3D Printing Technology-Assisted Precise Surgery for a Cryptic Hemangioma of Cranial Bone

Sir, The hemangiomas of cranial bone are rare lesions accounting for less than 1% of all skull tumors.[1] They are caused by vascular malformation representing localized defects in the development of the embryonic vasculature. Skull hemangioma is manifested by bulging growth in the presence of osteolytic lesions of the skull, mostly the outer plate.[2] Hemangiomas that invade inside the inter plate of cranial bone are rarely reported.[3] Such hemangiomas are dubbed cryptic hemangiomas of cranial bone due to their insidious onset and slow growth.[3] We herein present a rare case of cryptic hemangioma of cranial bone in a 53-year-old woman receiving precise surgery assisted with three-dimensional (3D) printing technology. A 53-year-old female presented with complaints of repeated dull pain with a sensation of constant pressure over the left temporal and parietal regions of the head for 1 month. She denied a significant history of previous trauma or surgery and any similar vascular lesions in her family. There was no sensory impairment in the left temporal and parietal regions. The routine brain computed tomography (CT) scan showed no significant abnormalities, except for a subtle bulge in the left temporal and parietal bones [Figure 1a]. The bone window CT scan revealed a small, smooth expansion between the inner and the outer cortical tables in the same area, which suggested the presence of a benign lesion [Figure 1b]. Preoperative examination and evaluation found no contraindication to the following surgical treatment.Figure 1: Preoperative imaging data and 3D printing process of the surgical guide. (a) Routine CT of the brain revealed a subtle bulge (a suspicious lesion) in the left temporal and parietal bones (red arrow). (b) The bone window CT scan clearly showed a small, smooth osteolytic expansion (red arrow) between the inner and the outer cortical tables. (c) The reconstructed 3D model of the patient’s face and head with MIMICS 17.0 software. (d) The 3D model of the patient’s skull tumor. (e) The body surface projection to the virtual skull tumor was simulated. The white arrow points to the outer edge of the 1-cm normal margin of the bone lesion. (f) The relationships between the head model, bone lesion, and bone flap 3D were established with MIMICS software. (g) The 3D surgical guide was modeled with skull CT data of the patient in MIMICS software before 3D printing. (h) A practicable scalp incision line for accurate exposure of the bone lesion and adequate surgical field was sketched using the 3D surgical guide. A white arrow points to the edge of the preoperative designed bone flap. 3D=three dimensional, CT=computed tomography, MIMICS=Materialise Interactive Medical Image Control SystemThe surgical guide was firstly designed and fabricated for accurate drilling and implant placement. In detail, the data of the thin-slice (thickness <5 mm) brain CT images of the patient were extracted from the Picture Archiving and Communication System in our hospital and saved as a Digital Imaging and Communications in Medicine (DICOM) format file (about 5 min). The consecutive CT data were then imported into Materialise Interactive Medical Image Control System (MIMICS) 17.0 (Materialise, Leuven, Belgium). The skull CT data in MIMICS were utilized for reconstructing the 3D model of the patient’s face and head via digital threshold selection, morphological operations, and Boolean calculations [Figure 1c]. The lesion size was calculated (approximately 1.7 cm × 0.8 cm) after reconstructing the 3D model of the skull tumor in MIMICS [Figure 1d]. Afterward, the projection of the virtual skull tumor on the body surface was simulated and the relationships between the head model, bone lesion, and bone flap in 3D were established by MIMICS [Figure 1e and f]. The design data of the 3D reference (part of the auricle and tragus)-supported surgical guide and the projection of the skull tumor on the body surface were saved as the stereolithography (STL) model file. The time from data import to 3D model construction of the surgical guide was about 20 min. After loading the STL file in the HORI 3D printer software (about 5 min), the guide template was fabricated using a 3D printer (Hongrui H2; Beijing Huitianwei Technology Co., Ltd., Beijing, China) [Figure 1g]. It took about 5 min to adjust the balance of the printing platform, preheat the nozzle of the printer, and load the printing material (polylactic acid). The fabrication time was about 4 h. The 3D guide was stably placed on the targeting region of the patient’s head to sketch a practicable scalp incision line for accurate exposure of the bone lesion [Figure 1h]. The guide was used before surgery and required no specific disinfection. After general anesthesia and proper scalp incision [Figure 2a], the bone lesion, a bluish-purple lesion of about 2 cm × 2 cm in size, was exposed and approximately located at the central part of the surgical field [Figure 2b]. The outer surface of the skull was frictionless. After drilling a hole behind the temporal bone and at 1 cm apart from the edge of the visually exposed lesion, a bone flap containing the hemangioma was milled with a 1-cm peripheral excision margin and lifted off. The dura was intact without obvious tumor infiltration [Figure 2c]. The excised bone flap was about 3 cm × 3 cm in size [Figure 2d]. The new bone defect was repaired with a customized titanium mesh. The cut was closed by traditional layer-by-layer suturing in the absence of any bleeding. The excised bone flap received hematoxylin–eosin staining.Figure 2: Presentation of the surgery. (a) Design of preparation of the surgical site. A white arrow points to the edge of the designed bone flap. (b) The skull hemangioma (red arrow), a bluish-purple lesion of about 2 cm × 2 cm in size, was located at the center of the exposed surgical site. (c) The bone window of about 3 cm × 3 cm in size was exposed after en bloc resection. (d) The gross appearance of the excised bone lesionThe patient’s headache improved after the surgery. The postoperative histopathology supported the diagnosis of an intraosseous hemangioma [Figure 3a–c]. The skull CT confirmed complete resection of the skull hemangioma and firm fixation of the titanium mesh on the skull [Figure 3d]. There was no obvious epidural accumulation of blood and fluid. The patient was discharged on postoperative day 5 owing to the satisfactory surgical incision healing and physical condition. On postoperative day 12, the patient’s headache was significantly mitigated, and the sutures were removed. Besides, there was no subcutaneous effusion based on palpation. No evident headache, subcutaneous effusion, or titanium mesh rejection was reported at the 3-month follow-up.Figure 3: ×40 (a), ×100 (b), and × 400 (c) original magnifications of the hematoxylin–eosin-stained specimen. The postoperative histopathology supported the diagnosis of hemangioma of cranial bone. (d) After excising the skull hemangioma and the titanium mesh (black arrow) for repairing the bone window, the notch is displayed under the CT skull window. CT = computed tomographyThe hemangiomas of cranial bone often manifest in brain CT as a high-density, thin, peripheral sclerotic rim of the lesion and a characteristic honeycomb-like trabeculated appearance at its center.[4,5] The head CT bone window can reveal the degree of damage and visualize the relationship between the lesions and the inner and outer plates of the skull. In the histopathologic view, these intraosseous benign tumors are essentially vascular malformations, and capillary or cavernous hemangiomas are formed according to the size of vascular spaces.[6,7] Cryptic hemangiomas of cranial bone are prone to compression, and they invade the intradural brain tissue and cause intracranial hemorrhage.[6] Patients with such conditions should receive surgical treatment at the earliest possible time. The cryptic hemangiomas consist of multiple dilated vascular channels separated by fibrous septa. Such bone tumors should be removed along with about 0.5 cm of normal bone margin en bloc to reduce intraoperative bleeding and postoperative recurrence.[6-8] Blood arteries should be partially embolized before surgery for large-size skull hemangiomas to prevent uncontrollable hemorrhage. Removal of the involved dura mater and subsequent repair of the dura mater are also required. The cryptic hemangiomas often invade the cranial inner plate and sometimes appear with a small invasion in the outer plate and scalp. Obvious surface markings are hardly seen in this condition. With the traditional electrode positioning technique, the surgeons need to construct a 3D model based on the two-dimensional (2D) images of the head CT in their mind by their own experience. In our case, there was a big deviation between the electrode positioning technique and the 3D-printed surgical guide in positioning the lesion center. More CT scans are required for more precise positioning of the lesion center with the electrode positioning technique, which increases the medical costs and exposure to radiation. Displacement or falling off of the electrodes by accident brings more trouble to a second precise positioning. 3D printing technology has been applied in the reduction of complicated pelvic fractures and orthopedic practices for facial or spinal deformities.[8-10] Its application in skull repair, fabrication of aneurysm clamps, and minimally invasive puncture treatment for skull base tumors and cerebral hematomas has received positive feedback.[9,10] In our case, this technology provided virtual-reality surgical simulation and precise location of targeting lesions; the patient received a personalized precise minimally invasive surgery, with less gratuitous exposure and tissue damage. Besides, the well-matched 3D-printed guide is affordable and operable in the surgical treatment of such hemangiomas. In conclusion, surgical treatment of cryptic hemangiomas of cranial bone with the aid of 3D printing is worth clinical promotion in primary medical institutions without navigation equipment. Declaration of patient consent The authors certify that they have obtained an appropriate consent form from the patient. In the form, the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understands that her name and initials will not be published and due efforts will be made to conceal her identity, but anonymity cannot be guaranteed. Financial support and sponsorship Dazhou Science and Technology Program of Sichuan Province of China (19YYC0017) provided the financial support. Conflicts of interest There are no conflicts of interest.