Surface Roughness of Ceramic Femoral Heads after In-Vivo Transfer of Metal Correlation to Polyethylene Wear
A dark metallic-appearing smear resembling a lead pencil mark may be seen on the ceramic femoral head component at revision total hip surgery. The purpose of this study was to investigate the hypothesis that such a mark on a retrieved ceramic femoral head is associated with increased surface roughness of the head, and increased polyethylene liner wear in total hip arthroplasty.
Fifteen ceramic prosthetic femoral heads retrieved from fifteen patients at revision arthroplasty were examined in this study. Thirteen heads had been in vivo for an average of 10.8 years (range, 7.8 to 14.2 years). The remaining two heads had been in vivo for less than one month. The surface roughness characteristics of the explanted ceramic heads, the linear wear of the polyethylene liner, and the patient activity levels after primary replacement before revision were determined.
Four of thirteen ceramic heads which had been in vivo more than 7.8 years had severe (greater than 6% at the surface area) smears and the remaining nine heads had slight smears (less than 6% at the surface area). The two heads which had been in vivo less than one month had severe smears. The mean Ra and Rpm, surface roughness values, in the hips with slightly smeared regions were 26.38 nm and 323.82 nm, respectively and they were 180.77 nm and 1245.88 nm, respectively in the hips with severely smeared regions (P=0.002). The mean linear liner wear rate in the hips with slightly smeared heads was 0.10 mm per year and 0.19 mm per year in the hips with severely smeared heads (P=0.002). The activity score for all patients was 5 or 6 points on a 6 point scale.
The results of this study confirmed the hypothesis that a visual dark metallic-appearing smear on the ceramic femoral head correlates with increased surface roughness of the head and increased polyethylene wear. These findings imply that contact of a ceramic femoral head with a metallic material, such as may occur with femoral head reduction or dislocation of a total hip arthroplasty, is best avoided to prevent this metallic smear phenomenon.
KeywordsFemoral Head Wear Rate Polyethylene Wear Increase Surface Roughness Polyethylene Liner
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