6.2.2 Humerus, shaft
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1 Introduction—epidemiology
Humeral shaft fractures make up approximately 1% of all fractures. Typically, they are the result of direct trauma but also occur in sports where rotational forces are greater, for example, baseball or arm wrestling [1]. Fractures of the middle or distal third of the shaft put the radial nerve at risk. In a small percentage of cases humeral shaft fractures are associated with a vascular injury. Open fractures are uncommon but can represent serious injuries particularly if associated with crushing in industrial injuries.
2 Evaluation and diagnosis
2.1 Case history and physical examination
A careful history, taking into account the mechanism of injury, will help decide the likelihood of other associated nonbony injuries and the possibility of injuries in other body regions. An evaluation of concurrent disease and normal activity levels is an essential part of the patient′s assessment.
The upper arm should be examined for swelling, bruising, deformity, and the presence of open wounds, remembering that these can be posterior or medial. The entire limb must be carefully examined for vascular and neurological impairment. Evaluation of the radial and posterior interosseous nerves for a “primary nerve injury” is essential before any reduction maneuver [2].
2.2 Imaging
Radiographic images are obtained in two perpendicular planes. The x-rays should be full-length showing the shoulder and elbow joints on the same film to allow alignment and rotation to be assessed. If the fracture extends into the shoulder or elbow joints, intraoperative traction views or a computed tomographic scan with or without surface/volume rendering may be helpful.
3 Anatomy
The humeral shaft extends from the surgical neck proximally to the humeral condyles distally. It has a cylindrical shape proximally, is conical in its middle section, and in the distal third becomes dramatically flattened in the coronal plane. The humeral head is just proximal to and in line with the medullary canal. The humeral condyles are not in line with the distal end of the canal but angled 45° anteriorly. Distally, the triangular dorsal surface is bound by the medial and lateral supracondylar crests and the olecranon fossa.
The arm muscles are divided into anterior flexor and posterior extensor compartments. If the fracture is situated between the rotator cuff and the pectoralis major muscle, the humeral head will be abducted, flexed, and externally rotated relative to the glenoid and the shaft pulled into extension, abduction, anterior and medial translation relative to the head. If the fracture lies between the pectoralis muscle and the deltoid insertion, the proximal fragment will be adducted and the distal fragment laterally displaced. In fractures distal to the deltoid insertion, the proximal fragment will be abducted. In the case of a fracture proximal to the brachioradialis and extensor muscles, the distal fragment will be rotated laterally. Distal fractures tend to fall into varus.
The brachial artery and vein as well as the median and ulnar nerves traverse the anterior compartment medial to the coracobrachialis muscle proximally and the brachialis muscle distally.
The axillary nerve and the posterior circumflex humeral artery originate posteriorly and wind round the surgical neck about 5–6 cm below the lateral edge of the acromion. The radial nerve runs posteriorly through the triceps brachii muscle, occupying the radial groove in the midshaft area ( Fig 6.2.2-1 ) [3].
At the junction of the middle and distal third of the humerus, about a handbreadth above the lateral epicondyle, the radial nerve perforates the lateral intermuscular septum. Here the nerve is less mobile and more vulnerable when displacement of fragments occurs.
At this level the radial nerve may also have split into a leash of fibers. The division of the radial nerve into posterior interosseous and superficial radial nerves can occur high in the spiral groove with the two nerves running together. Care must be taken to ensure all parts of the nerve are under the surgeon′s control.
4. Classification
4.1 AO/OTA Fracture and Dislocation Classification
Classification of fractures of the humeral shaft uses (as for any long bone) the AO/OTA Fracture and Dislocation Classification. Humerus: bone 1, shaft; segment 2. Fracture severity increases from 12A1: a simple spiral fracture with high contact area to 12C3: a multifragmentary fragmentary segmental fracture ( Fig 6.2.2-2 ).
4.2 Other key classifications
There are no other helpful global classifications although there are some eponymous fractures, such as the low spiral distal shaft fracture, the Holstein-Lewis fracture, which is often associated with a radial nerve lesion.
5 Surgical indications
There are well-established absolute and relative indications for surgical stabilization ( Table 6.2.2-1 ). The patient′s age, fracture pattern, associated injuries or diseases, as well as the ability to comply with treatment; all need to be considered. Plate fixation can be used for almost all humeral fractures and is the best option for fractures of the proximal or distal shaft, particularly if there is an intraarticular extension.
Intramedullary (IM) nails are the best option for pathological or impending pathological fractures of the humeral shaft.
Numerous methods of nonoperative management for humeral shaft fractures have been described, including casting, splinting, and Velpeau immobilization.
Functional bracing is the most widely accepted treatment of humeral shaft fractures ( Fig 6.2.2-3 ).
Good to excellent outcomes have been reported with 95% union rates [4, 5]. Moderate angulation (< 20° anterior and 30° varus angulation), rotation (< 40°), and shortening (< 3 cm) are well tolerated functionally. Patients are generally becoming less tolerant of significant cosmetic deformity, primarily varus and shortening, particularly if shortening leads to a need for significant alteration of clothing.
6 Preoperative planning
6.1 Timing of surgery
There are rarely any indications for emergency surgery in humeral shaft fractures other than with an associated vascular injury. Open fractures should be managed expeditiously. Otherwise, these fractures are best treated by an experienced surgeon in a timely fashion.
6.2 Implant selection
Implants have to be patient-specific. Larger patients need the dynamic compression plate (DCP) or locking compression plate (LCP) 4.5 while most patients require the LCP 3.5. In all cases, selected implants should be 8 holes long or longer. The upper extremity has a large rotational excursion and because of this, it is wise to use a long plate to maximize the length of the moment arm ( Fig 6.2.2-4 ). The implants fit well on either posterior, anterior, medial, or lateral surfaces. In most circumstances nonlocking screws can be used in the combination holes of the LCP. However, in poor quality bone locking screws or blade plates can also be utilized. In the humerus, locking head screws must always be bicortical due to large rotational forces. Careful planning and application of AO principles are required to ensure a cogent construct, whether using the plate in compression, protection, or bridging mode.
Humeral shaft fractures extending from periarticular fractures are often optimally plated using anatomically specific precontoured plates, such as the thicker “metaphyseal” version of the PHILOS system or the distal plates 3.5 which are as thick and strong as plates 4.5 but have 3.5 mm screws (metaphyseal plate 3.5 for distal medial humerus or extraarticular distal (lateral) humeral plate).
The cannulated expert humeral nail is available in various diameters and various lengths. Both parameters must be determined before nail insertion. A radiographic ruler should be on hand to measure length and diameter intraoperatively. The long version of the Multiloc nail can be used. The proximal insertion points are different for both nails and both require free-hand distal locking but have jigged proximal locking.
6.3 Operating room set-up
6.3.1 Anterior approach
After positioning the patient and applying an arm tourniquet, the whole arm including fingertips are disinfected with the appropriate antiseptic. Disinfection fluids should not run under the tourniquet.
Sterile drapes should be applied to ensure a waterproof environment for the operative site. Since a drape around the hand can be bulky, it may be more suitable to wrap the hand in a sterile stockinette fixed with an adhesive tape or a clear adhesive plastic drape ( Fig 6.2.2-5 ). Drape the image intensifier.
The surgeon sits facing the patient′s head, the assistant opposite, and the operating room personnel at the end of the arm table. The image intensifier is brought in from the assistant′s side of the arm table. The assistant has to move temporarily when imaging. The image intensifier display screen is placed in full view of the surgical team and the radiographer ( Fig 6.2.2-6 ).
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