Fig. 21.1
AO classification of the humeral shaft fracture
Several mechanisms could be a cause of a humeral shaft fracture, and the mechanism normally correlates with the fracture type:
A flexion trauma usually leads to a transverse fracture.
A twisting trauma could lead to a spiral fracture.
A mix of bending and twisting could lead to an oblique fracture.
High loads, especially in axial direction, could lead to complex and epiphyseal fracture.
The most important biomechanical aspect in humeral shaft fractures is where the fracture occurs: if it is between the insertion of the deltoid and the pectoralis major, the proximal fragment will be displaced medially and adduced by the traction of the fibers of the pectoralis (Fig. 21.2); if it is under the insertion of the deltoid, the proximal fragment will be displaced laterally and abducted by the traction of the same deltoid (Fig. 21.3).
Fig. 21.2
Displacement mechanism #1: pectoralis major traction and adduction of the proximal fragment
Fig. 21.3
Displacement mechanism #2: deltoid traction and abduction of the proximal fragment
Although any randomized clinical trial does not exist confirming a safe, proven, and effective treatment, the first eligible treatment for these fractures is the conservative one [3]. Following recent meta-analyses, about 94–97 % of the humeral shaft fractures heal in cast or brace [4]; in low-energy fractures, this percentage could grow up to 99 % [5].
In fact, the humerus can tolerate deformities of 20° in procurvatum and 30° in varus, shortening and translation up to 4 and 1 cm, respectively [6].
The remaining fractures are treated surgically, following AO indications with plating, with anterograde or retrograde nailing, and in some selected cases with external fixation.
21.1.3 Surgical Indications
Commonly accepted criteria for surgical treatment, with both open and closed reductions, are [7]:
Exposed fractures
Severe radial nerve injuries
Multifragmentary fractures
Bilateral fractures or polytrauma
Stabilization in intensive trauma care unit
Obese patients
Common indications for external fixation in humeral shaft fractures are:
Bilateral fractures
Poor cutaneous conditions
Infections and infected nonunions
Malunions
Posttraumatic radial nerve palsy
Severe displacement of the fracture
Open fractures or comminuted fractures
Failure of a previous treatment
Although these are commonly accepted indications, a standardized decision-making guideline does not exist for any surgical treatment: we suggest that external fixation, in the presence of an expert surgeon, could be a safe option for the greatest part of the humeral shaft fractures. External fixation is often a more safe, rapid, and low-complication-rate procedure; nevertheless, it needs a high patient compliance and an accurate surgical procedure.
21.1.3.1 External Fixation Technique
In our experience, external fixation has to be used more commonly, with the purpose of a simple management and a rapid mobilization. The advantage of this technique (which if performed by an experienced surgeon takes a little surgical time) is giving an excellent stability with minimizing soft tissue damage. Furthermore, the possibility of callus distraction and compression and alignment correction during the treatment could lead to excellent results [8, 9].
Considering these factors, our indication in acute trauma is given when the patient presents a severe nerve injury, exposed fractures, and bilateral or comminuted fractures but also in young patients with simple fractures.
Other indications could be given in chronic conditions like pseudarthrosis , both septic and non-septic.
Three steps are mandatory for a good reduction and positioning of a humeral external fixator: patient position, pin insertion, and subsequent reduction:
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1.
Patient position—the patient lies supine, with the head immobilized, under general or selective anesthesia: a support has to be mounted under the humerus; surgical zone (in the absence of further lesions) goes from the axilla to the elbow included. Draping may leave free motion range to the entire arm. No fixed traction is needed (Figs. 21.4 and 21.5).
