What is Intrinsic Hand Deformity?
Our hands are capable of performing an impressive range of tasks. They give us the ability to carry out both broad and detailed movements with precision. From gripping an item firmly to performing delicate tasks, all these functions are possible because of the stability and mobility provided by the bones, muscles, and nerves in our hands.
Hand function is very important for our daily activities – how well we do our jobs and participate in various physical tasks. If the muscles inside our hands become impaired, it can reduce the strength of our grip and may also cause deformities. This can significantly impact the quality of our lives by limiting our ability to do things independently and participate in different physical activities.
What Causes Intrinsic Hand Deformity?
Hand impairment can be caused by two primary problems. The first is ‘intrinsic palsy’, or an ‘intrinsic minus hand’, which is damage to certain muscles in the hand. The second is ‘intrinsic contracture’, or an ‘intrinsic plus hand’, where these muscles become unusually rigid and hard to move. This can happen due to trauma, which is the most common reason. This often accompanies fractures in the hand or extra swelling and blood supply issues, such as those seen when there’s a ‘compartment syndrome’, a painful and dangerous condition caused by pressure buildup from bleeding or swelling after an injury. These issues can result in the formation of scar tissue and the hardening of these specific hand muscles and tendons.
There are also other reasons for ‘intrinsic contractures’. These include issues related to abnormally increased muscle tension due to a brain disorder such as a stroke, cerebral palsy, traumatic brain injury, Parkinson’s disease, or conditions affecting the joints like rheumatoid arthritis, osteoarthritis, and arthrogryposis, a condition causing joint stiffness and muscle weakness from birth.
Damage to the ulnar nerve, one of the three main nerves in your arm, due to a traumatic injury is the most common cause of ‘intrinsic palsy’. Other reasons can involve the compression of this nerve somewhere along its path in the arm, often known as ‘compression neuropathy’, complications due to ‘compartment syndrome’, diseases in the brain and spinal cord, autoimmune diseases affecting the joints like rheumatoid arthritis, infectious diseases like Leprosy, inherited nerve conditions like Charcot-Marie-Tooth disease, poor healing due to not wearing a splint after injuring the hand, or not keeping the hand in the ‘intrinsic plus posture’, a position that relaxes the muscles after a severe hand injury.
Risk Factors and Frequency for Intrinsic Hand Deformity
Trauma often causes intrinsic contractures and paralysis, particularly in the case of nerve injuries. These injuries, which may affect the ulnar and median nerves, can cause significant harm for young, active people by leading to both sensory and motor impairments. Men are more commonly affected by this type of hand deformity than women, and around 22% of nerve injuries in the volar forearm involve combined injury.
Carpal Tunnel Syndrome (CTS) is the most frequently occurring nerve entrapment condition, affecting 1 to 3 people out of 1000 each year. The ulnar nerve’s compressive neuropathy is the second most frequent after CTS, with an incidence rate of 25 to 28 cases per 100,000 people each year.
- Trauma can often result in intrinsic contractures, and paralysis.
- Nerve injuries, particularly in the ulnar or median nerves, are common.
- Such injuries can lead to sensory and motor impairments, especially in young, active individuals.
- Hand deformities resulting from trauma are more common in men than women.
- About 22% of nerve injuries in the volar forearm involve both types of injury.
- Carpal Tunnel Syndrome (CTS) affects 1 to 3 people out of 1000 every year, making it the most common nerve entrapment condition.
- The second most common nerve entrapment is compressive neuropathy of the ulnar nerve, which affects 25 to 28 people out of 100,000 each year.
Signs and Symptoms of Intrinsic Hand Deformity
Intrinsic muscle palsy mostly comes from ulnar nerve dysfunction. Our nerves can be harmed in different ways. If the injury is quite low, it can impact the sensibility or feeling in your fourth and fifth fingers. This could also affect the muscles in those fingers, resulting in a change of hand posture known as the intrinsic minus or claw posture. If the muscles in your fingers are weak, you could lose about 60% to 80% of your pinch and grip strength. Various signs can indicate this weakness. For instance, if you try to pinch something with your thumb and second finger and feel abnormal flexion, it could imply muscle weakness.
Median nerve injuries can lead to unique changes in hand posture too. High median nerve injuries usually result in the hand turning towards the little finger (ulnar deviation) or flattening out (supination). Some specific muscle groups in the hand can be affected by this kind of injury, leading to specific finger and thumb movements being weakened. Low median nerve injuries affect how the hand can make a fist, amongst other things, because they preserve the movements controlled by the muscles outside of the hand (extrinsic muscle function).
The muscles inside your hand (intrinsic muscles) are important because they enable you to flex your knuckles and straighten your fingers. When the muscles work in harmony, a health care provider can move your joints around without much resistance. However, if your intrinsic muscles are contracted or shortened, resistance or limitation in the movement can occur. Therefore the intrinsic tightness test, as first described by Sterling Bunnell in 1948, is an important maneuver for checking the health of the intrinsic muscles in your hand.
It’s important to remember that, if the muscles become overly tense because of overstraining, you might struggle to flex these small joints. People who suffer from this kind of muscle contracture often complain about weakness and might struggle with grabbing large objects.
Testing for Intrinsic Hand Deformity
A detailed physical examination is vital for diagnosing issues related to your hand and fingers. During their examination, the doctor will pay close attention to the movement ability, finger position, and any signs of muscle shrinkage or atrophy.
The doctor will assess muscle strength and function through various methods, such as comparing the muscle power in both hands, asking you to hold a sheet of paper between your fingers while they attempt to pull it away or asking you to perform specific finger movements against resistance.
If there is nerve damage — especially in the ulnar nerve, which provides sensation to your hand and fingers — the cause could be various forms of injuries such as cuts, stretching, or contusions (bruising). It’s crucial to determine the type and severity of nerve damage you have as it informs the course of treatment required. Some types of nerve injuries can be managed without surgery, while others may require surgical intervention.
Electrodiagnostic tests can help determine the extent of the injury, but the findings can depend on the time elapsed since the injury occurred. For instance, tests done immediately after the injury can help pin-point the exact location of the damage, while tests done one-to-two weeks after the injury can determine if the injury is partial or complete. Tests done around three or four weeks after the injury can differentiate between the types of nerve damage, and tests done after a few months can show signs of nerve healing or reinnervation.
High-resolution imaging procedures like ultrasound and MRI can also be used. They can accurately identify any nerve breaks, presence of nerve thickening (neuromas), or scar tissue around the injury site.
Treatment Options for Intrinsic Hand Deformity
Treating ‘intrinsic plus hand,’ a condition where the fingers assume a claw-like shape due to muscle contractures, depends on the cause. Physiotherapy is usually the first option, particularly for mild cases. If there are stiffness and tension involving the joint near the tip of the finger, a procedure called ‘distal intrinsic release’ might be used. This involves cutting some of the muscle fibers to ease the tension.
There are other treatment options if this tension extends to the joint in the middle of the finger. These include a ‘proximal intrinsic release,’ which is similar to a distal release but targets fibers closer to the hand; an ‘intrinsic muscle slide’, which aims to relocate muscle tissue, and using an injected form of botulinum toxin (often recognized from its use in Botox) to relax the muscles. Another option is an ‘ulnar nerve motor branch neurectomy,’ which involves removing a portion of the nerve responsible for controlling the hand muscles.
In the case of ‘intrinsic minus hand’, usually caused by an injury, prompt treatment involving repairing the injured ulnar nerve (a major nerve running down the arm) is necessary. However, if the injury site is contaminated, the repair might have to be delayed for a few days. If the nerve damage is from non-traumatic causes, further investigation is needed. In cases where a nerve injury can’t be corrected, a technique called distal nerve transfers can be used, which involves diverting other functioning nerves to take over the tasks of the damaged one.
For severe paralysis of the hand muscles, treatment is usually considered when the hand still has a weak grip strength 1 to 2 years after the initial corrective methods have been exhausted.
To correct the ‘claw hand’ deformity caused by this condition, various methods can be used, both passive (intended to restore some functionality to the hand muscles) and active (aiming to bring back normal function). The chosen procedure depends on various factors like the extent of paralysis and the flexibility of the hand joints and tendons.
Tendon transfers can re-establish thumb movement. One method involves using a tendon from the forearm, threaded through the wrist and attached to the thumb. Hand splints can be used to prevent over-extension of the affected joints.
Surgical procedures involve moving or altering tendons, muscle fibers, and other tissue to correct the deformity and restore the function of the fingers. Procedures can aim to restore active finger movement or to prevent overextending certain joints in the fingers.
What else can Intrinsic Hand Deformity be?
When examining a person for possible ulnar nerve paralysis or hand tightness due to an injury or body-wide event, other hand-related health issues should be considered. These can include:
- High ulnar nerve injuries leading to neuropathy
- Compression of the anterior interosseous nerve causing neuropathy
- Parsonage-Turner syndrome
- Inflammation of the network of nerves in the arm (brachial plexus neuritis)
- Carpal tunnel syndrome
- Pronator syndrome
- Stiffness in the forearm due to lack of blood flow (Volkmann’s contracture)
- Dupuytren’s contracture, causing fingers to bend inward
If a patient is diagnosed with complete ulnar nerve paralysis, they should show absolutely no muscle activity in the muscles controlled by the ulnar nerve. If a patient with a confirmed complete ulnar nerve injury still shows signs of partial paralysis, it might suggest an unusual connection (called Martin-Gruber anastomoses) between the anterior interosseous nerve and ulnar nerve. This unique condition is found in about 15% of people.
What to expect with Intrinsic Hand Deformity
Generally, younger patients and those with less severe injuries, who get their nerve lacerations fixed immediately, have a better chance of recovery. However, older patients, those with severe injuries, and those suffering from chronic ulnar compressive neuropathy, which is an injury associated with muscle wasting, may find it harder to recover fully. Moreover, patients with claw hand, where the hand bends towards the wrist, have a better chance of improvement if a surgical procedure to prevent the overextension of the MCP joint is performed.
Most treatments for these conditions offer relief rather than a complete cure, and significant improvement in hand function could take up to 5 years after the surgery.
Possible Complications When Diagnosed with Intrinsic Hand Deformity
If you keep your intrinsic hand muscles tensed for long periods, this can limit the extension of your metacarpophalangeal (MCP) joints, causing your fingers to curve in a shape resembling a swan’s neck. If a mild claw hand deformity – where your fingers are bent into the shape of a claw – is left untreated, it can worsen and involve all your fingers.
Conditions that may occur:
- Decreased extension of MCP joints – your fingers cannot fully straighten
- Swan neck deformity – your fingers curve like a swan’s neck
- Progression of a mild claw hand deformity – your fingers are bent like a claw and this can affect all of them if not treated
Preventing Intrinsic Hand Deformity
Learning about your hand surgery is very important. We want you to ask questions and understand everything about your condition and the treatments you’re receiving. This information can help you live a better quality life and avoid any serious problems.
