The Accessory Navicular Bone

What is an accessory Navicular Bone?

accessoryAn Accessory Navicular Bone is an extra bone that may be attached or detached from the navicular bone. It is considered a normal variant and is present in approximately 10% of people. This accessory bone is usually located under the plantar medial aspect of the navicular and is often associated with a pes planus (flatfoot) deformity. Ossification of the navicular bone occurs at three years of age in females and five years of age in males. However, the accessory navicular bone does not begin ossification before eight years of age.


The majority of patients are asymptomatic but, females tend to be more symptomatic. The patient may present with an activity related limp and pain in the arch area. The condition may also be bilateral. During examination, there may be swelling, tenderness, warmth, or redness in the plantar medial aspect of the arch. Relative to a normal foot, a plain x-ray AP view can detect the accessory navicular. An external oblique view is considered to be the best imaging position to detect an accessory navicular bone. An MRI may also be obtained in order to determine the size and type of the accessory navicular as well as assess the posterior tibial tendon.

radiologyThe accessory navicular is classified into three types. In Type I classifications, the accessory ossicle is mainly in the substance of the posterior tibial tendon and is not attached to the navicular. In Type II, the accessory bone resides very close to the navicular tubercle and is connected to the navicular by a thick layer of cartilage. In Type III classifications, the accessory bone is considered an enlarged navicular tubercle. Type IIIs are essentially a type II that is fused with the navicular by a bony bridge.

accessory typesIn regards to prognosis, when skeletal maturity has been reached, almost all patients become asymptomatic.


Nonoperative treatment usually consists of activity modification, orthotics, or a short leg walking cast. Surgical excision is indicated only after all conservative treatment options have failed.



Dislocations of the Talus

dislocationtalusA dislocation of the talus can be a total dislocation or a subtalar dislocation. There are two different main types of dislocations, total and subtalar. Subtalar dislocations are further categorized into lateral and medial dislocations.

A total dislocation of the talus that is not accompanied by a fracture is a very rare injury. Most of the injuries are open and urgent care is necessary totalin order to avoid any soft tissue complications. There is a high risk of avascular necrosis of the talus, as well as arthritis and soft tissue infection.

Subtalar dislocations of the talus are rare injuries that result from either excessive supination or from excessive pronation. It involves a simultaneous dislocation of the distal articulations of the talus at the talocalcaneal and talonavicular joints. A lateral subtalar dislocation is often the result of a high energy trauma. These dislocations have a worse long-term prognosis. Irreducible lateral dislocation due to interposed tibialis posterior tendon. Lateral subtalar dislocations can be unstable and may sublux. The physician may need a CT scan to check for fractures. 85% of the dislocations are medial and subtalaroften result from low energy trauma. Irreducible medial dislocations can be due to the interposed extensor digitorum brevis or extensor retinaculum. The direction of subtalar dislocation has important effects with respect to management and outcome. Complications of subtalar dislocations may include stiffness and subtalar arthritis.


Stable dislocations will be treated with a closed reduction. The patient should have 3-4 weeks of immobilization, followed by physical therapy. Unstable fractures will require a closed reduction; an internal fixation may be required. An anteromedial incision is used for medial dislocations and a lateral approach is used for lateral dislocations.


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


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.


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.


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.