Cranioplasty is designed to cosmetically repair a cranial defect. After historically poor results with autografts, allografts & xenografts, skull defects are often either left untreated, resulting in soft tissue filling of the defect and a scalp depression, or treated with synthetic materials that can induce inflammatory response, fibrous encapsulation, infection, loosening, exposure of the implant, cosmetic deformities, and are unable to integrate to provide remodeling or to grow with the patient,essential for successful treatment of children.
In this pilot project, we will evaluate barrier membrane systems to overcome the limitations and complications of cranioplasty repair. We will evaluate collagen and resorbable chitosan membranes for ease of use and clinical superiority in guided bone regeneration (GBR) of craniotomy defects.
Bone defects are a significant clinical problem in orthopedics and neurosurgery, resulting from trauma and from iatrogenic defects created during surgery. Trephination dates from prehistoric neolithic times (10,000-7000 B.C.) and is the oldest operation known. Cranioplasty with bone allografts dates from the Stone Age Celts. Cranioplasty is a surgical procedure designed to provide a cosmetic appearance to the skull and to protect the brain following the development of a cranial defect. For a cosmetic appearance, the materials used must be able to be molded or pressed permanently into shape without breaking or cracking. For protective qualities, the material must ultimately be strong and its final shape must be unchangeable. Toward these ends, many foreign materials, synthetics, allografts, alloplastic metals & plastics, autografts, and even xenografts have been used. The primary obstacle to creating new bone is connective tissue invasion into healing bone. That is, ingrowth of soft tissue delaying and/or disrupting osteogenesis. Bone defects may be regained by osteogenesis, osteoinduction, osteoconduction or guided bone regeneration. Each one of these four processes may work independently but theoretically, a combination of any of these processes will give better results.
After historically poor results following placement of bone autografts, allografts, and xenografts for cranioplasty, residual skull defects following craniotomy procedures are often left untreated, resulting in soft tissue filling of the defect and a scalp depression at the site of each defect. Other common treatment modalities for craniotomy repair include the use of metal plates to cover the defects, or filling the defects with a curable plastic which can cause a marked inflammatory response and fibrous encapsulation of the implant, resulting in the possibility of infection, loosening, and exposure of the implant. Further, the plastic or the plate often causes cosmetic deformities and cannot integrate to provide a naturally remodeling tissue complex; nor can they grow with the patient, a requirement for successful treatment of children.
In this pilot project, we will address the clinical problem of cranial bone defects following surgery or trauma. Our goal is to identify a barrier membrane system that will make it easy and efficient to repair craniotomy defects and overcome the limitations or complications of leaving such defects empty, plating them, or filling them with plastic. We will evaluate a collagen membrane and a new resorbable chitosan membrane for ease of use and clinical superiority in the guided bone regeneration (GBR) of craniotomy defects. This pilot clinical trial will enroll twelve subjects scheduled for elective craniotomy procedures at the UAB Health Systems Hospitals.
We anticipate that the dense chitosan membranes will have excellent utility as implantable surgical membranes in oral, orthopedic, general, plastic, and dermatologic surgeries, among other uses. The Magenta Medical Membrane (Agenta’s dense chitosan membrane) is biocompatible and resorbable in a rat oral palate model. In orthopedics, one can envision membrane barriers between bone and soft tissues, for instance, as complements to long bone fractures (especially open fractures) being repaired with hardware and/or bone graft substitutes. In these cases, and in vertebral reconstruction, the dense chitosan membranes could be sutured, tacked, and/or stapled in place to prevent in-growth by soft tissue (e.g., fibroblasts) and diffusion of cements or biologics. In general surgery, the membranes could be sutured in situ to provide strength to repair hernias, or to prevent post-surgical tissue adhesion of visceral organs. In plastic surgery, the membranes could be used to augment soft tissue defects (e.g., facial and breast reconstruction). In dermatologic surgery the membranes could be used as either intact sheets or in mesh form with holes to promote the healing of cutaneous burns or ulcers, essentially as a wound dressing. In conclusion, the surgical indications of use for this new material are myriad and provide additional significance beyond the present craniotomy model.
At present there are multiple types of resorbable membranes that are commercially available as US FDA 510(k)-cleared Class II devices. The most common are reconstituted bovine and porcine collagens, although other biomaterials are available commercially (e.g., synthetic polymers of lactate and/or glycolate, and processed xenograft tissues). Published data indicate in head-to-head comparisons that the dense chitosan membranes have properties meeting and often exceeding those of commercial collagen membranes. Reconstituted collagen membranes represent the current standard-of-care in many, if not most, surgical indications. Compared to the new dense chitosan membranes, the BioMend Absorbable Collagen Membrane exhibited lower tensile strength and resistance to suture pull-out. In addition, the clinical handling characteristics of the dense chitosan membranes are superior to that collagen membrane with regard to “memory” while wet, and the ability to discriminate between the material and surrounding tissues helping to guide placement of the membrane.
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