36 Radiographic manifestations of pubic symphysis osteomyelitis in the prostate cancer survivor: Definitive diagnosis lies in findings on magnetic resonance imaging

Abstract

INTRODUCTION AND OBJECTIVES: Pubic symphysis osteomyelitis (PSO) represents a debilitating complication of radiation and ablative treatments for prostate cancer. The definitive radiographic diagnosis of this is not described. In this review, we characterize the plain film radiographic and magnetic resonance imaging (MRI) findings of PSO in prostate cancer survivors treated at a tertiary referral center providing multidisciplinary treatment for PSO. METHODS: We conducted a retrospective review of an IRB approved database of prostate cancer survivors diagnosed with PSO from 2011 to 2015. Demographic and radiographic data were collected and analyzed. All patients suspected of having PSO underwent a plain film radiograph of the pelvis and a pelvic MRI with T1-weighted and fatsuppressed T2-weighted fast spin echo sequences. Intravenous gadolinium was utilized as determined by the clinical scenario. RESULTS: 17 patients were identified with PSO. All patients underwent plain radiographs of the pelvis at our institution. 16 had MRIs performed and interpreted at our institution and one MRI at another facility. The median age of these patients was 71 (range 64-84). All patients demonstrated increased signal on T2-weighted sequences and decreased signal on T1-weighted sequences along the pubic symphysis and the marrow of the involved pubic rami. High T2 signal at the origin of the obturator and adductor muscle groups (69%) along with diastasis of the pubic symphysis with cortical bone erosion (63%) were identified in the majority of patients. A fluid collection was identified in 75% of patients with the periprostatic space (n1⁄44), parasymphyseal region (n1⁄44), and left rectus muscle (n1⁄42) being the most common locations. 65% of plain films demonstrated no radiographic evidence of PSO CONCLUSIONS: MRI of pubic symphysis osteomyelitis in the prostate cancer survivor is characterized by high signal on T2 weighted images and low signal on T1-weighted images of the pubic symphysis and the bone marrow of involved pubic rami, with the majority of patients demonstrating regional myositis. Cortical erosion and fluid collections were also common findings in our cohort. The constellation of these findings combined with one’s clinical assessment should prompt consideration for PSO and will facilitate appropriate management. Plan radiography of the pelvis will miss the majority of radiographic findings critical to establishing a diagnosis. We consider MRI to be the definitive diagnostic modality for this clinical entity.