In Vitro characterization of low modulus linoleic acid coated strontium‐substituted hydroxyapatite containing PMMA bone cement

Abstract

Poly (methyl methacrylate) (PMMA) bone cement is widely used in vertebral body augmentation procedures such as vertebroplasty and balloon kyphoplasty. Filling high modulus PMMA increases the modulus of filled verterbra, increasing the risk of fracture in the adjacent vertebra. On the other hand, in porous PMMA bone cements, wear particle generation and deterioration of mechanical performance are the major drawbacks. This study adopts a new approach by utilizing linoleic acid coated strontium substituted hydroxyapatite nanoparticle (Sr-5 HA) and linoleic acid as plasticizer reducing bone cement's modulus with minimal impact on its strength. We determined the compressive strength (UCS) and modulus (Ec), hydrophobicity, injectability, in vitro bioactivity and biocompatibility of this bone cement at different filler and linoleic acid loading. At 20 wt % Sr5-HA incorporation, UCS and Ec were reduced from 63 ± 2 MPa, 2142 ± 129 MPa to 58 ± 2 MPa, 1785 ± 64 MPa, respectively. UCS and Ec were further reduced to 49 ± 2 MPa and 774 ± 70 MPa respectively when 15 v/v of linoleic acid was incorporated. After 7 days of incubation, pre-osteoblast cells (MC3T3-E1) attached on 20 wt % Sr5-HA and 20 wt % Sr5-HA with 15 v/v of linoleic acid group were higher (3.73 ± 0.01 x 10⁴, 2.27 ± 0.02 x 10⁴) than their PMMA counterpart (1.83 ± 0.04 x 10⁴). Incorporation of Sr5-HA with linoleic acid in monomer phase is more effective in reducing the bone cement's stiffness than Sr5-HA alone. Combination of low stiffness and high mechanical strength gives the novel bone cement the potential for use in vertebroplasty cement applications.

The effect of unsaturated fatty acid and triglyceride oil addition on the mechanical and antibacterial properties of acrylic bone cements

“…Interestingly, a much lower vol% (approximately 3 vol% compared to 15 vol%) of linoleic acid was needed to achieve a similar reduction in modulus in the current study compared to the study by Lam et al 43 However, in the study by Lam et al, the cements also contained 20 wt% (of powder) linoleic-acid functionalized strontium substituted hydroxyapatite particles, which hence appeared to limit the effect of the added linoleic acid, possibly due to the hypothesized formation of a copolymer on the particle-cement interface. 43 The setting time decreased for the cements containing ricinoleic acid and castor oil compared to the control, while the cement containing linoleic acid gave no significant difference.…”

“…43 The setting time decreased for the cements containing ricinoleic acid and castor oil compared to the control, while the cement containing linoleic acid gave no significant difference. The use of fatty acids or triglyceride oils also had a positive effect on the peak polymerization temperature, which was reduced by almost 30°C.…”

“…The authors reported similar compressive strength and a reduction of 62% in the Young's modulus when a modified liquid phase containing 2.57 wt% 4-N,N-dimethylaminobenzyl oleate was used. 32 Lam et al 33 modified bone cements with strontium-substituted hydroxyapatite-nanoparticles and linoleic acid, and reported a reduction of 15% in compressive strength and 57% in the Young's modulus when 15 vol% linoleic acid was incorporated into the liquid phase. 33 In previous work, we added castor oil to commercially available PMMA and found that 12 wt% castor oil decreased the strength and the Young's modulus by 83%…”

Mechanical Properties and Cytocompatibility Improvement of Vertebroplasty PMMA Bone Cements by Incorporating Mineralized Collagen

“…Many studies used HA and element-doped HA, such as strontium-doped HA to modify the PMMA bone cement. However, in some studies, the addition of HA largely decreased compressive strength of the bone cement that cannot meet the requirement of ISO 5833-2002 [23]; in some other studies, the compressive modulus even largely increased after the addition of HA [24]. Moreover, the addition of HA into PMMA bone cement did not exhibit improved biocompatibility [25].…”

Preoperative Motion-Related Pain in Cancer Patients with Extraspinal Metastases Treated by Percutaneous Osteoplasty

“…However, PMMA cement still has a few shortcomings such as high modulus, hydrophobicity, and lack of bioactivity. Hydroxyapatite instead of PMMA may increase the bone cement's bioactivity; however, it is more expensive, and may show less thermal or chemical nerve ablation, and less direct tumor thermal injury effect [9].…”