Sweater Finger Sign


Purpose

The sweater finger sign also called Jersey Test is used to confirm the rupture or the integrity of the Flexor Digitorum Profundus (FDP) Tendon. It occurs most often to the ring finger [1].

Muscles that move the Forearm.png

Clinically Relevant Anatomy

Flexor Digitorum Profundus is a fusiform muscle located deep within the anterior (flexor) compartment of the forearm [2]. The FDP muscle divides into 4 tendons that run down the forearm and closer to the bone. These tendons insert into the base of the distal phalanges of the index, middle, ring, and little fingers, and assist in bending them at the fingertip joint.[3]. As the tendons of the FDP arise at or below the wrist joint, they allow a power grip by the contraction of the muscle [4].

Testing position

The patient's position while tested should be sitting.

Technique

The following steps are taken to confirm if the sign is positive or not: [5]

Step 1. The therapist holds the patients' Metacarpophalangeal (MCP) and Proximal interphalangeal (PIP) in full extension.

Step 2. Then the patient is asked to flex at the DIP or make a fist.

Step 3. The PIP must be tested in full extension to isolate FDP function.

Step 4. If the FDP is intact, the patient will be able to flex at the DIP.

Interpretation of results

The sweater finger sign is said to be positive when the finger is not bent; when there is a loss of flexion at DIP of one of the fingers.

Clinical Indication

The Jersey test is indicated in the diagnosis of the Flexor digitorum profundus injury [6].

Resources


References

  1. Wallmann HW. Overview of Wrist and Hand Orthopaedic Special Tests. Home Health Care Management & Practice. 2011 Jun;23(3):218-20.
  2. Flexor digitorum profundus muscle. Available from: https://www.kenhub.com/en/library/anatomy/flexor-digitorum-profundus-muscle ( Accessed, 31 October 2020)
  3. Tendons. Available from: https://www.assh.org/handcare/safety/tendons#:~:text=Flexor%20digitorum%20profundus%20(FDP)%20tendons&text=They%20run%20down%20the%20forearm,in%20the%20hand%20and%20fingers (Accessed, 01 November 2020)
  4. Lung BE, Burns B. Anatomy, Shoulder and Upper Limb, Hand Flexor Digitorum Profundus Muscle. InStatPearls [Internet] 2019 Feb 10. StatPearls Publishing.
  5. Demystifying the Hand Exam. Available from: https://www.nuemblog.com/blog/2018/4/9/hand-exam (Accessed, 31 October 2020)
  6. Han Exam. Available from: https://fpnotebook.com/ortho/exam/HndExm.htm ( Accessed, 31 October 2020)
  7. Alfred University Health and Human Performance. Sweater Finger Sign. Available from: http://https://www.youtube.com/watch?v=cEaMYr0NuWk [last accessed 31/10/2020]
  8. Dr. Nabil Ebraheim. Jersey Finger - Everything You Need To Know. Available from:https://www.youtube.com/watch?v=rwy9gfN0K_Q [ last accessed 31/10/2020]