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.

Cerebrospinal fluid (CSF) flow abnormalities are known to be present in Chiari I malformation and to underlie the origin and progression of associated syringomyelia. The incidence of syrinx formation, however, is variable for unknown reasons. The aim of this study was to investigate whether differences in CSF flow dynamics in patients with Chiari I malformation may account for the different clinical and radiological presentation. Presurgical and postsurgical phase-contrast magnetic resonance imaging investigations were prospectively conducted in 47 adult patients with symptomatic Chiari I malformation. Patients were divided into two groups according to the presence (32 cases) or absence (15 cases) of syrinx. Cerebrospinal fluid flow patterns were evaluated at four regions of interest: prebulbar cistern, foramen magnum, and the ventral and dorsal spinal subarachnoid spaces at the C-5 level. A temporal analysis of CSF flow waveforms was performed with measurement of cranial- and caudal-directed flow durations. All patients underwent a craniocervical decompressive procedure. Preoperatively, a prolonged caudal-directed (systolic) flow pattern was observed in patients with syringomyelia, as compared with normal control values obtained in 15 healthy volunteers. Conversely, a decreased systolic duration was observed in Chiari I patients who had malformation without syrinx. These trends were not statistically significant because of the considerable degree of overlap with the control values recorded in both groups. Additional comparison of the observed preoperative values obtained in patients with and those without syringomyelia indicated that the difference in systolic flow duration was significant at the ventral spinal subarachnoid space level (p = 0.003) and remarkable at the other levels, although not reaching statistical significance. Cerebrospinal fluid flow was minimal or absent at the foramen magnum (dorsal aspect) due to tonsillar herniation, precluding reliable quantitative measurement at this level. There was no evidence of communication between the fourth ventricle and syrinx in any case. Postoperatively, unobstructed CSF flow was recorded across the enlarged foramen magnum and into the artificial cisterna magna in all patients. A gradual restoration of near-normal flow patterns was observed in both groups. Inside the syrinx, fluid motion gradually tapered, no longer being detectable in 12 patients (37.5%) 1 year postsurgery. In patients with Chiari I malformation and associated syringomyelia different CSF flow patterns were demonstrated as compared with patients in whom syrinx was absent. Analysis of this study's findings supports the hypothesis that in Chiari I malformation an elongated systolic flow may prolong the condition of increased spinal subarachnoid pressure caused by the junctional obstruction, thus favoring CSF penetration into the spinal cord. It may be also proposed that a shortened systolic flow may be insufficient to maintain a hypertensive condition for enough time to induce syrinx formation.

A large number of interspinous process devices (IPD) have been recently introduced to the lumbar spine market as an alternative to conventional decompressive surgery in managing symptomatic lumbar spinal pathology, especially in the older population. Despite the fact that they are composed of a wide range of different materials including titanium, polyetheretherketone, and elastomeric compounds, the aim of these devices is to unload spine, restoring foraminal height, and stabilize the spine by distracting the spinous processes. Although the initial reports represented the IPD as a safe, effective, and minimally invasive surgical alternative for relief of neurological symptoms in patients with low back degenerative diseases, recent studies have demonstrated less impressive clinical results and higher rate of failure than initially reported. The purpose of this paper is to provide a comprehensive overview on interspinous implants, their mechanisms of action, safety, cost, and effectiveness in the treatment of lumbar stenosis and degenerative disc diseases.

OBJECT: Spacers placed between the lumbar spinous processes represent a promising surgical treatment alternative for a variety of spinal pathologies. They provide an unloading distractive force to the stenotic motion segment, restoring foraminal height, and have the potential to relieve symptoms of degenerative disc disease. The authors performed a retrospective, multicenter nonrandomized study consisting of 1108 patients to evaluate implant survival and failure modes after the implantation of 8 different interspinous process devices (IPDs). METHODS: The medical records of patients who had undergone placement of an IPD were retrospectively evaluated, and demographic information, diagnosis, and preoperative pain levels were recorded. Preoperative and postoperative clinical assessments in the patients were based on the visual analog scale. A minimum of 3 years after IPD placement, information on long-term outcomes was obtained from additional follow-up or from patient medical and radiological records. RESULTS: One thousand one hundred eight patients affected by symptomatic 1- or 2-level segmental lumbar spine degenerative disease underwent placement of an IPD. The complication rate was 7.8%. There were 27 fractures of the spinous process and 23 dura mater tears with CSF leakage. The ultimate failure rate requiring additional surgery was 9.6%. The reasons for revision, which always involved removal of the original implant, were acute worsening of low-back pain or lack of improvement (45 cases), recurrence of symptoms after an initial good outcome (42 cases), and implant dislocation (20 cases). CONCLUSIONS: The IPD is not a substitute for a more invasive 3-column fusion procedure in cases of major instability and spondylolisthesis. Overdistraction, poor bone density, and poor patient selection may all be factors in the development of complications. Preoperatively, careful attention should be paid to bone density, appropriate implant size, and optimal patient selection.

OBJECTIVE. Damage to the facial nerve during surgery in the cerebellopontine angle is indicated by A-trains, a specific electromyogram pattern. These A-