Surgery – Truss – Pad
Patent
1979-11-13
1984-09-11
Frinks, Ronald L.
Surgery
Truss
Pad
3 191, 128 92C, A61F 124
Patent
active
044701586
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
Broadly speaking, this invention relates to joint endoprotheses and more specifically to a joint endoprosthesis with area contact bearing engagement and only two degrees of freedom of rotational movement between a first bone and a second bone while the bearing surfaces are kept in area contact engagement under the action of the joint.
BACKGROUND ART
For the sake of brevity and convenience, the discussion of the prior art here will be generally limited to the ankle, and prior art ankle prostheses with later discussion of the knee; accordingly:
As is known to those skilled in the art, until quite recently, fusion was the primary mode of treatment for the most disabling conditions of the ankle joint. The reason for this was that fusion of the ankle produces much less disfigurement and loss of function than does fusion of any other major load-bearing joint. Thus, ankle fusion, even with its attendant loss of function, remains a therapeutically acceptable procedure. Nevertheless, fusion, by its very nature, should be considered redical surgery--the last possible alternative in joint reconstruction. If effective prosthetic surfaces can restore normal ankle function, then such an alternative is certainly more desirable than fusion.
The article by Pappas, Buechel and DePalma entitled "Cylindrical Total Ankle Joint Replacement" which appeared in Clinical Orthopaedics and Related Research, No. 118, July-August 1976, pp. 82-92, surveys the various ankle prostheses which have been developed to date. All such prostheses are metal-to-plastic articular surface replacement types which essentially rely on ligamentous control for stability. The fundamental differences in the various designs lie in the nature of the articulating surfaces. Two basic types are found: those with theoretical line or point contact articulating surfaces and those with area contact articulating surfaces.
The incongruent surface types all permit the normally observed axial rotation in addition to permitting flexion-extension. However, incongruent surface prostheses suffer from two basic defects: (1) relatively poor wear and poor deformation resistance due to high local stress resulting from incongruent surface contact, and (2) relatively poor inherent stability. High local stresses and pressures resulting from normal walking loads, even with a relatively small amount of incongruity, result in permanent deformation of the ultra-high molecular weight polyethylene (UHMWPE) used in all known current ankle prostheses, as well as a relatively high wear rate.
In addition, since the human ankle joint possesses essentially congruent surfaces, one cannot expect an incongruent replacement joint to approximate normal motion since the kinematic properties of congruent and incongruent surfaces are so different.
Prostheses utilizing congruent or area contact surfaces, on the other hand, have good pressure distribution and, thus, offer superior wear and surface deformation resistance when compared to incongruent types. Further, they provide nearly normal stability because, under compressive load, the surfaces are forced into conformity and therefore motion to a large extent is defined by the surface geometry, thus providing predictable motion characteristics. Four basic variations of the area contact surface prosthesis are known. These are (1) spherical (e.g. ball and socket); (2) spheroidal (e.g. barrel-shaped); (3) cylindrical; and (4) conical.
The spherical prosthesis allows three independent axes of rotation but the joint surface geometry dictated by such a design tends to limit the flexion-extension range. Further, the spherical type ankle prosthesis is also less resistant to inversion-eversion injuries caused by substantially greater than normal loading of the ligaments and also is unstable since it allows an inversion-eversion motion between the tibia and talus that is not normally present. This lack of stability has been observed clinically.
The spheroidal type of prosthesis provides two independent rotations, plantar and dorsiflexion an
REFERENCES:
patent: 3816855 (1974-06-01), Saleh
patent: 3878566 (1975-04-01), Bechtol
patent: 3964106 (1976-06-01), Hutter, Jr. et al.
patent: 4016606 (1977-04-01), Murray et al.
patent: 4041550 (1977-08-01), Frazier
patent: 4081866 (1978-04-01), Upshaw et al.
patent: 4085466 (1978-04-01), Goodfellow et al.
patent: 4094017 (1978-06-01), Matthews et al.
patent: 4216549 (1980-08-01), Hillberry et al.
patent: 4219893 (1980-09-01), Noiles
Buechel Frederick F.
Pappas Michael J.
Biomedical Engineering Corp.
Frinks Ronald L.
Rhodes, Jr. R. Gale
LandOfFree
Joint endoprosthesis does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Joint endoprosthesis, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Joint endoprosthesis will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1188518