External Fixation of the Pelvis



External Fixation of the Pelvis


Stephen A. Kottmeier

Brian Campfield

John C. P. Floyd

Nicholas Divaris





DEFINITION



  • Pelvic instability is defined as inability of the pelvis to assume physiologic loads without displacement and functional compromise.


  • Pelvic external fixation can serve several different purposes depending on hemodynamic and pelvic structural instability.


  • Early external fixator application during resuscitative acute phase management can serve to control intrapelvic hemorrhage.9


  • External fixation of the pelvis may confer sufficient provisional stability to some injury patterns to facilitate patient mobilization. It may, however, prove inadequate in achieving long-term goals in the absence of additional surgical stabilizing efforts.


  • With certain rotationally unstable yet vertically stable patterns, external fixation of the pelvis or an internalized anterior fixator may serve as definitive management.


ANATOMY



  • The pelvis provides structural continuity between the axial skeleton and lower extremities.


  • The pelvis affords protection and passage for genitourinary, gastrointestinal, and neurovascular structures.


  • Life-threatening massive hemorrhage, a complication of pelvic injury, can be of arterial (branches of the iliac system), venous plexus, or fracture surface origins.


  • Additional concerns when treating pelvic ring trauma include injury to the lumbosacral and coccygeal nerves and male urethra.


  • The anterior portion of the pelvic ring assumes minimal weightbearing function and affords little pelvic ring stability.


  • The pelvic ring is made up of the sacrum and paired innominate bones. Ligamentous, rather than osseous, support is the sole source of stability to the pelvis.


  • Stability of the pelvis is particularly dependent on the tension band of the posterior weight-bearing sacroiliac complex (comprising the anterior sacroiliac ligaments, the interosseous ligaments, and the posterior sacroiliac ligaments) in addition to the iliosacral ligaments within the pelvic floor (sacrospinous and sacrotuberous). The iliolumbar ligaments confer additional stability between the axial skeleton (L5 transverse process) and the hemipelvis (ilium).


PATHOGENESIS



  • Pelvic injury patterns (osseous or ligamentous) are determined by the direction, point of application, and magnitude of applied forces.


  • Applied forces can be simplified into anteroposterior (AP) compression, lateral compression, and vertical shear. Actual forces and accordingly mechanism of injury are likely more complex.


  • Resultant instability patterns are categorized as (1) vertically and rotationally stable, (2) rotationally unstable and vertically stable, and (3) rotationally and vertically unstable.


  • AP compression and hemipelvic rotational forces tend to result in injury to the “anterior ligamentous” complex (severity order: symphysis pubis, ischiosacral ligaments, anterior sacroiliac ligament). The integrity of the posterior tension band is preserved and vertical stability accordingly maintained (FIG 1A). Depending on the severity of injury to the anterior ligamentous complex, rotational instability may ensue.


  • Lateral compression injuries, depending on severity, may result in internal collapse of the pelvis. Ligaments both anteriorly and posteriorly generally remain intact. Osseous injuries both anteriorly and posteriorly are typically stable impaction variants. Occasionally, internal rotatory instability is sufficient to warrant surgical stabilization (external or internal fixation).


  • Vertical instability implies disruption of the posterior tension band of the pelvic ring. This may be of osseous, ligamentous, or combined origin. Division of the sacrospinous and sacrotuberous ligaments in the presence of intact posterior ligaments will render a pelvis rotationally unstable. Further division of the posterior ligaments of the sacroiliac complex will result in both rotational and vertical instability. The involved hemipelvis is unstable in the axial, sagittal, and coronal planes (FIG 1B).


  • Any injury mechanism (AP compression, lateral compression, vertical shear) may result in complete (vertical and rotational) instability if the magnitude of force is sufficient.


NATURAL HISTORY



  • Life-threatening hemorrhage associated with pelvic fractures may be intrapelvic or extrapelvic. Identifying the source of bleeding may be challenging.27 In the absence of extrapelvic and intraperitoneal sources, external fixation of the pelvis may prevent life-threatening exsanguination.



    • Early sheeting (circumferential external compression) may offer an initial beneficial hemodynamic response. Suspected sustained hemorrhage of indeterminate source may be intrapelvic arterial in origin.2 This may respond favorably to angiographic transcatheter embolization.


    • Exploratory laparotomy, from the standpoints of role and timing, remains controversial.


    • Imaging findings, results of diagnostic peritoneal lavage (if indicated), and response to fluid resuscitation must be considered before exposing the unstable trauma victim to the potential negative effects of abdominal exploration (decompression of intrapelvic tamponade, among others).







      FIG 1 • A. An external rotation injury (AP compression) resulting in “anterior ligamentous complex injury.” Instability is rotational in character and demonstrated in the axial plane. The posterior tension band is intact and vertical stability is preserved. B. A vertical shear injury. In addition to compromise to the “anterior ligamentous complex,” the integrity of the posterior tension band is disrupted. The involved hemipelvis is unstable in all planes. (Modified from Buckle R, Browner B, Morandi M. Emergency reduction for pelvic ring disruptions and control of associated hemorrhage using the pelvic stabilizer. Tech Orthop 1995;9:258-266.)


  • Pelvic fractures associated with violation of the perineal, rectal, or vaginal regions must be identified immediately, and early measures directed toward preventing regional and systemic sepsis must be implemented. Appropriate soft tissue management requires early aggressive débridement and restoration of pelvic stability to facilitate wound care. External fixation is of paramount importance in many such cases, as is diverting colostomy.


  • Lumbosacral plexopathy may present in combination with sacral spinal canal or foraminal fractures. Pelvic reduction with restoration of stability and occasionally neurologic decompression may afford a more favorable prognosis if properly indicated and executed.23


  • Insufficient restoration of pelvic stability may result in complications associated with prolonged recumbency. Additional concerns include malunion and nonunion. Lower extremity limb length inequality and rotational deformity may result in functional deficits. Anterior ring injuries with significant displacement (tilt fragments) can result in sexual dysfunction, particularly in females.


PATIENT HISTORY AND PHYSICAL FINDINGS



  • The history, in terms of the mechanism of injury, offers insight into the energy of injury imparted. Force application and magnitude in turn determine pelvic injury and instability patterns as well as the type and frequency of associated injuries.7


  • The patient’s age may affect both physiologic reserve and bone quality. This dictates, respectively, the hemodynamic response and the energy of injury required to generate certain pelvic ring injuries.


  • Preexisting medical comorbidities must be ascertained, as they may have considerable impact on survivability and complications associated with both operative and nonoperative management of pelvic injuries.


  • Pelvic ring disruption is often accompanied by potentially life-threatening injuries to organs, vessels, and nerves within the pelvis, as well as other extrapelvic and closed cavity lesions of the abdomen, thorax, and head.


  • Adequate adherence and response to principles of resuscitation must be assessed and primary and secondary surveys completed.


  • Clinical evaluation includes inspection for abrasions, contusions, limb length discrepancy, or abnormal rotation of the lower extremities.


  • Palpation and manual testing for instability patterns may be pursued with caution. Stability is suggested (not confirmed) both radiographically and clinically.


  • Identification of any open fracture variants and those with rectal or vaginal continuity is mandatory, as mortality rates in the presence of such lesions are considerable.5


  • Physical examination should include the following:



    • Pelvic inspection to identify threatened or compromised soft tissues


    • Inspection of lower extremities for limb length inequality, rotational deformity, associated limb fractures or dislocations



      • Significant asymmetry in limb length or rotation implies rotational or vertical pelvic instability.


      • Further clinical examination or imaging of the limb is warranted if asymmetry is of other than pelvic origin.


    • Assessment of pelvic instability



      • Lateral compression injury is implied by internal rotation and shortening.


      • Vertical shear injury is implied by external rotation and shortening.


    • The genitourinary area is observed for regional hemorrhage. If present, it implies a urethral tear in a male and a vaginal tear in a female.


    • Neurologic assessment to identify deficits in voluntary sphincter control or perianal sensation. Lumbosacral plexopathy implies pelvic instability.


IMAGING AND OTHER DIAGNOSTIC STUDIES



  • Imaging studies offer a static view of the pelvis. These accordingly may imply but do not confirm stability (or instability) of the pelvis.



  • Conventional radiography is initiated with performance of an AP radiograph of the pelvis. In the hemodynamically unstable patient, this image alone is sufficient to allow implementation of treatment.


  • The pelvic inlet and outlet views in combination with the

    AP radiograph constitute the pelvic trauma radiographic triad (FIG 2A). The inlet view (FIG 2B) best depicts axial

    (most often posterior) and rotational displacement. In contrast, the outlet view (FIG 2C) best demonstrates vertical displacement.


  • Posterior pelvic displacement of more than 1 cm suggests posterior pelvic disruption. Symphyseal diastasis of more than 2.5 cm denotes disruption of the anterior ligament complex.


  • Other radiographic clues implying vertical or rotational instability include the following:



    • Sacrospinous ligament avulsions (ischial spine or sacral border fractures)


    • Iliolumbar ligament avulsion (L5 transverse process fracture)


    • Sacral fractures or sacroiliac joint displacement


  • Stress radiographs (“push-pull” studies) may offer a dynamic interpretation of pelvic instability (FIG 3). Longitudinal load and traction are sequentially imparted to the lower extremity of the involved hemipelvis with manual stabilization of the contralateral extremity.



    • This is performed with the patient anesthetized and under

      AP radiographic control.






      FIG 2 • A. AP view. The x-ray beam is directed perpendicular to the midpelvis. This view alone (particularly in the presence of hemodynamic instability) may be used to confirm the presence of pelvic instability and offer indication for pelvic external fixation. B. Inlet view. The x-ray beam is directed caudally at 45 degrees to the vertical axis centered on the midpelvis. AP displacement and axial rotational deformities are demonstrated. C. Outlet view. The x-ray beam is directed cephalad at 45 degrees to the vertical axis centered on the midpelvis (perpendicular to the sacrum). Vertical and sagittal plane deformities are demonstrated.


    • Such maneuvers are contraindicated in the presence of lumbosacral plexopathy, hemodynamic instability, or ipsilateral lower extremity fractures.


  • Computed tomography (CT) serves as a valuable adjunctive study. Cross-sectional axial images characterize posterior lesions best. Sacral foraminal and central spinal canal involvement is confirmed, as is integrity of the posterior tension band. Sacral impaction as opposed to gap displacement may suggest (but does not confirm) inherent stability.


  • The role of diagnostic and therapeutic angiography remains controversial with regard to management pathways.4, 10, 17 External fixation of the pelvis may effectively arrest venous and osseous hemorrhage (the source of 90% of intrapelvic hemorrhage).

    Sustained hemodynamic instability may suggest extrapelvic or intrapelvic arterial blood loss. In such cases, exploratory angiography may be considered and therapeutic arterial angiographic embolization performed as necessary.


  • Diagnostic peritoneal tap and lavage (first described in 1965) has a poorly defined contemporary role.15 Procedure performance, indications, and assay result criteria (cell count) remain ambiguous. The presence of a pelvic fracture may contribute to a false-positive result.



    • Current imaging technology (contrast-enhanced CT, focused abdominal ultrasound) may prove a more reliable tool to determine the likelihood of abdominal injury and the need for laparotomy.







FIG 3 • A,B. Push-pull radiographs (performed under controlled circumstances and in the absence of hemodynamic instability) may aid in identification of vertically unstable fracture variants. (Modified from Iannacone WM, Brathwaite CEM. Use of the external fixation frame for acute stabilization of unstable pelvic fractures. Oper Tech Orthop 1993;3:2-12.)




DIFFERENTIAL DIAGNOSIS



  • Low-energy pelvic fractures in senescent bone


  • High-energy pelvic fractures in younger patients with better quality bone


  • Similar fracture patterns in the two groups cited earlier suggest a high magnitude of force in the younger population. This, in turn, is more commonly associated with additional injuries of concerning severity.


  • “Nonring” fractures: iliac crest, ischial tuberosity


  • Ring fractures of increasing severity and instability



    • Rotationally and vertically stable


    • Rotationally unstable and vertically stable


    • Rotationally and vertically unstable


NONOPERATIVE MANAGEMENT



  • Circumferential pelvic antishock sheeting may offer comfort and enhance ring stability.24 This noninvasive method employs readily available and inexpensive materials.


  • Nonsurgical management is appropriate for lesions accurately deemed stable (confirmed on follow-up both clinically and radiographically).


  • The goals for nonsurgical and surgical management are identical. These include avoidance or correction of deformity, maintenance of stability, and pain-free function.


SURGICAL MANAGEMENT



  • The role of the external fixator must be defined before application.21 By decreasing pelvic volume, it offers intrapelvic tamponade. This, in addition to diminishing fracture motion, encourages hemostasis. In this capacity, it serves as acute phase management.


  • It may offer provisional stabilization of some injury patterns to facilitate patient mobilization. Attempts to stabilize vertically unstable lesions with external fixation alone are inadequate (FIG 4); these injuries require staged supplemental posterior fixation. Used for this purpose, it serves as provisional stabilization.


  • Rotationally unstable yet vertically stable patterns may be amenable to external fixation as a source of definitive stabilization. Lesions with considerable symphyseal comminution unreceptive to anterior plating may be managed to union with external fixation, provided the posterior tension band remains functionally intact.


Preoperative Planning



  • The surgeon must identify associated intrapelvic, vascular, urologic, and gynecologic comorbidities.


  • The surgeon must confirm the patient’s neurologic status and document deficits. Soft tissues are inspected thoroughly and circumferentially.






    FIG 4 • Anterior external fixation of the pelvis does not confer posterior stability. In this example, left posterior sacroiliac diastasis is unresolved. In such cases, anterior external fixation may effectively manage hemodynamic instability but does not offer structural posterior stability. (From Peters P, Bucholz RW. The assessment of pelvic stability following pelvic ring disruptions. Tech Orthop 1990;4:52-59.)



  • The surgeon characterizes, if applicable, the presence and type of pelvic instability, assigning the injury pattern to a classification scheme.


  • The intended purpose of external fixator must be defined

    (resuscitation or provisional vs. definitive stabilization).


  • If for purposes of provisional stabilization, the surgeon should determine the anticipated timing, sequence, and method of subsequent definitive stabilization.


  • Frame design and pin location are selected (anterior iliac crest, supra-acetabular, posterior C-clamp) based on the pelvic injury pattern, the patient’s hemodynamic status, the available imaging, and surgeon familiarity.


  • An immediate presurgical pelvic radiograph is obtained to assess the impact of retained bowel gas or contrast on imaging capability (if required).


Positioning



  • The patient is placed supine on a radiolucent table.


  • Adequacy of imaging and efficacy of closed reduction maneuvers are confirmed.


  • Preparation is done from the umbilicus to the anterior thighs, including both iliac crests.


  • One or both lower extremities are included circumferentially as required to effect rehearsed closed reduction maneuvers.


Approach

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Jul 22, 2016 | Posted by in ORTHOPEDIC | Comments Off on External Fixation of the Pelvis

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