Kanavel's Sign

Historical Overview

• Pyogenic flexor tenosynovitis (PFT) is an infection of the flexor tendon sheath of the finger that can result in tendon necrosis and adhesions leading to marked loss of motion, deformity, and loss of limb, particularly if treatment is delayed.¹
• Kanavel initially described three cardinal signs of PFT in his seminal work in 1912 as:
  1. Exquisite tenderness over the course of the sheath, limited to the sheath
  2. Flexed posturing of the finger
  3. Exquisite pain on extending the finger, most marked at the proximal end
  4. Although it was not noted as a cardinal sign in his initial description, “fusiform swelling of the entire digit” was also explained in this work and later became the fourth cardinal sign^1,2

Description

• Kanavel’s cardinal signs are a constellation of four clinical signs that are commonly used as the primary diagnostic tool for PFT.¹

Pathophysiology

• PFT is an uncommon, yet potentially devastating infection of the flexor tendon sheath that requires timely treatment to prevent loss of function and, in severe cases, amputation.³
• PFT is usually caused by penetrating trauma to the finger, but the presentation may be more indolent and chronic in immunocompromised patients. In these cases, the site of penetrating trauma can often be identified and may appear relatively mild, or there may be no history of trauma.¹
• The most common pathogen responsible for PFT is Staphylococcus aureus, while other causes include Methicillin-resistant S aureus, Sepidermidis, β-hemolytic Streptococcusspecies, and Pseudomona aeruginosa.¹

Instructions¹

1. Obtain an accurate and complete patient history, including any penetrating trauma and the presence of any immunocompromising conditions.
2. Examine the patient’s hand.
3. Observe if the affected digit is held in flexion.
4. Observe if the affected digit displays fusiform swelling.
5. Apply pressure to the tendon sheath and take note of the presence of pain or tenderness.
6. Apply a passive extension force to the affected digit and note of the presence of pain.

Variations

• One study proposed that a bedside ultrasound of the affected finger with a high-frequency linear probe and water bath technique could serve as Kanavel’s fifth sign. In the case presented, all four of Kanavel’s cardinal signs were present, but were not as intense as would be expected for typical PFT.⁴

Related Signs and Tests

• Hand radiographs
• MRI
• Ultrasonography
• Erythrocyte sedimentation rate
• Laboratory studies to identify the causative bacteria
• Kanavel’s signs are routinely used because advanced imaging and laboratory studies often are nonspecific.¹
• The inability to flex the finger to touch the palm has been identified an additional sign of PFT.⁵
• Conditions that mimic acute PFT include:¹
  • Abscesses
  • Felons
  • Herpetic whitlow
  • Gouty arthritis
  • Septic arthritis

Diagnostic Performance Characteristics

• Kanavel described excessive tendon sheath tenderness as the most important cardinal sign, and a study has concurred with this finding.
  • This paper also found flexor tendon sheath tenderness and pain with passive extension to be independent predictors of PFT.
  • On the other hand, finger flexion posture and fusiform swelling, although they frequently present in patients with PFT, did not appear to independently differentiate it from other finger infections.⁵

• A positive result occurs when the clinician observes one or more Kanavel’s signs.¹

• A negative result occurs when the clinician does not observe any of Kanavel’s signs.¹

• The presence of all four Kanavel’s signs should certainly raise clinical concern for a PFT diagnosis, but they should not be used themselves as a clinical prediction rule, as doing so assumes that each sign is independently significant and equal to another in terms of diagnostic utility.^1,5
  • On the other hand, the absence of one or more Kanavel’s signs does not necessarily exclude a PFT diagnosis.¹
• Kanavel’s signs have remained the primary diagnostic tool for PFT despite a lack of systematic validation for their use, and there are differing opinions in the literature regarding which signs are more suggestive of a PFT diagnosis than others.⁵
• One study found that Kanavel’s signs have high sensitivity for detecting PFT but individually have poor specificity.⁵
• Kanavel’s signs, particularly flexor tendon sheath tenderness, are more variable in children and adolescents than in adults. This variability may in part be explained by the limited ability of young children to cooperate and engage in a physical examination.³

1. Kennedy, CD, Huang, JI and Hanel, DP. In Brief: Kanavel's Signs and Pyogenic Flexor Tenosynovitis. Clin Orthop Relat Res 2016;474(1):280-4. PMID: 26022113
2. Kanavel AB: The symptoms, signs, and diagnosis of tenosynovitis and major fascial space abscesses. In Kanavel A, ed:Infections of the Hand, 6th Edition. Philadelphia, PA, Lea and Febiger, 1933, pp 364-395.
3. Brusalis, CM, Thibaudeau, S, Carrigan, RB, et al. Clinical Characteristics of Pyogenic Flexor Tenosynovitis in Pediatric Patients. J Hand Surg Am 2017;42(5):388 e1-388 e5. PMID: 28341068
4. Bomann, JS, Tham, E, McFadden, P, et al. Bedside ultrasound of a painful finger: Kanavel's fifth sign? Acad Emerg Med 2009;16(10):1034-5.PMID: 19732036
5. Kennedy, CD, Lauder, AS, Pribaz, JR, et al. Differentiation Between Pyogenic Flexor Tenosynovitis and Other Finger Infections. Hand (N Y) 2017;12(6):585-590. PMID: 28720000