- Email: [email protected]
Ultrasound-guided supra-acetabular pelvic external fixator (US-SA FIX)
Injury, Int. J. Care Injured 50S (2019) S24–S29
Contents lists available at ScienceDirect
Injury journal homepage: www.elsevier.com/locate/injury
Ultrasound-guided supra-acetabular pelvic external fixator (US-SA FIX) Manuel Cuervas-Monsa,b , Coral Sánchez-Péreza,b , Juan Arnal-Burróa,b , Javier Vaquero-Martína,b , Francisco Chana-Rodrígueza,b,* a b
Department of Traumatology and Orthopaedic Surgery, General University Hospital “Gregorio Marañón”, Spain Department of Surgery, Complutense University of Madrid, Spain
A R T I C L E I N F O
A B S T R A C T
Article history: Received 23 February 2019 Accepted 28 March 2019
Background: Between the different options in pelvic external fixation, the supra-acetabular pin placement is considered the best option by many authors. The aim of this study is to describe the surgical technique of the ultrasound-guided supra-acetabular pelvic external fixator (US-SA FIX). Surgical technique: Description of the steps to perform the US-SA FIX technique. Discussion: The supra-acetabular pin placement is considered the best option and it is the most wildly used because it combines three crucial qualities: safety, simplicity, and effectiveness. Notwithstanding, when a severely multiple injured patient arrives at the emergency room we need to perform an emergency external fixation, however trained x-ray technicians or pelvic surgeons are not always present, making it difficult to perform the surgery with the proper intra-operative imaging, increasing the surgical time with potentially serious repercussions, a case scenario where the ultrasound can be a very helpful tool. Ultrasound-guided supra-acetabular pelvic external fixator pin placement is feasible without compromising the reliability of its placement, and the application of this new technique in clinical practice in our centre brings encouraging results. © 2019 Elsevier Ltd. All rights reserved.
Keywords: Pelvic fracture Supraacetabular pinning Pelvic external fixator Ultrasound Sonography
Background
Surgical Technique
Usually presented in severely multiple injured patients, pelvic ring fracture combine low incidence with high mortality rate [1,2]. In tandem, this is a very dangerous combination for our patients, a mandatory reason for being familiar with the current gold standard treatment: damage control orthopaedics [3]. Hemodynamic instability needs effective and urgent treatment, and pelvic external fixation significantly reduce mortality rates in this patients [4]. Between the different options in pelvic external fixation, the supra-acetabular pin placement is more stable biomechanically, allow for a pelvic reduction in the transverse plane of the deformity, facilitate concurrent laparotomy procedures, and may allow an improved reduction of the posterior elements with a femoral distractor as a compressor [5,6], thus is considered the best option by many authors [5]. The aim of this study is to describe the surgical technique of the ultrasound-guided supra-acetabular pelvic external fixator (US-SA FIX).
Preoperative work up
* Corresponding author at: Hospital General Universitario Gregorio Marañón, c/ Dr. Esquerdo 46. 28007, Madrid, Spain. E-mail address: [email protected] (F. Chana-Rodríguez). https://doi.org/10.1016/j.injury.2019.03.050 0020-1383/© 2019 Elsevier Ltd. All rights reserved.
Before we perform the procedure, anteroposterior pelvic radiographs are mandatory. If it possible, oblique views and/or computed tomography are very useful. Shaving of the surgical field is done if necessary, and Cefazolin 2 g iv is used. Anaesthesia and positioning General anaesthesia is performed, and the patient is placed in a standard supine position. The entire abdomen and bilateral flanks are prepared with iodine solution or isopropyl alcohol, and then draped. Draping and positioning of the patient so that a view of entire pelvis is possible. The equipment To perform an ultrasound-guided supra-acetabular pelvic external fixator (US-SA Fix) procedure, you will need the following equipment: - Complete fixator set with 180 x 6 mm self-drilling pins.
M. Cuervas-Mons et al. / Injury, Int. J. Care Injured 50S (2019) S24–S29
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- Ultrasound system with linear array transducer. - Basic surgical instrumental (blade No.24, mosquito forceps, ...) - 22 G 1/2 needle. - Electric motor. In our centre, we use the Hoffman1 II external fixation system (Stryker1; Kalamazoo, MI, USA) and the M-Turbo1 ultrasound system (Sonosite1; Fujifilm1, Minato, Tokyo, Japan) with a linear transducer with 7- to 15-MHz frequencies. The anatomy and exposure The starting point for supraacetabular pins is the anterior inferior iliac spine (AIIS) [7], but sometimes it is difficult to localize by manual palpation, reason why we recommend starting by locating the anterior superior iliac spine (ASIS) and then carry down to the AIIS. The ASIS is localized by manual palpation; in case of obese patients it may be necessary to use ultrasound to localize the ASIS. The transducer is positioned perpendicular to ASIS to obtain a coronal view (Fig. 1), and carried down to the anterior inferior iliac spine (AIIS). Once the AIIS is located, the point is marked with a 22 G 1/2 needle. Afterwards, the transducer is placed parallel to the innominate line, obtaining a sagittal view of the AIIS and searching for the exact half-pin introduction point at 6 mm from the AIIS tip, modifying the needle position if necessary (Fig. 2). Subsequently, a 10 mm transverse skin incision is made around the needle, with surgical scalpel blade No.24. Blunt dissection is then carried down, using a mosquito forceps in longitudinal direction, up to the fascia between the tensor fascia lata and the sartorius muscles. The fascia is open and blunt dissection is carried down until the AIIS is palpated. The lateral femoral cutaneous nerve is just lateral to this interval, and it can be visualized with US, but in our opinion it is not necessary if a blunt dissection is carried down and soft tissue protector is used to avoid LCFN injuries. Imaging We use the US to localize and verify the starting point in the AIIS. Once it has been localized, the half-pin position is confirmed ultrasonically in both planes and the distance from the hip is measured, modifying the position if is under 20 mm [7] to avoid intraarticular positioning. Afterwards the double check (coronal
Fig. 1. US transducer perpendicular to ASIS to obtain coronal view.
Fig. 2. US transducer parallel to the innominate line to obtain a sagittal view.
and sagittal views) is done, the transducer is positioned in sagittal plane and under ultrasound control a 180 x 6 mm self-drilling pin is placed immediately below the AIIS tip (Fig. 3). Half-pin insertion The 6 mm half-pin is introduced using an electric motor, with 20 degrees medial inclination in the sagittal plane and 70-80 degrees in a cephalad direction [8]. The acetabular edge and femoral head must be visualized with sonography to check the extra-articular half-pin placing. The thread of the pin is sunk down to the bone, leaving the long shank above the level of the skin to allow the reduction and the external fixator construct. The same steps are repeated for half-pin insertion in the opposite hemipelvis. (Fig. 4). Reduction After the two half-pin insertions, the external fixator is assembled using clamps and connecting bars. The reduction can be either achieved or refined using the pins as manipulation devices prior to frame assembly.
Fig. 3. US-guided pinning below the AIIS tip.
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Fig. 5. Iliac anterior external fixation.
Fig. 4. US-guided supraacetabular pinning.
Discussion Damage control orthopaedics The current gold standard treatment for patients with pelvic ring fracture with hemodynamic instability is damage control orthopaedics [3]. Hemodynamic instability in patients with pelvic ring fractures needs urgent treatment, and pelvic external fixation in emergency room has been a crucial factor to reduce bleeding mortality [4,9]. Nevertheless, we can find different options of external stabilization of pelvic injuries: non-invasive techniques, anterior external fixation, posterior external fixation, ... [10] Choosing the best treatment for our patient Non-invasive techniques, such as pelvic binder or bed sheets, can be used initially, but they are not an adequate midterm treatment, this is the reason why most authors recommend invasive techniques in order to set and stabilize the fractured fragments. Anterior external fixators have been used when pelvic posterior ring was found to be stable, but other devices such C-clamp could be required when Tile C type lesion [11] is present and no posterior stability is found. Biomechanical studies have shown that the C-clamp provides better fixation than any other pelvic fixator does, when the posterior instable pelvic injuries are concerned [10]. When an anterior external fixation is needed, it can be placed in three different percutaneous positions: transiliac, sub-iliac or supra-acetabular. The iliac or transiliac external fixation is the classic method, where the pins are placed anteriorly through the wings of the iliac bone (Fig. 5). A total of three pins in each hemipelvises are used, with 4 or 5 mm pins usually employed and a separation between them of 1 cm at least. Its advantages are the facility to be placed even if non-experienced surgeon is operating and the few anatomic structures at risk during placement, but the most important disadvantage is the leak of mechanical resistance, because of thin bone surface and the pins size permitted. In the sub-Iliac crest technique, know as sub-crystal, the pins are placed beneath and along the length of the iliac crests (Fig. 6). Sub-crystal external fixation has been demonstrated to be an easy way to set the external fixation without anatomical danger, except from the nerve lateral cutaneous femoral.
Fig. 6. Sub-iliac anterior external fixation.
In the supra-acetabular external fixation 6 mm pins are placed just above the hip joint, in the bone above acetabulum, a dense and solid bone area which ensures the tight grip of the pin [10], thus it has been demonstrated to be the most resistant construct (Fig. 7). Besides it is more stable biomechanically, allowing for an easier pelvic reduction thus “it is easier to close a book from the front than the top” [10], and may allow an improved reduction of the posterior elements with a femoral distractor as a compressor [5,6]. Compared to the other anterior external fixator, there are more advantages to this placement: it is more comfortable for the patient in the sitting position it facilitates concurrent laparotomy procedures, it has greater insertion depth and bigger diameter of the pins (6 mm compared to 4 or 5 mm in iliac technique), has a more even distribution of the weigh over the SI joints, greater stability in the posterior pelvic ring, lower risk of penetration and infection [10] (Fig. 8).
Fig. 7. bis. Supra-acetabular anterior external fixation.
M. Cuervas-Mons et al. / Injury, Int. J. Care Injured 50S (2019) S24–S29
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Fig. 8. Patient with supra-acetabular anterior external fixation.
Other invasive techniques such as anterior suprapubic plates or supra-acetabular pedicle screw Internal Fixation device (INFIX) are also an alternative treatment. The suprapubic plate main advantage is that the biomechanical stability achieved when plating is higher than the one obtained with other devices when Tile B lesion [11]are present, but they require more surgical time and a surgeon with high pelvic-anatomy experience. The INFIX setting is also highly technically demanding and no mechanical advantage has been found compared to supra-acetabular eternal fixation [9,12]. When a patient is brought to the emergency department with a pelvic ring fracture it is mandatory for an orthopaedic surgeon to be familiar with the damage control orthopaedics [3] in order to bring an effective and urgent treatment. A proper external fixator pin placement is an important aspect of the overall treatment strategy and preoperative planning of pelvic ring injuries [4], and between all the different options in pelvic external fixation the supra-acetabular pin placement is considered the best option for many authors [5] and it is the most wildly used because it combines three crucial qualities: safety, simplicity, and effectiveness [10].
Fig. 9. Radiological tepee view.
Solving the “X-ray problem” The technique for a supra-acetabular external fixation has been previously described [13]. Nevertheless, in this technique, fluoroscopically-guided placement of the supra-acetabular pins is recommended, in order to avoid bad positioning [14]. Some authors warns that, if there is a lack of sufficient experience, this way may have some serious risks such as hip joint penetration, lateral femoro-cutaneous nerve injury or damage to structures passing through greater sciatic notch [10,15]. A classical way for setting this construct has been with X-ray guidance following the tepee view (Fig. 9) above the acetabulum. Performing this surgery requires appropriate intra-operative imaging, where the X-ray technician training is imperative [16]. Notwithstanding, when a severely multiple injured patient arrives at the emergency room, we need to perform an emergency external fixation, however trained x-ray technicians or pelvic surgeons are not always present, making it difficult to perform the surgery with the proper intra-operative imaging (Fig. 10), increasing the surgical time with potentially serious repercussions, a case scenario where the ultrasound can be a
Fig. 10. Intraoperative tepee view with a supra-acetabular pin.
very helpful tool [17]. Despite supra-acetabular external fixation being safe, simple and effective [10] in an emergency situation supra-acetabular half-pins may not be practical for some authors [7] due to lower surgeons familiarity with the details of this complex anatomic region and the need for proper intraoperative fluoroscopy. In the unstable pelvic injury management, the anterior external fixation plays an important role, but the actual surgical techniques under fluoroscopic vision can be modified, even improved, with the incorporation of new diagnostic and therapeutic tools in the
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Fig. 11. Details of the hip surface during pin placement.
field of the Orthopaedic surgery [17]. This is the reason why we have developed the US-SA FIX technique, to eliminate the need of intraoperative fluoroscopy, but at the same time offering the ultrasound as a proper intra-operative imaging to the surgeon, thus diminishing potential risks. After our previous studies, we can conclude that ultrasound-guided supra-acetabular half-pin placement is a feasible and effective technique [17], considering that the ultrasound is a worthless tool for ensuring the extra-capsular entry point, getting excellent details of the hip surface helping the surgeon to choose the correct extra-capsular half-pin entry point (Fig. 11). Ultrasonography advantages Ultrasound-guided supra-acetabular pelvic external fixator pin placement is feasible without compromising the reliability of its placement [17] (Fig. 12). During the last years it has been a rise of percutaneous procedures [16], allowing surgical procedures to be carried out through small incisions thus causing
minimal injury to adjacent tissues, and reducing the operative trauma [18]. As a consequence of these procedures, an intraoperative radiologic monitoring is needed, and the fluoroscopy use in the operating rooms leads to an increase of X radiation exposure to the patient and operating room personnel with harmful effects on health [16,19], usually underestimated by the surgeons [16]. We have developed an ultrasound-guided surgical technique, which can help the surgeon placing a supra-acetabular external fixator, identifying pelvic bone references, besides the hip joint or the femoral neuro-vascular structures if needed, for the half-pin placement being independent from a qualified x-ray technician, thus eliminating ionizing radiations. The first step to perform the US-SA FIX technique is to identify the AIIS, a bony subcutaneous structure, very reflective in the ultrasound, which makes really easy to identify it as a defined and hyperechoic line. Once the entry point is found the surgeon may be concerned about not being able to see further than the cortical surface, but this technique, if realized with proper direction of bone pins in a safe place, can offer a safe and quick pin placement. As in the “classic” manner, the pins should be inserted with 20 degrees medial inclination in the sagittal plane and 70-80 degrees in a cephalad direction [8]. The application of this new technique in clinical practice in our centre brings encouraging results. Nonetheless, there are some cons for this technique, those related to the use of ultrasound technique. In medical imaging, ultrasonography has been used for decades and is one of the most widely used imaging modalities [20], and in contrast to X-rays it is a totally safe non-invasive imaging technique, and it provides excellent anatomical detail of the cortical surface of superficial bone [21], but its use may need a long learning curve. Investment in training is justified in light of the contribution of this technology to diagnostic and therapeutic orthopaedics [21] and even though the learning curve may be long, the extensive anatomical knowledge of the orthopaedic surgeons combined to the easily bone landmarks viewing with ultrasound make this technique a reliable and affordable tool.
Fig. 12. CT after a US-SA Fix Ex placement.
M. Cuervas-Mons et al. / Injury, Int. J. Care Injured 50S (2019) S24–S29
Conflict of interest Cuervas-Mons M, Sánchez-Pérez C, Arnal-Burró J, Vaquero J, Chana-Rodríguez F, state that none of them has a conflict of interest that relates to the content discussed in this manuscript. Acknowledgements The paper is part of a supplement based on the 2017 workshop on “External Fixation and Percutaneous Pinning.” Support for the publication of this supplement was provided by the Osteosynthesis and Trauma Care Foundation (OTCF) sponsored by a research grant from Stryker. References [1] Krettek C, Simon RG, Tscherne H. Management priorities in patients with polytrauma. Langenbecks Arch Surg 1998;383(3-4):220–7. [2] Scheyerer MJ, Zimmermann SM, Osterhoff G, et al. Anterior subcutaneous internal fixation for treatment of unstable pelvic fractures. BMC Res Notes 2014;7:133. [3] Giannoudis PV, Pape HC. Damage control orthopaedics in unstable pelvic ring injuries. Injury 2004;35(7):671–7. [4] Calafi LA, Routt ML. Anterior pelvic external fixation: is there an optimal placement for the supra-acetabular pin? Am J Orthop 2013;42(12):E125–7. [5] Gardner MJ, Nork SE. Stabilization of unstable pelvic fractures with supraacetabular compression external fixation. J Orthop Trauma 2007;21 (4):269–73. [6] Kim WY, Hearn TC, Seleem O, Mahalingam E, Stephen D, Tile M. Effect of pin location on stability of pelvic external fixation. Clin Orthop Relat Res 1999; (361):237–44. [7] Haidukewych GJ, Kuma S, Prpa B. Placement of half-pins for supraacetabular external fixation: an anatomic study. Clin Orthop Relat Res 2003;(411):269–73.
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[8] Penning D, Gausepohl T. External fixation in pelvic ring injuries: the pelvic fixator. In: De Bastiani G, Apley AG, Goldberg A, editors. Orthofix external fixation in trauma and orthopaedics. London: Springer-Verlag; 2000. p. 219–35. [9] Hsu SD, Chen CJ, Chou YC, Wang SH, Chan DC. Effect of early pelvic binder use in the emergency management of suspected pelvic trauma: a retrospective cohort study. Int J Environ Res Public Health 2017;14(10). [10] Apostolov P, Burnev M, Milkov P. Methods and techniques of percutaneous external fixation in pelvic fractures. JofIMAB 2011;17:166–71. [11] Tile M. Classification. In: Tile M, editor. Fractures of the Pelvis and Acetabulum. Baltimore: Williams and Wilkins; 1995. p. 66–101. [12] Vaidya R, Tonnos F, Nasr K, Kanneganti P, Curtis G. The anterior subcutaneous pelvic fixator (INFIX) in an anterior posterior compression type 3 pelvic fracture. J Orthop Trauma 2016;30(Suppl. 2):S21–2. [13] Tile M. Pelvic ring fractures: should they be fixed? J Bone Joint Surg Br 1988;70 (1):1–12. [14] Tile M. The management of unstable injuries of the pelvic ring. J Bone Joint Surg Br 1999;81(6):941–3. [15] Gänsslen A, Pohlemann T, Krettek C. Supraacetabular external fixation for pelvic ring fractures. Eur J Trauma. 2006;32(5):489–99. [16] Torres-Torres M, Mingo-Robinet J, Moreno Barrero M, et al. [Radiation safety in orthopaedic operating theatres. what is the current situation?]. Rev Esp Cir Ortop Traumatol 2014;58(5):309–13. [17] Chana-Rodriguez F, Cuervas-Mons M, Rojo-Manaute J, Mora F, Arnal J, et al. Ultrasound-guided supra-acetabular pin placement in pelvic external fixation: description of a surgical technique and results. Injury 2017;48 (Suppl. 6):S66–74. [18] Giannini S, Cavallo M, Faldini C, Luciani D, Vannini F. The SERI distal metatarsal osteotomy and Scarf osteotomy provide similar correction of hallux valgus. Clin Orthop Relat Res 2013;471(7):2305–11. [19] Shore RE, Neriishi K, Nakashima E. Epidemiological studies of cataract risk at low to moderate radiation doses: (not) seeing is believing. Radiat Res 2010;174 (6):889–94. [20] Hangiandreou NJ. AAPM/RSNA physics tutorial for residents. Topics in US: Bmode US: basic concepts and new technology. Radiographics 2003;23 (4):1019–33. [21] Blankstein A. Ultrasound in the diagnosis of clinical orthopedics: the orthopedic stethoscope. World J Orthop 2011;2(2):13–24.
Contents lists available at ScienceDirect
Injury journal homepage: www.elsevier.com/locate/injury
Ultrasound-guided supra-acetabular pelvic external fixator (US-SA FIX) Manuel Cuervas-Monsa,b , Coral Sánchez-Péreza,b , Juan Arnal-Burróa,b , Javier Vaquero-Martína,b , Francisco Chana-Rodrígueza,b,* a b
Department of Traumatology and Orthopaedic Surgery, General University Hospital “Gregorio Marañón”, Spain Department of Surgery, Complutense University of Madrid, Spain
A R T I C L E I N F O
A B S T R A C T
Article history: Received 23 February 2019 Accepted 28 March 2019
Background: Between the different options in pelvic external fixation, the supra-acetabular pin placement is considered the best option by many authors. The aim of this study is to describe the surgical technique of the ultrasound-guided supra-acetabular pelvic external fixator (US-SA FIX). Surgical technique: Description of the steps to perform the US-SA FIX technique. Discussion: The supra-acetabular pin placement is considered the best option and it is the most wildly used because it combines three crucial qualities: safety, simplicity, and effectiveness. Notwithstanding, when a severely multiple injured patient arrives at the emergency room we need to perform an emergency external fixation, however trained x-ray technicians or pelvic surgeons are not always present, making it difficult to perform the surgery with the proper intra-operative imaging, increasing the surgical time with potentially serious repercussions, a case scenario where the ultrasound can be a very helpful tool. Ultrasound-guided supra-acetabular pelvic external fixator pin placement is feasible without compromising the reliability of its placement, and the application of this new technique in clinical practice in our centre brings encouraging results. © 2019 Elsevier Ltd. All rights reserved.
Keywords: Pelvic fracture Supraacetabular pinning Pelvic external fixator Ultrasound Sonography
Background
Surgical Technique
Usually presented in severely multiple injured patients, pelvic ring fracture combine low incidence with high mortality rate [1,2]. In tandem, this is a very dangerous combination for our patients, a mandatory reason for being familiar with the current gold standard treatment: damage control orthopaedics [3]. Hemodynamic instability needs effective and urgent treatment, and pelvic external fixation significantly reduce mortality rates in this patients [4]. Between the different options in pelvic external fixation, the supra-acetabular pin placement is more stable biomechanically, allow for a pelvic reduction in the transverse plane of the deformity, facilitate concurrent laparotomy procedures, and may allow an improved reduction of the posterior elements with a femoral distractor as a compressor [5,6], thus is considered the best option by many authors [5]. The aim of this study is to describe the surgical technique of the ultrasound-guided supra-acetabular pelvic external fixator (US-SA FIX).
Preoperative work up
* Corresponding author at: Hospital General Universitario Gregorio Marañón, c/ Dr. Esquerdo 46. 28007, Madrid, Spain. E-mail address: [email protected] (F. Chana-Rodríguez). https://doi.org/10.1016/j.injury.2019.03.050 0020-1383/© 2019 Elsevier Ltd. All rights reserved.
Before we perform the procedure, anteroposterior pelvic radiographs are mandatory. If it possible, oblique views and/or computed tomography are very useful. Shaving of the surgical field is done if necessary, and Cefazolin 2 g iv is used. Anaesthesia and positioning General anaesthesia is performed, and the patient is placed in a standard supine position. The entire abdomen and bilateral flanks are prepared with iodine solution or isopropyl alcohol, and then draped. Draping and positioning of the patient so that a view of entire pelvis is possible. The equipment To perform an ultrasound-guided supra-acetabular pelvic external fixator (US-SA Fix) procedure, you will need the following equipment: - Complete fixator set with 180 x 6 mm self-drilling pins.
M. Cuervas-Mons et al. / Injury, Int. J. Care Injured 50S (2019) S24–S29
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- Ultrasound system with linear array transducer. - Basic surgical instrumental (blade No.24, mosquito forceps, ...) - 22 G 1/2 needle. - Electric motor. In our centre, we use the Hoffman1 II external fixation system (Stryker1; Kalamazoo, MI, USA) and the M-Turbo1 ultrasound system (Sonosite1; Fujifilm1, Minato, Tokyo, Japan) with a linear transducer with 7- to 15-MHz frequencies. The anatomy and exposure The starting point for supraacetabular pins is the anterior inferior iliac spine (AIIS) [7], but sometimes it is difficult to localize by manual palpation, reason why we recommend starting by locating the anterior superior iliac spine (ASIS) and then carry down to the AIIS. The ASIS is localized by manual palpation; in case of obese patients it may be necessary to use ultrasound to localize the ASIS. The transducer is positioned perpendicular to ASIS to obtain a coronal view (Fig. 1), and carried down to the anterior inferior iliac spine (AIIS). Once the AIIS is located, the point is marked with a 22 G 1/2 needle. Afterwards, the transducer is placed parallel to the innominate line, obtaining a sagittal view of the AIIS and searching for the exact half-pin introduction point at 6 mm from the AIIS tip, modifying the needle position if necessary (Fig. 2). Subsequently, a 10 mm transverse skin incision is made around the needle, with surgical scalpel blade No.24. Blunt dissection is then carried down, using a mosquito forceps in longitudinal direction, up to the fascia between the tensor fascia lata and the sartorius muscles. The fascia is open and blunt dissection is carried down until the AIIS is palpated. The lateral femoral cutaneous nerve is just lateral to this interval, and it can be visualized with US, but in our opinion it is not necessary if a blunt dissection is carried down and soft tissue protector is used to avoid LCFN injuries. Imaging We use the US to localize and verify the starting point in the AIIS. Once it has been localized, the half-pin position is confirmed ultrasonically in both planes and the distance from the hip is measured, modifying the position if is under 20 mm [7] to avoid intraarticular positioning. Afterwards the double check (coronal
Fig. 1. US transducer perpendicular to ASIS to obtain coronal view.
Fig. 2. US transducer parallel to the innominate line to obtain a sagittal view.
and sagittal views) is done, the transducer is positioned in sagittal plane and under ultrasound control a 180 x 6 mm self-drilling pin is placed immediately below the AIIS tip (Fig. 3). Half-pin insertion The 6 mm half-pin is introduced using an electric motor, with 20 degrees medial inclination in the sagittal plane and 70-80 degrees in a cephalad direction [8]. The acetabular edge and femoral head must be visualized with sonography to check the extra-articular half-pin placing. The thread of the pin is sunk down to the bone, leaving the long shank above the level of the skin to allow the reduction and the external fixator construct. The same steps are repeated for half-pin insertion in the opposite hemipelvis. (Fig. 4). Reduction After the two half-pin insertions, the external fixator is assembled using clamps and connecting bars. The reduction can be either achieved or refined using the pins as manipulation devices prior to frame assembly.
Fig. 3. US-guided pinning below the AIIS tip.
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Fig. 5. Iliac anterior external fixation.
Fig. 4. US-guided supraacetabular pinning.
Discussion Damage control orthopaedics The current gold standard treatment for patients with pelvic ring fracture with hemodynamic instability is damage control orthopaedics [3]. Hemodynamic instability in patients with pelvic ring fractures needs urgent treatment, and pelvic external fixation in emergency room has been a crucial factor to reduce bleeding mortality [4,9]. Nevertheless, we can find different options of external stabilization of pelvic injuries: non-invasive techniques, anterior external fixation, posterior external fixation, ... [10] Choosing the best treatment for our patient Non-invasive techniques, such as pelvic binder or bed sheets, can be used initially, but they are not an adequate midterm treatment, this is the reason why most authors recommend invasive techniques in order to set and stabilize the fractured fragments. Anterior external fixators have been used when pelvic posterior ring was found to be stable, but other devices such C-clamp could be required when Tile C type lesion [11] is present and no posterior stability is found. Biomechanical studies have shown that the C-clamp provides better fixation than any other pelvic fixator does, when the posterior instable pelvic injuries are concerned [10]. When an anterior external fixation is needed, it can be placed in three different percutaneous positions: transiliac, sub-iliac or supra-acetabular. The iliac or transiliac external fixation is the classic method, where the pins are placed anteriorly through the wings of the iliac bone (Fig. 5). A total of three pins in each hemipelvises are used, with 4 or 5 mm pins usually employed and a separation between them of 1 cm at least. Its advantages are the facility to be placed even if non-experienced surgeon is operating and the few anatomic structures at risk during placement, but the most important disadvantage is the leak of mechanical resistance, because of thin bone surface and the pins size permitted. In the sub-Iliac crest technique, know as sub-crystal, the pins are placed beneath and along the length of the iliac crests (Fig. 6). Sub-crystal external fixation has been demonstrated to be an easy way to set the external fixation without anatomical danger, except from the nerve lateral cutaneous femoral.
Fig. 6. Sub-iliac anterior external fixation.
In the supra-acetabular external fixation 6 mm pins are placed just above the hip joint, in the bone above acetabulum, a dense and solid bone area which ensures the tight grip of the pin [10], thus it has been demonstrated to be the most resistant construct (Fig. 7). Besides it is more stable biomechanically, allowing for an easier pelvic reduction thus “it is easier to close a book from the front than the top” [10], and may allow an improved reduction of the posterior elements with a femoral distractor as a compressor [5,6]. Compared to the other anterior external fixator, there are more advantages to this placement: it is more comfortable for the patient in the sitting position it facilitates concurrent laparotomy procedures, it has greater insertion depth and bigger diameter of the pins (6 mm compared to 4 or 5 mm in iliac technique), has a more even distribution of the weigh over the SI joints, greater stability in the posterior pelvic ring, lower risk of penetration and infection [10] (Fig. 8).
Fig. 7. bis. Supra-acetabular anterior external fixation.
M. Cuervas-Mons et al. / Injury, Int. J. Care Injured 50S (2019) S24–S29
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Fig. 8. Patient with supra-acetabular anterior external fixation.
Other invasive techniques such as anterior suprapubic plates or supra-acetabular pedicle screw Internal Fixation device (INFIX) are also an alternative treatment. The suprapubic plate main advantage is that the biomechanical stability achieved when plating is higher than the one obtained with other devices when Tile B lesion [11]are present, but they require more surgical time and a surgeon with high pelvic-anatomy experience. The INFIX setting is also highly technically demanding and no mechanical advantage has been found compared to supra-acetabular eternal fixation [9,12]. When a patient is brought to the emergency department with a pelvic ring fracture it is mandatory for an orthopaedic surgeon to be familiar with the damage control orthopaedics [3] in order to bring an effective and urgent treatment. A proper external fixator pin placement is an important aspect of the overall treatment strategy and preoperative planning of pelvic ring injuries [4], and between all the different options in pelvic external fixation the supra-acetabular pin placement is considered the best option for many authors [5] and it is the most wildly used because it combines three crucial qualities: safety, simplicity, and effectiveness [10].
Fig. 9. Radiological tepee view.
Solving the “X-ray problem” The technique for a supra-acetabular external fixation has been previously described [13]. Nevertheless, in this technique, fluoroscopically-guided placement of the supra-acetabular pins is recommended, in order to avoid bad positioning [14]. Some authors warns that, if there is a lack of sufficient experience, this way may have some serious risks such as hip joint penetration, lateral femoro-cutaneous nerve injury or damage to structures passing through greater sciatic notch [10,15]. A classical way for setting this construct has been with X-ray guidance following the tepee view (Fig. 9) above the acetabulum. Performing this surgery requires appropriate intra-operative imaging, where the X-ray technician training is imperative [16]. Notwithstanding, when a severely multiple injured patient arrives at the emergency room, we need to perform an emergency external fixation, however trained x-ray technicians or pelvic surgeons are not always present, making it difficult to perform the surgery with the proper intra-operative imaging (Fig. 10), increasing the surgical time with potentially serious repercussions, a case scenario where the ultrasound can be a
Fig. 10. Intraoperative tepee view with a supra-acetabular pin.
very helpful tool [17]. Despite supra-acetabular external fixation being safe, simple and effective [10] in an emergency situation supra-acetabular half-pins may not be practical for some authors [7] due to lower surgeons familiarity with the details of this complex anatomic region and the need for proper intraoperative fluoroscopy. In the unstable pelvic injury management, the anterior external fixation plays an important role, but the actual surgical techniques under fluoroscopic vision can be modified, even improved, with the incorporation of new diagnostic and therapeutic tools in the
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Fig. 11. Details of the hip surface during pin placement.
field of the Orthopaedic surgery [17]. This is the reason why we have developed the US-SA FIX technique, to eliminate the need of intraoperative fluoroscopy, but at the same time offering the ultrasound as a proper intra-operative imaging to the surgeon, thus diminishing potential risks. After our previous studies, we can conclude that ultrasound-guided supra-acetabular half-pin placement is a feasible and effective technique [17], considering that the ultrasound is a worthless tool for ensuring the extra-capsular entry point, getting excellent details of the hip surface helping the surgeon to choose the correct extra-capsular half-pin entry point (Fig. 11). Ultrasonography advantages Ultrasound-guided supra-acetabular pelvic external fixator pin placement is feasible without compromising the reliability of its placement [17] (Fig. 12). During the last years it has been a rise of percutaneous procedures [16], allowing surgical procedures to be carried out through small incisions thus causing
minimal injury to adjacent tissues, and reducing the operative trauma [18]. As a consequence of these procedures, an intraoperative radiologic monitoring is needed, and the fluoroscopy use in the operating rooms leads to an increase of X radiation exposure to the patient and operating room personnel with harmful effects on health [16,19], usually underestimated by the surgeons [16]. We have developed an ultrasound-guided surgical technique, which can help the surgeon placing a supra-acetabular external fixator, identifying pelvic bone references, besides the hip joint or the femoral neuro-vascular structures if needed, for the half-pin placement being independent from a qualified x-ray technician, thus eliminating ionizing radiations. The first step to perform the US-SA FIX technique is to identify the AIIS, a bony subcutaneous structure, very reflective in the ultrasound, which makes really easy to identify it as a defined and hyperechoic line. Once the entry point is found the surgeon may be concerned about not being able to see further than the cortical surface, but this technique, if realized with proper direction of bone pins in a safe place, can offer a safe and quick pin placement. As in the “classic” manner, the pins should be inserted with 20 degrees medial inclination in the sagittal plane and 70-80 degrees in a cephalad direction [8]. The application of this new technique in clinical practice in our centre brings encouraging results. Nonetheless, there are some cons for this technique, those related to the use of ultrasound technique. In medical imaging, ultrasonography has been used for decades and is one of the most widely used imaging modalities [20], and in contrast to X-rays it is a totally safe non-invasive imaging technique, and it provides excellent anatomical detail of the cortical surface of superficial bone [21], but its use may need a long learning curve. Investment in training is justified in light of the contribution of this technology to diagnostic and therapeutic orthopaedics [21] and even though the learning curve may be long, the extensive anatomical knowledge of the orthopaedic surgeons combined to the easily bone landmarks viewing with ultrasound make this technique a reliable and affordable tool.
Fig. 12. CT after a US-SA Fix Ex placement.
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