Simon G F Abram, Abtin Alvand, Andrew Judge, David J Beard, Andrew J Price
Lancet Infect Dis 2020;20: 341–49. Published Online December 17, 2019
Summary by Michael Yayac MD
Although uncommon, septic arthritis is considered a medical emergency due to the severe consequences if not properly treated [1-2]. This condition most commonly affects the knee, but outcomes of septic knee arthritis are largely unknown as no current literature has focused on the knee and outcomes of previous studies are greatly varied with mortality rates ranging from 0.8%-15% [1–4].
Abram et al. present a longitudinal cohort study of 12,132 patients undergoing arthroscopic washout of the knee for septic arthritis at a National Health Service (NHS) hospital in England between April 1,1997 and March 31, 2017. Patients with a history of surgery to the same knee were excluded. The cohort was divided into patients whose primary diagnosis was septic arthritis (n=10,195) and patients in whom septic arthritis was a secondary diagnosis (n=1,937). Outcomes analyzed included 90-day mortality and one-year adverse joint outcomes (arthrodesis, amputation, and arthroplasty). 90-day mortality for the whole cohort was 8.9% with significant risk factors including a secondary diagnosis of septic arthritis (adjusted odds ratio (a-OR) 2.1, p<0.0001), age (per 5 years) (a-OR 1.38, p<0.0001), year of treatment (per 5 years) (a-OR 0.89,p=0.0018), history of knee osteoarthritis (a-OR 0.72,p=0.0006), and history of diabetes mellitus (a-OR,p<0.0001). One-year adverse joint outcomes were reported as 0.13% (0.07-0.22) for arthrodesis, 0.40% (0.30-0.54) for amputation, and 1.33% (1.13-1.56) for arthroplasty. Annual risk of arthroplasty for patients age 30 or older was found to be 1.29% (1.03-1.60) which is greater than six times that of the general population (0.21%). Greatest risk was found in patients age 40-49 with an observed risk ratio of 27.25 (13.01-57.09).
Noted limitations of this study include that analysis was limited to data available in Hospital Episode Statistics database of NHS hospitals. In addition, this study only reported outcomes of patients undergoing arthroscopic washout and therefore, the results described here cannot be generalized to patients treated through conservative measures or open procedures. Finally, while the investigators attempted to exclude patients with iatrogenic septic arthritis by removing patients with a history of knee surgery from the cohort, it is possible that cases of iatrogenic septic arthritis, secondary to aspiration, for example, were included. Despite these limitations, findings of this study suggest that mortality and morbidity associated with septic knee arthritis may be considerably higher than previously reported.
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