Diagnosing pedal osteomyelitis

Abstract

Objective: To compare the efficacies and cost-effectivenesses of four strategies for the management of suspected pedal osteomyelitis in the setting of vascular impairment: 1) therapeutic trial of short-term antibiotics for presumed cellulitis without osteomyelitis (short); 2) technetium bone scanning followed by either short-term therapy if negative or either a biopsy or aggressive long-term intravenous therapy if positive (scan); 3) bone biopsy followed by long-term intravenous therapy if positive or short-term therapy if negative (biopsy); and 4) immediate long-term intravenous antibiotics for presumed osteomyelitis (long).

Design: Decision analysis and cost-effectiveness analysis with sensitivity analyses. The main outcomes states are amputation and the resource expenditures associated with bone scans, biopsies, and therapies.

Data sources: The authors obtained estimates of test accuracy from literature review and summarized them using newly developed meta-analytic techniques.

Main results: The optimal decision depends heavily on the estimated probability of osteomyelitis at presentation. At very low probabilities, the short-term strategy is preferred. When the probability of osteomyelitis is from 2% to 8%, the lowest amputation rate occurs when one does a diagnostic scan. From 8% to 50%, the best outcomes follow biopsy. At probabilities higher than 50%, the preferred strategy is long-term antibiotics. However, the differences in outcomes are quite small even when osteomyelitis is a virtual certainty.

Conclusions: Over the whole range of prior probabilities, the short-term strategy is the least expensive. At very low probabilities, it dominates the other strategies. When the likelihood of osteomyelitis is higher (10–20%), scanning results in outcomes and cost-effectiveness ratios comparable to those of immediate biopsy and is less invasive. When the probability of osteomyelitis is 50%, biopsy is quite cost-effective compared with all the other strategies (cost-effectiveness ratio = $15,502 per amputation averted) and is preferred to the scan strategy. When the confidence that a patient has osteomyelitis is very high (>90% probability), the improved outcomes associated with long-term antibiotics are achieved with little additional expense and with favorable cost-effectiveness ratios compared with those of the other strategies.