EMULSION TEMPLATING - Intelligent Scaffolds for Tissue Engineering and Regenerative Medicine - page 666

medical care. Orthopedic conditions such as sprains, fractures,
arthritis, back pain, and bone tumors result in 136.8 million ambu-
latory health care visits, more than 3 million hospitalizations, 245
billion dollars in medical costs, and 488 million days of restricted
work activity each year. Overall, musculoskeletal ailments comprise
more than 14% of health care expenditures in the United States. . 2
A commonly encountered challenge for reconstructive surgeons is
treatment of large bony defects resulting from traumatic injury,
tumor resection, degenerative diseases, and congenital deformi-
ties. Although small defects in bone are effectively repaired natu-
rally, the body is often incapable of repairing these large defects. 5 , 6
Nationwide Inpatient Statistics show that over 1,100,000 surgi-
cal procedures involving the partial excision of bone, bone graft-
ing, and inpatient fracture repair were performed in 2004 at an
estimated total cost of over $5 billion, illustrating the impor-
tance of addressing the functional, aesthetic, and social impact of
such defects. 7 An important area of musculoskeletal research has
focused on biocompatible orthopedic implants for the treatment of
nonunion defects, replacement of diseased tissue, and maxillofacial
surgery.
Surgeons have long been interested in producing a synthetic
bone-grafting material that can accelerate the healing process,
integrate well with the surrounding tissue, and later remodel to
resemble native bone. During the past century, a wide variety of
alloplastic materials were utilized in reconstruction therapies,
including celluloid, aluminum, gold, vitallium, tantalium, stainless
steel, titanium, methyl methacrylate (MMA) resins, polyethylene,
silicone elastomers, and hydroxyapatite ceramics. Drawbacks and
complications inherent in the use of current alloplastic materials
include inadequate tissue integration, limited biodegradability, and
stress shielding. 8 − 16 Biologically active implants such as deminer-
alized bone matrix obtained from allogeneic or xenogeneic sources
have shown promise as reconstructive materials because of their
high osteoinductivity, but drawbacks include the risks of disease
transmission as well as cost. 8 , 14 The current gold standard for new
bone-graftingmaterialscontinuestobeautogenousboneasaresult
of its potential for growth and remodeling as well as its ability to
osseointegrate. Although often used, these treatments have several