For suspected musculoskeletal malignancies, an adequate biopsy is critical for appropriate treatment. Although open surgical biopsy has historically been considered the optimal method of soft-tissue and bone tumor biopsy, currently needle biopsy has proven to be an adequate method for biopsy, and is generally the primary method of biopsy in most centers.1–4 Recent literature has demonstrated an accuracy of 93-95% for needle biopsies, even in deep-seated tumors.2,5 However, there remains concern regarding the drawbacks of needle biopsy: (1) this procedure inherently yields a smaller sample of tissue compared to surgical biopsy, and (2) the possibility of damage to nearby neurovascular bundles, joints, or critical structures exists.6
Different needles may have varying ability to produce the desired biopsy. Various characteristics of the needle tip may influence the quality of the tissue obtained for histologic interpretation. Theoretically, a dynamic steerable needle with variable curve capability could potentially improve biopsy precision and minimize the risks of needle biopsy. For instance, a steerable needle with an operator-controlled variable curve could allow for adjustments around obstacles. Potential indications for such a steerable needle could include biopsy of deep-seated tumors and tumors near critical neural and vascular structures. Furthermore, a steerable needle may demonstrate utility in heterogenous tumors or high-grade tumors with areas of necrosis by allowing more precise access to tissues from a specific region of the tumor, thereby potentially avoiding suboptimal or nondiagnostic biopsy samples.
Regardless of needle type, however, needle biopsy presents several advantages over an open biopsy. For example, the majority can be performed as an outpatient procedure, avoiding the inherent time and costs of the operating room and hospitalization.2,7 Furthermore, needle biopsy significantly reduces patient discomfort, rates of complications, as well as rates of altered treatment and outcomes; this includes, but is not limited to, infection, hematoma, wound breakdown, pathologic fractures, and amputations directly attributable to problems resulting from the biopsy.5,8,9 Finally, current data suggest that needle biopsies are not associated with seeding of the needle track with the tumor, making this a safer biopsy method than a poorly performed surgical biopsy.6
To minimize the pitfalls of this procedure, the technical aspects of the procedure must be optimized. One important factor that can be optimized is the needle type. Biopsy needles from major manufacturers have different configurations designed to facilitate sample acquisition or to obtain a high-quality specimen. The ideal needle would provide the highest diagnostic yield and accuracy in the safest manner and be simple and easy to use. Needle types included Chiba (steep bevel; Halyard Health, Roswell, GA); Franseen (serrated tip; Stryker, Kalamazoo, MI); Spinal needle (shallow bevel; Becton Dickinson, Franklin Lakes, NJ); Westcott (collection chamber; Becton Dickinson, Franklin Lakes, NJ); and Menghini (double bevel; dAprioMed AB, Uppsala, Sweden).
The purpose of this study is to compare several needles, including a steerable needle, for image-guided procedures to determine which needle tip is superior regarding procedural ease, and gross and histological sample quality.
MATERIALS AND METHODS
Sample Collection: Needle Comparison
This study was conducted with approval from the institutional review board. Various needle types and gauges commonly used in musculoskeletal centers were tested: Chiba 22 g; Franseen 20 g; Franseen 22 g; Spinal 20 g; Spinal 22 g; Westcott 20 g; and Menghini 21 g (steerable needle). A lean bovine muscle sample was utilized. Each needle was blocked externally to achieve a standard 1-cm length. Each needle was advanced into the muscle block ten times as the stylet was slowly removed. All needle passes were performed by one of two fellowship-trained musculoskeletal oncologists following the same protocol (AP and AZ). The core sample was collected and assessed for gross integrity (poor, fair, good, or excellent) and size (poor to excellent); each needle was graded for overall ease of use and sample collection (poor to excellent).
All biopsy material was fixed in 10% buffered formalin (Fisher Brand, Waltham, MA) for 24 hr. After fixation, the tissue was processed, embedded in paraffin, cut on a Reichert-Jung microtome (Reichert Technologies, Depew, NY) at 4 μ, and placed on glass slides. The biopsy slides were stained with hematoxylin and eosin (H&E), cover slipped and subsequently examined by a surgical pathologist (BO). All slides were evaluated by the same surgical pathologist for preservation, crush artifact, tissue fragmentation, and overall biopsy measurements.
Histological Analysis of Needle Track
The steerable needle was placed 4 cm into tissue and the curve maximally deployed; the needle was then removed. A permanent curve was made in a 20-g spinal needle, which was inserted an equal depth into the adjacent tissue and removed. Each needle entry site was marked with methylene blue. Tracks were analyzed histologically by a surgical pathologist for tissue damage (BO).
Observation of Steerable Needle Characteristics
CT was used to evaluate needle steering characteristics in tissue; large porcine extremity tissue samples including subcutaneous fat, muscle and bone were used to simulate the variety of human tissue stiffness and to enable observation of needle characteristics at depth.
To evaluate needle advancement characteristics, the ease of needle passage through tissue was first analyzed. As the needle was passed through tissue by the same musculoskeletal radiologist (AP), any catching, kinking or other difficulty in advancement was recorded. Ability to perform single and double curves in tissue was tested. Feasibility of the needle to access targets around obstacles was assessed. Static needle characteristics in tissue were evaluated: needle tip position was monitored for stability using repeat CT scans with the stylet curve released in tissue. The needle tip was also monitored for deflection as the maximally curved stylet was withdrawn while the needle remained in place. This procedure was repeated as the outer needle was repeatedly withdrawn and advanced, simulating a fine needle aspiration and biopsy procedure. Finally the entire mechanism was withdrawn (outer needle and stylet together) with the curve maximally deployed. Following multiple uses and curve deployments, needles were assessed for wear, breakage, or memory (i.e., permanent curve).
Sample Collection: Needle Comparison
Both the Menghini 21 g and Chiba 22 g needles were graded as excellent in terms of their ease of use (Table 1). Lowest ease of use was the Franseen (20 g and 22 g), graded as poor due to difficulty separating the sample from the serrated tip. Gross evaluation also showed the best integrity of sample to be achieved with the Menghini and Chiba needles, both graded as excellent. The Franseen 22 g showed the highest degree of fragmentation. Gross sample size was largest with the Menghini and Chiba needles (graded as excellent) and smallest with the Franseen 22 g and the Westcott 20 g, both graded as poor. Histologic evaluation showed good preservation with all specimens. Crush artifact was only present with the sample from the 20-g spinal needle. Fragmentation was present in all samples except the Chiba 22 g, and was most severe with the sample from the Franseen 20 g and Westcott 20 g needles. Histology sample measurements were: Chiba 22 g: 0.6×0.3 mm; Spinal 22 g: 1.5×0.4 mm; Franseen 22 g: 2.9×0.5 mm; Menghini 21 g: 2.6×0.6 mm; Spinal 20 g: 2.0×0.5 mm; Franseen 20 g: 4.6×0.7 mm; and Westcott 20 g: 5.0×0.8 mm.
Histological Analysis of Needle Track
Needle tracks created by the curved steerable needle as well as the permanently curved 20-g spinal needle both showed no histologically detectable damage to surrounding tissue.
Observation of Steerable Needle Characteristics
Five steerable needles were used for testing; approximately 20 curve deployment and release cycles were performed for each needle in tissue. The needles advanced easily through the porcine tissue sample, even when maximally curved. The lever and mechanism functioned reliably. The lever did not relax or snap back to another position but remained in partial or full deployment as set by the tester. There were no instances of catching, kinking, or malfunction of the mechanism. In tissue the curvature appropriately changed needle direction in a controllable fashion (Figure 1). Smaller or larger curves were feasible to avoid obstacles and direct the tip to targets. The mechanism appeared to be especially useful for making a small adjustment close to the target (Figure 2). A double curve was also feasible, acquired by releasing the curve, turning the hub 180 degrees, redeploying the curve and advancing further (Figure 3). Maximal curvature did not seem to be affected by tissue stiffness in the physiological range (e.g., muscle vs. fat).
Next, the needle was tested for stability of position. Needle curve was released in tissue and the stylet removed while CT images were acquired. CT showed no deflection or change in position of the needle tip (Figure 4); therefore, if injection or aspiration is performed, the stylet can be removed, and the structure or joint accessed without change in tip location.
On the other hand, if the needle is used for fine needle aspiration and biopsy, the stylet is slowly removed while the needle is repeatedly advanced and withdrawn. This technique was performed under CT guidance. It was found that as the stylet curvature was relaxed and the needle pulled back and advanced, the outer needle relaxed to a more straightened position slowly (Figure 5). The advantage of this while performing fine needle aspiration (FNAB) biopsy is that different areas of the lesion can be sampled. This effect will only be observed when the FNAB is initiated with the needle in curved position.
Finally, the needle was tested for withdrawal characteristics. CT was performed while the needle was pulled back. Initially, the needle was placed with a maximal curve; the stylet curvature was released and removed. The curved outer needle was removed in stages while CT was performed; the needle followed the track of entry. Second, the needle was placed in maximally curved position, and the stylet was removed without releasing the curvature. There was no change in position of the needle tip (Figure 6). Third, the needle was placed in maximally curved position, and the entire mechanism (outer needle and stylet) was removed while remaining in a curved state. Again, the needle path followed the course of entry, without evidence of damage to surrounding tissue (Figure 7).
Five steerable needles were used in testing. Needle curvature was maximally deployed and released approximately 20 times each. There was no evidence of plastic deformation or dysfunction of the mechanism. On the other hand, there was no instance in which the curvature spontaneously released or the lever relaxed to a different position. During testing, no needle stylet broke, and all the needles remained completely functional after testing was completed. No wear was evident in any steerable needle tested. There was no evident loss of sharpness (i.e., no difficulty in advancement through tissue) during testing.
In 1982, a study by Mankin et al.10 described the complications associated with poorly performed biopsy of primary musculoskeletal malignancies. The authors found an 18.2% rate of major treatment alterations (i.e. surgeon carrying out different or more complex surgery) secondary to inaccurate or inappropriate biopsies. When the study was repeated 14 yr later, there was not a significant change in this rate.8 Clearly, the details of the biopsy procedure warrant further study. The technique of needle biopsy has been shown in several studies to approach the diagnostic accuracy of open surgical biopsy but has distinct advantages.2,5 Optimization of the needle tip represents one means to improve this procedure. The goal of this study was to investigate the ease of utilization, quality of tissue obtained, and adverse outcomes associated with needle selection.
There has been a great deal of research and development directed toward needle design, especially regarding the size and tip.11–14 The tip serves two basic functions: guiding the needle through tissue, and cutting the sample or aspirating or injecting with the stylet removed. Beveled (angled) tips and diamond (centrally pointed) tips are both efficient for passing through organic tissue, but the bevel has a slight advantage in allowing for slight change in direction during needle placement; the needle will tend to turn away from the bevel, and this effect can be enhanced by deflection of the hub. However, the degree of change in direction may be difficult to predict or control; it is partially dependent upon needle depth and stiffness of the tissue. Different needle tip designs also are intended to improve sample collection. Multiple studies have shown that there is little difference in yield between tip types. Precise localization within the lesion appears to be the most important factor in determining yield.13,15 Radiographic guidance (CT, fluoroscopy, ultrasound) is essential for localization and minimizing complications. Theoretically, a curvable needle could facilitate guidance of the needle, improve precision, and reduce complications. Flexible needle designs and various forms of fixed curves with robotic-controlled guidance have been used in an attempt to achieve this purpose.16–18 However, to our knowledge a dynamic steerable needle with variable curve capability and multipurpose use as a straight or curved configuration has not been previously tested.
This study evaluated a steerable needle developed for this purpose. The needle is a 21 g, 17 cm, multipurpose device with a Menghini double bevel tip. It is composed of a standard stainless steel outer needle and a stylet with a double core; one core is fixed while the other passes over a barrel and is connected to a lever at the hub. Deflection of the lever results in curvature of the stylet resulting in curvature of the outer needle. The needle curves in one direction but the lever mechanism at the hub can be rotated and the curve redeployed if a change in direction is needed. The needle can be used for FNAB as well as for injection procedures.
Gross differences in FNAB sample quality (size, sample integrity) as well as ease of use favored the Menghini and Chiba tip needles. Histological analysis following standardized collection technique showed highest quality sample with the steerable needle in terms of sample volume and fragmentation. On testing in tissue, the steerable needle appears to have certain advantages over a straight needle as well; the ability to curve the needle using imaging guidance allows for major adjustments around obstacles or dangerous regions, as well as minor adjustments (i.e., distal repositioning away from the needle course to reach a target). The Menghini and Chiba needles’ ability to precisely access tissue from a specific region of the tumor is particularly valuable for heterogenous tumors. For example, some high-grade tumors may have areas of necrosis that may provide suboptimal material for histologic examination, which could be better avoided with a steerable needle when compared to a standard needle.
For injections and aspirations, this study demonstrated that the needle tip position does not change if the curved stylet is removed. The needle can also effectively be used for FNAB; the technique is potentially enhanced by the configuration and function of the curvable needle. The recommended technique involves positioning the needle tip at the margin of the lesion, followed by slow withdrawal of the stylet as the outer needle is moved into the lesion repeatedly. With straight needles, the same track through the lesion is generally accessed over and over. With the curvable needle, the curvature slowly relaxes as the curved stylet is released; the needle tip slowly changes position as the needle is repeatedly pulled back and advanced, resulting in sampling of slightly different regions of the lesion. If this is not desired, the needle can be placed in a straight position and the needle will act as a straight needle with regard to FNAB.
Another potential advantage over straight needles is the control over deflection of the tip. If the curve is not deployed, the needle acts as a straight needle, advancing in a linear fashion. A standard straight needle with a bevel will tend to curve slightly in tissue as the bevel deflects the surrounding tissue, possibly in an uncontrolled fashion. Additionally, there was no histologically detectable damage to tissue surrounding the biopsy track when using the steerable or curved spinal needles, supporting recent findings that clinically significant tumor seeding along biopsy tracks generally does not occur.6
During in vitro testing, the steerable needle provides optimal biopsy material, exhibits predictable characteristics on advancement and withdrawal, and does not damage the surrounding tissue even when used in an unapproved manner (i.e., removal with curve deployed). Clinically, this presents a needle with several possible applications to improve biopsy outcomes. Although needle-based procedures, including those using imaging guidance, have been shown to yield adequate biopsy samples, a major disadvantage is the fact that straight needles have limited capability for changing direction once they have passed beyond the superficial fascia. Therefore, procedures demanding precise needle placement, especially those deep within the body or in obese patients, may require multiple passes before the optimal position is obtained. In addition, the shortest course to the target may be blocked by bone or a structure through which passage is contraindicated (e.g., organs or neurovascular structures), leading to a more difficult procedure: potentially longer, with increased radiation (in the case of CT and fluoroscopic guidance), more needle repositioning steps, a higher anesthesia dose and possibly greater morbidity.
A steerable needle may also be used for spine intervention, including transforaminal epidural injections, facet joint injections, and discography; fine needle aspiration and biopsy of suspected tumors in the abdomen; and joint procedures (aspiration and injection) in which there is a complicating factor (such as overlying infection or incision requiring an alternate approach). Utility may be enhanced in obese patients or patients who cannot tolerate standard positioning.
Differences in needle types can influence the quality and the precision of musculoskeletal biopsy. The steerable needle design appears to be advantageous with regard to accurate placement of the tip for tissue sampling. Multiple curves can be applied to the needle direction during placement, allowing for avoidance of obstacles and dangerous areas. Compared to other needles, the steerable needle was found to be durable and easy to use. It allowed for precise navigation around vital structures to yield superior integrity of sample tissue, with little crush artifact or injury to surrounding tissue, and presents several potential clinical applications to increase yield and reduce morbidity in needle-based procedures. Further testing of this needle type will be needed in the clinical setting to determine the advantages and drawbacks over other needle types for musculoskeletal biopsy.
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Keywords:Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved
needle biopsy; biopsy; musculoskeletal tumor; tumor; sarcoma