States each year. Although the 10-year survivorship statistics for hip replacement are quite good, improvements in implant designs remain an important goal if implants are to survive for the lifetime of the typical patient and if joint replacement surgery is to be routinely performed in younger and more active patients with end-stage joint disease.

Methods, Results, and Conclusions:On May 8, 2000 the United States Patent Office issued a Notice of Allowance for a patent application entitled "Prostheses Having Curvilinear Collars." This patent is an outgrowth of a series of VA-supported investigations into the mechanobiology of bone adaptation. The computational modeling that established proof of concept and performance characteristics for this invention was done by Dr. Jay Mandell as part of his Stanford PhD thesis work on "Load Transfer in Cementless Intramedullary Prostheses." Using finite element analysis and bone remodeling simulation software, Dr. Mandell demonstrated that our new prosthesis collar design should reduce prosthesis subsidence and improve the distribution of stress at the prosthesis collar/bone interface. These improvements should result in a reduction in adverse peri-prosthetic bone remodeling, a reduction in the risk of prosthesis loosening, and a reduction in the rate of revision surgery.

The clinical success of a closely related prosthesis design is documented in a publication by Dr. David Schurman (Barber TC, Woolson ST, Goodman SB, Schurman DJ: Flat versus conical collar in cemented total hip arthroplasty: radiographic outcome in osteoarthritic hips. Contemporary Orthopaedics, 32(4):245-248, 1996).

Future Plans: Pending formal issuance of the patent, our plans are to work with Stanford's Office of Technology Licensing to negotiate a licensing agreement with an orthopaedic implant company that will manufacture and market the prosthesis in the United States and worldwide.

Acknowledgement: This work was supported in part by the VA Rehabilitation Research & Development Service.