Thumb and Finger Joint Injection

Acute or chronic capsulitis

Causes and findings:
• Overuse or trauma
• Rheumatoid or degenerative arthritis
• Capsular pattern
• Thumb: painful and limited passive adduction of thumb backwards behind hand painful and limited passive extension and abduction
• Fingers: painful and limited extension with ulnar deviation at metacarpophalangeal joints painful and limited passive flexion at interphalangeal joints painful and limited passive extension at distal phalangeal joints

Equipment:
Syringe - 1ml
Needle - 23G 0.5 inches (16mm) orange
Kenalog 40 - thumb 10 mg, fingers 10 mg
Lidocaine - thumb 0.75 ml 2%, fingers 0.5 ml 2%
Total volume - thumb 1 ml, fingers 0.75 ml

Anatomy:
The first metacarpal articulates with the trapezium. The easiest entry site is at the apex of the snuff-box on the dorsum of the wrist. The joint line is found
by passively flexing and extending the thumb while palpating for the joint space between the two bones. The radial artery lies at the base of the snuffbox.
The distal thumb joint, and all finger joints can best be infiltrated from the medial or lateral aspect at the joint line.

Technique:
• Patient rests hand in mid position with thumb up and traction is applied by patient
• Identify gap of joint space at apex of snuff box on dorsum of wrist
• Insert needle perpendicularly into gap
• Inject solution as a bolus

Aftercare:
Tape the thumb using a spica technique, or tape two fingers together to splint them for a few days. Patient then begins gentle active and passive mobilizing
exercise within pain-free range and is advised against overuse of the thumb or fingers. Dipping the fingers into warm wax baths and using the wax ball as an exercise tool can be beneficial.

Comments:
Trapeziometacarpal joint capsulitis is a common lesion of older females and the results of infiltration are uniformly excellent. Often it is several years
before a repeat injection is required, provided the patient does not grossly overuse the joint.

Alternative approaches:
Infiltrating the thumb and finger joints can be difficult as osteophytosis will almost certainly be present. It is sometimes necessary to anaesthetize the capsule with some of the solution while trying to enter the joint. Gapping the side of the joint being entered also helps, and an even finer needle, such as 30G, can be used.