Posterior approach to the humerus

Introduction

The median posterior approach to the humerus is a classic, extensile exposure that provides excellent access to the lower three-quarters of the posterior humeral surface.

Indications

The posterior approach to the humerus is used for:

1. Open reduction and internal fixation of humeral fractures:
   • Often considered more cosmetic than the anterolateral approach.
   • Provides good exposure for both mid-shaft and distal-third humeral fractures.
2. Treatment of osteomyelitis.
3. Biopsy and excision of tumors.
4. Treatment of fracture nonunions (pseudarthrosis).
5. Exploration of the radial nerve in the spiral groove.
6. Insertion of retrograde humeral nails.

One study found that the anterolateral approach offers advantages over the posterior approach for treating simple humeral shaft fractures.

Patient Positioning

• Prone position with the arm on an arm board, abducted 90 degrees.
• Lateral position with the arm across the body.

A sandbag should be placed under the shoulder on the operative side. The elbow should be flexed, and the forearm should hang over the edge of the table.

Landmarks and Incision

• Landmarks:
  1. The acromion.
  2. The olecranon fossa.
• Incision:
  • A longitudinal midline incision on the posterior aspect of the arm, starting 8 cm distal to the acromion and extending to the olecranon fossa.

Internervous Plane

There is no true internervous plane for the posterior approach to the humerus. It is a muscle-splitting approach through the heads of the triceps brachii muscle, all of which are innervated by the radial nerve.

Because the nerve branches enter the muscle heads relatively close to their origin and travel distally within the muscle belly, a longitudinal split of the muscle does not denervate any portion of it.

Furthermore, the medial (deepest) head has a dual nerve supply from both the radial and ulnar nerves. A longitudinal split through the medial head will therefore not denervate either half.

Superficial Dissection

• The fascia should be split along the line of the skin incision.

Deep Dissection

• Splitting the fascia between the long and lateral heads of the triceps:
  • The lateral head is retracted laterally, and the long head is retracted medially.
• The radial nerve, along with the profunda brachii vessels, is identified in the spiral groove:
  • The radial nerve runs directly proximal to the medial head of the triceps, which lies deep to the other two heads in the spiral groove.
  • A tourniquet is often helpful until the nerve has been identified.

Approach Extension

The posterior approach to the humerus can be extended.

Proximal Extension

• The posterior approach does not effectively expose the bone proximal to the spiral groove. At this level, the deltoid muscle also crosses the surgical field.
• Further proximal exposure should be obtained through an anterior approach.

Distal Extension

• The skin incision can be extended distally past the olecranon. By deepening the approach, access to the elbow joint is created through an olecranon osteotomy.

Dangers

Structures at risk during the posterior approach to the humerus include:

• Nerves:
  1. The radial nerve is vulnerable in the spiral groove.
  2. The ulnar nerve lies deep to the medial head of the triceps in the distal third of the arm.
• Vessels:
  • The profunda brachii artery travels with the radial nerve in the spiral groove and is similarly at risk of injury.

Related Anatomy

Triceps Muscle

The triceps muscle has two layers.

1. The outer layer consists of two heads: the lateral head originates from the lateral lip of the spiral groove, and the long head originates from the infraglenoid tubercle of the scapula.
2. The inner layer is the third head, the medial (or deep) head, which extends across the entire width of the posterior humerus from below the spiral groove down to the distal quarter of the bone.

The spiral groove contains the radial nerve; therefore, the radial nerve effectively separates the origins of the lateral and medial heads.

References

• Book “Surgical Exposures in Orthopaedics” – 4th Edition.
• Campbell’s Operative Orthopaedics, 12th Edition.
• Li Y, Tian Q, Leng K, Guo M. Comparison of posterior and anterolateral surgical approaches for the treatment of humeral shaft fractures: A retrospective study. Med Sci Monit. 2020 Jul 8;26:e924400. doi: 10.12659/MSM.924400. PMID: 32639953; PMCID: PMC7366785.