Total condylar knee arthroplasty. Prosthetic component positioning and radiolucent lines.

Prosthetic positioning and overall postoperative alignment were studied in 138 consecutive total knee replacements, using the Insall/Burstein total condylar knee system. Overall alignment was within 7 +/- 5 degrees of valgus in 63 per cent of the knees, while tibial component positioning was within 4 degrees of tilt in any direction in 53 per cent of the knees. A radiolucency index incorporating width and extent of radiolucent zones at the tibia was shown to progress from 3 months to 2 years postoperatively. The radiolucency index 2 years postoperatively was higher with postoperative varus alignment in the rheumatoid arthritis group; a tibial component tilt of more than 4 degrees in any direction increased the radiolucency index in both treatment groups.