Enhancement of periprosthetic bone quality with topical hydroxyapatite-bisphosphonate composite

Sanjeev J. Suratwala, Samuel K. Cho, Jonathan J. Van Raalte, Hyun Park Sang, Wook Seo Sung, Seong Sil Chang, Thomas R. Gardner, Francis Young In Lee

Research output: Contribution to journalArticlepeer-review

36 Scopus citations

Abstract

Background: Implant loosening is associated with inflammatory bone loss induced by ultra-high molecular weight polyethylene wear debris. We hypothesized that a hydroxyapatite-bisphosphonate composite improves periprosthetic bone quality and osseous integration of an intramedullary implant even in the presence of ultra-highmolecular weight polyethylene particles in an experimental rat femur model. Methods: A preliminary in vitro study determined the optimal concentration of zoledronate (50 mM) that would maximally decrease osteoclasts without harming osteoblasts. Hydroxyapatite-coated intramedullary nails were implanted bilaterally in the femora of sixteen rats (the control group), and hydroxyapatite-zoledronate-coated nails were implanted bilaterally in the femora of sixteen rats (the experimental group). Ultra-high molecular weight polyethylene particles were introduced into the femoral canal before implantation. Eight rats fromeach group were killed at six weeks, and the remaining rats were killed at six months. Periprosthetic bone mass was analyzed by dual x-ray absorptiometry and microcomputed tomography. Osseous integration was examined by biomechanical testing of pullout strength. Results: Themean bone area (and standard deviation) inthe periprostheticbone regionwas significantly greater (p<0.0001) in the hydroxyapatite-zoledronate group (2.388 ± 0.960mm2) than in the control group (0.933 ± 0.571 mm 2). This difference was larger in the six-week group than in the six-month group (p = 0.03). The average peak pullout force for the treated femora (241.0 ± 95.1 N) was significantly greater (p < 0.0001) than that for the controls (55.6 ± 49.0 N). This difference was similar in the six-week and six-month groups. The energy required for nail pullout was significantly greater (p < 0.0001) for the treated femora (521.6 ± 293.8 N-mm) than for the controls (142.2 ± 152.1 N-mm). This difference in energy to pullout was similar in the six-week and six-month groups. Regression analysis demonstrated a high correlation between periprosthetic bone mass and peak pullout force for both the six-week (r = 0.766, p = 0.0005) and six-month (r = 0.838, p < 0.0001) groups. Conclusions: Surface modification of implants with hydroxyapatite-zoledronate improves periprosthetic bone quality and osseous integration. Clinical Relevance: Hydroxyapatite-based site-specific delivery of bisphosphonates may be one way of reducing ultrahigh molecular weight polyethylene wear particle-induced periprosthetic osteolysis and implant loosening.

Original languageEnglish
Pages (from-to)2189-2196
Number of pages8
JournalJournal of Bone and Joint Surgery
Volume90
Issue number10
DOIs
StatePublished - 1 Oct 2008
Externally publishedYes

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