Pyogenic flexor tenosynovitis due to Kingella kingae in an infant
- 1 Orthopaedic Surgery, NYU Langone Health, New York, New York, USA
- 2 Orthopaedic Surgery, Naval Medical Center Portsmouth, Portsmouth, Virginia, USA
- 3 Orthopedic Surgery, US Naval Hospital Camp Pendleton, Camp Pendleton, California, USA
- Correspondence to Dr Conor Garry; conor.garry@nyulangone.org
Abstract
Pyogenic flexor tenosynovitis is relatively common but is seldom reported in young children. Kingella kingae is increasingly recognised as a causative agent. We report on an infant who presented with a palmar deep space infection and pyogenic flexor tenosynovitis caused by K. kingae. K. kingae is a fastidious, often culture-negative, organism which has been increasingly recognised as a cause of paediatric orthopaedic infections, including flexor tenosynovitis. Clinical suspicion should be heightened, and antibiotic coverage broadened in the setting of a positive physical examination and negative blood cultures.
Background
Pyogenic flexor tenosynovitis (PFT) is a closed-space infection of the synovial sheath surrounding the flexor tendon which comprises up to 10% of all hand infections.1 2 PFT can cause permanent structural and functional damage, with sequelae ranging from stiffness to amputation if not treated promptly.3 PFT in young children, particularly infants, is a rare occurrence.4 5 Kingella kingae has been increasingly identified as a cause of infection, including PFT, in the paediatric population.6 K. kingae is second only to Staphylococcus aureus as a cause of orthopaedic infections in children aged 6–36 months. It has been implicated in other paediatric infections including occult bacteraemia, respiratory tract infections, eye infections and endocarditis.5 7
Patients frequently report a penetrating injury prior to presenting with PFT, and direct inoculation is the most common mechanism of PFT infection. In children, direct inoculation can occur from such seemingly benign activity as thumb sucking.4 However, PFT can also develop from haematogenous seeding or contiguous spread from a nearby infection.1 2 8 9 Pathogens such as S. aureus and Streptococcus pyogenes are the most commonly identified organisms in PFT in adults, although following a bite injury, other pathogens such as Eikenella corrodens and Pasteurella multocida are common.1 2 9 10
PFT is classically diagnosed clinically in a patient demonstrating Kanavel’s signs: flexed finger posture, fusiform swelling, erythema and tenderness along the flexor tendon sheath.2 8 9 All except fusiform swelling were present in our patient. Symptoms usually present 2–5 days after contracting the bacteria, and fever is not uniformly present. White cell count and inflammatory markers may be normal or only mildly elevated.11 Plain radiographs are most often unremarkable. Ultrasound and MRI studies provide more detailed characterisation of the infection.5 Wound cultures are negative in roughly 20% of cases and therefore may be unreliable in guiding treatment.4 5
Case presentation
A healthy male infant presented with a 1-day history of worsening tenderness, erythema and swelling of his left long finger with no report of injury and intact skin. His medical history was significant only for a recently resolved upper respiratory tract infection leading to aphthous stomatitis or multiple benign oral ulcers. His examination was remarkable for tenderness, erythema and swelling of the left third digit as well as within the mid-palmar space. He was afebrile, and laboratory data revealed a normal white cell count of 8.0×103 cells/µL. He demonstrated elevated C reactive protein and erythrocyte sedimentation rate of 170 mg/L and 25 mm/hour, respectively. Hand radiographs were unremarkable. An ultasound performed in the emergency room demonstrated a small fluid collection in his mid-palmar space (see figure 1).
Long axis ultrasound of left palm demonstrating palmar fluid collection.
Investigations
He was admitted and started on intravenous clindamycin for empiric antibiotic coverage. Despite 24 hours of antibiotics, his examination worsened, and the erythema spread to his second and fourth digits as the third digit developed more fusiform swelling. His MRI (see figures 2 and 3) demonstrated findings consistent with tenosynovitis of the left third digit and fourth digit flexor tendons with overlying cellulitis and a small collection palmar to the middle finger flexor tendon sheath. With a clinical picture concerning for PFT of the third digit, the patient was taken urgently to the operating room for surgical irrigation and debridement.
T2 coronal MRI of left hand demonstrating palmar abscess and tenosynovitis.
T2 sagittal MRI of left hand demonstrating palmar abscess and tenosynovitis.
Treatment
We began by marking out Bruner incisions with extension as needed from the distal wrist crease to the volar aspect of the third metacarpophalangeal joint. We then made an incision extending from the proximal metacarpophalangeal crease to the proximal palmar crease. Blunt dissection was used to arrive at the level of the A1 pulley. We divided the palmar fascia to visualise the flexor tendon sheath. We elected to use an eschmark tourniquet shortly after incision due to the lack of a suitably sized standard cuff tourniquet for this small child, which greatly improved visibility.
We then visualised a purulent pocket deep to the palmar fascial layer from which we obtained a set of aerobic and anaerobic cultures. We then irrigated this area with normal saline and gently massaged the surrounding tissues but were unable to express any additional purulence. Next, we transversely opened the third digit flexor tendon sheath just proximal to the A1 pulley and encountered further purulent material from which we collected cultures. We irrigated this area gently with normal saline.
We then moved distally, making an ulnar mid-axial incision between the third digit proximal interphalangeal (PIP) joint and distal interphalangeal joint. We opened the ulnar aspect of the PIP joint just palmar to the ulnar collateral ligament due to suspected infection on MRI as well as joint distention on direct visualisation. Only benign appearing clear viscous joint fluid was expressed from which we obtained a third set of aerobic and anaerobic cultures. Moving distally, we released the tendon sheath between the A4 and A5 pulleys. We gained access to the sheath but encountered difficulty moving even the smallest paediatric feeding tube or even a 22-gauge angiocatheter through this channel.
We made a direct approach distally using a single limb Bruner incision over the proximal aspect of the distal phalanx. We divided the A5 pulley and were able to successfully irrigate distally to produce fluid in the proximal incision and vice versa with the 22-gauge angiocatheter. We irrigated multiple 60 mL syringes until the outflow was completely clear. We closed the incision with 4–0 chromic gut and placed penrose drains in the palmar and distal phalanx incisions. A sterile dressing and plaster splint were then placed.
Outcome and follow-up
Postoperatively, antibiotic coverage was broadened to intravenous vancomycin and ceftriaxone to cover for clindamycin-resistant S. aureus and for gram-negative pathogens. Intraoperative cultures were likely mischaracterised as growing a Bacillus species, which was suspected to be a contaminant. The clinical examination and inflammatory markers improved postoperatively. The patient was discharged home after 3 days of intravenous antibiotics. He then started a 10-day course of oral clindamycin. Three weeks later, the intraoperative culture grew K. kingae. Fortunately, by this time, the infection had completely resolved as evidenced by improved examination and normal inflammatory markers, and no further antibiotics were prescribed. The patient remained clinically well and had normal appearance and function of his left third and fourth digits at 21month follow-up.
The child’s mother provided written consent for this publication.
Discussion
K. kingae is a fastidious, often culture negative, gram-negative facultative anaerobic bacilli which frequently colonises the oropharynx of small children.7 It is highly contagious, and its prevalence may be underestimated due to asymptomatic colonisation.12 Patients with invasive K. kingae disease frequently report a preceding upper respiratory infection, as was also seen in this case. The bacterium has pili which play a critical role in adherence to the respiratory epithelium.7 These infections often present insidiously, with slow changes to the physical examination and changes in biological markers more subtle than those seen in more virulent pathogens.13 Once adherent, colonies form and create biofilms which further enable oropharynx colonisation and may cause invasive infections to be difficult to eradicate. It can enter the bloodstream through mucosal damage from an upper respiratory tract infection and can lead to invasive disease.7 Such mucosal erosions were observed in this child and may account for the seeding of the hand observed in the absence of blunt or penetrating trauma. Testing a child for K. kingae oropharyngeal colonisation has excellent negative predictive value for ruling out K. kingae as a cause of invasive infection.7 K. kingae creates rtxA toxin which serves as a target for genetic assays, such as K. kingae PCR, identifying the previously culture negative culprit for a variety of infections.12 If this test is available, the authors feel it should be used to guide management in the case of culture negative disease.
Optimal management of PFT includes prompt empiric intravenous antibiotics and source control with irrigation and debridement of the infection. Intraoperative cultures should be obtained to guide antibiotic therapy, as empiric coverage is adequate only about 80% of the time.14 Vancomycin or clindamycin both provide excellent empiric broad-spectrum coverage against methicillin-sensitive and methicillin-resistant S. aureus which is the leading cause of PFT. Community clindamycin resistance is rising, making it a less effective empiric antibiotic agent. Forty per cent of K. kingae are resistant to clindamycin, and vancomycin does not cover K. kingae.7 Beta lactam agents with beta lactamase resistance are the first line treatment for K. kingae infection. It is therefore important to consider K. kingae and other oral flora by adding a third generation cephalosporin to either vancomycin or clindamycin when empirically treating PFT in children aged 6–36 months. Given the eventual culture yield, our patient received suboptimal antibiotic coverage following surgical incision and drainage despite following empiric guidance consistent with recent literature,15 yet he experienced a full recovery. This is consistent with the nature of K. kingae infections which tend to be minimally virulent.7 12 This also highlights the importance of pathogen identification in the effective treatment of these infections. Emerging literature has suggested that the concerns for both Multi-drug Resistant Staphylococcus Aureus (MRSA and Kingella may be met in future by ceftaroline treatment, providing excellent coverage in the absence of culture guidance.16
Learning points
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Kingella kingae is a fastidious, often culture-negative, organism which has been increasingly recognised as a cause of paediatric orthopaedic infections, including flexor tenosynovitis.
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Patients with invasive K. kingae disease frequently report a preceding upper respiratory infection.
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K. kingae pyogenic flexor tenosynovitis can be optimally managed with prompt empiric intravenous antibiotics and source control with irrigation and debridement of the infection.
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First-line treatment for K. kingae infection is the use of a beta lactamase resistant penicillin or a second or third generation cephalosporin. In a culture negative patient, these will not provide MRSA coverage. Fifth generation cephalosporins may serve as monotherapy covering suspected Kingella while also providing excellent MRSA protection.
Ethics statements
Patient consent for publication
Footnotes
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Contributors CG: drafting, reviewing, literature search, operative technique review and direct publication assistance. AE: drafting, reviewing, literature search, operative technique review and direct publication assistance. ML: operative technique review and reviewing. DJA: research into antibiotic resistance profiles and current therapies and stewardship practices and reviewing.
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Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
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Case reports provide a valuable learning resource for the scientific community and can indicate areas of interest for future research. They should not be used in isolation to guide treatment choices or public health policy.
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Competing interests None declared.
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Provenance and peer review Not commissioned; externally peer reviewed.
- © BMJ Publishing Group Limited 2023. No commercial re-use. See rights and permissions. Published by BMJ.
References
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