3.7 Pelvic ring
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1 Introduction
Pelvic ring disruptions in younger patients are typically high-energy injuries resulting from traffic accidents, falls from great height, or crush traumas. Very often, these patients are multiply injured, need hemodynamic resuscitation and provisional pelvic stabilization with a pelvic binder, clamp or another type of external fixation. Selective angiographic arterial embolization and pelvic packing are often indicated [1].
Fragility fractures of the pelvis present a totally different clinical picture. They occur in frail, older patients and are the result of a low-energy trauma such as a ground-level fall. In some patients, the history of their injuries is not obtainable. Repetitive “harmless” events such as the transfer from the bed to a chair or from a chair to the toilet, sneezing, coughing, which may not be regarded as traumatic, have been described as causing fragility fractures of the pelvis [2].
Pelvic ring injuries in advanced age may also result from a high-energy trauma. A typical accident mechanism is a trauma from being struck by a vehicle while crossing the street. These patients find themselves quickly in a life-threatening situation; resuscitation must follow the rules of advanced trauma life support similar to younger adults [3]. In this chapter, we discuss the characteristics, diagnostic, and therapeutic measures pertaining to fragility fractures of the pelvis. In this chapter, “fragility fractures of the pelvis” is abbreviated as FFP; note that this abbreviation is used for “fragility fracture patient” in other chapters.
2 Epidemiology and etiology
In some countries, the incidence of hip fractures is declining while the number of pelvic and acetabular fractures is increasing. In the US, hip fractures peaked in 1996 and declined by 25.7% until 2010. During the same 18-year period, pelvic fractures increased by 24%. Absolute numbers, however, remained different with 167,000 hip fractures and 33,000 pelvic fractures in 2010 [4]. In Finland, the age-adjusted incidence of hip fractures has also steadily declined since 1997. From 1970 to 2013, the number of age-adjusted incidences of pelvic fractures has increased from 73 to 364. The incidence increased in all age groups (ie, ages 80–84 years, 85–89 years, and 90+ years) of women and men during the entire study period. If both the fracture incidence and rate of the aging population continue to rise at the current pace, the number of low-trauma pelvic fractures in Finland will be 2.4 times higher in 2030 than it was in 2013 [5].
Both advancing age and comorbidities are associated with the increase of the risk of suffering a fragility fracture of the pelvic ring (FFP). Many patients have a history of osteoporosis, vitamin D deficiency, long-term immobilization, long-term glucocorticoid use, pelvic irradiation for malignancy, or bone graft harvest at the posterior ilium for lumbar spine surgery ( Fig 3.7-1 ) [6].
Fragility fractures of the pelvic ring occur in osteoporotic bone. With increasing age, bone mass is decreasing continuously. Wagner et al [7] demonstrated that this decrease is following a specific and consistent pattern in the sacrum. The sacral body is far less affected than the sacral ala. In advanced cases, areas of very low bone mineral density without any bone, called an alar void, can be seen in the region lateral of the S1 and S2 neuroforamina ( Fig 3.7-2 ).
The leading symptom in patients who have suffered an FFP is pain in the pelvic region. Sitting and standing are difficult or impossible, while lying quietly in bed minimizes the pain level. Most patients are unable to walk. A minority are still able to walk short distances with walking aids. Pain typically starts immediately after the fall and has an acute and sharp character. In some patients, history of pain is longer and related to previous events, which have been unrecognized, undiagnosed, or inadequately treated ( Case 1: Fig 3.7-3 ).
CASE 1
Patient
A 75-year-old woman sustained a right anterior pelvic ring fracture after slipping from a chair, 4 weeks before admission.
Comorbidities
No relevant comorbidities
Treatment and outcome
The primary x-ray revealed a right superior and inferior pubic rami fracture ( Fig 3.7-3a ). Initially, treatment was nonoperative. But the patient had intractable pain which increased over time. Two months later, bilateral sacral ala fractures and another anterior pelvic ring fracture on the left side were diagnosed on a pelvic computed tomographic scan ( Fig 3.7-3b–d ). She was seen in multiple clinical departments, was bedridden because of pain, and developed pressure ulcers on both heels. She also developed recurrent urinary tract infection and weight loss. Fixation with two iliosacral screws in S1 helped lessen the pain, and mobilization with weight bearing as tolerated was started ( Fig 3.7-3e ). Two months later, the fractures seemed to have healed. The patient was very satisfied, completely pain free, and walked without crutches ( Fig 3.7-3f ).
3 Diagnostics
3.1 Physical examination
Pain is localized at the pubic symphysis, the groin, and/or in the posterior pelvis or the low back. In the latter cases, the physician may be confused and focus on diagnostic examinations of the lumbar spine:
Manual compression on both iliac wings enhances pain intensity dramatically without demonstrating major instability. Direct palpation of the pubic symphysis, the groin, and the sacrum will additionally provoke pain.
Inspection of the skin and soft tissues around the pelvic ring, including the low back and the perineal region, is necessary to rule out local infections or decubitus ulcers.
Neurological and vascular status of the lower extremities should be evaluated.
3.2 Creeping hemorrhage
Hemodynamic instability due to continuing bleeding after low-energy pelvic trauma is not typical, but has been described [8, 9]. There is an eightfold increase in odds of pelvic hemorrhage in patients older than 55 years ( Case 2: Fig 3.7-4 ).
Especially in patients taking anticoagulants, there must be a high index of suspicion for continuing bleeding. Arteriosclerosis impairs the ability of vasospasm with less chance of spontaneous cessation of arterial bleeding.
CASE 2
Patient
An 81-year-old woman suffered a left superior and inferior pubic rami fracture after a fall at home.
Comorbidities
Atrial fibrillation
Cardiac insufficiency
Treatment and outcome
Nonoperative treatment with pain medication was started. The hemodynamic situation of the patient deteriorated within the first few hours after admission. A swelling above the pubic symphysis was noticed.
An x-ray of the pelvis showed a slightly displaced superior and inferior pubic ramus fracture ( Fig 3.7-4a ). Transverse computed tomographic cuts through the anterior pelvic ring were performed showing the left-sided superior pubic ramus fracture and a large hematoma inside the small pelvis, which stayed in direct connection with the fracture ( Fig 3.7-4b–c ). The patient was taken to the angiography ward where an active bleeding of the pubic branch of the left inferior epigastric artery was discovered ( Fig 3.7-4d ). A selective embolization and coiling was performed ( Fig 3.7-4e ). The hemodynamic situation of the patient improved. She was taken to the operating room 4 days later for operative removal of the hematoma. The patient recovered well and was discharged 18 days after admission (Courtesy of Dietz et al [9]).
It is recommended to monitor the hemodynamic condition of these patients for at least 24 hours. A flowchart for early clinical and radiological monitoring of patients with FFP is presented in Fig 3.7-5 [9]. In case of bleeding, arterial angiography with selective embolization represents a highly effective treatment of choice. Patients are at risk of exsanguinating with delayed diagnosis and undertreatment.
3.3 Imaging
3.3.1 Plain x-rays
AP pelvic x-ray
Fractures of the superior and inferior pubic rami or the pubic bone near the symphysis are easily recognized. In case of a lateral impact, the fracture line at the superior pubic ramus runs horizontally and there is a slight overriding of the fracture fragments, the lateral fracture fragment being displaced medially ( Fig 3.7-6a ).
Inlet and outlet views
There is controversy whether inlet and outlet views should be taken in this patient cohort. Some authors recommend taking them as a reference for a later follow-up. Others rely on computed tomographic (CT) scans in case of any fracture visible on the AP pelvic x-ray. Computed tomographic scans may also be added to AP x-rays during follow-up.
The inlet view gives a good idea of the amount and direction of rotation of the innominate bone. Integrity of the inner curve of the innominate bone and the anterior cortex of the sacrum can best be analyzed in the inlet view ( Fig 3.7-6b ). The outlet view gives the best information about the posterior pelvis, the shape and symmetry of the sacrum, the neuroforamina and the sacroiliac joints ( Fig 3.7-6c ). We recommend taking these three views as a reference for later follow-ups.
The large, often obese soft-tissue envelope, bowel content, and bowel gas overlie bony structures and joints. Moreover, due to rarefaction of cortical and cancellous bone, fissures and nondisplaced fractures may not be recognized on plain x-rays.
Posterior pelvic ring pathology may be missed with inadequate treatment as consequence [10]. Additional pelvic fractures may occur and enhance complexity and instability ( Fig. 3.7-7 ).
3.3.2 Computed tomographic scan
A pelvic CT scan is recommended when a lesion of any kind of the pelvic ring has been diagnosed on plain x-rays. In a cohort of 245 patients with FFP, more than 80% had a posterior pelvic ring fracture. When only a plain x-ray is obtained on admission, there is a high risk of missing posterior pelvic ring fractures [11].
In coronal reconstructions, a fracture of the lateral mass of the sacrum is sometimes better seen than in transverse sections. A horizontal sacral fracture with more or less severe angulation can only be recognized in sagittal reconstructions ( Fig 3.7-8 ).
In some patients, signs of an older injury may be visible. Bone resorption at a fracture site is a sign of chronic instability, and callus formation is a sign of bone healing. Chronic instabilities at or around a joint may end in bone resorption, joint widening, inclusion of nitrogen bubbles, and free intraarticular or periarticular bone fragments ( Fig 3.7-9 , Fig 3.7-10 , Fig 3.7-11 ).
3.3.3 Magnetic resonance imaging
This is the most sensitive examination and can detect bone bruise within the sacrum, fissures, and fractures before they become visible using other modalities ( Fig 3.7-12 ). Magnetic resonance imaging (MRI) may be indicated where conventional diagnostic measures cannot explain the clinical picture or the persistent complaints of pain. If pathology is detected with MRI, it rarely has consequences in terms of an operative treatment. Differentiation between bone marrow edema and malignancy is also possible with MRI [12]. With MRI, studies demonstrate up to 95% involvement of the posterior ring.
4 Classification
The Tile [13], AO/OTA Fracture and Dislocation [14], and Young-Burgess [15] classifications have been developed to distinguish different types of high-energy pelvic ring lesions. The Tile [13] and AO/OTA [14] classifications distinguish rotationally unstable from rotationally and vertically unstable injuries after AP, lateral, or vertical impacts. According to the direction of traumatic force, the Young-Burgess classification [15] differentiates AP displacement, lateral compression, vertical shear, and combined pelvic ring injuries. The Denis classification divides the sacrum into three zones. Denis I refers to the sacral ala, Denis II to the zone around the neurforamina and Denis III to the sacral body, medial to the neuroforamina [16].
High-energy pelvic trauma is complicated by additional injuries of neurological and vascular structures, hollow organs, and the skin, with additional impacts on prognosis and outcomes.
In contrast, low-energy FFPs have completely different trauma mechanisms. Concomitant injuries of the soft tissues are rare. It is not the direction of the traumatic impact but the areas of very low bone density that are responsible for the fracture morphology [17]. Instability of FFP may increase over time, when the original lesion has been overlooked or undertreated ( Fig 3.7-7 ). This is unique to FFP. The abovementioned characteristics of FFP led to the development of a new, specific, and comprehensive classification system. The classification of FFP is based on an analysis of both conventional x-rays and CT data of 245 patients, 65 years or older with FFPs [18].
The most important criterion is the degree of instability. Instability is defined as the inability of a structure to withstand physiological loads without displacement. Also in older adults, this criterion is crucial for identifying an indication for surgery. Fracture displacement is the leading hint of instability. Nondisplaced lesions are characterized by a crush zone or a fracture without deformation. Displaced lesions are characterized by a crush or a fracture with deformation of the anatomical landmarks. The second criterion is the localization of the fracture in the posterior pelvis. The localization of the instability determines type and invasiveness of the surgical treatment.
Four different categories with slight, moderate, high, and highest instability were identified, namely types I–IV. The subtypes were characterized by a, b, or c. The main goals of treatment are restoration of prefracture stability and mobility. Due to instability, FFP generates intense pain and immobilization. Immobilization leads to rapid deterioration of the physical condition of the patient with higher morbidity and mortality due to secondary complications. The decision for an operation is needed, and the decision on which type of osteosynthesis should be performed is based on the severity of instability of the pelvic ring. It is therefore of utmost importance to thoroughly analyze the characteristics of the fractures and classify them within the new classification system, as this will ultimately form the basis for decision making.
In the following topics, the different types and subtypes of FFP are presented and a recommendation for treatment is given for all types. The operative techniques to be used are described in topic 7 of this chapter.
4.1 Fragility fracture of the pelvis type I
Fragility fractures of the pelvis type I are anterior pelvic ring fractures without involvement of the posterior pelvic ring. These are the lesions with the lowest degree of instability. Type Ia are unilateral ( Fig 3.7-13 ) and type Ib are bilateral anterior lesions ( Fig 3.7-14 ). The latter is much less frequent. Type I comprised 17.5% of all FFP in the authors’ case series. Conversely, more than 80% of patients had a posterior pelvic ring injury. These findings support the use of CT evaluation for all low-energy pelvic ring fractures with anterior pelvic ring fractures, as there is a high risk of a concomitant posterior ring fracture that is often missed on conventional x-rays.
Fragility fracture of the pelvis type I should be treated nonoperatively. The authors hospitalize the patient and perform hemodynamic monitoring for the first 24 hours (see topic 4.2 in this chapter). When mobilization is not possible or delayed due to significant pain, pelvic stability should be reevaluated. If additional fractures are detected or primarily nondisplaced fractures displaced, operative management may be considered. External fixation can be regarded as a minimally invasive stabilization of anterior pelvic ring lesions. But there is little data on morbidity and outcome of pelvic external fixation in older adults. We assume that patients requiring anterior stabilization have posterior pelvic ring instability as well. Secondary fractures of the posterior ring may be induced over time in the stiff, older pelvis after initial anterior disruption ( Fig 3.7-7 ).
4.2 Fragility fracture of the pelvis type II
Fragility fractures of the pelvis type II are characterized by nondisplaced posterior pelvic ring fractures. Type II lesions suffer more instability than type I lesions. Type IIa is a nondisplaced isolated posterior pelvic ring fracture ( Fig 3.7-15 ), type IIb is a sacral crush with anterior disruption ( Fig 3.7-16 ), and type IIc is a nondisplaced sacral, sacroiliac, or iliac fracture with anterior disruption ( Fig 3.7-17 ). Type II fractures account for more than half of FFP [18]. Sacral fractures or crush zones of the sacral ala are much more frequent than sacroiliac dislocations or fractures of the posterior ilium. Fractures through the sacrum have unique and consistent fracture patterns [17]. The reason for this is the decrease in bone mass in the sacral ala, lateral to the neuroforamina in older patients. This has been demonstrated in a statistical model of the sacrum by Wagner et al [7, 19] based on CT data of 92 older Caucasians.
Fragility fractures of the pelvis type II must be regarded as posterior pelvic fractures before completion and displacement. They are more unstable than isolated anterior lesions but less unstable than displaced posterior lesions. They are typically associated with anterior instabilities. The traumatizing vector of FFP type IIb and FFP type IIc comes from a lateral direction, reflecting a sideways fall from a standing position with a lateral compression injury.
Nonoperative treatment with weight bearing as tolerated is initiated if patients are able to be mobilized within a few days. As the pelvic ring is broken posteriorly and anteriorly, we expect more pain and a longer rehabilitation time compared to FFP type I. It is important to listen to the complaints of the patient. If, after a maximum of 1 week, the pain is subsiding and the patient is able to mobilize independently, nonoperative therapy is continued. Followup x-rays after mobilization, and at 3, 6, and 12 weeks are recommended. Secondary fracture displacement with a higher degree of instability and transformation into a higher FFP type must be ruled out. Displacement of fractures of the posterior pelvic ring leads to a higher degree of instability and to classification in a higher FFP category. Nonoperative therapy must then be switched to operative therapy.
Complaints are another reason for changing therapy. When there is intense pain and patient transfer out of bed is impossible, operative fixation is recommended ( Case 3: Fig 3.7-18 ). If the fracture fragments of the posterior pelvic ring are not displaced, percutaneous stabilization techniques such as iliosacral screw fixation seem most useful.
CASE 3
Patient
An 85-year-old woman had a fall at home and sustained a fragility fracture of the pelvic ring type IIc.
Comorbidities
Hypothyreosis
Arterial hypertension
Treatment and outcome
The AP x-ray of the pelvis showed a left-sided pubic ramus fracture. Due to intense pain, mobilization was not possible for 3 weeks ( Fig 3.7-18a ). Inlet and outlet views were obtained ( Fig 3.7-18b–c ).
A coronal computed tomographic (CT) cut through the sacrum was performed and showed a complete fracture of the left sacral ala (white arrows in Fig 3.7-18d ). The transverse CT cut through the anterior pelvic ring showed the left-sided pubic fracture ( Fig 3.7-18e ). After a 3-week nonoperative treatment, operative fixation was performed. The sacral alar fracture was fixed with two iliosacral screws, the pubic ramus fracture with a retrograde transpubic screw. The AP x-ray of the pelvic ring after 2 years showed complete healing of the anterior and posterior pelvic ring ( Fig 3.7-18f ). Another pelvic inlet and outlet view were obtained ( Fig 3.7-18g–h ).
4.3 Fragility fracture of the pelvis type III
Fragility fractures of the pelvis type III are characterized by a displaced unilateral posterior injury combined with an anterior pelvic ring lesion. Displaced unilateral posterior lesions represent the smallest subtype in the group of 245 FFP, occurring in 11% [18]. They have a higher instability than type II lesions. Displacement must be assessed on both CT transections and conventional x-rays. Major displacement in the anterior pelvic ring must always be combined with some displacement in the posterior pelvic ring. Also, larger fracture gaps and changes of anatomical landmarks are signs of displacement.
Fragility fracture of the pelvis type IIIa involves a displaced unilateral ilium fracture ( Fig 3.7-19 ).
Fragility fracture of the pelvis type IIIb is a displaced unilateral sacroiliac fracture dislocation ( Fig 3.7-20 ).
Fragility fracture of the pelvis type IIIc is a displaced unilateral sacral fracture ( Fig 3.7-21 ).
It cannot be expected that these lesions will heal spontaneously. Due to severe pain, the patients are bedridden and mobilization is impossible. Operative treatment is therefore recommended as an urgent procedure. The type of internal fixation depends on the localization of the posterior instability. With limited displacement of the sacrum, sacroiliac joint, or posterior ilium, percutaneous stabilization is possible ( Case 4: Fig 3.7-22 ). In case of gross displacement or a fracture through the ilium, an open reduction and internal fixation (ORIF) is required ( Case 5: Fig 3.7-23 ).
CASE 4
Patient
An 85-year-old woman sustained a fragility fracture of the pelvic ring type IIIb lesion after a fall at home.
Comorbidities
Hypercholesterolemia
Arterial hypertension
Treatment and outcome
The AP x-ray of the pelvis showed a left-sided displaced superior and inferior pubic ramus fracture ( Fig 3.7-22a ). Pelvic inlet and outlet views were obtained ( Fig 3.7-22b–c ). A transverse computed tomographic (CT) cut through the sacrum showed a fracture-dislocation of the left sacroiliac joint (white arrows in Fig 3.7-22d ) while a transverse CT cut through the anterior pelvic ring revealed the left-sided pubic fracture ( Fig 3.7-22e ). The fracture-dislocation of the sacroiliac joint was fixed with two iliosacral screws and the pubic ramus fracture with a retrograde transpubic screw. The AP x-ray of the pelvic ring after 3 years showed complete healing of the anterior and posterior pelvic ring ( Fig 3.7-22f ). Another inlet and another outlet view of the pelvis were obtained ( Fig 3.7-22g–h ).
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