MC Flexion Test | Carpometacarpal OA | Thumb Osteoarthritis

Thumb osteoarthritis (OA) is a painful and debilitating condition that affects a large proportion of the adult population, with radiographic prevalence reaching 90% in both men and women by the age of 80. This condition can cause pain at the base of the thumb, progressive loss of thumb motion, weakness, and decreased coordination, which worsens over time.

Qualitative assessment of the history, physical examination, and radiographs are used to diagnose and treat thumb CMC arthritis. The location, duration, onset, frequency, intensity, and quality of the pain are all under consideration.

Sela et al. (2017) conducted a comparative study to determine the best diagnostic tests for CMC OA of the thumb by comparing the results of 4 provocative tests with the Eaton-Littler classification system of radiologic evaluation of the CMC joint.

Eaton-Littler Classification

1. Subtle carpometacarpal joint space widening
2. Slight carpometacarpal joint space narrowing, sclerosis, and cystic changes with osteophytes or loose bodies < 2mm
3. Advanced carpometacarpal joint space narrowing, sclerosis, and cystic changes with osteophytes or loose bodies > 2mm
4. Arthritic changes in the carpometacarpal joint as in stage III with scaphotrapezial arthritis

In their study, the MC flexion test yielded a sensitivity of 46% and a specificity of 100%.
The MC-flexion test appears to be a good test to confirm the diagnosis of CMC osteoarthritis. A negative test, however, does not always imply negative radiographic evidence of thumb CMC osteoarthritis. With OA it has to be added that it remains a clinical diagnosis and changes seen on radiographic imaging don’t necessarily need to cause any disability or pain, which is why we give this test a moderate clinical value.

To conduct the test, the patient is in sitting position and the hand is placed on a stable surface such as the examination table. The examiner grasps the patient’s hand with one hand in order to stabilize it. The patient’s wrist and metacarpals are in neutral position. With the other hand, the examiner places the metacarpal in flexion.

The test is considered positive if moving the MC into flexion created pain (even a slightly painful sensation) in the basal region of the thumb.

21 OF THE MOST USEFUL ORTHOPAEDIC TESTS IN CLINICAL PRACTICE

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Other orthopedic tests to assess CMC1 osteoarthritis are:

• Grind Test
• Pressure Shear Test
• MC Extension Test
• Traction-Shift/Subluxation Relocation Test
• Adduction Test
• Extension Stress Test

References

Sela, Y., Seftchick, J., Wang, W. L., & Baratz, M. E. (2019). The diagnostic clinical value of thumb metacarpal grind, pressure-shear, flexion, and extension tests for carpometacarpal osteoarthritis. Journal of Hand Therapy, 32(1), 35-40.