The Neer classification of proximal humeral fractures is probably the most frequently used system along with the AO classification of proximal humeral fractures. The terminology and factors which influence the classification are essential for the utility of radiology reports of proximal humeral fractures.

Terminology

The two main components of the classification are the number of fracture parts and the displacement ^1,4-6.

Fracture parts

The Neer system divides the proximal humerus into four parts and considers not the fracture line, but the displacement as being significant in terms of classification.

The four parts are:

1. humeral head

2. greater tubercle

3. lesser tubercle

4. humeral shaft

Displacement

Displacement is on a per-part basis. A fracture part is considered displaced if angulation exceeds 45°, or if the fracture is displaced by more than 1 cm ¹.

The simplest displaced fracture which is possible, therefore, is a two-part fracture. A minimally displaced fracture, even one that includes multiple fracture lines, however, merely constitutes a type I, one-part fracture.

Classification

The Neer classification has been variably adapted by multiple authors. The classification consists of four major groupings, based on the number of displaced parts. Neer added a fifth group ⁹.

One-part fracture

• fracture lines involves 1 to 4 parts

• none of the parts are displaced (i.e. <1 cm and <45°)

These non-displaced or minimally displaced fractures account for ~70-80% of all proximal humeral fractures and are almost always treated conservatively ^6,7.

Two-part fracture

• fracture lines involves 2 to 4 parts

• one part is displaced (i.e. >1 cm or >45°)

Four possible types of two-part fractures exist (one for each part):

1. surgical neck: most common

2. greater tubercle

   • frequently seen in the setting of anterior shoulder dislocation ⁸

   • a lower threshold of displacement (>5 mm) has been proposed ⁸

3. anatomical neck

4. lesser tubercle: uncommon

These fractures account for approximately 20% of proximal humeral fractures ⁶.

Three-part fracture

• fracture lines involves 3 or 4 parts

• two parts are displaced (i.e. >1 cm or >45°)

Two three-part fracture patterns are encountered ⁷:

1. greater tubercle and shaft are displaced with respect to the lesser tubercle and articular surface which remain together

   • most common three-part pattern

2. lesser tubercle and shaft are displaced with respect to the greater tubercle and articular surface which remain together

These fractures account for approximately 5% of proximal humeral fractures ⁶.

Four-part fracture

• fracture lines involves all 4 parts

• three parts are displaced (i.e. >1 cm or >45°) with respect to the 4^th

These fractures are uncommon (<1% of proximal humeral fractures) ⁶.

This pattern has poor non-operative results, and as the articular surface is no longer attached to any parts of the humerus which are attached to soft tissues. This pattern has a high incidence of osteonecrosis ⁷.

These fractures require operative management.

Valgus impacted four-part fracture

This type of four-part fracture is considered its own category and has a different prognosis than typical four-part fractures ⁹.

History and etymology

The Neer classification was created by Charles S Neer II, an American orthopaedic surgeon and professor. Dr Neer founded and was the first President of the American Shoulder and Elbow Surgeons.