Biologics in Fracture Care

Introduction

Fractures are a common cause of morbidity, lost productivity in the work force, and a significant driver of costs in the medical economy. Although exact numbers are difficult to identify, one Finnish registry study reported 53.4 fractures per 1000 person-years in women and 24.9 per 1000 person-years in men. Delayed healing and nonunion remain as significant complications in the treatment of fractures. Reported rates of delayed healing and nonunion approach 600,000 and 100,000 per year, respectively, in the United States alone.

Considerable research has been dedicated to improving the ultimate healing rate of fractures and preventing complications. Biologic augmentation and supplementation in the treatment of fractures is a pivotal area of development. The U.S. Food and Drug Administration definition of biologic treatment for fractures covers a wide range of therapies, including blood and blood components, stem cells, tissue grafts, recombinant proteins, and gene therapies. Biologic treatments in general are aimed at enhancing one or more aspects of the natural process of fracture healing. This includes stimulating cells with the capacity to form bone to actually do so (osteoinduction), augmenting the number or availability of cells capable of producing bone (osteogenesis), enhancing vascular growth and proliferation, and providing a scaffold conducive for cellular attachment and bone construction (osteoconductive). Although a comprehensive review of the available literature on biologic treatment of fractures is well beyond the scope of this textbook, this chapter seeks to provide an overview of currently available biologic treatments for fracture care.

When to Consider Biologic Augmentation

The majority of fractures (90%–95%) do not require biological enhancement and will heal uneventfully on their own with simple immobilization or standard internal fixation techniques. No definitive indications for biologic augmentation of fracture treatments exist. However, common indications cited in the literature include fracture nonunion and bony defects. Critical sized bone defects, commonly defined as greater than 50% circumferential bone loss or a 2 cm defect, may result from bone loss in open fractures or secondary to resection of infected bone at a fracture site. In either case, the healing potential of the fracture environment is not robust enough to result in bony union, whether the healing response is compromised or the size of the defect exceeds the body’s natural capability for fracture healing.

The selection of a particular biological adjuvant will depend on the specific clinical scenario. For instance, bone marrow aspirate (BMA) injection may be useful in the setting of stably fixed, aseptic nonunions of the tibia. Segmental defects may require more comprehensive treatment, such as autogenous bone graft, which contains vascular proliferative qualities and includes osteogenic, osteoinductive, and osteoconductive components. Patient factors such as the presence of infection, soft tissue coverage, or other medical problems may influence the decision as well. The remainder of this chapter will discuss the various biologic materials available to solve the clinical problems of nonunion and bone defects.

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