Pelvic and Acetabular Fractures



Pelvic fractures include disruption of the superior and inferior pubic rami, the acetabulum (hip socket), the iliac wing, and the sacrum. It is also possible to have a serious pelvic injury without fractured bone, as might be seen with a rupture of the ligaments that connect the two pubic rami or the ligaments stabilizing the sacroiliac joint.

 

Fractures of the pelvis can be caused by high-energy trauma, such as a motor vehicle collision, or, in the setting of frailty, a simple fall may be responsible. When a fracture is due to a high-energy mechanism, damage to the internal organs and major blood vessels is common and must be addressed first. The focus of treatment is “life before limb,” using the approach of Advanced Trauma Life Support (ATLS) guidelines. Thereafter, surgical reduction and fixation is often needed. Notably, the initial response addressing hemorrhagic shock in patients with pelvic fractures can include musculoskeletal treatments: emergency pelvic stabilization can compress damaged vessels and stem the bleeding, for example.

 

Even in the absence of pelvic instability, high energy pelvic fractures can be lethal. Death may be caused by associated injuries or from internal hemorrhage. Morbidity among survivors is also high, with residual pain, neurological loss, and functional disabilities commonly seen. Fractures of the acetabulum pose a specific risk for hip arthritis.

 

Low energy fractures, typically involving the pubic rami or sacrum, are usually seen in older or frail patients who fall. Most low energy fractures are stable injuries and can be managed with pain medication and early physical therapy. Particular attention to geriatric management is needed to prevent delirium in the short term and to prevent further falls and fragility fractures that might occur if these issues are not attended to.

 

Last, the pelvis is susceptible to avulsion fractures. Sudden and forcible movements – usually in sports activities – can pull off, or “avulse,” small fragments of bone at the point of ligament and tendon attachments. These injuries often, but not always, need no treatment beyond supportive care.

 

 

Structure and Function

The pelvis is a ring of bones that has two main functions: to provide a mechanically stable connection between the axial skeletal and lower limbs, and to protect the neurovascular, reproductive, and digestive structures within it.

 

The ring is formed by three bones, the left and right innominate bones [see Miscellany, below] and the sacrum (Figure 1) connected by three joints, the left and right sacroiliac joints posteriorly, and pubic symphysis anteriorly. The joints are reinforced by posterior and anterior ligament complexes, and the pelvic floor (Figure 2).

 

The posterior ligament complex includes the very strong posterior sacroiliac ligament, the anterior sacroiliac ligament, and the iliolumbar ligament. The anterior complex includes the symphyseal ligaments. The pelvic floor includes ligaments connecting the sacrum to the ischial spine and the ischial tuberosity (sacrospinous and sacrotuberous ligaments).

 

The innominate bone is a fusion of the ilium, ischium, and pubis. These bones come together at the level of the acetabulum, creating an inverted cup with anterior and posterior walls (Figure 3). The acetabulum articulates with the femoral head to make the hip joint. The acetabulum has anterior and posterior columns as well. The anterior column contains the anterior iliac wing, the superior pubic ramus, and anterior acetabular articular surface. The posterior column spans the greater sciatic notch to the ischial tuberosity. The superior aspect of the acetabulum is the main weightbearing surface and the posterior acetabulum is a key stabilizer of the hip joint - fractures in these areas are at high risk for post-traumatic arthritis.

 

The sacrum is a fusion of five sacral vertebrae and articulates with the spine via L5 vertebral body proximally, the iliac wings bilaterally, and the coccyx distally. The sacrum is intimately related to the L5 nerve root above it and the S1-S4 nerve roots that traverse its foramina.

 

The coccyx (tailbone) comprises three to five separate or fused coccygeal vertebrae attached via the fibrocartilaginous sacrococcygeal symphysis.

 

Figure 1: Annotated pelvic x-ray (x-ray from https://radiopaedia.org/cases/pelvic-radiograph-normal-1). 1) Iliac crest; 2) sacro-iliac joint; 3) posterior-inferior iliac spine; 4) roof of acetabulum; 5) inferior pubic ramus; 6) superior pubic ramus; 7) pubic symphysis; 8) sacrum; 9) obturator foramen; 10) ischial tuberosity; 11) anterior inferior iliac spine; 12) anterior superior iliac spine.

 

Figure 2: Ligaments of the pelvis (modified from Wikipedia, https://commons.wikimedia.org/wiki/Category:Pelvis#/media/File:Sobo_1909_211.png). A) pubic symphysis; B) inguinal ligaments; C) anterior sacroiliac ligaments; D) Iliolumbar ligaments; E) sacrospinous and sacrotuberous ligaments. (Shown but not labeled are the anterior longitudinal ligament of the spine and sacrococcygeal ligaments, among others.)
  
Figure 3: AP x-ray of the pelvis including the articulation between the proximal femur and acetabulum (hip joint) with annotated anatomic landmarks. 1) Anterior acetabular wall; 2) posterior acetabular wall; 3) acetabular roof; 4) iliopectineal line; 5) ilioischial line; and 6) radiographic “tear drop,” representing the thickness between the external and internal aspects of the acetabular walls.

 

 

Patient Presentation

Patients with a pelvic fracture present with groin, lower back, and hip pain which is exacerbated by movement. Weight-bearing is usually not possible with high energy fractures.

 

High energy pelvic fractures often present with additional serious injuries. There are three basic injury patterns (Figure 4): lateral compression fractures; anteroposterior compression fractures (seen in an “open book” or “sprung” pelvis fractures); and vertical shear fractures. Each of these has its own predictable pattern of associated injuries. These basic patterns can also be seen in combination such as the so-called “windswept pelvis,” in which there is compression on the side of impact and opening on the other side.  

 

Figure 4: Patterns of pelvic fractures. Shown in the top row are the three grades of lateral compression: I) an oblique pubic ramus fracture and ipsilateral anterior compression fracture of the sacrum; II) fracture of pubic rami with posterior fracture of the ipsilateral iliac wing; and III) an ipsilateral lateral compression fracture with a contralateral anteroposterior compression fracture. In the middle row are the anteroposterior compression patterns: I) a small, <2.5 cm, pubic diastasis; II) a pubic diastasis >2.5 cm with disruption and diastasis of the anterior part of the sacroiliac joint, with intact posterior sacroiliac joint ligaments; and III) pubic diastasis >2.5 cm along with disruption of both anterior and posterior sacroiliac joint ligaments with dislocation. In the bottom row, an example of a vertical shear fracture is shown, with vertical displacement of hemipelvis, and pubic and sacroiliac joint fractures. This is the most severe and unstable type and is highly associated with visceral injuries. (Note that other patterns of vertical shear - bilateral, for example - are possible.) Reproduced from https://radiopaedia.org/articles/young-and-burgess-classification-of-pelvic-ring-fractures, Dr. Matt Skalski rID:2037824)

 

Patients may be hypotensive due to external bleeding or from internal blood vessel and visceral injuries. A tension pneumothorax, brain or spinal cord injuries may also be the cause of hypotension. It is also very important to be aware of and prevent iatrogenic hypothermia as a cause of hypotension: a completely exposed and undressed patient in the Emergency Room can get cold fast and develop a coagulopathy that compounds the bleeding problems.

 

Evidence of the pelvic fracture and commonly associated injuries includes pelvic deformity, unequal limb lengths, scrotal or labral swelling, and hematomas. A detailed perineal exam is mandatory. Blood at the urethral meatus suggests urethral disruption – and thus bladder catheterization must not be attempted if blood is seen. On rectal examination, a high-riding prostate implies genitourinary disruption. Abnormalities of anal tone, perianal sensation or ano-cutaneous reflexes are suggestive of sacral nerve injury. Blood on rectal or vaginal examination is suggestive of an open fracture.

 

A serious pelvic injury, with instability and severe blood loss, can be present without obvious deformity on physical examination.

 

Elderly people with osteoporosis are also at risk of pelvic fractures from low energy mechanisms such as a fall from a standing height. Low impact pelvis fractures tend to be stable and are compatible with walking. Clues suggesting a fracture include bruising to the pelvic region, scrotum and labia; numbness in thighs or legs; rectal or vaginal bleeding; or more rarely, leg-length inequality.

 

Acetabular fractures usually result from impact of the femoral head into the acetabulum from a fall, or a blow to the flexed knee by a dashboard injury. The fracture pattern depends on the position of the femoral head at the moment of impact. Dislocations of the femoral head can occur anteriorly, posterior, or centrally through the acetabulum into the pelvis. Fractures may involve either the anterior or posterior walls, the anterior and posterior columns, or some combination thereof.

 

It’s also possible to have an avulsion fracture of the pelvis which may occur in the skeletally immature population as well as adults. In a pelvic avulsion fracture, usually a small piece of bone at the site of an apophysis (a secondary growth center that is attached to a tendon or ligament) gets pulled away from the main mass of the bone. Avulsion fracture tends to happen with a sudden muscle contraction. There are five characteristic regions of pelvic avulsion (Figure 5): the ischial tuberosity, by the pull of the hamstring muscles; the inferior pubic ramus by pull of the adductor muscles; the anterior superior iliac spine, caused by pull of the tensor fascia lata; the iliac crest, by the pull of abdominal muscles; and the anterior inferior iliac spine, by the pull of the rectus femoris.

 

Figure 5: Regions of pelvic avulsion: A) the ischial tuberosity, by the pull of the hamstring muscles; B) the inferior pubic ramus by pull of the adductor muscles; C) the anterior superior iliac spine, caused by pull of the tensor fascia lata; D) the iliac crest, by the pull of abdominal muscles; and E) the anterior inferior iliac spine, by the pull of the rectus femoris. (Annotation of a Gray's Anatomy original)

 

 

Objective Evidence

Advanced Trauma Life Support guidelines must be followed for patients with high-energy mechanism of injuries. Serology examination includes complete blood counts, electrolytes and creatinine) glucose, coagulation studies, and group and cross-match. Serial arterial blood gases with pH and lactate levels to monitor tissue oxygenation, circulatory status and response to resuscitation may be indicated.

 

Pelvic injuries are diagnosed on radiographic studies, beginning with plain films. Plain films must be examined not only for fractures but for disruption of the normal relationship between pelvic components (see Figure 6).

 

Figure 6: Tracing the following “lines of the pelvis” can help detect injuries. Top panel (purple): the main pelvic ring and two obturator foramina should be uninterrupted ovals. Middle panel (green): the sacroiliac joints and the symphysis pubis. Bottom panel (red): the acetabulum and the so-called Shenton’s line coursing from the inferior border of the superior pubic ramus along the inferior femoral neck. (modified from Radiopaedia.org, ID: 28928)
 

If a pelvic injury is found, a CT scan is indicated. The CT scan will help determine the stability of the pelvis as well as help identify all fracture lines. CT of pelvis and abdomen can provide critical information regarding source of bleeding and to delineate associated injuries. Sagittal, coronal and 3D reconstructions can provide highly detailed representations of fracture patterns and help with operative planning (Figure 7).

  

Figure 7: A plain radiograph (A) and a 3D bone model produced by reconstructing the axial, sagittal, and coronal two-dimensional CT images (B) of a pelvic fracture. (Reproduced from Yoon, et al, Asian Journal of Surgery Volume 44, Issue 1, January 2021)
 

Angiography is a highly sensitive method to identify (and embolize) arterial bleeding associated with pelvic fractures.

 

MRI is usually not required but may be used to assess avulsions or insufficiency fractures.

 

 

Epidemiology

Pelvic fractures are generally uncommon, only accounting for about 3% of all adult fractures. The most significant pelvic and acetabular fractures occur due to major trauma often due to car crashes, crush injuries, or falls from height. Motorcycle accidents are the most common cause for pelvic fractures.

 

It is common to see less severe, stable fractures in the elderly population, particularly those who may suffer from osteoporosis and frailty. Oftentimes these fractures take place due to a fall from standing and tend to result in an isolated pubic ramus fracture.

 

Teenagers who play high speed sports are particularly susceptible to avulsion fractures, typically involving the hamstrings and the ischium.

 

Sacral fractures are seen in conjunction with pelvic ring injuries in about 40% of cases; about one quarter of these are associated with neurologic injury, with the risk increasing with more medial fracture lines.

 

Acetabular fractures occur in both the young and elderly, with high energy and low energy mechanisms being the cause, respectively. About 30% of patients with acetabular fractures develop post-traumatic hip arthritis.

 

 

Differential Diagnosis

Pelvic fractures are diagnosed definitively on imaging studies. Thus, there is no “differential diagnosis list” per se, but rather there are associated conditions that must be considered and excluded.

  • High energy fractures are associated with chest and visceral injuries, long bone fractures and spinal fractures.
  • Acetabular fractures may have an associated femur fracture or hip dislocation.
  • Psychiatric disease may be present. Pelvic fractures can also be seen with suicide attempts (jumping from great heights). Drugs and alcohol are also commonly involved with fractures from motor vehicle collisions.
  • Low energy injuries are associated with frailty and osteoporosis.

 

 

Red Flags

A high-energy pelvic fracture is itself a red flag for visceral, skeletal, and vascular injury.

 

A low-energy pelvic fracture is itself a red flag for osteoporosis and underlying medical or neurological conditions that lead to falls.

 

 

Treatment Options and Outcomes

Management steps with pelvic fractures are dictated by the energy of the injury, mechanic stability of the pelvic ring, hemodynamic stability, and associated injuries.

 

High Energy Fracture

The management of high energy pelvic fracture centers on maintaining adequate blood pressure to preserve vital organ perfusion until bleeding can be controlled. Resuscitation uses saline, packed red blood cells, platelets, and fresh frozen plasma. Warmed fluids and thermal blankets can help prevent hypothermia.

If the pelvis is unstable, emergency stabilization is required as part of hemorrhage control, yet one should not assume that the pelvic fracture is the only source of hypotension. Simple measures such as a pelvic binder or a sheet tied between the level of the iliac crest and greater trochanter are often very effective to control bleeding by compressing bleeding bone surfaces and reducing pelvic volume creating a tamponade effect. Angiography and embolization is potentially lifesaving but may lead to necrosis of the skin or other organs.

 

Open fractures require early broad-spectrum IV antibiotics; tetanus vaccine or booster; irrigation and dressing followed by surgical debridement and wound management.

 

Once life threatening injuries have been addressed, treatment of a high energy pelvic fracture simply depends on whether the fracture pattern is stable or unstable. Stable fractures of the pelvis can be treated with pain medication and physical therapy alone. Weightbearing status depends on the patient’s overall conditioning and risk of falling.

 

Unstable fractures are treated with surgical intervention (Figure 8) followed by physical therapy. Surgical intervention is tailored to the specific injury pattern and may utilize plates, screws or external fixation. The choice among surgical methods will be influenced by fracture patterns, soft tissue injuries and the need for subsequent procedures. (Operations such as laparotomy, colostomy and genitourinary repair must not be impeded by poorly chosen placement of incisions or fixation hardware.)

 

Figure 8: A plain radiograph (A), 3D CT images (B), and surgical treatment (C) of a pelvic ring injury involving the pubis and left sacroiliac joint. (Reproduced from Yoon, et al, Asian Journal of Surgery Volume 44, Issue 1, January 2021)
 

Further reconstructive options such as acetabular fixation or hip arthroplasty are often best delayed until the patient’s medical condition and the state of their soft tissues have been optimized.

 

Acetabular fractures occurring in the setting of an unstable pelvic ring injury require stabilization of the ring first. Acetabular fractures that involve the weightbearing portion of the acetabulum or those associated with an unstable hip joint are treated surgically, in hopes of reconstructing the articular surface. If the reconstructed joint will not allow early hip joint range of motion, total hip arthroplasty will be required. Total hip arthroplasty can be performed either at the time of pelvic ring fixation or as a delayed procedure. Note that even with anatomic reduction there is a sizeable risk of post-traumatic hip arthritis.

 

The outcomes of a pelvic fracture depend largely on the severity of the fracture itself, any associated hemorrhagic, neurologic, or urogenital injury. Musculoskeletal complications include nonunion, malunion, hardware failure, wound and deep infection, and arthritis. Even with optimal management, many pelvic fractures lead to significant long-term pain and functional restrictions.

 

Thromboembolic complications are of particular concern due to local pelvic injury, coagulopathy associated with major injury and bleeding, and prolonged hospital immobility. Chemical (e.g., anticoagulants), mechanical (e.g., foot pumps) and barrier methods (e.g., vena cava filters) can be used to prevent such complications.

 

Pelvic fractures are unfortunately associated with sexual, bowel and bladder disturbances. These conditions must be actively explored and managed by the medical team, as patients are often too embarrassed to voluntarily disclose them.

 

Low Energy Fractures

Low energy injuries usually result in isolated stable fractures of the pelvic ring but in older populations, other concomitant fractures are common and must be anticipated and excluded. Treatment of low energy, stable ring fractures is usually non-operative.

 

Initial hospitalization (or “hospital at home”) care must address age-appropriate pain control (avoiding medications that can cause falls or mental status changes), mobilization with weightbearing as tolerated, and physical therapy. The patient’s social and physical environments should be assessed. For patients that are unable to mobilize, operative management may be considered and balanced against the risks of prolonged pain and immobility. Outcomes are governed by the patient’s other medical conditions, especially frailty, but full recovery is an achievable goal.

 

Avulsion Fractures

For younger patients with an avulsion fracture, weightbearing with crutches for a few weeks is often sufficient. In the rare occasion that the bone fragments are displaced too much that healing is precluded, surgery is recommended.

 

 

Risk Factors and Prevention

Injuries to the pelvis are commonly seen in high energy trauma, often involving motor vehicle collision, which accounts for over half of pelvic injuries. Driving without a smartphone in hand is probably the best way to prevent motor vehicle collision.

 

Preventing osteoporosis and preventing falls can help prevent low energy pelvic fractures.

 

 

Miscellany

The pioneering work on pelvic and acetabular fractures is attributable to Emile Letournel and Robert Judet, two French surgeons from Paris, whose work in the 1960’s laid the foundations for assessment, classification, and surgical treatment in today’s practice.

 

Corona mortis means “crown of death” and is the name given to an anatomical variant artery present in 25-35% of patients. It is an anastomosis between the obturator and external iliac arteries. This anastomosis lies close to the pubic bone near the symphysis. It is at risk of damage in pelvic fractures and surgical exposures near the inguinal canal (pelvic fixation and hernia repairs).

 

The coccyx is formed from the fusion of vestigial vertebrae. It serves no known function, and the various muscles, tendons and ligaments of the pelvic floor that attach to the coccyx also attach to adjacent structures. The coccyx is thus easily forgotten (and relegated, as here, to the “Miscellany” section). Nonetheless, a coccygeal fracture can be very painful, and produce a condition known as coccydynia. Treatment may require strong analgesics, pressure-relieving devices such as “donut cushions.” or even surgical excision (coccygectomy).

 

The designation of bone formed by the fusion of the ilium, ischium, and pubis as “innominate” is a bit of an oxymoron, as the word “innominate”  means “nameless” in Latin. 

 


Key Terms

Pelvis, Pelvic Ring Injury, Acetabulum, Sacrum, Pelvic Fracture

 

 

Skills

Assess patients for pelvic fractures and associated injuries/comorbidities. Follow ATLS guidelines and communicate/collaborate with the trauma team. Assess for pelvic ring stability. Assess hemodynamic stability. Apply simple emergency pelvic ring stabilization measures. Evaluate imaging studies including x-rays and CT scans to help determine the severity of the injuries.