Imaging review of percutaneous pelvic fracture fixation. Manickam Kumaravel MD Haider Virani MD Nicholas Beckmann MD Susanna Spence MD

Transcription

1 Imaging review of percutaneous pelvic fracture fixation Manickam Kumaravel MD Haider Virani MD Nicholas Beckmann MD Susanna Spence MD

2 No financial disclosures

3 Introduction Most injuries to the pelvis occur as a result of high-energy trauma. The mortality rate ranges from 10-20% and is due to hemorrhage and concurrent head and/or thoracic injury. (1) Classical fixation techniques involving malleable plates and screws require an open approach that exposes much of the pelvis. In turn, this exposure may result in infection, damage to neurovascular structures, and/or delayed wound healing. (1) On the other hand, percutaneous pelvic fracture fixation offers reduced exposure related complications associated with classical techniques, shorter surgical times, and quicker weight-bearing. A thorough understanding of pelvic anatomy is necessary before fluoroscopically assisted percutaneous fixation is attempted.

4 The pelvis as a ring (2) The bony pelvis is a ring like structure composed of the sacrum, ischia, iliac, and pubic bones. The ischia, iliac and pubic bones are fused together at the acetabulum and the ischia and pubic bones have a second point of fusion at the inferior aspect of the obturator ring or inferior pubic ramus. In the setting of trauma, disruptions of the pelvic ring may be classified biomechanically, however for the purposes of percutaneous fixation the pelvic ring may be thought of as two arches, an anterior arch and a posterior arch. The posterior arch is composed of the ilac bones joined to the sacrum by the sacroiliac joints. The anterior arch consists of the pubic and ischial bones joined by the symphysis pubis. Three broad biomechanical classifications of pelvic fractures are lateral compression, anteroposterior compression, and vertical shear. Each of these three categories have subtypes that are beyond the scope of this exhibit.

5 Pelvic Anatomy Sacral neural foramen Sacrum Sacroiliac joint Iliac bone Anterior superior iliac spine Superior pubic ramus Anterior inferior iliac spine Acetabulum Supra-acetabular region Femoral head Ischium Inferior pubic ramus Pubic tubercle Pubic body

6 Pelvic views in 3D Obturator oblique view demonstrates right obturator ring and left iliac wing Inlet view demonstrates anterior margin of the sacrum and AP margins of the superior pubic ramus Obturator oblique view demonstrates left obturator ring and right iliac wing Outlet view demonstrates superior margin of the superior pubic ramus and with AP rotation different neural forminal levels are visualized

7 Pelvic Fracture due to Lateral Compression Fracture extending across the sacral neural formina and into the sacral ala superolaterally Oblique fractures of the superior and inferior pubic rami

8 Pelvic Fractures due to Anteroposterior Compression Widening of the sacroiliac joints Sacral ala fracture Fractures of the superior and inferior pubic rami Diastasis of the symphasis pubis

9 Pelvic Fracture with Vertical Shear L5 transverse process fracture Widening of the sacroiliac joint Sacral fracture with superior displacement of the right hemipelvis Fractures of the superior and inferior pubic rami Diastasis of the symphasis pubis

10 Pelvic Fracture with prominent Iliac Component Iliac wing fracture Minimally displaced superior pubic ramus fractures

11 Percutaneous Fixation For purposes of pelvic fracture fixation, pelvic ring disruptions can be divided into anterior and posterior. Anterior pelvic ring disruptions may involve percutaneous screw fixation of the fractured superior pubic ramus using either an antegrade or retrograde approach. Disruptions of the posterior pelvic ring amenable to percutaneous screw fixation include sacral fractures, iliac fractures, and sacroiliac joint disruption or fracture-dislocation (crescent fracture).

12 Percutaneous Fixation Contraindications Some contraindications to percutaneous screw fixation include (1): Anterior pelvic ring disruptions Excessively thick soft tissues due to obesity, thick gluteal musculature, soft tissue swelling. Significant curvature of the superior pubic ramus. Diastasis of the pubic symphysis may require plating in addition to superior pubic ramus screw placement. Posterior pelvic ring disruptions Comminution of the iliac wing may preclude percutaneous screw fixation as plating is required. Abnormal curvature of the sacral promontory precludes percutaneous fixation

13 Anterior pelvic ring fixation Fluoroscopic inlet and hybrid obturator/outlet views are necessary to define anteroposterior and craniocaudal margins of the superior pubic ramus, respectively. Prior to fixation, the fracture must be reduced using either a closed or open technique. (3&4) A retrograde screw inserts inferior to the pubic tubercle and just lateral to the symphysis pubis and extends laterally through the superior pubic ramus. Alternatively, a retrograde screw may be inserted from the contralateral pubic tubercle extending through the symphysis pubis and into the superior pubic ramus in cases of ipsilateral pubic body comminution. (3) An antegrade screw inserts approximately 1 to 2cm above the acetabulum and extends medially towards the symphysis pubis. (4)

14 Retrograde Technique Fluoroscopic obturator oblique view Fluoroscopic inlet views Multiple intraoperative fluoroscopic images demonstrate the placement of a retrograde screw that fixates a left superior pubic ramus fracture. The fully threaded cannulated screw spans from a start point inferior to the pubic tubercle and lateral to the symphasis pubis to an end point at the supra-acetabular region.

15 Pre and Post Retrograde Fixation 3D view of a lateral compression pelvic fracture Fluoroscopic inlet view Fluoroscopic outlet view AP view x-ray

16 Antegrade Technique Multiple intraoperative fluoroscopic images demonstrate the placement of an antegrade screw that fixates a left superior pubic ramus fracture. The fully threaded cannulated screw spans from a start point at the supra-acetabular region to an end point at the left pubic body. Fluoroscopic inlet views Fluoroscopic outlet views

17 Pre and Post Antegrade Fixation 3D view of an anteroposterior compression pelvic fracture AP view x-ray demonstrating the left superior and inferior pubic rami fractures with diastasis of the symphysis pubis and sacroiliac joints AP view x-ray demonstrating placement of an antegrade superior pubic ramus screw

18 Posterior pelvic ring fixation flouroscopy Fluoroscopic inlet, outlet, and lateral sacral views are used to achieve percutaneous fixation of sacral fractures and sacroiliac disruption/fracture. The inlet views define the anterior margin of the sacral ala and upper sacral vertebral segment. The outlet views allow visualization of the upper segment neural formina when the superior aspect of the pubic symphysis is superimposed over the second sacral segment. The lateral view demonstrates the position of the spinal canal. Fluoroscopic hybrid obturator oblique/outlet, hybrid obturator oblique/inlet, and iliac oblique are used to achieve fixation of iliac fractures from anterior inferior iliac spine to the posterior ilium. Iliac crest fractures require customized imaging to accommodate for patient specific crest morphology.

19 Posterior pelvic ring fixation Sacroiliac joint disruptions - Iliosacral screws extend medially towards the upper segment sacral vertebral body from the posterolateral iliac bone while oriented perpendicular to the non-chondral sacroiliac joint. Sacral fractures Iliosacral screws extend medially towards the vertebral body while oriented perpendicular to the fracture. Iliosacral screws may also span the entire sacrum in patients with sacral fractures and bilateral sacroiliac joint disruptions. Additional obturator oblique views are obtained to ensure appropriate screw position and length. Iliac wing fractures A screw extends posteriorly through the anterior inferior iliac spine and above the greater sciatic notch to terminate at the posterior iliac spine. Iliac crest fractures will not be discussed.

20 Sacroiliac Fixation Technique Multiple intraoperative fluoroscopic images demonstrate the placement of an iliosacral screw that fixates a left sacral ala fracture. The fully threaded cannulated screw spans from a start point at the posterolateral iliac bone to an end point at the first sacral vertebral segment. Fluoroscopic inlet views Fluoroscopic lateral view Fluoroscopic outlet views Fluoroscopic obturator oblique view

21 Sacroiliac Fixation Technique Fluoroscopic outlet views Fluoroscopic outlet views Fluoroscopic obturator oblique views Multiple intraoperative fluoroscopic images demonstrate the placement of an iliosacral screw that fixates the disrupted bilateral sacroiliac joints. The fully threaded cannulated screw spans the second sacral segment from a start point at the left posterolateral iliac bone to an end point at the contralateral posterolateral iliac bone.

22 Post Sacroiliac Fixation AP view pelvic x-ray demonstrating the left first sacral segment iliosacral screw and a second iliosacral screw spanning the second sacral segment. Outlet view pelvic x-ray demonstrating the appropriate positioning of the left iliosacral screw as it passes superior to the sacral neural foramen. Inlet view pelvic x-ray demonstrating no breach of the anterior cortex of the sacrum by the iliosacral screw.

23 Iliac Wing Fracture Mildly comminuted Iliac wing fracture Minimally displaced superior pubic ramus fractures

24 Iliac Wing Fracture Fixation Multiple intraoperative fluoroscopic images demonstrate the placement of a partially threaded cannulated screw that extends from the anterior inferior iliac spine to the posterior iliac spine. Fluoroscopic lateral view Fluoroscopic obturator oblique views Fluoroscopic obturator oblique views

25 Pre and Post Iliac Wing Fracture Fixation Preoperative pelvic xray (top left) demonstrates a right iliac wing fracture. Postoperative AP (top right), inlet (bottom left), and outlet (bottom right) pelvic views demonstrate screw fixation from the anterior inferior iliac spine to the posterior iliac spine without encroachment of the greater sciatic notch.

26 Complications Knowing the boundaries of percutaneous screw fixation of the pelvic fractures requires an understanding of the specific intraoperative fluoroscopic views used during screw placement. This knowledge will enable to radiologist to comment beyond the standard assessments of loss of reduction, perihardware lucency, screw fracture, and screw retraction by providing an additional assessment of potential hardware malposition. Some complications of percutaneous pelvic fracture fixation consist of violation of the hip joint, extension beyond cortical boundaries that may be missed during intra-operative fluoroscopy, and encroachment of the sacral neural foramina. These complications are illustrated in the following slides.

27 Illustrated Complications The illustrated images demonstrate violation of the hip joint by a retrograde superior pubic ramus screw.

28 Illustrated Complications The illustrated images demonstrate extension of a retrograde superior pubic ramus screw anterior to the acetabulum.

29 Illustrated Complications The illustrated image demonstrates encroachment of the bilateral neural foramina by an ilioscaral screw.

30 Summary High velocity pelvic trauma is commonly associated with pelvic ring disruptions. Percutaneous (minimal access) fixation methods are established techniques in pelvic fracture fixation. Radiologists should be aware of percutaneous techniques, to be able to identify adequate fixation and appropriate complications.

31 Thank you for your attention!

32 References (1) P. V. Giannoudis, et al. Percutaneous fixation of the pelvic ring. The journal of bone & joint surgery. 2007; 89-B: (2) Musculoskeletal Imaging. The Requisites. Mosby; 3rd edition (November 24, 2006) (3) M.L. Routt, et al. The Retrograde Medullary Superior Pubic Ramus Screw for the Treatment of Anterior Pelvic Ring Disruptions: A New Technique. Journal of Orthopedic Trauma. 1995;9: (4) J.A. Bishop, M.L. Routt. Osseous fixation pathways in pelvic and acetabular fracture surgery: Osteology, radiology, and clinical applications. Journal Trauma Acute Care Surgery. 2011;72: