Date of Award

10-31-1993

Document Type

Thesis

Degree Name

Master of Science in Biomedical Engineering - (M.S.)

Department

Biomedical Engineering Committee

First Advisor

Clarence W. Mayott

Second Advisor

Mark Zimmerman

Third Advisor

J. Russell Parsons

Fourth Advisor

Joseph Benevenia

Abstract

Osteosarcoma is the most common malignant bone tumor in the pediatric age group. This thesis presents the analysis of a total femoral prosthesis implanted in a 9 year old black male. The design includes a bipolar, expanding mid-shaft component, and a rotating hinge knee used in the reconstruction of the patient's right lower limb after surgical resection of the femur. The areas being analyzed are (i) the trochanteric attachment, (ii) the expanding component, and (iii) the rotating hinge knee. The stresses acting on the cables reconnecting the greater and lesser trochanter were determined for bipedal stance, single-legged stance, stance phase of gait, running and they were calculated to be 0.5 MPa, 17 MPa, 23 MPa and 51 MPa respectively. On comparing these stresses to the fatigue data for stainless steel cables, it is estimated that the cables will last for 108 cycles The expanding component cross-pin was analyzed to experience loads of up to three times the body weight. The maximum stress required for failure is 275 MPa at 107 cycles. The cross-pin is not expected to fail in fatigue. The cylindrical bearing surfaces in the rotating hinge knee experience contact stresses of 11 MPa, which is higher than the maximum stress under fatigue loading of polyethylene. The polyethylene bearing component will need to be replaced at about 104 cycles. Rotating knee hinge-pin component was analyzed in bending and shear, the low stresses (100 MPa and 11 MPa respectively) on the pin would give a working life of more than 107 cycles. The carriage-pin experiences a maximum bending stress of 98.16 MPa which is less than 50% of the maximum stress required for the titanium alloy to fail at 107 cycles.

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