^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).}

 

 

³¹⁰

 

 

 

^{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}

 

³¹¹

 

^{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.}

 

 

³¹²

 

 

 

 

^{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.)}

 

 

³¹³

 

^{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

 

^{Adequate fixation and accordingly proper pin placement are the principal requirements for restoring pelvic stability when applying an external fixator.}

 

^{Pins for purposes of anterior pelvic external fixation may be placed either in the anterior iliac crest or in the supraacetabular region (FIG 5).}

 

^{Ease of insertion is an important attribute when applying a resuscitation frame.}

 

 

 

^{FIG 5 • The anterior hemipelvis offers two sites for pin insertion: the iliac crest (superiorly) and the supraacetabular region (more inferiorly). A. Profile view. B. Frontal view.}

 

 

^{Pin placement within the iliac crest is more expeditiously performed and lacks significant regional anatomic hazards.}

 

 

^{On occasion, this area may be compromised by soft tissue concerns or proximity to fracture planes. In such cases, pin placement within the supra-acetabular region is an option.}

 

^{Pins and frames in this lower position may offer improved access to the abdomen and, unlike pins placed within the iliac crest, are less irritating to anterolateral abdominal soft tissues.19}

 

^{In an obese patient, these pins (supra-acetabular) may be better tolerated and less prone to loosening and infection.}

 

^{The dense bone of the supra-acetabular region offers stability of fixation as good as or better than the iliac crest.}

 

^{Some authors investigating the biomechanical performance of these pins (supra-acetabular) demonstrated superior purchase within bone and diminished displacement of posterior portions of the pelvic ring.12}

 

^{Because supra-acetabular pin insertion is more time consuming and instrumentation and fluoroscopy dependent, its role as a resuscitative measure is limited.}

 

^{The pelvic antishock clamp (C-clamp) is a posteriorly (or trochanteric) applied device that may offer greater}

^{stability to vertically unstable fractures than anteriorly applied frames (FIG 6).1, 11 It is designed for the emergent treatment of unstable pelvic ring injuries.}

 

 

^{The device is indicated in both rotationally and vertically unstable pelvic ring injuries.}

 

^{It is contraindicated in lateral compression injuries and fractures involving comminution of the iliac wing or sacrum. If the device is used in lateral compression-type injuries, it may accentuate the deformity. Use of the pelvic}

 

³¹⁴

^{antishock clamp with iliac wing fractures may lead to the pins traversing the fracture sites, subsequently causing internal injury.}

 

 

 

 

^{FIG 6 • “Antishock” clam This device, applied posteriorly, may offer more stability to vertically unstable injury patterns than anteriorly applied frames. A. Schematic. B. Case AP radiograph. (A: Modified from Simonian PT, Routt ML Jr, Harrington RM, et al. Anterior versus posterior provisional fixation in the unstable pelvis: a biomechanical comparison. Clin Orthop Relat Res 1995;310:245-251.)}

 

 

^{Despite advances in contemporary pelvic external fixation, concerns and complications associated with its application remain. Among these include poor patient tolerance, loss of reduction as well as pin tract sepsis, and loosening. In an effort to obviate these, the introduction of a subcutaneous internal anterior fixator has}

^{been described.29}

 

 

^{This technique employs either a precontoured rod or plate, which is introduced via small incisions at the}

^{level of the anterior inferior iliac spine (AIIS). A subcutaneous tunnel overlying the external oblique fascia is established through which the device is delivered and anchored within the dense bone of the supraacetabular region bilaterally.}

 

^{Close proximity to underlying intrapelvic and neurovascular structures demands an understanding of regional anatomy and proper surgical technique.16, 30 It is not applicable for resuscitative purposes, as its fluoroscopic and insertion times can be intensive. Attributes include enhanced patient mobilization and low}

^{documented rates of infection.}

 

 

^{Its most unique indication may be in obese individuals.31 Obligatory removal in an operating room setting remains a relative disadvantage.}

 

^TECHNIQUES

• ^{Circumferential Pelvic Antishock Sheeting}

   

  ^{Several techniques of noninvasive external pelvic ring stabilization have been described. Among them are the use of inflatable antishock trousers and spica casts. These do not permit abdominal access; they require skill and familiarity, and they conceal the abdomen.}

   

  ^{The simple application of a circumferential bed sheet may be considered during the resuscitation of the}

  ^{hemodynamically unstable patient.26 Unlike methods described earlier, this technique requires materials that are inexpensive, easy to apply, and readily available. No incisions that may jeopardize subsequent operative procedures are required. The sheet may be positioned to allow assessment of abdominal and lower extremity regions.}

   

   

   

  ^{TECH FIG 1 • Circumferential antishock sheeting. A. The sheet is positioned with inclusion of the trochanters of the hips. It is next pulled taut (B), overlapped (C), and secured with clamps (D).}

   

   

  ^{The patient's clothing should be removed before application. The sheet ends are crossed and overlapped anteriorly.}

   

  ^{The position of sheet application is directed more at the level of the greater trochanters of the hips than more proximally at the injured pelvis. Clamps secure the snugged sheets (TECH FIG 1).}

   

  ^{Long-term pelvic sheeting is discouraged as soft tissue compromise is a concern. It is contraindicated in the presence of unstable lateral compression injuries. Its use in such situations may aggravate deformity, resulting in internal visceral injury and posterior neurologic compression.}

   

  ^{Pelvic circumferential compression devices may offer the simplicity and effectiveness of sheeting with the}

  ^{benefit of feedback-controlled force. This may prevent inadequate or excessive compression.3, 13}

• ^{Anterior Iliac Crest: Open Technique}

 

^{A manual trial reduction is recommended before establishing a site for a skin incision.}

 

^{An 8- to 10-cm oblique wound adjacent and parallel to the iliac crest anteriorly is established.}

 

^{This incision is made in the anticipated site of the reduced hemipelvis to minimize tension on soft tissues (TECH FIG 2A).}

 

^{Dissection continues through skin and subjacent soft tissues, allowing palpation of the underlying iliac crest.}

 

 

^{Subperiosteal elevation of the external oblique exposes the inner table (TECH FIG 2B,C). Subperiosteal elevation of the hip abductors exposes the outer table (TECH FIG 2D).}

 

 

^{Exposure of the inner and outer tables continues within the confines of the surgical wound. The thick anterior pillar is identified (TECH FIG 2E).}

 

³¹⁵

 

^{The surgeon's index digit is introduced, confirming inner table inclination.}

 

^{The surgeon's thumb and index fingers palpate the outer and inner tables, respectively, to aid in establishing proper pin orientation within the two tables (TECH FIG 2F).}

 

^{The first pin is placed anteriorly within the anterior pillar, about 1 to 2 cm posterior to the anterior superior iliac spine.}

 

^{The iliac crest anteriorly is asymmetric with regard to crosssectional anatomy.}

 

^{The ideal starting point is thus along the medial third of the crest at the junction of the inner and middle thirds (“rule of thirds”) (TECH FIG 2G).}

 

^{Pins placed centrally or laterally are likely to be misdirected, exiting the desired intercortical path (TECH FIG 2H).}

 

 

 

^{TECH FIG 2 • Anterior iliac crest pin insertion, open technique. A. The skin incision is made at the anticipated site of the reduced iliac crest. B,C. The internal oblique is elevated from the inner table. D. The hip abductors are elevated from the outer pelvic table. E. The thick osseous pillar (asterisk) is the desired site of pin insertion. (continued)}

 

 

^{A unicortical drill hole, no more than 1 to 2 cm deep, initiates access within the crest.}

 

^{Pin direction is judged by manually grasping the crest within the surgeon's digits as described. This is typically 25 to 45 degrees medially and 10 to 15 degrees caudally.}

 

^{The pin may be introduced through the established surgical wound or adjacent (medial) percutaneous ones (TECH FIG 2I).}

 

^{The pin is advanced 5 cm (50-mm threaded, 5.0-mm diameter pin), directed within the pillar between the osseous tables of the ilium.}

 

^{The second pin and the third, if applicable, are inserted one fingerbreadth posterior to the previous pin.}

 

^{The narrow and curved profile of the crest does not allow parallel pin insertion and, on occasion, accommodates no more than two pins.}

 

³¹⁶

 

 

 

^{TECH FIG 2 • (continued) F. Palpation of the inner and outer tables confirms proper pin trajectory. G. The rule of thirds (cross-sectional junction of inner third and outer two-thirds of the crest) aids in establishing the preferential pin entry point. H. This facilitates pin insertion, preventing misdirection and premature exit.}

^{I. Alternatively, pins may be placed through percutaneous wounds subjacent to the open surgical incision.}

^{J. Pins should converge on the supra-acetabular region while remaining within the anterior pillar. K. Fluoroscopic guidance facilitates proper pin placement within the inner and outer tables. (A: Modified from Yang AP, Iannacone WM. External fixation for pelvic ring disruptions. Orthop Clin North Am 1997;28:331-344; J: Modified from Poka A, Libby E Indications and techniques for external fixation of the pelvis. Clin Orthop Relat Res 1996;329:54-59.)}

 

 

³¹⁷

 

^{Subsequent pins should appear to converge toward each other and the common target of the supraacetabular region within the anterior pillar (TECH FIG 2J).}

 

^{In an effort to retain intrapelvic tamponade, pins may be introduced through a similar approach without elevation of periosseous muscular attachments.}

 

^{Small Kirschner wires or spinal needles are directed along the iliac fossa to orient proper pin placement.}

 

^{Inner and outer table soft tissue attachments are preserved. Hematoma is not accessed and intrapelvic tamponade is preserved.}

 

^{A fluoroscopic obturator oblique outlet view of the pelvis can aid in identification of misdirected pins exiting the desired intercortical path (TECH FIG 2K).}

• ^{Anterior Iliac Crest: Percutaneous Technique}

   

  ^{Stab wounds 1 to 2 cm long are directed perpendicular from the anterior iliac crest toward the umbilicus (TECH FIG 3).}

   

  ^{This orientation diminishes undesirable soft tissue tension around the pin on pelvic reduction and greatly enables pin tract release in the event of impending pin tract infection.}

   

  ^{After completing the skin incision, dissection continues by spreading a surgical clamp, clearing away subcutaneous fat.}

   

  ^{Through these small wounds, Kirschner wires or spinal needles can be introduced along both sides of the iliac wing.}

   

   

   

  ^{TECH FIG 3 • Anterior iliac crest pin insertion, percutaneous technique. Stab wounds (1 to 2 cm long) are established perpendicular to the iliac crest in the direction of the umbilicus.}

   

   

  ^{This provides a targeting method to accurately position the pins within the two tables of the ilium.}

   

  ^{Guided by the spinal needles, a soft tissue trocar assembly is introduced and situated medial of the midline to account for lateral overhang (rule of thirds).}

   

  ^{Sagittal plane orientation of the pin must be considered as well.}

   

  ^{This requires that the drill be held more cephalad (directed caudad) than expected to allow proper position within the desired supra-acetabular bone (superior and cephalad to the acetabulum) rather than the thin bone of the ilium. Triple cannulated drill sleeves are used to protect soft tissues.}

   

  ^{The fixation pin is inserted, allowing the cortical walls of the ilium to establish direction. An image intensifier may aid in elective nonemergent fixator application.}

• ^{Supra-acetabular Technique}

   

  ^{The patient is positioned supine on a radiolucent table.}

   

  ^{Safe introduction and proper positioning of the pin require the assistance of fluoroscopic guidance.}

   

  ^{The open approach for pin placement begins with a vertically oriented 5- to 10-cm incision, depending on patient body habitus and prereduction pelvic deformity. A smaller transverse incision has been described in addition to entirely percutaneous techniques of pin insertion.}

   

  ^{This vertical approach begins along the lateral border of the anterior superior iliac spine, extending distally and lateral to the AIIS.}

   

   

  ^{The interval between the sartorius and tensor fascia lata is identified (TECH FIG 4A). Tissue planes are developed with blunt dissection and the anterior inferior spine is palpated.}

   

   

  ^{The lateral femoral cutaneous nerve is most commonly identified medial to the anterior iliac spine. Anatomic studies have demonstrated the lateral femoral cutaneous nerve to have a variable course, often within 10 mm of inserted pins.6}

   

  ^{With blunt dissection and the use of protective drill sleeves, the lateral femoral cutaneous nerve may be adequately protected.}

   

  ^{Supra-acetabular pins should be inserted no less than 2 cm proximal to the joint to avoid intra-articular penetration. Capsular extension of the hip may be up to 16 mm superiorly.}

   

  ^{An obturator oblique view with slight cephalad angulation}

  ^{(obturator outlet view) is first obtained. A metallic marker is positioned 2 cm proximal to the hip joint under fluoroscopic control (TECH FIG 4B).}

   

  ^{The trocar assembly is positioned under fluoroscopic control superior to the hip joint.}

   

  ^{Only the outer cortex is drilled. A triple cannulated guide facilitates atraumatic drill and pin insertion.}

   

  ^{The drill, followed by the pin, is directed within the pelvis, avoiding intra-articular penetration of the hip joint.}

   

  ³¹⁸

   

  ^{Pin angulation is typically 20 degrees medial from the vertical axis and slightly cephalad.}

   

  ^{The drill is directed toward and superior to the sciatic notch (30 to 45 degrees in the sagittal plane).}

  ^{Fluoroscopic guidance (iliac oblique view with slight cephalad angulation) ensures proper pin trajectory and depth of insertion (TECH FIG 4C,D).}

   

   

   

  ^{TECH FIG 4 • Supra-acetabular pin insertion technique. A. The interval between the sartorius and the tensor fascia lata is established (lateral femoral cutaneous nerve protected [asterisk]). B. An obturator outlet view identifies the proper pin entry site. C,D. An iliac oblique view with cephalad angulation directs the advancing pin. E,F. The rollover view (obturator oblique inlet view) ensures pin placement within the inner and outer tables of the pelvis.}

   

   

  ^{Intercortical pin orientation within the tables of the pelvis is monitored on an obturator oblique inlet view (“rollover view”) (TECH FIG 4E,F).}

   

   

  ^{A 5-mm diameter, 50-mm thread length pin is inserted to the depth of the threads. A second pin may be inserted proximal to the first, if desired.}

• ^{Frame Application and Reduction}

   

  ^{No frame, regardless of complexity, restores sufficient definitive fixation to vertically unstable lesions.22 Accordingly, simple constructs are preferred to permit patient mobilization, abdominal access, and performance of subsequent diagnostic and therapeutic procedures.}

   

  ^{Accurate pin placement within the curved iliac crest mandates a nonparallel converging pin pattern. Pin}

  ^{clamps with a straight configuration require that pins be prestressed to conform and accommodate such clamps (TECH FIG 5A). Those with an independent ball joint design offer an attractive alternative (TECH FIG 5B).}

   

  ³¹⁹

   

   

   

   

  ^{TECH FIG 5 • A,B. Pin clamps: straight and multiplanar.}

   

   

  ^{Applied pin clamps should remain three fingerbreadths above the skin surface. This is less threatening to subjacent soft tissues and permits adequate pin tract care.}

   

  ^{The frame is fabricated with inclusion of universal ball joints and reduction is performed. AP compression injuries are reduced with midline-directed compression and lateral compression injuries with distraction. Adjunctive lower extremity skeletal traction may be considered for vertically displaced patterns. Bar-to-bar connectors are next secured and operative incisions are closed and dressed.}

• ^{Pelvic Antishock Clamp: C-Clamp}

 

^{The surgeon can choose between two coronally oriented pin placement positions (anterior or posterior)}

^{(TECH FIG 6A).20 Anterior pins are placed in the dense column of bone of the gluteal ridge. Anterior pin placement will allow for compression of the anterior and, to some degree, the posterior pelvic ring.}

^{Posterior pin placement allows for compression of the posterior pelvic ring.}

 

 

 

^{TECH FIG 6 • Pelvic antishock clam A. Anterior and posterior sites of application. B. Pin site, (continued)}

 

 

^{Landmarks for anterior pin placement include the anterior superior iliac spine, the tip of the greater trochanter, and the axis of the femur.}

 

^{The surgeon should ensure that the patient's legs are not externally rotated, as this will place pins too far posterior.}

 

^{The surgeon finds the gluteal ridge, which is three fingerbreadths posterior to the anterior superior iliac spine on the iliac wing.}

 

³²⁰

 

 

 

^{TECH FIG 6 • (continued) C-E. Application landmarks and anterior pin site landmarks. F. Pelvic antishock clamp application landmarks and posterior pin site landmarks. (A: 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.)}

 

 

^{Next, the surgeon locates the tip of the greater trochanter and the axis of the femur with legs in neutral rotation.}

 

^{The center of the line connecting the gluteal ridge and the greater trochanter corresponds to the pin site. This point should be about 5 to 6 cm from the top of the iliac wing (TECH FIG 6B-E).}

 

^{Landmarks for posterior pin placement include the anterior superior iliac spine, posterior superior iliac spine, and dorsal axis of the femur. A line is drawn between the anterior and posterior superior iliac spines. The intersection of this line and the dorsal axis of the femur corresponds to the pin site. The pin site should be about 4 to 5 cm anterior to the posterior iliac spine (TECH FIG 6F). The surgeon must avoid the greater sciatic notch and the soft bone of the iliac fossa.}

 

^{The pin site is infiltrated with local anesthetic and an incision is made. Blunt dissection is carried down to bone.}

 

^{The pins are adjusted to be in a single axis. This orientation allows rotation of the C-clamp, permitting abdominal access.}

^{Reduction of any vertical displacement is now completed with traction.}

 

^{Alternatively, the C-clamp may be directly applied to the trochanteric region of the femur.1 The anatomic hazards of the previous method of application are thus avoided. In this manner, it serves a role similar to circumferential sheeting.}

 

³²¹

• ^{Subcutaneous Anterior Internal Pelvic Fixation}

 

^{Internalization of anterior pelvic fixation may be preferable when external fixation is planned as the definitive treatment modality.}

 

^{This is especially true in obese patients where a traditional external fixator may be necessarily placed farther from bony anatomy, affording less stability and predisposing pin tracts to infection.}

 

^{Internalized, subcutaneous fixators show lower rates of infection and loosening, but heterotopic ossification is a concern and lateral femoral cutaneous nerve irritation is somewhat common.30}

 

^{The technique depicted in this text employs cannulated instruments and implants commonly employed for posterior spinal fixation. Several similar procedures have evolved using similar techniques with plates, screws, pins, or alternative devices.}

 

^{The patient is positioned supine on radiolucent table, and ability to obtain the necessary C-arm positioning for the appropriate fluoroscopic views is confirmed prior to draping.}

 

^{The skin is prepared and draped from umbilicus to the upper thigh.}

 

^{If needed for reduction, the lower extremities may be included; for example, if performing iliosacral screw placement concurrently, many surgeons prefer to perform posterior stabilization prior to anterior.}

 

^{The anterior superior iliac spine is used as a superficial landmark; the incision and starting point is approximately 2 cm caudal and 1 cm medial to this point. Placement of the incision over the AIIS is confirmed with fluoroscopy.}

 

^{Incision is made obliquely in line with skin folds over the AIIS, and dissection is carried down between sartorius and tensor fascia lata down to AIIS.}

 

^{A Jamshidi needle is pressed between the cortices of the ilium, directed toward the posterior superior iliac spine, as visualized on the obturator oblique outlet fluoroscopic view (as noted in the Supraacetabular}

^{Technique section of this chapter) (TECH FIG 7 A,B).}

 

^{The obturator inlet view is used for surveillance of the needle as well as the subsequent guidewire and screw advancement between the tables of the ilium, as noted previously.}

 

^{The guidewire of the pedicle screw system is then positioned and advanced through the needle, between the tables of the ilium toward the posterior superior iliac spine under fluoroscopic control, and length is measured.}

 

 

 

^{TECH FIG 7 • A. Jamshidi needle with guidewire in place in supraacetabular bone. B. Fluoroscopy obturator outlet view showing placement of guidewire via Jamshidi needle. (continued)}

 

 

^{It is essential when selecting screw length to consider that the screw should stand proud about 1.5 to 4 cm from bone to allow the connecting rod to lie subcutaneously without compression of traversing neurovascular structures (iliac vessels, femoral nerve). Patient habitus should be considered when contemplating this additional length, as the fixator can be customized to match patient body habitus, with}

^{longer lengths for obese patients and shorter lengths for thin patients to avoid hardware prominence.29}

 

^{A tap can be employed if desired, especially if a plain screw is being used as in part of a noncannulated system (TECH FIG 7 C-E).}

 

^{A single 7.0- to 8.5-mm cannulated uniaxial or polyaxial pedicle screw is placed over the guidewire using the screw assembly (TECH FIG 7 F,G).}

 

^{The procedure is repeated on the contralateral side either simultaneously or sequentially after placement of the first screw (TECH FIG 7H).}

 

^{The 5.5- to 6.5-mm titanium connecting rod is precontoured with an anterior bow to comply with individual patient habitus and pelvic morphology. This rod is inserted above the abdominal fascia via a subcutaneous tunnel using the rod holder assembly to meet the contralateral screw (TECH FIG 7 I,J).}

 

^{The “bikini line” has been described to guide rod placement subcutaneously and exists as a skin fold essentially connecting the two AIIS. This line exists, on average, 5-7 cm above the pubic symphysis.31}

 

^{The individual contouring of the rod is a variable that must be considered when taking care to avoid compression of vital structures, as external iliac vessels are, on average, a mere 2.2 cm posterior to the rod when done correctly.16}

 

^{Once the rod is captured and locked by an end cap on one side, rotational reduction can be finalized, closing the pelvis anteriorly. Use of a system-specific compression tool is feasible at this point prior to applying the second end cap, locking the fixator. Supra-acetabular compression has been observed to}

^{infer some modest degree of posterior reduction as well.8}

 

^{A rod cutter is employed to eliminate excessive lateral overhang of the rod if desired. Incisions are irrigated}

^{and closed according to surgeon preference, with the screw heads left above fascia (TECH FIG 7K).}

 

^{The surgeon should bear in mind that internalization of the fixator in the manner described mandates a return to the operating room for removal after healing of fractures (typically between 3 to 6 months).}

 

³²²

 

 

 

^{TECH FIG 7 • (continued) C. Cannulated tap placed over guidewire through soft tissue dilator. D. Fluoroscopic view of tap over guidewire between the inner and outer tables of the ilium. E. Iliac oblique of the tap in place at AIIS. F. Placing the cannulated pedicle screw over the guidewire. G. Screw in place over the guidewire; notice the screw is left proud to accommodate the connecting rod over the fascia. H. Both pedicle screws have been placed, the inserters are left in place in preparation for the connecting rod. (continued)}

 

 

³²³

 

 

 

^{TECH FIG 7 • (continued) I. The connecting rod is placed percutaneously. J. Fluoroscopic view confirming rod capture by the pedicle screw. K. View of the screw head above the fascia.}

 

PEARLS AND PITFALLS
	Enhancing pin ▪ The pin-bone interface has maximal stress concentration and represents the fixation weakest component of the external frame assembly. Bone quality, frame rigidity, pin number, and pin placement and diameter can all affect the strength of the pin-bone interface. The insertion length, also referred to as the intercortical distance, greatly influences pullout forces. As a general rule, pins should be maintained within the two cortices as long as possible. Distal cortical penetration is technically undesirable and should be avoided.

 

• ^{Pins of adequate intercortical distance consistently appear to outperform those with transcortical purchase (undesired extracortical exit).}

 

^{Avoiding conflicting surgical exposures}

• ^{Surgical wounds and pin location in the supra-acetabular region are less likely to compromise future anticipated surgical wounds. This is particularly important if anterior access to the sacroiliac joint is anticipated and pursued later.}

 

^{Anterior iliac crest wound}

• ^{The surgical wound anteriorly should be placed in the anticipated region of the hemipelvis after reduction. This minimizes tension on soft tissues. Percutaneous wounds may be made adjacent to the open exposure to allow pin introduction.}

  ^{The wound is closed before frame application.}

   

  ^{Anticipating pin trajectory in the unreduced pelvis}

• ^{Pin inclination in the unreduced pelvis does not reflect normal parameters.}

• ^{Depending on deformity, pin inclination may be more vertical (lateral compression) or horizontal (externally rotated, AP compression).}

   

  ^{Avoiding extrapelvic misguided pins}

  • ^{“Preferential errors” do exist!}

  • ^{For AP compression injuries, an internal exit is preferred. For lateral compression injuries, an external exit is preferred. This maintains three-point fixation in a mechanically advantageous manner.}

     

    ^{Overcompression is possible.}

• ^{Depending on the method of application, reduction, and fracture pattern, compression with an anteriorly applied frame may accentuate posterior displacement.}

   

  ^{Beware of neurovascular damage by anterior subcutaneous rod.}

  • ^{Compression of traversing femoral vessels and femoral nerve is to be avoided with adequate rod contouring. Careful postoperative neurologic examination is mandatory and consideration should be given to Doppler ultrasound of femoral vessels.}

^{Lateral femoral cutaneous nerve irritation rates approach 30%.}

 

^{POSTOPERATIVE CARE}

 

^{After satisfactory application of the frame, individual pin sites are scrutinized and soft tissues are released to prevent tension-induced necrosis and subsequent infection.}

 

^{Postapplication imaging confirms pelvic stability, symmetry, and indications for additional anterior or posterior (open or percutaneous) stabilization techniques.}

 

^{Pin sites are débrided of organized blood and cleansed once or twice daily with peroxide solution. Dressings may be applied (if inspected regularly) or the wounds may be left open. Peripheral pin site tension should be released with sharp dissection under local anesthesia. Regional necrosis and subsequent pin tract sepsis are thereby avoided.}

 

^{Mobilization and weight bearing are dictated by the injury pattern and designated stability classification.}

 

^{After application of a subcutaneous anterior internal fixator, it may be advisable to obtain a duplex ultrasound of the femoral and iliac vessels with the hip in flexion to exclude the possibility of compression of these vessels.}

^{Careful examination of femoral nerve function is also advisable. Compression of these vital structures may necessitate revision.25}

 

^OUTCOMES

^{Severe hemodynamic instability on arrival is a useful predictor of mortality and transfusion demands. Death within the first 24 hours is often due to acute blood loss; after this time, it is usually secondary to multisystem organ failure.}

^{Reported mortality rates of open pelvic fractures range from 10% to 45%. These injuries are often associated with injuries of prognostic significance. Life-saving strategies to address this problem continue to evolve. The degree of pelvic instability clearly parallels rates of morbidity and mortality.}

^{Vertically unstable fractures, despite adequate contemporary management, have significant neurologic and associated injuries that remain of long-term consequence and disability.}

^{Those with rotational instability alone have a considerably more favorable prognosis.18, 28}

^{The transient use of external fixation is efficacious if its role and indication are clearly defined. Use for definitive treatment is associated with a high rate of infection and aseptic pin loosening. Unstable posterior lesions are inadequately managed with external fixation alone.}

 

 

^{COMPLICATIONS}

^{Sheeting: overcompression (lateral compression injuries), skin breakdown if sheeting is maintained for prolonged periods of time.}

^{General: pin tract sepsis, loss of pin fixation, malreduction, loss of reduction14 Anterior external pelvic fixation: inadequate or aggravated posterior alignment}

^{Supra-acetabular pin placement: lateral femoral cutaneous nerve injury, intra-articular hip penetration, sciatic notch neurovascular injury}

^{Subcutaneous anterior fixator: above supra-acetabular complications and, additionally, compression of neurovascular structures by connecting rod is a possibility if rod is undercontoured or screws are placed}

^{too deeply. Asymptomatic heterotopic ossification is also reported.30 C-clamp: intrapelvic pin penetration}

 

 

^REFERENCES

1. ^{Archdeacon MT, Hiratzka J. The trochanteric C-clamp for provisional pelvic stability. J Orthop Trauma 2006;20:47-51.}

    

    

2. ^{Blackmore CC, Cummings P, Jurkovich GJ, et al. Predicting major hemorrhage in patients with pelvic fracture. J Trauma 2006;61:346-352.}

    

    

3. ^{Bottlang M, Krieg JC, Mohr M, et al. Emergent management of pelvic ring fractures with use of}

   ^{circumferential compression. J Bone Joint Surg Am 2002;84A:43-47.}

    

    

4. ^{Cook RE, Keating JF, Gillespie I. The role of angiography in the management of haemorrhage from major fractures of the pelvis. J Bone Joint Surg Br 2002;84:178-182.}

    

    

5. ^{Dente CJ, Feliciano DV, Rozycki GS, et al. The outcome of open pelvic fractures in the modern era. Am J Surg 2005;190:830-835.}

    

    

6. ^{Deridder VA, de Lange S, Popta JV. Anatomical variations of the lateral femoral cutaneous nerve and the consequences for surgery. J Orthop Trauma 1999;13:207-211.}

    

    

7. ^{Eastridge BJ, Starr A, Minei JP, et al. The importance of fracture pattern in guiding therapeutic decision-making in patients with hemorrhagic shock and pelvic ring disruptions. J Trauma 2002;53:446-450.}

    

    

8. ^{Gardner MJ, Nork SE. Stabilization of unstable pelvic fractures with supraacetabular compression external fixation. J Orthop Trauma 2007; 21:269-273.}

    

    

9. ^{Giannoudis PV, Pape HC. Damage control orthopaedics in unstable pelvic ring injuries. Injury 2004;35:671-677.}

    

    

10. ^{Hak DJ. The role of pelvic angiography in evaluation and management of pelvic trauma. Orthop Clin North Am 2004;35:439-443.}

     

     

    ³²⁴

     

11. ^{Heini PF, Witt J, Ganz R. The pelvic C-clamp for the emergency treatment of unstable pelvic ring injuries: a report on clinical experience of 30 cases. Injury 1996;27:A38-A45.}

     

     

12. ^{Kim WY, Hearn TC, Seleem O, et al. Effect of pin location on stability of pelvic external fixation. Clin Orthop Relat Res 1999;361:237-244.}

     

     

13. ^{Krieg JC, Mohr M, Ellis TJ, et al. Emergent stabilization of pelvic ring injuries by controlled circumferential compression: a clinical trial. J Trauma 2005;59:659-664.}

     

     

14. ^{Mason WT, Khan SN, James CL, et al. Complications of temporary and definitive external fixation of pelvic ring injuries. Injury 2005; 36:599-604.}

     

     

15. ^{Mendez C, Gubler KD, Maier RV. Diagnostic accuracy of peritoneal lavage in patients with pelvic fractures. Arch Surg 1994;129: 477-481.}

     

     

16. ^{Merriman D, Ricci W, McAndrew C, et al. Is application of an internal anterior pelvic fixator anatomically feasible? Clin Orthop Relat Res 2012;470:2111-2115.}

     

     

17. ^{Miller PR, Moore PS, Mansell E, et al. External fixation or arteriogram in bleeding pelvic fracture: initial therapy guided by markers of arterial hemorrhage. J Trauma 2003;54:437-443.}

     

     

18. ^{Miranda MA, Riemer BL, Butterfield SL, et al. Pelvic ring injuries: a long-term functional outcome study. Clin Orthop Relat Res 1996;329:152-159.}

     

     

19. ^{Noordeen MH, Taylor BA, Briggs TW, et al. Pin placement in pelvic external fixation. Injury 1993;24:581-584.}

     

     

20. ^{Pohlemann T, Braune C, Gansslen A, et al. Pelvic emergency clamps: anatomic landmarks for a safe primary application. J Orthop Trauma 2004;18:102-105.}

     

     

21. ^{Poka A, Libby E Indications and techniques for external fixation of the pelvis. Clin Orthop Relat Res 1996;329:54-59.}

     

     

22. ^{Ponsen KJ, Hoek van Dijke GA, Joosse P, et al. External fixators for pelvic fractures: comparison of the stiffness of current systems. Acta Orthop Scand 2003;74:165-171.}

     

     

23. ^{Reilly MC, Zinar DM, Matta JM. Neurologic injuries in pelvic ring fractures. Clin Orthop Relat Res 1996;329:28-36.}

     

     

24. ^{Routt ML Jr, Falicov A, Woodhouse E, et al. Circumferential pelvic antishock sheeting: a temporary resuscitation aid. J Orthop Trauma 2002;16:45-48.}

     

     

25. ^{Sellei R, Dienstknecht T, Bruken D, et al. Percutaneous anterior internal pelvic fixator. Oper Tech Orthop 2013;23:33-37.}

     

     

26. ^{Simpson T, Krieg JC, Heuer F, et al. Stabilization of pelvic ring disruptions with a circumferential sheet. J Trauma 2002;52:158-161.}

     

     

27. ^{Starr AJ, Griffin DR, Reinert CM, et al. Pelvic ring disruptions: prediction of associated injuries, transfusion requirement, pelvic arteriography, complications, and mortality. J Orthop Trauma 2002;16: 553-561.}

     

     

28. ^{Tornetta P III, Templeman DC. Expected outcomes after pelvic ring injury. AAOS Instr Course Lect 2005;54:401-407.}

     

     

29. ^{Vaidya R, Colen R, Vigdorchik J, et al. Treatment of unstable pelvic ring injuries with and internal anterior fixator and posterior fixation: initial clinical series. J Orthop Trauma 2012;26(1):1-8.}

     

     

30. ^{Vaidya R, Kubiak E, Bergin P, et al. Complications of anterior subcutaneous internal fixation for unstable pelvis fractures: a multicenter study. Clin Orthop Relat Res 2012;470:2124-2131.}

     

     

31. ^{Vaidya R, Oliphant B, Jain R, et al. The bikini area and bikini line as location for anterior subcutaneous pelvic fixation: an anatomic and clinical investigation. Clin Anat 2013;26:392-399.}