r

 

 

 

DEFINITION

Incidence: 3% to 5% of all fractures12

The AO/ASIF classification of humeral shaft fractures is based on increasing fracture comminution and is divided into three types according to the contact between the two main fragments:

Type A: simple (contact >90%)

Type B: wedge/butterfly fragment (some contact) Type C: complex/comminuted (no contact)

Intramedullary nailing (IMN) can be used to stabilize fractures 2 cm distal to the surgical neck to 3 cm proximal to the olecranon fossa.12

The precise role of IMN is not defined. Proponents offer the following benefits over formal open reduction with internal fixation (ORIF): It is minimally invasive, causing limited soft tissue damage and no periosteal

stripping (preservation of vascular innervation)14; it is biomechanically superior; it is cosmetically advantageous (smaller incision); it is capable of indirect diaphyseal fracture reduction and metaphyseal fracture approximation. It can be helpful in severe open fractures in which plate and screw constructs could be less ideal from an infection standpoint (FIG 1).

 

FIG 1 • A. Intraoperative image of a type 3C open humerus fracture after undergoing vascular repair, débridement, limited internal fixation to protect the vascular repair (which was immediately adjacent to the fracture site), and external fixation. The medial and ulnar nerves as well as the vascular repair are seen here. B. Initial postoperative radiograph with preoperative template planning for IMN. It was felt that with her soft tissue injury and segmental fracture, extensive stripping and placement of a long plate-and-screw

construct might be a higher risk for infection. If that were to occur, future treatment could be hazardous from a neurovascular standpoint in this case. So conversion to a nail was done after 2 days after discussing this with the vascular surgeon. C. Postoperative radiograph after removal of the external fixator and temporary plate-and-screw construct and placement of an antegrade intramedullary nail.

 

Complications such as shoulder pain (with antegrade nailing), delayed union or nonunion, fracture about the implant, iatrogenic fracture comminution, and difficulty in the reconstruction of failures raise

questions regarding the usefulness of IMN over ORIF.7

Biomechanically, intramedullary nails are closer to the normal mechanical axis; consequently, they can act as a load-sharing device if there is cortical contact.

Unlike plate-and-screw fixation, a load-bearing construct, intramedullary nails are subjected to lower bending forces, making fatigue failure and cortical osteopenia secondary to stress shielding less likely.

 

 

ANATOMY

 

Comparatively, there are several anatomic differences between the long bones of the upper extremity versus the long bones of the lower extremity (femur, tibia).

 

 

 

The medullary canal terminates at the metaphysis (vs. diaphysis).

 

 

Isthmus: junction is at the middle-distal third (vs. proximal-middle third).

 

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Trumpet shape: The proximal two-thirds of the humeral canal is cylindrical; distally, the medullary canal rapidly tapers to a prismatic end at the diaphysis (hard cortical bone) versus the wide flare of the metaphysis (soft cancellous bone).

 

Because of the funnel shape of the humeral shaft, a true interference fit is difficult to obtain; therefore, proximal and distal static locking has become the standard of care for IMN of humeral fractures.

 

Neurovascular considerations include average distances of key structures from notable bony landmarks.

 

 

 

 

Axillary nerve to proximal humerus, 6.1 ± 0.7 cm (range 4.5 to 6.9 cm) Axillary nerve to surgical neck, 1.7 ± 0.8 cm (range 0.7 to 4.0 cm) Axillary nerve to greater tuberosity, 45.6 mm

 

Axillary nerve to distal edge acromion, 5 to 6 cm

 

Crossing of radial nerve at lateral intermuscular septum to proximal humerus, 17.0 ± 2.3 cm (range 13 to 22 cm)

 

Crossing of radial nerve at lateral intermuscular septum to olecranon fossa, 12.0 ± 2.3 cm (range 7.4 to 16.6 cm)

 

Crossing of radial nerve at lateral intermuscular septum to distal humerus, 16.0 ± 0.4 cm (range 9.0 to 20.5 cm)1,5,9

PATHOGENESIS

 

Biomodal distribution17

 

 

Young, male 21 to 30 years old: high-energy trauma

 

 

Older, female 60 to 80 years old: simple fall/rotational injury Five percent open17

 

Sixty-three percent AO/ASIF type A fracture patterns17

 

Various loading modes and the characteristic fracture patterns they create

 

 

 

 

 

Tension: transverse Compression: oblique Torsion: spiral Bending: butterfly

 

 

High energy: comminuted Red flags

 

Minimal trauma indicates a pathologic process.

 

Disconnection between history and fracture type suggests domestic abuse.

 

NATURAL HISTORY

 

The humerus is well enveloped in muscle and soft tissue, hence its good prognosis for healing in most uncomplicated fractures.

 

PATIENT HISTORY AND PHYSICAL FINDINGS

 

Patients with humeral shaft fractures present with arm pain, deformity, and swelling.

 

Demographics, medical history, and information regarding the circumstance and mechanism of injury should be obtained.

 

Particularly significant in upper extremity trauma: Hand dominance, occupation, age, and pertinent comorbidities must be solicited from the patient. All of these factors play a major role in determining whether to pursue surgical versus nonsurgical treatment.

 

On physical examination, the arm is typically shortened, angulated, or grossly deformed, with motion and crepitus on manipulation.

 

Document the status of the skin (open vs. closed fracture) and perform a careful neurovascular evaluation of the limb.

 

If indicated, Doppler pulse and compartment pressures should be checked.

 

Always examine the shoulder and elbow joint for possible associated musculoskeletal pathology.

 

Examine the radial nerve for evidence of injury by testing resistance to wrist and finger extension, with care to distinguish intrinsic extension from extrinsic extension.6

IMAGING AND OTHER DIAGNOSTIC STUDIES

 

Initial studies must always include orthogonal views (antero-posterior [AP] and lateral radiographs) of the fracture site, shoulder, and elbow (FIG 2). To obtain these radiographs, move the patient rather than rotating the injured limb through the fracture site. Lateral imaging typically needs to be done with a transthoracic projection in order to prevent rotation through the fracture site with positioning.

 

Traction radiographs may be helpful with comminuted or severely displaced fractures, and comparison radiographs of the contralateral side may be helpful for determining preoperative length.

 

Computed tomography (CT) scans rarely are indicated. Rare situations in which they should be obtained include significant rotational abnormality, precluding accurate orthogonal radiographs, and suspicion of possible intra-articular extension or an additional fracture or fractures at a different level.

 

Doppler pulse and compartment pressures should be checked, if indicated, following a thorough physical examination.

 

Suspicion of vascular injuries warrants an angiogram.

 

 

 

 

FIG 2 • AP and lateral radiographs of a displaced humeral shaft fracture, shortened and in varus angulation.

 

 

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DIFFERENTIAL DIAGNOSIS

 

Osteoporosis

Pathologic fractures

High- or low-energy trauma Open or closed fractures Domestic abuse

 

 

NONOPERATIVE MANAGEMENT

 

Most non- or minimally displaced humeral shaft fractures can be successfully treated nonoperatively, with union rates of more than 90% often reported.12

 

Common closed techniques include hanging arm cast, coaptation splint, Velpeau dressing, abduction humeral/shoulder spica cast, functional brace, and traction.

 

 

Each of these modalities has been successfully employed, but most commonly, either a hanging arm cast or coaptation splint is used for 1 to 2 weeks followed by a functional brace, tightened as the swelling decreases.

 

Hanging arm casts are a very good option for displaced, midshaft humeral fractures with shortening, especially oblique or spiral fracture patterns, if the cast is able to extend 2 cm or more proximal to the fracture site.

 

For nonoperative treatment to be effective, the patient should remain upright, either standing or sitting, and avoid leaning on the elbow for support. This allows for gravitational force to assist in fracture reduction.

 

 

As soon as possible, the patient should begin range-ofmotion (ROM) exercises of the fingers, wrist, elbow, and shoulder to minimize dependent swelling and joint stiffness.

 

Acceptable alignment of humeral shaft fractures is considered to be 3 cm of shortening, 30 degrees of varus/valgus angulation, and 20 degrees of anterior/posterior angulation.10

 

Varus/valgus angulation is tolerated better proximally, and more angulation may be tolerated better in patients with obesity.

 

Patients with large pendulous breasts are at increased risk for varus angulation if treated nonsurgically.

 

No set values for acceptable malrotation exist, but compensatory shoulder motion allows for considerable tolerance of rotational deformity.10

 

Low-velocity gunshot wounds act as closed injuries after initial treatment. Following irrigation and débridement of skin at entry and exit sites, tetanus status confirmation, and prophylactic antibiotic initiation, nonoperative

treatment modalities are commonly employed.10

 

SURGICAL MANAGEMENT

 

Successful nonoperative management may be impossible for various reasons.

 

 

Fracture pattern (eg, displaced, comminuted, segmental [segmental fractures are at risk of nonunion of one or both fracture sites])

 

 

Prolonged recumbency Morbid obesity

 

Large, pendulous breasts (in women)

 

Patient's inability to maintain a semisitting or reclined position owing to polytraumatic injuries or patient noncompliance

 

Operative indications include the following:

 

 

 

Proximal humeral fractures with diaphyseal extension Massive bone loss

 

 

Displaced transverse diaphyseal fractures Segmental fractures

 

Floating elbow

 

 

Pathologic or impending pathologic fractures Open fractures

 

 

 

Associated vascular injury Intra-articular extension Polytrauma

 

Spinal cord or brachial plexus injuries

 

Poor soft tissue over the fracture site(s), such as thermal burns

 

The most commonly cited overall best indication for IMN from this extensive list is a pathologic or impending pathologic fracture.

 

The need for operative intervention secondary to radial nerve dysfunction after closed manipulation is controversial.

 

 

There are advocates for both early nerve exploration and observation.

 

This condition was once thought to be an automatic indication for surgery; however, this assumption has since been called into question.12

 

Isolated comminution is not an indication for operative treatment.12 However, if surgical fixation is chosen over nonoperative management, antegrade IMN has been proposed by some to be favored over plate fixation for

comminuted or segmental fractures.2

 

Relative contraindications include the following:

 

 

Open epiphyses

 

 

Narrow intramedullary canal (ie, <9 mm) Prefracture deformity of the humeral shaft

 

Open fractures with obvious radial nerve palsy and neurologic loss after penetrating stab injuries

 

 

The last two conditions require nerve exploration with subsequent plate-and-screw fixation.

 

 

Chronically displaced fractures should be treated with ORIF rather than IMN to prevent traction-induced brachial plexus palsy and radial nerve injury.

Preoperative Planning

 

When selecting implant size, consider canal diameter, fracture pattern, patient anatomy, and postoperative protocol.

 

 

Nail length and diameter should take into account the distal narrowing of the humerus.

 

Estimations of the nail diameter, length, and necessity of reaming can be made using preoperative roentgenograms of the uninjured humerus.

 

Alternatively, the length and diameter of the medullary canal can be ascertained intraoperatively using a radiopaque gauge and C-arm imaging of the intact humerus. Use of a radiolucent table top will substantially improve the quality of the image as well as the ability to obtain accurate C-arm images.

 

 

Position the gauge anterior to the unaffected humerus with its distal end 2.5 cm or more proximal to the superior edge of the olecranon fossa and 1 cm distal to the superior edge of the articular surface.

 

Move the C-arm to the proximal end of the humerus and read the correct length directly from the stamped measurements on the nail length gauge. The IMN should end approximately 1 to 2 cm proximal to the olecranon fossa.

 

Measure the length of the IMN to allow the proximal end to be buried. This will reduce the incidence of subacromial impingement if an antegrade technique is used or encroachment

 

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on the olecranon fossa and blocked elbow extension if a retrograde approach is chosen.

 

 

In comminuted fractures, carefully choose the length to avoid distracting the humerus, which predisposes the patient to delayed union or nonunion.

 

Measure the diameter of the medullary canal at the narrowest part that will contain the nail.

 

In retrograde nailing, it is important to determine the relation between alignment of the humeral canal and the entry point of the nail by measuring the anterior deviation/distal humeral offset of the distal canal on the preoperative lateral radiograph.

 

 

Based on these calculations, if the deviation is small, make a distal, long entry portal that includes the superior border of the olecranon fossa.

 

If the anterior deviation is large, however, make the entry portal more proximal and shorter in length.

 

Positioning

 

The patient's position for surgery is determined based on the method chosen for fixation.

 

Antegrade Intramedullary Nailing

 

Place the patient in either a beach chair or supine position on a radiolucent table with the head of the bed elevated 30 to 40 degrees (FIG 3).

 

Put a small roll between the medial borders of the scapula and rotate the head to the contralateral side to increase exposure of the shoulder.

 

Certain fracture patterns may call for skeletal traction.

 

 

If it is used, place an olecranon pin and apply intermittent traction to avoid brachial plexus palsy.

 

Clinically assess the rotational alignment by placing the shoulder in an anatomic position and rotating the

distal fragment of the fracture humerus so that the arm and hand point toward the ceiling and the elbow is flexed 90 degrees.

 

 

 

 

FIG 3 • A. Beach-chair position for antegrade IMN. B. Beach-chair position for antegrade IMN using a McConnell positioner (McConnell Orthopedic Manufacturing Co., Greenville, TX). C. Supine position. Note the bump under the scapula and the C-arm image intensifier ready to come in from the contralateral side. D. Carm imaging from the contralateral side. The patient is in the supine position.

 

 

Prepare the affected extremity and drape the arm free in the typical manner. The operative area should encompass the shoulder proximal to the nipple line, the midline of the chest to the nape of the neck, and the entire affected extremity to the fingertips.

 

Bring the patient to the edge of the radiolucent table to improve the ability to obtain orthogonal C-arm images of the affected extremity.

 

 

It may be necessary to have the patient lying partially off the table on a radiolucent support.

 

Cover the C-arm imager with a sterile isolation drape. Most commonly, the C-arm is brought in directly lateral on the injured side, although some surgeons favor coming in from the contralateral side.

 

 

Regardless of which direction the C-arm is brought into the field, it is imperative to obtain orthogonal views of the entire humerus before the first incision is made.

 

Retrograde Intramedullary Nailing

 

Put the patient in the lateral decubitus or prone position with dorsum placed near the edge of the operating table.

 

If the patient is in the prone position, the affected arm may be supported on a radiolucent arm board or placed over a bolster or paint roller upper extremity support. The latter two options facilitate access to the olecranon fossa and prevent a traction injury to the brachial plexus. The arm should be positioned in 80 degrees of abduction with the elbow flexed at least 90 degrees.

 

If the lateral decubitus position is used, suspend the fractured extremity, taking care not to distract the fracture site or cause neurovascular compromise. Suspension can be aided by an olecranon pin.

 

 

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Prepare the affected extremity and drape the arm free in the typical manner. Include the distal clavicle, the acromion, the medial scapula, and the entire arm and hand in the operative field.

 

Cover the C-arm imager with a sterile isolation drape. Bring the C-arm from the ipsilateral side and make sure that adequate orthogonal C-arm images are possible before making the surgical approach.

 

Approach

 

 

Standard locked intramedullary humeral nails can be inserted either antegrade or retrograde.

 

TECHNIQUES

• Antegrade Intramedullary Nailing

Approach

The antegrade approach, which has been the traditional method of IMN, typically involves a starting point at the proximal humerus—either through the rotator cuff, where the tissue is less vascular, or just lateral to the articular surface, where the blood supply is higher (TECH FIG 1).

Palpate and outline the surface anatomy of the acromion, clavicle, and humeral head.

Feel the anterior and posterior borders of the humeral head to locate and mark the midline.

Make a small longitudinal incision at the anterolateral corner of the acromion centered over the top of the greater tuberosity. Extend it 3 cm distally.

The C-arm can be used to locate the exact entry point before performing the anterior acromial approach.

Place a K-wire percutaneously into the ideal entry point under C-arm imaging guidance. Confirm the location on orthogonal images.

Leave the K-wire intact while making an anterior acromial approach. Split the deltoid fibers in line with the longitudinal cutaneous incision.

Do not extend the incision distally more than 4 or 5 cm in the deltoid muscle to avoid damage to the axillary nerve.

 

 

 

TECH FIG 1 • Postoperative AP and lateral radiographs of antegrade IMN for a midshaft humerus fracture.

 

 

Excise any visible subdeltoid bursae to improve your visualization of the rotator cuff.

 

Longitudinally incise the supraspinatus in line with the deltoid/cutaneous incision for 1 to 2 cm, just posterior to the bicipital tuberosity.

 

Placing suture tags at the margins of the supraspinatus will help retract its edges during the remainder of the procedure and assist in achieving an optimal rotator cuff repair during wound closure.

 

There is insufficient evidence to indicate that a larger incision, in cases in which the rotator cuff is identified and purposely incised, is superior to a smaller incision made with the aid of C-arm imaging.13

Entry Hole

 

Make the entry hole medial to the tip of the greater tuberosity, just lateral to the articular margin and approximately 0.5 cm posterior to the bicipital groove to minimize damage to the supraspinatus (TECH FIG 2).

 

Linear access to the humeral medullary canal is possible only though an entry portal made in this sulcus between the greater tuberosity and the articular surface.

 

 

 

TECH FIG 2 • AP and lateral intraoperative fluoroscopic images demonstrating the proper placement of a guidewire for the portal for antegrade nailing.

 

 

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Make sure the entry portal is centered on AP and lateral C-arm images to ensure the nail will be in the midplane of the humerus.

 

If the entry hole is too medial, it will violate the supraspinatus; if the entry portal is too lateral, it will cause some degree of varus angulation (in proximal fractures) or substantially increase the risk of an iatrogenic fracture during nail insertion.

 

Proximal third fractures may require a more medially located entry hole to avoid varus angulation at the fracture site.

Entrance into Medullary Canal

 

After establishing the entry hole, insert a K-wire through the portal into the medullary canal to the level of the lesser tuberosity.

 

Next, to open the medullary canal, either use a cannulated awl or pass a cannulated drill bit over the K-wire, through a protection sleeve, and drill to the depth of the lesser tuberosity.

 

Adduct the proximal component of the fractured humerus and extend the shoulder to improve clearance of the acromion and facilitate awl or starter reamer access to the correct portal location.

 

Once the medullary canal has been opened, remove the guidewire and insert a long, ball-tipped guidewire. Bending the tip of the guidewire may aid in its passage across the fracture site.

Provisional Reduction/Guidewire Passage

 

Manipulate the extremity to reduce the fracture. In many cases, reduction is obtained through a combination of adduction, neutral forearm rotation, and longitudinal traction.

 

While advancing the guidewire down the canal, rotate the arm about its longitudinal axis and take several C-arm images to confirm that the guidewire remains contained in the canal.

 

This is especially important if the humerus is substantially comminuted.

 

Slowly and deliberately pass the guidewire across the fracture site.

 

Difficult passage may be a tip-off that soft tissue may be interposed (possibly the radial nerve).

 

An open fracture is advantageous in this situation because it provides the opportunity to directly visualize and clear the fracture site of any problematic soft tissue.

 

After crossing the fracture site, advance the ball-tipped guidewire into the center of the distal fragment until the tip is 1 to 2 cm proximal to the olecranon fossa.

 

Avoid shortening or distracting the fracture site while firmly securing the guidewire into the distal fragment.

Determining Nail Length

 

Determine the correct nail length by one of two methods:

 

Guide rod method: With the distal end of the rod 1 to 2 cm proximal to the olecranon fossa, overlap a second guide rod extending proximally from the humeral entry portal. Subtract the length in mm of the overlapped guide rod from the total length of an identical guidewire to determine the correct nail length.

 

Nail length gauge: Position the radiopaque gauge anterior to the fractured humerus. Move the C-arm to the proximal end of the humerus and read the length from the stamped measurements on the gauge.

 

The ideal length of an IMN should be measured 1 cm distal to the articular surface of the humeral head to a point 1 to 2 cm proximal to the olecranon fossa.

 

If the calculated length falls between two standardized nail lengths of the chosen implant, always choose the smaller size.

 

Excessively long nails are a risk factor for subacromial impingement and fracture site distraction.

 

Avoid the temptation to countersink an excessively long nail below the subchondral surface of the proximal humerus as this can cause an iatrogenic split of the distal humerus or can create a supracondylar fracture when the tip of the nail is wedged too close to the olecranon fossa. In these cases, it is best to remove the nail and replace it with one which is one size shorter.

Reaming the Humeral Shaft

 

Reaming the humeral shaft usually is avoided, especially in comminuted fractures, to avoid reaming injury

to the radial nerve or the rotator cuff.

 

If it is warranted, slowly ream the entire humerus over the balltipped reamer guidewire in 0.5-mm increments.

 

Exercise greater caution when reaming the humerus than when reaming the long bones of the lower extremity because the cortical thickness of the humerus is substantially less than that of the tibia or femur.

 

Ream 0.5 mm to 1 mm larger than the selected nail diameter. Ream minimally until the sound of cortical chatter becomes audible.

 

Choose a nail 1 mm smaller in diameter than the last reamer used.

 

Some implant systems require that the ball-tipped guidewire be replaced with a rod that does not have a tip.

 

Use the medullary exchange tube when replacing the guidewire to maintain fracture reduction.

Inserting the Nail

 

Once the correct nail length and the diameter of the selected implant have been verified, attach the nail adapter, place the nail-holding screw through the nail adapter, and then attach the radiolucent targeting device onto the nail adapter.

 

Verify that this assembly is locked in the appropriate position and that its alignment is correct by inserting a drill bit through the assembled tissue protection/drill sleeve placed in the required holes of the targeting device.

 

Insert the nail with sustained manual pressure.

 

Aggressive placement can result in iatrogenic fractures or displacement of the fracture fragments.

 

Use the C-arm image intensifier to identify the source of the problem if the IMN does not easily advance.

 

Insert the nail at least to the first circumferential groove on the nail adapter but no deeper than the second groove.

 

Ideally, the IMN should be countersunk about 5 mm below the articular surface to avoid subacromial impingement.

 

Sinking the nail more than 1 cm below the articular surface may place the proximal interlocking screws at the level of the axillary nerve.

 

If the proximal end of the nail is properly countersunk, the incidence of shoulder pain is reportedly less than 2%.4

 

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Attach a strike plate to the targeting device and use a mallet to impact the proximal jig assembly to eliminate any fracture gap or advance the IMN.

 

Do not hit the targeting device or the nail-holding screw directly.

 

 

The distal end of the IMN should come to lie about 2 cm proximal to the olecranon fossa. Remove the guidewire.

Compression

 

Before proximal interlock insertion, make sure that optimal fracture site compression is present.

 

Proximal compression locking can be used for transverse or short oblique fracture patterns. Severe

osteopenia is a contraindication to its use.

 

Explore the radial nerve before compression locking if any possibility of radial nerve entrapment exists.

 

The nail must be overinserted by the same distance of anticipated interfragmentary travel because otherwise, during compression, the nail will back out and cause subacromial impingement.

 

Additionally, if the fracture is suitable for compression, the chosen implant should be 6 to 10 mm shorter than the calculated measurement to avoid proximal migration of the nail beyond the insertion site.

 

Proximal locking screw placement

 

Oblique proximal locking screws are preferred because their insertion point is cephalad to axillary nerve.

 

It is important to make sure that these screws are inserted above the level of the humeral neck to avoid axillary nerve injury.

 

Lateral screws placed too proximal can produce subacromial impingement with terminal arm elevation.

 

Some implant systems may offer a spiral blade fixation as an option for proximal interlocking. In theory, it creates a fixed-angle construct and has a higher resistance (vs. screws) against loosening (ie, “windshield wiper” effect; TECH FIG 3). Other devices offer multiple screws in multiple planes in the proximal humerus for compromised bone or for proximal humeral fracture fixation.

Determining Rotation

 

Confirm rotational alignment before placing distal interlock screws. Rotational alignment can be ascertained clinically and radiographically.

 

Magnified C-arm AP images of the fracture site can be used to judge the medial and lateral cortical width of the most proximal and most distal aspects of the fracture site.

 

Proper rotation is achieved when these widths are identical.

Distal Locking Screws

 

Insert distal interlocking screws using a freehand technique.

 

To place AP-directed screws, advance the C-arm over the distal humerus until the distal interlocking hole is seen to be in maximal relief—that is, “perfect circle.”

 

Under C-arm imaging, place a scalpel over the skin to precisely determine the location of the incision. Make every attempt to keep this incision just lateral to the biceps tendon. This will decrease the risk to brachial artery, median nerve, and musculocutaneous nerve.

 

 

 

TECH FIG 3 • Postoperative AP and lateral radiographs of antegrade IMN for a midshaft humerus fracture. A spiral blade has been used for proximal interlock fixation.

 

 

Carefully make the incision though the skin and spread through the brachialis muscle down to the bone. This should not be a percutaneous incision, but rather, a generous enough incision so that you have adequate visualization with appropriate retractors.

 

Insert a short drill bit through a soft tissue protector.

 

Center the drill bit in the locking hole and then position it perpendicular to the nail.

 

Attach the drill and penetrate the near cortex. Then detach the drill bit from the drill and use a mallet to gently advance the drill bit through the nail up to the far cortex.

 

An orthogonal C-arm image may be used to verify that the position of the drill bit is satisfactory.

 

Reattach the drill and penetrate the far cortex.

 

A depth gauge can now be inserted to ascertain the length of the interlock screw.

 

Use C-arm image intensification to confirm screw position through the nail as well as screw length.

 

Avoid articular penetration into the glenohumeral joint.

 

Lateral to medial directed distal locking screws

 

Either in combination with or as an alternative to anterior to posterior screws, insert lateral to medial screws if necessary. This may be needed in cases of poor bone density and need for a second screw in an orthogonal position to the AP screw. Skin problems or anatomic issues anteriorly could also potentially obviate the placement of an AP screw, therefore requiring a lateral to medial screw.

 

Make a generous 5-cm incision to decrease the risk to the radial nerve. It is due to this risk that this particular screw trajectory is less ideal compared with the anterior to posteriorly directed screws.

 

Use the same technique employed when placing AP-directed screws: blunt dissection, a protecting drill/screw insertion sleeve, and perfect circle freehand technique.

 

Finally, confirm the IMN position, fracture reduction, and interlocking screw(s) placement with multiple orthogonal C-arm images.

 

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After orthogonal C-arm images demonstrate satisfactory reduction and hardware implantation, remove the proximal targeting device and place an end cap (this last step is optional, depending on surgeon preference).

 

Carefully select the length of the end cap to avoid impingement.

Wound Closure

 

Copiously irrigate all wounds before they are closed.

 

During closure of the proximal insertion site, formally repair the surgically incised rotator cuff and deltoid raphe; side-to-side nonabsorbable sutures commonly are recommended.

• Retrograde Intramedullary Nailing

Approach

 

Make a limited posterior approach centered over the distal humerus, starting at the olecranon tip to a point 6 cm proximal.

 

Longitudinally split the triceps in line with its fibers to the cortical surface of the humerus and identify the olecranon fossa.

 

Make every attempt to avoid entering the elbow joint to decrease the possibility of periarticular scarring.

Starting or Entry Portals

 

As previously discussed in the Approach section, the coronal deviation of the distal humerus is variable, and, therefore, two potential starting portals exist:

 

Traditional metaphyseal entry portal: created by reaming in the midline of the distal metaphyseal triangle 2.5 cm proximal to the olecranon fossa

 

Olecranon fossa entry portal: established by reaming the proximal slope of the olecranon at the superior border of the olecranon fossa

 

The more distal location of the nontraditional olecranon fossa entry portal increases the effective working length of the distal segment and provides a straighter alignment with the medullary canal.

 

However, biomechanical investigation has found that the olecranon fossa entry portal provides greater reduction in torque resistance and load to failure, which may increase the probability of an iatrogenic or postoperative fracture.16

 

When making either entry portal, pay careful attention to the relation between the olecranon fossa and the longitudinal axis of the humerus in order to place the entry portal in line with the humeral shaft. The axis of the humerus usually is colinear with the lateral aspect of the olecranon fossa.

 

Make the initial entry portal in one of two ways:

 

Open the near cortex with a 4.5-mm drill bit. Continue drilling while progressively lowering the drill toward the arm until the drill bit is in line with the medullary canal on the lateral C-arm images.

 

Drill three small pilot holes in a triangular configuration perpendicular to the cortical surface. Connect these holes with a large drill bit and small rongeur or enlarge the triangular site with a small curved awl to create a long, oval hole 1 cm wide × 2 cm long that leads directly into the medullary canal.

 

Undercut the internal aspect of the posterior cortex in addition to the medial and lateral walls of the entry portal to create a distal bevel along the path of nail insertion.

 

This will facilitate easy passage of the guidewire, optional reamer, and final implant.

Provisional Reduction and Guidewire Passage

 

Now follow the same steps outlined in the antegrade IMN technique section to pass the guidewire, reduce the fracture, ream (optional), measure the desired nail length and diameter, and insert the chosen implant.

 

Reduction of the fracture usually involves gentle longitudinal traction on the distal humerus and correction of the varus-valgus displacement.

Reaming (Optional)

 

If it is necessary to ream, carefully select the reamer size to avoid damage to the posterior cortex. In addition, slowly advance the reamer under C-arm image guidance to avoid excessive reaming of the anterior humeral cortex.

 

Both of these steps decrease the risk of possible iatrogenically induced fractures.

Distal Locking Screws

 

Next, distally lock the nail to prevent backing out, that is, blocked elbow extension.

 

Place the distal locking screws from posterior to anterior using a guide.

 

Make an indentation with the guide, incise the cutaneous layer, and then use a blunt hemostat to spread down to the bone.

 

Follow the remaining steps unique to the chosen implant.

 

After distal interlocking, gently tap the insertion bolt with a mallet to compress the fracture site. Assess the reduction with C-arm images.

Proximal Locking Screws

 

Next, place a proximal interlocking screw, either anterior to posterior, posterior to anterior, or lateral to medial.

 

Incise the skin and use a blunt hemostat to spread down to bone to protect the biceps tendon (anterior to posterior directed screws) or axillary nerve (posterior to anterior and lateral to medial directed screws).

 

Use C-arm image intensification to confirm screw position through the nail as well as screw length.

Wound Closure

 

Copiously irrigate each wound before closing it. Close triceps split with interrupted nonabsorbable sutures.

 

 

 

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PEARLS AND PITFALLS

 

IMN

contraindications

• Antegrade nailing in patients with preexisting shoulder pathology (eg, impingement, rotator cuff)

• Permanent upper extremity weight bearers (eg, para- or tetraplegics)

   

  Antegrade IMN entry site

  • If the entry portal is too far laterally, the lateral wall of the proximal humerus can be reamed out or fractured during nail insertion.

  • Pushing the reamer shaft medially may prevent this complication.

     

    Nail insertion ▪ If any resistance is met while attempting to pass the nail, either antegrade or retrograde, make a small incision to ensure that the radial nerve is not entrapped in the fracture site.

     

    Interlock screws ▪ In most cases, soft tissues should be bluntly spread down to the bone with a hemostat before holes are drilled for any interlocking screw, to minimize neurovascular injury.

    • Antegrade IMN distal interlock screws: Make generous incisions rather than percutaneous incisions when placing distal locking screws. This way, proper visualization can permit safe instrumentation with regard to neurovascular structures.

      Antegrade IMN: Rotate the C-arm 180 degrees, so the top can be used as a table to support the arm for placing the distal locking screws.

       

      Nail length ▪ Always err on the side of a shorter nail: Do not distract the fracture site or cause iatrogenic fractures by trying to impact a nail that is excessively long.

    • The retrograde IMN must be long enough to engage the cancellous part of the humeral head; the wide medullary flare of the proximal one-third of the shaft does not provide sufficient stability to the inserted nail.

       

      Open fractures: reaming

  • After a thorough irrigation and débridement is performed and the guidewire is successfully passed across the fracture site, close the deep muscle layer around the fracture site to keep the osteogenic reaming debris from washing away.

 

POSTOPERATIVE CARE

 

Tailor the postoperative rehabilitation regimen to the method of nailing (antegrade vs. retrograde), stability of the fracture, overall patient health, and preinjury level of activity/workplace demands.

 

Antegrade IMN

 

 

Place the affected arm in a sling or shoulder immobilizer at the end of surgery.

 

Postoperative day 2: Remove the dressing and begin gentle shoulder pendulum and elbow ROM exercises.

 

Postoperative days 10 to 14: Remove the sutures. Institute a structured, supervised physical therapy program. Close patient monitoring and formal therapy are key components to achieving maximum postoperative function.

 

Subsequently, schedule follow-up visits at 4- to 6-week intervals, depending on the patient's clinical and radiographic progression. Healing often takes 12 weeks or longer.

 

As union progresses, the therapist may begin supervised exercises to recover upper extremity strength. Caution the therapist against instituting programs or exercises that create large rotational stresses to the arm until radiographic healing becomes evident.

 

Retrograde IMN

 

 

Initial postoperative management is identical to treatment following antegrade nailing, unless weight bearing is necessary for wheelchair transfers, walkers, or crutch ambulation. Use a posterior splint and platform attachment if crutches are necessary.

 

It is important to institute early elbow active ROM or gentle passive range of motion (PROM) by the patient to prevent elbow stiffness.

 

Avoid the following:

 

 

Aggressive PROM or stretching to decrease the risk of myositis ossificans formation

 

Resisted elbow extension for the first 6 weeks after surgery to protect the repair of the triceps split

 

 

OUTCOMES

Randomized clinical trials comparing IMN to compression plating show a higher reoperation rate and greater shoulder morbidity with the use of nails.11

Locked antegrade IMN has resulted in loss of shoulder motion in 6% to 37% of cases.13

Recent antegrade nails designed to eliminate insertion site shoulder morbidity through an extra-articular start point have been introduced, and prospective randomized trials are pending.

Retrograde IMN union rates range from 91% to 98%, and the mean healing time is 13.7 weeks.15 Retrospective reviews of retrograde IMN have found shoulder function to be excellent in 92.3% of patients and elbow function excellent in 87.2% of patients after fracture consolidation.15

Functional end results were excellent in 84.6% of patients, moderate in 10.3% of patients, and bad in 5.1% of patients.

Biomechanical studies have shown that, for midshaft fractures, both antegrade and retrograde nailing showed similar initial stability and bending and torsional stiffness—20% to 30% of normal humeral

shafts.8

In proximal fractures (ie, 10 cm distal to the greater tuberosity tip), antegrade nails demonstrated significantly more initial stability and higher bending and torsional stiffness, as was true for distal fractures with retrograde nailing.

COMPLICATIONS

Nonunion3

Nonunion of the humerus after IMN is preferentially treated with plate fixation, with or without bone grafting, depending on the biologic type of nonunion. Exchange nailing, a procedure done frequently in the tibia and femur, is not generally as successful in the humerus.

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Antegrade IMN: 11.6%

Retrograde IMN: 4.5%

Infection: 1% to 2% Insertion site morbidity

Antegrade IMN: shoulder pain, impingement, stiffness, and weakness Retrograde IMN: elbow pain, stiffness, and triceps weakness

Iatrogenic fractures3 Antegrade IMN: 5.1%

Retrograde IMN: 7.1%

Iatrogenic comminution and distraction at the fracture site Neurovascular risk

Risk to the radial nerve in the spiral groove from canal preparation and nail insertion Risk to the axillary nerve from proximal interlocking

Risk to the radial, musculocutaneous, and median nerves or brachial artery from distal interlocking Heat-induced segmental avascularity after reaming

 

 

REFERENCES

1. Bono CM, Grossman MG, Hochwald N, et al. Radial and axillary nerves. Anatomic considerations for humeral fixation. Clin Orthop Relat Res 2000;373:259-264.

    

    

2. Chen AL, Joseph TN, Wolinsky PR, et al. Fixation stability of comminuted humeral shaft fractures: locked intramedullary nailing versus plate fixation. J Trauma 2002;53:733-737.

    

    

3. Court-Brown C. Paper presented at the Orthopaedic Trauma Association Specialty Day Meeting, February 26, 2005, Washington, DC.

    

    

4. Crates J, Whittle AP. Antegrade interlocking nailing of acute humeral shaft fractures. Clin Orthop Relat Res 1998;350:40-50.

    

    

5. Farragos AF, Schemitsch EH, McKee MD. Complications of intramedullary nailing for fractures of the humeral shaft: a review. J Orthop Trauma 1999;13:258-267.

    

    

6. Foster RJ, Swiontowski MF, Back AW, et al. Radial nerve palsy caused by open humeral shaft fractures. J Hand Surg Am 1993;18: 121-124.

    

    

7. Green AG, Reid JS, Carlson DA. Fractures of the humerus. In Baumgaertner MR, Tornetta P, eds. Orthopaedic Knowledge Update: Trauma. Rosemont, IL: American Academy of Orthopaedic Surgeons, 2005:163-180.

    

    

8. Lin J, Inoue N, Valdevit A, et al. Biomechanical comparison of antegrade and retrograde nailing of humeral shaft fracture. Clin Orthop Relat Res 1998;351:203-213.

    

    

9. Lin J, Hou SM, Inoue N, et al. Anatomic considerations of locked humeral nailing. Clin Orthop Relat Res 1999;368:247-254.

    

    

10. Lyons RP, Lazarus MD. Shoulder and arm trauma: bone. In Vacaro AR, ed. Orthopaedic Knowledge Update 8. Rosemont, IL: American Academy of Orthopaedic Surgeons, 2005:275-277.

     

     

11. McCormack RG, Brien D, Buckley RE, et al. Fixation of fractures of the shaft of the humerus by dynamic compression plate or intramedullary nail: a prospective randomized trial. J Bone Joint Surg Br 2000;82B:336-339.

     

     

12. McKee MD. Fractures of the shaft of the humerus. In Bucholz RW, Heckman JD, Court-Brown C, eds. Rockwood and Green's Fractures in Adults, ed 6. Philadelphia: Lippincott Williams & Wilkins, 2006: 1117-1157.

     

     

13. Riemer BL, Foglesong ME, Burke CJ. Complications of Seidel intramedullary nailing of narrow diameter humeral diaphyseal fractures. Orthopedics 1994;17:19-29.

     

     

14. Roberts CS, Walz BM, Yerasimides JG. Humeral shaft fractures: intramedullary nailing. In Wiss D, ed. Master Techniques in Orthopaedic Surgery: Fractures, ed 2. Philadelphia: Lippincott Williams & Wilkins, 2006:81-95.

     

     

15. Rommens PM, Verbruggen J, Broos PL. Retrograde locked nailing of humeral shaft fractures. A review of 39 patients. J Bone Joint Surg Br 1995;77B:84-89.

     

     

16. Strothman D, Templeman DC, Varecka T, et al. Retrograde nailing of humeral shaft fractures: a biomechanical study of its effects on strength of the distal humerus. J Orthop Trauma 2000;14:101.

     

     

17. Tytherleigh-Strong G, Walls N, McQueen MM. The epidemiology of humeral shaft fractures. J Bone Joint Surg Br 1998;80B:249-253.