Clin Orthop Surg.  2014 Mar;6(1):87-95. 10.4055/cios.2014.6.1.87.

Negative Effect of Rapidly Resorbing Properties of Bioactive Glass-Ceramics as Bone Graft Substitute in a Rabbit Lumbar Fusion Model

• Lee JH
• Ryu HS
• Seo JH
• Lee DY
• Chang BS
• Lee CK

• KMID: 1737636
• DOI: http://doi.org/10.4055/cios.2014.6.1.87

Abstract

BACKGROUND
Bioactive glass-ceramics have the ability to directly bind to bones and have been widely used as bone graft substitutes due to their high osteoconductivity and biocompatibility. CaO-SiO2-P2O5-B2O3 glass-ceramics are known to have good osteoconductivity and are used as bone graft extenders.
METHODS
This study aimed to evaluate the effects of the resorbing properties of glass-ceramics in bone fusion after producing and analyzing three types of CaO-SiO2-P2O5-B2O3 glass-ceramics with high osteoconductivity that had enhanced resorption by having an increased B2O3 content. The three types of CaO-SiO2-P2O5-B2O3 glass-ceramics with B2O3 contents of 8.0, 9.0, and 9.5 weight % were designated and grouped as P20B80, P10B90, and P5B95, respectively. Glass-ceramic types were tested for fusion rates and bone formation by employing the lumbar 5-6 intertransverse process fusion model in 51 New Zealand male rabbits. Bioactivity was assessed by soaking in simulated body fluid (SBF).
RESULTS
In vitro study results showed sufficient hydroxycarbonate apatite layer formation occurred for P20B80 in1 day, for P10B90 in 3 days, and for P5B95 in 5 days after soaking in SBF. For the rabbit lumbar spine posterolateral fusion model, the autograft group recorded a 100% fusion rate with levels significantly higher than those of P20B80 (29.4%), P10B90 (0%), and P5B95 (14.3%), with high resorbing properties. Resorbing property differences among the three glass-ceramic groups were not significant. Histological results showed new bone formation confirming osteoconductivity in all three types of glass-ceramics. Radiomorphometric results also confirmed the resorbing properties of the three glass-ceramic types.
CONCLUSIONS
The high resorbing properties and osteoconductivity of porous glass-ceramics can be advantageous as no glass-ceramics remain in the body. However, their relatively fast rate of resorption in the body negatively affects their role as an osteoconductive scaffold as glass-ceramics are resorbed before bony fusion.

Keyword

CaO-SiO2-P2O5-B2O3 glass ceramics; Osteoconductivity; Resorption; Fusion

MeSH Terms

Animals
Bone Resorption
Bone Substitutes/adverse effects/*therapeutic use
Ceramics/adverse effects/*therapeutic use
Electric Conductivity
Lumbosacral Region/*surgery
Male
Rabbits
Spinal Fusion/*methods
Bone Substitutes
Ceramics

Figure

• 

  Fig. 1 Radiomorphometric analysis. The percentage of the area of glass-ceramics at 12 weeks postoperatively (PO) compared to that immediately postoperatively (IPO).

• 

  Fig. 2 In vitro results using simulated body fluid (SBF). Formation of the hydroxycarbonate apatite layer after soaking in SBF was observed in 1 day in the P20B80 group (A), in 3 days in the P10B90 group (B), and in 5 days in the P5B95 group (C).

• 

  Fig. 3 Radiological results of the P20B80, P10B90, P5B95, and autograft groups. The autograft group was considered to have fusion because the trabecular bridging between the upper and lower transverse processes was clear. In comparison, the volume of the graft with the three glass-ceramics types declined at 12 weeks postoperatively from the immediate postoperative (IPO) levels, and was, thus, thought to be resorbed.

• 

  Fig. 4 Undecalcified histologic findings of the three glass-ceramics implant types at 12 weeks postimplantation (H&E, ×12.5, ×40, ×100) in the P20B80 (A), P10B90 (B), and P5B95 (C) groups. Newly formed bony tissues were found in and around all three kinds of glass-ceramic types. Arrows: newly formed bone, Stars: implanted glass-ceramics.

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