The AO classification divided into type A (extra-articular—unifocal, lowest AVN risk), type B (extra-articular—bifocal, higher AVN risk), and type C (articular, highest AVN risk) also seems to have a rather low inter- and intraobserver agreement (Fig. 2.2). Recently, a system known as “binary classification” has been proposed by Hertel who associates the risk of ischemia to the pattern of fracture. As shown in Fig. 2.3, the Hertel classification is based on an analysis of fracture planes as opposed to fragment numbers as in Neer/Codman classification:
Fig. 2.2
AO classification
Fig. 2.3
Hertel classificationH head humerus, GT greater tuberosity, LT lesser tuberosity, S shaft humerus (Reproduced with permission from Hertel et al. [7])
1.
Between the greater tuberosity and the head
2.
Between the greater tuberosity and the shaft
3.
Between the lesser tuberosity and the head
4.
Between the lesser tuberosity and the shaft
5.
Between the lesser tuberosity and the greater tuberosity
2.3 Understanding the Fracture
The management of every kind of proximal humerus fracture makes mandatory the analysis of some essential features, depending on the patient, fracture’s patterns, and bone quality:
1.
Age and functional requirements of the patient
2.
Integrity of calcar and medial hinge
3.
Degree of displacement of tuberosities
4.
Head impaction into valgus or varus
5.
Displacement of humeral shaft
6.
Head splitting or glenohumeral dislocation
7.
Bone quality (comminution of tuberosities and surgical neck)
2.3.1 Age and Functional Requirements of the Patient
The age and functional requirements of the patient guide us to decide for the best treatment. The treatment could be simply a Desault bandage in the elderly patient with restricted or null functional requirements and poor bone quality.
The patient’s functional requirements are an important element that must guide us in the choice of treatment. Nowadays we often find ourselves in front of an overweighing old man who still plays important daily activities such as driving, swimming, gardening, etc.
No less important is to consider the affected side: dominant or not.
2.3.2 Integrity of Calcar Medial Hinge
The evaluation of the fracture line extension length on the metaphyseal head is essential to assess the integrity of the calcar zone. Frequently, a head impaction into valgus or into varus has been observed. The head rotates into valgus when the greater tuberosity displaces posteriorly and superiorly and the below cancellous bone is compacted.
It is not uncommon that fractures with valgus head impaction have a low risk of osteonecrosis because the medial periosteal hinge is preserved.
Most proximal humerus fractures occur in elderly patients with osteopenia; this can explain the high degree of comminution, the size of cancellous defects due to the impaction, and the potential risk for fixation failure and fracture redisplacement. The knowledge of differences of either bone quality or mineral density in different regions of proximal humerus guides us in reaching the best implant fixation and decreasing the potential failure [8] (Fig. 2.4).
Fig. 2.4
Valgus head impaction fracture with a medial periosteal hinge preserved
2.3.2.1 Humeral Head Blood Supply
The major blood supply is from the anterior and posterior humeral circumflex arteries. The anterolateral branch of the anterior circumflex artery ascends parallel to the lateral aspect of the biceps tendon and through its terminal branch, the arcuate artery; it enters the head at the junction of the bicipital groove and the greater tuberosity and perfuses the head. Most contributions to the humeral head blood supply arise from the posterior humeral circumflex, reaching the humeral head via tendo-osseous anastomoses of the posterior and inferior capsule [9, 10].
This kind of knowledge is mandatory to understand and predict the probability of the most dangerous complication of proximal humerus fractures: osteonecrosis. It is a well-known condition which develops when fracture location and displacement compromise the humeral head vascularization. It may be associated with permanent disability. The risk of humeral head ischemia is related to fracture morphology [7] (Fig. 2.5).
Fig. 2.5
Posterior humeral circumflex artery and posterior capsule
Good ischemia predictors are (Fig. 2.6):
Fig. 2.6
Blue line intact and metaphyseal head extension <8 mm are good ischemia predictors
Length of metaphyseal head extension (accuracy 0.84 for calcar segments <8 mm)
Integrity of the medial hinge (accuracy 0.79 for disrupted hinge)
Basic fracture pattern (accuracy 0.7 for fractures comprising the anatomic neck)
Poor ischemia predictors are:
Angular displacement of the head (accuracy 0.62 for angulations over 45 deg)
Extent of displacement of the tuberosities (displacement over 10 mm: accuracy 0.61)
Glenohumeral dislocation (accuracy 0.49)
Head-split components (accuracy 0.49)
The integrity of the medial hinge is also very important to plan reduction and synthesis. In fact, the hinge integrity makes definitely easier reestablishing the correct anatomy. In the case of a valgus impacted head opposite to a preserved medial hinge, in order to perform the reduction, it will be easier to bring the head in anatomic position by exploiting the medial hinge effect (Fig. 2.7). The management of the head can be extremely difficult and could fail, whenever the medial hinge is interrupted. In the event of a varus head, the medial hinge is more frequently interrupted.
