Presentation
Basal thumb osteoarthritis causes:
- pain at the base of the thumb
- weakness of pinch and grip
- difficulty opening jars or turning keys
- adduction deformity in advanced disease
- compensatory MCP hyperextension
Examination
Look for swelling and deformity, then palpate the first CMC joint. Axial loading with circumduction can reproduce pain but should be interpreted with the rest of the examination.
Assess:
- first web-space contracture
- MCP hyperextension
- STT joint symptoms
- de Quervain disease as a differential
Imaging
Standard thumb/hand radiographs show joint-space loss, osteophytes, subchondral sclerosis and subluxation. Radiographic severity does not perfectly predict symptoms.
Radiographs can stage structural disease but correlate imperfectly with symptoms. Treatment should be driven by pain and function.
Non-operative treatment
activity modification
splinting
analgesia
hand therapy
intra-articular corticosteroid injection for selected patients
education and activity adaptation
analgesia
splintage
hand therapy
injection in selected patients
Surgical options
For persistent disabling symptoms:
- trapeziectomy with or without soft-tissue reconstruction
- first CMC arthrodesis in selected younger high-demand patients
- implant arthroplasty in selected settings
The key objectives are pain relief and functional pinch, not simply restoration of radiographic anatomy.
Associated MCP hyperextension may require simultaneous treatment when it compromises thumb function.
Clinical pattern
Thumb-base OA commonly causes pain with pinch and grip.
Symptoms include:
- pain at the first CMC joint
- weakness opening jars or turning keys
- difficulty with pinch
- progressive deformity
Examine for:
- local tenderness
- crepitus/grind
- subluxation
- MCP hyperextension
- thenar function
Biomechanics
The saddle-shaped CMC joint allows wide thumb movement but experiences high forces during pinch. Ligament insufficiency and cartilage degeneration can permit metacarpal subluxation and progressive deformity.
MCP hyperextension may develop as compensation.
Surgery
When symptoms remain substantial despite non-operative care, options include:
- trapeziectomy alone
- trapeziectomy with ligament/tendon procedures
- suspension techniques
- arthrodesis in selected high-demand cases
- implant arthroplasty in selected settings
No single operation is ideal for every patient.
Associated deformity
If MCP hyperextension is substantial, it may require separate treatment to restore a stable pinch posture.
FRCS synthesis
The aim is pain relief with a stable, mobile thumb and useful pinch. Radiographic stage alone should not dictate surgery.