Computer-aided design for three-dimensional titanium mesh used for repairing skull base bone defect in pediatric neurofibromatosis type 1. A novel approach combining biomodeling and neuronavigation.

BACKGROUND: Sphenoid dysplasia is a distinctive but uncommon manifestation of neurofibromatosis type 1. The absence of the sphenoid greater wing allows the temporal lobe to prolapse into the orbit resulting in temporal base encephalocele and pulsating exophthalmos. Surgical procedures are aimed at preserving vision and improving ocular movement and cosmesis. This defect can be closed using bone grafts or titanium mesh. However, the results of this procedure are often unsustainable due to bone graft resorption and graft displacement. METHODS: In this report, we describe a novel surgical technique, combining computer-aided design, stereolithography and neuronavigation to repair a temporal base skull defect in a 16-year-old female patient with neurofibromatosis type 1. A three-dimensional model of the skull base defect and a template for graft were first constructed according to the image data, then transferred to a real-size stereolithographic biomodel using a rapid prototyping technique. RESULTS: The final graft of titanium mesh, which was intraoperatively fabricated based on the biomodel, was precisely orientated and securely fixed to the surrounding bone under frameless navigation. Long-term follow-up result proved this repair to be effective and durable. CONCLUSION: The approach combining computer-aided design, stereolithography and surgical navigation could help managing the complex lesions in the skull base and craniofacial area requiring rigid reconstruction.

Cadaveric study of sonographically assisted percutaneous release of the A1 pulley.

The purpose of this study was to assess the value of using intraoperative sonography to assist percutaneous release of the A1 pulley in cadavers. By detailed sonographic examination and anatomical exploration, the authors determined the correlation of the actual A1 and A2 pulleys (and adjacent neurovascular bundles not visualized by sonography) to the clearly visualized flexor tendons and the metacarpophalangeal joint. The authors also evaluated their effectiveness as landmarks and the effectiveness of real-time sonographic monitoring during percutaneous release. Experiments were performed on 80 fingers and 20 thumbs in 10 cadavers. All digits were sonographically examined. The clearly delineated bony landmarks of the metacarpophalangeal joint were measured and marked. The A1 and A2 pulleys and the neurovascular bundles were surgically exposed, and their relation to the markers made during sonographic examination was measured. Using these parameters, sonographically assisted percutaneous release of the A1 pulley with a custom-made hook knife was performed on the contralateral side. The completeness of the A1 release and the potential risk of injuries to the A2, flexor tendon, and neurovascular bundles in each digit were examined. Results showed good correlation between the actual length of the A1 pulleys and the sonographically determined distance between the bony prominences of the metacarpophalangeal joint in all digits. Release was complete in 48 of the 50 digits (96 percent) and partial in two, with no injuries to neurovascular bundles. Sonography can clearly delineate the flexor tendon and underlying bony boundary of the metacarpophalangeal joint, which is useful in directing the percutaneous release of the A1 pulley. Sonography can also provide real-time intraoperative monitoring. The results using this new release technique were adequate. The method is safe and its clinical application should be encouraged.