Overview of Hand Tendon Transfers
Problems with hand function can come from damage to one of three main nerves in the arm – the radial, median, or ulnar nerve. Hand function can also be affected by injury to the network of nerves in the shoulder (brachial plexus), injury to the spinal cord, damage to a specific muscle or tendon, or as a result of an illness like polio. Even fractures in the wrist that haven’t caused a bone to move out of place (non-displaced distal radius fractures) and which aren’t treated with surgery, can lead to a slow tear of the thumb-extending tendon (extensor pollicis longus).
To restore hand function caused by these conditions, tendon transfers are used. Tendon transfers are procedures where tendons (the tissues that connect muscle to bone) are moved from their original location to a new one to help regain movement.
Many of the techniques and knowledge used today regarding tendon transfers come from treating patients with paralyzed limbs due to polio and wounded soldiers during the World Wars.
Anatomy and Physiology of Hand Tendon Transfers
When the radial nerve, which runs down your arm, gets injured high up above the elbow, it can cause a few problems. At this part of the nerve, damage can lead to difficulty in extending your wrist because the muscles that usually work with the nerve are not working. Also, holding your fingers out straight might be hard because the muscles connecting them to the nerve are affected. You might even struggle to move your thumb out or extend it fully, because the nerve that controls this movement is damaged. Additionally, you might lose some feeling in the area served by this part of the nerve.
A lower injury on the radial nerve, occurring below the elbow, can also cause problems but not usually with sensation. Instead, it can cause dragging of the wrist and fingers, and difficulty in extending your thumb.
Similarly, injury to the median nerve, which is another nerve that runs down your arm, can cause problems as well. If the injury is above the elbow, it can weaken the ability to bring your thumb across your hand or bend your thumb. It may also affect how well you can bend your index and middle fingers or the joints of your fingers. It might become hard to turn your forearm or flex your wrist as this part of the nerve controls these movements too. This kind of injury can also lead to loss of feeling in the thumb, index finger, middle finger, and half of the ring finger.
If the injury to the median nerve is located below the elbow, you might find it hard to bring your thumb across your hand, and you might lose some feeling in the thumb, index finger, middle finger, and half of the ring finger.
Injuries to the ulnar nerve, another key nerve in your arm, can lead to its own set of issues if it happens above the elbow. This could affect your ability to bend your ring and little finger, make a gripping motion with your hand, or pinch things. You might also lose feeling in the little finger, half of the ring finger, and part of your palm.
An injury to the ulnar nerve at the level of the wrist can make it hard to bend your ring and little fingers or pinch things. You might also lose feeling on the inner side of the little finger and half of the ring finger.
Why do People Need Hand Tendon Transfers
Motor strength and sensory tests are used to identify and locate muscle and nerve issues. By using these tests, doctors can figure out if certain treatments, corrections, or surgeries are needed.
To test the function of your wrist, your doctor might do a wrist passive tenodesis test. This is basically taking your wrist from a bent to a straight position, and watching how your fingers move. A normal test result would show your fingers moving from a straight to a bent position as your wrist goes from bent to straight, maintaining a symmetrical pattern. If this doesn’t happen, it could indicate an injury to a tendon. It is also necessary to test the range of motion in your wrist, hand, and fingers, as full flexibility should be restored before any surgical procedures are considered.
Ulnar claw hand is a condition where the small and ring fingers are bent in a way that they look like a claw. This can happen if the forces that extend and flex your fingers are unbalanced. This is usually related to nerve dysfunction in your hand, specifically the ulnar nerve.
If the ulnar nerve is damaged at a low point, it can cause a severe form of claw hand. This is because the muscles in the ring and small fingers that pull (or flex) them remain intact, which results in an imbalance between finger flexing and extending.
If you have ulnar nerve palsy, when you try to pinch an object, your thumb might hyperextend (move too much in the opposite direction of bending) and the joint closer to the nail might bend. This happens because different parts of your hand are trying to compensate for the weakness in other muscles. This is usually diagnosed using the Froment sign.
If you have a fracture in the lower part of your forearm bone (distal radius fracture) that hasn’t caused any displacements (the bone remains aligned), your doctor may check if a tendon in your hand called the Extensor Pollicis Longus (EPL) is intact. They will ask you to place your hand flat on a table and see if you can lift your thumb. If you can’t, it might mean that this tendon has ruptured.
An EMG (Electromyography) test can help the doctor see how severe the nerve injury is, and estimate how likely the nerve will recover. This is important in deciding what treatment option is best, whether it’s a procedure to restore nerve function, or a surgical procedure called a tendon transfer which can be done whenever necessary.
When a Person Should Avoid Hand Tendon Transfers
Tendon transfer is a surgical procedure where a muscle or tendon is moved from one part of the body to another. This procedure can help to restore function to a damaged area. However, we need to take some precautions to avoid potential complications:
- The tendon chosen for this swap should not significantly impact other body functions; it should be something we can afford to move without causing more problems.
- The strength of the transferred tendon should be close to normal. It is likely that the tendon will lose some of its strength after the procedure. For example, a tendon that was previously classified as 5/5 strength may decrease to 4/5 strength after the transfer.
- The length and movability of the donor tendon should resemble those of the recipient tendon, the tendon receiving the transfer. For instance, tendons that control wrist movements have a certain length, and finger tendons can stretch a bit more. This matching is important to ensure the transferred tendon can do its job in the new location. We can also take advantage of the wrist’s swinging behaviour to make up for the difference in stretch between the hand and finger tendons.
The transferred tendon should closely follow the direction of the recipient tendon to maximize efficiency. Each tendon transfer aims to restore a single function. It’s also essential that the tissue near the transfer site is healthy and soft, allowing the tendon to easily move around. The joint controlled by the transferred tendon should be fully movable before surgery. Ideally, tendons that work together simultaneously, such as those controlling our fingers and wrists, should be kept on the same timetable if possible.
Equipment used for Hand Tendon Transfers
The treatment is usually done in a surgery room with the patient under full anesthesia. A medical device called a tourniquet is positioned high in the armpit area, and the arm is placed on a special table designed for hand procedures. The equipment needed for this procedure include a tool known as a tendon passer and a basic hand tray.
How is Hand Tendon Transfers performed
Surgical Procedures
Radial Nerve Injury
Here are the key steps to rectify radial nerve injury:
1. To achieve an extension of the wrist, the pronator teres (PT) is transferred to the extensor carpi radialis brevis (ECRB).
2. For extending finger metacarpophalangeal (MCP) joints, convenient ways include transferring the flexor carpi radialis (FCR) to extensor digitorum communis (EDC) or the flexor digitorum superficialis (FDS) of the long finger to the EDC.
3. For thumb extension, one approach is to transfer the palmaris longus to the extensor pollicis longus (EPL) or use the FDS of the ring finger for the same.
Low Median Nerve Injury
1. For achieving thumb opposition, a few techniques can be employed like the transfer of the little finger’s muscle that aids in abduction (abductor digiti minimi) to the abductor pollicis brevis (APB) or utilize the muscle that straightens the index finger (extensor indicies proprius) to the APB. These techniques attempt to restore thumb movement. Another common procedure involves restoring palmar abduction but not thumb opposition, by transferring palmaris longus to APB.
High Median Nerve Injury
1. Thumb opposition can be restored using the previously mentioned approaches.
2. Thumb IP flexion can be achieved with the transfer of the muscles that bend the wrist (brachioradialis or extensor carpi radialis longus (ECRL) or extensor carpi ulnaris (ECU)) to the flexor pollicis longus (FPL).
3. Flexion of the index finger joints (DIP and PIP) can be achieved by transferring the ECRL to the tendon that bends the most distal joints of fingers (flexor digitorum profundus (FDP) tendon of the index finger).
Ulnar Nerve Palsy
Here the aim is to correct clawing by restraining hyperextension of MCP joints which allows the extensor forces of extensor digitorum communis (EDC) to act upon the proximal interphalangeal (PIP) and interphalangeal (IP) joints. This restraining can be done using tenodesis or capsulodesis at the MCP joint level. Also, a technique named Zancolli lasso can be used or the FDS of the long finger can be modified to correct clawing. In more severe cases, the tendons that flex the wrist (like flexor carpi radialis (FCR) or ECRB) can be used for the treatment of clawing.
Power pinch can also be addressed using the ECRB or FDS for an adductor plasty. In the process of an ECRB adductor-plasty, the ECRB is detached from its insertion on the base of the second metacarpal and then it’s connected to the adductor pollicis insertion on the first metacarpal with the help of a free tendon graft. Alternatively, FDS adductor-plasty can be done in a similar fashion.
Extensor pollicis longus (EPL) Rupture
In such cases, one muscle of the index finger, the EIP, can be identified and transferred to the EPL to facilitate proper healing.
Possible Complications of Hand Tendon Transfers
When a patient needs a tendon replacement, doctors often use a process called the Pulvertaft weave to attach a donor tendon to the patient’s tendon. Think of this like weaving a thread through a fabric – the surgeon weaves the donor tendon in and out through the patient’s own tendon. Each weave is done at a 90-degree angle from the last to make sure it’s secure. Then, the doctors tie the tendons together using a sturdy stitch. They make at least three passes to ensure the connection is strong.
There could be some complications with this process. For example, the new tendon could be attached too tightly or too loosely, which could cause it to tear or come loose over time. Other methods, like spiral linking and loop-tendon suture, could be used if the surgeon thinks they’ll work better for the patient. These methods might make the tendon connection stronger, but they also make the area a little bulkier.
What Else Should I Know About Hand Tendon Transfers?
Your forearm and hand contain more than forty muscles that perform various tasks. Sometimes, these muscles may overlap in functionality. Following an injury, certain muscles may lose their ability to move correctly.
A surgical procedure known as a tendon transfer is used to improve this situation. It involves relocating a functional muscle and its attached tendon to replace a muscle and tendon that aren’t working properly. This helps improve the injured hand or forearm’s function.
