What is Claw Hand ?
Ulnar nerve palsy can cause a loss of feeling and movement. This can happen if any part of the ulnar nerve gets injured. The ulnar nerve is the final offshoot of the medial cord (C8, T1), which controls the flexor carpi ulnaris and the flexor digitorum profundus muscles once it passes through the cubital tunnel.
This nerve is responsible for feeling in the inner half of the fourth finger, all of the fifth finger, and the part of the back of the hand nearest the ulnar bone.
Ulnar nerve controls the following muscles:
* Abductor digiti minimi
* Flexor digitorum profundus
* Flexor digiti minimi
* Opponens digiti minimi
* Ring finger lumbricals
* Small finger lumbricals
* Dorsal and palmar interosseous muscles
* Adductor pollicis
* Deep head of flexor pollicis brevis
If the ulnar nerve gets damaged, the muscles it controls start to lose strength. This leads to an uneven balance between the stronger outer muscles (like the extensor digitorum communis) and the weakened inner muscles (such as the interossei and lumbricals). This imbalance can lead to overextension of the joints of the palm (MCP) and the bending of the joints of the fingers (PIP and DIP). After carpal tunnel syndrome, damage to the ulnar nerve is the second most common nerve disorder of the upper limbs.
The ulnar nerve can become trapped in a number of different places. It happens most commonly in the cubital tunnel. Other typical sites include the medial intermuscular septum, the ulnar groove in the epicondylar region, and the deep flexor pronator aponeurosis. If the ulnar nerve gets trapped in Guyon’s canal, it causes ulnar tunnel syndrome.
What Causes Claw Hand ?
Claw hand can be caused by anything leading to ulnar nerve palsy, or malfunction. This can happen due to a cut along the path of the ulnar nerve or injuries high up on the inside cord of the network of nerves in the upper arm, which may even lead to a loss of feeling in the hand. Claw hand also can be a result of cubital tunnel and ulnar tunnel syndromes, which are conditions where the nerves are squeezed at your elbow or wrist.
Other factors contributing to ulnar nerve palsy can be failure to properly brace the hand after a significant injury, like a crush accident. A few systemic diseases such as leprosy, syringomyelia, and Charcot-Marie-Tooth disease also can cause the malfunction of this nerve. However, these diseases usually affect more than one nerve.
When claw hand occurs, it is generally due to paralysis of the muscles in the hand known as the lumbricals.
Risk Factors and Frequency for Claw Hand
Claw hand is a condition that can either be present from birth, known as congenital, or can be acquired later in life. Men have a higher chance of developing this condition, but when it comes to the congenital form, it equally affects both men and women. This condition doesn’t favor any particular race or ethnicity.
Signs and Symptoms of Claw Hand
If someone has an ulnar nerve palsy, they might notice a decrease in the normal function of their hand. This problem tends to cause hyperextension in the main joints of the hand, and flexion in the smaller, inner joints.
Interestingly, the fourth and fifth fingers tend to be more affected by this condition than the second and third fingers. This is due to the fact that these fingers are regulated by different nerves. The second and third fingers are controlled by the median nerve, while the fourth and fifth fingers are controlled by the ulnar nerve.
People with ulnar nerve palsy may also find it difficult to grasp, grip, or pinch objects. Additionally, they may exhibit certain characteristic signs when the main joints of their hand are flexed. This maneuver tends to correct any deformities that may have developed in the smaller, inner joints of their hand.
There are several specific tests that doctors can use to diagnose ulnar nerve palsy. Some of these tests include:
- Froment sign: The person is asked to pinch an object. If the joint of their thumb bends excessively, it suggests that they may be using the flexor muscle of their thumb (controlled by the median nerve) to compensate for a weakness in the adductor muscle (controlled by the ulnar nerve).
- Jeanne sign: In this test, if the person’s thumb joint hyperextends while trying to pinch, it indicates the use of flexor muscle as a replacement for the adductor muscle.
- Wartenberg sign: Checks for the abduction of the small finger at the main joint, which implies a deficient muscle in the palm controlled by the ulnar nerve.
- Duchenne sign: Highlights specific issues with certain muscles in the ring and small fingers, which might include overextension of the main joints and flexion of the inner joints.
Testing for Claw Hand
Tests that measure muscle activity and nerve signals, known as electromyographic and nerve conduction velocity studies, are often used to investigate issues with the ulnar nerve. These tests can also help doctors confirm or rule out other potential diagnoses.
Treatment Options for Claw Hand
If a patient’s finger joint is bent more than 45 degrees and can’t straighten, a non-surgical treatment may be applied. This usually involves a rigorous hand therapy program where the hand is put in a series of casts over time.
Exercises are introduced that aim to strengthen specific hand muscles and improve finger movement. Each finger and thumb is exercised in different directions while the hand is turned palm side down. Over time, through these exercises, certain muscles in the hand become stronger.
However, most cases eventually require surgery, especially when the condition is getting worse and impacting a person’s quality of life. The main goal here is to prevent a situation where the first joint of the fingers over-extends permanently.
Various types of hand surgeries involve moving tendons, which are the tissues connecting muscles to bones. These surgeries help address various issues such as difficulty in moving the thumb towards the index finger, an abnormal bending of the fingers that hinders grabbing things, and the inability to bend the ring and little finger.
In one type of surgery, tendons from a few specific muscles can be used to restore thumb movement. The same surgery can also help when it is needed to rebuild structures in the fingers.
To correct abnormal finger bending, surgeons can either perform a static procedure or use a technique that moves tendons from donor muscles. And to restore function to the ring and small finger, a specific tendon transfer is performed.
What else can Claw Hand be?
When diagnosing a “claw hand” condition, doctors might consider the following medical conditions that could cause similar symptoms:
- Neck nerve damage or impingement (Cervical radiculopathy)
- Dupuytren’s contracture, a hand deformity
- Klumpke paralysis, a form of paralysis involving the muscles of the forearm and hand
- Lower brachial plexopathy, a nerve issue in the lower part of the brachial plexus, which controls your shoulder, arm, and hand.
The healthcare provider would consider these possible diagnoses and conduct the necessary assessments to make a sure diagnosis.
What to expect with Claw Hand
The outlook for recovery really depends on the nature and extent of the nerve damage. In the case of mild nerve injuries, it’s possible for the person to fully recover. However, if the nerve has been completely cut, a full recovery is unlikely.
Even for those who do recover, they might need prolonged hand therapy and they might never regain the full strength in their hand muscles. Certain factors can worsen the prognosis, these include being older, having diabetes, not having a sensory response, and experiencing muscle wasting.
According to some studies, there might be little improvement even after a surgical procedure that moves the ulnar nerve to a different location.
Possible Complications When Diagnosed with Claw Hand
Tendon transfers within the hand can be tricky and complications may arise more frequently compared to other procedures such as adductor-plasty. This is primarily due to the complex and delicate balance of the extensor hood mechanism.
If the muscle selected for the transfer lacks adequate strength or movement range, the surgery may not be successful. Another common issue is elongation of the tissues when connecting the transferred tendon into the extensor hood’s lateral bands.
Transfers that fail due to lack of strength can sometimes be corrected through therapeutic muscle strengthening. However, it’s not uncommon for a corrective operation to be required.
If on the other hand, the chosen muscle is too strong or has a limited range of motion, the results may also be unsatisfactory. Sewing the tendon too tightly can lead to a condition known as swan-neck deformity of the finger.
Tight or overly strong tendon transfers can be managed using passive range of motion therapy. This supports stretching and relaxation of the tissues to alleviate the tightness.
Potential issues:
- Balancing the extensor hood mechanism
- Choosing a muscle with insufficient strength or movement range
- Elongation during sewing into the lateral bands of the extensor hood
- Failing tendon transfers due to insufficient muscle strength
- Need for a corrective surgery in case of failure
- Choosing a muscle with excessive strength or limited range of motion
- Sewing the tendon too tightly into the lateral band
- Swan-neck deformity of the finger due to too tight or strong tendon transfers
- The need for passive range of motion therapy for overly tight or strong tendons
Recovery from Claw Hand
An expert hand therapist is crucial in the aftercare of patients who undergo tendon transfers for ulnar nerve palsy. They ensure the proper use of custom splints for protecting the transferred tendons, while also enabling mobility in unaffected joints. This involves strictly following certain care procedures after surgery. Typically, the hand is kept still for around 3 to 4 weeks post-operation. Afterwards, a special type of splint is used that lets the hand move within its confines for another 3 to 4 weeks. Passive exercises for the hand start around the 6-week mark, with strengthening exercises beginning at week 8 for the adductor-plasty procedure and week 10 to 12 for intrinsic tendon transfers.
Preventing Claw Hand
Patients should be informed about their health outlook and, if necessary, the importance of regular visits to a physiotherapist. This helps in the timely recovery and management of their condition.