biologic diagnosis (7-9,58-60). A variety of trephine needles are available and vary predominantly in their coring diameter. Large-core biopsies can be obtained using the Craig (10-gauge, Becton Dickinson, Rutherford, NJ) and the Ackerman (12-gauge, Cook, Blooming-ton, IN) trephine needles (Fig. 4). Trephine needle systems consist of a large outer cannula with a fitted obturator, which is advanced to the bone surface. Once the obturator is removed, the trephine needle containing cutting teeth is advanced through the cannula to the bone. Using a clockwise-counterclockwise motion, the needle is advanced through the bone and a bone core is obtained. The trephine needle is withdrawn and a blunt obturator is used to remove the specimen (40).
Trephine needle systems can be used as a coaxial system for subsequent FNA and cutting needle biopsies. Once the trephine needle has traversed the cortex during a core biopsy, FNA and cutting needles can be advanced through the outer cannula into the medullary cavity through the bone biopsy defect. Serial FNA and cutting biopsies can be performed.
Newer trephine systems use a coaxial technique for initial needle placement in high-risk areas such as the upper thoracic and cervical spine (28,29,59). The Elson (Cook, Bloomington, IN) and Geremia (Cook, Bloom-ington, IN) coaxial systems use a 22-gauge needle with a removable stylet and hub to act as a coaxial guiding needle (Fig. 5). The Geremia needle is a smaller caliber (16-gauge) needle than the Elson (12-gauge) and is preferred by many interventional radiologists in the thoracic and cervical spine. After local anesthesia, the 22-gauge needle is advanced to the desired site on the bony surface (Fig. 6A). The stylet is removed and the periosteum is anesthetized through the needle with local anesthesia. Subsequently, the hub is removed and a coaxial introduction cannula is advanced over the needle to the site (Fig. 6B, C). (The Geremia system replaces the stylet with a hubless stiffing stylet prior to the coaxial cannula placement.) After removal of the 22-gauge guiding needle and inner cannula, the trephine needle is advanced through the outer cannula to the lesion (Fig. 6D, E). The coaxial placement allows the trephine needle to follow the predeter-
Fig. 4 (A) Trephine needle systems. (Ackerman needle, Cook, Bloomington, IN.) (A) Large outer cannula with a fitted obturator. (B) Trephine needle containing cutting teeth that is advanced through the cannula. (B) Close-up of Trephine needle.
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