The Posterior Interosseous Nerve acts as the extension of the broader branch of the radial nerve located in the forearm. We also know this as a dorsal interosseous nerve and reduces in size as we age.
On this article, we explain the function and location of the nerve and some information about nerve injuries. Furthermore, we offer more information when the nerve gets injured, the symptoms and the available treatments.
The Role of the Posterior Interosseous Nerve
Accordingly, the posterior interosseous nerve (PIN) branches off the radial nerve. Also, this remains responsible for innervating most of the muscles in the forearm.
After passing around the radial head the nerve, it crosses and enters the supinator muscle. The fibers of the nerve originate from spinal cord segments C7 and C8.
The Muscles with PIN
The posterior interosseous nerve innervates the following muscles:
- Extensor (E.) indicis
- E. pollicis longus
- Extensor pollicis brevis
- E. carpi ulnaris
- Extensor digiti minimi
- E. digitorum
- Extensor carpi radialis brevis
- Supinator muscle
- Abductor pollicis longus
Posterior Interosseous Nerve Injuries
Due to the location of the posterior interosseous nerve, we easily injure it. Compression, trauma, fracture, inflammation, tumors, and surgery leads to nerve damage.
When we injure the nerve, the forearm muscles get affected. The finger drop moment appears as a symptom.
When the posterior interosseous nerve compresses, it causes problems. A condition called posterior interosseous nerve syndrome (PINS) occurs once the nerve compression happens for any reason.
The condition often results in paralysis of the thumb and finger extensor muscles. Notably, the compression of this nerve commonly happens in the elbow region rather than the wrist.
The nerve gets compressed in an area of the supinator muscle known as the arcade of Frohse. Entrapment of the nerve in this area leads to posterior interosseous nerve syndrome.
The symptoms associated with PINS usually develop slowly. Many patients do not know they have the condition for a period of time. So, manage the symptoms with massage, medication, and splints.
Any type of blunt trauma to the forearm damages the posterior interosseous nerve. A heavy blow sustained in an accident or when playing contact sports puts the nerve at risk.
Blunt trauma often causes bruising and it damages tissue beneath the skin. Nerves also damage if the trauma remains heavy. Any swelling due to blunt trauma the nerve compresses until the swelling goes down.
Penetrating trauma such as a stab wound or a laceration of the forearm associated with damage to the posterior interosseous nerve. If the nerve cuts down, the function and innervation to muscles loss.
Loss of muscle function and mass remain as a possibility following penetrating trauma. The nerve damages when an IV needle enters the forearm during a medical procedure.
Any type of puncture wound near the nerve puts it at risk for injury. Medical evidence concluded that IV needles cause damage to the posterior interosseous nerve.
When fracture in the radius appears, the posterior interosseous nerve becomes susceptible to damage. Because the nerve in the forearm becomes vulnerable to injury when the bone breaks.
A fracture damage the posterior interosseous nerve in a couple of ways. The nerve severed by rough edges of a fractured bone.
The nerve gets trapped between pieces of fractured bone leading to compression. Broken fragments from the damaged radius remain as another risk factor.
Accordingly, the nerve inflammation (neuritis) implies another condition that damages the posterior interosseous nerve. Inflammation causes swelling and it affects blood flow in the affected area.
If a nerve does not receive a supply of blood, it malfunctions due to a lack of oxygen and essential nutrients.
A tumor grows anywhere in the body and fortunately, most are non-cancerous (benign). If a tumor grows near to the posterior interosseous nerve.
Once attached to the nerve, it causes damage. Muscles will be affected due to the nerve damage and blood supply to the nerve is also compromised.
Most tumors whether benign or malignant needs surgical removal and this damages the nerves. In some cases, this even remains unavoided nerve damage due to tumor removal.
Any surgical procedures carried out on the forearm put the posterior interosseous nerve at risk of injury. Post-surgical neuropathy remains as uncommon and leads to symptoms developing.
Further, it also results in a severed nerve when the surgeon makes an incision. Or else, it gets damaged when operating on surrounding tissue.
Cancer treatments including radiation and chemotherapy denote harmfulness to nerves. The treatments ascent to treat cancer but the side effects always happen.
The cocktail of drugs used for chemotherapy contains Platinum and taxane which causes nerve damage. Once the surgery utilized radiation to treat cancer it also damages nerves in the body.
Nerves in various parts of the arm remain at risk during this type of cancer treatment. The symptoms associated with posterior interosseous nerve damage include:
- Forearm and wrist pain
- Elbow pain
- Inability to extend the fingers
- Wrist and finger weakness
- Inability to extend the wrist
- Restricted thumb movement
Posterior Interosseous Nerve Damage Diagnosis
Primarily, the physician asks the patient about their symptoms before carrying out a physical examination. Then, the physician quickly diagnoses nerve damage during the initial consultation.
If the tests results tell unidentified root cause of the problem, further tests need attention. Imaging tests include X-rays, CT scans, MRI’s and ultrasound tests to look for nerve damage.
High-resolution images remain as an effective way to look at nerves when symptoms develop. A nerve conduction study (NCS) checks for damage to the PIN.
Now, the test measures how strong and fast the electrical signal in the nerve. If the signal stays weak or slows, it indicates nerve damage.
Physician use electromyography (EMG) for damage checking for to the PIN injuries. EMG translates electrical signals from muscles to determine the level of nerve damage.
Measuring the electrical activity in muscles remains an effective way to diagnose nerve injuries. Eventually, when the physician diagnosed posterior interosseous nerve damage, we need an appropriate course of action.
Treatments For Posterior Interosseous Nerve Damage
If the posterior interosseous nerve is compressed the physician may recommend physiotherapy, to begin with. Deep tissue massage and stretching is an effective way to release a trapped nerve in a non-invasive way.
If physiotherapy does not free the compressed nerve there are other options. The compression takes place due to inflammation or swelling where anti-inflammatory drugs help.
Aspirin or ibuprofen will reduce swelling which in turn frees the compressed nerve. Corticosteroids are used to relieve pain and to reduce swelling and inflammation.
When non-invasive treatments do not free a compressed nerve, surgery remains as the last option. Nerve decompression acts as a surgical procedure carried out by surgeons to free a trapped nerve.
The surgeon finds the position of the trapped nerve and makes an incision. The nerve can then be accessed and freed and any fragments of bone or scar tissue can be removed.
The procedure is effective and pain and other symptoms will ease following the surgery. If the posterior interosseous nerve has been severed there are three ways that it can be repaired.
A physician will usually wait and see if the nerve can heal by itself before electing to perform surgery. Severed nerves can regenerate at a rate of one inch per month in some cases.
In times when the nerve does not repair itself, there exists a couple of surgical solutions. A surgeon carries out end-to-end suturing where the two ends of the reconnected nerve.
When the ends have been joined the nerve will begin to regenerate and function. Another option, performing a nerve graft where physicians harvest a piece of the nerve that they use as a bridge.
The repair takes place in the piece of the nerve between the severed nerve. The physician harvests the sural nerve in the leg on the situation of a nerve graft.
This needs immediate action or else donor’s nerve suffers permanent damage. If all treatments fail, the symptoms associated with posterior interosseous nerve damage requires management.
In order for muscles in the forearm to work properly, the posterior interosseous nerve needs to be healthy. Conclusively, it affects the quality of life because of the damaged nerve and impaired muscle functions.
Unfortunately, prevention for most of the injuries to the nerve implies uneasy actions. However, proper treatment and medication work fine.