A characteristic bony structure found at revision surgery for failed joint replacement, and implicated as being associated with poorer subsequent implant fixation, is a sclerotic bone rim (SB rim). This study is a histomorphometric analysis of the SB rim formed around an experimental canine micro-motion implant system under stable or unstable conditions with polyethylene (PE) particles, after 8 weeks. A point count histomorphometric analysis was performed to determine the cellular activity at the surface of the SB rim, and the morphology of the structure was determined by image analysis. A SB rim was found to form under both stable and unstable conditions, but with unstable conditions the rim was more distinct, thick, continuous, and was located near the drill hole, and had high and ongoing formative activity at both surfaces with little resorption. Under stable conditions, thinner second or third SB rims were observed. The difference in width and distance between implant and the SB rim is significant (p<0.05), as was the difference in fraction of resorption surfaces at the SB surface facing the implant. This study observed an in vivo primary bone response to controlled stable and unstable loaded implants. Sclerosis of trabeculae in a semi-continuous SB rim can serve to isolate the implant from the marrow space. The increases in SB rim width and continuity is consistent with the previously demonstrated knowledge that increase of total bone mass and low risk for trabeculae perforation is the consequence of low resorptive and high formative activity.
Bibliographical noteFunding Information:
We would like to thank Prof. Flemming Melsen, Ellen M. Hauge, Søren Kold and the Institute of Pathology at Aarhus University Hospital, who provided guidance and mentoring for histologic and pathologic evaluations. Orthopaedic Research and Education Foundation, NIH AR4205, Danish Research Foundation for Health, Master of a guild, butcher Peter Ryholts Foundation and the Danish Rheumatism Association, and Anna and Jakob Jakobsens Foundation. Biomet donated the PMMA implants.
- Bone histomorphometry
- Bone ingrowth
- Polyethylene particles
- Revision total joint
- Sclerotic bone rim (SB rim)