Dorsal Approach to Radius

The Dorsal approach to radius also called Thompson approach, provides good access to the entire dorsal aspect of the radial shaft.

• The Dorsal approach to radius is used for:
  1. ORIF of radial shaft fractures using extensor side of bone.
  2. Treatment of delayed union or nonunion of fractures of the radius .
  3. Access to the posterior interosseous nerve as it passes through the arcade of Frohse for:
     • nerve paralysis.
     • resistant tennis elbow.
  4. Radial osteotomy.
  5. Osteomyelitis and bone tumor resection/biopsy.

• Place the patient in the Supine position:
  1. If the arm is abducted to the side on an arm board, the forearm should be pronated.
  2. If the arm is adducted across the chest, the forearm should be supinated,
     • If the ulna must be approached as well as the radius, this position will allow easier access to the ulna through a separate incision.

• Landmarks:
  • Proximal:
    • Lateral epicondyle of the humerus.
  • Distal:
    • Dorsoradial tubercle (Lister’s tubercle).
• Incision:
  • Starting point is anterior and distal to the lateral epicondyle of the humerus,
  • straight or gently curved incision along the dorsolateral aspect of the forearm,
  • be aware of superficial radial nerve and cephalic vein distally.
  • end incision just distal and ulnar to Lister’s tubercle.

• The Internervous plane for the Dorsal approach to radius (Thompson approach) is:
  • Proximally between:
    • Extensor carpi radialis brevis muscle (ECRB): innervated by the radial nerve.
    • Extensor digitorum communis muscle (EDC): innervated by the posterior interosseous nerve.
  • Distally between:
    • Extensor carpi radialis brevis muscle (ECRB): innervated by the radial nerve.
    •  extensor pollicis longus muscle (EPL): innervated by the posterior interosseous nerve.

• Proximal third:
  • Incise fascia in line with skin incision using interval between extensor carpi radialis brevis muscle (ECRB) and the extensor digitorum communis muscle (EDC) to reveal supinator muscle.
• Middle third:
  • Identify the abductor pollicis longus (APL) and extensor pollicis brevis (EPB) emerging between extensor carpi radialis brevis muscle (ECRB) and the extensor digitorum communis muscle (EDC).
• Distal third:
  • Undermine the abductor pollicis longus (APL) and extensor pollicis brevis tendons medially to identify plane between extensor pollicis longus and extensor carpi radialis brevis muscle (ECRB).

• Proximal third:
  • Identify the insertion of supinator by turning arm into full supination,
  • supination moves the posterior interosseous nerve away from area of deep dissection.
  • incise insertion of supinator along radius and subperiosteally strip supinator off bone to expose proximal third of radius.
  • for more proximal exposures, two deep approaches exist to protect posterior interosseous nerve:
    • dissecting proximal to distal:
      • detach origin of extensor carpi radialis brevis muscle (ECRB) and
      • extensor carpi radialis longus muscle (ECRL) from lateral epicondyle and identify and dissect posterior interosseous nerve  as it enters supinator muscle.
    • dissecting distal to proximal:
      • identify nerve as it exits supinator and dissect it proximally out of supinator substance.
• Middle third:
  • Make incision along superior and inferior borders of abductor pollicis longus (APL) and extensor pollicis brevis (EPB).
  • retract them off bone to expose middle third of radius.

• Distal third:
  • separating the extensor carpi radialis brevis muscle (ECRB)and extensor pollicis longus (EPL) will directly lead to the lateral border of the radius.
  • part of the interosseous membrane may have to be removed to approach the radius.

• The dorsal approach to radius (Thompson approach) can be extended to the dorsal side of the wrist ( Dorsal Approach to the Wrist ).
• Dorsal approach to radius (Thompson approach) can be extended proximally to expose the lateral epicondyle of the humerus ( Lateral Approach to Distal Humerus ).

The structures at risk during dorsal approach to radius (Thompson approach) include:

1. Posterior interosseous nerve (branch of radial nerve):
   • Injury usually occurs from retraction.
   • In 25% of patients the nerve actually touches the dorsal aspect of the radius.
   • Plates placed high on the dorsal surface may trap the nerve.
   • Posterior interosseous nerve must be identified within the supinator muscle.
2. Posterior interosseous artery:
   • Accompanies the Posterior interosseous nerve along the interosseous membrane in the proximal 1/3 of radius.

• Surgical Exposures in Orthopaedics book - 4th Edition
• Campbel's Operative Orthopaedics book 12th