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- 47-1.
Complex humerus shaft fracture.
Introduction: Scope and Purpose
Fractures of the humeral shaft account for approximately 3% of all fractures and represent an incidence of 19 per 100,000 person-years. The occurrence shows a bimodal age distribution with a peak observed in the third decade mainly in men as a result of violent high-velocity injuries and a larger peak in the seventh decade mainly occurring in women, generally resulting from simple fall and attributed to osteoporotic bone. The primary causes of fracture include traffic accident, accidental falls, and violent injury. In a consecutive series of 249 fractures, fewer than 10% were open.
Relevant Anatomy
The humerus shaft is the longest bone of the upper extremity. The proximal cylindrical aspect flattens in distal direction and is more triangular shaped in the supracondylar area. Proximally at the transition from the humerus head to the shaft lie the lesser and the greater tubercle where the rotator cuff is attached. The lesser tubercle continues distally in the crest of the lesser tubercle, and the greater tubercle continues distally in the crest of the greater tubercle. In between lies the intertubercular groove containing the long biceps tendon. The crest of the greater tubercle divides the anterolateral from the anteromedial surface. The medial and lateral margins (the proximal continuation of the medial and lateral epicondyle) define the posterior surface. The deltoid tuberosity, a rough area on the anterolateral aspect of the humerus, serves as the attachment of the deltoid muscle and is just proximal and nearly parallel to the groove of the radial nerve. The spiral groove for the radial nerve runs on the dorsal aspect of the humerus and can be found 20 cm proximal to the medial epicondyle and 14 cm proximal to the lateral epicondyle. The three muscles brachialis, triceps, and brachioradialis origin and three muscles pectoralis major, deltoid, and coracobrachialis insert from humerus diaphysis. These muscles are innervated by the musculocutaneous, radial, or axillary nerve. As an exception, the brachialis muscle receives innervation from two nerves, the musculocutaneous (medial part) and radial (lateral part) nerve. So splitting the brachialis muscle medially does not jeopardize the innervation. In two-thirds of all humeri, one single nutrient canal lies in a small area on the medial aspect of the distal half of the middle third of the humerus. It can be assumed that the main blood supply will enter this point.
Mechanism of Injury and Biomechanics
In contrast to the lower extremity, the upper extremity experiences only few axial loads, and rotational forces dominate. This different load shearing requires an adjustment in osteosynthetic treatment. Plate osteosynthesis needs additional screws on both fracture sides to compensate for these rotational forces.
The degree of displacement is influenced by the height of fracture level. In fractures above the insertion of the pectoralis muscle, the proximal fragment tends to rotate externally and abduct. The distal fragment dislocates medially and anteriorly. Fractures above the deltoid muscle insertion adduct the proximal fragment and proximalize the distal fragment. With the fracture just below the insertion of the deltoid muscle, the proximal fragment tends to abduct. Generally, moderate malalignment (rotation, length, and axis) is well tolerated by the humerus, and a maximum of 15 degrees’ malrotation, 20 degrees’ anterior angulation, and 30 degrees’ varus as well as shortening of less than 3 cm are still acceptable.
As a rule of thumb, bending forces create transverse fractures, and torsion forces result in a spiral fracture. The combination of both forces creates an oblique fracture with or without a butterfly fragment. Axial compression either fractures the proximal or the distal part of the humerus.
Evaluation
Examination
In all cases, brachial plexus injuries must be ruled out. Neurovascular injuries (mainly lesions to the radial nerve) frequently occur in humerus shaft fracture, making the preoperative clinical evaluation of utmost importance. Radial nerve impairment is best recognized by examination of the extensor carpi radialis longus function. An inability to oppose the thumb indicates a median nerve lesion, and an inability to spread the fingers indicates an ulnar nerve injury.
An absent radial pulse is the best clinical diagnosis for a lesion of the brachial artery mainly in the proximal and distal third where the artery runs in proximity to the humerus shaft. The degree of ischemia depends on the level of the arterial lesion. Injuries proximal to the profunda brachii artery show a high rate of ischemia and limb loss.
Imaging
Standard radiologic assessment is usually sufficient for the diagnosis of humerus shaft fracture. Analogous to other fractures, computed tomography (CT) and three-dimensional reconstruction can facilitate visualization. If desired, CT angiography can help to localize vascular impairment.
In pathologic fractures, additional CT, technetium-labeled bone scan, magnetic resonance, or angiography might be necessary for preoperative planning and eventual embolization ( Fig. 47-1 ).
Diagnosis and Classification
The classification follows the Müller Arbeitsgemeinschaft für Osteosynthesefragen (AO) classification of long bones. The bone number is 1, and the diaphyseal fracture location is 2 (AO 12). Additional numbers and letters address the further fracture characteristics. Simple fracture patterns are A type, wedge are B type, and complex are C type ( Fig. 47-2 ). Spiral fractures of the distal third of the humerus shaft are called Holstein-Lewis fractures and are commonly associated with neurapraxia of the radial nerve.
Management
Disorder or Injury
Emergent Treatment
Immediate emergent treatment is indicated in concomitant vascular injuries; even so, limb amputation rates are low, which is probably related to the rich collateral supply.
In open fractures, early soft tissue and bone débridement is essential to decrease the infection rate. The timing is still under debate and a strict “6-hour rule” has little support in the existing literature.
Indications for Definitive Care
The humerus shaft fracture was historically mainly treated nonoperatively with good union rates and shoulder as well as elbow function. Perioperative complications of concern included iatrogenic radial nerve damage, nonunion, and infection. Although nonoperative treatment is successful in many fractures, several variables favor operative treatment. Denard and colleagues compared in a retrospective study 213 patients and showed a higher nonunion rate with conservative therapy. There were no differences in radial nerve palsy, infection rate, range of motion, or time to union. Comparing functional bracing and intramedullary (IM) nail fixation found, apart from better free shoulder mobility in the bracing group, no significant differences in shoulder function or fracture alignment. Comparing functional bracing and plate fixation for extraarticular distal-third diaphyseal humeral fractures, operative treatment achieved more predictable alignment and potentially quicker return of function but risks iatrogenic nerve injury and infection and the need for reoperation. Functional bracing was associated with skin problems and varying degrees of angular deformity, but function and range of motion were similar and usually excellent. Nonoperative management of humeral midshaft fractures can be expected to have similar functional outcomes and patient satisfaction at 1 year despite an early benefit to operative treatment.
Operative intervention may include compression plate fixation, IM nailing, or external fixation, depending on the properties of the fracture and other associated injuries.
Pathologic Fractures.
Pathologic fractures need special consideration concerning the treatment options. These fractures that are caused by metastatic tumors are commonly seen in patients with advanced tumor disease. In adults, metastatic disease is the most common malignant neoplasm of bone. Closed reduction and IM fixation, and open reduction and internal plate fixation are the most widespread methods for the stabilization of these fractures. Sarahrudi and colleagues analyzed 56 pathologic humerus shaft fractures mainly related to breast, bronchial, or kidney cancer. Their results show that patients with a metastatic fracture of the humerus survive an average of 2.8 months after pathologic fracture. Conservative therapy resulted in nonunion and inadequate pain relief. For patients in advanced stage of metastatic disease, they recommended closed IM fixation and irradiation because of faster and less invasive procedure. Patients with better prognoses as well as patients with solitary metastasis of the humerus should undergo open reduction curettage of the lesion, cementation, and plate fixation ( Fig. 47-3 ).
Indications for operative treatment are summarized in Table 47-1 .
| Indications |
|---|
| Fracture Pattern |
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| Associated Injuries |
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Nonoperative Treatment
About 30% to 90% of humeral shaft fractures are treated conservatively, with functional bracing being the most common nonoperative option for the majority of fractures. After an average of 9 days, a hanging arm cast or a coaptation splint is replaced by a prefabricated brace ( Fig. 47-4 ). Sarmiento and colleagues reported nonunion in 6% of open fractures (mostly gun shot wounds) and fewer than 2% in closed fractures using functional bracing. In their patient cohort, 70% had less than 5 degrees of shaft angulation, 90% had less than 10 degrees’ shoulder function impairment, and 92% had less than10 degrees’ elbow function impairment compared with the uninjured side. Bracing of a humerus shaft fracture can be challenging in short and obese patients, especially in fractures of the proximal third ( Fig. 47-5 ). Several other nonoperative treatment modalities are reported. The coaptation splint supports the humerus shaft in a U-type fashion. It is mainly indicated in nondisplaced fractures, but close follow-up is necessary to identify potential pitfalls such as axillary irritation, shortening of the fracture, and displacement. The elbow range of motion is limited. The hanging arm cast was introduced by Caldwell. The cast involves the elbow and allows a distraction of a comminuted humerus shaft fracture. This cast is now mainly used for initial reduction of a humerus shaft fracture and is replaced with a functional brace after the first week. Overdistraction of the fracture is the main risk with this technique ( Fig. 47-6 ). Secondary operations in up to 15% because of delayed healing are published. The patient must also sleep semierect to avoid supporting the elbow while sleeping. Two cohort studies compared patients treated with the functional brace method and with U-cast method. No statistically significant differences comparing nonunion were found, although delayed union was more common after fracture brace treatment. Elbow extension was significantly greater in the brace group; however, the number of patients with varus deformity of less than 5 degrees was significantly greater in the brace group compared with the U-cast method.
Surgical Treatment
Surgical Anatomy.
From the surgical neck proximally to the condyles distally, several anatomic characteristics complicate the surgical approach. About 5 to 6 cm below the acromion on the inner surface of the deltoid muscle, the axillary nerve and the circumflex humeral artery wind from posterior to anterior around the humerus ( Fig. 47-7 ). These structures might be injured with proximal humerus nail interlocking or minimally invasive approaches. The radial nerve runs on the posterior aspect of the humerus proximal to the insertion of the medial head of the triceps muscle. Distally, the radial nerve enters the intermuscular septum and is embedded between the brachial and the brachioradialis muscle (key structure), which should be protected while splitting the brachial muscle. The radial nerve is at risk with distal humerus nail interlocking and dorsal plate osteosynthesis.
