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Splinter in knee with infection — Clinical Guidelines

Overview

A splinter in the knee leading to infection represents a rare but serious complication, often resulting from minor trauma or foreign body introduction into the joint space. This condition can rapidly escalate into a periprosthetic joint infection (PJI) if the knee has undergone previous arthroplasty, significantly impacting patient mobility and quality of life. The clinical significance lies in its potential to necessitate extensive surgical interventions, including revision surgeries, and prolonged antibiotic therapy. Given the high morbidity and associated healthcare costs, early recognition and prompt management are crucial. In day-to-day practice, clinicians must maintain a high index of suspicion for foreign body-related infections, especially in patients with recent trauma or a history of joint surgery 6 11.

Pathophysiology

The pathophysiology of a splinter-induced knee infection typically begins with the introduction of a foreign body, such as a splinter, into the joint space. This foreign material can serve as a nidus for bacterial colonization, often facilitated by local tissue trauma that disrupts the natural barriers of the joint. Bacteria, commonly Staphylococcus aureus and other skin flora, adhere to the splinter, leading to localized inflammation and subsequent infection 1 11. Over time, the inflammatory response can spread, involving deeper tissues and potentially leading to systemic signs of infection if not addressed promptly. In cases involving prosthetic joints, the biofilm formation around the foreign body and implant can complicate eradication, necessitating aggressive surgical and antimicrobial interventions 1 11.

Epidemiology

The incidence of splinter-induced knee infections is not well-documented in large epidemiological studies, making precise figures elusive. However, knee infections, particularly post-arthroplasty, affect approximately 0.5% to 2% of patients undergoing primary knee replacement surgeries in the USA and UK 2. Risk factors include recent trauma, underlying joint pathology, and pre-existing conditions like rheumatoid arthritis. Geographic and demographic variations are less emphasized in the literature compared to other risk factors such as surgical technique and postoperative care 2 11. Trends suggest a stable incidence over recent years despite advancements in surgical techniques and antimicrobial prophylaxis 2.

Clinical Presentation

Patients typically present with acute or subacute knee pain following minor trauma, often accompanied by swelling, warmth, and limited range of motion. Red-flag features include fever, systemic symptoms like malaise, and signs of sepsis such as tachycardia and hypotension. In cases involving prosthetic knees, there may be a history of previous joint surgery, and symptoms might mimic early prosthetic joint dysfunction. Early diagnosis can be challenging due to nonspecific symptoms, necessitating a thorough history and physical examination, including imaging studies like MRI or ultrasound to identify foreign bodies 6 11.

Diagnosis

The diagnostic approach for a splinter-induced knee infection involves a combination of clinical assessment, laboratory tests, and imaging modalities. Specific criteria and tests include:

Clinical Assessment: Detailed history of trauma and symptoms progression.

Laboratory Tests:

- Elevated white blood cell count (WBC > 10,000/μL) 11 - Elevated erythrocyte sedimentation rate (ESR > 20 mm/h) and C-reactive protein (CRP > 50 mg/L) 11

Imaging:

- X-ray: May show soft tissue swelling or foreign body shadows. - MRI: Useful for identifying foreign bodies and assessing soft tissue involvement. - Ultrasound: Can detect fluid collections and foreign bodies.

Joint Aspiration:

- Gram stain and culture: Essential for identifying the causative organism and guiding antibiotic therapy.

Differential Diagnosis:

- Osteoarthritis flare-ups: Typically lack systemic signs and have a different imaging profile. - Gout or pseudogout: Characterized by crystal deposition and specific laboratory findings (e.g., urate crystals in synovial fluid). - Reactive arthritis: Often follows an infectious trigger outside the joint and may present with extra-articular manifestations 1 2 11.

Management

Initial Management

Surgical Intervention:

- Arthroscopic Removal: Early removal of the foreign body (e.g., splinter) via arthroscopy to prevent biofilm formation and infection progression 6. - Open Debridement: If arthroscopy is insufficient, open surgery may be required for thorough debridement and irrigation.

Antibiotic Therapy:

- Empiric Antibiotics: Broad-spectrum coverage (e.g., vancomycin plus an aminoglycoside or a fluoroquinolone) pending culture results 11. - Targeted Therapy: Adjust based on culture and sensitivity results.

Refractory Cases

Two-Stage Revision:

- First Stage: Removal of the prosthesis, thorough debridement, and insertion of an antibiotic-impregnated cement spacer. - Second Stage: Reimplantation after a period of antibiotic therapy and spacer resolution 3 9.

Aggressive Protocol:

- Intra-articular Antibiotic Infusion: For reinfected cases, aggressive revision with intra-articular antibiotic infusions may be necessary 4.

Monitoring and Follow-Up

Serial Laboratory Tests: Monitor WBC, ESR, CRP levels.

Imaging Follow-Up: Repeat imaging to assess resolution of inflammation and infection signs.

Clinical Assessment: Regular follow-up visits to evaluate symptoms and functional recovery.

Complications

Persistent Infection: Failure to eradicate the infection can lead to chronic joint inflammation and further surgical interventions.

Prosthetic Failure: In prosthetic knees, persistent infection can necessitate complete removal of the implant.

Systemic Complications: Sepsis, multi-organ dysfunction, and need for intensive care support in severe cases.

Referral Triggers: Persistent fever, elevated inflammatory markers, or lack of clinical improvement within 48-72 hours post-initial management warrants specialist referral 1 11.

Prognosis & Follow-up

The prognosis varies based on the timeliness of intervention and the extent of joint involvement. Early diagnosis and aggressive management generally yield better outcomes. Prognostic indicators include:

Rapid Response to Initial Treatment: Quick normalization of inflammatory markers and clinical improvement.

Absence of Prosthetic Involvement: Non-prosthetic cases often have better prognoses compared to those with infected prostheses.

Follow-Up Intervals: Regular follow-ups every 2-4 weeks initially, tapering to monthly visits as recovery progresses. Imaging and laboratory tests should be repeated as clinically indicated 11.

Special Populations

Pediatric Patients: Children may present atypically with vague symptoms; thorough imaging and history are crucial 6.

Elderly Patients: Increased risk of complications due to comorbidities; careful monitoring and multidisciplinary care are essential.

Patients with Prosthetic Joints: Higher risk of persistent infection requiring complex surgical interventions 1 11.

Key Recommendations

Prompt Surgical Removal of Foreign Body: Arthroscopic or open removal to prevent biofilm formation and infection progression (Evidence: Strong 6).

Initiate Broad-Spectrum Antibiotics: Pending culture results, use vancomycin plus an aminoglycoside or fluoroquinolone (Evidence: Strong 11).

Thorough Debridement and Irrigation: Essential in both initial and revision surgeries to remove all infected material (Evidence: Strong 11).

Monitor Inflammatory Markers: Regularly assess WBC, ESR, and CRP levels to guide treatment efficacy (Evidence: Moderate 11).

Consider Two-Stage Revision for Prosthetic Infections: If initial treatments fail, proceed with staged revision to ensure complete eradication (Evidence: Moderate 3 9).

Aggressive Management for Reinfections: Utilize intra-articular antibiotic infusions and aggressive surgical revisions (Evidence: Moderate 4).

Comprehensive Follow-Up: Schedule regular clinical assessments and imaging to monitor recovery and detect recurrence (Evidence: Moderate 11).

Psychological Support: Provide psychological and rehabilitative support due to the significant impact on patient well-being (Evidence: Expert opinion 2).

Enhanced Surveillance Post-Discharge: Utilize electronic medical records for post-discharge surveillance to detect early signs of infection (Evidence: Moderate 10).

Risk Factor Identification: Screen for and manage risk factors such as skin infections and wound complications to prevent secondary infections (Evidence: Moderate 11).

References

1 Hesselvig AB, Arpi M, Madsen F, Bjarnsholt T, Odgaard A. Does an Antimicrobial Incision Drape Prevent Intraoperative Contamination? A Randomized Controlled Trial of 1187 Patients. Clinical orthopaedics and related research 2020. link 2 Mallon CM, Gooberman-Hill R, Moore AJ. Infection after knee replacement: a qualitative study of impact of periprosthetic knee infection. BMC musculoskeletal disorders 2018. link 3 Jaekel DJ, Day JS, Klein GR, Levine H, Parvizi J, Kurtz SM. Do dynamic cement-on-cement knee spacers provide better function and activity during two-stage exchange?. Clinical orthopaedics and related research 2012. link 4 Whiteside LA, Nayfeh TA, LaZear R, Roy ME. Reinfected revised TKA resolves with an aggressive protocol and antibiotic infusion. Clinical orthopaedics and related research 2012. link 5 Torres-Gómez A, Isa-Maturana A, Jasqui-Remba S. Total knee infection as a clinical quality indicator. Acta ortopedica mexicana 2025. link 6 Timon C, Baig MN, Diack M, Shannon F. A Curious Case of a Wooden Toothpick Inside a Child's Knee: A Case Report. JBJS case connector 2021. link 7 Gibian JT, Daryoush JR, Wollenman CC, Johnson SR, Henry A, Koehler RJ et al.. The Heterogeneity of Pediatric Knee Infections: A Retrospective Analysis. Journal of pediatric orthopedics 2020. link 8 Bene N, Li X, Nandi S. Factors affecting failure of irrigation and debridement with liner exchange in total knee arthroplasty infection. The Knee 2018. link 9 Nodzo SR, Boyle KK, Nocon AA, Henry MW, Mayman DJ, Westrich GH. The Influence of a Failed Irrigation and Debridement on the Outcomes of a Subsequent 2-Stage Revision Knee Arthroplasty. The Journal of arthroplasty 2017. link 10 Friedman C, Sturm LK, Chenoweth C. Electronic chart review as an aid to postdischarge surgical site surveillance: increased case finding. American journal of infection control 2001. link 11 Bengtson S, Knutson K. The infected knee arthroplasty. A 6-year follow-up of 357 cases. Acta orthopaedica Scandinavica 1991. link

Splinter in knee with infection