SLR - October 2018 - Bao Tram Nguyen

Culture of Bone Biopsy Specimens Overestimates Rate of Residual Osteomyelitis After Toe of Forefoot Amputation

Reference: JB. Mijuskovic, R. Kuehl, A.F. Widmer, G. Jundt, R. Frei, L. Gurke, T. Wolff. Culture of Bone Biopsy Specimens Overestimates Rate of Residual Osteomyelitis After Toe of Forefoot Amputation. J Bone Joint Surg Am. 2018 Sep 5;100(17):1448–1454.

Scientific Literature Review

Reviewed By: Bao Tram Nguyen, DPM
Residency Program: Montefiore Medical Center, Bronx, NY

Podiatric Relevance: While diagnosis of osteomyelitis (OM) can at times require experience, according to the Infectious Disease Society of America (IDSA), guidelines confirmation of OM is based on bone specimens of both culture and histological analysis; however, often it is based on culture alone. This study is designed to compare cultures and histological analysis of bone specimens taken intraoperatively from the clean margin of the amputation.

Methods: A prospective study over a two-year period of patients requiring an amputation based on clinical evaluation without requirement of radiographic examination. Patients with peripheral arterial disease were treated with the appropriate vascular procedure prior to amputation. A proximal bone biopsy was obtained with precautions to avoid contamination and sent to microbiology and histology for analysis. Standard microbiological techniques were used for identification of microorganisms. Histological diagnosis of OM was defined as presence of neutrophils in addition to either fibrosis, marrow necrosis or perivascular lymphoplasmacytic infiltration. Failure of the initial amputation was one that required a more proximal amputation.
Results: Of the 51 patients enrolled, 65 percent had a positive bone culture. However, only 27 percent demonstrated histological evidence of OM. A negative histological finding but positive culture was found in 41 percent, whereas 12 of the 14 with a positive histological result had positive cultures, and 16 of the 18 with negative culture also had negative histological findings. This suggests that in comparison to histological analysis, culture had a higher false positive rate.  

Conclusion: With more than 100 million Americans diagnosed with diabetes and prediabetes, the need for proper diabetic foot care has never been so important. Often, despite screenings and checkups, patients become victim to infections leading to amputations in the foot due to OM. IDSA guidelines for a definite diagnosis of OM are often not followed leading to inappropriate use of antibiotic therapy contributing to resistance. The authors concluded that the high rate of false positive cultures are affiliated with contamination from surrounding infected soft tissue. While there is an advantage to guided antibiotic therapy, it is important to follow up with histological results to ensure proper overall treatment for the patient.

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