William B Morrison

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Department of Radiology, Thomas Jefferson University Hospital, Philadelphia, Pennsylvania, U.S.A.

INTRODUCTION

Needle localization, predominantly using hookwire needles, has been used for preoperative localization of breast lesions and pulmonary nodules (1-6). This technique is advantageous because the needle can be precisely positioned using imaging guidance. The hook at the end of the wire (Fig. 1) immobilizes it so that the patient can be transported to the surgical suite for excision of the lesion. This technique is also useful for musculoskeletal lesions (7). In this chapter, we will describe the technique, review previously reported musculoskeletal applications for this procedure, and discuss potential indications.

TECHNIQUE

Although needle localization of musculoskeletal lesions has been reported using only computed tomography (CT ) guidance, which is the method discussed here, the technique should be applicable using whatever modality best visualizes the lesion. If ultrasound or magnetic resonance imaging (MRI ) is chosen, specialized needles are commercially available to facilitate visualization. As with any biopsy, but particularly in this situation, consultation with the surgeon is essential to determine the optimal skin entry site that will be used for the surgical approach.

Using CT, the patient is initially scanned with 5 to 10 mm sections through the area of the lesion. Marker needles are placed on the skin, and repeat 3 mm sections are acquired at the level of the lesion (Fig. 2A) in order to plan the skin entry site and to measure the distance and angu-lation from the lesion to this point. The skin entry site is marked with an indelible marker, and this site and surrounding area is widely prepped. The hookwire needle selected is of a length determined by the depth required to reach the lesion, with an additional 5 to 10 cm external to the skin margin. Local anesthetic is administered subcutaneously. The hookwire (with the hook covered by the needle sheath) is then advanced (Fig. 2B) to the desired location next to or within the lesion based on the angle and depth determined using the preliminary scan. Repeat 3 mm CT sections through the area (Fig. 2C) document needle positioning. At this point, the needle can be repositioned if necessary. Once optimal positioning is confirmed, the hook is deployed by pulling back the sheath of the needle while holding the inner wire in place (Fig. 2D). Follow-up CT confirms final placement and serves as a surgical guide. The wire extending from the skin is coiled loosely and packed in sterile fashion with gauze and tape (Fig. 2E). The patient is then transferred to the surgical suite for excision of the lesion.

INDICATIONS Osseous Lesions

Preoperative wire localization of osteoid osteoma has been described (8,9). However, these lesions can be ablated percutaneously with image guidance (10), making surgery less likely to be needed. Similarly, the majority of osseous lesions can be safely and effectively accessed and biopsied per-cutaneously using image guidance. Despite these developments, there may be situations in which operative excision is preferred. These include lesions subject to insufficient sampling via the percutaneous route, such as lesions with varying aggressiveness in different areas, such as chondroid or lipomatous lesions, or lesions suspected to be such that preservation of tissue architecture is

FIGURE 1 Hookwire needle with tip deployed.

required to make the diagnosis. In these settings, preoperative localization could be useful to mark a small lesion or to mark an area within a lesion suspected of having more aggressive characteristics. Other osseous lesions can be difficult or unsafe to sample using a percutaneous route, such as highly vascular lesions in noncompressible areas or sclerotic rib lesions. In particular, lesions in small or rounded bones, especially those near vital structures may prompt surgical rather than percutaneous management. Uncooperative or combative patients may also be easier to manage using needle localization. Finally, the preference of the surgeon, the patient, or the patient's family may drive the decision to perform surgery rather than percutaneous biopsy or ablation. The last category includes pediatric patients with tumors (11).

Soft-Tissue Lesions

Soft-tissue lesions may also be referred for preoperative localization. Again, the preference of the referring physician may drive the management decision. Nevertheless, the technique should be considered for some soft-tissue lesions. These include hard lesions within the soft tissues (such as a calcified mass) that would merely be deflected away from a biopsy needle, or lesions precariously close to vital structures that would be more safely approached surgically. Also, in patients with distorted anatomy or scar tissue surrounding the area of interest, a localizer needle can provide the surgeon with a helpful guide. In these situations, CT-guided hookwire needle localization of the lesion before surgical biopsy may be the best option for the patient.

RISKS/LIMITATIONS

Some issues and limitations regarding this technique should be recognized and discussed with the patient. First, the lesion must be readily visualized on the modality used for localization. For example, a rib lesion may be obvious on MRI, but have only subtle findings on CT; this coupled with rib motion during respiration as well as volume averaging effects from the oblique course of the ribs may complicate correct localization of the lesion. Localization of the wrong rib is a potential complication. However, this technique offers an improved chance of localizing a subtle rib lesion compared to blind surgical exploration.

Second, despite the hook at the tip of the wire, it is possible for the wire to migrate farther into the tissue or to be pulled out. When localizing an osseous lesion, the needle tip should be positioned such that it is abutting against the bone, preventing migration. When localizing lesions of bone with this technique, migration should theoretically be much less likely than in localization procedures involving loose soft tissues such as the breast or lung. In rare situations in which the needle tip must be positioned within or next to a lesion in the soft tissues of the musculoskeletal system, again, planning is necessary to assure that the needle course would not endanger any sensitive structures if it were to unintentionally advance. Also, after placement, the wire protruding from the skin can be bent with a hemostat, so that it lies flush against the skin and cannot advance further. In our experience there has been no migration of the needle after placement. After proper positioning of the wire and deployment of the hook, it should be carefully coiled and packed loosely on the skin to prevent dislodgement.

FIGURE 2 Technique for placement and deployment of a hookwire needle. (A) Scout axial computed tomography (CT) image showing a small, sclerotic lesion (arrow) in the sixth rib laterally (later proven to represent metastatic adenocarcinoma). Preprocedure images are used to plan the skin entry site as well as the angle and depth to the lesion from that point. (B) The skin entry site is marked; the surrounding area is prepped and draped. Hookwire needle (with the hook retracted) is positioned at the planned angle and depth. (C) Repeat CT verifies optimal placement of needle tip (arrow) against lesion. (D) Hookwire is deployed by holding the inner wire in place while withdrawing the outer needle (motion of hands indicated by arrows). (E) After repeat CT documents final location, wire protruding from skin is loosely packed in sterile fashion.

FIGURE 2 Technique for placement and deployment of a hookwire needle. (A) Scout axial computed tomography (CT) image showing a small, sclerotic lesion (arrow) in the sixth rib laterally (later proven to represent metastatic adenocarcinoma). Preprocedure images are used to plan the skin entry site as well as the angle and depth to the lesion from that point. (B) The skin entry site is marked; the surrounding area is prepped and draped. Hookwire needle (with the hook retracted) is positioned at the planned angle and depth. (C) Repeat CT verifies optimal placement of needle tip (arrow) against lesion. (D) Hookwire is deployed by holding the inner wire in place while withdrawing the outer needle (motion of hands indicated by arrows). (E) After repeat CT documents final location, wire protruding from skin is loosely packed in sterile fashion.

Surgical complications such as wire transection or loss are minimized by effective communication with the referring surgeon. The surgeon should be made aware of the type of needle used, and the length, and precise location of the needle course, tip, and hook relative to adjacent structures. We routinely print a sheet of images of the procedure including that of the final needle placement, which we send to the operating room along with the patient. Surgeons ordering this procedure are generally experienced at using hookwire localization of other organ systems; however, the radiologist performing the localization should discuss the technique with the surgeon to assure that the surgeon is familiar with the procedure.

SUMMARY

The vast majority of musculoskeletal lesions can be biopsied or ablated using image-guided percutaneous techniques. However, this technique may rarely be excessively difficult or may subject the patient to unacceptably high risk-to-benefit ratio. These situations are likely to include combinations of the following factors: small lesion size, lesions in small or curved bones (e.g., rib lesions); lesions with overlying sclerotic bone or thick cortex, with no soft-tissue extension or access to a drill; lesions close to vital structures; heterogeneous lesions subject to errors in sampling (e.g., chondroid lesions); hard (e.g., calcified) lesions in soft tissue, which would be pushed away by the biopsy needle; and lesions with significant bleeding risk (e.g., vascular lesions in noncompressible areas). Other lesions already planned for open surgical biopsy carry greater risk or less chance for success because of small lesion size, contiguity with major blood vessels or nerves, and surrounding scar tissue or distorted anatomy; in these situations, preop-erative hookwire needle localization of the lesion can provide a reliable guide for the surgeon. This could potentially decrease operative morbidity and increase success rate of obtaining a diagnostic sample. Regarding the risk of complications, a general rule is that preoperative needle localization procedures should not be considered any less involved than percutaneous biopsies; the same preprocedure evaluation and preparation is essential.

REFERENCES

1. Kopans DB, DeLuca S. A modified needle-hookwire technique to simplify preoperative localization of occult breast lesions. Radiology 1980; 134:781.

2. Meyer JE, Kopans DB. Preoperative roentgenographically guided percutaneous localization of occult breast lesions: three-year experience with 180 patients and description of a method. Arch Surg 1982; 117:65-68.

3. Shah RM, Spirn PW, Salazar AM, et al. Localization of peripheral pulmonary nodules for thoraco-scopic excision: value of CT-guided wire placement. AJR 1993; 161:279-283.

4. Kanazawa S, Ando A, Yasui K, et al. Localization of pulmonary nodules for thoracoscopic resection: experience with a system using a short hookwire and suture. AJR 1998; 170:332-334.

5. Sawhney R, McCowin MJ, Wall SD, Block MI. Fluoroscopically guided placement of the Kopans hookwire for lung nodule localization prior to thoracoscopic wedge resection. J Vasc Interv Radiol 1999; 10:1133-1134.

6. Thaete FL, Peterson MS, Plunkett MB, Ferson PF, Keenan RJ, Landreneau RJ. Computed tomography-guided wire localization of pulmonary lesions before thoracoscopic resection: results in 101 cases. J Thoracic Imaging 1999; 14:90-98.

7. Morrison WB, Sanders TG, Parsons TW, Penrod BJ. Preoperative CT-guided hookwire needle localization of musculoskeletal lesions. AJR 2001; 176:1531-1533.

8. Steinberg GG, Coumas JM, Breen T. Preoperative localization of osteoid osteoma: a new technique that uses CT. AJR 1990; 155:883-885.

9. Magre GR, Menendez LR. Preoperative CT localization and marking of osteoid osteoma: description of a new technique. J Comput Assist Tomogr 1996; 20:526-529.

10. Rosenthal DI, Springfield DS, Gebhardt MC, Rosenberg AE, Mankin HJ. Osteoid osteoma: percutaneous radiofrequency ablation. Radiology 1995; 197:451-454.

11. Hardaway BW, Hoffer FA, Rao BN. Needle localization of small pediatric tumors for surgical biopsy. Pediatr Radiol 2000; 30:318-322.

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