Stephen Kottmeier, John C. P. Floyd, and 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.8
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 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 weight-bearing 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 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.
Anteroposterior 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 (anteroposterior 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.25 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.2This 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).
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.
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.)
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.22
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:
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 anteroposterior (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.
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 caudad 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.
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.
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.4,9,16
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.
DIFFERENTIAL DIAGNOSIS
Low-energy pelvic fractures in senescent bone
High-energy pelvic fractures in younger patients with betterquality bone
FIG 3 • “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.)
Similar fracture patterns in the two groups above suggest a high magnitude of force in the younger population. This in turn is more commonly associated with additional injuries of concerning severity.
“Non-ring” 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.23 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.20 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.
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 versus definitive stabilization).
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.)
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).
FIG 5 • The anterior hemipelvis offers two sites for pin insertion: the iliac crest (superiorly) and the supra-acetabular region (more inferiorly). A. Profile view. B. Frontal view.
Ease of insertion is an important attribute when applying a resuscitation frame.
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.18
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.11
Because supra-acetabular pin insertion is more timeconsuming 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).1,10 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 antishock clamp with iliac wing fractures may lead to the pins traversing the fracture sites, subsequently causing internal injury.
FIG 6 • “Antishock” clamp. 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 MLCJ, Harrington RM, et al. Anterior versus posterior provisional fixation in the unstable pelvis: a biomechanical comparison. Clin Orthop Relat Res 1995;310:245–251.)
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.24 Unlike methods described above, 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.
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
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).
ANTERIOR ILIAC CREST: OPEN TECHNIQUE
A manual trial reduction is recommended before establishing a site for a skin incision.
An 8to 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).
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 cross-sectional 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).
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 caudad.
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-mmdiameter pin), directed within the pillar between the osseous tables of the ileum.
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.
Subsequent pins should appear to converge toward each other and the common target of the supra-acetabular 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).
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 (*) is the desired site of pin insertion. 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 EP. Indications and techniques for external fixation of the pelvis. Clin Orthop Relat Res 1996;329:54–59.)
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.
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.
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.
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 5to 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 anterior inferior iliac spine.
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.
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).
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.
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 (*). 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.
FRAME APPLICATION AND REDUCTION
No frame, regardless of complexity, restores sufficient definitive fixation to vertically unstable lesions.21 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).
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. Anteroposterior 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.
TECH FIG 5 • Pin clamps: straight (A) and multiplanar (B).
PELVIC ANTISHOCK CLAMP: C-CLAMP
The surgeon can choose between two coronally oriented pin placement positions (anterior or posterior) (TECH FIG 6A).19 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.
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.
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).
TECH FIG 6 • Pelvic antishock clamp. A. Anterior and posterior sites of application. B. Pin site. C–E. Application landmarks and anterior 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.) F. Pelvic antishock clamp application landmarks and posterior pin site landmarks.
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.
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.
Post-application 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.
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.17,26
COMPLICATIONS
Sheeting: overcompression (lateral compression injuries)
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
C-clamp: intrapelvic pin penetration
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