eMedicine Specialties > Orthopedic Surgery > Hip

Unstable Pelvic Fractures

Author: Kenneth W Graf Jr, MD, Consulting Surgeon, Department of Orthopedic Trauma Services, Mission Hospitals
Coauthor(s): Madhav Karunakar, MD, Consulting Surgeon, Section of Orthopedic Surgery, Department of Surgery, University of Michigan Medical Center
Contributor Information and Disclosures

Updated: Jan 18, 2008

Introduction

Most pelvic fractures are stable and occur with a low-energy mechanism of injury. The evaluation and treatment of these fractures are described in Pelvic Fractures. This article focuses on unstable pelvic fractures, which are usually caused by high-energy injuries.

The most common high-energy mechanism of injury is a motor vehicle accident. Patients who sustain these injuries not only have the osseous injury but also often have concomitant life-threatening injuries. Younger people are more likely to be involved in these accidents. Early death after these injuries is usually due to hemorrhage, multiple organ system failure, or sepsis. These unstable high-energy pelvic fractures require a multidisciplinary approach to treatment.

History of the Procedure

Before 1950, the treatment of pelvic fractures posed significant problems for orthopedic surgeons. In the past 50 years, however, significant progress has been made in understanding and treating these difficult fractures. The advent of clinically and anatomically significant classification systems has greatly increased the understanding of these injuries.

In 1948, Holdsworth reported on 27 patients with untreated sacroiliac (SI) dislocations and found that only half were able to return to work, with all 27 experiencing residual low back pain.¹ In his 1966 report on 65 patients with double vertical fractures of the pelvis, Raf noted a worse outcome when SI dislocation was present. In the same report, Raf noted a high incidence of nerve injury with posterior fractures through the sacrum.

In 1972, Slatis and Huittinen reported on the late sequelae of unstable pelvic fractures, noting significant problems with pelvic obliquity, impaired gait, disabling low back pain, and signs of persistent lumbosacral plexus damage in 46% of their patients. They concluded that although conservative treatment of pelvic fractures of moderate severity afforded good results, conservative treatment of severe pelvic fractures had significant shortcomings.²

In 1988, Tile reported on 248 patients with pelvic ring injuries.³ He noted that stable pelvic injuries resulted in few long-term problems. In contrast, vertically unstable injuries resulted in many problems, with 60% of patients having residual pain.

Over the past 20 years, significant advances in open reduction of pelvic fractures have been made. In 1989, Matta published his techniques for operative fixation of pelvic fractures.⁴ Routt has popularized percutaneous methods of fixation.⁵

Frequency

Pelvic fractures account for 1-3% of all skeletal fractures and 2% of orthopedic hospital admissions. The frequency of pelvic fractures occurs in a bimodal pattern, with peaks observed in persons aged 20-40 years and later in individuals older than 65 years.

Etiology

High-energy injuries that result in pelvic ring disruption are more likely to be accompanied by severe injuries to the CNS, abdomen, and chest. These are often the results of motor vehicle accidents. The changes made in passenger restraints and an increased frequency of high-velocity motor vehicle trauma have led to a steady increase in the number of pelvic ring injuries observed and treated at trauma centers across the country. With the institution of advanced trauma life support (ATLS) protocols, the treatment of patients with polytrauma has significantly decreased mortality rates. The reported range of mortality rates associated with pelvic ring fractures is 9-20%. The mortality rate among hemodynamically unstable patients has been reported to be 50%, whereas hemodynamically stable patients have a mortality rate of 10%.^6,7,8

Young and Burgess⁹ described different pelvic injury patterns observed with varying mechanisms of injury. With side-impact compression, lateral impaction injuries are observed in the pelvic ring. In head-on type collisions, an anterior-posterior (AP)–directed force results in opening of the pelvic ring and an external rotation force on the innominate bones. Combinations of these mechanisms may also occur.

Pathophysiology

The 2 most commonly used classification systems are those of Tile^10,11 and of Young and Burgess.^9,12 These classifications help the orthopedic surgeon evaluate the stability of the pelvic injury and determine the appropriate treatment.

Tile classification^10,11

Tile proposed a classification based on a continuum of stability.

• Type A fractures are stable and do not fracture through the pelvic ring or soft tissues. The posterior ligamentous arch is intact. These fractures include avulsion fractures, iliac wing fractures, and transverse fractures of the sacrum.
• Type B fractures are rotationally unstable but vertically stable. An incomplete disruption of the posterior pelvic arch is present. This subgroup includes open-book and lateral compression (LC) injuries.
• Type C fractures are vertically and rotationally unstable, with complete disruption of the posterior arch and pelvic floor. The hemipelvis is, thus, completely unstable.

Young and Burgess classification^9,12

Young and Burgess proposed a classification system based on Tile's classification. In this classification, they determined the injury pattern in relation to different mechanisms of injury. The 4 subtypes are anterior-posterior compression (APC), lateral compression, vertical shear (VS), and combined mechanisms (CM). These subtypes have been found to correlate with the resuscitation needs of the patient.

• APC injury results from an anteriorly directed force applied directly to the pelvis or indirectly via the lower extremities (see Image 1). The result is an external rotation force on the innominate bones and an open-book type injury. This classification delineates the severity of the injury by quantifying the amount of ligamentous damage present with radiographs.
  • APC-I injuries result from low- to moderate-energy forces. They result in slight (<2 cm) widening of the pubic symphysis. The sacroiliac joint (SIJ) is ligamentously intact.
  • APC-II injuries are higher-energy injuries that result in tearing of the anterior SI ligaments, as well as tearing of the sacrotuberous and sacrospinous ligaments. The posterior SI ligaments are intact. The pubic symphysis diastasis usually measures greater than 2 cm. These fractures are rotationally unstable and are more likely to be associated with neurovascular injuries, soft tissue complications, and hemorrhage.
  • APC-III injuries are a result of high-energy injuries. The hemipelvis continues to rotate externally until the posterior sacrospinous ligaments are also disrupted. Thus, these injuries result in complete ligamentous dissociation of the involved hemipelvis to the axial skeleton. These injuries are associated with the highest rate of neurovascular complications and blood loss.
• Lateral compression injuries result from lateral impact of innominate bone, with internal rotation of the pelvis toward the midline. The sacrotuberous, sacrospinous, and internal iliac vessels are shortened rather than stretched. The injury sustained to the anterior ring in these injuries is not critical to the weight-bearing function of the pelvis. Because of this, lateral compression injuries are further classified into 3 subsets based on the nature of the injury to the posterior ring.
  • Lateral compression-I injuries are the most common type of lateral compression injury. They result in a transverse fracture of the anterior ring and a cancellous impaction fracture of the sacrum posteriorly. This impaction fracture often goes unidentified. Generally, these injuries are low-energy and stable. They are commonly observed in the elderly population.
  • Lateral compression-II injuries are usually the result of a greater laterally applied force. This fracture pattern often results in a posterior fracture dislocation of the SI joint, which is referred to as a crescent fracture.¹³ This injury involves a combination of ligamentous disruption of the inferior portion of the SI joint and a vertical fracture of the posterior ilium that extends from the middle of the SI joint and exits the iliac crest. The posterior superior iliac spine remains firmly attached to the sacrum via the superior portion of the posterior ligamentous complex. The remaining anterior fragment is more mobile to internal rotation but remains relatively stable to external rotation and vertical forces.
  • Lateral compression-III injuries usually occur when an individual receives a laterally directed force on one side of the pelvis and is trapped against an immobile object on the contralateral side. This results in a lateral compression injury pattern on the side of the laterally directed force and an external rotation injury on the contralateral side. The ligamentous injury pattern observed on the contralateral side is the same as that in the APC injuries, with disruption of the sacrospinous, sacrotuberous, and anterior SI ligaments. Most hemorrhages observed in these fractures occur on the side contralateral to the injury force, where tensile forces are acting.
• A vertical shear injury results in vertical translation of the hemipelvis (see Image 2). The typical mechanism for this injury involves a fall from a height and landing on an extended limb. Anteriorly, the injury usually involves the pubic symphysis, but fractures through the pubic rami are not uncommon. Posteriorly, the force is directed through the SI joint, causing a complete disruption of this joint.
• Combined-mechanism injuries have features of at least 2 of the above-mentioned categories. The most common is the combined lateral compression and VS injuries.

Denis zone of injury classification¹⁴

Discussion of pelvic fractures is not complete without mentioning sacral fractures. Denis classified these fractures according to their zone of injury. In a zone I injury, the sacral alar region is involved. In zone II injuries, the sacral foramina are involved (see Image 3). Zone III injuries involve the central sacral canal. Transverse fractures of the sacrum may also occur.

Presentation

Upon admission to the emergency department (ED), the treatment of a patient with polytrauma with a pelvic ring injury requires a multidisciplinary approach, including the attention of specialists from general surgery and orthopedics and emergency care personnel. The initial evaluation should include the ABCs (airway, breathing, circulation) of trauma care as described in the ATLS protocols. Although the initial history is often lacking in such patients, gathering as much information as possible is important. Especially important to the orthopedic evaluation is the patient's mechanism of injury. This information assists in determining the energy with which the injury has occurred, as well as in predicting the injury pattern.

Several clinical signs may help with diagnosis before radiography is performed. The Destot sign, a superficial hematoma above the inguinal ligament, in the scrotum, or in the thigh, can indicate a pelvic fracture. The examiner should look for a rotational deformity of the pelvis or lower extremities. Leg-length discrepancies may also be present with pelvic fractures. The practice of compressing and distracting the iliac wings and applying manual traction to determine stability lacks specificity and should be avoided.

Neurologic injuries are commonly overlooked. The lower extremities must undergo a thorough neurovascular examination. Prevalence of neurologic injury in pelvic fractures has been reported to be 3.5-13%.

Sacral fractures and SI disruptions have a particularly high incidence of neurologic injury. According to the Denis classification of pelvic fractures,¹⁴ zone I sacral fractures are associated with a 5.9% incidence of neurologic injury. Zone II injuries have a 28% neurologic injury rate, usually involving L5, S1, and S2 nerve roots. Zone III injuries have a 56% incidence of neurologic injury. Such injuries frequently involve the bowel and bladder and may also cause sexual dysfunction.¹⁵

All patients with sacral fractures must undergo vaginal and rectal examinations in the ED. Open pelvic fractures can communicate directly with the rectum, vagina, or skin laceration and carry a mortality rate of up to 50%. Many lacerations are missed if such examinations are not performed. A urethral disruption can also be revealed as a high-riding prostate on the rectal examination. The perineal area should be examined for blood at the meatus, which is a sign of a possible urethral tear.¹⁶

Indications

The treatment goals for unstable pelvic fractures are the same as those for other bones—a healed fracture with the prevention of nonunion, malunion, and other defined complications. The initial priority in a hemodynamically unstable patient is aggressive resuscitation and prevention of further hemorrhage. External fixation is indicated as the immediate treatment in a hemodynamically unstable patient with an unstable pelvic fracture.

Open reduction and internal fixation (ORIF) is preferred for definitive management and has been demonstrated to provide superior results. Operative indications include diastases of pubic symphysis greater than 2.5 cm, sacroiliac joint dislocations, displaced sacral fractures, crescent fractures, posterior or vertical displacement of the hemipelvis (>1 cm), rotationally unstable pelvic ring injuries, sacral fractures in patients with unstable pelvic ring injuries that require mobilization, and displaced sacral fractures with neurologic injury.

Relevant Anatomy

A firm knowledge of pelvic anatomy is critical to understanding fracture patterns and determining treatment goals. The 3 bones that compose the pelvic ring are the sacrum and the 2 innominate bones. Each innominate bone is formed from the fusion of 3 ossification centers (ie, ilium, ischium, pubis) that join at the triradiate cartilage of the acetabulum. The innominate bones join the sacrum posteriorly at the sacroiliac joints and anteriorly at the pubic symphysis.

The posterior sacroiliac ligaments run from the sacrum to the posterior iliac spines and are the strongest ligaments in the body. The sacrotuberous ligaments consist of a strong band that runs from the posterolateral sacrum and dorsal aspect of the posterior iliac spine to the ischial tuberosity. The sacrotuberous ligaments and the posterior sacroiliac ligaments maintain the vertical stability of the pelvis. The sacrospinous ligaments run from the lateral edge of the sacrum and coccyx, separate the greater and lesser sciatic notches, and insert on the ischial spine. The iliolumbar ligaments run from the L4 and L5 transverse process to the posterior iliac crest to provide stability between the spine and the pelvis.

An understanding of the location of major nerves and vessels in relation to bony anatomy is particularly important with the more recent development of percutaneous techniques. The sciatic nerve is formed by the roots from the lumbosacral plexus (L4, L5, S1, S2, S3) and exits the pelvis deep to the piriformis muscle. The lumbosacral trunk is formed by the anterior rami of L4 and L5 and crosses the anterior sacral ala and the SI joint. Fractures of the sacral ala or dislocations of the SI joints are most likely to injure the lumbosacral trunk. The L5 nerve root exits below the L5 transverse process and crosses the sacral ala 2 cm medial to the sacroiliac joint and may be injured during the anterior approach to the SI joint.

Pelvic fractures are frequently associated with large amounts of blood loss. The internal iliac artery (hypogastric artery) is the most important vascular structure in pelvic trauma. The anterior division consists of the inferior gluteal artery, the internal pudendal artery, the obturator artery, the inferior vesicular artery, and the middle rectal artery. The posterior division consists of the superior gluteal artery, iliolumbar artery, and lateral sacral artery.

The superior gluteal artery is the largest branch of the internal iliac artery. It courses along the sacroiliac joint and exits through the greater sciatic notch superior to the piriformis. The superior gluteal artery supplies the gluteus medius, gluteus minimus, and tensor fascia lata muscles. The superior gluteal is the most commonly injured artery in pelvic fractures. Most bleeding after pelvic fractures results from venous injury. The pelvic viscera lie on a large thin-walled venous plexus that drains into the internal iliac vein. Massive bleeding may result from disruption of this venous plexus. Other neurovascular structures that lie in close proximity to the bony pelvis may be damaged when a pelvic fracture occurs.

The close relationship between the urogenital tract and the bony pelvis results in a high incidence of urinary tract injuries. Bladder rupture, diagnosed with a cystogram (see Image 4), and posterior urethral injuries are the most common injuries. Signs of bladder injury include inability to void despite a full bladder, blood at the urethral meatus, high-riding or abnormally mobile prostate, and an elevated bladder. A retrograde urethrogram should be obtained to exclude urethral injury before insertion of a Foley catheter if an anterior pelvic disruption is present or any sign of urethral injury exists (see Image 5).

Anatomic differences between males and females result in a higher incidence of urethral injuries in males. The 3 portions of the male urethra include the prostatic portion, the membranous portion, and the bulbous portion. The bulbous urethra, located inferior to the urogenital diaphragm, is the most common site of injury. In contrast, the female urethra is short, not rigidly fixed to the pubis or pelvic floor, more mobile, and less susceptible to injury from shear forces. If the urethra is ruptured, retrograde urethrography dye extravasates into the perineum. Impotence may occur in 25-47% of male patients with urethral rupture. Impotency is likely secondary to damage of parasympathetic nerves (S2-4). Note that the absence of meatal blood or a high-riding prostate does not exclude a urethral injury.

Bladder injuries may result from bony spicules caused by pubic rami fractures, from blunt force that causes rupture, or from shearing injuries. The superior and upper posterior portions of the bladder are covered by peritoneum. The remainder of the bladder is extraperitoneal and covered with loose areolar tissue. Intraperitoneal ruptures usually require operative repair, whereas extraperitoneal ruptures are managed nonoperatively unless laparotomy is being performed. Extraperitoneal bladder ruptures are typically managed with suprapubic catheter drainage and broad-spectrum antibiotics. Cystography is performed before catheter removal to verify healing. Eighty-seven percent of ruptures heal within 10 days, and virtually all ruptures heal within 3 weeks.

Contraindications

ORIF is contraindicated for patients who are unstable and critically ill or who have severe open fractures with inadequate wound debridement, crushing injuries, and placement of a suprapubic tube in the operative field. Additionally, a Morel-Lavalle lesion can be considered a contraindication to ORIF. This lesion is identified on the basis of a fluctuance under the skin of the involved area.

Contusions and abrasions are often associated with this lesion. It represents a large area of hematoma and fat necrosis under degloved skin. The lesion results from shearing of the subcutaneous tissue from the underlying fascia. Although the Morel-Lavalle lesion is a closed injury, it is associated with high rates of bacterial contamination and, thus, must be treated with debridement and drainage before operative intervention is considered. Specific contraindications for percutaneous fixation include a dysmorphic upper sacrum, obesity, skin compromise, and poor fluoroscopic images.

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