ankle pain

An 11-year-old girl with right ankle pain (page 2)

Prepared by.... Shanika Kosarat M.D.
Thanyawee Puthanakit M.D

What is your diagnosis?
Acute osteomyelitis of the right tibia

What are the proper managements?

1. Starting intravenous anti-staphylococcus antibiotic (cloxacillin 150 MKD)
2. Needle aspiration of the right tibia.

The needle aspiration did not obtain any pus.

What should be the next investigation?
Bone scan................... see figure 1

Figure 1: 99 Technitium scan:
Three-phase bone scan of both legs.
The dynamic and blood pool imaging shows increased perfusion and blood pool in the right leg.The static images show intense increased uptake at the metaphysis of the right distal tibia, compared with normal uptake on the left side. The remaining skeleton is unremarkable.

The surgery at the right distal tibia obtained 50 cc of pus under the periosteum.
Gram stain : see figure 2


	Figure 2 : Gram stain revealed numerous PMN with gram positive cocci in cluster

Course in the hospital

	After the surgical drainage the fever gradually subsided. She was given intravenous cloxacillin for 4 weeks.

Final Diagnosis : Acute osteomyelitis of the right tibia

Discussion: Acute osteomyelitis
Pathogenesis

>	Disease of young children because of the rich vascular supply of rapidly growing bones.
>	Hematogenous in origin
>	One-third of patients has minor trauma to the affected extremity prior to infection
>	Metaphysis of long bone is the most common site of infection
>	Risk of joint involvement in the following setting
	Hip and shoulder joint; metaphysis of the proximal femur and humerous are intracapsular Age < 18 months; transphyseal vessels providing a connection between the metaphysis and epiphysis

Etiology

S.aureus is the most common cause

The specific microorganism that is associated with the age of the patient

Table 1: The specific microorganism that is associated with the age of the patient (from ref. 2)

Clinical Manifestation

Most frequent manifestation: fever, pain and reluctance to use affected extremities.

Physical signs:

>	Focal swelling, tenderness, warmth, erythema, usually over metaphysic of a long bone.
>	Local swelling and redness mean that the infection has spread out of the metaphysis into the subperiosteal space.
>	Long bone is principally involved in osteomyelitis. (picture 4)

	Figure 4: Site of acute osteomyelitis in whom a single bone was involved. Shaded areas constitute sites of approximately 75% of cases. Miscellaneous sites accounting for 5% are not shown. (from ref. 3)
>	Differential diagnosis from cellulitis: In case of osteomyelitis, tenderness is out of proportion to soft tissue swelling
>	Differential diagnosis from pyogentic arthritis: In case of pyogenic arthritis, there is exaggerated immobility of the joint but lack of point of tenderness over the metaphysis.

Laboratory diagnosis

1. Needle aspiration: Most directly confirmed diagnosis by examination and culture of infected material

2. Complete blood count: Leukocytosis and thrombocytosis

3. Acute phase reactant: Erythrocyte sedimentation rate (ESR), C-reactive protein (CRP)

Table2: Dynamic of acute phase reactant in acute oseteomyelitis (from ref. 3)

	% Abnormal	Value	Peak (Days after initiation of treatment)	Return to normal (Since treatment)
ESR	90%	40-60 mm/hr	3-5 days	3-4 weeks
CRP	98	Mean 83 mg/L	2day	7-10 days

4. Radiologic findings

4.1 Plain radiograph

	• 3 days of onset: deep soft tissue swelling, loss of the visible tissue planes around the bone • 10-20 days after onset: osteolytic lesions, periosteal elevation due to subcortical purulence and periosteal new bone formation • 1 month: sclerosis of bone
4.2 Radionuclide scan: Technetium-labeled methylene diphosphonate isotope
	• The uptake is enhanced when osteoblastic activity is increased • The sensitivity is 80-100%.
4.3 Magnetic resonance Imaging (MRI )
	•The sensitivity is 92-100%. •Differentiate cellulitis from osteomyelitis using signal alterations in soft tissue •Differentiate acute from chronic osteomyelitis

Treatment

Antibiotic selection is based on knowledge of likely bacterial pathogens at various ages, the results of Gram stain of aspirated material, and special considerations.

Table 3: Antibiotic Selection for initial treatment of osteomyelitis (modified from ref. 3)

Age	Likely pathogen	Empirical antibiotics
Newborn	S. aureus GBS Enteric gram -ve	Nafcillin (or cloxacillin) 100 MKD q 6 hr AND Gentamicin 5-7.5 MKD q 8 hr OR Nafcillin (or cloxacillin) 100 MKD q 6 hr AND cefotaxime 150 MKD IV q 8 hr
< 3 years	S.aureus H. influenza b	Nafcillin (or cloxacillin) 150 MKD IV q 6 hr AND Cefotaxime 100-150 MKD q 6 hr OR Ceftriaxone 100 MKD q 12 hr OR Cefuroxime 72-150 MKD q 8 hr OR Ampicillin-sulbactam 300 MKD q 6 hr
> 3 years	S. aureus	Nafcillin (or cloxacillin) 150 MKD IV q 6 hr OR Clindamycin 30 MKD IV q 6-8 hr OR Cefazolin 100 MKD IV q 8 hr

Indications for surgery

• Prolonged fever, erythema, pain and swelling
• Persistent bacteremia despite adequate antibiotic
• Soft tissue or periosteal abscess
• Formation of sinus tract
• Presence of necrotic, nonviable bone

Duration of treatment

At least 3-6 weeks. If duration of treatment less than 3 weeks, it is associated with higher rates of relapse. Plain radiograph at the end of treatment should be performed to document maximal anticipated destruction and served as a baseline for further studies to follow a possible complication.

Sequential parenteral-oral antibiotics:

This can be successful. However, the adherence to oral regimens is critical. Dosage of antibiotics in the oral phase is generally two to three times the usual oral dose (Table 4... from ref 3).

Table 4. Dosage of antibiotics commonly used in the oral phase of treatment of osteomyelitis

Antibiotic	mg/kg/day	Doses/Day
Dicloxacillin	75-100	4
Cephalexin	100-150	4
Clindamycin	30	3-4

References and suggested further readings
1. Nelson JD. Osteomyelitis and Suppurative Arthritis. In: Behrman RE,Kliegman RM, Jenson HB: Nelson Textbook of Pediatrics. 16th ed. Philadelphia: W.B. Saunders company; 2000. Page 776-780.
2. Carek PJ, Dickerson LM, Sak JL. Diagnosis and management of osteomyelitis.
Am Fam Phy.2001; 63(12):2413-20.
3. Kathleen MG. Osteomyelitis. In: Long S, Pickering L and Prober C: Principles and Practice of Pediatric Infectious Diseases. 2nd ed. Philadelphia. Churchill Living stone; 2003. Page 467-474.

Final Diagnosis : Acute osteomyelitis of the right tibia

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