Pandit et al. (2009) reported on a RCT comparing 62 patients who received either cemented (n = 32) or cementless (n = 30) versions of the OUKA. The tibial interfaces were studied with fluoroscopically-aligned radiographs. At one year there was no difference in clinical outcome between the two groups. Narrow radiolucent lines were seen at the bone-implant interfaces in 75% of cemented tibial components. These were partial in 43%, and complete in 32%. In the cementless implants, partial radiolucencies were seen in 7% and complete radiolucencies in none. These differences are statistically significant (p < 0.0001) and imply satisfactory bone ingrowth into the cementless implants. These results continued to show the same trends at five years with no complete radiolucencies in the cementless group (28% in the cemented implants), confirming stable and superior fixation with the cementless OUKA as compared to the cemented OUKA.
Radiolucencies are commonly seen beside the vertical wall but we consider them to be of no significance as this is non-weightbearing.
We have seen very few cases of complete radiolucencies around cementless components so we know little about their significance. The cases we have seen have been associated with tibial subsidence and pain, at about three to six months post surgery. With time, the symptoms settled and the radiolucency disappeared, suggesting that the implant had become securely fixed (Fig. 9.4). We would not have expected this to occur with a cemented component. We have not seen complete radiolucencies around cementless components in the long term.
