Sphenoethmoid cerebrospinal fluid leak repair with hydroxyapatite cement.

Despite advances in neurological, reconstructive, and endoscopic sinus surgery, sphenoethmoid cerebrospinal fluid (CSF) fistulae continually pose difficult management problems. Standard surgical techniques for fistulae closure succeed approximately 78% to 90% of the time. To improve this success rate, hydroxyapatite cement (HAC), a Food and Drug Administration-approved substance for cranial defect repair, was applied to this problem in a clinical setting. Twenty-one patients with spontaneous, posttraumatic, or postoperative CSF leaks of the sphenoid sinus, cribriform plate, or ethmoid region were treated with HAC. Study participants were prospectively accrued at 5 tertiary care medical centers in the eastern United States. The CSF leaks of all 21 patients treated with HAC were successfully sealed by its initial application. The sites of CSF leakage included the nasal cavity (n = 2) and sphenoid sinus (n = 19). Fifteen of the patients had previously undergone a failed repair by standard methods. There have been no recurrent CSF leaks with a maximum follow-up of 72 months, and an average follow-up of 36 months. All patients have survived to date. The only HAC-related morbidity was the extrusion of the HAC when placed in the nasal cavity. Hydroxyapatite cement is an effective method of repair for postoperative, posttraumatic, and spontaneous sphenoid CSF leaks. The efficacy of HAC in sealing the CSF leak was unaffected by previous attempts at leak closure by standard methods or by its origin. Hydroxyapatite cement should not be applied transnasally for the treatment of an ethmoid region fistula owing to its high probability of extrusion. Correct patient selection and technical familiarity with HAC are necessary for successful application.

Future directions in biomaterial implants and tissue engineering.

Over the last 50 years, we have gained much knowledge about biomaterial implants by incorporating the fields of basic biologic science and engineering science. Future implant developments will have a significant impact on facial cosmetic and reconstructive surgical therapy.

Morphological and phase characterizations of retrieved calcium phosphate cement implants.

A self-hardening calcium phosphate cement (CPC), consisting of equimolar amounts of tetracalcium phosphate and dicalcium phosphate anhydrous, hardens when mixed with water and forms a resorbable hydroxyapatite (HA) as the end-product. The objective of this study was to investigate the changes of the phase and morphology of the CPC during hardening and aging under in vivo conditions. CPC samples retrieved 12 h after hardening in vivo had already contained carbonated HA (type B), even though the initial cement mixture did not contain carbonate as one of the solid components. The mass fraction of carbonate in the 12-h sample was about 1%. The results suggested that under in vivo conditions carbonate is readily available and this allows formation of carbonated HA in favor of carbonate-free HA. The carbonate content of the CPC samples retrieved 3 months after implantation was similar to that of the 12-h samples, and the exterior surfaces of the 3-month samples appeared less crystalline than that of the 12-h samples.

Reconstruction of the frontal sinus and frontofacial skeleton with hydroxyapatite cement.

OBJECTIVE: To evaluate the efficacy of a newly developed biomaterial, hydroxyapatite cement, for use in frontal sinus and anterior craniofacial skeletal reconstruction. DESIGN: A nonrandomized patient cohort that was compared with historical controls of standard treatment with methyl methacrylate implants. SETTING: Craniofacial reconstructive surgery services at 3 referral health care centers. Eligible patients had frontal-cranial defects limited to a maximum size of 25 cm2. Patients were randomly selected volunteers with preexistent, acute traumatic or acute surgically induced defects of the frontal sinus and anterior craniofacial skeleton. All patients provided informed consent, and the study was approved by the 3 institutional review boards. Forty patients underwent reconstruction of defects of the anterior craniofacial region, and 38 of these patients were evaluable at 24 months. MAIN OUTCOME MEASURES: Hydroxyapatite cement was used to reconstruct full-thickness anterior craniofacial skull defects. Standard surgical techniques were used to place all implants. The primary outcome measurement was maintenance of implant volume determined at 24 months by computed tomography and clinical examination. Secondary outcome measures included incidence of complications and infections necessitating implant removal. RESULTS: Of the 38 evaluable patients, 31 had successful reconstructions at the end of the study, for an overall success of 82% for frontal sinus and frontofacial region reconstruction. Seven patients underwent explantation, 5 for surgical access to the site. Two implants were removed because of infection in the wound, for an overall incidence of approximately 5%. Explant biopsy specimens confirmed implant osseointegration and vascularization. CONCLUSIONS: Hydroxyapatite cement successfully reconstructs full-thickness defects of the frontal sinus and frontofacial region at 24 months. Hydroxyapatite cement appears to be superior to acrylic implants for frontal-cranial reconstruction and by allowing implant osseointegration with improved biocompatibility.

Primary extraosseous cemento-ossifying fibroma of the auricle.

BACKGROUND: A mass of the auricle is uncommon. An enlarging lesion may be the result of a reactive process, or a benign or malignant neoplasm. The literature is reviewed, and a case of extraosseous cemento-ossifying fibroma of the auricle is presented. METHODS: A 22-year-old white man presented with a 3-month history of an enlarging 2 cm mass in the right concha cavum. An incisional biopsy demonstrated cemento-ossifying fibroma. The lesion was resected en bloc, and the patient did well. There is no evidence of recurrence. RESULTS: Pathological examination of the excised mass revealed a well-circumscribed but unencapsulated spindle cell lesion with foci of osteoid and cementum deposition. It did not involve the auricular cartilage, and there was no connection with the overlying epidermis. CONCLUSIONS: This is a case report of an extraosseous cemento-ossifying fibroma of the auricle. This benign tumor should be completely excised because local recurrence may otherwise result.

Current use of bone substitutes in maxillofacial surgery.

The use of bone substitutes in the field of facial plastic and reconstructive surgery is well established. Because of the complexity of the anatomy in the head and neck region, reconstruction and augmentation of this area pose a challenge to the surgeon. In addition, the shortcomings of autogenous bone, such as resorption and donor site morbidity, have led to the need for alloplastic implants in the field of facial plastic surgery. Multiple alloplastic implants are currently in use today; however, those compounds that contain calcium, silicon, and carbon have been examined more closely in this article. This is because of their ability to osseointegrate and osseoconduct with surrounding fibro-osseous tissue, as well as demonstrate a higher immunogenic tolerance by the human body. The discussion of each compound includes a description of its composition and structure, the advantages and shortcomings of the material, and its current uses in the field of facial plastic and reconstructive surgery. With a better understanding of the available alloplastic implants, the surgeon can make a more informed decision as to which implant would be most suitable in a particular patient.

BoneSource hydroxyapatite cement: a novel biomaterial for craniofacial skeletal tissue engineering and reconstruction.

BoneSource-hydroxyapatite cement is a new self-setting calcium phosphate cement biomaterial. Its unique and innovative physical chemistry coupled with enhanced biocompatibility make it useful for craniofacial skeletal reconstruction. The general properties and clinical use guidelines are reviewed. The biomaterial and surgical applications offer insight into improved outcomes and potential new uses for hydroxyapatite cement systems.

The use of processed allograft dermal matrix for intraoral resurfacing: an alternative to split-thickness skin grafts.

BACKGROUND: The standard reconstruction of significant mucosal defects in head and neck surgery has been split-thickness skin grafting (STSG). OBJECTIVE: To examine the use of a commercially available acellular dermal matrix as an alternative to STSG to reduce the scarring and contracture inherent to meshed split-thickness autografting and avoid the additional donor site morbidity. PATIENTS AND METHODS: Twenty-nine patients with full-thickness defects of the oral cavity were included in this retrospective chart review. Candidate patients had their operative procedure performed at a tertiary care center during a 24-month period. Allograft dermal matrix, an acellular tissue-processed biomaterial, was applied to these intraoral defects. The defects were reconstructed with an acellular dermal graft matrix in the same technical fashion as with an autologous skin graft. Patients were evaluated for rate of "take," functional return time to reepithelialization, average surface area of graft, associated pain and discomfort, evidence of restrictive graft contracture, patient diagnosis, and graft location within the oral cavity. Any evidence of incomplete graft reepithelialization was considered grounds for graft failure, either complete or incomplete. Epithelialization and contracture were assessed during outpatient clinical examinations. Patient complaints with regard to discomfort at the graft bed were considered evidence of pain. RESULTS: Graft locations included 9 in the tongue (32%), 5 in the maxillary oral vestibule (17%), 4 in the mandible (14%), 4 in the floor of mouth (14%), 3 in the hard and/or soft palate (10%), 3 in the tonsil (10%), and 1 in the lip (3%). The overall rate of take was 90% with complete epithelialization noted on clinical evaluation within 4 weeks. Patients were followed up for an average of 8.6 months. The average grafted surface area was 25 cm2. Pain or discomfort was noted in 3 patients (12%). One patient (4%) was noted to have clinical evidence of graft contracture. CONCLUSIONS: Allograft dermal matrix was successful as a substitute to autologous STSG for resurfacing of intraoral defects. Allograft dermal matrix may be considered a useful reconstructive option for patients with oral mucosal defects.

Hydroxyapatite cement in craniofacial skeletal reconstruction and its effects on the developing craniofacial skeleton.

OBJECTIVE: To assess the effects of hydroxyapatite cement (HAC) on the developing feline craniofacial skeleton. DESIGN: Fronto-orbital craniotomies were performed on 14 kittens and reconstructed by autograft or HAC. By design, animals in which the craniofacial skeleton was reconstructed with HAC also underwent obliteration of the left frontal sinus. After achievement of skeletal maturity, animals were sacrificed and compared by 11 standardized cranial measurements obtained by sliding caliper. Additional analyses included histological studies, histomorphometry, and computed tomography. SUBJECTS: Twenty-one 12-week-old female cats were divided into 3 groups, composed of 7 specimens. INTERVENTION: The control animals underwent periosteal elevation alone (group 1). The remaining animals underwent unilateral fronto-orbital craniotomy and subsequent reconstruction with orthotopic bone flap replacement (group 2) or HAC (group 3). RESULTS: All animals survived the study with no evidence of wound infection or implant failure. Gross morphological studies demonstrated excellent contour reconstruction in both experimental groups. Craniometric analysis detected 1 intergroup difference that consisted of a wider skull in group 3 on the reconstructed side. An intragroup difference in orbital height was also seen in group 3. Computed tomography demonstrated a solid appearance of the implant with obliteration of the left frontal sinus in group 3. Histological studies showed that HAC was osseointegrated to native bone, with areas of new bone interspersed throughout the implants. No significant inflammatory response or fibrous encapsulation was noted. Histomorphometry demonstrated that implants were replaced by osseous tissue in 44% to 50% of the animals within 5 months. CONCLUSION: Hydroxyapatite cement is safe and effective for craniofacial reconstruction in the developing feline and may be appropriate for similar applications in humans.

Hydroxyapatite cement, a smart biomaterial for craniofacial skeletal tissue engineering.

Craniofacial skeletal surgery continues to command special interest from patients and clinicians dealing with skeletal defects. Autologous bone grafts remain the standard treatment by which bone substitutes are compared. A continued interest in avoiding donor sites and realizing "off the shelf convenience" has fostered the use of biomaterial bone substitutes. The first generation of implant materials used for cranial reconstruction were not specifically designed for biomedical applications. Methylmethacrylate was adopted for cranial applications after use in implant fixation for hip arthroplasty by Charnley, The development of this material did not employ sophisticated implant evaluation and mainly focused on standard mechanical properties demonstrated on the benchtop.

Irradiated bone and its management.

There are two undeniable attributes of radiotherapy: its value in controlling head and neck malignancies and the progressive damage it inflicts on all treated tissues. It is fortunate that over the past decade, we have developed techniques and treatments that counteract, at least in part, the negative effects of radiotherapy on bone. Some of these measures are purely preventive and must be employed before or during radiation therapy to be successful. They include limiting the total radiation dose to less than 7000 Rads, appropriately shielding structures that do not require radiation, sparing one or more major salivary glands to minimize xerostomia, limiting fraction dosages to less than 200 Rads, obtaining pre-radiation dental evaluations, and performing dental extractions before radiotherapy begins. Additionally, treatments have been devised to prevent ORN following radiotherapy. They consist of patient participation in aggressive dental maintenance programs, oral fluoride treatments, and the use of preextraction hyperbaric oxygen when unhealthy teeth need to be removed. Should radiation-induced complications develop in spite of these efforts, treatments have been developed that effectively deal with ORN, namely, hyperbaric oxygen (the Marx protocol) and prolonged courses of intravenous antibiotics. Finally, when ORN results in mandibular loss and deformity, these defects can be effectively reconstructed with either corticocancellous particulate bone grafts or microvascular osseous tissue transfers, depending on the clinical situation. Much can be done to prevent and treat radiation-induced complications involving bone, and it remains the responsibility of the head and neck surgeon to make sure that these measures are utilized. When all priorities in treating ORN are considered, differentiating a radiation-induced wound healing problem from a delayed tumor recurrence remains paramount. This differentiation should always be the first step in the treatment of any radiation-induced wound.

Indications for hydroxyapatite cement reconstruction in lateral skull base surgery.

Preliminary data on the use of hydroxyapatite cement to restore cranial bone integrity has shown excellent results. Cranial base reconstruction has been accomplished for translabyrinthine, middle cranial fossa, and suboccipital craniectomy defects, as well as extensive temporal bone fractures. Fifteen patients have been followed for up to 2 years with no evidence of complication from use of the hydroxyapatite cement. Exposure to cerebrospinal fluid does not appear to alter its stability, and pre-existing infection appears to be the only contraindication to its use. Stability of the cement has been confirmed by serial radiographic analyses. This paper reviews the chemical structure and bioactivity of hydroxyapatite cement and employs case studies to illustrate the applications of this new biomaterial in lateral skull base surgery.

Reconstruction of suboccipital craniectomy defects with hydroxyapatite cement: a preliminary report.

Hydroxyapatite cement, a new biomaterial presently under clinical investigation, has been demonstrated to have potentially wide application in cranial reconstruction. We describe our experience with this biologic bone cement in the reconstruction of suboccipital craniectomy defects in seven patients after vestibular schwannoma removal. With up to 2-year follow-up, cranial bone integrity has been reestablished in five patients. Dissolution of cement has occurred in dependent areas and appears to be technique related. Cranial bone contour appears dependent on the amount of cement used. The frequency of debilitating postoperative headache was reduced in these patients when compared to patients who had no reconstruction of the craniectomy defect. Reconstruction of the bony defect after suboccipital craniectomy with hydroxyapatite cement is not only useful to restore cranial contour, but also appears to reduce some of the functional deficits attributed to this surgical approach.

Polymeric implants in craniomaxillofacial reconstruction.

With advances in polymer chemistry, polymeric implants are becoming an increasingly attractive alternative to autogenous bone. Although polymeric implants were traditionally used to bridge bony defects and modify the overlying soft tissue envelope, new resorbable polymers may allow bony replacement and may be used as alternatives to metals in rigid fixation. This article contains an overview of polymeric implants from acrylics to modern resorbable polymers.

Synthetic bone graft substitutes.

Some of the most significant advances in biomaterials over the last 20 years have been in the field of bone graft substitutes. Additionally, bone growth proteins were one of the first tissue-specific morphogenic factors to be characterized and produced by recombinant genetic technology. Consequently, the development of a new generation of totally synthetic, biologically active bone graft substitutes is just now beginning to move from the laboratory to clinical testing. It is entirely possible that within the next 10 to 15 years, the majority of "bone grafting" in craniofacial reconstructive surgery and in orthopedic surgery may be done with biologically active synthetic bone graft substitutes rather than natural bone sources. In fact, the harvesting of autogenous grafts may eventually prove to be the exception rather than the standard of care. Regardless of whether the potential of biologically active bone graft substitutes is ever fully realized, we now have a large number of synthetic alternatives to autogenous bone grafts for craniofacial skeletal augmentation and reconstruction. The reality of these synthetic bone graft substitutes is that no single material is "the best" for all applications. Instead, the specific biomaterial must be tailored to the individual site of application to achieve optimal results. The synthetic bone graft substitutes reviewed in this article represent only the "core" of synthetic biomaterials from which synthetic bone graft substitutes can be selected. Other articles in this monograph highlight the roles that various natural and biologically active bone graft substitutes play in craniofacial skeletal augmentation and reconstruction.

General concepts in craniofacial skeletal augmentation and replacement.

Craniofacial skeletal reconstruction has reached new levels of sophistication. The ability to precisely plan and execute these instructions affords better and more predictable outcomes of surgical therapy. This article will focus on the general concepts and principles for advanced craniofacial skeletal augmentation and replacement.

Nonvascularized autogenous bone grafts for craniofacial skeletal augmentation and replacement.

Autogenous nonvascularized bone grafts play an important role in the reconstruction of complex craniomaxillofacial defects. Experimental animal data have demonstrated that grafts from membranous bone donor sites tend to undergo less resorption than grafts from endochondral donor sites, probably because of the different bony architecture of each of these types of grafts. Of all the potential donor sites, the harvest of bone graft from the calvarium is associated with the least overall morbidity. Surgeons should be aware of the biologic basis for the successful application of free autogenous bone grafts.

Metal plate and screw technology.

Fundamental to the choice and proper application of plating systems in osteosynthesis of the craniomaxillofacial skeleton is an understanding of the basic design and biomechanical characteristics that define them. Improper selection of systems and technical execution of rigid internal fixation is not uncommon and may result in hardware failure, dysfunction, and dysmorphology. The surgeon who is able to command the nuances of system design and discipline in application will achieve superior functional and aesthetic results that are predictable and reproducible.

Soft-tissue augmentation and replacement in the head and neck. General considerations.

It is clear that many of the factors that affect wound healing when natural biomaterials are used also affect the long-term success of semisynthetic and synthetic alloplasts. The development of a new generation of biomaterials that combine synthetic components with bioactive proteins are just now beginning to move from the laboratory into clinical testing. Within the next decade, biologically active growth proteins, in combination with resorbable synthetic alloplasts, may allow missing tissues to be regenerated rather than just "filled in" by permanent implants. There will also be a steady drift away from materials that show any risk of being carcinogenic or immunoreactive over time. As promising as these new alloplasts appear to be, we should learn from past experience. Implants that initially seem biocompatible can fail in unpredictable ways when exposed to the hostile environment of the body. As surgeons, we well ultimately be held responsible for the biomaterials we implant. Our selection of biomaterials should be based on sound scientific and surgical knowledge, and not solely upon the recommendations of manufacturers. The authors hope that the information in this monograph will help to integrate reconstructive options so that autologous tissues are used whenever possible and synthetic materials are appropriately selected and applied when necessary.