Sternoclavicular Joint Infection Caused by Staphylococcus capitis

Summary

Here, we present a case of a right sternoclavicular joint infection with osteomyelitis due to Staphylococcus capitis. The patient underwent surgical debridement and drainage followed by 10 weeks of antibiotics, resulting in complete symptom resolution and satisfactory wound healing.

Abstract

A 74-year-old female patient presented with "palpitations and chest tightness for half a day." The symptoms developed suddenly while riding an elevator, accompanied by shortness of breath, but without dizziness or chest pain. The patient had a 5-year history of diabetes, managed with metformin. She had undergone a right mastectomy 20 years ago for breast cancer. On admission, her vital signs were stable. Physical examination revealed a tender, swollen mass in the right side of the neck, soft in texture, with purulent drainage. Blood tests showed an elevated C-reactive protein (CRP) level (51.47 mg/L). Imaging studies (computed tomography [CT], ultrasound, magnetic resonance imaging [MRI]) revealed a soft tissue mass in the right clavicular region, with possible osteomyelitis. The patient was diagnosed with a right-sided sternoclavicular joint skin infection complicated by osteomyelitis.

Surgical debridement and drainage were performed, and pathological examination confirmed a Staphylococcus capitis infection. The patient was treated with a 10-week course of antibiotics, initially with intravenous ertapenem, later switched to oral linezolid. Throughout the treatment, no adverse drug reactions were observed. One month later, follow-up observations indicate that the patient's surgical wound is healing well. The patient's symptoms significantly improved, with complete resolution of palpitations, chest tightness, and shortness of breath. The treatment was well-tolerated. This case report aims to raise clinicians' awareness of sternoclavicular joint infections caused by Staphylococcus capitis and to highlight the importance of early diagnosis and individualized treatment strategies.

Introduction

Sternoclavicular joint infection (SCJI) is a rare form of septic arthritis, accounting for less than 1% of all infectious arthritis cases^1,2. Despite its low incidence, SCJI can lead to serious complications such as mediastinitis, chest wall abscess, and pulmonary empyema^2,3,4. Staphylococcus capitis, a coagulase-negative staphylococcus (CoNS) and a common commensal organism of human skin, has been increasingly implicated in catheter-related bloodstream infections, prosthetic joint infections, and wound infections^5,6,7. However, SCJI caused by Staphylococcus capitis has been rarely reported in the literature⁸. Common risk factors for SCJI include diabetes mellitus, immunosuppression, and a history of intravenous drug use^2,9,10. Nonetheless, cases have also been reported in healthy individuals without underlying conditions^11,12,13. While Staphylococcus capitis is generally regarded as a benign skin colonizer, it can act as an opportunistic pathogen under specific conditions⁵.

This case report describes a sternoclavicular joint infection caused by Staphylococcus capitis in a patient who presented primarily with chest tightness and palpitations. The diagnosis was ultimately established through imaging studies and microbiological examinations, confirming a Staphylococcus capitis–associated sternoclavicular joint infection. The patient underwent surgical debridement followed by a total of 10 weeks of antibiotic therapy, resulting in complete resolution of the infection. This case is clinically relevant and appropriate for reporting because it involves a typical high-risk population (elderly, diabetic, and history of malignancy) with an atypical initial presentation, thereby filling a key knowledge gap regarding S. capitis-induced SCJI. This report aims to increase clinicians' awareness of sternoclavicular joint infections caused by Staphylococcus capitis and highlights the importance of early diagnosis and individualized treatment strategies^14,15,16.

CASE PRESENTATION:

A 74-year-old female patient presented to the First Affiliated Hospital of Zhejiang University with a chief complaint of palpitations and chest tightness that had persisted for half a day. The symptoms began suddenly while the patient was riding an elevator, characterized by palpitations, chest oppression, and shortness of breath. She denied dizziness, blurred vision, chest pain, or other discomfort. The patient had a 5-year history of type 2 diabetes, managed with metformin (two tablets daily), and a history of right-sided breast cancer, for which she underwent a radical mastectomy 20 years ago.

Upon admission, physical examination revealed the following: Temperature: 37.2 °C; Pulse: 78 beats/min; Respiratory rate: 19 breaths/min; Blood pressure: 128/79 mmHg. The patient was alert, oriented, and had a normal mental status. A reddish-purple mass, approximately 2 cm in diameter, was observed at the right sternoclavicular joint. The mass was soft, with localized skin warmth and purulent bloody discharge. No jaundice was noted in the skin or sclera. Pupils were equal and reactive to light. Lung auscultation was clear without rales, and the heart rhythm was regular with no pathological murmurs. The abdomen was soft, non-tender, and without rebound pain. No lower limb edema was observed, and muscle strength and tone were normal in all extremities, with no movement limitation.

Laboratory Investigations showed the following: white blood cells (WBC): 6.43 × 10⁹/L; Neutrophils: 67.8%; C-reactive protein (CRP): 51.47 mg/L (normal < 6.00 mg/L); electrocardiogram (ECG): Supraventricular tachycardia (heart rate > 200 beats/min); Mycobacterium tuberculosis PCR polymerase chain reaction (PCR) assay of infected tissue: Negative.

Abdominal CT scan showed no acute abdominal pathology. Ultrasound revealed a mixed cystic-solid mass in the right subclavicular region, suggestive of inflammation. The MRI of the chest wall (3.0 T) showed an occupying lesion at the anterior edge of the right proximal clavicle and sternoclavicular joint, with recommended contrast-enhanced imaging. Inflammatory exudates were observed in the right chest wall, upper arm subcutaneous tissues, and fascial planes. Enlarged lymph nodes were noted in the left axilla and mediastinum. A preliminary diagnosis of skin infection involving the right sternoclavicular joint was made, and the patient was admitted for further treatment.

The patient received preoperative intravenous ertapenem (1.0 g/day) and surgical debridement of the infected lesion was performed. Intraoperatively, two purulent abscesses were identified at the right sternoclavicular joint, along with localized purulent sinus tracts and necrosis of both the fascia and bone. Intraoperative observation confirmed that the stability of the sternoclavicular joint was preserved and not compromised by infection or debridement. The procedure involved excising necrotic tissue, debriding osteomyelitic and necrotic fascia, and inflammatory subcutaneous tissue. The wound was irrigated, and hemostasis was achieved. The flap was closed, and two negative-pressure drainage tubes were placed.

Postoperative diagnosis confirmed clavicular osteomyelitis. The pus drainage was sent for culture and bacterial identification, which revealed Staphylococcus capitis, sensitive to ertapenem. The patient continued on ertapenem (1.0 g IV daily) and received supportive treatments, including pain management, gastric protection, and nutritional support. Inflammatory markers decreased rapidly postoperatively, with CRP levels dropping from 51.47 mg/L to 17.38 mg/L within 4 weeks.

The patient successfully completed a 10-week course of antibiotic therapy, consisting of 2 weeks of intravenous ertapenem, followed by 8 weeks of oral linezolid. No adverse drug reactions or complications were noted during the treatment. At 1-month follow-up, the wound had healed well, and the patient's symptoms had significantly improved, with complete resolution of palpitations, chest tightness, and dyspnea.

Diagnosis, Assessment, and Plan:

The patient was diagnosed with a rare primary sternoclavicular joint infection complicated by osteomyelitis, initially suspected clinically and radiologically as a bacterial pyogenic infection. Surgical exploration confirmed purulent material, necrotic soft tissue, and osteomyelitis involving the medial clavicle. The patient is an elderly female with multiple risk factors, including long‑standing diabetes and a history of malignant tumor, which predisposed her to opportunistic infection. Clinical presentation was atypical, with chest tightness and palpitations as chief complaints, while local inflammatory signs and elevated inflammatory markers supported an active infectious process. Imaging confirmed deep soft tissue and bone involvement, and microbiological culture identified Staphylococcus capitis as the causative pathogen. The treatment plan included urgent surgical debridement of necrotic bone and soft tissue, targeted antibiotic therapy based on culture results, and soft tissue reconstruction with a pedicled myofascial flap to achieve durable wound closure. Antibiotic therapy consisted of 2 weeks of intravenous ertapenem followed by 8 weeks of oral linezolid, with close monitoring of inflammatory markers and wound healing. Postoperative follow‑up was scheduled to assess healing, infection resolution, and potential recurrence. Long‑term management includes regular outpatient review, wound care education, and instruction regarding warning signs of recurrent infection.

Protocol

This surgical procedure has been approved by the hospital's ethics committee and conducted in accordance with the ethical guidelines provided. Informed consent was obtained from all individual participants involved in the study.

1. Initial evaluation and sample collection

1. Comprehensive skin examination
   1. Conduct a thorough inspection of the affected skin area, paying particular attention to the presence of erythema, swelling, tissue necrosis, and purulent exudation.
      ​NOTE: Capture baseline visual documentation (e.g., photographs and lesion dimensions) and record initial clinical manifestations, including erythema and edema.
2. Medical history and comorbidities
   1. Obtain a detailed medical history, documenting prior medical conditions, current and previous medications used for symptom management, surgical history, and any associated complications.
3. Wound exudate collection
   1. Collect wound exudate using a sterile swab. Gently rotate the swab for no less than 5 s while sampling the ulcer base and margins. Immediately place the swab into Amies transport medium and store at 4 °C.
   2. Inspect the swab visually to confirm sufficient exudate collection; if the sample is inadequate, repeat the collection procedure without delay.
      ​NOTE: Transport samples to the microbiology laboratory within 2 h. If immediate processing is not feasible, store samples under refrigerated conditions and process them within 24 h.

2. Imaging and empirical treatment

1. Imaging studies
   1. Perform magnetic resonance imaging (3.0T MRI) using T1-weighted, T2-weighted, and contrast-enhanced fat-suppressed sequences to evaluate soft tissue involvement and assess potential bone extension.
      ​NOTE: Verify the presence of deep soft tissue fluid accumulation or abscess formation on imaging studies.
2. Empirical antibiotic therapy
   1. Initiate empirical antibiotic treatment by administering 1 g of ertapenem intravenously, diluted in 100 mL of normal saline and infused once daily over 30 min.
      ​NOTE: Modify the antibiotic regimen according to local antimicrobial susceptibility patterns and culture results.

3. Surgical debridement procedures

1. Preoperative preparation
   1. Perform the procedure under general endotracheal anesthesia to ensure adequate muscle relaxation, stable hemodynamics, and patient immobility during debridement and flap reconstruction.
      NOTE: The anesthesiologist maintained an appropriate depth of anesthesia and closely monitored respiratory and circulatory functions throughout the operation.
   2. Place the patient in the supine position with adequate exposure of the sternoclavicular joint, the medial segment of the clavicle, and the anterior chest wall. Perform routine skin disinfection using povidone‑iodine, followed by sterile draping to establish a standard surgical field.
   3. Perform routine monitoring continuously during the operation, including heart rate, noninvasive blood pressure, electrocardiography, pulse oximetry, and end‑tidal carbon dioxide partial pressure.
2. Debridement
   1. Under sterile operating room conditions, remove visibly infected or necrotic tissue using a scalpel in combination with bipolar electrocautery set to 30–40 W. Curette and resect the infected lesion involving the medial 2 cm segment of the clavicle until all devitalized bone is removed.
   2. Continue debridement until all nonviable tissue has been excised and healthy, bleeding tissue is clearly visible.
3. Pedicled myofascial flap surgery
   1. Perform pedicled myofascial flap reconstruction under standard operating room sterile conditions with sterile gloves, gown, mask, and a dedicated sterile field, using the sternocostal portion of the pectoralis major muscle as the donor muscle for the pedicled myocutaneous flap.
   2. Carry out the dissection superficially to the clavipectoral fascia while preserving the thoracoacromial artery and vein as the vascular pedicle to ensure sufficient blood supply. Then, rotate the flap medially to achieve tension‑free coverage of the sternoclavicular joint defect after debridement.
4. Tissue sample collection
   1. Harvest a minimum of three tissue specimens from anatomically distinct sites, including the ulcer base, ulcer margin, and deep tissue layers.
   2. Place each specimen into individually labeled sterile containers for subsequent microbiological culture and histopathological evaluation.
      NOTE: Confirm that tissue samples accurately represent different regions, including viable margins, necrotic tissue, and deep subcutaneous structures.
5. Monitoring debridement progress
   1. Monitor and document wound characteristics, including incision healing status and the volume and nature of drainage, along with trends in inflammatory markers such as CRP (<10 mg/L) and white blood cell count (<10 × 10⁹/L).

4. Pathogen identification

1. Staining and microscopic examination
   1. Use infected soft tissue and devitalized bone tissue obtained intraoperatively for staining. Process the tissue specimens as follows: fix in 10% neutral buffered formalin, embed in paraffin, and cut into serial sections at 4 µm thickness. Then, deparaffinize the sections with xylene and rehydrate through graded ethanol (100% > 95% > 75%) to complete pre-staining preparation.
   2. Perform Gram staining.
      1. Apply crystal violet for 60 s, followed by rinsing with sterile saline. Then add Gram iodine for 60 s and rinse thoroughly.
      2. Perform decolorization for 1–2 s until no purple dye elutes, followed by immediate rinsing with saline. Finally, apply safranin for 60 s; rinse the sections and air-dry to finish Gram staining.
   3. Perform Gomori methenamine silver (GMS) staining.
      1. Incubate the tissue sections that had undergone the aforementioned pretreatment (deparaffinization and rehydration) in GMS working solution (prepared by mixing methenamine silver stock solution and citrate buffer at a 1:1 ratio) at room temperature for 30 min.
      2. Then, wash the sections three times with sterile saline to remove unbound stain. Next, apply 0.5% gold chloride solution for 30 s for differentiation.
      3. After rinsing, use 5% sodium thiosulfate solution for 1 min to terminate the staining reaction. Finally, rinse the sections thoroughly with distilled water and air-dry to complete GMS staining.
      4. After staining is completed, observe the sections under a light microscope at 200× magnification. Record morphological features of positively stained regions to ensure accurate identification of infection-related lesions.
         ​NOTE: Fungal hyphae, spores, and pathogen distribution within the tissue were the main focus.

5. Antibiotic therapy

1. Antibiotic administration
   1. Administer ertapenem at a dose of 1 g intravenously in 100 mL of 0.9% saline, infused once daily over 30 min.
   2. Monitor serum CRP and procalcitonin levels every 3–7 days.
   3. Upon discharge, prescribe oral linezolid 600 mg twice daily for a duration of 8 weeks.
      ​NOTE: Confirm treatment effectiveness through radiological improvement (e.g., reduced inflammatory edema on MRI), normalization of inflammatory markers, and complete resolution of clinical signs of infection.

6. Recovery and follow-up

1. Outpatient follow-up
   1. Schedule outpatient follow-up visits at 1, 2, and 4 weeks after discharge, followed by monthly evaluations for a total duration of 6 months.
   2. Assess wound healing status, recurrence of infection, pain severity (using the visual analog scale [VAS]), and functional recovery (e.g., joint range of motion).
      ​NOTE: Document weekly wound healing progress, confirm complete epithelialization within the expected timeframe (<8 weeks), and evaluate adequacy of pain control (VAS ≤ 3).
2. Data recording and analysis
   1. Record wound appearance, drainage volume, inflammatory markers, and imaging findings at each follow‑up visit.
   2. Securely store anonymized patient data in a standardized case report form for subsequent analysis and publication.
      ​NOTE: Review final clinical outcomes on a monthly basis to confirm complete wound healing, absence of infection recurrence at the 6-month follow-up, and documentation of patient satisfaction and functional recovery.

7. Biohazard waste disposal

1. Discard the biohazard waste (tissue, swabs, sharp instruments) according to hospital biosafety regulations.

Results

A 74-year-old woman presented with a half-day history of sudden-onset palpitations, chest tightness, and shortness of breath, without dizziness or chest pain. She had a history of type 2 diabetes managed with metformin and prior breast cancer surgery. Physical examination revealed a ~2 cm red-purple, tender mass over the right sternoclavicular joint with localized warmth and purulent discharge. Electrocardiography showed supraventricular tachycardia (>200 beats/min). Imaging studies, including ultrasound and MRI, demo...

Discussion

Sternoclavicular Joint Infection (SCJI) is a relatively rare joint infection, but its incidence may be higher in certain populations. According to the literature, sternoclavicular joint infection can occur in various clinical contexts, including postoperative infections (such as extension of sternal osteomyelitis to the sternoclavicular joint after cardiac surgery)¹⁷, immunosuppressive states (such as after the use of immune checkpoint inhibitors)¹⁸, and primary bacterial o...

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Amies Transport Medium	Thermo Fisher	9805-200	Used for transporting wound exudate samples to the microbiology lab
Bipolar Electrocautery	Valleylab (Medtronic)	1190-0001	Used for excising necrotic or infected tissue during surgery
Crystal Violet (0.5% w/v)	Sigma-Aldrich	C-5810	Staining reagent for Gram staining
Ethanol (70%)	Sigma-Aldrich	E7023	Used for tissue dehydration and fixation in staining protocols
Faropenem (oral)	N/A	N/A	Antibiotic used in the second phase of treatment
Formalin (10%)	Sigma-Aldrich	F-1635	Used for tissue fixation before histopathological analysis
Grocott's Methenamine Silver Stain	Sigma-Aldrich	3953-000-5	Used for fungal identification in tissue samples
Proteinase K	Sigma-Aldrich	25560-039	Used in DNA extraction from tissue samples
Safranin (0.25% w/v)	Sigma-Aldrich	S8884	Counterstain used in Gram staining
T1-weighted MRI Sequence	Siemens Healthineers	NA	Imaging sequence for soft tissue assessment
T2-weighted MRI Sequence	Siemens Healthineers	NA	Imaging sequence for soft tissue and bone evaluation
VITEK System	BioMérieux	4112118	Automated system for bacterial identification