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Supra-acetabular Pelvic External Fixator, Percutaneous With Fluoroscopic Guidance

Grannis, Kimberly MD*; Tidwell, John MD*; Cho, Rosa MD

Author Information
Journal of Orthopaedic Trauma: August 2018 - Volume 32 - Issue - p S14-S15
doi: 10.1097/BOT.0000000000001211

Abstract

INTRODUCTION

Pelvic fractures comprise 3%–8% of all fractures seen in the emergency department and are present in up to 25% of multiply injured patients. Of those, up to 10% of those have mechanically unstable pelvic fractures with hemodynamic instability.1 Early control of hemorrhage is critical to patient survival. External fixation is indicated for unstable pelvic ring injuries to restore rotational stability in vertically stable patterns. If a posterior ring injury exists, additional posterior stabilization is recommended. Prompt pelvic external fixation has been shown to improve mortality when part of the resuscitation protocol by means of tamponade through correction of deformity and fracture stability.2 Specifically, the supra-acetabular pelvic external fixator provides better access to the abdomen for future surgeries, is less irritating to soft tissues, and is less likely to compromise further surgical incisions compared with other constructs.3 Biomechanical studies have shown that the supra-acetabular pin construct has better sacroiliac joint stability compared with iliac crest pins. This video (see Video, Supplemental Digital Content 1, http://links.lww.com/JOT/A382) demonstrates 1 method of supra-acetabular pelvic external fixation using fluoroscopic guidance.

METHODS

Preoperative Planning

It is helpful to obtain a preoperative computed tomography scan with 3D imaging, as well as inlet/outlet pelvic films, to evaluate the extent of pelvic ring injury. Keep in mind that external fixation may be definitive fixation if the patient is too unstable to return to the operating room. If that is the case, consider using hydroxyapatite-coated pins. The patient is positioned on a flat radiolucent table with a Foley catheter to decompress the bladder. Consider using a pillow under the knees to gently flex hips and relax anterior neurovascular structures. Bilateral sequential compression devices are recommended for deep vein thrombosis prevention. Relevant images should be taken before the patient is prepped and draped to ensure that there are no barriers to obtaining intraoperative films, and adjustments can be made as needed before the field is sterile.

Procedure

The patient is prepped and draped in a sterile fashion with iodine-impregnated incision drape covering the inguinal region. Palpate the anterior superior iliac spine and find the anterior inferior iliac spine (AIIS) approximately 2 cm distal and 2 cm medial to the anterior superior iliac spine. Keep in mind that the patient's anatomy has been disturbed from the injury. Confirm the start position with the C-arm starting with the obturator outlet or tear drop view, which profiles the external and internal iliac walls. The radiograph technician can mark C-arm angles to allow quicker return to the correct position.

Make a small stab incision with a No. 15 blade along Langer lines that extends medial to the expected pin site to reduce soft-tissue tension after reduction. Take care to avoid the lateral femoral cutaneous nerve.

Using a blunt instrument such as a hemostat, spread soft tissue until down on bone going rectus femoris tendon down to AIIS. Insert the triple sleeve guide consisting of an outer 5.0-mm tube, inner 3.5-mm tube, and trochar. When using hydroxyapatite-coated pins for long-term fixation, a 6.0 sleeve is needed.

Because of the sloped shape of the AIIS, the drill has a tendency to slide medially or laterally. This can be avoided by first using a 1.25 K-wire with a cannulated drill. A more caudal start point will help prevent skiving.4 A short K-wire is recommended to allow room for the C-arm. Obtain the obturator outlet and obturator inlet and iliac oblique views to confirm trajectory and advance K-wire or redirect accordingly.

Remove the inner trochar and insert a cannulated drill just superior to the AIIS aiming toward the sacroiliac joint approximately 30 degrees medially and 20 degrees cranially toward the posterior superior iliac spine. For long-term external fixation, consider a more superior start point aiming just superior to the sciatic notch for more patient-friendly position of the external fixator. Take care to avoid the sciatic notch. Insert a 5- or 6-mm diameter Schantz pin on a t-handle to the posterior ilium for best bone purchase. Be aware that the pin tends to exit on the lateral iliac wing. Repeat on the contralateral side.

Place clamps on the outside of pins for better compression through the pelvis. Attach two rods with a center rod connector with adequate room for the abdomen when the patient is seated, as well as room to all for swelling to prevent skin necrosis. The compression/distraction device can be used for additional pelvic reduction if needed.

Postoperative Care

The patient is allowed toe-touch weight bearing on the unstable side for 8–12 weeks. A compression dressing around the pins is recommended to prevent drainage while the patient is mobilizing. Routine pin site care should be performed to prevent infection and ensure that the skin surrounding the pin is not under tension. Plan to return to the operating room for definitive fixation. Most modern external fixation systems are magnetic resonance imaging compatible.

CONCLUSIONS

Application of a supra-acetabular external fixator with the use of fluoroscopic guidance is a safe and effective way to achieve provisional reduction and stability in patients with unstable pelvic ring injuries.5,6

REFERENCES

1. Weis DA. Master techniques in orthopaedicsurgery. In: Pelvic Fractures: External Fixation. Chap 37. Philidelphia PA: Lippincott Williams & Wilkins; 2013:745–770.
2. Riemer BL, Butterfield SL, Diamond DL, et al. Acute mortality associated with injuries to the pelvic ring: the role of early patient mobilization and external fixation. J Trauma. 1993;35:671–677.
3. Kim WY, Hearn TC, Seleem O, et al. Effect of pin location on stability of pelvic external fixation. ClinOrthop. 1999;361:237–244.
4. Calafi LA, Routt ML. Anterior pelvic external fixation: is there an optimal placement for the supra-acetabular pin? Am J Orthop. 2013;42:E125–E127.
5. White E, Hsu JR, Holcomb JB. Hemodynamically unstable pelvic fractures. Injury. 2009;40:1023–1030.
6. Stahel PF, Mauffrey C, Smith WR, et al. External fixation for acute pelvic ring injuries: decision making and technical options. J Trauma Acute Care Surg. 2013;75:882–887.
Keywords:

pelvic ring; external fixator; technique; fracture; supra-acetabular

Supplemental Digital Content

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