Midshaft humerus fractures in adults

INTRODUCTION — Fractures of the humerus can occur proximally, at the shaft, or distally. The majority of both proximal and midshaft humerus fractures are nondisplaced and can be treated conservatively (nonsurgically).

Nonstress fractures of the midshaft (diaphysis) of the humerus will be reviewed here. Stress fractures of the humeral shaft and proximal humeral fractures are discussed separately. (See "Stress fractures of the humeral shaft" and "Proximal humeral fractures in adults".)

CLINICAL ANATOMY — The humerus is the largest bone in the upper extremity. The proximal humerus articulates with the glenoid of the scapula to form the shoulder joint (figure 1). The muscles and tendons of the rotator cuff, the acromion, and ligamentous attachments such as those between the coracoid process of the scapula and the acromion, serve to both stabilize the glenohumeral articulation and provide for a wide range of motion of the shoulder joint. The distal humerus articulates with the radius and ulna at the elbow.

The greater tuberosity, located lateral to the humeral head and on the superior aspect of the humerus, provides the attachment for three of the rotator cuff muscles: supraspinatus, infraspinatus and teres minor (figure 2). The lesser tuberosity of the humerus is located on the anterior surface of the humerus and provides the attachment for the subscapularis muscle. For the purposes of fracture classification, the lesser tuberosity marks the boundary between the proximal humerus and the midshaft.

The humeral shaft supplies the attachment for a number of powerful muscles (figure 3). The pectoralis major muscle inserts on the proximal shaft while the deltoid muscle attaches to the midshaft. The biceps brachii and triceps muscle groups attach further distally.

The tendon of the long head of the biceps brachii muscle passes between the lesser and greater tuberosities as it courses from its origin on the superior portion of the glenoid to its insertion on the radius (figure 4).

The blood supply to the humeral shaft is supplied by the axillary and brachial artery, the latter branches to form the radial and ulnar artery (figure 5 and figure 6 and figure 7). The vascular supply can be disrupted if there is considerable displacement of shaft fragments.

Innervation of the muscles in the posterior compartment of the arm and forearm is provided by the radial nerve. The radial nerve enters the arm medial to the humerus and anterior to the long (medial) head of the triceps muscle and travels inferolaterally, moving around and adjacent to the humeral shaft, in the radial groove (figure 8 and figure 6). Thus, the radial nerve is susceptible to injury when there is significant displacement of mid to distal humeral shaft fractures [1]. Median and ulnar nerve injuries are uncommon with such fractures [2].

EPIDEMIOLOGY AND RISK FACTORS — Midshaft humeral fractures account for about 2 percent of all fractures [3]. They occur in all age groups, but show a bimodal distribution: The first peak is seen in the third decade in males and is often associated with high velocity trauma; the second peak is noted in females in the seventh decade and is associated with low velocity falls [1]. An observational study of 401 humeral shaft fractures noted that 68 percent resulted from a simple fall and 90 percent overall were due to trauma [1]. Trauma, increasing age, and osteoporosis are known risk factors. (See "Falls in older persons: Risk factors and patient evaluation" and "Falls: Prevention in community-dwelling older persons".)

MECHANISM OF INJURY — Midshaft fractures typically result from trauma such as a direct blow or bending force to the humerus and, less commonly, from a fall on an outstretched hand or elbow. Midshaft fractures may also result from strong muscle contractions such as in high-velocity throwing or arm wrestling. There is some debate whether this occurs solely from a violent muscle contraction or requires an underlying stress fracture associated with the muscle contraction. A study of 90 recreational baseball players with midshaft humeral fractures concluded that these fractures are caused by the accelerated phase of throwing, and can occur in any recreational baseball player who tries to make a hard throw [4].

SYMPTOMS AND EXAMINATION FINDINGS — Patients with midshaft humeral fractures typically present with severe arm pain in the area of the mid-arm but may have referred pain to the shoulder or elbow. Swelling and ecchymosis is often apparent shortly after the injury. The presence of abrasions or lacerations should be noted. If medicolegal circumstances warrant and the patient agrees, photographs of the injured arm can be obtained.

There is significant tenderness to palpation and crepitus may be noted at the fracture site. Shortening of the upper arm suggests the presence of significant humeral shaft displacement. Careful examination, including inspection and palpation of the shoulder and elbow, are important to assess for other injuries.

The initial evaluation of midshaft humerus fractures includes a detailed neurovascular exam of the affected arm, including careful assessment of the radial and ulnar arteries and the function of the radial, median, and ulnar nerves.

The radial nerve is the nerve most commonly injured by midshaft humerus fractures. Injury to the radial nerve results in weakness of wrist, finger, and thumb extension and some weakness of elbow supination. Motor function can be tested by giving the “thumbs up” sign (picture 1) and testing resisted extension of the thumb (picture 2). Sensory loss may be present on the dorsum of the hand and is easily tested at the dorsal web space between the thumb and index finger.

Injury to the median nerve is uncommon following midshaft humeral fractures, but, when it occurs, results in weakness of the flexor muscles of the hand and loss sensation on the palmar surface of the thumb and the index and middle fingers. The largest branch and most commonly injured portion of the median nerve is the anterior interosseus nerve. It lacks a sensory component and results in loss of hand and finger flexion. This is best evaluated by having the patient give an “OK sign,” which tests the flexor pollicis longus (thumb flexion) and flexor digitorum profundus (DIP flexion of the index finger) (picture 3). Anterior interosseus syndrome results in weakness or flattening of the “OK sign” due to loss of thumb and index finger flexion (picture 4).  

The ulnar nerve is seldom injured by midshaft humeral fractures. Injury to the ulnar nerve results in dysfunction of the dorsal and palmar interossei and an inability to abduct and adduct the fingers. This can be tested by asking the patient to make the “peace sign” (picture 5) and testing the strength of the interossei (picture 6).

DIAGNOSTIC IMAGING — Radiographs of the humeral shaft in an anteroposterior and lateral plane are necessary to evaluate the amount of angulation or displacement of the fracture. If physical examination cannot exclude injury to the shoulder and elbow, radiographs should include those joints as well.

Fracture patterns — Fractures of the humeral shaft can be spiral, oblique, or transverse. The AO North American classification system sorts each fracture in to three lettered categories (figure 9):

●A - Simple fractures (image 1)

●B - Wedge fractures

●C - Complex (comminuted) fractures

Depending on the location of the fracture, displacement of the proximal and distal fragments can occur.

●Fractures near the midpoint of the humeral shaft typically assume an apex lateral position. The proximal fragment is pulled laterally by the deltoid, while the distal fragment is pulled medially by the triceps and biceps. Fractures near the midpoint of the shaft are more likely than more proximal or distal fractures to shorten due to the strong pull of the biceps and triceps muscles.

●Shaft fractures that are located more proximally are angulated apex medially due to the medial pull of the pectoralis major muscle proximally and the lateral pull of the deltoid muscle distally.

ORTHOPEDIC CONSULTATION OR REFERRAL

Indications for surgical referral — Based on available evidence and broad clinical experience, approximately 70 to 80 percent of humeral shaft fractures can be treated non-surgically, but some require functional bracing or use of traction for adequate treatment [5]. Physicians without experience using hanging casts and functional braces should refer patients with humeral shaft fractures for orthopedic consultation and management.

Acceptable positioning for a midshaft humerus fracture includes [6-8]:

●Less than 20 degrees of anterior or posterior angulation

●Less than 30 degrees of varus angulation

●Less than 3 cm of shortening

●Less than 15 degrees of rotational deformity

Varus angulation of up to 10 degrees is common [9]. Fractures that exceed the limits of acceptable alignment should be referred for closed reduction or operative stabilization.

Immediate surgical referral is required for a midshaft humerus fracture associated with vascular injury and for open fractures. Other absolute indications for referral include:

●Fracture associated with articular injuries

●Brachial plexus injuries

●Ipsilateral forearm fractures (eg, floating elbow)

●Bilateral humerus fractures

●Pathologic fractures (eg, associated with bone tumor)

●Concomitant traumatic major non-humeral fractures (eg femur fracture)

●High-velocity gunshot injuries (depending on the extent of injury, may require immediate surgical consultation)

●Fracture associated with severe soft tissue injuries or significant skin involvement [10]

Displaced distal spiral shaft fractures (Holstein Lewis fractures) have a high association with radial nerve injury and are generally best referred for surgical evaluation, and possible exploration and repair [11].

We suggest referral for all humeral shaft fractures associated with radial nerve injuries at presentation. However, it remains uncertain whether operative intervention is necessary in all cases of radial nerve dysfunction following fracture manipulation. Approximately 75 to 90 percent of radial nerve injuries at presentation are neurapraxias that resolve without intervention [11].

Other relative indications for referral include:

●Transverse fractures that are relatively unstable and at a high risk of shortening

●Patient noncompliance

●An obese body habitus that may result in increased varus deformity

Surgery versus bracing — Multiple systematic reviews have found no evidence from high quality trials to determine whether surgery or bracing is the best management for humeral shaft fractures [12-14]. Subsequent randomized trials and observational studies described below suggest better outcomes for surgical management, but the results are not definitive:

●A randomized trial comparing open reduction and internal fixation (ORIF) using compression plating (n = 38) with functional bracing (n = 44) for closed, displaced humeral shaft fractures reported no significant differences in functional outcome, as determined by Disabilities of the Arm, Shoulder, and Hand (DASH) scores (a validated score assessing symptoms and function) [15]. However, 13 patients originally assigned to functional bracing required surgical treatment by 12 months, 11 for nonunion. Few other complications occurred.

●A randomized trial comparing minimally invasive bridge plating through an anterior incision with functional bracing in 110 patients reported a nonunion rate of 0 percent for the surgical group versus 15 percent for the bracing group [16]. The surgery group had statistically superior DASH scores at six months but not at one year.

●A randomized trial involving 60 patients comparing ORIF compression plating with functional bracing reported a shorter time to union in those treated with ORIF (13.9 versus 18.7 weeks) [17]. Differences in DASH scores and nonunion rates were not statistically significant.

●A retrospective study comparing results in 213 patients with a midshaft humerus fracture reported an 8.7 percent nonunion rate in those treated with a compression plate versus a 20.6 percent nonunion rate in those treated with bracing, while malunion rates were 1.3 versus 12.7 percent, respectively [13]. There were no differences in time to union, infection rates, or final range of motion. Radial nerve palsy was observed in 9.5 percent of the nonoperative group versus 2.7 percent of the surgical group, but all resolved. A subsequent retrospective study of 186 patients reported similar delayed union rates (19 percent) and similar rates of radial nerve injury (9 to 10 percent) in the operative and non-operative treatment group, although 5 percent of the radial nerve injuries occurred as a direct result of operative fixation [18].

INITIAL TREATMENT — Most humeral shaft fractures can be treated initially in a coaptation splint. Some spiral, oblique and comminuted fractures require traction, in addition to splinting, to achieve appropriate alignment.

Transverse fractures — Transverse fractures do not require traction and can be treated initially with a splint and standard sling. Initial splinting of humeral shaft fractures is commonly done with a coaptation (sugar tong) splint (figure 10). The splint is applied to the medial aspect of the upper arm in the upper portion of the axilla and extended down around the elbow, up past the deltoid to the top of the shoulder. Slight valgus molding of the splint can decrease varus malalignment. Ensuring the splint extends deep into the axilla, proximal to the fracture sight also helps to minimize varus angulation. (See "Basic techniques for splinting of musculoskeletal injuries", section on 'Sugar tong splints'.)

Spiral, oblique, and comminuted fractures — Some spiral, oblique, and comminuted fractures require a degree of traction to achieve adequate positioning. This can be accomplished by using a coaptation (sugar-tong) splint with a collar and cuff sling, or a hanging cast. Initial immobilization with a splint and collar and cuff sling is preferred to casting if there is substantial swelling present. Use of a hanging cast is appropriate for reducing apex medial, lateral, anterior, or posterior angulation, if there is minimal swelling and the patient can be relied upon to watch for symptoms and signs of constriction by the cast or the appearance of compartment syndrome. If appropriate alignment cannot be accomplished with these techniques, surgical referral is needed.

Sugar tong splint with collar and cuff sling — The weight of the arm and the plaster coaptation (proximal sugar tong) splint (figure 10) provide gentle traction when the elbow is unsupported and the cuff is placed at the wrist or distal forearm (figure 11).

Hanging cast — Application of a hanging cast (figure 12) is similar to that for a long arm cast. The elbow is placed in 90 degrees of flexion and the forearm in a neutral position. The proximal portion of the cast extends 2 cm above the fracture site. The cast should be hung from the neck to the distal forearm with the elbow left unsupported at all times (this requires sleeping sitting upright). The weight of the cast is to be no more than two pounds, which is equivalent to one made from three 4 inch (10 cm) wide and one 3 inch (7.5 cm) rolls of plaster [19].

Adjustments to the length of the neck strap and the distal attachment points can be made to adjust for angulation. In order for the hanging cast to provide traction or to provide a force to reduce fracture angulation, the cast must be unsupported except at the attachment point and the patient must be upright at all times. This means sleeping in an upright position.

FOLLOW-UP CARE — Follow-up is initiated on a weekly or biweekly basis until radiographic and clinical union have occurred. Typical healing time is 10 to 14 weeks [19].

Transverse humerus shaft fractures

Functional bracing — A functional brace is the preferred definitive treatment for transverse humerus shaft fractures and most other midshaft fractures. Swelling and mobility at the fracture site typically decrease enough after one to two weeks to allow a functional brace to be applied. Prefabricated braces of various sizes (such as the Sarmiento brace) can be used (picture 7A-B). The brace should be tightly applied and should extend above and below the fracture site. Compression around the fracture site can restore proper positioning and may stimulate early osteoblastic activity [20]. A cuff and collar sling can be used if some degree of traction is necessary.

Weekly follow-up with serial plain radiographs ensures adequate healing and confirms appropriate fracture alignment. Once the fracture is stabilized, patients are followed every two to three weeks until full healing is achieved, generally in 10 to 14 weeks.  

Rehabilitation — Within one week, patients start pendulum exercises. Pain determines the progression to increased shoulder motion exercises. In most patients the brace can be removed once callous formation is present and the fracture site is stable to manual stress. Aggressive exercises to improve the range of motion of the shoulder, elbow, and hand, and to strengthen the muscles of the affected limb, should follow. After brace removal, the patient is reevaluated every two weeks until adequate arm function is achieved.

Results with functional bracing — Although there are no head-to-head studies comparing hanging casts to functional bracing, most experts will use functional bracing rather than hanging casts if there is no significant shortening or displacement. The results that can be expected from functional bracing for humerus shaft fractures in the following case series are illustrative:

●In one series of 107 cases of closed humerus fractures treated with functional bracing, 82 percent of patients had 8 degrees or less of varus/valgus and/or anterior/posterior angulation after their fractures had healed and rehabilitation was completed [21]. In the few patients with greater angulation, no obvious functional impairment or cosmetic detriment was noted.

●Another study of 87 patients with humeral shaft fractures treated with functional bracing noted that 86 percent healed with no restrictions in the movement of their shoulder and elbow joints [20]. Subjectively, 95 percent of the patients were content with the functional treatment, 65 percent claimed to be pain free in their daily activities and at work, and 35 percent felt pain only when doing vigorous activities or heavy physical work.

●A study that included patients with both open and closed midshaft humerus fractures (620 total) who were treated in prefabricated functional braces, reported that 87 percent of patients had less than 16 degrees of varus deformity, and 81 percent had less than 16 degrees anterior angulation [6]. Nonunion rates were less than 2 percent in closed fractures, and 98 percent of patients had limitation of shoulder range of motion less than 25 degrees at the time of brace removal.

Displaced oblique or spiral humerus shaft fractures — Non-surgical patients with oblique or spiral humeral shaft fractures associated with displacement or shortening can be treated in a hanging cast or functional brace (see 'Hanging cast' above and 'Functional bracing' above). Initial follow-up is weekly and includes plain radiographs to ensure that no further displacement occurs and acceptable alignment is maintained. The hanging cast can be removed once callous formation is present on radiographs and the fracture is stable to manual stress.

Rehabilitation following use of hanging cast — Immediately after removal of the cast, patients should begin rehabilitation to regain shoulder and elbow mobility and upper extremity strength. The patient should be followed every two weeks to evaluate progress.

COMPLICATIONS — The most common complications associated with humeral shaft fractures are neurovascular compromise and nonunion. Other fracture complications are described separately. (See "General principles of fracture management: Early and late complications".)

Radial nerve injury — The most common neurological complication of humeral shaft fractures is a radial nerve injury, which presents as paresthesias of the dorsal hand or weakness of wrist and finger extension. This injury occurs in approximately 11 percent of midshaft fractures and is more common with midshaft or distal shaft fractures associated with displacement [22]. Of these radial nerve injuries, 75 to 90 percent are temporary neurapraxias that resolve without specific treatment in four to six months [23]. However, we suggest that patients with such injuries be referred to an orthopedic surgeon for management. (See 'Orthopedic consultation or referral' above.)

Nonunion — Nonunion of humeral shaft fractures may be present if there is no radiographic evidence of union at three to four months [6]. Symptoms of nonunion include continued pain and swelling. Nonunion occurs more commonly in transverse fractures and severely comminuted fractures. It is estimated to occur in 2 to 10 percent of all humeral shaft fractures treated non-operatively [6]. Proximal third fractures are known to have higher rates of nonunion, up to 25 percent [10,24]. This higher rate of nonunion is presumed to be due to the pull of deltoid and pectoralis major muscles, along with possible interposition of muscle at the fracture site [10]. Surgical referral is indicated for all humeral shaft nonunions.

RECOMMENDATIONS FOR RETURN TO SPORT OR WORK — Patients typically cannot return to sport until 8 to 12 weeks following the injury when there is complete healing [19]. Low-impact activity, such as stationary bicycling, can be used to maintain cardiovascular fitness once pain is well controlled. Returning to work is typically easier in a functional brace, which allows for increased mobility, rather than in a hanging cast. Care must be taken to allow for continuous traction in the hanging cast. Work that is amenable to wearing a functional brace or hanging cast can typically be done one to two weeks following the injury. Patients whose jobs require use of both arms or involve heavy lifting should not return to work until full radiographic healing is achieved, and normal range of motion and strength are regained.

ADDITIONAL INFORMATION — Several UpToDate topics provide additional information about fractures, including the physiology of fracture healing, how to describe radiographs of fractures to consultants, acute and definitive fracture care (including how to make a cast), and the complications associated with fractures. These topics can be accessed using the links below:

●(See "General principles of fracture management: Bone healing and fracture description".)

●(See "General principles of fracture management: Fracture patterns and description in children".)

●(See "General principles of definitive fracture management".)

●(See "General principles of acute fracture management".)

●(See "General principles of fracture management: Early and late complications".)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Fractures of the skull, face, and upper extremity in adults" and "Society guideline links: Acute pain management".)

SUMMARY AND RECOMMENDATIONS

●Humerus shaft fractures are uncommon injuries that typically occur as the result of a direct blow or bending force applied to the upper arm. (See 'Mechanism of injury' above.)

●Initial evaluation of the patient with an upper arm injury includes inspection of skin integrity, neurovascular function, deformity, shortening, and is complemented by radiographs. Shoulder radiographs should include at least one view (axillary or scapular-Y) that assures that the humeral head is not dislocated. (See 'Symptoms and examination findings' above and 'Diagnostic imaging' above.)

●Urgent orthopedic referral is necessary for patients with open fractures, those who present with neurologic or vascular compromise, associated articular injuries, ipsilateral forearm fractures, and fracture-dislocations. (See 'Orthopedic consultation or referral' above.)

●Most (70 to 80 percent) humerus shaft fractures can be treated without surgical intervention. Initial immobilization is usually accomplished with a coaptation (sugar-tong) splint applied to the upper arm. An ordinary sling is used for most cases of transverse fractures. For oblique and spiral fractures that require some traction, a collar and cuff sling is used instead. (See 'Initial treatment' above.)

●Physicians experienced in the use of hanging casts to reduce angulated and displaced humerus shaft fractures may choose to use this technique, and application of a hanging cast rather than a coaptation splint may be appropriate for reliable patients with uncomplicated oblique and spiral fractures who do not have excessive swelling at presentation.

●After the initial swelling has resolved (typically after one to two weeks), a commercially available functional splint may be used for definitive immobilization and is used until adequate callous formation is apparent radiographically and the fracture is stable to manual stress, typically 10 to 14 weeks. (See 'Follow-up care' above.)

●Rehabilitation begins within a week of injury and includes pendulum exercises for the shoulder. Once the brace or hanging cast is removed, the patient may begin exercises to strengthen arm and shoulder muscles and restore range of motion.

●Return to sports or occupations that involve full use of the arm is expected in 8 to 12 weeks, but should not occur until callus is present, the fracture site is stable to manual stress, and range of motion has been restored. Patients generally can return to work that is amenable to a functional brace or hanging cast within one to two weeks. (See 'Recommendations for return to sport or work' above.)