How to Document Thumb Opposition Examination
Use a simplified 0-3 grading scale that documents where the thumb tip can reach: 0 = no opposition, 1 = touches middle phalanx of index finger, 2 = touches tip of index finger, 3 = touches tip of little finger. This validated system has excellent inter-observer reliability (kappa 0.991) and is particularly useful for clinical documentation 1.
Primary Documentation Method
The most practical and validated approach for clinical documentation involves:
- Grade 0: No opposition movement possible 1
- Grade 1: Thumb tip reaches the middle phalanx (second phalanx) of the index finger 1
- Grade 2: Thumb tip reaches the pulp/tip of the index finger 1
- Grade 3: Thumb tip reaches the pulp/tip of the little finger 1
This simplified scale specifically assesses abduction-rotation without requiring assessment of metacarpophalangeal or interphalangeal joint flexion, making it more straightforward than complex multi-step scales 1.
Alternative Detailed Documentation (Kapandji Scale)
For more comprehensive documentation, the traditional 10-point Kapandji scale can be used, though it is more complex 2:
- Score 1: Thumb touches lateral side of second phalanx of index finger 2
- Score 2: Thumb touches lateral side of third phalanx of index finger 2
- Score 3: Thumb tip touches tip of index finger 2
- Score 4: Thumb tip touches tip of middle finger 2
- Score 5: Thumb tip touches tip of ring finger 2
- Score 6: Thumb tip touches tip of little finger 2
- Score 7: Thumb touches DIP crease of little finger 2
- Score 8: Thumb touches PIP crease of little finger 2
- Score 9: Thumb touches proximal crease of little finger 2
- Score 10: Thumb reaches distal palmar crease 2
Critical Documentation Pitfalls
The test is only valid if initial stages are achievable - a thumb that merely crawls in the palm without true opposition movement should not be scored using these scales 2. True opposition involves three distinct components: abduction, flexion, and pronation of the thumb 3.
Biomechanical Context for Interpretation
When documenting opposition deficits, recognize that:
- Opposition involves coordinated movement across carpometacarpal, metacarpophalangeal, and interphalangeal joints 4
- Linear coupling exists between flexion and pronation at the CMC joint 4
- Conditions like carpal tunnel syndrome can reduce thumb path length during opposition by approximately 0.9 palm widths compared to normal, even with preserved pinch strength 5
Documentation Format
Record the examination as: "Thumb opposition: Grade [0-3]" or "Kapandji score: [1-10]" with notation of which finger/landmark the thumb can reach 2, 1. If using the simplified scale, specify that you are documenting abduction-rotation capacity 1.