Ulnar Intrinsic Atrophy | Hand Surgery Resource

Exams and Signs

Description

In the early stages of cubital tunnel syndrome, edema may be a sign of muscle denervation.¹
In severe cases of cubital tunnel syndrome, patients may display ulnar intrinsic atrophy, sensory disturbance and secondary joint contractures.² Severe cubital tunnel syndrome may eventually extend to a loss of function in the hand.³

Pathophysiology

Ulnar intrinsic atrophy may result from cubital tunnel syndrome or cervical radiculopathy. Some patients with cubital tunnel syndrome also have a history of diabetes, thyroid disease, or hemophilia.⁴
Repetitive, athletic activity may contribute to cubital tunnel syndrome in children, adolescents, or adults.

Instructions

Record the patient’s history, including any sports-related injuries. Ask the patient to rate on a scale from 1 to 10 how much pain s/he usually experiences in the affected hand and elbow
Ask the patient to abduct the small finger and the ulnar half of the ring finger against resistance¹
Check the hypothenar eminence for muscle wasting
Determine the muscle strength of the hand and elbow on the contralateral side for comparison

Variations

The Medical Research Council of Britain’s grading system describes muscle strength in Grades 0-5. Grade 0 describes no perceived muscle function, and Grade 5 describes typical muscle strength, as compared to the patient’s contralateral hand and elbow.⁵

Related Signs and Tests

Diagnostic Performance Characteristics

In patients with physical signs of cubital tunnel syndrome, electromyography (EMG) and nerve conduction velocity (NCV) studies show a false negative rate >10%.⁴
To improve reliability, MRI may be useful to detect distal muscle atrophy.¹

Presentation Photos and Related Diagrams

Definition of Positive Result

A positive result occurs if the patient’s affected hand shows a decrease in ulnar intrinsic muscle mass. In severe cases there will be a concavity in first web space dorsally and in the area of the hypothenar muscles. This loss of ulnar intrinsic muscle mass causes a decrease in strength, observed during abduction the small and ring fingers against resistance or resisted ulnar deviation of the pointed index finger.

Definition of Negative Result

A negative result occurs if the patient’s affected hand shows muscle strength and mass consistent with that of the contralateral normal side.
In a negative result the round hypothenar eminence and first dorsal interosseous muiscles bulge slightly against resistance and there is normal 5/5 muscle strength with no limitations.

Comments and Pearls

If the patient’s symptoms of ulnar intrinsic atrophy are sporadic, there is a greater possibility of success with conservative and operative treatments.⁴
If the patient experiences severe ulnar intrinsic atrophy, surgery for cubital tunnel syndrome may be necessary. To restore intrinsic muscle function, the patient may require 2-4 years of recovery.⁶

Diagnoses Associated with Exams and Signs

Videos

FDI atrophy and weakness demonstrated by muscle testing.

Hypothenar muscle atrophy and weakness demonstrated by muscle testing.

References

Culp R, Jacoby S. Musculoskeletal Examination of the Elbow, Wrist and Hand: Making the Complex Simple. New Jersey: SLACK Incorporated, 2012.
Boone S, Gelberman RH, Calfee RP. The management of cubital tunnel syndrome. J Hand Surg Am 2015;40(9):1897-1904. PMID: 26243318
Cutts S. Cubital tunnel syndrome. Postgrad Med J 2007;83(975):28-31. PMID: 17267675
Palmer BA, Hughes TB. Cubital tunnel syndrome. J Hand Surg Am 2010;35:153-63. PMID: 20117320
Medical Research Council. Aids to the Examination of Peripheral Nervous System. London, UK: Her Majesty’s Stationary Office; 1976.
Matsuzaki H, Yoshizu T, Maki Y, et al. Long-term clinical and neurologic recovery in the hand after surgery for severe cubital tunnel syndrome. J Hand Surg Am 2004;29:373-8. PMID: 15140474