Computer-assisted surgery for reconstruction of complex mandibular defects using osteomyocutaneous microvascular fibular free flaps: Use of a skin paddle-outlining guide for soft-tissue reconstruction. A technical report.

INTRODUCTION: We present our pre-operative virtual planning of complex mandibular reconstruction with a microvascular fibular composite free flap and its harvesting using our novel cutaneous positioning guide based on the perforator vessels for our soft tissue reconstructive surgery. TECHNICAL REPORT: We applied our protocol to 42 consecutive patients needing mandibular composite reconstruction. All patients were preoperatively studied with a CTA scan to evaluate the fibular pattern of vascularization and the perforator vessels three-dimensional path and position. Computer assisted surgery (CAS) was performed: a skin paddle outlining guide (SPOG) was designed to reproduce the shape and area of the planned soft tissue resection. CTA measurements and in vivo findings were compared. After performing the CTA, we classified the viable perforators in High Perforators, Medium Perforators and Low Perforators. The average diameter of the perforator vessels was 3 mm. The average difference between the measurements performed on the CTA and the intra-operative measures was 1, 4 mm. The SPOG was based on calf proximal and distal diameters. The anatomical fitting of the guide was obtained thanks to two customized flanges that embrace circumferentially the proximal and distal portions of the leg. The SPOG encompassed appropriate skin/leg regions, allowing the surgeon to localise the required perforator vessel. CONCLUSIONS: CTA protocol appears to be a valuable approach to asses and virtually simulate composite mandibular reconstructions. The SPOG seems to be a valuable tool to reproduce intra-operatively the planned soft tissue area to be reconstructed.

Navigation-guided resection of maxillary tumors: Can a new volumetric virtual planning method improve outcomes in terms of control of resection margins?

INTRODUCTION: In the present study, our aim was to confirm the role of navigation-guided surgery in reducing the percentage of positive margins in advanced malignant pathologies of the mid-face, by introducing a new volumetric virtual planning method for resection. MATERIALS AND METHODS: Twenty-eight patients were included in this study. Eighteen patients requiring surgery to treat malignant midface tumors were prospectively selected and stratified into two different study groups. Patients enrolled in the Reference Points Resection group (RPR - 10 patients) underwent resection planning using the anatomical landmarks on CT scan; patients enrolled in the Volume Resection group (VR - 8 patients) underwent resection using the new volumetric virtual planning method. The remaining 10 patients (Control group) were treated without the use of a navigation system. RESULTS: In total, 127 margins were pathologically assessed in the RPR group, 75 in the VR group, and 85 in the control group. In the control group, 16% of the margins were positive, while in the RPR group the value was 9%, and in the VR group 1%. CONCLUSIONS: The volumetric tumor resection planning associated to the navigation-guide resection appeared to be an improvement in terms of control of surgical margins in advanced tumors involving the mid-face.

Osteomyocutaneous fibular flap harvesting: Computer-assisted planning of perforator vessels using Computed Tomographic Angiography scan and cutting guide.

INTRODUCTION: Mandibular reconstruction performed after virtual planning has become more common during recent years. The gold standard for extensive mandibular reconstruction is of course a fibular free flap. In designing an osteomyocutaneous fibula flap, poor planning, aberrant anatomy and/or inadequate perforator vessels are the most frequent causes of complications and may force the surgeon to modify the flap design, explore the contralateral leg or harvest an additional microvascular flap. The goal of our study was to pre-operatively evaluate the vascular anatomy of the fibula and localize the cutaneous perforator vessels, so to create the fibular cutting guide based on the position of the cutaneous perforator and safely harvest the reconstructive flap. MATERIALS AND METHODS: Twenty consecutive patients who were candidates for mandibular reconstruction using a fibular microvascular free flap were enrolled in this study between January 2016 and August 2016. The patients were preoperatively assessed with a Computed Tomographic scan of head and neck and with a Computed Tomographic Angiography (CTA) scan of the lower limbs to evaluate the vascular anatomy of the fibula. Virtual planning was carried out for all patients. The fibular cutting guide was based on the position of the perforator cutaneous vessels, which were used to harvest the cutaneous part of the flap. Preoperative CT measurements were performed in order to identify the cutaneous perforators on the patients' skin. Intraoperative checking was performed to evaluate the accuracy of the perforators' position and the reproducibility of the virtual planning. RESULTS: In 5 patients out of 20 (25%), anatomical anomalies were discovered, without clinical evidence. The perforator vessels were localized in all patients. The average difference between the CTA and the intraoperative perforator localization was 1 mm (range 0-2 mm). Fibular cutting guide was positioned and fitted the anatomy of the patients in all treated patients. This allowed us to perform the planned segmentation of the fibula, obtaining the correct number of segments. In all cases, flap insetting was carried out and skin paddle was positioned as preoperatively planned. Neither donor site complications nor flap complications occurred. CONCLUSIONS: Preoperative evaluation of the legs using CTA, in patients who undergo an osteomyocutaneous fibular free flap for mandibular reconstruction, is a valuable approach to reduce altered-anatomy related complications and to improve the accuracy and outcomes of the reconstruction, especially in reconstructions of complex defects. In these cases, a soft tissue-based cutting guide can be planned based on the perforator vessels of the skin paddle, minimizing the harvesting risks of vascular lesions. Further studies and longer follow-ups are needed to evaluate the long-term outcomes and advantages of this procedure.

Relationship between multidetector CT imaging of the vestibular aqueduct and inner ear pathologies.

This study investigated the relationships between morphological changes in the vestibular aqueduct (VA) in different inner ear pathologies. Eighty-eight patients (34 males and 54 females, ranging from seven to 88 years of age; average age 49.2 years) with cochleovestibular disorders underwent temporal bone CT (with a 64-channel helical CT system according to temporal bone protocol parameters; 0.6 mm slice thickness, 0.6 mm collimation, bone reconstruction algorithm). All patients with cochleovestibular disorders who underwent temporal bone CT had been previously divided into six different suspected clinical classes: A) suspected pathology of the third window; B) suspected retrocochlear hearing loss; C) defined Ménière's disease; D) labyrinth lithiasis; E) recurrent vertigo. On CT images we analyzed the length, width and morphology of the VA, contact between the VA and the jugular bulb (JB), the thickness of the osseous capsule covering the semicircular canals, the pneumatization rate of the temporal bone and the diameter of the internal auditory canal. At the end of the diagnostic work-up all patients were grouped into six pathological classes, represented as follow: 1) benign paroxysmal positional vertigo (BPPV), 2) recurrent vertigo (RV), 3) enlarged vestibular aqueduct syndrome (EVAS), 4) sudden or progressive unilateral sensorineural hearing loss (SNHL), 5) superior semicircular canal dehiscence syndrome (SSCD), 6) recurrent vestibulocochlear symptoms in Ménière's disease. We evaluated 176 temporal bones in 88 patients. The VA was clearly visualized in 166/176 temporal bones; in ten ears the VA was not visualized. In 14 ears (11 patients, in three of whom bilaterally) we found an enlarged VA while in 31 ears the VA was significantly narrower. In 16 ears a dehiscence of the JB with the vestibular or cochlear aqueduct was noted. In all six patients with suspected EVAS we found a AV wider than 1.5 mm on CT scans; moreover CT identified four patients with large VA and ill-defined clinical symptoms. Most patients with BPPV (11 patients, Class 1) we did not find any VA abnormalities on CT scans, confirming the clinical diagnosis in ten patients; in the remaining patients we found an enlarged VA, not clinically suspected. In the RV class (eight patients, Class 2) we found three patients with negative CT scans, two patients with narrow aqueduct and subsequently reclassified as Ménière's disease patients, and three patients with ectasic JB dehiscence with the VA. In patients suffering from SNHL we found no statistically significant correlation with the morphological abnormalities. The clinical suspicion of SSCD was confirmed by CT in 11/13 patients (84.6 %); in addition another seven patients showed a thinning or dehiscence of the superior semicircular canals as the prevailing alteration on CT scans, and were reclassified in this group. Ménière's disease symptoms were correlated with a VA alteration in more than half of the cases; the most striking finding in this class was that the VA was significantly narrower (21 patients). Our study demonstrates that alterations of the VA morphology are not only related to EVAS but are also found in other inner ear pathologies such as Ménière's disease. Furthermore, MDCT may confirm the presence of correlations between the morphology of inner ear structures such as VA, semicircular canals or JB dehiscence, and alterations of vestibulocochlear function.

Could vestibular evoked myogenic potentials (VEMPs) also be useful in the diagnosis of perilymphatic fistula?

The role of vestibular evoked myogenic potentials (VEMPs) is at this time indisputable in the study of vestibular disorders. Furthermore, VEMPs are widely accepted as a diagnostic tool when a superior semicircular canal dehiscence (SCD) is suspected, presenting in such cases a lowering of threshold values able to raise a recordable response due to increased inner ear immittance. According to the same principle, the possibility of another kind of alteration having the same effect on the inner ear might be considered when high-resolution computed tomography has excluded the presence of an SCD. In this paper four cases are described in which high-resolution computed tomography showed normal features without any labyrinthine dehiscence and VEMP threshold values were lowered; the appropriateness of suspecting a perilymphatic fistula in such cases and resorting to VEMPs in detecting a perilymphatic fistula is discussed.

Superior semicircular canal dehiscence: a series of 13 cases.

Increasingly more detailed imaging techniques have recently highlighted the frequent occurrence of bony labyrinthine dehiscence. Among them, superior canal dehiscence (SCD) has been described in a number of cases presenting different features. Here, we report a series of 13 cases, in which the detection of vestibular evoked myogenic potentials (VEMPs) in response to stimuli of abnormally low intensity as compared to normal responses led us to suspect the presence of a 'third window effect'. An accurate HRCT investigation allowed the diagnosis of SCD. Anamnestic and symptomatologic differences seem difficult to explain, although in our opinion a dural rupture could be at the basis of the onset of pathologic manifestations after many years of silence of a probably malformative condition.