The long-term survival of hip prosthesis is thought to depend partly on osteolysis in the proximal femur after insertion of the prosthesis. There are several studies using dual energy X-ray absorptiometry (DXA) for determining the bone loss after insertion of prosthesis, mainly with uncemented stems.
Most of these studies have used the postoperative measurement as a reference value. The exact time of these postoperative measurements is often not written in the papers and may differ with several days. We performed a study with a reversed hybrid to find out if there was a rapid bone loss post operatively and a following significant difference between such early measurements.
Our results showed that there was no bone loss during the first 14 days after operation. We concluded that all measurements done within 14 days after operation could be used as a reference for later measurements.
Since there has been problems with proximal osteolysis with uncemented stems there is a need to find alternative technologies for fixation of stems, which may retain more bone. Although plasma sprayed HA coatings seem to give good fixation in the femur, alternative coatings which may influence bone mineral density around the prosthesis, and eventually be a carrier for bone active substances could be an advantage. One such coating is the galvanically applied Bonemaster® HA coating. We have carried out the first clinical studies with the Bonemaster® coating. We compare bone remodeling (DXA) and migration (RSA) after insertion of Taperloc uncemented stem with two different hydroxyapatite coatings.
The bone remodeling analysis of proximal femur came up with significantly higher values for bone mineral density in the Bonemaster-group than the HA-group after two years. HA has never been proven to be osteoinductive before, but because of these promising results we performed an animal study to find out if this particular form of HA could be osteoinductive. Titan discs with 4 different surfaces were implanted in rabbit muscles. Bonemaster® on titanium turned out to be osteoinductive.
Head of project: Lars Nordsletten
Measurement of early bone loss around an uncemented femoral stem
Acta Orthop, 82 (3), 321-4