Extensive MRSA-positive sternoclavicular septic arthritis with uncommon origin: a case report

Introduction

Sternoclavicular joint (SCJ) infections are extremely rare; they account for less than 1% of bone infections (1). SCJ is unilateral in almost all the reported cases, affecting mainly the right side (2). The most frequent route of infection of the SCJ is hematogenous transmission through the bloodstream, while it can also happen by direct inoculation of the joint or contiguous dissemination from a nearby region. About 62% of patients with SCJ infections have bacteremia (3). Poorly controlled diabetes mellitus is a major predisposing factor due to impaired neutrophil function and microvascular disease (4). Examples of the entry sites of SCJ infections are: (I) local skin infection; (II) upper extremity venous access sites; (III) oropharyngeal/dental source; (IV) pneumonia; (V) chronic osteomyelitis; (VI) non-sterile injection, mostly among drug abusers. The vast majority of the infections are linked to other systemic diseases such as diabetes mellitus, chronic kidney disease, and rheumatoid arthritis, and are also more common among intravenous drug users (5). Staphylococcus aureus is the most commonly isolated microorganism in patients with SCJ septic arthritis. Methicillin-resistant Staphylococcus aureus (MRSA) is responsible for a significant proportion of septic arthritis cases, accounting for 6% to 22% of Staphylococcus aureus (S. aureus) isolates (6). In our case, we present an uncommon origin of MRSA infection associated with extensive inflammation of the SCJ. We present this article in accordance with the CARE reporting checklist (available at https://acr.amegroups.com/article/view/10.21037/acr-2025-311/rc).

Case presentation

All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Declaration of Helsinki and its subsequent amendments. Written informed consent was obtained from the patient for publication of this case report and any accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Our case report presents a 52-year-old male patient with hypertension, hypercholesterolemia, type 2 diabetes mellitus, coronary artery disease, and above-knee amputation of his right leg in his medical history. The patient had long-standing type 2 diabetes mellitus with poor glycemic control. Glycated hemoglobin (HbA1c) was 9.8% at presentation, indicating chronic hyperglycemia. Pharmacologic therapy included acarbose (Synhydrate) 160 mg per day, dapagliflozin 10 mg once daily (Forxiga), metformin 500 mg twice daily, and gliquidone (Glurenorm) one tablet twice daily. The HbA1c levels measured 5, 4, and 3 months before surgery were 6.0%, 8.8%, and 9.8%, respectively.

The patient had evidence of diabetes-related complications, including peripheral vascular disease, which had previously necessitated right above-knee amputation two years earlier. The stump had been chronically non-healing for more than eight months despite local wound care.

The patient presented to the emergency department, stating that the crutch he was leaning on had caused a wound on the inner side of the right arm. The skin above the right SCJ and on the left side of the neck had slight redness, but no tenderness or swelling was observed (Figure 1). The wound in his arm seemed to be more likely an abscess, and a general surgeon incised and probed the tract. Since it was found to be very long and directed toward the chest wall, the patient was sent to a head and neck and chest computed tomography (CT). The examination confirmed an extensive soft tissue abscess from the upper part of the right arm to the right SCJ, which continues to the lower left part of the neck. Osteomyelitis of the right sternoclavicular and first sternocostal joints was also confirmed, with destruction of the bones (Video 1), Contrast-enhanced CT imaging demonstrated no evidence of internal jugular or subclavian vein thrombosis .The laboratory markers showed a slight elevation of the white blood cell (WBC) 10.94 G/L, notably among neutrophil, extreme elevation of C-reactive protein (CRP) 231.1 mg/L, and a decrease in hemoglobin level 4.6 mmol/L. The culture taken from the abscess by the surgeon confirmed MRSA infection.

Figure 1 Patient with a wound on his right arm and slight redness on the skin above the right SCJ and on the left side of the neck. SCJ, sternoclavicular joint.

In our department, we found a largely exudating, plaque-covered, non-healing amputated stump in the patient, from which further cultures were taken. Blood cultures were obtained on admission, which were MRSA positive. After a positive blood culture, we asked for transesophageal echocardiography, which showed no evidence of infective endocarditis.

In consultation with the diabetologist, the patient’s antihyperglycemic regimen was adjusted during the acute septic episode and perioperative period. Oral agents (metformin, gliquidone, acarbose) and the SGLT2 inhibitor (dapagliflozin) were withheld, and glycemic control was achieved using a subcutaneous basal-bolus insulin regimen targeting 7.8–10.0 mmol/L (140–180 mg/dL). Given chronic kidney disease and risk of hypoglycemia, insulin was initiated conservatively at a total daily dose of approximately 0.2–0.3 units/kg/day (about 50% as basal insulin glargine once daily and 50% as rapid-acting insulin divided before meals), with correctional insulin and daily titration based on bedside capillary glucose measurements; prandial insulin was held when the patient was nil per os.

“The patient was informed about the suspected infectious source and treatment strategy and expressed understanding of the prolonged course of therapy and surgical management.”

After evaluation of the case, we decided to perform surgical debridement of the affected joints and the nearby regions. During the procedure, a curved incision was made from the left side of the neck, over the right SCJ toward the abscess on the arm. The inflamed soft tissues were excised in these areas. This was followed by resection of the proximal part of the clavicle, the proximal part of the first rib, and the articular portion of the sternum, all of which were eroded by the inflammatory process. The retrosternal mediastinal region was explored; however, the infection had not extended deeply into this area. On the right side, a tunnel extending toward the arm, but did not reach the shoulder joint, and the joint capsule was not opened. The tunnel bifurcated laterally: one branch exited through the skin of the arm, while the other extended behind the brachial plexus. Both pathways were opened and explored. Multiple irrigations were performed using hydrogen peroxide and Betadine solution. At the end of the surgery, we applied vacuum-assisted closure (VAC) therapy to facilitate the wound cleaning and encourage the growth of new tissue (Figure 2).

Figure 2 VAC therapy to facilitate the wound cleaning and encourage the growth of new tissue. VAC, vacuum-assisted closure.

Since MRSA was also cultured from the amputation stump, we considered this chronic wound as the primary source of the infection. Under regular VAC sponge, the wound developed healthy granulation tissue (Figure 3). The wound care of the stump, with proper management, developed healthy granulation tissue. After completing a course of Vancomycin, MRSA was no longer detectable from either wound site, and we took blood culture again, and due to antibiotic treatment, the result was negative. Because the patient had chronic renal failure, we closely monitored the kidney function markers and gave the patient proper treatment, besides applying vancomycin for septic arthritis treatment. During the therapy, inflammatory markers gradually decreased in laboratory tests with 7.63 G/L WBC and 28.1 mg/L CRP marker. Due to clinical improvement, the abscess cavity wound was closed by secondary suture over two Redon drains. Once the output from the Redons drain diminished, both were removed, and finally the wound healed after two weeks from the closure (Figure 4). The chronological course of the patient’s presentation, diagnosis, treatment, and recovery is summarized in Table 1.

Figure 3 Under a regular VAC sponge, the wound developed healthy granulation tissue. VAC, vacuum-assisted closure.

Figure 4 With continued dressing changes, the wound gradually contracted and healed per primam.

Discussion

Diagnosis challenges in case of SCJ infections

The diagnosis of SCJ infections is frequently postponed because of their low frequency and ambiguous presentation. As a result, the infection spreads to the surrounding tissues (7). Local complications or distant septic metastases occur in around one-third of individuals with S. aureus bloodstream infection (8). The bones and joints (particularly in the presence of prosthetic materials), the epidural space and intervertebral discs, and both native and prosthetic heart valves are common locations for distant metastases; for this reason, transesophageal echocardiography is important to rule out infective endocarditis. Patients may also develop kidney and splenic visceral abscesses (9).

It may manifest as a rash in the primary care context or as arm pain radiating from the chest (10). Further frequent symptoms are fever, joint swelling, warmth, and immobility. A butterfly rash on the chest may be the first sign of bilateral infections. The literature has also documented certain uncommon manifestations, such as pressure-like chest pain that radiates to the shoulder or neck, which pain pattern may be mistaken for a myocardial infarction. Vocal cord palsy, dysphagia, cervical esophageal rupture, lower respiratory infection, breast abscess, and subclavian compression syndrome are other uncommon manifestations (11). Although it is an uncommon manifestation of the SCJ infection, it underscores the importance of examining potential atypical and distal sources.

Identification and management of sources of infection

A chronically infected amputation stump as a source of SCJ infection is rarely reported and is considered uncommon. Identifying the amputated leg as the origin of hematogenous spread and exclusion of other possibilities was one of the important aspects of a successful treatment. Eliminating and preventing recurrence of the local infection requires localized therapy parallel with the treatment of the SCJ infection.

After amputation, surgical site infections are frequent and can have detrimental consequences on healing, phantom pain, and the time it takes to get a prosthetic fitting, in addition to raising patient morbidity. Diabetes mellitus, advanced age, and smoking are risk factors for amputation infection and are prevalent among amputees (12). Hematogenous spread from a chronically infected amputated foot is a rare but serious consequence that is highlighted in our case. Staphylococcus aureus acquired systemic access as a result of impaired immunity (diabetes, vascular disease), settling in the SCJ, a well-known but rare location for hematogenous seeding (13). Once established, infection’s complications can be jugular vein thrombosis, osteomyelitis, joint damage, extension to the mediastinum, and potentially fatal septicemia (14).

The diagnosis methods

The diagnosis is based on laboratory and imaging. Laboratory workup includes complete blood count, erythrocyte sedimentation rate (ESR), CRP, rheumatoid factor, antinuclear antibody, and human leukocyte antigen B27, and usage of sampling for the type of the bacteria of the suspected site of SCJ infection. The laboratory profile demonstrated variable ranges across the studied parameters. WBC count was found to range between 4,330 and 20,250 cells/µL, with a mean of 12,248 cells/µL; a diagnostic sensitivity of 90% was noted when values exceeded 101,000 cells/µL. The ESR ranged from 13 to 120 mm/h, with a mean value of 66.2 mm/h, showing a sensitivity of 95% for values greater than 30 mm/h. CRP levels varied between 1.2 and 28.9 mg/dL, with a mean concentration of 11.8 mg/dL, and demonstrated a sensitivity of 77% when levels exceeded 100 mg/dL (15).

Generally, a chest X-ray is the initial diagnostic procedure. Soft tissue shadow broadening and joint space distension may be observed. Soft tissue edema often takes 10 to 12 days to show up on a standard X-ray. Bony destruction and demineralization typically occur considerably later. If more soft tissue information is required, diagnostic workups include imaging such as CT and magnetic resonance imaging (MRI). The accumulation of inflammatory substances causes the joint space to enlarge. This larger diameter contrasts with the narrowing of the joint space caused by the loss of cushioning between bones in conventional osteoarthritis and joint deterioration. An infection is more likely if the average joint distention is 14 mm (range: 10–20 mm). Degeneration is more likely to occur if the distension is 5 mm (range: 3–8 mm). Nevertheless, by the second week of symptoms, only 20% of osteomyelitis cases had abnormal radiographic results (16).

The role of surgical radical debridement and VAC therapy

The example highlights how important early, thorough surgical debridement is for joint infections connected to MRSA. More mediastinal extension and vascular problems were avoided by resecting the affected soft tissues and bones (clavicle, sternum margins, and adjacent ribs). VAC therapy was essential for enabling wound granulation, managing exudate, and lowering the bacterial burden. Additionally, it ensured infection control while permitting phased wound closure.

Multidisciplinary care management

Taking care of to prevent complications such as osteomyelitis, chest wall abscess, and mediastinitis, early diagnosis and timely treatment are essential (17), and we consulted closely with our infectious disease colleagues as a multidisciplinary team. Management entails starting empirical antibiotic therapy against Streptococcus species and Staphylococcus aureus, with treatment customized according to microbiological findings and clinical response. Drainage or debridement is necessary for septic arthritis brought on by MRSA, and antibiotics must be taken for three to four weeks. There is little data to support the selection or course of antibiotic treatment for septic arthritis, and no randomized studies have been conducted as far as we are aware. No therapy regimen was shown to be superior to another for native joint infection in a comprehensive meta-analysis of antibiotic treatment for joint sepsis. According to consensus, the cornerstones of treatment should be the timely evacuation of any purulent material and the use of the proper antibiotics (18). Intravenous vancomycin and daptomycin are parenteral choices, and trimethoprim/sulfamethoxazole with rifampin, linezolid, and clindamycin are oral and parenteral options (19).

Vancomycin was selected as definitive therapy because the infection was culture-confirmed MRSA and involved native sternoclavicular/first sternocostal joint septic arthritis with osteomyelitis, for which intravenous vancomycin remains a standard first-line agent in widely cited MRSA guidance (20-24). In our patient, management also emphasized source control: radical resection of infected bone and extensive debridement of involved soft tissues, followed by VAC therapy, which likely reduced bacterial burden and any sessile/biofilm-like bacterial populations.

Prolonged Vancomycin therapy effectively eradicated MRSA, as confirmed by negative follow-up cultures from both infected sites and negative blood culture. Therapy was adjusted based on clinical progress and microbiological results.

Role of uncontrolled diabetes mellitus in disease pathogenesis

Poorly controlled diabetes mellitus is a well-established risk factor for invasive Staphylococcus aureus infections, including septic arthritis. Chronic hyperglycemia impairs neutrophil chemotaxis, phagocytosis, and intracellular killing, while diabetes-associated microangiopathy compromises tissue perfusion and antibiotic penetration. These mechanisms collectively promote persistent infection, bacteremia, and metastatic seeding of distant joints.

In the present case, long-standing poor glycemic control likely contributed to the chronic non-healing amputation stump, which served as a sustained infectious reservoir. Although transient bacteremia was not microbiologically documented, the identical MRSA strain isolated from both the stump and sternoclavicular abscess strongly supports hematogenous dissemination. Diabetes has been repeatedly identified as one of the most common comorbidities in SCJ septic arthritis, particularly in cases complicated by osteomyelitis and extensive soft-tissue involvement (25).

With the help of a diabetologist, the optimization of glycemic control was therefore considered an essential component of multidisciplinary management, alongside surgical source control and targeted antimicrobial therapy.

For the management of diabetes, close collaboration was maintained with a diabetologist to improve glycemic control and reduce the HbA1c level.

This case required collaboration between thoracic surgeons, infectious disease specialists, diabetologist and nephrologists due to the complex infection, risk of mediastinitis, and potentially kidney injury caused by antibiotic therapy and inflammatory burden.

Conclusions

We describe a rare case of extensive MRSA-positive SCJ septic arthritis in a patient with multiple comorbidities and a history of lower limb amputation. The infection originated hematogenously from a chronically infected, non-healing amputation stump, an uncommon transmission route for SCJ infections. This case highlights the need for early recognition of atypical sources, aggressive surgical management, targeted antimicrobial therapy, and multidisciplinary care to prevent life-threatening complications.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the CARE reporting checklist. Available at https://acr.amegroups.com/article/view/10.21037/acr-2025-311/rc

Peer Review File: Available at https://acr.amegroups.com/article/view/10.21037/acr-2025-311/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://acr.amegroups.com/article/view/10.21037/acr-2025-311/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Declaration of Helsinki and its subsequent amendments. Written informed consent was obtained from the patient for publication of this case report and any accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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