geometric analysis of commonly used prosthetic systems for proximal humeral replacement* by michael...

Geometric Analysis of Commonly Used Prosthetic Systems for Proximal Humeral Replacement*

by MICHAEL L. PEARL, and SAM KURUTZ

J Bone Joint Surg AmVolume 81(5):660-71

May 1, 1999

©1999 by The Journal of Bone and Joint Surgery, Inc.

Fig. 1 Schematic representation showing the geometry of the prosthesis.

MICHAEL L. PEARL, and SAM KURUTZ J Bone Joint Surg Am 1999;81:660-71


Fig. 2 Anteroposterior radiograph of the proximal aspect of a humerus from a cadaveric specimen, showing the center of rotation (black dot), the base of the articular surface (white

broken line), and the center line of the reamed canal (vertical black line).



Fig. 3 Illustration showing the placement of the osteotomy (broken line) at 45 degrees on specimens with head-shaft angles of 45 degrees (A), 32 degrees (B), and 51 degrees (C).



Fig. 4 Plot of the articular surfaces for the prosthesis (shaded) and specimen (clear) combination with the least displacement of the articular surface.



Figs. 5-A and 5-B: Plots of articular surfaces showing the best match of the Bio-Modular and Kirschner II-C prostheses to the same specimen shown in Fig. 4.



Fig. 5-B The Kirschner II-C prosthesis that was selected had a stem-head angle of 50 degrees and a radius of curvature of 25.4 millimeters.



Fig. 6 Plot of articular surfaces for the prosthesis (shaded) and specimen (clear) combination with maximum displacement of the center of rotation (CR) (31.4 millimeters).



Fig. 7 Plot of articular surfaces for the prosthesis (shaded) and specimen (clear) combination with greatest diminution in the arc of the articular surface (41 degrees), from 161 to 120 degrees.



Figs. 8-A and 8-B: Plots of articular surfaces for the Global shoulder prosthesis and the same specimen as shown in Fig. 7, with use of larger head sizes.



Fig. 8-B A prosthesis with a large-sized head.



Figs. 9-A and 9-B: Plots of articular surfaces for the Global shoulder prosthesis and specimen, with use of both algorithms.



Fig. 9-B Plot of the Global shoulder prosthesis with a head-shaft angle of 45 degrees.



geometric analysis of commonly used prosthetic systems for proximal humeral replacement* by michael...

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