Significance of clinical examination, CT and MRI scan in the diagnosis of posterior pelvic ring fractures

Abstract

Introduction

Patients with a fracture in the anterior pelvic ring often simultaneously demonstrate pain in the posterior pelvic ring. The aim of the present prospective study was to assess the sensitivity of CT, MRI and clinical examination in the detection of fractures in the posterior pelvic ring in patients with fractures of the anterior pelvic ring diagnosed in conventional radiographs.

Methods

Sixty patients with radiographic signs of an anterior pelvic ring injury were included in this prospective analysis. Following a focused clinical examination of the posterior pelvis, all patients underwent both a CT and then a MRI scan of their pelvis. Two board certified radiologists evaluated the CT and MRI scans independently. To estimate the presence of osteoporosis the Hounsfield units of the vertebral body of L5 were measured in each case.

Results

Fifty-three women and seven men, with a mean age of 74.7 +/− 15.6 years were included into the study. A fracture of the posterior pelvic ring was found in fourty-eight patients (80%) patients using MRI. Fractures of the posterior pelvic ring would have been missed in eight cases (17%), if only CT had been used. Eighty-five percent of the patients with a posterior fracture had an osteoporosis. The majority of the cases suffered from a low energy trauma. Thirty-eight patients (83%) with positive clinical signs at the posterior pelvic ring actually had a fracture of the posterior pelvic ring in the MRI. The clinical examination proved to be equally effective to CT in detecting posterior pelvic ring fractures.

Conclusion

The significance of both, clinical examination and CT was confirmed in the detection of fractures in the posterior pelvic ring. MRI examination of the pelvis however, was found to be superior in detecting undislocated fractures in a cohort of patients with a high incidence of osteoporosis. Using MRI may be beneficial in select cases, especially when reduced bone density is suspected.

Introduction

Due to the ageing of society and the mounting incidence of osteoporosis, there is an increase of pelvic fractures to be noticed following low-energy trauma [1], [2]. Fractures of the anterior part of the pelvis for example lesions of the pubic rami count among the most common fractures in trauma patients. These anterior injuries are often associated with additional lesions of the posterior pelvic ring [2], [3]. Mortality is high. Hill reported only 45.6% of the patients to be alive after a five-year period after the occurrence of a pubic rami fracture [4].

Radiologic diagnostic measures for pelvic ring fractures are still under discussion. By using CT-scans Rommens et al. found posterior lesions in 32% of patients with pelvic injuries that were initially missed in standard X-ray [5]. Insufficiency fractures in particular tend to be underdiagnosed by standard pelvic ap X-ray, mainly due to a missing fracture dislocation [6], [7], [8] (Fig. 1).

The present gold standard for the detection technique in acute pelvic fractures with involvement of the posterior pelvic ring is the Multidetector Computed Tomography (MDCT) [8], [9]. Recent investigations favour MRI-scan to the CT for pelvic ring fractures, particularly when it comes to occult fractures [1], [10], [11], [12], [13], [14]. Osteoporotic patients often indicate pain in the posterior pelvic ring after low energy trauma without fracture signs in the CT-scan [12]. In diagnosing occult sacral fractures the MRI seems to be superior to the CT scan [15].

The aim of the present prospective study was to assess the sensitivity of CT, MRI and clinical examination in the detection of fractures in the posterior pelvic ring in patients with fractures of the anterior pelvic ring diagnosed in conventional radiographs.