Background Skin ulcers, particularly digital ulcers occur in at least 50% of systemic sclerosis (SSc) patients (pts) and cause significant morbidity. They are often complicated by local infection which can lead to contiguous osteomyelitis.
Objectives Our aims were to evaluate the accuracy of clinical diagnosis of osteomyelitis and to assess whether there are clinical parameters that may improve the precision of the clinical diagnosis.
Methods We retrospectively analyzed the clinical data of consecutive SSc patients hospitalized for skin ulcers in a tertiary referral center for SSc. Our cohort is part of the EUSTAR cohort. The patients were evaluated by rheumathologists skilled in managing SSc skin lesions. All the patients with infected ulcers and suspected for contiguous involvement of underlying bone had bone scans. All the positive scans were followed with 99m-Technetium-Tc-labeled white blood cells (WBC) scintigraphy, in order to differentiate true osteomyelitis from acro-osteolysis or soft tissue infection. We collected demographic data, disease type, extent and severity, routine lab data (CBC, C-reactive protein -CRP, erythrocyte sedimentation rate (ESR), alkaline phosphatase (ALKP), albumin) and wound culture. Each hospitalization was considered a separate event. Statistical analysis: descriptive, student's T test, Mann-Whitney test.
Results During the years 2003–2016, 220 SSc pts with skin/digital ulcers were hospitalized in our department for ilomedin treatment (993 hospitalizations). Most of the pts were hospitalized several times due to recurrent ulcers. Tc bone scan was performed in 39 pts (59 admissions) with infected ulcers (32 females, mean (SD) age 48 (15), disease duration 9 (6.6) years, 25 with diffuse SSc, skin score (MRSS) 9.9 (8)). Osteomyelitis was confirmed in 18 pts on 23 occasions. Osteomyelitis occurred twice in 5 pts in different locations. No statistically significant differences were found between the group with positive scans and the group with negative scans regarding demographic, clinical and lab data. 9 pts had 25 admissions for infected ulcers, osteomyelitis was confirmed in 14 of the admissions. No statistically significant differences were found for CBC ESR CRP ALKP between the osteomyelitis events and superficial infected ulcer admissions in these pts. The causative infectious agents were similar between the 2 groups. Positive bone and WBC scans confirmed osteomyelitis in 39% of clinical suspected cases. WBC scans confirmed osteomyelitis in 75% or the patients with positive Tc bone scans.
Conclusions The prevalence of osteomyelitis among our SSc pts admitted for digital ulcers was 10%. The prevalence of confirmed osteomyelitis by scintigraphy in clinically highly suspected cases was 39%. Even when contiguous osteomyelitis was suspected by highly skilled rheumathologists, bone scan ruled out the diagnosis in 61% of the cases, thus avoiding unnecessary prolonged antibiotic therapy. No clinical predictors to rule osteomyelitis in or out could be identified.
Disclosure of Interest None declared