Tohoku J. Exp. Med., 2025 May, 266(2)

Efficacy of Octacalcium Phosphate/Gelatin (OCP/Gel) Composite Implantation for Miniature Swine Lumbar Interbody Fusion

Yu Mori,¹ Ryo Hamai,² Ryuichi Kanabuchi,¹ Takahiro Onoki,¹ Kohei Takahashi,¹ Ko Hashimoto,¹ Toshimi Aizawa¹ and Osamu Suzuki²

¹Department of Orthopaedic Surgery, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
²Division of Craniofacial Function Engineering, Tohoku University Graduate School of Dentistry, Sendai, Miyagi, Japan

Synthetic octacalcium phosphate (OCP) has emerged as a potential precursor for bone apatite crystals, promoting faster bone formation and better biodegradability compared to hydroxyapatite and β-tricalcium phosphate materials. Combining OCP with various polymeric biomaterials enhances its ductility, making it suitable for clinical applications, including dentistry. Preclinical studies on OCP/gelatin (OCP/Gel) composites have shown excellent osteoconductive and osteoinductive properties, indicating potential for bone defect repairs. This study investigates the efficacy of OCP/Gel as a filler for lumbar interbody fusion cages. A miniature swine model underwent surgery using polyetheretherketone (PEEK) cages with different fillers: no filler, autologous rib, and OCP/Gel. Eight weeks post-surgery evaluations using computed tomography, histological assessments, and Fourier transform infrared (FT-IR) spectroscopy revealed that while PEEK cages without fillers showed no bone fusion, those with autologous rib and OCP/Gel demonstrated partial interbody fusion. Histological analysis indicated new bone growth in cages with OCP/Gel, and FT-IR spectroscopy confirmed the degradation of OCP at the vertebral interface and increased bone matrix proteins. The findings suggest that OCP/Gel could be a viable alternative to autologous bone grafts for lumbar interbody fusion surgeries, offering less invasive and more cost-effective solutions. The success of OCP/Gel in clinical applications could pave the way for broader use in orthopedic reconstructive surgeries, potentially eliminating the need for combined use of bone marrow aspirate or expensive growth factors.

Key words —— bone graft substitute; gelatin; interbody fusion; octacalcium phosphate; osteogenesis

© 2025 Tohoku University Medical Press

===============================

Tohoku J. Exp. Med., 2025 May, 266(2), 135-144.

Correspondence: Yu Mori, Department of Orthopaedic Surgery, Tohoku University Graduate School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi 980-8574, Japan.

e-mail: yu.mori.c4@tohoku.ac.jp

Correspondence: Osamu Suzuki, Division of Craniofacial Function Engineering, Tohoku University Graduate School of Dentistry, 4-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi 980-8575, Japan.

e-mail: suzuki-o@tohoku.ac.jp