Mallet Finger (Drop Finger, Baseball Finger) - observation

Historical Overview

• Mallet finger was first described in 1880 by Segond.¹
• Examination of the extensor tendons is a long-established component of the routine clinical examination of the hand.
• The exam is used in the diagnosis of mallet finger, as well as in Kirners deformity,¹ Dupuytren’s disease,² certain injuries to the digits,³ rheumatoid arthritis and a variety of other diseases, disorders and conditions⁴

Description

•  A mallet finger is a finger in which the distal interphalangeal joint is held in a flexed position.²
• This is caused by an extension lag or a fixed flexion contracture in more chronic cases.

Pathophysiology

• A flexion deformity due to division or elongation of the terminal extensor tendon at the distal interphalangeal (DIP)joint. ²

Instructions

• The patient is examined for a finger with extension lag at the distal interphalangeal joint.
• The distal interphalangeal joint is also examined for tenderness dorsally.

Variations

• The degree of deformity from the injury may vary from loss of extension of a few degrees to a 75–80° contracture of the DIP joint.³

Related Signs and Tests

• Fingers can be bent at the proximal interphalangeal (PIP) joint owing to a variety of diseases, disorders and conditions, including Kirner’s deformity,⁵ Dupuytren’s disease,³ other injury,⁶ and rheumatoid arthritis.⁷

Diagnostic Performance Characteristics

• Findings from the history and physical examination define the condition. Therefore, a condition that meets the criteria described in the “Instructions” section above, by definition, has a sensitivity (true positive rate; proportion of actual positives that are correctly identified as such) and specificity (true negative rate; proportion of actual negatives that are correctly identified as such) of 100%.
• The ability of individual clinicians to apply these criteria will alter the sensitivity and specificity of this diagnostic exam.

• A positive result occurs when the patient has tenderness at the dorsum of DIP joint and an extension lag.

• A negative result when the patient does not ahve tenderness at the dorsum of DIP joint and an extension lag.

• The force of the blow that causes mallet finger may pull away a piece of bone along with the tendon.⁴ This is called a mallet fracture
• In most cases, X-rays are ordered.⁴
• There is a history of closed or blunt trauma to the tip of the affected digit, laceration at or proximal to the distal interphalangeal (DIP) joint, or deep abrasion with loss of skin, subcutaneous cover and tendon substance.³
• In cases of closed trauma, the finger is usually painful, swollen and bruised. The fingertip may droop noticeably. Occasionally, blood collects beneath the nail. The nail can become detached from beneath the skin fold at the base of the nail.⁴

1. Browner D, Jupiter J, Levine A, Trafton P, Krettek C (eds): Skeletal Trauma Basic Science, Management, And Reconstruction Fourth Edition. Saunders Elsevier, Philadelphia, 2009.
2. Tubiana R, Thomine, J-M. Mackin E. Examination of the Hand and Wrist. New York: Informa Healthcare, 2009.
3. Doyle JR. Hand and Wrist (Orthopaedic Surgery Essentials Series). Philadelphia: Lippincott Williams & Wilkins, 2006.
4. OrthoInfo. Mallet Finger (baseball finger). American Acadamy of Orthopaedic Surgeons. 2014, available at http://orthoinfo.aaos.org/topic.cfm?topic=a00018. Accessed January 20, 2015
5. Frank R. Campodactyly, Orthobullets. Available at http://www.orthobullets.com/hand/6074/camptodactyly. Accessed January 20, 2015.
6. Rayan GM and Akelman, E. The Hand: Anatomy, Examination, and Diagnosis. Philadelphia: Lippincott Williams & Wilkins, 2012.
7. Culp R and Jacoby SM. Musculoskeletal Examination of the Elbow, Wrist, and Hand: Making the Complex Simple. Thorofare: Slack Inc., 2012.