Abstract
A femoral stem using a double threaded cone locking mechanism has been developed down under. Over 400 prostheses have been implanted as primary, revision and replacement prostheses over the last 4 years. Stem insertion is achieved by a gentle screw home mechanism and does not use the “hammer and nail” insertion principle.
Design
The prosthesis has two components:
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A cone shaped stem
The stem body externally is a slowly tapering hydroxyapatite coated cone, with a distal pilot and two differing speed external threads. The parallel threads strongly resist derotation of the prosthesis in the bone and impart rotatory stability. The cone shape imparts excellent vertical stability.
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A modular neck
The neck component is available in various horizontal offsets and vertical height options and allows the femoral ball to accurately find the “sweet spot”, the center of the acetabulum
Full four-vector adjustability is available at the end of stem preparation:
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Vertical height (leg length)
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Horizontal offset
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Anteversion neck angle
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Neck/ball length
Design Advantages
The locking mechanism gains immediate and longterm vertical and torsional stability in the femur.
Immediate full weight bearing is possible, especially in primary total hip replacements.
The locking mechanism grips equally well in the metaphysis and proximal or distal diaphysis of the femur.
Bulk structural allograft may not be necessary even in the severely deficient proximal femur.
The prosthesis can be used in wide medullary canals.
The early clinical experience with this prosthesis will be presented.
The abstracts were prepared by Mrs Dorothy L. Granchi, Course Coordinator. Correspondence should be addressed to her at PMB 295, 8000 Plaza Boulevard, Mentor, Ohio 44060, USA.
