➢ Fragility fractures of the pelvis exhibit different morphological characteristics and occur as a result of different mechanisms than high-energy pelvic ring lesions. The degree of instability may increase over time.
➢ A new comprehensive classification system distinguishes between different degrees of instability and different locations of the fractures in the posterior pelvic ring.
➢ The majority of fragility fractures of the pelvis have nondisplaced components in the posterior part of the pelvic ring. These types of fragility fractures are treated nonoperatively with pain therapy and mobilization as tolerated. A multidisciplinary approach is needed to ameliorate the general condition of the patient and to treat underlying metabolic abnormalities.
➢ Because one of the primary goals of treatment is functional recovery, restoring stability is more important than restoring perfect anatomy.
➢ Less-invasive stabilization techniques are preferable to open reduction and internal fixation for the treatment of posterior and anterior pelvic ring instabilities.
Because of longer life expectancy, the number of elderly persons is rapidly increasing in industrialized countries. The number of age-related diseases and injuries is increasing accordingly. A Nationwide Inpatient Sample from the United States, which recorded >600 million Medicare-paid hospital discharges from 1993 to 2010, showed a 24% increase in pelvic fractures during this period1. Similarly, a recent Finnish study demonstrated that the age-adjusted incidence of pelvic fractures increased from 73 to 364 per 100,000 persons with an age of ≥80 years2. The authors of that study calculated that the number of low-energy pelvic fractures in that population will be 2.4 times higher in 2030 than it was in 2013. Pelvic fractures have a major impact on the quality of life of the elderly as they lead to intense pain, immobility, and loss of independence.
Definition and Etiology
The World Health Organization defines a fragility fracture as “a fracture that is caused by an injury that would be insufficient to fracture normal bone; the result of reduced compressive and/or torsional strength of bone.”3 Fragility fractures of the pelvis occur in frail persons after low-energy trauma, such as domestic falls. In some cases, the traumatic event is not remembered by the patient. The most frequent underlying cause is osteoporosis, a condition marked by loss of bone mass and a propensity for fracture4. Other pathological conditions (e.g., vitamin-D depletion5, a history of long-term immobilization, rheumatoid arthritis6, long-term corticosteroid use, pelvic irradiation7, and bone harvesting at the posterior aspect of the ilium8) also increase the risk of such an injury.
Specific Characteristics of Fragility Fractures of the Pelvis
Low-Energy Trauma Mechanisms
Pelvic disruptions are the result of high-energy trauma. Large displacements of bone fragments cause vessel ruptures, damage to neurological structures, and disruption of intrapelvic organs. The type and extent of associated injuries are decisive in determining the need for and character of emergency treatment, definitive treatment, and long-term results9. In elderly individuals, low-energy traumatic events are more common. Low-energy accidents do not cause substantial bleeding, damage to intrapelvic organs, or damage to soft-tissue envelopes. Hemodynamic instability is seldom noted in association with fragility fractures of the pelvis; in 2 large case studies, none of the patients sustained life-threatening hemodynamic instability10,11. Damage-control measures are not needed. However, for patients receiving anticoagulation therapy, there must be a high index of suspicion for bleeding, and hemodynamic monitoring is recommended for at least 24 hours12. Delayed diagnosis and treatment of arterial bleeding substantially increases mortality. Selective angiography and embolization is the treatment of choice in cases of active arterial bleeding13.
Altered Bone Strength
With advanced age, bone strength decreases and fracture risk increases accordingly. Changes in bone mineral density with aging are not equally distributed throughout the pelvis. Using 3-dimensional (3D) statistical modeling techniques, Wagner et al. demonstrated that sacral alae are especially affected by severe bone loss, leading to alar voids in which bone resorption is complete and fatty bone marrow is present14,15. Leung et al., with use of finite-element models, found that reduction of bone density caused an increase of principal strain patterns in the sacral ala, the greater sciatic notch, the supra-acetabular roof, and the superior pubic rami. Decreases of both the cortical-surface and interior bone densities at these sites of the pelvis were found to be indicators for the risk of insufficiency fracture16. These locations correspond to typical sites for the occurrence of fragility fractures of the pelvis and are the reason for the typical fracture patterns of fragility fractures of the pelvis. Linstrom et al. described similar patterns in a series of 108 patients17.
To our knowledge, data on age-related changes in the strength of the ligaments of the pelvic ring are not available. However, Hammer et al. demonstrated that the iliotibial tract becomes less elastic with age, as shown by an increasing Young modulus18. In patients with fragility fractures of the pelvis, a collapse of osseous structures occurs but the ligaments remain intact and continue to form an envelope around the failed bone10,19.
Specific Fracture Characteristics
Specific fracture patterns are observed in association with fragility fractures of the pelvis. A so-called lateral compression fracture pattern with a horizontal and overriding superior pubic ramus fracture and a crush or nondisplaced fracture in the sacral ala is frequently seen10. Bilateral fractures through the sacral ala are also often observed17. Fracture lines follow areas of lowest sacral bone mass and highest strain15,17. Large fracture displacements are rare. Other characteristics that have been identified in association with fragility fractures of the pelvis (e.g., bilateral fractures through the iliac wing and chronic fractures in which the complex injury pattern results in complete pelvic ring collapse) cannot be classified with use of conventional systems20-22.
The morphological characteristics of fragility fractures of the pelvis change over time (Fig. 1). The natural history of these lesions is one of insidious but continuous progress. The history often starts with a simple pubic ramus fracture. Patients are mobilized early, and full weight-bearing is allowed. Because of recurrent falls or repetitive smaller traumas, additional bone structures are damaged, leading to more complex fracture patterns and greater instability23. Complete collapse of the pelvic ring represents the end of this evolving process.
The primary reason for presentation to an emergency department is pain in the pelvic region. Pain typically is related to a fall and has an acute and sharp character. In some cases, the fall is not memorable. Most patients are immobilized; a minority is able to sit or walk short distances. In some patients, pain is chronic and is related to previous events that have been underestimated, underdiagnosed, or undertreated. This pain has a deep and dull character. Pain is localized at the pubic symphysis, in the groin, and/or at the posterior aspect of the pelvis or the low back. Physicians may erroneously focus diagnostic examinations on the lumbar spine24. Tenderness is noted in the fractured region. Gross pelvic instability is not detectable. Hemodynamic instability is rarely noted12. The condition of the skin and soft tissues around the pelvis is not altered. The exclusion of local hematomas, infections, and decubitus ulcers, all of which may influence the treatment protocol, is recommended. The neurological and vascular status of the lower extremities is documented in all patients.
Patients with a clinical suspicion of fragility fractures of the pelvis receive an anteroposterior pelvic overview first. Inlet and outlet-view radiographs are made when a pelvic fracture is confirmed on the anteroposterior radiograph. The inlet-view radiograph shows the amount of internal rotation of the innominate bone. The integrity of the anterior sacral cortex and of the inner curve of the innominate bone is best analyzed on this view. The outlet-view radiograph provides information on the shape and symmetry of the sacrum, neural foramina, and sacroiliac joints. We recommend the use of these 3 projections as a reference for later comparison.
However, crush zones and nondisplaced fractures, especially in the sacrum, may not be recognized on radiographs. Missed fractures may lead to underestimation of the severity of the fragility fracture pattern, resulting in inadequate treatment and rehabilitation25. We therefore recommend always performing a pelvic computed tomography (CT) scan when there is a high index of suspicion for a pelvic fracture on conventional radiographs or when a fracture has been confirmed. Axial, coronal, and sagittal scans should all be analyzed to gather information about the fracture configuration in the posterior part of the pelvis. For example, the horizontal component of an H-type sacral fracture is rarely visible on conventional radiographs and is only identified on sagittal CT scans.
Radiographic signs of chronic instability include callus formation at the edges of the fracture margins and areas of bone loss due to persistent movement between fracture fragments. Bone destruction near a joint leads to joint instability.
Magnetic resonance imaging (MRI) of the pelvic ring is the most sensitive examination for the detection of occult fractures. Bone bruises within the sacrum can be detected before fissures and fractures become visible on other diagnostic examinations. MRI is not part of the classic diagnostic workup of fragility fractures of the pelvis. MRI is used if conventional radiographs and CT scans do not reveal findings that may explain the complaints of the patient, especially low-back and pelvic pain. Differentiation between bone marrow edema and malignant lesions is also possible with MRI26.
Fragility fractures of the pelvis are, in many ways, different from pelvic ring fractures in younger adults. The trauma mechanism, hemodynamic condition, clinical signs and symptoms, bone density, fracture morphology, and natural course are specific and not comparable. These differences were reasons enough for us to propose a new classification system that includes all typical fracture patterns, differentiates between different degrees of instability, and is connected with recommendations for treatment (Fig. 2)10. This classification system is based on analysis of conventional radiographs and CT scans.
The first criterion for differentiation among fracture types is the degree of instability. This criterion is the most important consideration when determining the type of treatment and the type and extent of surgery, if needed. Fracture displacement is considered to be the leading sign of instability. Nondisplaced lesions are characterized by a crush or fracture without deformation of anatomical landmarks, whereas displaced lesions are characterized by a crush or fracture with anatomical deformation. The second criterion, which leads to different subcategories, is the localization of the instability in the posterior part of the pelvic ring. The various categories and subcategories of fragility fractures of the pelvis are described in the following paragraphs.
Type I: Type-I lesions are isolated anterior pelvic ring fractures, with no involvement of the posterior part of the pelvis. Type-IA lesions are unilateral, whereas Type-IB lesions are bilateral (Fig. 2). In our case series of 245 patients with fragility fractures of the pelvis, Type-I lesions accounted for only 17.5% of the fractures27. Hence, >80% of the patients in that series had an additional posterior pelvic ring injury. These data support the need for CT evaluation of all low-energy pelvic fractures as posterior pelvic ring abnormalities are often missed on conventional radiographs25.
Type II: Type-II lesions are nondisplaced posterior lesions. Type-IIA lesions are nondisplaced and isolated posterior lesions, Type-IIB lesions are sacral crush injuries with anterior disruption, and Type-IIC lesions are nondisplaced sacral, sacroiliac, or iliac fractures with anterior disruption (Fig. 2). Type-II lesions accounted for >50% of the fractures in our case series10,27.
Type III: Type-III lesions are displaced but unilateral posterior injuries combined with an anterior pelvic ring lesion. Type-IIIA lesions involve a displaced unilateral ilium fracture, Type-IIIB lesions involve a displaced unilateral sacroiliac fracture-dislocation, and Type-IIIC lesions involve a displaced unilateral sacral fracture (Fig. 2). Type-III lesions accounted for only 11% of the fractures in our case series10,27.
Type IV: Type-IV lesions are displaced bilateral posterior injuries. Type-IVA lesions are bilateral iliac fractures or sacroiliac disruptions. Type-IVB lesions are spinopelvic dissociations associated with bilateral vertical fractures through the sacral ala with a horizontal component connecting them (a U- or H-type sacral fracture). Type-IVC lesions are a combination of different posterior instabilities (Fig. 2). Type-IV lesions accounted for 19.2% of the fractures in our case series10,27.
The treatment of fragility fractures of the pelvis goes far beyond the decision between nonoperative and operative treatment and involves a multidisciplinary team approach with the input of orthopaedic surgeons, geriatricians, specialists in bone metabolism and pain therapy, and physiotherapists. It is evident that the general condition of the patient should be optimized in the shortest possible time. It is also indispensable to diagnose and address underlying bone disease according to established guidelines28. Continuous monitoring of the patient during and after the hospital stay is mandatory. The different parts of treatment (pain therapy, correction of metabolic disorders, physiotherapy) and their effect on the patient’s condition must be discussed by the team. Treatment modalities must be adapted to the level of activities of the patient before the traumatic event as well as to his or her functional progress.
Fragility fractures of the pelvis lead to intense and immobilizing pain. Long-term immobilization leads to secondary complications. Van Dijk et al. reported a rate of serious complications of 20.2% in a case-controlled study of 99 patients29. The most frequent complications were urinary-tract infections, pneumonia, and side effects associated with nonsteroidal anti-inflammatory drugs. It follows that the primary goals of treatment must be to minimize pain and to restore mobility in the least invasive manner. Therefore, it is of utmost importance to thoroughly analyze the characteristics of each lesion. The classification system provides a framework for identifying the “personality” of each fracture10.
Nonoperative management, consisting of pain treatment and careful physiotherapy, has first priority. Pain medication is administered as needed. Physiotherapy begins with the patient in bed. The patient is mobilized out of bed as soon as possible. Nonoperative treatment is considered to have failed if the patient reports unbearable pain during mobilization. Follow-up radiographs are needed to rule out secondary fracture displacement, which would necessitate a change in the treatment strategy.
If operative treatment is needed, minimally invasive procedures are preferred to open reduction and internal fixation. Anatomical reduction is less important than is the restoration of stability. In the following paragraphs, we describe various treatment concepts according to the different degrees of instability represented by the main categories of our classification system.
Type-I injuries should be treated nonoperatively as described above. To prevent complications, the progression of mobilization must be guided by the patient’s complaints and should not be forced by the therapist. Evolution should be monitored and discussed, and changes should be implemented as needed. Therapy that is too aggressive can lead to progression of instability as a result of secondary fractures or increased fracture displacement.
Type-II lesions also can be treated nonoperatively, but rehabilitation will take longer and will be more cumbersome because of the involvement of the posterior part of the pelvic ring. When nonoperative treatment does not relieve symptoms, operative treatment must be discussed with the patient. Percutaneous procedures for fixation are then recommended.
Type-III lesions rarely heal spontaneously; thus, operative treatment is the rule. Percutaneous stabilization is preferred in cases of limited displacement. In cases of gross displacement, open reduction and internal fixation is inevitable.
Type-IV lesions must be treated with surgical fixation in order to restore stability and to prevent further intrusion of the lumbosacral segment into the pelvic ring. Stabilization is needed on both sides.
Special attention must be paid to any instability in the anterior aspect of the pelvis. In the case of such instability, we recommend that both the anterior and posterior parts of the pelvic ring should be surgically stabilized. Stabilizing the posterior but not the anterior part of the pelvic ring may be associated with a higher risk of implant loosening or secondary displacement. Percutaneous procedures are preferred for the treatment of the anterior part of the pelvis.
Before surgery, bowel contents should be cleared for optimal intraoperative visibility of all osseous landmarks. This recommendation is particularly important in situations involving minimally invasive surgical procedures.
Multiple techniques for the reduction and fixation of posterior and anterior pelvic ring instabilities following high-energy pelvic trauma have been developed. Percutaneous and less-invasive techniques play a more important role than open procedures in the elderly patient population30.
Posterior Stabilization Procedures
Iliosacral Screw Osteosynthesis
Iliosacral screw osteosynthesis is widely accepted for the fixation of sacral fractures and sacroiliac dislocations in patients with high-energy pelvic injuries31. This procedure is also of high value for the treatment of fragility fractures of the pelvis because a majority of cases include a sacral ala fracture. The procedure can be performed with the patient in the supine or prone position. Access to the posterior part of the ilium is easier with the patient in the prone position. Screw fixation with the patient in the supine position is only recommended when the patient is thin and the sacral fracture is not displaced or is only minimally displaced32. The stability of sacroiliac fixation has been shown to be significantly higher when the procedure is performed with 2 screws as compared with 1 screw (p = 0.015 and p = 0.018 for screws inserted in S1-S1 and S1-S2 configurations, respectively)33. The screws are placed perpendicular to the fracture plane, and 7 or 8-mm cannulated screws with a long thread are used34. Screws should cross the midline and should pass through the sacral body, where the highest bone density is found. (Fig. 3)15. The use of washers is recommended in order to avoid perforation of the screw head through the lateral cortex of the posterior part of the ilium. Tightening of the screw creates compression in the fracture plane. A second screw also can be placed in the body of S2. However, the corridor in S2 is smaller than that in S114, which enhances the risk of malpositioning or perforation. The individual anatomy of the sacrum must be respected in order to minimize the risk of malpositioning35,36.
The holding power of iliosacral screws in fragility fractures of the pelvis is lower than in pelvic lesions in adults. Implant-augmentation techniques have been developed to increase the pullout force of these screws. Novel cannulated iliosacral screws have several perforations near the tip. Once the screws are put in place, liquid cement is applied under light pressure into the cancellous bone around the tip. The hardened cement creates a stable construct with the screw. The pullout force of augmented screws is considerably increased in bone with low bone mineral density37,38. Cement must be applied very carefully to avoid leakage into the fracture site, sacral canal, or neural foramina. Data from the first clinical studies are promising, yet further analysis is needed before iliosacral screw osteosynthesis with cement augmentation can be recommended as a standard procedure39,40.
Sacroplasty is analogous to vertebroplasty and kyphoplasty41. Cement is injected into the sacral fracture according to one of the various insertion techniques that have been described42,43. Following the procedure, the intensity of pain is reduced and mobilization can be started quickly44,45. The cement leakage rate has differed remarkably among reported series: Kortman et al. described only 1 case of cement leakage in association with 243 procedures (for a rate of 0.4%)46, whereas Bastian et al. reported a rate of cement leakage of 38% in association with 33 procedures47. The indications for sacroplasty as described by Kortman et al. were based on MRI findings, whereas those described by Bastian et al. were based on CT images. The different incidence of leakage suggests that different pathologies were treated. Sacral fractures with a cortical gap may be a contraindication for sacroplasty because of the risk of symptomatic cement leakage. There is little evidence in the literature regarding when a fragility fracture of the sacrum should be treated with sacroplasty or osteosynthesis. Recently, a combination of sacroplasty with cement-augmented iliosacral screw osteosynthesis was proposed48.
Transsacral Bar Osteosynthesis
Transsacral bar osteosynthesis is performed by inserting a 6-mm threaded bar through the sacral corridor of S1; the insertion is performed through small skin incisions49. Washers and nuts are placed over the bar on both sides. Tightening of the nuts creates interfragmentary compression. The osteosynthesis is adequate for the stabilization of bilateral nondisplaced or minimally displaced fractures of the sacral ala or sacroiliac joint (Fig. 4). The stability of transsacral bar osteosynthesis does not depend on the strength of the sacral cancellous bone (as is the case after iliosacral screw osteosynthesis) but rather on the strength of the external cortex of the posterior iliac wing against which the nuts and washers are tightened. Outcome data for this technique are sparse yet positive49,50.
Posterior Bridging Plate Osteosynthesis
For posterior bridging plate osteosynthesis, a long plate is inserted posterior to the sacrum and is contoured around the posterior iliac crests to fit against the posterior part of the ilium51. Only 2 small incisions at the posterior iliac crests are needed, and the soft tissues behind the sacrum are tunneled for plate positioning. The plate functions as a tension band, but it does not create direct compression on the fracture site. Specific angular stable plate designs have been developed and have been associated with greater stability52.
Transiliac Internal Fixation
For transiliac internal fixation, 2 pedicle screws with a diameter of up to 9 mm and a length of up to 120 mm are inserted from the posterior superior iliac spine toward the anterior inferior iliac spine and are connected with a transverse rod (Fig. 5). Stability following this procedure is comparable with that following anterior plate fixation of the sacroiliac joint and iliosacral screw osteosynthesis for the treatment of pure sacroiliac dislocation53. The usefulness of this procedure for the stabilization of high-energy posterior pelvic traumatic injuries is high, but published data on the use of this procedure for the treatment of fragility fractures of the pelvis are not yet available54.
Lumbopelvic fixation is performed by connecting the lumbar spine to the posterior part of the ilium, bypassing the fractured sacrum. One pedicle screw is placed in L4 and/or L5 at the side of instability, and a second pedicle screw is inserted in the posterior part of the ilium; a rod connects the pedicle screws. The procedure can be performed percutaneously and bilaterally with a transverse connection between both rods. This procedure has been used for the treatment of sacral H-type fractures55. As this technique implies fixation of the lumbopelvic junction, it should only be used for the treatment of displaced and vertically unstable lesions (Fig. 6). Little information is available about the outcome of lumbopelvic fixation when used for the treatment of fragility fractures of the pelvis56.
Angular Stable Plate Fixation of the Innominate Bone
Angular stable plate fixation of the innominate bone is recommended for the treatment of fractures of the ilium. Through the first window of the ilioinguinal approach, a preshaped large-fragment angular stable plate is placed over the reduced fracture. The proximal screws are directed parallel to the iliosacral joint. The distal screws are directed distally and laterally, taking the longest trajectory in the ilium bone above the acetabular cavity. At the iliac crest, the fracture is stabilized with additional long lag screws (Fig. 7). Locked plates and screws have a higher pullout force and prevent secondary loosening in osteoporotic pelvic bone57.
The same complications associated with the above-mentioned techniques are noticed when they are used for the treatment of high-energy pelvic ring fractures or fragility fractures of the pelvis. In elderly persons, surgery is more challenging for several reasons. Intraoperative orientation may be difficult because of reduced visibility of bone structures as a result of decreased bone density. There is a higher risk of implant loosening as a result of poor bone stock. The soft-tissue envelope of elderly persons is at higher risk of wound-healing disturbances. We are not aware of any data comparing the rates of complications after pelvic fracture surgery in younger adults and the elderly. To minimize the risk of complications, we recommend that surgery should be performed by an experienced pelvic surgeon.
Anterior Stabilization Procedures
Posterior lesions are nearly always combined with anterior lesions. When posterior pelvic instability is treated surgically, fixation of the anterior part of the pelvis should also be taken into consideration.
External fixation is widely used to stabilize high-energy pelvic disruptions58. Gänsslen et al. recommend supra-acetabular external fixation for the treatment of lateral compression injuries in geriatric patients59. We do not recommend external fixation for the stabilization of anterior pelvic ring instability associated with fragility fractures of the pelvis. Pin-track infections and pin loosening are frequent complications. The incidence of complications dramatically increases with the duration of treatment60.
Retrograde Transpubic Screw: The optimal indications for retrograde transpubic screw fixation include a superior pubic ramus fracture or fracture at the anterior lip of the acetabulum. The screw is inserted percutaneously in cases of minimally displaced fractures. Care should be taken to avoid penetration of the acetabulum. The screw passes the acetabular cavity medially and cranially (Figs. 3, 4, and 5). The screw splints the pubic ramus fracture; it does not create compression30,61.
Plate Fixation: Plate fixation can be performed through an infra-umbilical midline incision or a Pfannenstiel incision. Small-fragment curved plates are used, allowing variable screw directions. Stability is greater after plate fixation than after retrograde transpubic screw fixation62. It is recommended that the longest-possible screw trajectories should be used in order to obtain good purchase. Non-angular stable plates are preferable63. The infra-acetabular corridor medial to the acetabulum should be used whenever possible. The corridor can be >100 mm in length; the screw has very good holding power in the strong ischium (Fig. 8)64,65.
Internal Fixator: The concept of the anterior internal fixator is similar to that of posterior transiliac internal fixation. A curved rod is placed subcutaneously over the entire anterior part of the pelvis. Long pedicle screws are inserted from the anterior inferior iliac spines toward the posterior superior iliac spines. The rod is inserted through a subcutaneous tunnel and is connected to both screw heads66. Irreversible damage to the lateral femoral cutaneous nerve and the femoral nerve has been reported67,68.
Fragility fractures of the pelvis are receiving more attention because of their increasing incidence and their possibly complicated course. Fragility fractures of the pelvis have a specific “personality” that differs from that of pelvic ring lesions in younger adults. A comprehensive classification system distinguishes different degrees of instability and different morphological characteristics. Nonoperative treatment is adequate in the majority of cases. Operative fixation is recommended in cases in which nonoperative treatment does not relieve symptoms and in cases involving displaced fractures. Less-invasive osteosynthesis techniques are preferred over open reduction and internal fixation of the anterior and posterior parts of the pelvis. Rehabilitation is adapted to the general condition of the patient and to the level of pelvic stability after surgery. Few outcome data are currently available. More clinical and biomechanical research is needed to shed light on the optimal treatment of these lesions27,69.
Investigation performed at the Department of Orthopaedics and Traumatology, University Medical Center, Johannes Gutenberg-University, Mainz, Germany
Disclosure: The authors indicated that no external funding was received for any aspect of this work. The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article.
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