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. 2014 Mar 23;15:97.
doi: 10.1186/1471-2474-15-97.

Early Tissue Responses to Zoledronate, Locally Delivered by Bone Screw, Into a Compromised Cancellous Bone Site: A Pilot Study

Free PMC article

Early Tissue Responses to Zoledronate, Locally Delivered by Bone Screw, Into a Compromised Cancellous Bone Site: A Pilot Study

Joerg Arnoldi et al. BMC Musculoskelet Disord. .
Free PMC article


Background: In fracture treatment, adequate fixation of implants is crucial to long-term clinical performance. Bisphosphonates (BP), potent inhibitors of osteoclastic bone resorption, are known to increase peri-implant bone mass and accelerate primary fixation. However, adverse effects are associated with systemic use of BPs. Thus, Zoledronic acid (ZOL) a potent BP was loaded on bone screws and evaluated in a local delivery model. Whilst mid- to long-term effects are already reported, early cellular events occurring at the implant/bone interface are not well described. The present study investigated early tissue responses to ZOL locally delivered, by bone screw, into a compromised cancellous bone site.

Methods: ZOL was immobilized on fibrinogen coated titanium screws. Using a bilateral approach, ZOL loaded test and non-loaded control screws were implanted into femoral condyle bone defects, created by an overdrilling technique. Histological analyses of the local tissue effects such as new bone formation and osteointegration were performed at days 1, 5 and 10.

Results: Histological evaluation of the five day ZOL group, demonstrated a higher osseous differentiation trend. At ten days an early influx of mesenchymal and osteoprogenitor cells was seen and a higher level of cellular proliferation and differentiation (p < 5%). In the ZOL group bone-to-screw contact and bone volume values within the defect tended to increase. Local drug release did not induce any adverse cellular effects.

Conclusion: This study indicates that local ZOL delivery into a compromised cancellous bone site actively supports peri-implant osteogenesis, positively affecting mesenchymal cells, at earlier time points than previously reported in the literature.


Figure 1
Figure 1
Representative screw positioning and region of interest (ROI) in the lapine medial femoral condyle. A: Post-operative radiological images, demonstrating the appropriate location of the bone screw in the lapine bone (cranio-caudal and latero-medial (insert)). B: Histological section, showing the ROI for the histomorphometrical measurement.
Figure 2
Figure 2
Chronological events at the screw site in the overdrilled bone defect (differences between test and control sites are indicated by bold letters).
Figure 3
Figure 3
Representative photomicrographs of undecalcified sections of control (A, C ,E, G and I) or test (ZOL coated) (B, D, F, H and J) screws after 1 (A and B), 5 (C,E,G and D,F,H) and 10 (I and J) days stained with a modified paragon. Photomicrographs E and F are respectively high power views of photomicrographs C and D (frames). The signs of repair with formation of fibro-mesenchymal tissue and woven bone are increased in the test groups without evidence of cellular adverse effects. Yet at 5 days, the test group (picture H) showed more advanced signs of angiogenesis than the control group (picture G). Osteoclasts remained active around the test implants.

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