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Wrist Denervation

Introduction

  • Indicated for patients with persistent wrist pain
  • Pain etiologies:
    • Distal radius malunion
    • Scaphoid non-union
    • Scapholunate dissociation
    • Ligamentous instability
    • Inflammatory arthritis
    • Degenerative arthritis
    • Kienböck disease
  • Partial denervation is a neurectomy of the:
    • Anterior interosseous nerve (AIN)
    • Posterior interosseous nerve (PIN)
  • Compete wrist denervation includes the
    • AIN
    • PIN
    • Lateral cutaneous nerve of the forearm
    • Superficial radial nerve
    • Palmar branch of the median nerve
    • Dorsal branches of the ulnar nerve
  • Surgical candidates
    • Best for young patients with good range of motion
    • Elderly patients regardless of range of motion
    • Respond to local, temporary nerve block
  • This proceed does not prevent further arthrodesis, arthroplasty or carpectomy

Anatomy

Posterior Interosseous Nerve 

  • Terminal branch of the radial artery 
  •  Exits the distal edge of the supinator muscle

Patient Evaluation

Local, Temporary Nerve Blockade

  • Tests the anticipated response to neurectomy
  • Local anesthetic in injected into several points to elucidate where the pain in eminating from
  •  If and when the injection resolves the pain, no further injections are needed 
  • Neurectomies should be performed of the nerves that responded to the local injections with pain resolution
  • Instill 1-2 ml of local anesthetic into the following points in order:

Injection Point #1:  AIN/PIN

  • On the dorsal, distal forearm at a point located 1 cm ulnar and 3 cm proximal to Lister’s tubercle on the dorsal, distal forearm
  • Insert the needle vertically until resistance of the interosseous membrane is felt
  • Withdraw the needle 2 mm and inject (targets the PIN)
  • Advance the needle to 2 mm past the interosseus memebrane and inject (targets the PIN)

Injection Point #2: Dorsal articular branch of the ulnar nerve

  • At the ulnar border of the styloid process, insert the needle vertically
  • Inject against the bone and just volarly

Injection Point #3: Branches of the radial nerve

  • Inject subcutaneously approximately 3 cm proximal to the wrist around the radial vessels
  • Inject dorsally and proximally over this area as well

Injection Point #4: Palmer branch of median nerve and AIN

  • At the ulnar boarder of the plamaris longus tendon and 3 cm proximal to the wrist crease, insert the needle vertically
  • Inject superficial to the radius and interosseous membrane

Surgical Technique

  1. Incision dorsally between the 2nd and 4th dorsal compartments to access the PIN
    1. Incise through the extensor retinaculum at the ulnar border of the 3rd compartment (EPL)
    2. Open the 4th dorsal compartment 
    3. Retract the extensor tendons ulnarly and the EPL radially to expose the PIN
    4. The PIN sits at the radial aspect of the  base of the this compartment
    5. Dissect the PIN free of the posterior interosseous artery 
    6. Resect at 1 cm segment of the PIN
      1. Send to pathology for frozen evaluation to confirm nerve fascicles present
    7. Incise through the interosseous membrane via longitudinal incision to reach the AIN
      1. There is a risk of denervating the pronator quatdratus if the AIN is sectioned 2 cm or more proximal to the ulnar head
      2. This is nearly complete if the AIN is sectioned 4 cm or more proximal to the ulnar head
    8. Alternatively, may use volar approach to access the AIN (below)
    9. Dissect the skin flaps ulnarly and radially to separate the subcutaneous tissue off of the extensor retinaculum, which essentially detaches the small fibers from the ulnar and radialy sensory branches to the wrist
      1. Use tenotomy scissors and a freer to sweep across and release these fibers
  2. Volar incision over the FCR tendon to access the AIN
    1. Dissect along the radial side of the FCR tendon
    2. Elevate the pronator quadratus (PQ) muscle, under which lies the AIN
      1. The AIN sends a motor branch to the PQ and the continues on to supply sensory to the wrist