Case Presentation:  A 38-year-old para 2 healthy female presented with left shoulder pain 4 weeks after an uncomplicated vaginal delivery at 41 weeks gestation.  Rectovaginal swab and culture obtained at 37 weeks gestation was negative for group B streptococcus (GBS) colonization.  One week postpartum, she developed a fever of 100.8 F, left shoulder pain and pelvic cramping. Physical exam, including pelvic exam, was unremarkable.  Blood and urine cultures were negative.  She was clinically diagnosed with endometritis and discharged on a 7 day course of ciprofloxacin and metronidazole.  All her symptoms resolved except for left shoulder pain, which was attributed to a hairline clavicular fracture secondary to trauma during delivery.  Her shoulder pain worsened over the next 3 weeks despite supportive treatment.  An outpatient MRI revealed septic arthritis and osteomyelitis of the left sternoclavicular joint (SCJ).  Physical exam was notable for normal vital signs with tenderness, erythema, and swelling overlying the left SCJ.  Laboratory findings included a white blood cell count of 6.0 K/uL, an erythrocyte sedimentation rate of 84 mm/hr and a C-reactive protein of 27 mg/L.  She underwent left sternoclavicular drainage and bone debridement with biopsy and culture, followed by Vacuum-Associated Closure placement.  Wound cultures grew GBS; blood cultures were negative.  She was treated with intravenous (IV) ceftriaxone for 4 weeks and transitioned to oral amoxicillin.

Discussion: Septic arthritis and osteomyelitis due to GBS have been observed among neonates, children, and immunocompromised adults, but are extremely rare in healthy adults.  GBS has been cited as the cause of rare postpartum invasive infections including endocarditis, meningitis, bacteremia, septic arthritis and osteomyelitis.  Our patient had tested negative for GBS colonization and did not receive chemoprophylaxis.  We hypothesize that she became colonized with GBS during delivery, causing postpartum endometritis due to bacterial ascension.  The transient bacteremia eventually seeded her SCJ, resulting in septic arthritis and osteomyelitis.  Alternatively, the low sensitivity (40-60%) of the rectovaginal swab and culture may have resulted in a false negative result.  Sternoclavicular septic arthritis is also very rare among healthy adults and few cases have been attributed to GBS, since it is usually caused by Staphylococcus aureus and tends to occur in IV drug users.  However, given her recent delivery and intrapartum trauma, we conjecture that our patient had a rare manifestation of sternoclavicular septic arthritis and osteomyelitis due to hematogenous spread of GBS during or after delivery. 

Conclusions: Septic arthritis requires prompt recognition and surgical debridement to avoid permanent joint damage.  Although rare, septic arthritis and osteomyelitis should be included in the differential diagnosis for postpartum women with joint pain regardless of prior GBS colonization.