A thirty-eight-year-old woman, seventeen weeks postpartum, presented to the Emergency Department with right-sided hip pain, a progressive limp, and refusal to bear weight on the right lower extremity. Before visiting our Emergency Department, she had been diagnosed with radicular pain and had been prescribed analgesics, which proved ineffective. The pain initially had presented two weeks postpartum and had increased over the next four months. She denied fever, chills, and trauma. She had had an uneventful pregnancy and a vaginal delivery at full term. She was neither tested nor treated for group B streptococcus prior to delivery. She denied current tobacco, alcohol, and drug use but did have a history of cigarette smoking. Medical history and family history were unremarkable.
On physical examination, the patient walked a maximum of two paces with an antalgic gait. She had decreased range of motion of the right hip, which worsened with internal rotation and extension. She was afebrile. White blood-cell (WBC) count was 8.3/mm3 with no left shift. The erythrocyte sedimentation rate (ESR) was 69 mm/h, and the C-reactive protein (CRP) level was 24 mg/L. Testing for human immunodeficiency virus (HIV) was negative. Results from the initial blood and urine culture specimens were negative.
Radiographs of the right hip revealed joint space narrowing as well as erosions of the superior acetabulum and femoral head without substantial sclerosis. There was no fracture or periostitis (Fig. 1). A computed tomography (CT) scan of the right hip demonstrated reactive periosteal bone about the anterior margin of the acetabulum and adjacent to the superior ramus. Erosive changes across all articular surfaces of the right acetabulum were noted (Fig. 2). Magnetic resonance imaging (MRI) demonstrated substantial joint effusion, edema in the surrounding gluteal soft tissues and femoral head, and adenopathy in the inguinal and iliac lymph nodes (Figs. 3-A and 3-B).
The patient underwent incisional biopsy of the right hip. Because malignancy was included in the differential diagnosis, we performed an incisional biopsy rather than hip aspiration in order to obtain adequate tissue samples for pathology. Aspiration of the joint returned approximately 2 cc of blood-tinged fluid. A 1-cm lateral incision was made; two core biopsy samples of the femoral neck were taken. Antibiotics were not administered until the biopsy was found to be adequate. Gross evaluation and frozen section demonstrated inflammatory tissue consistent with infection. The results of the initial Gram stain were negative. Permanent histological examination of the tissue was consistent with chronic inflammation.
The results were discussed with the patient, and the decision was made to perform resection arthroplasty of the right hip, with placement of an antibiotic-eluting spacer. A posterior approach was used. The hip capsule was hypertrophic and boggy, and the femoral head was eroded. Hypertrophic soft tissue that surrounded the entire femoral neck and the acetabulum was excised. The femoral neck was cut approximately 2 cm above the lesser trochanter, and head and neck tissue samples were sent to the pathology laboratory for permanent histological evaluation. Group B streptococcus was recovered during the initial biopsy and the subsequent resection arthroplasty. Once the femoral head and neck were removed, all pathologic tissue was excised and thoroughly debrided, and a Prostalac cement spacer (Biomet Orthopedics, Warsaw, Indiana) was fabricated with 2 gm of vancomycin and was then inserted (Figs. 4-A and 4-B).
Postoperatively, the Infectious Disease service recommended a four-week regimen of ceftriaxone (2 g intravenously daily), followed by six weeks of levofloxacin (750 mg orally daily). The patient completed this protocol; serial infectious markers were monitored and had trended down. After being off antibiotics for eight weeks, the ESR measured 8 mm/h and the CRP level measured <1 mg/L. Twenty weeks after the resection arthroplasty, the patient underwent hip aspiration. Two weeks later, final culture specimens were negative. The antibiotic spacer was removed, and a biopsy and total hip arthroplasty were performed. At the time of the definitive surgery, there were no gross signs of infection, and frozen-section analysis demonstrated less than five polymorphonuclear cells per high-power field. The total hip arthroplasty was performed without complication. Culture specimens taken during the final procedure were negative.
On follow-up at seven months after the total hip arthroplasty, the patient was walking without assistive devices; she was pain-free, and she denied fever, chills, or malaise. The incisions were well healed, and radiographs demonstrated adequate alignment of the prosthesis without loosening (Figs. 5-A and 5-B). She had resumed normal activities of daily living.
Case reports of joints infected with group B streptococcus following abortion can be found in the literature5,6. DeNoble and Gonzalez reported a case of group B streptococcal septic arthritis of the shoulder following elective dilation and evacuation5. McKenna and O'Brien reported one case of septic arthritis of the sacroiliac joint following elective dilation and evacuation6. Cases of septic arthritis following parturition have been reported by Liu et al.7 and Wilbur et al.8; in both cases, the sacroiliac joint was affected. However, the causative agent was not reported in either case.
Several comorbid conditions are identified as increasing the risk of group B streptococcal infection, including diabetes mellitus, malignancy, HIV, and liver cirrhosis1,9,10. Whether men or women are at increased risk varies according to age. Farley et al. demonstrated that 68% of patients younger than sixty years old who were infected with group B streptococcus were men, while more than half of those over sixty years old were women1. Nolla et al. demonstrated that 68% of nonpregnant patients had group B streptococcal arthritis restricted to one joint, while the remaining 32% presented with polyarthritis. The most commonly affected joint was the knee (36% of patients), followed by the shoulder (25% of patients). The hip joint was affected in 16% of patients11.
Group B streptococcal infection in pregnant and postpartum women typically causes urinary tract infection, sepsis, meningitis, osteomyelitis, endocarditis, amnionitis, endometritis, wound infections, cellulitis, and fasciitis. In the nonpregnant population, the most common group B streptococcal presentation is primary bacteremia, with resultant skin or soft-tissue infection, such as cellulitis, infected peripheral ulcers, osteomyelitis, septic arthritis, decubiti, or wound infections. Less common presentations in the nonpregnant population are pneumonia, urosepsis, endocarditis, peritonitis, meningitis, and empyema12. Dental-related group B streptococal infections must be considered, underscoring the importance of a thorough history.
Group B streptococcus is part of the normal flora of the genitourinary tract. During pregnancy, its presence increases11. Septic arthritis caused by group B streptococcus is uncommon, but when it does present clinically in pregnant, postpartum, or postabortion women, it is commonly found at the sacroiliac joint6-9. In our patient, the hip joint rather than the sacroiliac joint was affected. Howell and Sheddon postulated a hematogenous mechanism via retrograde flow as the ligamentum teres drains into the obturator venous system4.
Although postpartum septic arthritis is rare, our case demonstrates the need to include a septic etiology in the differential diagnosis when determining the cause of hip pain, low back pain, and buttock pain in postpartum women. Our patient had experienced hip pain for four months prior to presentation at our institution. Etiologies such as transient osteoporosis and intrapelvic pathology may preclude a physician from recognizing signs of septic arthritis. This emphasizes the importance of early radiographic studies if septic arthritis is part of the differential diagnosis in a postpartum woman. Difficulty weight-bearing and limited joint motion should also be concerning signs. Imaging is appropriate for a woman who is postpartum. However, if septic arthritis is suspected in a pregnant woman, blood work (including WBC, ESR, and CRP levels) should be assessed. In our patient, the delay in diagnosis caused irreparable destruction of the hip, which necessitated resection arthroplasty, the administration of antibiotics, and a total hip arthroplasty.
To determine the patient population at risk for group B streptococcal infection, Schuchat and the Centers for Disease Control recommend prenatal screening for group B streptococcal colonization in all pregnant women12. The American College of Obstetricians and Gynecologists (ACOG) support this recommendation13. Screening by swabbing the vaginal introitus and rectum between thirty-five and thirty-seven weeks of pregnancy is recommended. Pregnant women with positive group B streptococcal cultures should be administered antibiotics at the onset of labor or at the time of membrane rupture (if it occurs before labor)12-14. The ACOG recommends penicillin as the antibiotic of choice, with ampicillin as a second option13. Dechen et al.15 and Jackson et al.10 suggest immunization as a potential option. While screening is part of many obstetric protocols, our patient was never tested nor treated for group B streptococcus.
Group B streptococcus is classically associated with neonatal sepsis, yet a heightened awareness of postpartum and postabortion infection has implemented a treatment protocol in the peripartum period, which has minimized such infections. It is imperative that members of health care teams identify such an infection in the postpartum patient. Vigilance can prevent the catastrophic outcome that occurred in our patient.