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Humeral shaft fractures

Description

Humeral Shaft (Diaphysis) can fracture following injury to the arm due to a direct fall or blow, automobile injury, gun shot wound, missile injury, and rarely, due to ball-throwing injuries. It may also result following low-energy injury or fall in patients with significant osteoporosis or skeletal metastases.

 

Structure and function

The portion of humerus stretching between upper border of pectoralis major muscle insertion (just below the surgical neck) to supracondylar ridge distally, constitutes the humeral shaft. On cross-section, the proximal ½ of shaft is cylindrical, whereas distally, it tapers to become triangular. The medullary canal, likewise, tapers and ends just superior to Olecranon fossa, which is in contrast to femoral and tibial metaphysic, which widens distally. This is important to prevent distraction of femoral shaft fractures during antegrade intra-medullary nailing.

The humeral diaphysis has abundant soft tissue envelop and receives rich blood supply from perforating branches of the brachial artery, which aids in fracture healing. Branches of brachial artery constitute the main blood supply to humeral diaphysis. The main nutrient artery enters the humerus medially, distal to midshaft and provides intra-medullary and periosteal circulation. Soft tissues surrounding the humeral shaft are divided into two compartments by medial and lateral muscular septa. The biceps brachii, coracobrachialis, and brachialis muscles (elbow flexors); median nerve, musculocutaneous nerve and brachial vessels occupy the anterior compartment, whereas, the triceps muscle (elbow extensors) and the radial nerve are contained in the posterior compartment. At the level of middle 1/3rd of humeral shaft, the radial nerve runs in the radial groove (spiral groove or radial sulcus) and remains in contact with the posterior surface for about 6.5cms. It exits the posterior compartment and enters the anterior compartment by piercing the lateral intermuscular septum. The ulnar nerve, proximally, lies in the anterior compartment and pierces the medial intermuscular septum to enter the posterior compartment near the distal 1/3rd of the humerus. 

Epidemiology

In US, it equally affects all age groups. A bimodal distribution with peaks in the third and seventh decades reported in European population.

It is a common injury, representing 3% to 5% of all fractures in Adults. 8% of Humeral Shaft fractures are Pathological.  

It also represents 3% of all fractures in Children and constitutes less than 10% of humeral fractures in children. In children, they are more common under age 3 and above age 12. 

Clinical presentation

Mechanism Of Injury:

Direct trauma to the arm resulting in transverse or comminuted fractures of the shaft is the most common mode of injury in these patients. 

Spiral or Oblique fractures result from indirect injuries - a fall on an outstretched arm, especially in elderly patients. Rarely, ball-throwers can get this fracture pattern following violent muscular contractions of the arm muscles.

Clinical Presentation:

Patients usually present after a fall, direct blow or motor vehicle accident with mid-arm pain and shortened extremity.

Mid-arm area is tender to palpation and crepitus may be present on examination of arm.

Both the shoulder and elbow joints should be thoroughly evaluated, clinically and radiographically, as should the distal neurovascular status.

The incidence of concomitant radial nerve injuries is approximately 18%. 

Classification:

Routinely, humeral shaft fractures are descriptively classified as:

Classification

 

Comments

A) Based on Wound type:

Open 
Closed Fractures

75% fractures are closed.
Open fractures are indications for Internal fixation.

B) Based on Location:

Proximal 1/3rd,
Middle 1/3rd 
Distal 1/3rd

Radial Nerve Injury more common with Middle and Distal 1/3rd fractures .

C) Based on Degree of Displacement:

Non-displaced
Displaced

Displaced fractures through distal shaft are difficult to reduce and may show delayed healing or develop atrophic non-union.
Deltoid and Pectoralis Major muscle are the two main deforming forces.

D) Based on Anatomic Location:

1) Fracture line above the pectoralis major insertion.
2) Fracture line below the pectoralis major insertion and above the deltoid insertion.
3) Fracture line below the deltoid insertion.

In type 3: due to the deltoid pull on proximal fragment, fracture ends frequently displace and override.

E) Based on Direction:

Transverse,
Oblique or Spiral,
Comminuted.

Long Spiral, comminuted, and oblique fractures tend to heal rapidly compared to transverse fractures, due to larger available surface area.

F) Articular extension:

Extra-articular.
Intra-articular.

 

F) Intrinsic Condition of Bone:

Normal (Healthy Bone)
Pathologic (Metabolic, Metastatic, Infectious).

 

G) OTA Classification

OTA Compendium

 

Red flags

Look for radial nerve injury in patients with middle 1/3rd to distal 1/3rd shaft fracture. Check for ECRL/ECRB, EDC, ECU, EIP, and EPL functions.

Suspect child abuse in a child presenting with humerus and other fractures, especially if younger than 18 months of age. If older than 18 months age, long bone fractures are more likely due to accidental trauma.

Differential diagnosis

Look for associated injuries in form of:

Floating Elbow (Concomitant Ipsilateral Radius-Ulna and Humeral fractures).
Shoulder dislocation.
Moreover, humeral shaft fractures may serve as a predictor of potential intra-abdominal pathology in multiply injured trauma patients. 

Objective evidence

Anteroposterior and lateral views of arm at 90° to each other, including the shoulder and elbow joints should be obtained first (a figure like this one). 
DO NOT move the injured arm through the fracture site.
Traction views may be indicated in case of severely displaced fractures.

Contralateral arm radiographs aid in pre-operative planning.

Ultrasound has shown 93% sensitivity and 83% specificity in diagnosing long humeral and femoral fractures in emergency room setting. 

Computed tomography (CT) and MRI scanning is rarely indicated.

Risk factors and prevention

Propensity to fall.
Child and Elderly abuse.
High Speed motor vehicle accidents.

Treatment options

Most cases of isolated diaphyseal humeral fractures are managed non-operatively and successfully unite with an acceptable alignment and restore the pre-injury functional level.

Nonoperative methods lead to good results with more than 90% union rates. Cast bracing appears to be the most effective.

In current practice, these injuries are treated with a hanging arm cast or a co-aptation splint for 5-15 days, which is changed to a functional brace in 5-15 days when reduction is adequate and initial fracture pain subsides.

A) Non-Operative Treatment:

Treatment Options

Specifics

Hanging Cast

With elbow flexed to 900, the arm is placed hanging in a Velcro cast with a sling placed on the radial aspect of the wrist. 
Gravitational pull aids in achieving reduction (dependency traction) and avoid shortening.
Patient should stay upright during day and sleep in a recliner to have overnight gravitational pull on distal fragment.
It limits wrist, elbow and shoulder movements and exercises for shoulder and digits should be encouraged. 
Weekly radio-graphic evaluations are must.
Indications:
Displaced mid-shaft humeral fractures with shortening, particularly spiral or oblique patterns.
Relative Contra-Indications:
Transverse or short oblique fractures; because of the potential for distraction and possible nonunion.

Coaptation Splint

An U-shaped splint with forearm suspended in cuff and collar can be used for initial stabilization.
It is also a type of dependency traction to achieve fracture reduction, but with greater stabilization and less distraction than a hanging arm cast.
It is inexpensive, easy to apply and allows movements at wrist and hand.
However, it may allow shortening and cause axillary irritation if applied high into the axilla.
Commonly indicated for initial management of non-displaced fractures or fractures with minimal shortening, especially transverse or short oblique fractures.

Sling and Swathe (Velpeau’s Dressing or Thoracobrachial immobilization)

Most useful for non-compliant patients, children and elderly.
Fracture motion is reduced in a sling and stockinette body swathe for comfort.
Passive shoulder pendulum exercises should be initiated as early as possible to avoid shoulder contractures and adhesive capsulitis.

Skeletal Traction

Only indicated in special circumstances as in recumbent patients and patients with large soft tissue defects.
The traction pin (Kirschner wire or Steinmann Pin) is inserted medial to lateral through the olecranon.
Potential for Ulnar nerve injury and Infection.
No clear advantage over External fixation.

Functional bracing

This is the current gold standard method for conservative treatment of humeral shaft fractures.  (a figure like fig 7 here)..
Popularized by Sarmiento, it utilizes hydrostatic soft tissue compression to maintain fracture alignment while allowing motion at shoulder and elbow joints.
It protects the fracture site against varus and valgus angulation stresses and controls flexion as well as translational forces.
Typically applied as anterior and posterior shell held together with Velcro straps when initial pain and swelling have subsided after using Hanging arm cast or Coaptation splint. For best outcomes, requires upright patient and daily brace tightening as the swelling decreases.
Patients are allowed to use the injured arm as tolerated with abduction restricted to 600-700 until evidence of radiographic union.
The functional brace is worn for a minimum of 8-12 weeks after fracture or until radiographic evidence of union.
Contraindications include massive soft tissue injury and an inability to obtain or maintain acceptable fracture reduction as in a segmental fracture or a non-compliant patient.

B) Operative (Open) Treatment:

Very few cases of Humeral Shaft Fractures need open reduction internal fixation (ORIF).

Absolute Indications for ORIF of Humeral Shaft Fractures:

Relative Indications for ORIF of Humeral Shaft Fractures:

Open Fracture
Floating Elbow
Vascular Injury
Intra-Articular fracture

Poly-trauma
Inadequate closed reduction
Nonunion or unacceptable malunion
Pathologic fracture
Segmental fracture
Bilateral humeral fractures
Neurologic loss following penetrating trauma
Radial nerve palsy after fracture manipulation (controversial)

Two basic ORIF techniques are used:

ORIF Technique      

Specifics              

(1) Compression plate and screw fixation:
Posterior, lateral and anterolateral surgical approaches are used.
Anterolateral approach is preferred for proximal and middle 1/3rd shaft fractures.
Lateral approach can be used in case of radial exploration.
Posterior approach is used for isolated fractures in the distal ½.
Minimally invasive plate osteosynthesis (MIPO) is gaining popularity due to better
cosmetic outcomes and preservation of ideal fracture healing environment.

If ORIF is indicated, plate osteosynthesis is the gold standard 
treatment option for displaced humeral shaft fractures.
 (a figure like figure 3 & 4 here). 
Technique:
A 4.5-mm dynamic compression plate with fixation
of 8 to 10 cortices proximal and distal to the fracture is used.
Lag screws should be utilized wherever possible.
Advantages:
Best functional results.
Allows direct fracture reduction and stable fixation without violation of the rotator cuff.

(2) Intramedullary nailing:
Especially useful in osteopenic bone, segmental and pathological fractures.

Two types of intramedullary nails are available:

Flexible nails:
This design has relatively poor stability and multiple nails are required to fill the canal
to achieve an interference fit.
Reserved for humeral shaft fractures with minimal comminution.

Advantages include ease and speed of insertion.
However, they do not provide rigid fixation, do not prevent fracture shortening,
and do not provide significant rotational control.

Interlocking Nails:
Provide rotational and axial stability by proximal and distal interlocking mechanisms.
Both types of nails can be inserted through antegrade or retrograde techniques.
While performing antegrade nailing - avoid screw protrusion through medial
cortex while inserting proximal locking screws to avoid axillary nerve injury.
Distal locking usually consists of a single screw in the anteroposterior plane.
Lateral to medial insertion of screws are associated with risk of injury to lateral antebrachial cutaneous nerve.

Disadvantages:
High incidence of shoulder pain following antegrade humeral nailing.
Avoid rotator cuff injury while nail insertion and the proximal aspect of 
nail is countersunk to prevent subacromial impingement.

C) External Fixation

External fixation is used in open humerus fractures as in burns, gunshot wounds or severe comminuted open injuries with defects of skin, bone, or soft tissue. Other indications may include osteitis and infected non-union and only when other means of management are not applicable or appropriate.

Complications include pin tract infection, neurovascular injury, and nonunion.

Outcomes

Union takes approximately 8 weeks but full recovery may take up-to a year.

Fracture healing rates for this injury are >95%, even with non-operative treatment

Complications

Comments

1) Radial nerve injury      

Occurs in up to 18% of cases.
Most common with middle third fractures.
Also associated with Holstein-Lewis (distal third spiral shaft) fracture,which may entrap or lacerate the nerve.
Most injuries are neurapraxias or axonotmesis type and more than 70% recover over 3 months.
Transverse fractures are commonly associated with neurapraxia.
In case of Neurapraxia: nerve axons will regenerate at a rate of 1 mm/day.
Disappearance of nerve function with fracture reduction may indicate nerve entrapment and hence, immediate 
exploration is required, to prevent further nerve damage; however no clear advantage is reported and
this remains controversial.
Electromyography (EMG) or nerve conduction velocity (NCV) studies are used to assess nerve function.
If there is no recovery a delayed surgical exploration should be done after 3 to 4 months.
Tendon transfer may be required in some cases to restore function.

2) Vascular injury

Laceration of brachial artery with sharp ends of fracture fragments or with open penetrating injuries,
however, this is uncommon.
If present, commonly seen with proximal and distal third fractures.
Arterial inflow should be established within 6 hours.
External fixation should be considered to stabilize the fracture and protect the vascular repair.

3) Nonunion

Occurs in up to 15% of cases
Most commonly associated with fractures at the proximal or distal third of the humerus,
transverse fractures, fracture distraction, soft tissue interposition, and inadequate immobilization.
Management options include open reduction and internal fixation with autogenous bone grafting,
exchanging the nails and plating of the non-union.

4) Malunion

Incidence of malunion, mainly anterior angulation and varus variety is high. 
Functionally non-limiting if within:
20 degrees of anterior angulation, 30 degrees of varus angulation and 3 cm of shortening without apparent deformity .
Arm musculature and shoulder, elbow, and trunk range of motion can compensate for angular, rotational, and shortening deformities.
Obese patients may develop significant angulation during healing with hanging cast, compared to non-obese.

Holistic medicine

Geriatric humeral shaft fractures can be prevented by fall prevention programs focusing on individual’s balance, strength, and conditioning to improve gait and safe ambulation. E.g. practicing tai chi has been shown to reduce the risk of falls and improve bone health.

Miscellany

Sir John Charnley wrote, “It is perhaps the easiest of the major long bones to treat by conservative methods".

Seen in Snowboarders, Skiers, Baseball Pithcers, and Softball players. Snowboarders more often fracture the left humerus at the diaphysis.

When it results in spiral/oblique fracture pattern and known as “ball-thrower’s fracture”. These fairly rare injuries tend to affect arm wrestlers and throwing athletes, especially pitchers, javelin throwers and discus throwers.

Key terms

Humeral Shaft Fractures; Functional bracing; mid-shaft; radial nerve injury. 

Skills

Develop a habit to assess distal neurovascular function in all long bone and extremity trauma.
In case of Humeral Shaft fractures, learn to aptly rule out radial nerve palsy by assessing function of the Extensors in fore-arm (ECRL/ECRB, EDC, ECU, EIP, and EPL). 

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