Radial Nerve Injury- Locations

radial nerveThe posterior cord of the brachial plexus gives the axillary and radial nerves. Radial nerve compression or injury may occur at any point along the course of the nerve. All motor and sensory function below the axilla will be affected with injury at this level. With injury to the radial nerve at the axilla, there will be loss of function to the triceps and weak elbow extension. The patient will experience wrist drop due tSaturday night palsyo loss of function associated with the extensor carpi radialis longus and extensor carpi radialis brevis muscles. There will also be a loss of finger extension. Put the wrist in extension and ask the patient to extend the fingers. Sensory loss will also be seen in the distribution of the superficial branch of the radial nerve.

Saturday Night Palsy is a common cause of compression or injury to the radial nerve at the axilla. This condition is named due to the position a person may fall asleep in while drinking, with the back of their arm compressed by a chair back, or bar edge, etc. Another common condition is referred to as Honeymoon Palsy, which occurs from another individual sleeping on one’s arm overnight, compressing the nerve. Crutch Palsy occurs from the compression on the nerve from walking with crutches.

radial nerrrrrrveeeeeeAdditionally, there are several compressions or fractures that may cause injury to the radial nerve within the spiral groove. For example, a fracture of the distal third of the humerus may entrap the radial nerve, causing all motor and sensory function below the level of injury to be affected. The radial nerve is vulnerable, usually due to a fracture of the humerus at the spiral groove. Injury may also occur below the spinal groove when there is a fracture in the distal third of the humeral shaft. If a Holstein-Lewis Fracture occurs, injury to the nerve at this level will cause the condition known as wrist drop, as well as weakness of finger extension. Sensory loss will also be seen in the distribution of the superficial branch of the radial nerve.

Entrapment of the posterior interosseous nerve at the “Arcade of Frohse” is a low radial nerve palsy; occurring below the elbow. Motor function below this area will be affected by the injury. The posterior interosseous nerve is purely motor and the patient will have no sensory loss. The Arcade of Frohse is a site of radial nerve entrapment which may cause paralysis of the posterior interosseous nerve. frohse

With injury to the posterior interosseous nerve, the patient will experience difficulty with extension of the fingers only. It is important for the physician to ask the patient to extend the wrist first when examining the finger extension. A Monteggia Fracture, or a fracture of the proximal third of the ulna/radius with dislocation of the radial head may cause compression of the radial nerve secondary to the fracture. A neurovascular examination is important for these fractures. A nerve injury, especially involving the posterior interosseous nerve, is not uncommon (observe). The patient will have a loss of finger extension. Wartenberg’s Syndrome is a compression of the superficial branch of the radial nerve. Pain associated with this condition is located 8cm proximal to the radial styloid; wearing a wristwatch may irritate this area. Pain and paresthesia will be experienced on the dorsum of the hand and the patient will have a positive Tinel’s sign.

wartenburgs point

 

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Supracondylar Fractures of the Humerus in Children

Supracondylar fractures constitute approximately 50% of all elbow fractures. The supracondylar region is thin and weak and thus can fracture easily. These fractures are classified into two different types: extension and flexion.

fracture typesExtension type fractures are the most common type, occurring approximately 95% of the time. Extension fractures typically occur due to falling onto an outstretched hand. With extension fractures, the distal fragment of the humerus displaces posteriorly. Anterior interosseous neurapraxia is the most common nerve palsyOKsign occurring with supracondylar fractures. Injury to the anterior interosseous nerve will lead to weakness of the flexor digitorum profundus muscle to the index finger and the flexor pollicis longus muscle. The patient will not be able to make an “OK” sign or bend the tip of his index finger. Radial nerve neurapraxia is the second most common palsy and is evident by weakness in wrist and finger extension.

The second type of fractures, flexion type fractures are rare and occurs due to falling flexionfxdirectly on a flexed elbow. In flexion type fractures, the distal fragment is displaced anteriorly. This type of fracture may be accompanied with ulnar nerve neurapraxia. Injury to the ulnar nerve will lead to a loss of sensation along the little finger. Later on, the patient may also have weakness of the intrinsic hand muscles and clawing.

 

Gartland Classification System

gartland classificationThe Gartland Classification System provides physicians with a way to categorize supracondylar humerus fractures. There are four classifications and are as follows: Type I fractures are nondisplaced fractures; Type II are angulated with an intact posterior cortex; Type III are completely displaced; and Type IV has complete periosteal disruption with instability in both flexion and extension.

Radiology

Plain AP and lateral x-rays should be obtained. A posterior fat pad sign seen on a anterior humeral linelateral view x-ray should increase your suspicion of an occult fracture around the elbow. On a lateral view x-ray, the anterior humeral line is drawn along the anterior border of the distal humerus. Normally, the anterior humeral line should run through the middle third of the capitellum. In extension type fractures, the capitellum will be displaced posteriorly, relative to the anterior humeral line.

The Baumann’s Angle is formed by a line perpendicular to the axis of the humerus and a line going through the physis of the capitellum. Normally, the Baumann’s angle should measure at least 11° (variable).

 

Physical Examination

It is important to assess the neurovascular structures. The anterior interosseous nerve is assessed by asking the patient to do the “OK” sign with their hand. The radial nerve is assessed by asking the patient to extend their wrist and fingers. Ulnar nerve damage is usually indicated by the loss of sensation along the little finger; however, later on the patient may have weakness of the intrinsic hand muscles and clawing.

finger extensionTreatment

Nonoperative treatment is usually indicated for type I fractures. This treatment usually consists of splinting or casting the elbow for a duration of 3-4 weeks. It is very important to remember not to flex the elbow in the splint or cast beyond 90° in order to avoid vascular compromise and compartment syndrome.

closed reductionOperative treatment is usually indicated for Types II and III, and are usually treated by a closed reduction and percutaneous pinning. During reduction, pronation of the forearm during elbow flexion helps to correct a varus deformity. After reduction, the surgeon will want to check for a gap in the fracture, as the neurovascular bundle may be trapped there. The surgeon will need to free the brachialis muscle from the fracture site if it is interpositioned there. Fixation is usually achieved with 2-3 ulnar nerve pinningdivergent lateral pins, depending on stability. Medial pins may also be added depending on stability; however, the surgeon will need to be aware of the ulnar nerve when placing the medial pin.

Open reductions are only performed when closed techniques are unable to achieve the appropriate reduction of the fracture. The surgeon will want to avoid posterior dissection in order to preserve the vascularity of the fractured segment. Fracture reduction and fixation should be done emergently in cases of vascular compromise.

Complications

Neurapraxia is a common complication of supracondylar fractures and usually resolves on its own—thus, treatment is observation only. A cubitus varus deformity may occur due to a malunion of the fracture. This only presents as a cosmetic problem since it does not affect the function of the arm or elbow. Additionally, this cubitus varusdeformity can be corrected later on by a supracondylar valgus osteotomy. Vascular problems, such as compartment syndrome, may also occur. Volkmann’s ischemic contracture may occur due to a compression of the brachial artery with then patient is placed in a cast with the arm in hyperflexion (more than 90°).

Important Scenerios

A patient may present with a Displaced Type III fracture and a pulseless hand. He may have adequate circulation—which is evident by the normal temperature and color of the hand—or he may have inadequate circulation—indicated by a cold blue hand. In both cases, an urgent closed reduction and percutaneous pinning is required. Once this has been performed and the circulation is adequate, the surgeon can observe the patient and place them in a splint that is at a 45° angle. However, if the patient continues to have inadequate circulation after the closed reduction, then the patient will require a vascular exploration and repair.

The Lateral Plantar Nerve

more nerves

The lateral plantar nerve is branch of the posterior tibial nerve, which originates from the sciatic nerve. Around the medial side of the ankle, close to the tarsal tunnel, the posterior tibial nerve divides into the medial and lateral plantar nerves. anatomy

Thickening of the flexor retinaculum will cause compression of the posterior tibial nerve, which is called tarsal tunnel syndrome. When drawing a line between the medial malleolus and the calcaneus, the posterior tibial nerve divides into branches within 2 cm from this axis. The lateral plantar nerve is interesting because its branches give innervation to most of the intrinsic muscles in the foot—similar to the ulnar nerve in the hand. The lateral plantar nerve is also important due to its first branch being the Baxter’s nerve. baxter

This nerve is always mentioned in nerve entrapment in running athletes and is associated with chronic heel related pain. The pain associated with the Baxter’s nerve is very similar to the pain associated with plantar fasciitis; the pain is in the same location, the mechanical symptoms are the same, and there is nerve pain unassociated with weight-bearing.

The first branch of the lateral plantar nerve gets compressed between the fascia of the abductor hallucis muscle and the medial side of the quadratus plantae muscle. This condition may require surgical release of the abductor hallucis fascia if conservative treatments and injections do not produce any effect.

In summary, the lateral plantar nerve:

  • Is similar to the ulnar nerve in the hand
  • Supplies most of the intrinsic muscles of the foot
  • Supplies the Baxter’s nerve branch
  • Can be injured during surgery (rod placement from the heel).

sustainAnother point of interest when it comes to the lateral plantar nerve is the hardware placement. Hardware placement prominent to the sustentaculum tali can injure the flexor hallucis longus tendon and the lateral plantar nerve.

Monteggia Fracture Dislocation

Monteggia fracture is the fracture of the proximal third of the ulna with dislocation of the radial head. The fracture is more common in children and rare in adults. Treatment will depend on the age of the patient.The normal position of the radial head and shaft should line up with the capitellum in any position. Dislocation of the radial head may be missed.

normal position

Type I Monteggia fractures occur in the middle or proximal third of the ulna with anterior dislocation of the radial head and characteristic apex anterior angulation of the ulna. This is the most common type and occurs in about 60% of cases. In children, you will immobilize the fracture in flexion and supination. Flex the elbow more than 90 degrees to relax the biceps.

Only 15% of Monteggia fractures are Type II. This fracture occurs in the middle or proximal third of the ulna with posterior dislocation of the radial head and characteristic apex posterior angulation of the ulna. You will need to immobilize this fracture in extension.

type ii

20% of Monteggia fractures are type III. These fractures occur at the ulna just distal of the coronoid process with lateral dislocation of the radial head.

Type IV only occur 5% of the time and is classified as the fracture of the proximal or middle third of the ulna with anterior dislocation of the radial head, and a fracture of the proximal third of the radius below the bicipital tuberosity. This fracture will require surgery, even in children.

TypeIVWith Monteggia Fracture Dislocations, it is important to perform a neurovascular exam. Nerve injury, especially involving the posterior interosseous nerve, is not uncommon. Additionally, you will want to watch the patient for compartment syndrome.

Treatment in adults consists of ORIF of the ulna—when the ulna is properly aligned and fixed, the radial head will reduce by itself. Radial head instability may usually be caused by nonanatomic reduction of the ulna or by interposition of the annular ligament. Fracture of the ulna may need a bone graft for healing.

platingWhen treating pediatric patients, it is important to note that the radial head ossifies around age 4. For Type I-III fractures, you will perform a closed reduction of the ulna to restore the length of the ulna and reduce the radial head. Remember to immobilize in flexion and supination. Type IV fractures or cases where you are unable to reduce the radial head or the length of the ulna in pediatrics will require surgery. Fixation will be done with an IM rod or a plate.

When treating old cases, you will perform an osteotomy of the ulna and an open reduction of the radial head, followed by plating of the ulna.