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Management and localization strategies for the nonpalpable Implanon rod
Contraception 73 (2006) 325 – 330
Review article
Management and localization strategies for the nonpalpable Implanon rod Lee P. Shulmana,4, Helena Gabrielb a
Division of Reproductive Genetics, Department of Obstetrics and Gynecology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA b Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA Received 1 March 2005; revised 1 September 2005; accepted 10 October 2005
Abstract Purpose: The goal of this paper is to review the imaging methods required for localizing nonpalpable Implanonk. Method: Different localization methods for nonpalpable Implanon rods are summarized, and clinical guidance is provided as to how best to localize such implants. Results: In the great majority of cases, optimal visualization of the single-rod Implanon rod is obtained with ultrasound using a highresolution linear array transducer (10 –15 MHz). An implant located just under the skin, under the fascia muscularis or one located deep in the muscle can most often be localized with ultrasound. In rare cases where ultrasound does not definitively locate the implant, magnetic resonance imaging is usually the next best choice. Measurements of serum etonogestrel levels may be necessary to confirm the presence or absence of the implant when it cannot be visualized by either of the two imaging methods. Discussion: Close clinical coordination between women’s health care providers and radiologists is required to minimize or prevent removal complications and to facilitate subsequent contraceptive management of the patient. D 2006 Elsevier Inc. All rights reserved. Keywords: Implanon; Etonogestrel (ENG); Contraceptive implant; Localization; Imaging methods; Ultrasound; Magnetic resonance imaging (MRI)
1. Introduction Subdermal contraceptive implants provide long-acting reliable contraception. Implanonk (manufactured for Organon USA, Roseland, NJ, by N.V. Organon, Oss, The Netherlands) is a single-rod, nonbiodegradable, implantable contraceptive that has been used widely throughout the world (in 32 countries worldwide in Europe, Australia and Southeast Asia), providing contraceptive protection for up to 3 years [1– 3]. It consists of a core containing the selective progestin etonogestrel (ENG) and ethylene vinyl acetate (EVA) copolymer surrounded by a rate-controlling EVA membrane. The rod is 40 mm in length and 2 mm in diameter. Etonogestrel, the active metabolite of desogestrel, is a progestin with a well-established safety and efficacy profile [3], which is also used in the contraceptive ENG/ ethinyl estradiol vaginal ring (NuvaRingR, Organon USA). Implanon is inserted with a unique, specially designed, preloaded, disposable applicator (Fig. 1) [4]. The Implanon 4 Corresponding author. Tel.: +1 312 926 6627; fax: +1 312 926 6675. E-mail address: [email protected] (L.P. Shulman). 0010-7824/$ – see front matter D 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.contraception.2005.10.009
rod is placed in the needle of the disposable applicator, and the loaded applicator is packaged in a blister tray, which is then sterilized by gamma irradiation. Because the sterile rod is contained within the needle of the applicator, there is no handling of the implant itself, minimizing the potential for the implant to be contaminated during insertion. The applicator also eliminates the need for an incision, thereby reducing scarring. Results from 16 clinical studies with Implanon, enrolling 1453 patients, show that insertion is quick and easy; the mean Implanon insertion time was 1.4F1.7 min (data on file). When the implant is inserted properly, removal is usually quick and easy. Results from the 16 clinical studies described hereinbefore show that average Implanon removal time was 4.2F4.9 min (data on file). However, if the implant is not inserted according to the instructions in the package insert, if there is migration or fibrosis of the implant, it may not be palpable, requiring imaging methods for its localization and subsequent removal. In this review, we describe localization methods for nonpalpable Implanon and advise clinicians on avoiding insertion and removal complications. Our observations appear to be in agreement
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Fig. 1. Implanonk applicator.
with recently published papers from England and Australia [5,6], countries where Implanon has been on the market for several years. We refer to Implanon as either the rod or the implant interchangeably. 2. Techniques for insertion, removal and localization of Implanon 2.1. Proper insertion of Implanon In order to prevent or minimize complications at the time of either insertion or removal of Implanon, it is critical to follow proper insertion procedures (found in the package insert). Following these procedures will increase the likelihood that the Implanon rod will be easy to palpate, making the localization and removal procedures relatively uncomplicated. The placement of Implanon in the arm must always be verified by palpation by both the patient and the doctor, and this step is critical for minimizing complications at the time of removal [6]. The Implanon applicator facilitates the proper placement of the implant. We recommend verification of the presence of the implant in the applicator needle visually prior to insertion of the needle into the arm and checking the needle for the absence of the implant following insertion. When handling the applicator in preparation for insertion, keep the tip of the cannula pointed upward to prevent Implanon from falling out. The protruding end of the obturator appearing in the tip of the needle after insertion should not be confused with the implant because they are the same color. However, the obturator tip is grooved, whereas the implant is smooth (Fig. 1). The design of the applicator also allows the clinician to keep the needle in a superficial plane and permits a withdrawal method of insertion.
longitudinal direction, toward the distal tip of the implant (the end closest to the elbow). The implant is then removed by either the bpop-outQ technique described by Darney et al. [7] or the implant is grasped with a small curved sterile hemostat and removed through the incision. If the implant cannot be pushed by pressing the opposite end toward the incision, the tissue around the implant is gently dissected and then the implant is pushed toward the incision. Following the insertion procedures as described in the package insert can considerably minimize or prevent complications. Nevertheless, in rare instances, the implant may not be palpable. The inability to palpate the implant in such circumstances is usually the result of incorrect insertion or noninsertion, the presence of large amounts of subcutaneous fat, migration from the site of initial insertion or development of dense fibrous sheaths [5,8]. Hereinafter, we describe imaging methods for the localization of such nonpalpable implants. 2.3. Proper imaging methods for localization of nonpalpable Implanon Lantz et al. [9] published one of the first reports of localization characteristics of a subdermally placed Implanon rod. The authors describe a posterior acoustic shadow cast by Implanon and recommend performing ultrasound sonography with a 5- or 7.5-MHz transducer and a 2-cm standoff pad to localize subdermally implanted implants in the transverse direction. This recommendation, with some modifications due to technological advances, still holds at the present time, especially as a result of the advent of the high- or very high frequency linear array transducers, like those described by Amann et al. [8], Kaptein and Ganpat [10] and Westerway et al. [11]. These authors recommend the use of ultrasound as first-line localization technique for subdermally implanted, clinically nonpalpable Implanon,
2.2. Proper removal of palpable Implanon Before attempting removal, the implant should be palpated to confirm its position and location. Once the implant is located, the arm is anesthetized with a small amount of local anesthetic. A small incision, approximately 2 to 3 mm in length, is made over the implant, in the
Fig. 2. Properly inserted Implanon — transverse view. The best way to visualize Implanon with ultrasound is to first look in transverse view and find sharp acoustic shadow (eclipse). The arrow points to the actual implant, whereas the dark line underneath represents the shadow or eclipse cast by the implant.
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Fig. 3. Implant and the associated shadow — transverse (left) and longitudinal (right) view. Visualization is accomplished with a 15-MHz transducer in both pictures. (A) Transverse view of implant. The arrow points to the implant. The ultrasonographic bshadowingQ or beclipse effectQ of the implant is well observed in this ultrasound view. (B) Longitudinal view of the implant. The arrow points to the implant. Visualization of the length of the implant is facilitated by identifying the implant in a transverse view with the distinctive beclipseQ shadow. The shadowing effect of the implant is seen below the implant; the distinction between the nonshadowed area and shadowed area is best seen in the area below the arrow.
together with high- to very high frequency transducers (7–15 MHz) [8–11]. However, our experience shows that we could not obtain a consistently adequate image with a 7-MHz transducer and needed a higher-frequency (10–15 MHz) transducer, like that used for musculoskeletal ultrasound. Commercially available high-resolution transducers now reach frequencies of 15 MHz and are routinely being used in breast, musculoskeletal and other small-part ultrasound imaging [12–17]. The higher frequency allows for higher axial spatial resolution. The linear array type of transducer also allows for excellent near- and far-field resolution, thus, precluding the need for a standoff pad, as was needed earlier with lower-frequency transducers. It is these technological
Fig. 4. Longitudinal view of the full length of the implant inserted in the m. biceps. Longitudinal ultrasound image of the full length of an implant inserted in the m. biceps using a 12- to 5-MHz transducer. The oval indicates the actual implant.
advances that allow better visualization of what is often referred to as the bsignatureQ appearance of the Implanon rod when the ultrasound scans are done at right angles to the rod — that is, as a 2-mm-diameter, superficial, highly echogenic, linear structure casting a strong posterior acoustic shadow [10,11]. The implant is thus seen as a small, but clear, echogenic spot (see Figs. 2–5). In order to achieve these results, the following steps should be followed. Start the ultrasound examination with a high-frequency, linear array transducer as close to 15 MHz
Fig. 5. Implant inserted deep in m. biceps — transverse view. This image shows how easily fascia or other echogenic structures can be confused with the actual Implanon. Upon first view, it would appear that the echogenic line is the Implanon rod in a sagittal view. However, the rod (arrow) is actually in transverse view and is identified by the sharp acoustic shadow underneath. This is a transverse ultrasound image of an implant inserted deep into the m. biceps using a 12- to 5-MHz transducer. The arrow indicates the actual implant.
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Fig. 6. Overview MRI of properly placed Implanon. Overview of a series of MRI images of the upper arm, in which appearance and disappearance of the signal-void area (the diameter of the implant), is shown from left to right. The implant is in the subcutaneous fat tissue and is marked by the arrow.
as possible. The transducer should be placed to scan in the transverse plane of the arm. A larger footprint, on the order of 50 mm, is also helpful in identifying the full length of the implant on longitudinal images. A superficial structure preset should be selected, and the beam should be focused superficially no deeper than 3 cm, assuming the implant is inserted correctly. Multiple focal zones can be used. In order to locate the implant, the posterior acoustic shadowing, referred to as an beclipse sign,Q is first identified. The eclipse sign is observed because the passage of the transducer over the implant results in a shadow appearing as in a celestial
eclipse. This shadow occurs because the implant has a very different acoustic impedance compared to the adjacent soft tissues. This causes reflection of sound back to the transducer, whereas there is little sound posterior to the implant. This results in what is termed posterior acoustic shadow, or the celestial eclipse. Once this eclipse sign is detected, it is possible to look for the echogenic focus or spot at the superior apex of the shadow, representing the actual implant (see Figs. 2–5). The transducer is then turned 908 to obtain a longitudinal view of the implant (Fig. 4). The entire implant can usually be seen in this view, although clinicians will
Fig. 7. Properly inserted Implanon-MRI scan. Axial and coronal T1-weighted MRI sequence demonstrates the properly placed implant with a circle in A and an oval in B.
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rately, we recommend it only as second-line visualization modality because of its high cost, limited access in certain parts of the world and claustrophobia by some individuals undergoing MRI [20]. 2.4. Measurement of ENG levels
Fig. 8. Deeply placed Implanon. T1-weighted axial image demonstrates that the implant (shown with a circle) is located in the biceps muscle.
notice how direct visualization of the rod without the benefit of the eclipse sign is problematic because the appearance of the echogenic implant in the longitudinal view is similar to other echogenic structures within the subcutaneous tissue (see Fig. 5). Finally, one can now mark the exact position of both tips of the implant on the skin with a skin marker. Once the implant is identified, the incision for removal can be made directly over the distal end of Implanon, allowing it to be pushed out through the incision. The fibrous capsule that may have been formed can be bluntly or sharply dissected from the end of the implant before removal is attempted. Deep implants sometimes require a larger incision (about 1 in.), often followed by the inverse U-technique as developed for the removal of Norplant [18]. On rare occasions, if implants are placed deep within the muscle or just beneath the fascia of the muscularis biceps, ultrasound may not detect the implants, even when using a 15-MHz linear array transducer [19]. In these relatively rare cases, magnetic resonance imaging (MRI) can serve as an appropriate second-line imaging modality, especially in cases of deeply inserted, nonpalpable implants [11,19,20]. On sequential transverse MRI scans, the implant appears as a signal-void black spot 2 mm in diameter (the thickness of the implant in a sagittal plane), which can then be followed through sequential scan layers, adding up to 40 mm (the total length of the implant), and then disappears. The appearance and disappearance of implant on the MRI scans help to differentiate it from nearby blood vessels and other anatomical structures (see Fig. 6). Implanon is bestidentified accurately by the MRI in axial plane (Figs. 7A and 8), although it can also be clearly observed in a coronal plane as well (Fig. 7B). The fatsuppression technique should be avoided, whereas the use of an MRI-contrast agent is often helpful if the implant is localized close to vessels [19]. Caution should always be exercised when differentiating blood vessels and fibrous septa from the Implanon rod on the MRI scans [11]. However, even though MRI localizes the implants accu-
Ultrasound and MRI should localize the vast majority of nonpalpable Implanon rods. On those rare occasions when further definitive proof of the presence or absence of Implanon is required because imaging techniques have failed to localize the rod, measuring serum ENG levels will confirm whether Implanon is in situ but will not localize its position [10,20]. For example, Kaptein and Ganpat [10] described a case of a woman whose Implanon could not be visualized using ultrasound scans. A negative serum ENG level confirmed the absence of Implanon by demonstrating undetectable levels of the active component of Implanon, ENG. Determination of serum ENG levels can be carried out by any local Organon affiliate. 3. Clinical guidelines Implanon is a single-rod, progestin-only, implantable subdermal contraceptive that has been used widely throughout the world and that provides reliable contraceptive protection for up to 3 years. In contrast to multiple-rod systems, such as the six-capsule levonorgestrel implants, the advantages of the single-rod Implanon is that insertion and removal are relatively quick and easy, markedly reducing the potential for improper insertion and resulting in fewer complications during removal. However, if insertion is not done properly, there may be complications with removal of Implanon. It is thus essential that clinicians familiarize themselves with proper insertion techniques and that they work in close liaison with radiologists to localize any nonpalpable implants by ultrasound and, if necessary, by MRI scanning techniques [19,20]. In addition, we strongly recommend that clinicians do not attempt to remove a deeply implanted Implanon rod without first localizing it as described hereinbefore. We also recommend that they coordinate care with radiologists who have the proper equipment. Once the implant has been localized, it is strongly recommended not to put off its removal, but rather, to remove it immediately following localization; this approach will also minimize potential problems [6].
4. Conclusion Meticulous insertion technique will minimize difficulties at the time of Implanon removal. In the unlikely event that an Implanon rod cannot be localized prior to removal, close clinical coordination between women’s health care providers and radiologists is needed to minimize or prevent further complications and facilitate removal of the rod and subsequent contraceptive management of the patient.
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Acknowledgments Writing and editing support for this manuscript was provided by Lena S. Shapiro, Ph.D. Dr. Lee Shulman is a consultant for Organon, Ortho-McNeil, Berlex and Novo-Nordisk. References [1] Brache V, Faundes A, Alvarez F. Risk–benefit effects of implantable contraceptives in women. Expert Opin Drug Saf 2003;2:321 – 32. [2] Collins DC. Sex hormone receptor binding, progestin selectivity, and the new oral contraceptives. Am J Obstet Gynecol 1994;170: 1508 – 13. [3] Croxatto HB, Urbancsek J, Massai R, Coelingh Bennick H, van Beek A, and the Implanon Study Group. A multicentre efficacy and safety study of the single contraceptive implant Implanon. Hum Reprod 1999;14:976 – 81. [4] Mascarenhas L. Insertion and removal of Implanon: practical considerations. Eur J Contracept Reprod Health Care 2000; 5(Suppl 2):29 – 34. [5] Piessens SG, Palmer DC, Sampson AJ. Ultrasound localisation of non-palpable Implanon. Aust N Z J Obstet Gynaecol 2005;45:112 – 6. [6] Navani M, Robinson C. Clinical challenge with Implanon removal: a case report. J Fam Plann Reprod Health Care 2005;31:161 – 2. [7] Darney PD, Klaisle CM, Walker DM. The bPop-OutQ method of Norplant removal. Adv Contracept 1992;8:188 – 9. [8] Amann P, Botta U, Montet X, Bianchi S. Sonographic detection and localization of a clinically nondetectable subcutaneous contraceptive implant. J Ultrasound Med 2003;22:855 – 9.
[9] Lantz A, Nosher JL, Pasquale S, Siegel RL. Ultrasound characteristics of subdermally implanted Implanonk contraceptive rods. Contraception 1997;56:323 – 7. [10] Kaptein MCJ, Ganpat R. Localization of non-palpable single-rod contraceptive implants using ultrasound sonography. Eur J Contracept Reprod Health Care 2002;7(Suppl 1):86. [11] Westerway SC, Picker R, Christie J. Implanon implant detection with ultrasound and magnetic resonance imaging. Aust N Z J Obstet Gynaecol 2003;43:346 – 50. [12] Lagalla R, Midiri M. Image quality control in breast ultrasound. Eur J Radiol 1998;27(Suppl 2):S229 – 33. [13] Rizzatto GJ. Towards a more sophisticated use of breast ultrasound. Eur Radiol 2001;11:2425 – 35. [14] Ahuja AT, Richards P, Wong KT, Yuen EH, King AD. Accuracy of high-resolution sonography compared with magnetic resonance imaging in the diagnosis of head and neck venous vascular malformations. Clin Radiol 2003;58:869 – 75. [15] Benson CB. Sonography of the musculoskeletal system. Rheum Dis Clin North Am 1991;17:487 – 504. [16] Rasmussen OS. Sonography of tendons. Scand J Med Sci Sports 2000;10:360 – 4. [17] Bianchi S, Martinoli C, Sureda D, Rizzatto G. Ultrasound of the hand. Eur J Ultrasound 2001;14:29 – 34. [18] Rosenberg MJ, Alvarez F, Barone MA, Waugh MS, Brache V, Pollack AE. A comparison of bU Q and standard techniques for Norplant removal. Obstet Gynecol 1997;89:168 – 73. [19] Merki-Feld GS, Brekenfeld C, Migge B, Keller PJ. Nonpalpable ultrasonographically not detectable Implanon rods can be localized by magnetic resonance imaging. Contraception 2001;63:325 – 8. [20] Stillwell S, Sheppard P, Searle S. The impalpable Implanon: a case report. J Fam Plann Reprod Health Care 2003;29:156 – 7.
Review article
Management and localization strategies for the nonpalpable Implanon rod Lee P. Shulmana,4, Helena Gabrielb a
Division of Reproductive Genetics, Department of Obstetrics and Gynecology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA b Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA Received 1 March 2005; revised 1 September 2005; accepted 10 October 2005
Abstract Purpose: The goal of this paper is to review the imaging methods required for localizing nonpalpable Implanonk. Method: Different localization methods for nonpalpable Implanon rods are summarized, and clinical guidance is provided as to how best to localize such implants. Results: In the great majority of cases, optimal visualization of the single-rod Implanon rod is obtained with ultrasound using a highresolution linear array transducer (10 –15 MHz). An implant located just under the skin, under the fascia muscularis or one located deep in the muscle can most often be localized with ultrasound. In rare cases where ultrasound does not definitively locate the implant, magnetic resonance imaging is usually the next best choice. Measurements of serum etonogestrel levels may be necessary to confirm the presence or absence of the implant when it cannot be visualized by either of the two imaging methods. Discussion: Close clinical coordination between women’s health care providers and radiologists is required to minimize or prevent removal complications and to facilitate subsequent contraceptive management of the patient. D 2006 Elsevier Inc. All rights reserved. Keywords: Implanon; Etonogestrel (ENG); Contraceptive implant; Localization; Imaging methods; Ultrasound; Magnetic resonance imaging (MRI)
1. Introduction Subdermal contraceptive implants provide long-acting reliable contraception. Implanonk (manufactured for Organon USA, Roseland, NJ, by N.V. Organon, Oss, The Netherlands) is a single-rod, nonbiodegradable, implantable contraceptive that has been used widely throughout the world (in 32 countries worldwide in Europe, Australia and Southeast Asia), providing contraceptive protection for up to 3 years [1– 3]. It consists of a core containing the selective progestin etonogestrel (ENG) and ethylene vinyl acetate (EVA) copolymer surrounded by a rate-controlling EVA membrane. The rod is 40 mm in length and 2 mm in diameter. Etonogestrel, the active metabolite of desogestrel, is a progestin with a well-established safety and efficacy profile [3], which is also used in the contraceptive ENG/ ethinyl estradiol vaginal ring (NuvaRingR, Organon USA). Implanon is inserted with a unique, specially designed, preloaded, disposable applicator (Fig. 1) [4]. The Implanon 4 Corresponding author. Tel.: +1 312 926 6627; fax: +1 312 926 6675. E-mail address: [email protected] (L.P. Shulman). 0010-7824/$ – see front matter D 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.contraception.2005.10.009
rod is placed in the needle of the disposable applicator, and the loaded applicator is packaged in a blister tray, which is then sterilized by gamma irradiation. Because the sterile rod is contained within the needle of the applicator, there is no handling of the implant itself, minimizing the potential for the implant to be contaminated during insertion. The applicator also eliminates the need for an incision, thereby reducing scarring. Results from 16 clinical studies with Implanon, enrolling 1453 patients, show that insertion is quick and easy; the mean Implanon insertion time was 1.4F1.7 min (data on file). When the implant is inserted properly, removal is usually quick and easy. Results from the 16 clinical studies described hereinbefore show that average Implanon removal time was 4.2F4.9 min (data on file). However, if the implant is not inserted according to the instructions in the package insert, if there is migration or fibrosis of the implant, it may not be palpable, requiring imaging methods for its localization and subsequent removal. In this review, we describe localization methods for nonpalpable Implanon and advise clinicians on avoiding insertion and removal complications. Our observations appear to be in agreement
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Fig. 1. Implanonk applicator.
with recently published papers from England and Australia [5,6], countries where Implanon has been on the market for several years. We refer to Implanon as either the rod or the implant interchangeably. 2. Techniques for insertion, removal and localization of Implanon 2.1. Proper insertion of Implanon In order to prevent or minimize complications at the time of either insertion or removal of Implanon, it is critical to follow proper insertion procedures (found in the package insert). Following these procedures will increase the likelihood that the Implanon rod will be easy to palpate, making the localization and removal procedures relatively uncomplicated. The placement of Implanon in the arm must always be verified by palpation by both the patient and the doctor, and this step is critical for minimizing complications at the time of removal [6]. The Implanon applicator facilitates the proper placement of the implant. We recommend verification of the presence of the implant in the applicator needle visually prior to insertion of the needle into the arm and checking the needle for the absence of the implant following insertion. When handling the applicator in preparation for insertion, keep the tip of the cannula pointed upward to prevent Implanon from falling out. The protruding end of the obturator appearing in the tip of the needle after insertion should not be confused with the implant because they are the same color. However, the obturator tip is grooved, whereas the implant is smooth (Fig. 1). The design of the applicator also allows the clinician to keep the needle in a superficial plane and permits a withdrawal method of insertion.
longitudinal direction, toward the distal tip of the implant (the end closest to the elbow). The implant is then removed by either the bpop-outQ technique described by Darney et al. [7] or the implant is grasped with a small curved sterile hemostat and removed through the incision. If the implant cannot be pushed by pressing the opposite end toward the incision, the tissue around the implant is gently dissected and then the implant is pushed toward the incision. Following the insertion procedures as described in the package insert can considerably minimize or prevent complications. Nevertheless, in rare instances, the implant may not be palpable. The inability to palpate the implant in such circumstances is usually the result of incorrect insertion or noninsertion, the presence of large amounts of subcutaneous fat, migration from the site of initial insertion or development of dense fibrous sheaths [5,8]. Hereinafter, we describe imaging methods for the localization of such nonpalpable implants. 2.3. Proper imaging methods for localization of nonpalpable Implanon Lantz et al. [9] published one of the first reports of localization characteristics of a subdermally placed Implanon rod. The authors describe a posterior acoustic shadow cast by Implanon and recommend performing ultrasound sonography with a 5- or 7.5-MHz transducer and a 2-cm standoff pad to localize subdermally implanted implants in the transverse direction. This recommendation, with some modifications due to technological advances, still holds at the present time, especially as a result of the advent of the high- or very high frequency linear array transducers, like those described by Amann et al. [8], Kaptein and Ganpat [10] and Westerway et al. [11]. These authors recommend the use of ultrasound as first-line localization technique for subdermally implanted, clinically nonpalpable Implanon,
2.2. Proper removal of palpable Implanon Before attempting removal, the implant should be palpated to confirm its position and location. Once the implant is located, the arm is anesthetized with a small amount of local anesthetic. A small incision, approximately 2 to 3 mm in length, is made over the implant, in the
Fig. 2. Properly inserted Implanon — transverse view. The best way to visualize Implanon with ultrasound is to first look in transverse view and find sharp acoustic shadow (eclipse). The arrow points to the actual implant, whereas the dark line underneath represents the shadow or eclipse cast by the implant.
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327
Fig. 3. Implant and the associated shadow — transverse (left) and longitudinal (right) view. Visualization is accomplished with a 15-MHz transducer in both pictures. (A) Transverse view of implant. The arrow points to the implant. The ultrasonographic bshadowingQ or beclipse effectQ of the implant is well observed in this ultrasound view. (B) Longitudinal view of the implant. The arrow points to the implant. Visualization of the length of the implant is facilitated by identifying the implant in a transverse view with the distinctive beclipseQ shadow. The shadowing effect of the implant is seen below the implant; the distinction between the nonshadowed area and shadowed area is best seen in the area below the arrow.
together with high- to very high frequency transducers (7–15 MHz) [8–11]. However, our experience shows that we could not obtain a consistently adequate image with a 7-MHz transducer and needed a higher-frequency (10–15 MHz) transducer, like that used for musculoskeletal ultrasound. Commercially available high-resolution transducers now reach frequencies of 15 MHz and are routinely being used in breast, musculoskeletal and other small-part ultrasound imaging [12–17]. The higher frequency allows for higher axial spatial resolution. The linear array type of transducer also allows for excellent near- and far-field resolution, thus, precluding the need for a standoff pad, as was needed earlier with lower-frequency transducers. It is these technological
Fig. 4. Longitudinal view of the full length of the implant inserted in the m. biceps. Longitudinal ultrasound image of the full length of an implant inserted in the m. biceps using a 12- to 5-MHz transducer. The oval indicates the actual implant.
advances that allow better visualization of what is often referred to as the bsignatureQ appearance of the Implanon rod when the ultrasound scans are done at right angles to the rod — that is, as a 2-mm-diameter, superficial, highly echogenic, linear structure casting a strong posterior acoustic shadow [10,11]. The implant is thus seen as a small, but clear, echogenic spot (see Figs. 2–5). In order to achieve these results, the following steps should be followed. Start the ultrasound examination with a high-frequency, linear array transducer as close to 15 MHz
Fig. 5. Implant inserted deep in m. biceps — transverse view. This image shows how easily fascia or other echogenic structures can be confused with the actual Implanon. Upon first view, it would appear that the echogenic line is the Implanon rod in a sagittal view. However, the rod (arrow) is actually in transverse view and is identified by the sharp acoustic shadow underneath. This is a transverse ultrasound image of an implant inserted deep into the m. biceps using a 12- to 5-MHz transducer. The arrow indicates the actual implant.
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Fig. 6. Overview MRI of properly placed Implanon. Overview of a series of MRI images of the upper arm, in which appearance and disappearance of the signal-void area (the diameter of the implant), is shown from left to right. The implant is in the subcutaneous fat tissue and is marked by the arrow.
as possible. The transducer should be placed to scan in the transverse plane of the arm. A larger footprint, on the order of 50 mm, is also helpful in identifying the full length of the implant on longitudinal images. A superficial structure preset should be selected, and the beam should be focused superficially no deeper than 3 cm, assuming the implant is inserted correctly. Multiple focal zones can be used. In order to locate the implant, the posterior acoustic shadowing, referred to as an beclipse sign,Q is first identified. The eclipse sign is observed because the passage of the transducer over the implant results in a shadow appearing as in a celestial
eclipse. This shadow occurs because the implant has a very different acoustic impedance compared to the adjacent soft tissues. This causes reflection of sound back to the transducer, whereas there is little sound posterior to the implant. This results in what is termed posterior acoustic shadow, or the celestial eclipse. Once this eclipse sign is detected, it is possible to look for the echogenic focus or spot at the superior apex of the shadow, representing the actual implant (see Figs. 2–5). The transducer is then turned 908 to obtain a longitudinal view of the implant (Fig. 4). The entire implant can usually be seen in this view, although clinicians will
Fig. 7. Properly inserted Implanon-MRI scan. Axial and coronal T1-weighted MRI sequence demonstrates the properly placed implant with a circle in A and an oval in B.
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329
rately, we recommend it only as second-line visualization modality because of its high cost, limited access in certain parts of the world and claustrophobia by some individuals undergoing MRI [20]. 2.4. Measurement of ENG levels
Fig. 8. Deeply placed Implanon. T1-weighted axial image demonstrates that the implant (shown with a circle) is located in the biceps muscle.
notice how direct visualization of the rod without the benefit of the eclipse sign is problematic because the appearance of the echogenic implant in the longitudinal view is similar to other echogenic structures within the subcutaneous tissue (see Fig. 5). Finally, one can now mark the exact position of both tips of the implant on the skin with a skin marker. Once the implant is identified, the incision for removal can be made directly over the distal end of Implanon, allowing it to be pushed out through the incision. The fibrous capsule that may have been formed can be bluntly or sharply dissected from the end of the implant before removal is attempted. Deep implants sometimes require a larger incision (about 1 in.), often followed by the inverse U-technique as developed for the removal of Norplant [18]. On rare occasions, if implants are placed deep within the muscle or just beneath the fascia of the muscularis biceps, ultrasound may not detect the implants, even when using a 15-MHz linear array transducer [19]. In these relatively rare cases, magnetic resonance imaging (MRI) can serve as an appropriate second-line imaging modality, especially in cases of deeply inserted, nonpalpable implants [11,19,20]. On sequential transverse MRI scans, the implant appears as a signal-void black spot 2 mm in diameter (the thickness of the implant in a sagittal plane), which can then be followed through sequential scan layers, adding up to 40 mm (the total length of the implant), and then disappears. The appearance and disappearance of implant on the MRI scans help to differentiate it from nearby blood vessels and other anatomical structures (see Fig. 6). Implanon is bestidentified accurately by the MRI in axial plane (Figs. 7A and 8), although it can also be clearly observed in a coronal plane as well (Fig. 7B). The fatsuppression technique should be avoided, whereas the use of an MRI-contrast agent is often helpful if the implant is localized close to vessels [19]. Caution should always be exercised when differentiating blood vessels and fibrous septa from the Implanon rod on the MRI scans [11]. However, even though MRI localizes the implants accu-
Ultrasound and MRI should localize the vast majority of nonpalpable Implanon rods. On those rare occasions when further definitive proof of the presence or absence of Implanon is required because imaging techniques have failed to localize the rod, measuring serum ENG levels will confirm whether Implanon is in situ but will not localize its position [10,20]. For example, Kaptein and Ganpat [10] described a case of a woman whose Implanon could not be visualized using ultrasound scans. A negative serum ENG level confirmed the absence of Implanon by demonstrating undetectable levels of the active component of Implanon, ENG. Determination of serum ENG levels can be carried out by any local Organon affiliate. 3. Clinical guidelines Implanon is a single-rod, progestin-only, implantable subdermal contraceptive that has been used widely throughout the world and that provides reliable contraceptive protection for up to 3 years. In contrast to multiple-rod systems, such as the six-capsule levonorgestrel implants, the advantages of the single-rod Implanon is that insertion and removal are relatively quick and easy, markedly reducing the potential for improper insertion and resulting in fewer complications during removal. However, if insertion is not done properly, there may be complications with removal of Implanon. It is thus essential that clinicians familiarize themselves with proper insertion techniques and that they work in close liaison with radiologists to localize any nonpalpable implants by ultrasound and, if necessary, by MRI scanning techniques [19,20]. In addition, we strongly recommend that clinicians do not attempt to remove a deeply implanted Implanon rod without first localizing it as described hereinbefore. We also recommend that they coordinate care with radiologists who have the proper equipment. Once the implant has been localized, it is strongly recommended not to put off its removal, but rather, to remove it immediately following localization; this approach will also minimize potential problems [6].
4. Conclusion Meticulous insertion technique will minimize difficulties at the time of Implanon removal. In the unlikely event that an Implanon rod cannot be localized prior to removal, close clinical coordination between women’s health care providers and radiologists is needed to minimize or prevent further complications and facilitate removal of the rod and subsequent contraceptive management of the patient.
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