Table 1.

Patient characteristics.

Characteristic	Total ( $N=\mathrm{91}$ )
Age, median (IQR)	62.0 (51.5–74.0)
Female sex – $n$ (%)	29 (32 %)
Body mass index (BMI) (kg m-2), median (IQR)	28.2 (23.7–32.8)
Manual occupation – $n$ (%)	8 (9 %)
Abrasions or wounds on the affected elbow – $n$ (%)	16 (18 %)
History of surgery on the affected elbow – $n$ (%)	16 (18 %)
Fall on the affected arm/trauma to elbow – $n$ (%)	36 (40 %)
Comorbidities – $n$ (%)
Diabetes mellitus	17 (19 %)
End-stage renal disease	1 (1 %)
Autoimmune disease	31 (34 %)
Rheumatoid arthritis	20 (65 %)
Inflammatory bowel disease	5 (17 %)
Other	6 (19 %)
Hematologic malignancy	3 (3 %)
Solid malignancy	4 (4 %)
Smoking history, $n$ (%)
Never smoker	43 (47 %)
Current smoker	18 (20 %)
Former smoker	30 (33 %)
Pharmacologic immunosuppression, $n$ (%)*	26 (29 %)
Prednisone	18 (69 %)
$>$  20 mg of prednisone equivalents for $\ge$  2 weeks	4 (22 %)
TNF- $\mathit{\alpha }$ inhibitor	5 (19 %)
Methotrexate	5 (19 %)
Other	14 (54 %)
Clinical presentation
Duration of symptoms prior to presentation, median (IQR), $N=\mathrm{89}$	13.0 (4.0–53.0)
Fever (temperature $>$  38.3 °C) – $n$ (%)	13 (14 %)
Local signs of inflammation at time of presentation – $n$ (%)
Mild–moderate swelling, redness, and/or pain	44 (48 %)
Moderate–severe swelling, redness, and/or pain	29 (32 %)
Extensive peribursal cellulitis	18 (20 %)
Presence of wound overlying the bursa – $n$ (%)
No open wound	31 (34 %)
Minor skin lacerations	5 (6 %)
Small open wound	23 (25 %)
Sinus tract/fistula	32 (35 %)
Bursa imaging – $n$ (%)	17 (19 %)
Ultrasound showing fluid collection in the olecranon bursa	2 (12 %)
CT scan showing fluid densities in the subcutaneous tissues	4 (24 %)
CT scan showing hypodense bursa with wall enhancement	5 (29 %)
MRI showing bursal fluid collection with T1/T2 changes and gadolinium enhancement	9 (53 %)
MRI showing evidence of osteomyelitis	1 (6 %)
Laboratory data within 48 h of surgery, median (IQR)
White blood cell count (WBC) ( $\times {\mathrm{10}}^{\mathrm{9}}$  L-1), $N=\mathrm{74}$	9.2 (7.2–11.9)
Erythrocyte sedimentation rate (ESR) (mm s-1), $N=\mathrm{32}$	38.0 (16.0–60.5)
C-reactive protein (CRP) (mg L-1), $N=\mathrm{42}$	58.3 (13.3–139.4)

^* Represents the number of times a specific immunosuppressive medication was used, whether alone or in combination with other medications, among the 26 patients who were receiving pharmacologic immunosuppression. Other medications include mycophenolate, azathioprine, tacrolimus, rituximab, tocilizumab, and chemotherapy