Hands have a very delicate and complex structure. This gives muscles and joints in the hand a great range of movement and precision. The different forces are also distributed in the best possible way. Thanks to this structure, you can do a wide range of things with your hands, such as grip objects tightly and lift heavy objects, as well as guide a fine thread through the tiny eye of a needle.
The median nerve innervates some of the major muscles of the forearm and hand, which allows for two-way communication between the brain and spinal cord, and the muscles and overlying skin. The brain and spinal cord can send signals through the medial nerve, to the muscles that it innervates, with instructions on when to contract and complete specific actions. Similarly, the muscles and overlying skin can transmit sensations and sensory information, such as heat and pain, through the median nerve, and back to the brain and spinal cord for processing.
Ape hand (also called Simian hand) is a deformity of the thumb characterized by an inability to abduct the thumb or to extend the thumb parallel to the plane of the fingers (the thumb usually extends perpendicular to the palm). Generally, Ape hand is caused by median nerve injury (also called median claw lesion) which causes wasting of the muscles of the thenar eminence; so the palm appears flattened with an extended thumb. Supposedly, this name is derived due to its resemblance to an ape’s hand. However, the term “Ape hand deformity” is a misnomer since apes have opposable hands. The opposable thumb is indispensable to men. The opposition of the thumb refers to the rotation of the thumb along its long axis such that it can touch each fingertip of the same hand.
Ape hand involves a limited range of motion in the thumb. Claw hand, however, is a condition in which the fingers are noticeably curved or bent. Other common causes of Ape hand include a congenital defect, a defect present at birth, and certain disorders such as diabetic neuropathy.
Causes & Symptoms
Ape hand is normally the result of median nerve palsy, which is commonly caused by deep injury to the wrist or forearm. This can impair the function of the thenar muscles.
The median nerve runs down the length of the arm, starting near the shoulder. It runs through the forearm, traveling through the carpal tunnel into the hand. This nerve also begins near the shoulder and runs down the arm length supplying flexors of the forearm and muscles of the hand, including the thenar muscles and two lateral lumbricals. It also supplies sensory innervations to the lateral palm and three and a half fingers. Additionally, studies have shown that median nerve mononeuropathy is the most common peripheral neuropathy throughout the population. It can occur due to myriads of causes. The two most common causes of median nerve injury (i.e. Ape hand) include:
- Traumatic fractures or penetrating injuries
- Chronic compression
As the nerve runs through the entire length of the hand. The nerve lesion can be a proximal lesion or a distal lesion. The motor and sensory deficits are produced due to a distal nerve lesion either near the elbow or wrist. In most cases, the thumb is rotated and adducted.
The lesion causes a wasting of the following thenar muscles, including:
- Adductor pollicis
- Abductor pollicis brevis
- Flexor pollicis brevis
- Opponens pollicis
Who Gets Ape Hand?
Overall, there are no well-identified risk factors for the development of Ape hand, however, some of these factors include the following:
- Ape hand can be a congenital condition, meaning it may be inherited or even acquired.
- Men are more prone to develop this condition rather women.
- The congenital form of an Ape hand is common in both men and women.
- There is no racial or ethnic preference observed.
How Does It Affect You? How Serious Is It?
There are a few other hand deformities akin to Ape hand deformity – these include:
Carpal Tunnel Syndrome – If the median nerve gets compressed in the carpal tunnel in the wrist, it causes carpal tunnel syndrome.
Motor deficits – Impaired flexion of the thumb, index, and middle finger, and ring finger, sometimes even in the forearm.
Sensory deficits – Tingling, numbness, and pain in the thumb, index finger, middle finger, and ring finger, sometimes even in the forearm.
Hand of Benediction – Also known as “Preacher’s Hand”, it occurs due to a proximal lesion of the median nerve if the compression is in the forearm or at the elbow.
Trigger Finger – Trigger finger occurs when a finger or thumb gets stuck in a bent position. Tendons in the thumb or fingers get inflamed due to repetitive or forceful movement, which causes stiffening.
Claw Hand – Often confused with Ape hand, Claw hand can also be caused later in life due to any injury to the arm, diabetic neuropathy, or can be present at birth.
De Quervain’s Tendinosis – Inflammation of certain tendons of the thumb due to repetitive movement or rheumatoid arthritis causes a condition called De Quervain’s Tenosynovitis. It is characterized by pain and tenderness at the base of the thumb.
Pronator Syndrome – Pronator syndrome occurs when the pronator teres muscle compresses the median nerve in the forearm. Some patients also complain of a loss of sensation over the thenar muscle including discomfort in the forearm during activity.
Other complications of Ape hand include:
- Functional loss of the hand, resulting in an inability to perform basic functions.
- Difficulty opening one’s hand.
- Difficulty gripping large objects.
Recommended Treatment & Rehabilitation
Upon physical examination, a patient may find a “bottle sign” when a person grasps a long cylindrical object in his hand; there is some gap present between the skin of the hand and the object. Bottle sign is related to the weakness of the thenar muscles due to nerve injury. After the history and physical examination, the following diagnostic procedures can be used:
- Nerve conduction velocity – This can detect any impairment in the median nerve conductance.
- Electromyography (EMG) – Any pathology of the muscles innervated by the median nerve can be determined. This will also help to exclude other causes such as polyneuropathy.
Management mainly depends upon the etiology of median nerve injury. In the case of carpal tunnel syndrome, splints can be used. Some other conservative therapies for ape hand include:
- Avoiding repetitive hand and wrist movements
Generally, hand therapy exercises can help improve strength and dexterity in the hands and fingers. They are especially helpful for improving finer motor skills after a neurological event like stroke or brain injury. Furthermore, hand strengthening exercises may also help prevent conditions like arthritis from worsening. For those with mild Ape hand injuries, you should start with passive exercise. This means using your unaffected hand to help your affected hand complete the exercises. These certain exercise examples for hand injuries (including Ape hand) include:
- Wrist extension and flexion – For this gentle hand dexterity exercise, begin with your forearm on a table. Let your hand hang off the side of the table with your palm down. Then, move your hand up and down, bending at your wrist. When finished, repeat with your palm facing upwards.
- Thumb extension and flexion – Begin with your palm open, as if you were signaling the number five. Then, practice moving your thumb over to your little finger, signaling the number four. Continue to move your thumb back and forth between these two positions.
- Wrist stretch – With your fingers still interlaced, gently bend your affected wrist backwards and get a nice stretch there. Finally, hold this stretch for 20 seconds and release. It is recommended to repeat on the opposite side.
- Inner arm stretch – Place your hands on your lap and interlace your fingers. Then stretch your affected arm palm-side up. You should feel this stretch up to your inner arm. Hold this stretch for 20 seconds and release, then repeat on the opposite side.
- Palm up and down – Place your hand palm-up on a table. Afterwards, use your non-affected hand to flip your hand palm down. This helps improve hand and wrist mobility. Repeat this exercise 10 times a day.
For some affordable and effective hand strengthening exercises, it’s worth getting a set of hand therapy balls. They usually come in different thicknesses so that you can keep yourself consistently challenged. Therapy ball exercises include:
- Table roll – Roll the ball up and down your palm by flexing (making your thumb bent) and extending (making your thumb straight). This will move the ball up and down your hand in a somewhat straight motion.
- Pinch – Pinch the ball with fingers and the thumb extended. Press your fingers down into the top of the ball and your thumb upward on the bottom of the ball. If this exercise is making your hand feel uncomfortable, try using a firmer therapy ball.
- Power grip – For a basic hand strengthening exercise, squeeze a therapy ball with your fingers and thumb. Focus on pressing the pads and tips of your fingers into the ball. Lastly, pick a ball with thickness for a higher challenge.
The general treatment for Ape hand includes both non-surgical and surgical methods, and this may depend on the cause. Non-surgical treatment measures for the acquired forms of Ape hand include:
- Non-steroidal anti-inflammatory oral medications – such as indomethacin and naproxen, may be used to help decrease the pain and swelling.
- Complete immobilization – of the hand with a cast may be required in order to restrict movement.
- Corticosteroids injections – may help provide temporary relief of symptoms and improve the range of motion.
- Physiotherapy – after symptoms have abated, it is very important to begin some light motion exercises. Physiotherapy may help restore strength, flexibility, and function of the hands. This can also be used for a congenital form of an ape hand.
Surgical treatment for Ape hand involves fixing the underlying issues contributing to the deformity. This can include nerve problems, tendon abnormalities, and scar tissue.
Alternative & Homeopathic Treatment
For patients with some hand movement regarding Ape hand, try these simple tasks that involve common household items. These are great for hand strengthening occupational therapy at home. Some of these homeopathic treatments include:
- Stacking coins – Grab a handful of loose change and practice stacking coins on top of each other. This will help improve coordination and fine motor skills. Try to stack the coins by size. Put the largest coins at the bottom.
- Pinching clothespins with each finger – To gently improve finger strength, take a clothespin and practice pinching it with different fingers. Begin with your thumb and index finger, ring finger, then pinky. Using your thumb, index finger, and middle finger is a functional tripod grip.
- Playing board games – If you want to make things more fun and interesting, play board games like checkers or chess which require you to practice your fine motor skills as you move your pieces and activities your brain for scanning, decision making, and sequencing tasks.