Posterior Approach to the Humerus

The midline posterior approach to the humerus is classically extensile, providing excellent access to lower three fourths of the posterior aspect of the humerus.

Posterior Approach to the Humerus is used for:

1. Open reduction and internal fixation of fractures of the humerus:
   • Often thought to be more cosmetic when compared to the anterolateral approach.
   • Provides good exposure to both middle and distal 1/3 humeral shaft fractures.
2. Treatment of osteomyelitis.
3. Biopsy and excision of tumors.
4. Treatment of nonunion of fractures.
5. Exploration of the radial nerve in the spiral groove.
6. Insertion of retrograde humeral nails .

A study found that the anterolateral approach showed an advantage over the posterior approach to the humerus for treating simple humeral mid-shaft fractures.

Position of the Patient

• Prone position with arm on arm board, abducted 90 degrees.
• Lateral position with arm over the top of the body.

A sandbag should be placed under the shoulder of the side to be operated on, and the elbow should be allowed to bend and the forearm to hang over the side of the table.

Landmarks and Incision

• Landmarks:
  1. The Acromion.
  2. The Olecranon fossa.
• Incision:
  •  Longitudinal Incision in the midline of the posterior aspect of the arm from 8 cm distal to the acromion to the olecranon fossa.

Internervous plane

• There is no internervous plane for posterior approach to the humerus, it is a muscle splitting approach through the heads of the triceps brachii muscle which are supplied by the radial nerve.

• Because the nerve branches enter the muscle heads relatively near their origin and run down the arm in the muscle’s substance, splitting the muscle longitudinally does not denervate any part of it.
• In addition, the medial head (which is the deepest head) has a dual nerve supply consisting of the radial and ulnar nerves; splitting the medial head longitudinally does not denervate either half

Superficial dissection

• Fascia should be split in line with incision.

Deep dissection

• Split the fascia between the long and lateral head of the triceps muscle:
  • Lateral head is retracted laterally and the long head is retracted medially.
• Radial nerve will be identified along with the profunda brachii vessels in the spiral groove:
  • The radial nerve runs just proximal to the medial head of the triceps muscle which lies below the other two heads in the spiral groove.
  • Often times a tourniquet is beneficial until the nerve is identified.

Approach Extension

Posterior Approach to the Humerus can be extended through:

Proximal Extension:

• The bone cannot be exposed effectively above the spiral groove using the posterior approach. At this point, the deltoid muscle (which is the outer layer of the musculature) also crosses the operative field.
• More proximal exposures should be accomplished by the anterior route.

Distal Extension: 

• The skin incision can be extended distally over the olecranon; deepening the approach provides access to the elbow joint via an olecranon osteotomy.

Dangers

The structures at risk during 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 lower third of the arm.
• Vessels
  • The profunda brachii artery lies with the radial nerve in the spiral groove and is similarly vulnerable to damage.

Related Anatomy

Triceps Muscle

The triceps muscle has two layers.

1. The outer layer consists of two heads: the lateral head arises from the lateral lip of the spiral groove, and the long head arises from the infra-glenoid tubercle of the scapula.
2. The inner layer consists of the third head, the medial (or deep) head, which arises from the whole width of the posterior aspect of the humerus below the spiral groove all the way down to the distal fourth of the bone.

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

References

• Surgical Exposures in Orthopaedics book – 4th Edition
• Campbel’s Operative Orthopaedics book 12th
• Li Y, Tian Q, Leng K, Guo M. Comparison of the Posterior and Anterolateral Surgical Approaches in the Treatment of Humeral Mid-Shaft Fractures: A Retrospective Study. Med Sci Monit. 2020 Jul 8;26:e924400. doi: 10.12659/MSM.924400. PMID: 32639953; PMCID: PMC7366785.