Critical Evaluation of the Scientific Literature Concerning Bone Graft Alternatives in Spinal Surgery and Focus on Bioceramics.

To improve solid spinal fusion while avoiding the morbidity associated with autograft harvesting procedures, numerous alternatives have been investigated, including allograft, demineralized bone matrix (DBM), cell-based therapies and growth factors (i.e., bone morphogenetic proteins, platelet concentrates), and ceramic-based biomaterials. Even though all of these approaches have the potential to improve the outcome of spinal fusion procedures, most of them have not yet been validated by evidence-based clinical results, and thus they are not strongly advisable for clinical use, in addition to being particularly expensive. Here, we give an overview of the current clinical evidence for bone graft alternatives for spine surgery procedures. We will also evaluate the pros and cons of their use and briefly review the more relevant literature.

Successful Strategies for Dealing With Infected, Custom-Made Hydroxyapatite Cranioplasty.

When a cranioplasty implant becomes infected, standard operating procedure dictates its removal and the initiation of a long course of antibiotic therapy. However, removing such a prosthesis can have a series of adverse consequences, including delayed cognitive and motor recovery, lack of brain tissue protection, unsightly deformity, and the need for two additional surgical procedures, not to mention the additional costs involved. To maintain the advantages of cranioplasty, we opted for a conservative approach (levofloxacin and rifampicin every 24 hours for 8 weeks) in a 68-year-old woman whose custom-made porous hydroxyapatite implant, fitted following aneurysm clipping, had become infected. The tissues overlying the implant were curettaged, and the patient's clinical condition, blood markers, and infection course were continuously monitored (local monitoring was performed by single-photon emission computed tomography [SPECT]/computed tomography [CT after intravenous administration of Tc-labeled antigranulocyte antibody). Blood tests and SPECT/CT evidenced a progressive reduction in phlogosis indices and infection locus, even 1 month after antibiotic therapy was commenced, and at 2 years from cranioplasty, the same tests and clinical examination were negative. At 6-year follow-up, clinical assessment revealed nothing out of the ordinary.Hence, specific cases (hydroxyapatite prosthesis, intact dura, cranial CT and magnetic resonance imaging negative for empyema, well-vascularized scalp, antibiotic-responsive bacteria) of infected cranial implant can be treated using a conservative approach consisting of appropriate antibiotic therapy, accompanied by local debridement where necessary, and assiduous monitoring of phlogosis indices and local verification via labeled-leukocyte scintigraphy. Our report, which was compiled after a long-term follow-up period, shows that this conservative procedure appears to be a viable option in cases of infected, custom-made hydroxyapatite cranioplasty, provided that some basic rules concerning clinical and instrumental standards are adhered to, as clearly stated in our report.

Cranioplasty: Review of Materials.

Cranioplasty remains a difficult procedure for all craniofacial surgeons, particularly when concerning the reconstruction of large lacunae in the skull. Considering the significant clinical and economic impact of the procedure, the search for materials and strategies to provide more comfortable and reliable surgical procedures is one of the most important challenges faced by modern craniofacial medicine.The purpose of this study was to compare the available data regarding the safety and clinical efficacy of materials and techniques currently used for the reconstruction of the skull. Accordingly, the scientific databases were searched for the following keywords autologous bone, biomaterials, cranial reconstruction, cranioplasty, hydroxyapatite, polyetheretherketone, polymethylmethacrylate, and titanium. This literature review emphasizes the benefits and weaknesses of each considered material commonly used for cranioplasty, especially in terms of infectious complications, fractures, and morphological outcomes.As regards the latter, this appears to be very similar among the different materials when custom three-dimensional modeling is used for implant development, suggesting that this criterion is strongly influenced by implant design. However, the overall infection rate can vary from 0% to 30%, apparently dependent on the type of material used, likely in virtue of the wide variation in their chemico-physical composition. Among the different materials used for cranioplasty implants, synthetics such as polyetheretherketone, polymethylmethacrylate, and titanium show a higher primary tear resistance, whereas hydroxyapatite and autologous bone display good biomimetic properties, although the latter has been ascribed a variable reabsorption rate of between 3% and 50%.In short, all cranioplasty procedures and materials have their advantages and disadvantages, and none of the currently available materials meet the criteria required for an ideal implant. Hence, the choice of cranioplasty materials is still essentially reliant on the surgeon's preference.

Spontaneous fractures in custom-made porous hydroxyapatite cranioplasty implants: is fragility the only culprit?

BACKGROUND: Although the porous hydroxyapatite (PHA) used in custom-made cranioplasty implants is a material appreciated for its biomimetic properties, before osteointegration it is initially very fragile. Nevertheless, we wondered whether this primary fragility is entirely due to brittleness or whether the surgeon's actions may influence the behavior of the material. METHODS: To study the influence of the surgeon's behavior, we made a virtual model of a custom-made PHA cranioplasty implant and submitted it to three implant procedural variables using finite element methods. In the first test, a scenario in which the surgeon's design, validation, and positioning techniques are impeccable, the edges of the implant adhered well to the craniectomy margins. In the second test, a discrepancy between a portion of the perimeter of the craniectomy and the profile of the prosthesis was modeled, and in the third test, several gaps were simulated between the implant and the craniectomy margins. RESULTS: Our mathematical model showed that when local and general discontinuities were included in the test scenarios, there was an increase in the load coming to bear on the cranioplasty implant, which amounted to 80 and 50 %, respectively. CONCLUSIONS: The fragility of custom-made PHA cranioplasty implants increases if the surgeon fails to achieve a precise design and validation, and/or an accurate surgical procedure. Nevertheless, careful attention during these phases helps to maintain the strength of the implant, given the more favorable mechanical conditions, without interfering with its biomimetic capacity.

Enhancing dermal and bone regeneration in calvarial defect surgery.

INTRODUCTION: To optimize the functional and esthetic result of cranioplasty, it is necessary to choose appropriate materials and take steps to preserve and support tissue vitality. As far as materials are concerned, custom-made porous hydroxyapatite implants are biomimetic, and therefore, provide good biological interaction and biointegration. However, before it is fully integrated, this material has relatively low mechanical resistance. Therefore, to reduce the risk of postoperative implant fracture, it would be desirable to accelerate regeneration of the tissues around and within the graft. OBJECTIVES: The objective was to determine whether integrating growth-factor-rich platelet gel or supportive dermal matrix into hydroxyapatite implant cranioplasty can accelerate bone remodeling and promote soft tissue regeneration, respectively. MATERIALS AND METHODS: The investigation was performed on cranioplasty patients fitted with hydroxyapatite cranial implants between 2004 and 2010. In 7 patients, platelet gel was applied to the bone/prosthesis interface during surgery, and in a further 5 patients, characterized by thin, hypotrophic skin coverage of the cranial lacuna, a sheet of dermal matrix was applied between the prosthesis and the overlying soft tissue. In several of the former groups, platelet gel mixed with hydroxyapatite granules was used to fill small gaps between the skull and the implant. To confirm osteointegration, cranial computed tomography (CT) scans were taken at 3-6 month intervals for 1-year, and magnetic resonance imaging (MRI) was used to confirm dermal integrity. RESULTS: Clinical examination performed a few weeks after surgery revealed good dermal regeneration, with thicker, healthier skin, apparently with a better blood supply, which was confirmed by MRI at 3-6 months. Furthermore, at 3-6 months, CT showed good biomimetism of the porous hydroxyapatite scaffold. Locations at which platelet gel and hydroxyapatite granules were used to fill gaps between the implant and skull appeared to show more rapid integration of the implant than untreated areas. Results were stable at 1-year and remain so to date in cases where follow-up is still ongoing. CONCLUSIONS: Bone remodeling time could be reduced by platelet gel application during cranioplasty with porous hydroxyapatite implants. Likewise, layering dermal matrix over such implants appears to promote dermal tissue regeneration and the oshtemo mimetic process. Both of these strategies may, therefore, reduce the likelihood of postsurgical fracture by promoting mechanical resistance.

Method to thicken the scalp in calvarian reconstruction.

BACKGROUND: Scalp reconstruction has always been a challenging task. In our case, we report the use of INTEGRA Dermal Regeneration Flap, together with a cranioplasty for complex scalp defect. We have obtained not only an appropriate coverage of the cranial bone, but also an optimal aesthetic result. METHOD: We present a 24-year-old patient with a history of severe cranial trauma with sinking of the frontal bone with dural laceration and large bilateral frontal lacerocontusive focus. First, he had undergone reconstruction with the aid of autologous bone, metallic mesh, and titanium plates at a different clinical center. He arrived to our attention with exposure of the fixation devices, as well as part of the titanium plate used for the primary reconstruction. His general conditions could not allow a complex reconstructive procedure such as microsurgical flaps. The use of INTEGRA allowed us to reach the goal of a good and appropriate reconstruction, without exposing the patient to a higher-risk procedure. After the creation of a custom-made cranial implant in porous hydroxyapatite, the patient has undergone cranial bone remodeling to reach a homogeneous contour of the forehead profile. After the positioning of the implant, a single-layer INTEGRA regeneration template has been placed between the implant itself and the hypotrophic and thinned skin layer. CONCLUSIONS: The postoperative result after 16 months allowed us to observe a normal forehead profile with a normal thickness, good skin texture, and well-hidden scars.

Septic complication following porous hydroxyapatite cranioplasty: prosthesis retention management.

After failing of autologous cranioplasty or when the bone flap is unavailable, the alloplastic (heterologous) materials are the choice for cranial reconstruction. No agreement has been reported about the material with a significant lower risk of septic complications. This is due to extremely heterogeneous prognostic factors related not only to the material used but also to the surgical procedures and/or to the timing of the procedure. More attention should be focused on the material whose characteristic could enable a delay in bacterial colonization, where an antibiotic therapy could be effective, without need of prosthesis removal. Four cases of severe septic complication following cranioplasty with porous hydroxyapatite (HA) prosthesis are presented. Patients were conservatively treated, without heterologous bone flap removal. All of our patients presented reasons for delaying HA cranioplasty removal: patients #1, 3, and 4 had an associated shunted hydrocephalus and the need for not removing the prosthesis was related to the predictable recurrence of overshunting and/or sinking skin flap syndrome. In patient #4, the revision surgery would have also damaged the microvascular flap with latissimus dorsi muscle used by plastic surgeon for skin reconstruction. In patient #2, the patient refused revision surgery. In all cases, systemic and/or radiological signs of infection were observed. In patient #2 the infective process surrounded completely the HA prosthesis, while it was located in the epidural region in patients #1 and 4. In patient #3, a surgical curettage of the infected wound was performed over the HA prosthesis. Following prosthesis retention management with antibiotic therapy, all patients revealed systemic and/or radiological signs of sepsis resolution at follow-up. The possibility to avoid a prosthesis removal with effective antibiotic treatment is mainly due to the combination of three factors: targeted antibiotic therapy, good anatomical area revascularization (resulting of an "in situ" intake of antibiotics), and the biomimetism of HA prosthesis. Further investigations in a larger number of cases need to confirm these observations.

Gamma Knife surgery in vestibular schwannomas: impact on the anterior and posterior labyrinth.

OBJECT: During the past decades, in small-to-medium size vestibular schwannomas, Gamma Knife surgery (GKS) has become a reliable therapeutic option because of either excellent local tumor control or minimal morbidity, with cranial neuropathy becoming increasingly rare. Although still insufficiently analyzed in larger cohorts of patients with long-term follow-ups, adequate chances of hearing preservation and vestibular sparing seem clinically guaranteed. However, deeper investigations are needed in this regard, expanding the number of cases and the follow-up period. METHODS: A small group of patients with vestibular schwannomas (74 patients, including 41 men and 33 women) treated between 2003 and 2009 using GKS at the authors' institution were analyzed--both before and after GKS--with computerized static stabilometry and electronystagmography for balance disorders, vertigo, and ataxia on 1 side and pure tone average, vocal speech discrimination score, auditory brainstem response, and so forth for hearing impairment and tinnitus on the other side. Eligibility criteria for this prospective study included previously untreated unilateral lesions and a Gardner-Robertson hearing class of I-III. Dosimetry plans had been programmed at the lower effective dosages for these tumors (median surface dose 12.4 Gy, range 10-13 Gy), carefully avoiding even minimal toxic dosages on the most vulnerable targets: the cochlea (never > 6 Gy) and the vestibular canals (< 7.5 Gy). RESULTS: To date, tumor growth control rates remain satisfactory; at a mean follow-up of 50 months, the rate was 96%. The overall level of hearing preservation was 72%, with 81% having Gardner-Robertson Class I hearing. Tinnitus decreased, from 52% to 28% of patients (p < 0.01). Significant improvements were also observed in vestibular symptoms, with computerized static stabilometry abnormalities decreasing from 62% to 32% (p < 0.001) and electronystagmography abnormalities reducing from 48% to 14% (p < 0.001). CONCLUSIONS: Using appropriate radiodosimetry planning, GKS seems to guarantee not only adequate tumor growth control rates, but also better levels of hearing preservation, with a documented, long-lasting improvement in vestibular functions.

Descriptive epidemiology of head injury in Romagna and Trentino. Comparison between two geographically different Italian regions.

We studied the occurrence of head injury in two different Italian regions: Romagna and Trentino. Both geographical areas attract large numbers of seasonal tourists. The study was carried out over 1 year (January 1, 1998 to December 31, 1998), prospectively in Romagna and retrospectively in Trentino because of their different head injury management protocols. The study was based on all admissions to hospital extracted by medical staff from the case records, and all cases were identified by the ICD-9 codes (ranges: 800.0-800.3, 801.0-801.3, 803.0-803.3, 850, 851.0-851.1, 852.0-852.1, 853.0-853.1, 854.0-854.1). The annual incidence of hospitalization for head injury was 314/100,000, 297 for Romagna and 332 for Trentino. The causes of head trauma and the type of injuries were similar to those reported in the international literature, and so were the characteristics of the population at risk. Romagna recorded a higher incidence of head injury among the elderly, probably due to the widespread use of bicycles without safety helmets. In Romagna, where neurosurgery departments exist, hospital mortality was low (8/100,000/year). Based on similar international literature findings, different prevention measures are suggested to reduce the occurrence and severity of head injury.