Pelvic Trauma

Mark R. Adams, MD

Mark C. Reilly, MD

Dr. Reilly or an immediate family member is a member of a speakers’ bureau or has made paid presentations on behalf of Stryker. Neither Dr. Adams nor any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this chapter.

ABSTRACT

Pelvic ring injuries and acetabular fractures can be challenging to treat, especially in elderly patients. Accurate assessment of any associated imaging studies is important to identify the severity of injury. Determination of the degree of instability of the pelvic ring or hip is required to determine the best course of treatment.

Keywords: acetabular fracture; acetabulum; pelvic ring injury; pelvis

Introduction

It is important to be aware of the recent trends in the literature as it pertains to pelvic ring injuries and acetabular fractures in adult patients. The general principles of care of these injuries are well established, and these recent trends represent the evolution in care of patients with these complex injuries.

Pelvic Ring Injuries

The typical goals for the care of an adult patient with a pelvic ring injury are for union in a well-aligned position while avoiding serious complications. Although the goals are constant from patient to patient, the spectrum of injury to the pelvic ring, as it relates to severity and instability, is wide ranging. Assessing the degree of mechanical instability and developing an individualized treatment plan based on that instability as well as other associated patient-related factors can be challenging.

The recent literature has documented issues with revision surgery of pelvic injuries due to failure of fixation, residual instability, and loss of alignment.¹^,²^,³^,⁴^,⁵ Failure of fixation is most commonly attributed to inferior reduction quality, inadequate fixation stability for the level of mechanical instability or a combination thereof, and the majority of the recent literature is dedicated toward improving understanding of these issues.

Surgical Indications

The typical indication for surgery for a pelvic ring injury is primarily based on the amount of mechanical instability thought to be present. Although the available classifications do not specifically direct treatment, they can help the surgeon better understand instability of the pelvic ring. An unstable pelvic ring is unlikely to heal in an acceptable position and is therefore indicated for reduction and fixation, whereas a stable pelvic ring injury may be managed nonsurgically.

Determining the correct procedure for each patient who requires pelvic ring surgery may be challenging. Injuries to the same anatomic structures but with differing degrees of instability may require different techniques to obtain and maintain a reduction. However, as radiographs and CT scans are static tests, the true degree of instability can often be difficult to determine. Recent articles have highlighted situations in which the preoperative workup and treatment can result in the surgeon underestimating the degree of instability present. The presence of a pelvic binder, a common emergency department resuscitative tool, has been noted to decrease clinicians’ ability to properly diagnose pelvic ring injuries.⁶ Furthermore, a recent case series of 72 patients with symphyseal injuries evaluated without binders noted that the circumferential wrap of the CT scanner consistently reduced the diastasis at the symphysis. In both of these studies, an AP radiograph of the pelvis prior to binder placement was more predictive of the degree of instability present.⁶^,⁷

In a 2011 study, a fluoroscopic examination of the pelvis under anesthesia consistently demonstrated a greater magnitude of instability than the initial radiographs revealed.⁸ The examination of the pelvis under
anesthesia is a powerful test because of its dynamic nature, and it was considered the benchmark for diagnosis of a pelvic ring injury in the pelvic binder study mentioned previously.⁶ This test has also been verified for its negative predictive value, as patients with a negative stress examination consistently obtain fracture union with appropriate alignment with closed treatment.⁹ The natural history of patients who have instability present only on stress examination is still unknown.

Reduction and Fixation

Posterior Pelvic Ring

A variety of reduction and fixation options exist for an unstable posterior pelvic ring injury, but irrespective of the treatment strategy, the surgical goal is obtaining and maintaining an accurate reduction and creating a stable fixation construct in a well-aligned pelvis. Reductions can be performed closed, percutaneously, or open.

Percutaneous reduction and fixation techniques for the posterior pelvic ring have increased in frequency over time. Between 2003 and 2015, the number of pelvic ring injuries treated by candidates sitting for Part II of the ABOS examination was constant from year to year. Percutaneous treatment of the posterior pelvic ring increased from 49% in 2003 to 79% in 2015, with a corresponding decrease in the percentage of open procedures.¹⁰ This trend toward more percutaneous fixation techniques has not necessarily been accompanied by a change in the reduction quality, however. A retrospective review of 113 patients at two trauma centers compared open reduction and internal fixation (ORIF) and closed reduction and percutaneous fixation of unstable pelvic ring injuries, and the reduction quality was considered slightly better in the closed reduction and percutaneous fixation group.¹¹

Recent literature has seen an increase in the number of publications related to the use of transiliac-transsacral screws, the accurate insertion of percutaneous posterior pelvic ring fixation, and novel methods of increasing stability of the posterior ring percutaneously.¹²^,¹³^,¹⁴^,¹⁵^,¹⁶ Transiliac-transsacral screws have been demonstrated to have a clear biomechanical advantage when compared with the use or shorter iliosacral screws.¹⁷ Furthermore, transiliac-transsacral screw fixation is capable of stabilizing bilateral injuries with a single implant.¹⁸

Execution of proper placement of transiliac-transsacral screws has been noted to be technically demanding. As a result, several articles have been recently dedicated to describing the anatomical variations in the pelvis, as well as the fluoroscopic imaging utilized for the procedure.¹²^,¹³^,¹⁸ Planning includes using the trauma CT scan of the pelvis and involves evaluation of the size and trajectory of the available osseous fixation pathways, measurements of planned screws for expected length, and assessment of the space available for multiple screw insertions.¹²

Iliosacral screws are most commonly inserted with conventional fluoroscopic guidance. Certain centers have fluoroscopically guided computer navigated surgery capability, and a comparative multicenter cohort study at two trauma centers in the Netherlands compared the two methods. Although there was no difference between the two groups in terms of their accuracy, the postoperative CT scan showed 17% of the screws placed to be inaccurate; 5 of the 80 patients underwent revision procedures as a result.¹⁹ This finding highlights the need for improved understanding of fluoroscopic images. A 2016 study noted that surgeons may perceive the position of iliosacral screws incorrectly with certain positions of misplaced screws. Surgeons consistently did not recognize the inaccuracy of iliosacral screws that penetrated the anterior border of S1, the superior sacral ala, and the S1 foramen when standard inlet and outlet views were obtained. They described variations on these views that improved the surgeons’ accuracy in identifying malpositioned screws.²⁰

In addition to malpositioned fixation, another potential complication is related to the proximity of the starting point for iliosacral screws to the superior gluteal artery. A CT arteriography study from 2017 measured 12.4 mm between the transsacral S1 screw and the superior gluteal neurovascular bundle.²¹

As a transiliac-transsacral screw used for a unilateral injury crosses the contralateral sacroiliac joint, concerns about the effect of the screw on that uninjured joint exist among surgeons. A recent retrospective comparative study of 62 patients treated with either unilateral iliosacral screws or transiliac-transsacral screws did not support those concerns, however. Majeed Pelvic Scores and side-specific Numeric Rating Scale pain scores demonstrated no difference between the two groups at 3-year follow up.¹⁴

Other strategies regarding posterior pelvic ring fixation have also been explored in the recent literature. Two recent studies have explored the possibility of using the third sacral segment as an osseous fixation pathway for a 7.0 mm diameter transiliac-transsacral screw. Interestingly, patients with dysmorphic sacra commonly had a pathway of sufficient diameter to accommodate a transiliac-transsacral screw in the third sacral segment. This corridor could potentially supplement the fixation performed at the higher sacral levels, when additional stability is desired¹⁵^,¹⁶ (Figure 1).

An alternate strategy that has recently been proposed focused on increasing the density of the bone in the osteoporotic patient being treated with an iliosacral
screw. A 2016 study described a technique of percutaneously injecting calcium phosphate into the sacrum, prior to the full insertion of the screw.²² Ideally, this would supplement the fixation of the screw in the sacrum as prior biomechanical study demonstrated a significant improvement in both stiffness and screw pull-out strength in a human cadaveric iliosacral screw model.²³

Figure 1 Outlet view of the pelvis reformatted from the postoperative CT scan. Transiliac-transsacral screws cross the second and third sacral segments.

Anterior Pelvic Ring

The anterior pelvic ring has comparatively received less attention in the recent literature than the posterior pelvic ring. Anterior ring injury typically involves fractures of the rami, disruption of the symphysis, or a combination thereof. There are open and percutaneous methods of treatment, similar to posterior ring; both methods have been studied in the past few years.

Open treatment of a pubic symphysis disruption commonly involves a direct clamp reduction of the symphysis dislocation, followed by plate stabilization. Two studies have questioned this typical process in the recent literature.⁵^,²⁴

The clamp is traditionally applied anteriorly, in close proximity to the pubic tubercles. Although sexual dysfunction after a pelvic ring injury is common, this has generally been attributed to the trauma, and not to the surgical treatment of the injury. However, the spermatic cord lies immediately adjacent to the pubic tubercles, and can easily be penetrated with a clamp applied in this location during the surgery.²⁴

It is well established that plate fixation can fail after ORIF of the symphysis pubis.²⁵^,²⁶^,²⁷^,²⁸ Although it is also established that failure of the plate does not necessarily correlate with a loss of alignment or a change in outcome, a 2015 study investigated whether symphyseal fusion at the time of ORIF would make a difference in terms of alignment and implant failure rate.²^,⁵^,²⁹ In this study, patients in the symphyseal fusion arm had lower rates of implant failure and revision surgery than patients in the standard ORIF group.⁵

Implant failure and malunion can also be affected by the addition of posterior fixation in patients with APC 2 pelvic ring injuries. When compared with patients treated with a symphyseal plate alone, those with combined anterior and posterior pelvic ring fixation had substantially lower rates of malunion and implant failure.⁴

Percutaneous treatment of the anterior pelvic ring generally comes in two forms: intramedullary screw fixation and external fixation. Modifications to the standard external fixator have been made to avoid issues with pin care and patient mobilization that occur because of the prominent pins; this is termed anterior subcutaneous internal pelvic fixator.³⁰^,³¹^,³²

Anterior subcutaneous internal pelvic fixator, when compared with plate fixation, is associated with an inferior reduction of the symphysis in those patients with a symphyseal injury. This implant is used with a planned second anesthetic for removal; plates typically do not require removal. In a retrospective review of 83 patients treated with this device, patients treated with this fixator appear to score well overall on validated functional outcome measures. However, issues with the lateral femoral cutaneous nerve and heterotopic ossification are frequent. The authors also highlight that there is a learning curve to the procedure.³¹^,³³

Perhaps this learning curve is responsible for some of the other complications associated with this device reported in the literature. Femoral nerve palsies were noted in eight femoral nerves in six patients treated with this device; resolution of the issue was noted to be variable after the removal of the fixator. A persistent femoral nerve palsy was noted to significantly affect patient function.³⁴

Spinopelvic Dissociation

Patients with a spinopelvic dissociation are a subset within patients with pelvis injuries, even though several types can involve the pelvic ring. Although these injuries have certain things in common with pelvic ring injuries, there are several issues that are particular to spinopelvic dissociation. Lumbopelvic instability is primarily a sagittal plane issue; flexion of the pelvis and lower sacral fragment on the body of the upper sacrum result in kyphosis of the sacrum and compromise of the cauda
equina within the sacral spinal canal. ORIF, classically done through a vertical midline approach, typically involves spinal instrumentation from the lumbar spine to the pelvis for patients with significant instability and may also include a neural decompression.³⁵^,³⁶

Because of these significant issues in patients with lumbopelvic instability, it behooves the provider to correctly assess patients for this injury. The axial and sagittal cross-sectional imaging from the patient’s CT scan can be used as a screening evaluation for this injury. A unilateral sacral fracture has a high negative predictive value for lumbopelvic instability. Conversely, bilateral sacral fractures noted on the axial CT images are highly predictive of finding a transverse fracture component on the sagittal images. In one study, no patients with unilateral sacral fractures had associated lumbopelvic instability, but 87% of bilateral sacral fractures were associated with lumbopelvic issues.³⁷

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