Use of an advanced formulation of beta-tricalcium phosphate as a bone extender in interbody lumbar fusion.

Despite numerous advances in the development of bone graft substitutes over the past 20 years, iliac crest autograft remains the gold standard for lumbar spinal fusion. However, donor site morbidity associated with the harvesting of iliac crest autograft remains problematic. Acute and chronic pain, prolonged operative time, bleeding, infection, deformity, and nerve and vascular injury still produce significant postoperative morbidity, even in the presence of careful surgical technique. Although allograft circumvents donor site morbidity, the growing number of spinal fusions performed in the United States and worldwide is creating a shortage of cadaver bone acceptable for use. Additionally, the extensive processing and storage of allograft is expensive. Synthetic materials, such as beta-tricalcium phosphate (beta-TCP), have been developed as alternatives to both autograft and allograft. A novel formulation of ultraporous beta-TCP (Vitoss, Orthovita, Malvern, Pa) offers interconnected microporosity, providing it with good wicking and hydrophilic properties. These properties allow the migration of nutrients, growth factors, and osteogenic cells into the ultraporous beta-TCP scaffold, thereby promoting new bone growth and concurrent scaffold resorption. This study presents a retrospective review of 7 patients who underwent anterior (ALIF) or posterior (PLIF) interbody fusion at 12 levels with a 3- to 6-month follow-up. At the patients' last radiographic examination, all 12 levels were solidly fused with interbody grafting material consisting only of allograft plus a combination of ultraporous beta-TCP and venous blood as an extender. Additionally, all 7 patients had segmental pedicle-screw fixation.