Flexor Digitorum Superficialis and Profundus Tendon Sheath Injection

Other Names

• Flexor Digitorum Superficialis and Profundus Tendon Sheath Injection
• Flexor Digitorum Superficialis Injection
• Flexor Digitorum Profundus Injection
• FDS Injection
• FDP Injection

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Background

Cross section of the wrist highlighting FDS and FDP

Key Points

• Use a high frequency, linear transducer
• Needle: 25- to 27-gauge, 1.0- to 1.5 inch needle
• Avoid median nerve, ulnar nerve, ulnar artery

Anatomy of FDP, FDS

• Flexor Digitorum Profundus
  • Origin: proximal ulna, interosseous membrane
  • Insertion: distal phalanx of digits 2-5
• Flexor Digitorum Superficialis
  • Origin: medial epicondyle, proximal ulna, proximal radius
  • Splits distally into four slips, passing superficial to the FDP
  • Insertion: middle phalanx of digits 2-5
• Both FDP, FDS tendons pass through carpal tunnel at the wrist
• Enveloped in synovial sheath
• Median Nerve is superficial to FDS on the radial side

Palpation Guidance vs Ultrasound Guidance

• It is recommended that this injection be performed with ultrasound guidance
• There is no literature comparing palpation and ultrasound guidance

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Indications

• Wrist Tendinopathies of FDP or FDS

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Contraindications

• Absolute
  • Anaphylaxis to injectates
  • Overlying cellulitis, skin lesion or systemic infection
• Relative
  • Can be treated with less invasive means
  • Hyperglycemia or poorly controlled diabetes
  • Lack of symptom improvement with previous injection

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Procedure

Normal sonographic view of the flexor digitorum tendons at the level of the wrist crease: FCR, flexor carpi radialis; FDP, flexor digitorum profundus; FDS, flexor digitorum superficialis; FPL, flexor pollicis longus; M, median nerve; P, palmaris; UA, ulnar artery; and UN, ulnar nerve.

FDS and FDP injection in short axis, in plane technique with needle and probe position

Ultrasound view FDS and FDP injection using short axis, in plane technique.

Equipment

• Sterile prep (i.e. chloraprep, chlorhexidine, iodine, etc)
• Gloves
• Needle: typically 21-25 gauge, 1.5 inch
• Syringe: 5-10 mL
• Gauze
• Ethyl Chloride
• Bandage
• Injectate
  • Local anesthetic
  • Corticosteroid
• Sterile probe cover

Ultrasound Findings

• Ultrasound approach
  • Best visualized in short axis
  • Depth is 1-2 cm
  • Start at proximal carpal tunnel
  • Can see 4 tendons of FDS superior to FDP
  • Find the median nerve, usually superficial and slightly radial
  • Use anisotropy to distinguish between nerve and tendon
  • Identify the radial artery, ulnar artery/nerve
• Common ultrasound findings include
  • Increased interfibrillar distance (hypoechoic tendon appearance)
  • Tendon thickening
  • Fluid within the tendon sheath

Technique: Short Axis, In Plane

• Patient Position
  • Wrist supinated
  • Slightly extended if possible
• Transducer position
  • Short axis over the carpal tunnel
• Needle Approach/ Orientation
  • In plane
  • Ulnar to radial approach
• Target
  • Synovial sheath of FDP and/or FDS
• Pearls and Pitfalls
  • On radial side, avoid radial artery and median nerve
  • On ulnar side, avoid ulnar artery and ulnar nerve
  • Doppler and anisotropy can be use be used to orient
  • A step-off technique can help with approach

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Aftercare

• No significant restrictions
• Can augment with ice, NSAIDS
• Consider temporary cock up wrist splint after procedure

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Complications

• Skin: Subcutaneous fat atrophy, skin atrophy, skin depigmentation
• Painful local reaction
• Infection
• Hyperglycemia
• Tendon, nerve or blood vessel injury

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See Also

• Procedures Main
• Ultrasound Main
• Wrist Pain Main

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