BONE INGROWTH AND WEAR DEBRIS IN WELL-FIXED CEMENTLESS POROUS-COATED TIBIAL COMPONENTS REMOVED FROM PATIENTS

Bone ingrowth and the distribution of wear debris within the porous co ating of 13 primary cementless porous-coated tibial components removed for reasons unrelated to fixation or infection were quantitatively de scribed. The average length of implantation was 15.3 months (range, 3- 30 months). The implants were all of the same design, made from Ti6Al4 V with a commercially pure titanium fiber-metal porous coating, which covered the undersurface of the tray and the four fixation pegs. In al l but one component, supplemental screw fixation was used. The average extent of bone ingrowth within the tray was 27.1 +/- 16.1%, and the a verage volume fraction was 9.5 +/- 7.5%. There was significantly more bone ingrowth within the fixation pegs than within the tray and also m ore bone ingrowth in the anterior half of the tray than posteriorly. T here was no correlation between the amount of bone ingrowth and the le ngth of implantation, age, or sex of the patient; however, the depth a nd orientation of the resection plane were found to correlate with the topographic distribution of bone ingrowth. Particulate debris appeare d to gain access to the interface via soft tissue pathways both at the periphery and through the holes for adjuvant screw fixation.