Pelvic fractures

JOHN KEATING

Introduction

Epidemiology

INTRODUCTION

Pelvic fractures in the elderly are most commonly low energy osteoporotic fractures or pelvic insufficiency fractures. Although these fractures are actually the most common traumatic pelvic injuries the literature on them is sparse in comparison to that devoted to the management of higher energy pelvic disruptions, which are relatively uncommon by comparison. It is worth noting that 73% of all pelvic fractures occur in older patients.¹ Osteoporosis is a reduction in the volume of normally mineralized bone and renders bone susceptible to fracture from low energy trauma. Insufficiency fractures of the pelvis are fractures which occur spontaneously without obvious trauma in response to normal physiological loads. Although higher energy major pelvic disruptions do occur, they are less common but obviously life-threatening injuries in the older patient. The majority of pelvic fractures encountered in the elderly are stable and amenable to non-operative treatment but they do incur a substantial demand on healthcare resources since they are often associated with a prolonged hospital stay and requirement for rehabilitation.²

EPIDEMIOLOGY

Low energy osteoporotic fractures are the most frequent pattern of pelvic injury encountered in elderly patients. It has been estimated that two-thirds of pelvic fractures in older patients are due to low energy trauma, most commonly a result of simple falls.^3,4 Pelvic fracture incidence does increase with age. The overall incidence of pelvic fractures has been estimated to be between 20 and 37/100,000 per year.^5,6 However this incidence increases to 92/100,000 per year in patients over 60 years of age⁷ and rises to 446/100,000 per year in patients over 85 years of age.⁸ More than 90% of pelvic fractures in patients over the age of 60 years can be considered osteoporotic.⁷ In addition to this, the actual incidence of pelvic fractures in the elderly is increasing. Clement and Court-Brown⁹ reported an increase from 7.9/100,000 to 13.1/100,000 over a 10-year period. Kannus et al.⁷ reported a threefold increase in osteoporotic pelvic fractures over the period 1970–1997 in Finland. The increase in actual numbers of fractures can be explained to some extent by the increasing number of elderly patients in the population, but there is also evidence that the age specific incidence of pelvic fractures is increasing in European epidemiological studies^9,10 although the explanation for this is not certain.

Pelvic fractures in the elderly are associated with an increase in the standardized mortality ratio at 1 year, even when they are isolated injuries. Higher energy pelvic fractures in the elderly can be a result of a motor vehicle accident but falls from a height or down stairs are a more frequent cause of unstable pelvic fracture patterns in patients over the age of 65 years.¹¹ Acetabular fractures are much less common and account for less than 20% of osteoporotic pelvic fractures.^3,4

ASSESSMENT

There is generally a history of a fall in the majority of patients but in those with cognitive impairment the history may be unreliable. High energy trauma does occur but is much less common than in younger patients.^4,12 Unstable fracture patterns in the elderly are more likely to occur as a consequence of higher energy falls than road traffic accidents.¹ The patients most commonly complain of anterior groin pain, often associated with posterior pelvic pain. Patients complaining of posterior pain may have a posterior fracture and these patients should be considered for further imaging by computed tomography (CT) or magnetic resonance imaging (MRI). In low energy trauma resulting in the most common pelvic injury, an isolated pubic ramus fracture, physical signs are limited. In the majority of cases there is no external rotation or shortening of the leg, as would commonly be found in hip fractures.

For the small number of patients involved in higher energy trauma who present with multiple trauma, an assessment according to Advanced Trauma Life Support (ATLS) guidelines is appropriate. High energy pelvic fractures are uncommon in older patients but are associated with higher mortality rates than in younger patients. It is recognized that even mechanically stable patterns (e.g. lateral compression injury) are associated with a risk of significant bleeding.^{13,14 and 15} Assessment of older patients can be difficult – the presence of a normal blood pressure may actually represent hypotension in a patient with pre-existing hypertension.¹⁶ Development of a physiological tachycardia in response to blood loss may be impaired in patients on β-blockers or other anti-arrhythmic agents.¹³ Patients on warfarin for atrial fibrillation or other indications are more susceptible to serious haemorrhage.

IMAGING

Plain radiography will identify most anterior fractures but posterior injuries are often missed on these radiographs. Lau and Leung¹⁷ reported a prevalence of 59% of posterior ring fractures in patients presenting with an apparently isolated pubic ramus fracture. Other authors have reported an even higher incidence. Scheyerer et al.¹⁸ described a case series of patients with a pubic ramus fracture and found that 96.8% of patients had a posterior ring injury on CT scan, although their series had a proportion of higher energy injuries with a younger mean age than would be typically associated with isolated ramus fractures. On MRI, the posterior pelvic ring is involved in over 90% of patients with pelvic injuries.¹⁹ However, in elderly patients after falls, even a completely normal plain radiograph does not rule out a fracture. Ohishi et al.¹⁰ reported on 113 elderly patients with negative pelvic radiographs after falls and recorded that over 90% had some bone or soft tissue abnormality and one-third had occult pelvic ring fractures on MRI scan. Occult fractures of the pelvic ring are therefore quite common and the absence of radiographic abnormality on the plain radiographs does not rule out a fracture.

Patients who present with hip fractures should be evaluated carefully for the presence of an associated pelvic fracture. The incidence of occult pelvic fractures among in-patients with suspected hip fractures has been reported with incidence varying from 11% to 51%.^{20,21,22,23,24,25,26,27 and 28} Apart from the anterior ring, the most common site of fracture is the sacrum.¹⁰

Although pelvic inlet and outlet views can be obtained, they are not commonly used in modern orthopaedic practice, particularly in elderly patients following low energy falls. The most common situation is either to find a pubic ramus fracture with a suspected posterior injury or a negative plain radiograph in a patient with pelvic pain after a fall. A CT scan will identify the majority of bony injuries either occult or in association with anterior ramus fractures (Figure 32.1). If this investigation is negative, then an MRI scan will usually pick up associated soft tissue injuries which may the source of pain. Clearly, not all elderly patients with stable low energy pubic ramus fractures require additional imaging. However a CT scan should be considered if the mechanism of injury was not a low energy fall. Other relative indications are suspicion of a significant posterior lesion or patients who have significant persistent pain.

Figure 32.1 CT scan of the sacrum showing bilateral osteoporotic sacral alar fractures.

CLASSIFICATION

Patients with high energy pelvic ring disruptions are commonly described using two radiological classification systems: the AO/OTA classification mainly devised by Tile^29,30 and the Young-Burgess classification developed in Baltimore.³¹ The Tile/OTA³² system is a morphological system based on pelvic ring stability and in particular the integrity of the posterior ligament complex. Injuries are divided into stable (type A), rotationally unstable (type B) and vertically unstable patterns. The rotationally unstable types are classified as open book patterns (B1), lateral compression (B2) or combinations of these two patterns (B3). Vertical shear patterns are either unilateral (C1), combined with contralateral rotational injury (C2) or bilateral vertical shear (C3). This is the most comprehensive classification system with the ability to describe most patterns of injury in detail with the use of subgroups under each main category.

The most common pattern of injury in the elderly is the isolated pubic ramus fracture. In this system this injury is considered a stable fracture of the ring and is termed an A2.2 injury. Considering the high incidence of occult posterior lesions which can be detected by CT or MRI scanning, there is an argument for classifying these fractures as lateral compression injuries (B2). However the posterior injury is generally a minor anterior sacral ala compression and this will not influence management. In a study of elderly patients with pelvic fractures using this classification,⁹ 85% were isolated pubic ramus fractures which are termed A2.2 injuries using this classification system (Figure 32.2). Of the remainder 8% were other type A patterns and therefore stable pelvic ring injuries and only 7% were type B or C mechanically unstable pelvic ring disruptions.

Figure 32.2 Anteroposterior (AP) view of the pelvis showing right-sided pubic ramus fractures, the most common pattern of pelvic fracture in elderly patients.

The Young–Burgess³¹ system was devised for use with high energy pelvic ring disruptions. It relates the mechanism of injury to the pattern of ring disruption, and the expected injuries. It is a simpler classification, dividing fracture patterns into anteroposterior compression (APC), lateral compression, vertical shear and combined mechanical injury (CMI). This system does not really pertain to low energy osteoporotic fractures. Its application is therefore really limited to the small percentage of older patients who sustain higher energy pelvic trauma, which will be less than 10% of cases. Although it does guide the treating surgeon to the expected injuries (e.g. the association of APC injuries with transfusion requirement and urethral/bladder injury), the associations are not particularly sensitive or specific. Both classification systems are widely used and reported in published studies but the levels of interobserver agreement for both systems are moderate to poor.^{33,34 and 35}

A key difference in the pattern of pelvic fracture in the older patients is the relative infrequency of ligamentous injury and the higher prevalence of lower energy trauma, which results in a very different spectrum of injury than that covered by the foregoing systems of classification. On this basis Rommens and Hofmann³⁶ recently proposed a new classification for fragility fractures of the pelvis (FFP; Table 32.1). This was based on an analysis of pelvic ring fractures in a population of 245 patients with a mean age of 80 years. Their classification divides these fractures into four groups with increasing instability. A summary of the classification is given in Table 32.1. Additional imaging by means of CT or MRI scanning is required for accurate use of this classification.

Table 32.1 Classification of fragility fractures of the pelvis

Types I and II where there was an isolated anterior injury or an associated undisplaced posterior injury were the most common and amenable to non-operative management. However they do suggest percutaneous fixation needs to be considered in some type 2 injuries. In type 3 and type 4 there are unilateral or bilateral displaced posterior injuries, respectively. They suggest these are much more unstable fractures and best treated by standard methods of internal fixation. One of the interesting observations in their study was that unlike younger adults, where transforamenal sacral fractures are very common, they are very rare in elderly patients where the fractures are almost always localized to the sacral ala (Figure 32.1). Use of this classification and the associated treatment recommendations will need to be supported by prospective clinical studies.

For the majority of patients plain radiographs of the pelvis will be sufficient to make the diagnosis and plan treatment, which is generally non-operative. Additional imaging by CT or MRI scanning is indicated in patients presenting with:

Haemodynamic instability
Mechanically unstable pelvic fracture patterns
Suspicion of posterior ring involvement
Persistent pelvic pain after 2 weeks

TREATMENT

Low energy pelvic fractures

PUBIC RAMUS FRACTURES

Although pubic ramus fractures can occur at any age, they are comparatively uncommon in younger patients. Hill et al.³⁷ reported an overall incidence of 6.9/100,000/year but this rose to 25.9/100,000/year in patients over the age of 60 years. The majority of these are due to falls on the side, resulting in lateral compression injuries. They are often associated with posterior ring injuries but in the majority these consist of a type I alar compression fracture, which is stable and does not require operative intervention. Isolated fractures of the pubic ramus, classified as a type A2.2 injury, account for 85% of pelvic fractures in the elderly (Figure 32.2). The most common pattern of injury is unilateral with fractures involving both the superior and inferior pubic ramus. Management is almost invariably non-operative with a short period of initial bed rest and analgesia with mobilization as soon as pain allows. Although as indicated there is a high incidence of occult posterior fractures, these are almost invariably stable and their presence does not alter management or the prognosis.¹⁷ For this reason routine imaging by means of CT or MRI scanning in all of these patients is not indicated.

Both non-union and displacement (Figure 32.3) can occur but are very rare complications of these fractures.^38,39 In order to facilitate rehabilitation it is important to achieve adequate analgesia. Failure to do so will hamper regaining mobility, increase the risk of complications and prolong the hospital stay. Patients with cognitive impairment may find it difficult to communicate analgesic needs and this should be taken into account in their management. Some care in choosing analgesic management is required – opioid medication can increase confusion and non-steroidal analgesics are best avoided due to renal and cardiovascular side-effects.

Figure 32.3 Anteroposterior (AP) view of the pelvis 2 years after injury showing pubic ramus non-union, an uncommon complication of low energy ramus fractures.

Some authors have recommended interventions in selected patients. Tosounidis et al.⁴⁰ reported the use of external fixation in patients with pubic ramus fractures with associated sacral fractures if pain persisted for longer than 2 weeks. Percutaneous fixation with retrograde medullary ramus screws and iliosacral screws is also an option. Winkelhagen et al.⁴¹ reported on a series of six patients with persistent pain following isolated pubic ramus fractures treated by medullary ramus screws. They noted significant improvement in pain which facilitated mobilization and discharge. The technique had the advantage of being minimally invasive, and biomechanically is equivalent to plating.⁴² Injection of methyl methacrylate cement into ramus fractures to relieve pain has also been reported.³⁸ These techniques have only been reported in small numbers of patients and are probably only applicable to a subset of patients with these fractures where there is a posterior lesion and pain control is a significant problem.

Lau and Leung¹⁷ reported on a series of patients with pubic ramus fractures and recommended internal fixation in type II lateral compression fractures where there was an associated posterior iliac wing crescent fracture. Other fracture patterns were treated non-operatively and healed. Other authors have reported relatively high rates of operative intervention. Scheyerer et al.¹⁸ reported on a series of patients with isolated ramus fractures on plain radiographs with a 96.8% incidence of posterior fractures on CT scans and a 30% operative rate. However the mean age of their patients was 56 years, the series included many lateral compression fractures and it can be assumed therefore that their findings would not apply to the elderly population who present with low energy ramus fractures after a simple fall.

Pharmacological measures may have a role to play in accelerating healing. Peichl et al.⁴³ reported on the use of parathyroid hormone (PTH 1-84) in patients with low energy pubic ramus pelvic fractures. In 21 patients who received PTH 1-84 injections, fractures healed at a mean time of 7.8 weeks compared to 12.6 weeks in a control group of 44 patients, which was significantly faster. The relief of pain as measured by visual analogue scores and function as measured by the timed up and go test were also significantly better in the treatment group. Although the data are encouraging, corroboration of the findings in other studies would be useful.

The main issue with most pubic ramus fractures is the burden imposed on the healthcare system. The duration of hospital stay has been reported to vary from 9 to 17 days.^2,9,37 Shorter lengths of stay are associated with younger age and independent mobility prior to fracture.

Once the patient has been discharged, routine follow-up of these fractures is not required – the majority are united 6–8 weeks after injury. Although most patients do recover and regain their previous level of mobility, the fracture is a hallmark of frailty. However in their study Hill et al.³⁷ reported a mean hospital stay of 9 days and 78% of patients were discharged to their original residence. The overall survival rates at 1 and 5 years were reported as 86.7% and 45.6%, respectively.³⁷ In another study⁴⁴ of pubic ramus fractures and sacral insufficiency fractures the mortality was 23% at 1 year and 47% at 3 years. Male gender appears to be associated with a much poorer survival. Clement and Court-Brown⁹ reported a 40% 1-year mortality in male patients, which was significantly higher than in female patients.

Iliac wing fractures

Isolated osteoporotic fractures of the iliac wing are relatively uncommon (Figure 32.4). The literature on their management is very limited and mainly relates to higher energy fractures in younger patients.^45,46 They tend to occur as a result of a direct traumatic blow to the iliac wing itself, which is an uncommon mechanism of injury in the older patient. When they do occur they are often relatively comminuted without extensive displacement and can usually be treated non-operatively in the expectation that the majority will unite uneventfully. Surgical fixation of these comminuted fractures would be technically challenging in any event. Occasionally a two part fracture may rotate or displace significantly and in these cases non-union is a risk. Plate fixation is the method of choice for these fractures.

Pelvic and sacral insufficiency fractures

Pelvic insufficiency fractures are a well-recognized but under-diagnosed clinical entity in older patients presenting with pelvic pain. Patients present with lower lumbar back and pelvic pain. There is a history of injury in two-thirds of patients.⁴⁷ Pain is exacerbated by physical activity. They often occur in the presence of other comorbidities particularly osteoporosis, rheumatoid arthritis and metabolic bone disorders including Paget’s disease, hyperparathyroidism and osteomalacia. Physical findings are limited – stress tests of the sacroiliac joints however do tend to provoke increased pain. This would include compression of the sacroiliac joints and the flexion abduction external rotation test (FABER test). Neurological impairment is rare but has been reported. Sacral insufficiency fractures often occur in association with pubic ramus fractures, and in one report 78% of cases had concomitant ramus fractures.⁴⁸

Figure 32.4 Two-dimensional CT reconstruction image of an isolated iliac blade fracture. These can be managed without surgery as long as there is good bony apposition, as in this case.

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