– The higher the comorbidity burden, the greater the likelihood that osteomyelitis will lead to amputation within 2 years, according to a review of 1,186 adult osteomyelitis patients at the University of Michigan, Ann Arbor.

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The limb amputation incidence was 7.2% over 2 years in patients with no comorbidities, 21.4% among patients with heart failure, 36.1% in patients with diabetes, and 36.7% among those with peripheral vascular disease (PVD).

The 2-year incidence marched steadily upward with combined comorbidities to 47.4% in patients with diabetes and heart failure; 64.5% in patients with diabetes and PVD; and 75.0% in patients with diabetes, heart failure, and PVD.

“What this means is that looking at diabetes versus no diabetes alone is not sufficient to gauge the risk of amputation. We have to look at the patient’s comorbidity profile as a whole; greater comorbidity burden and different combinations of comorbidities [increase] amputation incidence, but there’s considerable risk [7.2%] even among otherwise healthy patients,” said lead investigator Toby Keeney-Bonthrone, a medical student at the university.

The ultimate goal of the work is to develop an osteomyelitis amputation risk calculator for physicians and patients to improve decision making, validated by nationwide data. “The question is if some patients would benefit from [an earlier,] more prophylactic amputation. Would it be better to just take off the limb and be done with it, and would that decrease overall morbidity?” he said at the annual clinical congress of the American College of Surgeons.

“We often find ourselves reacting to osteomyelitis as it progresses. I think patients deserve a better deal than that. They deserve for us to think one or two steps ahead,” Mr. Keeney-Bonthrone said.

The immediate goal of the study was to fill the data gap on long-term osteomyelitis outcomes, something that hasn’t been addressed much in the literature. The team reviewed adult patients from 2004 to 2015 who were followed for at least 2 years after diagnosis; 610 had diabetes, a known risk factor for osteomyelitis and amputation, and 576 did not.

Comorbidities were considerably more common in the diabetes group, including PVD and heart failure, but also chronic obstructive pulmonary disease, previous heart attack, prior amputation, and especially renal disease. The 2-year amputation incidence was also higher in the diabetes group (43.1% vs. 12.3%), as was 2-year mortality (22.3% vs. 15.5%).

Odds ratios for lower limb amputation climbed in a stepwise fashion on multivariate analysis, from almost a 100% increase in men and in black patients to a 158% increase among patients with past amputations; a 206% increase with PVD; a 256% increase in patients with type 2 diabetes, and a 349% increase among patients with type 1 diabetes. The investigators were puzzled that the amputation risk was higher among type 1 patients than in those with type 2, because comorbidity burdens are generally higher in type 2 diabetes.

No data was provided on treatment differences between the groups, including antibiotic use.

The work was funded by the National Institutes of Health. The investigators reported no relevant disclosures.

SOURCE: Keeney-Bonthrone T et al. J Am Coll Surg. 2018 Oct;227(4), S105.