Fatigue behavior of a titanium femoral hip prosthesis with proximal sleeve-stem modularity

✍ Scribed by Jan Janusz Krygier; Ariel Ricardo Dujovne; John Dennis Bobyn

• Publisher: Wiley (John Wiley & Sons)
• Year: 1994
• Tongue: English
• Weight: 727 KB
• Volume: 5
• Category: Article
• ISSN: 1045-4861
• DOI: 10.1002/jab.770050304

✦ Synopsis

Modular hip prostheses are increasing in variety and utilization. Component stability, high endurance limit, and minimal particulate debris generation are critical for long-term clinical success. The purpose of this study was to characterize the fatigue response and evaluate the in v i m potential for component motion and wear of the S-ROMTM, a Ti-6A1-4V hip prosthesis with a modular design based on a Morse taper connection. A fatigue jig was designed to simulate fixation of the device at the sleeve-bone interface only with distal support mainly against the lateral endosteal cortex. Two series of tests were performed in air at room temperature: one with direct vertical loading (to produce high bending moments in the coronal plane) and one with a compound loading angle directed at 15" out-of-plane (to include torsional physiological loads). Applied loads using a servohydraulic test machine ranged from 5 X BW (body weight) to 9 X BW (1 X BW = 73 kg, =160 Ib) at 10 Hz on an Instron apparatus. No mechanical failures were observed on the 11-mm size stems below 6 X BW for in-plane vertical loading, and at or below 7 X BW for out-of-plane loading. Using displacement monitoring with a sensitivity of 35 pm, no measurable slippage or relative motion was detected between the stem and sleeve when they were properly assembled. Examination of the contact areas with scanning electron microscopy revealed random surface modification (an indication of fretting or burnishing) with occasional evidence of transfer of material between stem and sleeve. At loads under 7 X BW there was no visual evidence of loose wear debris in the presence of gross stability. Overall, the extent of surface change or wear was relatively small in all components tested at physiological load levels.