Septic arthritis of the pubic symphysis,a rare cause of peripartum pelvic pain: A case report

Introduction

Septic arthritis of the pubic symphysis is a rare and potentially life-threatening infectious condition, particularly in the peripartum period.^1–3 Its presentation can mimic more common obstetric or musculoskeletal conditions, leading to diagnostic delays. Although documented in athletes and postoperative patients,^4,5 peripartum onset remains uncommon and underrecognized. Early diagnosis and prompt treatment are essential to prevent complications such as functional limitation or systemic infection. This report contributes to the limited literature by presenting a case of pubic symphysis septic arthritis occurring peripartum in the absence of immediate provoking factors, with complications including endocarditis, and highlighting a subsequent uncomplicated pregnancy.

Case

A 32-year-old woman in her first pregnancy presented at 41 weeks and 2 days of gestation for induction of labour due to postdates, using dinoprostone. Her pregnancy had been complicated by a mountain bike accident at 23 weeks with laceration to the left elbow requiring sutures, and a motor vehicle accident at 24 weeks with minor injuries to the left rib, right low back, and hip. She was a lifelong non-smoker and non-drinker, and was physically active throughout the pregnancy.

Following the insertion of dinoprostone, she complained of a new onset of sharp pain in the right buttocks, which then settled. Four hours later, she was woken from sleep by severe, sharp pain to her groin and inner thighs exacerbated by movement and weight-bearing. She returned to the hospital and subsequently developed a fever of 38.1°C; other observations were normal. Physical examination revealed severe tenderness to the lower back, hips, and suprapubic region and decreased range of motion of both hips, worse with hip flexion and abduction/adduction. Neurologic examination did not reveal focal deficits, although power assessment was limited due to severe pain. No surrounding edema, erythema, or skin changes were noted. On vaginal examination, there was severe tenderness of the pubic symphysis. Fetal heart rate was 165 beats per minute and cardiotocography showed a few uncomplicated variable decelerations.

Bloods revealed a normal white blood cell count (11.5 × 10⁹/L) and elevated C-reactive protein (158.3 mg/L). Other blood tests were normal. Blood and urine cultures were taken.

The initial working diagnosis was chorioamnionitis. The cause of the pelvic pain was unclear; the differential diagnosis included severe symphysis pubis dysfunction. Ampicillin and gentamicin were initiated, alongside intravenous fluids and analgesia. Multidisciplinary discussion, including obstetrics, obstetric internal medicine, and anesthesia, was undertaken, with concerns about epidural insertion due to fever and inability to rule out neurologic involvement. To keep labour progressing, oxytocin was started, and rupture of membranes was performed. Amniotic fluid was clear. Remifentanil patient-controlled analgesic (PCA) was initiated. Despite this treatment, she had minimal ability to move her legs, and there were concerns about her ability to have an active second stage of labour. An emergency caesarean delivery was performed under general anaesthetic, and a healthy baby boy was born weighing 3975 g.

Postoperatively, the severe pelvic pain remained unchanged. Hydromorphone PCA was initiated. The plain radiograph of the pelvis and lumbar spine was normal. Lumbar spine computed tomography (CT) revealed irregularity of the articular surfaces of the pubic symphysis without any bony destruction or joint effusion (Figure 1). Blood cultures were positive with Gram-positive cocci suggestive of Staphylococcus aureus (S. aureus).

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Figure 1.

Computed tomography (CT) scan showing mild irregularity of the articular surfaces of the pubic symphysis.

The patient was started on intravenous cefazolin 2 g every 8 h for treatment of methicillin-sensitive S. aureus (MSSA) bacteraemia and suspected septic arthritis of the pubic symphysis. A pelvic magnetic resonance imaging (MRI) confirmed the diagnosis, revealing an abnormal pubic symphysis. The articular surfaces of the joint were irregular, consistent with erosive changes, with no cortical destruction. The subchondral bone on either side of the joint was abnormal, displaying high signal on short tau inversion recovery (STIR), low signal on T1, and enhancement (Figure 2). These changes extended laterally from the articular surface by 1 cm on the right and 0.9 cm on the left. There was no other focal bony abnormality. A joint aspiration was not felt indicated, given blood cultures had identified the causative organism, and there was no evidence of abscess formation on imaging.

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Figure 2.

Magnetic resonance imaging (MRI) showing abnormal fluid signal within the pubic symphysis joint space, with irregular articular surfaces of the joint consistent with erosive change.

She was transferred to a high-acuity unit for close monitoring. Initial transthoracic echocardiogram (TTE) showed no valvular vegetation. After 48 h of cefazolin, the patient was afebrile but still required regular opioid analgesia. Repeat blood cultures were negative. A peripherally inserted central catheter line was placed for ease of continuation of intravenous antibiotics.

The patient was discharged home after one week to complete a 6-week course of IV cefazolin. She had a bed rail and raised toilet seat installed prior to discharge and left the hospital using a four-wheel walker. A transesophageal echocardiogram was considered but felt unlikely to alter medical management, so it was not performed. By 5 weeks postnatally, the patient weaned off all opioids but was experiencing some withdrawal symptoms. A repeat TTE 3 months after the initial bacteraemia showed a 2 mm × 2 mm vegetation on the aortic valve not seen on the initial echocardiogram. A 2-year post-infection TTE showed the vegetation remains unchanged. The patient had a second pregnancy and delivered by planned caesarean 3.5 years post-infection. She described mild to moderate recurrent pubic symphysis pain, particularly with hip flexion and abduction, that required modification of normal activities. She attended regular pelvic health physiotherapy throughout pregnancy and postpartum.

Discussion

Here described is a rare case of MSSA septic arthritis of the pubic symphysis presenting acutely peripartum and complicated by endocarditis. Septic arthritis of the pubic symphysis is an extremely rare condition, accounting for approximately 0.8% to 1.36% of all infectious arthritis in adults. ¹ The main risk factors include prior female urological and gynaecological surgeries, intense physical activity, pelvic malignancy, and trauma.^1–4 Pelvic girdle pain, typically of musculoskeletal origin, is common and can be experienced at the pubic symphysis, usually subsiding after birth. ⁶ Osteitis pubis is a sterile inflammatory process frequently associated with the gradual onset of pelvic pain, which is generally described as mild to moderate. In contrast, septic arthritis of the pubic symphysis is rare but life-threatening, characterized by severe, debilitating pain and accompanied by fever. Prompt diagnosis and treatment are required to prevent serious complications.^1,3,4,7 The most common causative organisms are S. aureus and Pseudomonas aeruginosa. ¹

Outside of the pregnant population, septic arthritis commonly affects athletes, with the possibility of osteitis pubis predisposing to septic arthritis if transient bacteremia occurs. In the pregnant population, it is most commonly secondary to peripartum trauma, which can predispose to infection. In this case, etiology was unclear as the patient presented acutely with no preceding pelvic pain or trauma. She was, however, physically active at a high level throughout pregnancy, which may have been a contributing factor. She also sustained minor trauma from a motor vehicle accident at 24 weeks and experienced a second-trimester laceration that may have been an entry point for bacteria.

Imaging is important for the accurate diagnosis of pubic pain. While CT scans are commonly used, false negatives can occur in up to 10% of cases, so septic arthritis should still be considered if clinical suspicion remains high.^5,7,8 MRI has been shown to be highly sensitive for detecting septic arthritis in the general adult population; however, its specificity may be reduced in the postpartum setting due to physiological changes leading to abnormal bone marrow signal changes and diagnostic uncertainty in this population, which can complicate interpretation.^9,10 The treatment for both infective endocarditis and septic arthritis of the pubic symphysis typically ranges from 4 to 6 weeks of IV antibiotic therapy targeted to the organism isolated. ⁸ While some cases may require surgical intervention, most are managed successfully with targeted antibiotic therapy.^1,3

Following delivery, recovery is often viewed in the context of postpartum physiological changes, while little emphasis is placed on the functional status of the mother. While physiologic changes during pregnancy typically resolve within 6 weeks, a full return to functional capacity may take longer, especially if complications arose during childbirth. After childbirth, functional status is defined not only by physical state, but readiness to assume care of the family in social, psychological, and occupational settings. ¹¹ Upon discharge, it is important to consider the impact of intensive treatment such as IV therapy and the functional impairments that can result from pathology like that described here.

For the obstetric patient presenting with pelvic girdle pain, septic arthritis of the pubic symphysis must remain a key consideration in the differential diagnosis, especially when accompanied by fever and severe pain. It is a rare, life-threatening illness that can have serious complications if left untreated. Differentiating it from other causes of pelvic pain can be challenging, but early detection is crucial to ensure prompt treatment and prevent functional disability or death. Reassuringly, with multidisciplinary care and appropriate activity modification, subsequent pregnancies can be successful.