Thumb CMC Grind Test

Thumb CMC Grind Test (Carpometacarpal Grind Test) is used to assess the osteoarthritis of the carpometacarpal joint of the thumb. Where the examiner applies axial compression along the plane of the thumb metacarpal and simultaneously rotates the thumb metacarpal base.

How do you perform Thumb CMC Grind Test?

The clinician grasps the thumb metacarpal using the thumb and index finger of one hand and the proximal aspect of the thumb carpometacarpal joint with the other hand.

An axial compressive force, combined with rotation, is applied to the thumb carpometacarpal joint.

What does a positive Thumb Grind Test mean?

• Thumb Grind Test is positive if Pain is reported in the carpometacarpal joint of the thumb, it is usually due to osteoarthritis in the joint (differential diagnosis includes a Bennett or Rolando fracture).
• Tenderness to palpation and painful instability are additional signs of wear in the joint.
• The patient will typically also complain of pain in the carpometacarpal joint of the thumb when opposing the thumb against the resistance of the examiner’s hand.

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Sensitivity & Specificity

A study¹ found that The grind test has a low sensitivity and a high specificity, that make it as of limited diagnostic value:

• Sensitivity: 42 %
• Specificity: 80 %

A study Melissa M Merritt found that the sensitivity of the CMC grind test was 42% and 53%, depending on tester. The specificity of the grind test was 80% and 93%, depending on tester. The positive likelihood ratio was 2.65 and 6.00, and the negative likelihood ratio was 0.59 and 0.62. The positive predictive value was 91% and 96%, depending on tester. The negative predictive value was 68% and 70%, depending on tester. He conclude that the thumb CMC grind test has moderate reliability and accurately confirms the diagnosis of CMC osteoarthritis and identifies those who do not have CMC osteoarthritis. However, a negative grind test does not necessarily reflect negative radiographic evidence of thumb CMC osteoarthritis.

Another Comparative Study by R M Choa found that the CMC grind test has a 30% sensitivity and 96.7%, specificity.

Thumb CMC

Thumb carpometacarpal joint (also termed basal joint or CMC joint) .

Up to 50% of patients with thumb CMC osteoarthritis also have carpal tunnel syndrome.

Eaton and Littler staging for CMC joint arthritis:

STAGE	DESCRIPTION
Type I	Normal-appearing joint with the exception of possible widening from synovitis
Type II	Joint space narrowing, with debris and osteophytes < 2 mm
Type III	Joint space narrowing, with debris and osteophytes 2 mm
Type IV	Joint space narrowing of scaphotrapezial and trapeziometacarpal articulations

Most commonly performed procedure for advanced thumb CMC osteoarthritis is trapezium excision with ligament reconstruction and tendon interposition.

Reference

1. Zina Model, Andrew Y. Liu, Lana Kang, Scott W. Wolfe, Jayme C. Burket, and Steve K. Lee: Evaluation of Physical Examination Tests for Thumb Basal Joint Osteoarthritis. Hand (N Y). 2016 Mar; 11(1): 108–112. PMID: 27418899
2. Waggy C: Disorders of the wrist. In: Wadsworth C, ed. Orthopaedic Physical Therapy Home Study Course – The Elbow, Forearm, and Wrist. La Crosse, WI: Orthopaedic Section, APTA, Inc., 1997.
3. Swanson A: Disabling arthritis at the base of the thumb: Treatment by resection of the trapezium and flexible implant arthroplasty. J Bone Joint Surg Am 54A:456, 1972.
4. Choa RM, Parvizi N, Giele HP. A prospective case-control study to compare the sensitivity and specificity of the grind and traction-shift (subluxation-relocation) clinical tests in osteoarthritis of the thumb carpometacarpal joint. J Hand Surg Eur Vol. 2014 Mar;39(3):282-5. doi: 10.1177/1753193413508714. Epub 2013 Oct 14. PMID: 24127463.
5. Merritt MM, Roddey TS, Costello C, Olson S. Diagnostic value of clinical grind test for carpometacarpal osteoarthritis of the thumb. J Hand Ther. 2010 Jul-Sep;23(3):261-7; quiz 268. doi: 10.1016/j.jht.2010.02.001. Epub 2010 May 10. PMID: 20452743.
6. Green DP et al, editors: Green’s operative hand surgery, ed 6, Philadelphia, 2011, Churchill Livingstone, p 409.
7. Clinical Tests for the Musculoskeletal System 3rd Edition.
8. Dutton’s Orthopaedic Examination, Evaluation, And Intervention 3rd Edition.