Anterior Interosseous Nerve- The Benedictine and O.K. Sign

A patient with a complete anterior interosseous nerve injury or a high medial nerve injury should be asked to make a fist. The first and second digits will have difficulty in flexing, while the other digits will flex. The third digit will be weak, while the fourth and fifth digits are normal. This position of the hand is similar to the position taken during a hand blessing. The Benedictine sign is different from an “ulnar claw hand”. Ulnar claw hand refers to damage to the ULNAR nerve and is seen when attempting to extend all the digits (leaving the 4^th and 5^th digits flexed). The O.K. sign is used to check for paralysis of the anterior interosseous nerve due to entrapment or compression injury. A patient with paralysis of the anterior interosseous nerve will be unable to make the O.K. sign. This is due to weakness of the flexor pollicis longus and flexor digitorum profundus muscles. A typical pinch attitude is associated with anterior interosseous nerve injury.

The anterior interosseous nerve arises from the median nerve about 4-6cm distal to the elbow, which is about 1/3 of the way down the forearm. It exits from the anterolateral aspect of the median nerve and it runs between the radius and the ulna on the interosseous membrane between and below the muscles of the flexor digitorum profundus and the flexor pollicis longus.

The anterior interosseous nerve supplies the flexor digitorum profundus muscle for the index and long fingers. It also supplies the flexor pollicis longus and the pronator quadratus muscles. The flexor digitorum profundus muscle for the index and long fingers is supplied by the anterior interosseous nerve. The medial part of the FDP is supplied by the ulnar nerve (FDP has dual innervation). The anterior interosseous nerve passes dorsal to the pronator quadratus with the anterior interosseous artery and provides innervation to the volar wrist capsule. The terminal branch of the anterior interosseous nerve innervates the carpal joint capsule.

In patients with Martin-Gruber Connection, the median nerve, or anterior interosseous nerve to the ulnar nerve in the forearm may present with intrinsic muscle weakness. It may be differentiated also from Parsonage-Turner Synrome (acute brachial plexus neuritis) and patient may have pain in the affected extremity. In anterior interosseous nerve entrapment, the median nerve conduction study result will be normal, however the needle EMG of the anterior interosseous innervated muscles will be abnormal.

Adhesive Capsulitis, Frozen Shoulder

Adhesive Capsulitis, or frozen shoulder, is a painful progressive loss of shoulder motion. It affects both active and passive movement of the shoulder joint. The shoulder will be stiff and painful and occurs due to inflammation, fibrosis, scarring, and contraction of the capsule. A normal shoulder joint capsule is elastic and allows great range of motion. Inflammation and thickening of the shoulder capsule and may lead to adhesive capsulitis. Frozen shoulder may occur without any specific cause, however it may be triggered by a mild trauma to the shoulder.

This condition develops slowly and goes through three phases:

1. Pain and freezing
2. Stiffness or frozen
3. Resolution

During the pain and freezing phase, the pain is worse at night and increases with any movement. This phase will last several months. During the second phase, range of motion is limited as pain is diminishing. This may last up to one year. The resolution phase may begin overtime and may last up to three years.

Conditions associated with frozen shoulder include:

• Diabetes
• Thyroid problems
• Auto immune disease
• Stroke
• Rheumatoid arthritis
• Trauma or post-surgery

A patient with frozen shoulder will have loss of both active (movement without assistance) and passive (movement with assistance) motion. External rotation of the shoulder is very limited and the condition is self-limiting and may resolve on its own. X-rays are needed to rule out degenerative arthritis.  An MRI or arthrogram will show small fluid in joint cavity. Rotator cuff may be normal and synovitis and narrowing of the rotator cuff interval is usually seen.

Treatment consists of anti-inflammatory medications, physical therapy, injections, and manipulation under anesthesia. Surgery will be done in the form of a release of the capsule when nonoperative methods fail. The physician should always check the patient for diabetes.  

Ganglion Cyst of the Shoulder

Ganglion cysts can be important when they are located around the shoulder, especially when they are located in the suprascapular notch and the spinoglenoid notch. The suprascapular nerve passes under the transverse scapular ligament at the suprascapular notch. The transverse scapular artery runs above the transverse scapular ligament. The artery and nerve joint and then pass through the spinoglenoid notch under the inferior scapular ligament. The suprascapular nerve gives branches to the supraspinatus muscle and branches to the infraspinatus muscle.

Nerve compression from a ganglion cyst at the suprascapular notch affects both the supraspinatus and infraspinatus muscles, causing a decrease in abduction and loss of external rotation of the shoulder. Nerve compression at the spinoglenoid notch affects only infraspinatus muscle, causing loss of external rotation of the shoulder with the arm to the side. Spinoglenoid notch compression is usually associated with cysts and ganglia. In addition to compression of the suprascapular nerve, these patients may also have associated posterior labral tears.

Massive Rotator Cuff Tear

To view my Youtube video, 'Massive Rotator Cuff Tear- Classic', click here.

Massive rotator cuff tears are a disabling problem. These tears can cause pain, weakness, and sometimes swelling of the shoulder. The rotator cuff consists of four muscles that function to stabilize the shoulder joint: supraspinatus rotator cuff tendon, subscapularis tendon, infraspinatus rotator cuff tendon, and the teres minor rotator cuff tendon. The supraspinatus tendon is the most common of the rotator cuff tendons to become ruptured. Massive tears of the rotator cuff that are greater than 5cm usually involving both the supraspinatus and infraspinatus tendons.

Massive tears of the rotator cuff are defined as tears greater than 5cm, usually involving both the supraspinatus and infraspinatus tendons. Retraction of the rotator cuff tendons along with muscle atrophy and fatty infiltration can occur. This makes surgical reconstruction difficult with the surgical outcome being unpredictable and less than satisfactory.

Treatment varies from physiotherapy to replacement of the humeral head. Arthroscopic or open repair is usually the selected treatment. Reconstruction can be done in selected cases. A rotator cuff arthropathy is performed on massive cuff tears that are associated with superior migration of the humeral head as well as instability and arthritis of the shoulder. The patient will have pseudoparalysis and an x-ray will show shift of the humerus proximally. An MRI will show massive cuff tear with retraction at the level of the glenoid with atrophy of the muscle and fatty infiltration. A reverse shoulder is the treatment of choice for the elderly with rotator cuff arthropathy as it improves the pain and function. Hemiarthroplasty is the treatment for younger patients. A standard head or a big humeral head can be selected.

A patient with a massive tear of the cuff usually develops weakness of the shoulder and becomes unable to actively lift the arm without assistance. Fluid collection within the shoulder may occur with a massive tear of the rotator cuff.

Examination of the Acromioclavicular Joint

The acromioclavicular joint is located at the top of the shoulder, where the acromion of the scapula and the clavicle join together. The AC joint is a small synovial gliding joint that can be affected by arthritis and osteoarthritis. The oblique orientation of the joint’s articular surfaces may allow the acromion to be driven underneath the clavicle when the AC joint is injured. The condition could be subtle. Injuries of the acromioclavicular joint most commonly occur due to separation of the AC joint. Falling directly onto the shoulder can injure the ligaments that stabilize the AC joint. The AC ligament provides anterior-posterior stability of the AC joint. The posterior and superior AC ligaments are most important for stability. The coracoclavicular ligaments provide superior-inferior stability. Activity related pain with overhead activity and arm adduction.

During the physical examination, in order to test for injury to the AC joint, the physician will begin by palpating the AC joint. They should check to see if pain is present with direct palpation of the AC joint. If pressing down onto the AC joint causes pain, this is a sign of an AC joint problem such as distal clavicle osteolysis, arthritis, sprain of the AC ligament, or separation. Osteolysis of the distal clavicle is a localized area of inflammation, hyperemia, microfracture, bone resorption, and eventually arthritis of the AC joint. When pulling down on the shoulder, if there is a separation of the AC joint, the clavicle will rise and a bump will be seen in the area of the joint. Sometimes, this is demonstrated by adding weights and comparing both sides. The cross body adduction test can also be done by bringing the shoulder across the body. This squeezes the acromion and clavicle together, causing pain directly in the area of the joint if an AC joint separation or arthritis is present.

The acromioclavicular joint is best evaluated using the Zanca view radiograph. Using the Zanca view, the x-ray beam is directed with a cephalad angle of 15 degrees. Clavicular osteolysis can be assessed using the Zanca view. The acromion will be normal with the abnormality isolated to the distal clavicle. The Zanca view is also used for diagnosis of arthritis of the AC joint. It can show osteophytes and joint space narrowing. The patient’s symptoms may not correlate with the x-ray findings. An MRI will show an increased signal and edema in the AC joint.

Elbow Joint Dislocations

An Elbow dislocation occurs when the radius and ulna bones of the forearm move out of place from the humerus bone of the upper arm. There are two basic types of elbow dislocations:

1. Simple

   No fracture of the bones around the elbow joint

   Usually ligamentous injury

2. Complex

   Fracture has occurred along with ligamentous injury

Simple elbow dislocations typically occur when the patient falls onto an outstretched hand. Injury progression from lateral to medial in most patients. Posterolateral simple dislocations are the most common, occurring approximately 90% of the time.

The proximal ulna and radius are displaced posterolaterally relative to the distal humerus. Postemedial dislocations occur at the proximal ulna and radius and are displaced posteromedially relative to the distal humerus. In medial dislocations, the proximal ulna and radius are displaced medially relative to the distal humerus. With lateral dislocations, the proximal ulna and radius are displaced laterally relative to the distal humerus. Anterior dislocations are rare, as they result from a direct force applied to the posterior aspect of the forearm with the elbow in a flexed position. Anterior dislocations occur when the proximal ulna and radius are displaced anteriorly relative to the distal humerus. If stable, simple acute fractures can be treated with a closed reduction and a splint for two to three days (no more than two weeks) in addition to range-of-motion exercises and physical therapy. Unstable simple fractures are rare, but can be stabilized by ligament repair and/or by the use of an external fixator or cross pinning of the joint in the elderly.

Chronic Elbow dislocations will need to be treated with an open reduction and external fixator and is usually hinged. Recurrent elbow dislocations (diagnosed by pivot shift) occurs due to a deficiency of the lateral collateral ligament and is treated by a reconstruction of the ulnohumeral ligament with a tendon graft.