Pediatric Acute Hematogenous Osteomyelitis

PEDIATRIC ACUTE HEMATOGENOUS OSTEOMYELITIS

THOMAS KIM, MD, Orthopaedic Resident

J. RICHARD BOWEN, MD, Orthopaedic Attending

April 1, 1995

CLINICAL CASE PRESENTATION

ORTHOPAEDIC DEPARTMENT

THE ALFRED I. DUPONT INSTITUTE

WILMINGTON, DELAWARE

CASE HISTORY:

Day of Admission to a hospital: this 9 month old male child had a history of a normal pregnancy, delivery and growth. The mother noted a fever of unkown origin for the previous 2 days with vague abdominal pain and diarrhea. Initial workup revealed: temp 104, WBC 16,800 with left shift, CXray/Abd/Pelvis/Hip Xrays negative, bone scan negative, spinal tap neg. The infant was admitted with a diagnosis of viral infection vs. mycoplasma pneumonia. Started on erythromycin.
Hospital Day 2: Right hip was noted to be flexed and orthopaedic services consulted. The right hip was aspirated, Gram stain: G PC, Started on Nafcillin 150mg IV q4. The child than had daily hip aspirations for decompression. Final culture: coag (+) Staph aureus resistant to PCN.
Hospital Day 6: Respiked to 103.4. R hip Xray showed a defect in proximal medial metaphysis, Possible osteomyelitis. The child was than taken to the operating room for Incision & Drainage of Right hip via anterolateral approach with suction irrigation system (seropurulent fluid drained).
Post Operative Day 7: Drains removed. Respiked to 101.6. R hip Xray: suggestion of demineralization of proximal metaphysis. The hip was reaspirated and pus was obtained. Cultures neg.
Post Operative Day 12: Respiked to 103.6. Gentamicin 1 mg IV q6 added to Nafcillin. Daily aspirations of 10 cc purulent fluid, all cultures neg.
Post Operative Day 18: R hip Xray: subluxation of R hip, possible metaphyseal lucency consistent with osteomyelitis. Taken to OR for repeat I & D of R hip via posterior approach with Penrose drains and hip spica cast (15cc seropurulent fluid drained). Antibiotics changed to Oxacillin 225mg IV q4.
Post Operative Day 7: Drains removed. Afebrile.
Post Operative Day 9: Afebrile for 48hrs. Transferred to AI duPont Institute. Initial labs: WBC 15,100, ESR 72. R hip Xray: changes in proximal . metaphysis including lucency and demineralization, hip subluxated. Treated with oxacillin and Pavlik harness.
Hospital Day 12: WBC 12,600, ESR 48. Discharged home in Pavlik harness x 1 yr., Oxacillin 250mg po q4.
2 month Office Follow Up: Rt hip Xray: progressive destruction of capital femoral epiphysis, cystic changes in metaphysis consistent with AVN.
Age 6: Valgus osteotomy for subluxation and 2cm leg length inequality.
Age 15: Valgus osteotomy for hip incongruity.
Age 20: Hip arthroscopy. Hip fusion recommended.

Introduction

Before advent of antibiotics, acute hematogenous osteomyelitis had mortality rate as high as 45%.

After introduction of PCN in 1944, mortality rate < 1 %.

No consistent peak incidence by age group.

Acute hematogenous osteomyelitis may coexistst with septic arthritis especially in patients. < 12-18 months of age and in joints with intra-articular metaphyses (eg. proximal humerus, proximal femur, distal lateral tibia, proximal radius).

Pathogenesis

Risk factors: trauma (regional ischemia), bacteremia, illness, malnutrition, immune system deficiency. Infection begins in metaphyseal venous sinusoid (sluggish blood flow, poorly developed reticuloendothelial system).

Exudate exits porous metaphyseal cortex and forms subperiosteal abcess, involucrum, sequestrum.

Evaluation and Diagnosis

HISTORY

H/O recent or concurrent infection in 1/3 to 1/2 of cases.
Unexplained bone pain and fever = osteomyelitis until proved otherwise.

LABS:

WBC not invariably elevated (Scott et al: 41 % had WBC < 10,500).
ESR elevated in majority of cases (not reliable in neonates, patients with sickle cell anemia, lags behind clinical improvement).
C-reactive protein (Unkila-Kallio et al: elevated in 98% of cases, peak level on day 2, normal within a week of treatment).
Blood cultures positive in 40 - 50% of cases.

XRAY:

Early: deep soft tissue swelling only.
Bone changes usually not present until > 1 week.
Bone scans: Technetium-99m useful for localization in spine and pelvis, detecting multiple sites of involvement.
Not accurate in very early cases (< 24 hrs).
Non specific (trauma, tumor, infection).
False negative rate 4 - 20%.
Bone aspiration does not affect results of bone scan if bone scan obtained within 48 hrs after aspiration (Canale et al).

MRI:

Sensitivity = bone scan
Specificity > bone scan

ASPIRATION:

Most valuable clinical test. Positive in 85-90% of cases.
Neonates: group B Strop > Staph aureus
Infants & children: Staph aureus (90% of cases)
H. influenzae (6mo - 4yr)
Sickle cell disease: Staph aureus > Salmonella

Treatment

                        Probable                                Initial

Patient Type            Organism*                               Antibiotic



Neonates                Group B Streptococcus,         Cefotaxime, 100-120

                        Staphylococcus aureus,         mg/kg of body weight

                        or Gram-negative rods          for 24 hr, or oxacillin and

                        Hemophilus influenzae          gentamicin, 5.0-7.5

                                                             mg/kg for 24 hr



Infants and             S aureus (90% of cases)        Oxacillin, lz-)o mg/kg for 24 hr

        children                        

If allergic to                                         Cefazolin, 100 mg/kg for 24 hr

        penicillin                      

If allergic to                                         Clindamycin, 25-40 mg/kc,

        penicillin and                                 for 24 hr, or vancomvcin,

        cephalosporins                                 40 mg/kg for 24 hr



Patients with sickle    S aureus or Salmonella         Oxacillin and ampicillin 

        cell disease                                   chloramphenicol or cefotaxime, 

                                                       100-126 mg/kg for 24 hr

Duration of antibiotics: 6 weeks

Switch from IV to oral antibiotics once clinical response is seen (7 - 1 0 days).

Usual oral antibiotics: Dicioxacillin 50 mg/kg over 24 hr or Cephalexin 150 mg/kg over 24 hr

90% response rate to antibiotics alone when treatment is initiated within first few days after onset of symptoms.

SURGICAL INDICATIONS:

aspiration of pus (ie. abcess) sequestra in chronic osteomyelitis joint sepsis
delayed clinical response to antibiotics(> 36 hr)

Neonatal Osteomyelitis

Metaphyseal vessels penetrate directly into chondroepiphysis up to 12 - 18 mo.

Infections starting in metaphysis readily spread to chondroepiphysis and joint.

Multiple sites involved in 40% (immature immune system).

This case is an example of untreated septic arthritis which caused avascular necrosis of the proximal femur. The primary cause of this is undrained septic hip. Repeated aspiration is not adequect treatment of a septic hip.

References

Canale ST, Harkness RM, Thomas PA, et a[: Does aspiration of bones and joints affect results of later bone scanning? J Pediatr Orthop 1985;5:23-26.
Cole WG, Dalziel RE, Leitl S: Treatment of acute osteomyelitis in childhood. J Bone Joint Surg Br 1982;64:218-223.
Dormans JP, Drummond DS:. Pediatric Hematogenous Osteomyelitis: New trends in presentation, diagnosis and treatment. J AAOS 1994;2/6: 333-341.
Green NE, Edwards K: Bone and joint infections in children. Orthop Clin North Am 1987;18(4):555-576.
Jackson MA, Nelson JD: Etiology and medical management of acute suppurative bone and joint infections in pediatric patients. J Pediatr Orthop 1982;2:313-323.
Morissy RT: Bone and joint infections, in Morrissy Rt (ed): Lovell and Winter's Pediatric Orthopaedics, 3rd ed. Phila: Lippincoft, 1990, vol 1, pp 539-561.
Scoff RJ, Christofersen MR, Robertson WW Jr, et al: Acute osteomyelitis in children: A review of 116 cases. J Pediatr Orthop 1990; 10:649-652.
Unidia-Kallio L, Kallio MJT, Eskola J, et al: Serum C-reactive protein, ESR, and WBC in acute hematogenous osteomyelitis of children. Pediatrics 1994;93:59-62.