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Muscle Test: First Dorsal Interosseous (FDI) [Ulnar Intrinsics]

Exams and Signs
Origin:First and second metacarpals
Insertion:Dorsal extensor expansion
Innervation:Cervical root(s):  C8-T1
Nerve: Ulnar Nerve

 

Grading of Muscle Strength:

GradeStrengthDescription
5NormalComplete range of motion against gravity and full resistance
4GoodComplete range of motion against gravity and some resistance
3FairComplete range of motion against gravity with no additional resistance
2PoorComplete range of motion with gravity eliminated and no resistance
1TraceEvidence of slight muscle contraction but no joint or tendon motion
0ZeroNo evidence of any muscle contraction and no joint motion
Position of patient's hand and upper extremity:
The forearm and hand are resting on the table in neutral forearm rotation with the wrist in mild extension.  The thumb should be pinching the long finger and the index finger pointing straight ahead.

 

Examiner’s Actions:

  • The examiner uses his or her index finger to portion the patient's pointing index finger towards the table with his or her nondominant index finger.  (I.e. the examiner tries to adduct the patient's index finger against the patient's resistance).  While performing this maneuver the examiner palpates the patient's first dorsal interosseous muscle with their dominant index finger.  By palpating the muscle the examiner assesses muscle contraction and notes the strength that the patient can provide against the examiner's resistance.

Directions for the patient:

  • “Put your hand on the table and point your index finger straight ahead and hold it there as hard as you can.” “hold your index finger up towards the ceiling and do not let me push it down.”
Presentation Photos and Related Diagrams
  • Testing the right first dorsal interosseous muscle, the last muscle innervated by the ulnar nerve.
    Testing the right first dorsal interosseous muscle, the last muscle innervated by the ulnar nerve.
  • Testing the left first dorsal interosseous muscle. The last muscle innervated by the ulnar nerve.
    Testing the left first dorsal interosseous muscle. The last muscle innervated by the ulnar nerve.
Definition of Positive Result

In muscle testing a normal result is a positive one. During a normal muscle test, the examiner should observe a normal muscle contraction that can move the joint or tendon against full resistance.

Definition of Negative Result

In muscle testing a abnormal result is a negative one. During a abnormal muscle test, the examiner should observe a abnormal muscle contraction that can move the joint or tendon. In a complete denervation injury, such as a complete nerve laceration, there will be no evidence of any muscle function.  The muscle testing grade will be zero.

Comments and Pearls
  • When the patient can demonstrate full normal resistance, usually the examiner cannot "break" the patient's effort.
Diagnoses Associated with Exams and Signs
Videos
First Dorsal Interosseous Muscle testing
References

Hislop JH, Avers D, and Brown M. Daniels and Worthingham's Muscle testing, Techniques of Manual Examination and Performance Testing. 9th ed. St.Louis, Missouri: Elsevier Saunders; 2014: 138-202.

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