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Hypothesis: Cat bites to the hand pose significant risk of morbidity and can result in varying degrees of infection. Treatment options include observation alone (no treatment), outpatient treatment with oral antibiotics, hospitalization and intravenous antibiotics, and if indicated, surgical irrigation and debridement. Hospitalization and operative management indicate severe infection. This study seeks to assess the overall morbidity of cat bites to the hand and identify risk factors for severe infection after such an injury.

Methods: All patients treated at our institution for cat bite injuries to the hand were retrospectively reviewed. We identified 193 patients between January 2009 and December 2011. Patient demographics, medical history, physical exam findings, laboratory values, hospital course, and long-term followup data were collected. Univariate and multivariate statistical regression were used to analyze the data.

Results: Thirty percent (N=57) of patients with cat bites to the hand were hospitalized. The average length of stay for these patients was 3.2 days. Of the hospitalized patients, 67% (N=38) underwent irrigation and debridement, with 8 patients requiring more than one operation. Complications were common and included abscess formation (N=6), tendon involvement (N=14), nerve involvement (N=2), and loss of joint mobility following resolution of infection (N=14). Risk factors associated with hospitalization included smoking [odds ratio (OR) 2.2, p=0.04], immunocompromised state (OR 5.2, p=0.02), location of bite over joint/tendon sheath vs. soft tissue (OR 2.94, p<0.01), erythema (OR 7, p<0.01), pain (OR 5.7, p<0.01), swelling (OR 6.7, p<0.01), drainage (OR 12.6, p<0.01), warmth (OR 3.1, p=0.01), and decreased range of motion (OR 9.1, p<0.01). Multivariate analysis identified the following as independent risk factors for hospitalization: location of bite over joint/tendon sheath vs. soft tissue (OR 2.4, p=0.02), as well as physical exam findings of erythema (OR 3.9, p=0.02), pain (OR 3.4, p=0.04), and swelling (OR 3.2, p=0.02). Time from bite to presentation, as well as WBC, ESR, and CRP values at presentation, were not significant risk factors of hospitalization.

Summary: Cat bites to the hand pose a high risk for infection and need for hospitalization, and require aggressive treatment. Laboratory findings may not be necessary in the routine evaluation and treatment of cat bite injuries to the hand. Independent risk factors for severe infection include location of the bite over a joint or tendon sheath, erythema, pain, and swelling. These findings should increase concern for a severe infection, and warrant urgent consultation with a hand surgeon.