Subacute Osteomyelitis (Brodie Abscess) Treatment & Management

Updated: May 27, 2020
  • Author: Khalid I Khoshhal, MBBS, FRCS(Edin), ABOS; Chief Editor: Thomas M DeBerardino, MD  more...
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Treatment

Approach Considerations

Treatment of subacute osteomyelitis is controversial. No literature exists to support medical treatment in adults, because this condition mostly affects patients in the pediatric age group. Until medical treatment in adults is described, surgical treatment of subacute osteomyelitis in this population is indicated. No true contraindications for surgical intervention exist; medical treatment alone without biopsy or curettage is still debated in the literature, though more and more studies are showing the success of the medical treatment. [14]

A number of authors have maintained that in patients with characteristic clinical and imaging findings and laboratory results, treatment with antibiotics alone may be undertaken without biopsy, at least in the pediatric age group. [3, 23, 32, 34, 38, 39, 30, 14, 40] In the literature, opinion differs as to whether treatment should be surgical or medical for these classic lesions.

Failure of symptoms to resolve after an up to 6-week course of antibiotics or worsening of the condition during treatment should lead to reevaluation and a definite tissue or bacteriologic diagnosis, followed by surgical treatment and appropriate antibiotics. Other indications for surgery include aggressive lesions (indistinguishable from malignant bone tumors) and impending sinus formation or drainage into a synovial joint. Clinical signs of subperiosteal pus or synovitis indicate that the subacute infection has transformed into an acute component, and it must be drained surgically.

Diagnostic experience and awareness of the condition significantly reduce the indications for surgery, from an approach in which biopsies are taken of all lesions to an approach in which biopsies are taken of only selected lesions.

Development of molecular assays for the direct detection of microorganisms has been an actively growing specialty. Amplification techniques such as those using polymerase chain reaction (PCR) should provide increased sensitivity because of the extensive amplification of target nucleic acid to identify the RNA or DNA of viruses, bacteria, and other microorganisms in patients' blood. At present, however, these techniques are not widely available.

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Medical Therapy

Treatment of subacute osteomyelitis depends on the diagnosis. Almost one third of cases (the group that was categorized by Ross and Cole as comprising aggressive lesions [32] ) are indistinguishable from primary malignant bone tumors. Biopsy and curettage are required for diagnosis in these cases.

Once the diagnosis is established, appropriate antibiotic therapy (with the dose adjusted according to the patient's weight and age) based on Gram stain, culture, and sensitivity results should be initially started intravenously (IV) for 2-7 days, followed generally by 6 weeks of oral antibiotic therapy. (Consultation with pediatric or adult infectious diseases specialists is recommended for determining dosage, route, and duration.)

Clinical and laboratory (erythrocyte sedimentaion rate [ESR] and C-reactive protein [CRP]) monitoring of clinical improvement is appropriate. Ezra et al reported their criteria for changing from IV to oral antibiotics to be marked cessation of pain, subsidence of swelling, and functional improvement. [33]

In cases where clinical and imaging findings and laboratory results are characteristic (ie, where the diagnosis is not uncertain), treatment with antibiotics alone, though admittedly controversial, may be undertaken as suggested by Bogoch et al, [38] Ross and Cole, [32] Andrew and Porter, [39] Martin, [41] Hamdy et al, [30] Ezra et al, [33, 34] Pabla et al, [42] and Gonzalez-Lopez et al. [3] In the literature, opinion differs as to whether treatment for these classic lesions should be surgical or medical.

Although most of the available pediatric orthopedic literature supports medical treatment, no literature regarding treatment in adults is available to support either medical or surgical treatment (apart from recommending biopsy). Most orthopedic surgeons treating adults feel more comfortable with surgical treatment. A review of 407 patients with Brodie abscess found that 77% of cases were treated with surgery followed by antibiotics and 17% with surgery alone. [43]

Ross and Cole reported an 87% success rate and Ezra et al reported a 96% success rate with a single course of medical treatment. [32, 33] Hoffman et al found that medical treatment with only biopsy (no curettage) was successful in every case of diaphyseal subacute osteomyelitis they treated (biopsy was required to exclude malignancy). [44] In another study, Ezra et al reported a 90% success rate in medically treating subacute osteomyelitis in tarsal bones. [34]

Failure of resolution of symptoms after a course of antibiotics of up to 6 weeks or worsening of the condition during treatment should lead to reevaluation and a definite tissue diagnosis, bacteriologic diagnosis, or both, followed by surgical treatment and appropriate antibiotics.

Other indications for surgery are impending sinus formation or drainage into a synovial joint. Clinical signs of subperiosteal pus or synovitis indicate that the subacute infection has transformed into an acute component and therefore must be drained surgically. If the patient is being treated empirically, a broad-spectrum antibiotic should be given that covers S aureus first and other pathogens secondarily. Coverage should be considered for H influenzae in young children who have not been immunized adequately.

Antibiotics administered orally for osteomyelitis must be given in doses that often are double to triple those recommended in the agents' package inserts. Patient (or parent) education is essential to maintain the compliance that is required for successful treatment. Absorption of the antibiotic to produce effective concentrations at the site of infection is documented by measuring the concentration of the antibiotic or the antibacterial activity in serum.

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Surgical Therapy

It has been suggested that surgery should be reserved for aggressive lesions. In case of aggressive subacute osteomyelitis with an ESR higher than 40 mm/hr, an abscess larger than 3 cm, or a lesion indistinguishable from a tumor, [25] open biopsy for culture and histology is indicated. Other lesions are incised and drained when indicated, the granulation tissue present in the lesion is curetted and cultured, and antibiotics are started immediately after biopsy.

In pediatric patients with typical cavities in the metaphysis, the epiphysis, or both, surgery is undertaken only for specific indications. When clinical signs of subperiosteal pus are present, treatment consists of incision and drainage. When clinical signs of synovitis are present, with a possibility of pus within a joint, arthrotomy is performed and synovium is sent for culture and histology studies.

If metaphyseal or epiphyseal cavities communicate with the joint, curettage is indicated. Curettage of cavities is also indicated if the symptoms and signs of infection persist during conservative treatment or if they recur. Curettage of metaphyseal cavities should be carried out carefully, and perforations in the growth plate should not be curetted, because curettage of the metaphyseal lesion usually decompresses the epiphyseal lesion.

Ross and Cole reported that all epiphyseal cavities in their study healed with a single course of antibiotics and immobilization without operation. [32] However, when drainage was indicated, the procedure was not performed through the growth plate.

Green et al described curetting epiphyseal lesions after localization by inserting a needle into the epiphysis and obtaining two plain radiographs, then making a 2- to 3-mm drill hole to avoid the weightbearing or the articulating portion of the epiphysis. [45] In the proximal femoral epiphysis, the drill hole must be intracapsular as far distally as possible to avoid the portion of the femoral head that articulates with the acetabulum while avoiding the growth plate. In the distal femoral epiphysis, the drill hole also must be intra-articular but must avoid the weightbearing articular surface coming medially or laterally.

Diaphyseal lesions may be difficult to treat surgically. In patients with these lesions, the clinical picture is more likely to resemble a tumor, and diagnosis requires a surgical biopsy, which should include adequate periosteum, cortical bone, and medullary tissue. These lesions usually respond to adequate antibiotic therapy. In cases that do not respond adequately to medical treatment, exposure of the whole length of the affected bone is indicated, with excision or exposure of all abscess cavities to remove dead bone. The wound is sutured primarily and antibiotics started.

If surgery is undertaken for subacute osteomyelitis lesions that measure more than 3 cm or in cases in which bone is weak and subject to fracture, the cavity could be filled with bone graft or bone graft substitutes (either primary bone grafting, [46] if the surgeon was happy about the total excision of the abscess cavity to eliminate the dead space, or, more appropriately, delaying bone grafting until the antibiotic treatment is completed and the infection is believed to have been eradicated on the basis of clinical and laboratory results).

Other options include the temporary use of antibiotic cement beads and the use of other alternatives to autologous bone graft, such as antibiotic-laden bone graft substitutes. A drain is generally indicated to avoid hematoma or seroma accumulation, which can lead to recurrent abscess, unless the surgeon is completely confident with regard to hemostasis.

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Postoperative Care

In epiphyseal lesions especially, protection of the joints, either with traction or with splinting, and starting protected motion early are important considerations (with intermittent removal of the splint or traction for early range-of-motion exercises). In view of the proximity of the cavity to the articular surface and the risk of collapse, limitation of weightbearing is indicated until evidence of partial healing of the defect is seen on radiographs.

In diaphyseal lesions, the use of a cast or nonweightbearing mobilization can be considered, depending on the size of the excised lesion and the grafting technique used.

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Complications

In pediatric cases of subacute osteomyelitis, 24% of infants younger than 1 year experience complications, compared with 8.5% of older children. [28] In epiphyseal or epiphyseal-metaphyseal lesions, because of the proximity of the cavity to the articular surface, there is a risk of collapse, as well as a risk of pus discharge into the joint; Ross and Cole reported two such cases, one of the hip and one of the ankle joint. [32] Effusions into the hip joint were also reported by Ross and Cole in two patients who had closed cavities in the femoral neck.

Injury to the growth plate during surgical treatment (curettage) is also a possibility. In large lesions, especially diaphyseal lesions, the involved bone might become weak and prone to fracture after surgical treatment.

Ross and Cole reported recurrence in three of 32 patients. [32] Ezra et al reported recurrence in one of 21 patients treated with antibiotics only [33] ; all of their patients responded to curettage and antibiotics. Stephens and MacAuley reported that the age and sex of the patient, the size of the abscess, and the length of IV therapy did not influence the rate of recurrence, but they noted more recurrences in patients who were given a shorter course of antibiotics (2-3 weeks) and in patients with an initial high ESR level (mean of 30 mm/hr in the recurrence group; mean of 8 mm/hr in the group without recurrences). [46]

Although frequently located adjacent to the epiphyseal plate, subacute osteomyelitis rarely results in retardation or stimulation of growth, with Gonzalez-Lopez et al reporting a single case of 15-mm growth stimulation (these lesions are quiescent lesions and hyperemia is minimal) [3] and Ross and Cole reporting a single case in a child with a metaphyseal and epiphyseal lesion of the proximal femur that resulted in growth retardation. [32]

Despite evidence of penetration of the physis by the abscess, growth impairment is extremely rare. Subacute abscesses that traverse the epiphyseal plate do so in only one small cross-sectional area, which may explain the absence of bony bridging. Thus, on the basis of all the recorded experience with this condition, growth disturbance seems unlikely.

That stated, Lindenbaum and Alexander reported a case with varus recurvatum deformity of the knee (a metaphyseal-epiphyseal lesion that was present for more than 3 years before treatment). [10] Stephens and MacAuley reported coxa vara in one patient, mild shortening (7 mm and 15 mm) in two patients, and growth stimulation in two patients (7 mm and 10 mm). [46]

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Long-Term Monitoring

Follow-up in cases of subacute osteomyelitis should continue for at least 2 years.

In the first week, the patient should be closely monitored for signs of response to treatment (clinical and laboratory). Clinical response usually is noted within a few days of initiation of treatment. Compliance with antibiotic therapy should be monitored for 6 weeks.

In the first 6 months, monitoring for signs of recurrence is warranted. Most recurrences occur within 6 months, but recurrence after intervals as long as 18 months has been reported.

Radiologic healing is slower than clinical healing and usually occurs within 3-12 months. Metaphyseal and epiphyseal cavities usually disappear or heal, leaving either a small area of sclerosis or a small, indistinct lucency in the cortex.

After 1 year, the main purpose of follow-up after 1 year to assess bone growth and alignment, though physeal growth is very rarely affected.

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