UPPER EXTREMITY NERVE ENTRAPMENTS AND INJURIES



Musculocutaneous Nerve
o Entrapment Point 1 - Coracobrachialis Muscle (upper arm): The musculocutaneous nerve can be
compressed as it pierces the coracobrachialis muscle. This can result in weakness of the elbow
flexors (brachialis and biceps brachii) and forearm supinator (biceps brachii), and sensory loss over
the lateral forearm.
o Entrapment Point 2 - Bicipital Aponeurosis (cubital fossa): This is also known as the Lacertus
Fibrosus. Entrapment here is uncommon but can occur, resulting in sensory loss in the lateral
forearm and potentially mild weakness in elbow flexion and forearm supination.
o Common Injury 1 - Direct Trauma or Injury (upper arm): A severe blunt or penetrating injury to the
upper arm can damage the musculocutaneous nerve. This can result in weakness or paralysis of the
biceps brachii, brachialis, and coracobrachialis muscles, leading to difficulties in elbow flexion and
forearm supination.
o Common Injury 2 - Fracture (upper arm): A fracture to the upper arm (humerus) can potentially
injure the musculocutaneous nerve. This could lead to sensory loss over the lateral forearm and
motor loss in elbow flexion and forearm supination.
o Common Injury 3 - Iatrogenic Injury: This refers to an injury that occurs as a result of medical
procedures or treatments, such as surgery or injections in the upper arm. This could lead to sensory
and motor deficits similar to those described above.
o Please note, the musculocutaneous nerve is less commonly entrapped or injured compared to other
peripheral nerves, and these scenarios represent potential but relatively rare occurrences.
Median Nerve
o Entrapment Point 1 - Carpal Tunnel (wrist): When the median nerve gets compressed at the wrist, it
can lead to Carpal Tunnel Syndrome. This results in numbness, tingling, and weakness in the hand
and fingers, particularly the thumb and the first three fingers.
o Entrapment Point 2 - Pronator Teres Syndrome (elbow): Here, the median nerve is compressed at the
elbow. This can lead to pain in the forearm and hand, numbness and tingling in the palm, thumb, and
first three fingers, as well as weakness in hand grip.
o Entrapment Point 3 - Anterior Interosseous Nerve Syndrome (forearm): This condition occurs when
the anterior interosseous branch of the median nerve is compressed. Symptoms can include
weakness in the thumb and index finger, making it difficult to pinch or hold objects.
o Common Injury 1 - High-level Median Nerve Injury (near the elbow or upper arm): This can result
in an inability to pronate the forearm, weakness in flexion of the wrist and fingers, and loss of
sensation in the thumb, index, and middle fingers, leading to a condition known as 'Ape Hand
Deformity.'
o Common Injury 2 - Low-level Median Nerve Injury (wrist level): This often results in loss of thumb
opposition, abduction, and flexion, leading to 'Hand of Benediction' or 'Pope's Blessing' when trying
to make a fist. This is because the affected person cannot flex the index and middle fingers while the
other fingers can be flexed.
Ulnar Nerve
o Entrapment Point 1 - Cubital Tunnel (elbow): When the ulnar nerve is compressed at the elbow, it
can lead to Cubital Tunnel Syndrome. This can result in numbness and tingling in the ring and little
fingers, weakness in the hand, and difficulty with fine movements.
o Entrapment Point 2 - Guyon's Canal (wrist): This is also referred to as Ulnar Tunnel Syndrome.
Compression at this point can cause numbness and tingling in the ring and little fingers, weakness in
the hand, and can potentially lead to a condition known as 'claw hand' if severe and untreated.
o Entrapment Point 3 - Struthers' Ligament (near the elbow): The ulnar nerve can also be compressed
as it passes under the Struthers' ligament in the upper arm. This can lead to symptoms similar to
Cubital Tunnel Syndrome.


o Entrapment Point 4 - Between the humeral and ulnar heads of the Flexor Carpi Ulnaris (forearm):
Compression at this point can lead to numbness and tingling in the ring and little fingers, weakness
in the hand, and can potentially lead to a condition known as 'claw hand.'
o Common Injury 1 - Fracture (elbow): A fracture or dislocation of the elbow can potentially damage
the ulnar nerve. This could lead to weakness in the hand, sensory loss in the ring and little fingers,
and difficulty with finger coordination.
o Common Injury 2 - Deep Cuts (wrist): Deep cuts or wounds at the wrist can damage the ulnar nerve.
This could result in sensory and motor loss in the areas innervated by the ulnar nerve, affecting the
ring and little fingers and leading to a condition known as 'claw hand.'
o Common Injury 3 - Prolonged Pressure (elbow): Prolonged pressure on the elbow, such as leaning
on it for long periods, can injure the ulnar nerve over time. This can lead to numbness and tingling in
the ring and little fingers, weakness in the hand, and difficulty with fine movements.
Axillary Nerve
o Entrapment Point 1 - Quadrangular Space (posterior shoulder): The axillary nerve passes through the
quadrangular space, bounded by the teres minor, teres major, long head of the triceps brachii, and the
humerus. Compression or entrapment in this area can lead to shoulder instability, weakness in
shoulder abduction and external rotation, and sensory loss over the regimental badge area (the upper,
outer part of the arm).
o Common Injury 1 - Anterior Shoulder Dislocation: This is one of the most common causes of
axillary nerve injury. It can result in weakness of the deltoid and teres minor muscles, leading to
difficulty with shoulder abduction and external rotation. Sensory loss may occur over the regimental
badge area.
o Common Injury 2 - Fracture of the Humeral Neck: A fracture at this location can lead to damage of
the axillary nerve. This can result in weakness or paralysis of the deltoid and teres minor muscles,
leading to difficulties with shoulder abduction and external rotation. Sensory loss over the
regimental badge area may also occur.
o Common Injury 3 - Iatrogenic Injury: This refers to an injury that occurs as a result of medical
procedures or treatments, such as surgery or injections in the shoulder area. This could lead to
sensory and motor deficits similar to those described above.
o Please note, the axillary nerve is not commonly entrapped in comparison to other peripheral nerves,
and these scenarios represent potential but relatively rare occurrences.
Radial Nerve
o Entrapment Point 1 - Radial Tunnel (elbow/forearm): The radial tunnel is an anatomical space in the
elbow and upper forearm area. It starts just below the lateral epicondyle of the humerus and extends
down the forearm. The tunnel is bordered by muscles including the brachialis, brachioradialis,
supinator, and extensor carpi radialis brevis. Entrapment of the radial nerve in this tunnel, known as
Radial Tunnel Syndrome, primarily results in pain in the forearm and the back of the hand,
especially when straightening the wrist and fingers. It typically does not cause significant sensory or
motor loss, as the portion of the nerve involved at this point is mainly carrying motor fibers.
o Entrapment Point 2 - Arcade of Frohse (elbow): This point of entrapment affects the deep branch of
the radial nerve, specifically as it passes through the fibrous arch (Arcade of Frohse) within the
supinator muscle. This can lead to a specific type of Radial Tunnel Syndrome known as Posterior
Interosseous Nerve Syndrome (PINS). Entrapment here can result in motor deficits, including
weakness in the extensor carpi radialis brevis and other muscles involved in extending the wrist and
fingers, but typically there's no sensory loss since the deep branch of the radial nerve is primarily a
motor nerve.
o Entrapment Point 3 - Spiral Groove (upper arm): This is a common site for compression, especially
with fractures of the humerus or prolonged immobilization of the upper arm. Symptoms can include
weakness or paralysis of the extensor muscles of the forearm, wrist, and fingers, as well as decreased
sensation in the back of the hand and forearm.
o Common Injury 1 - Humeral Shaft Fracture: A fracture of the humerus can injure the radial nerve as
it winds around the bone in the spiral groove. This can lead to 'wrist drop' - inability to extend the
wrist and fingers, and potential sensory loss in the back of the hand and forearm.
o Common Injury 2 - Crutch Palsy: Prolonged pressure on the upper arm from using crutches can
compress the radial nerve in the spiral groove. This can lead to wrist drop, and numbness or tingling
in the back of the hand and forearm.
o Common Injury 3 - Saturday Night Palsy: This refers to an injury that occurs when the arm is draped
over a hard object, compressing the radial nerve in the spiral groove. It can lead to wrist drop, and
numbness or tingling in the back of the hand and forearm.
Things to Note:
The Struthers' ligament
The Struthers' ligament is also known as the supracondylar process ligament. The Struthers' ligament is a
relatively rare anatomical variant found in the upper arm, specifically in the region of the distal anterior
humerus. It stretches from the supracondylar process (a small, hook-like bony spur that is present in about 1%
of the population) to the medial epicondyle of the humerus. This formation creates a canal through which the
median nerve and brachial artery may pass.
Please note that the presence of a Struthers' ligament and supracondylar process can sometimes lead to
nerve or vascular compression syndromes, though these are quite rare. The ulnar nerve does not typically pass
under the Struthers' ligament, but rather in the cubital tunnel at the elbow, under the retinaculum of Osborne,
between the two heads of the flexor carpi ulnaris muscle.
Radial tunnel
The entrapment of the radial nerve within the radial tunnel can indeed lead to motor symptoms given
that this portion of the nerve primarily carries motor fibers. However, it's important to note that these symptoms
are often subtle and can be overshadowed by the predominant symptom of pain.
The radial tunnel is a narrow space that begins at the level of the elbow and extends into the forearm. It
contains the radial nerve which splits into a superficial branch (sensory) and a deep branch (motor - also known
as the posterior interosseous nerve) at the level of the radial tunnel.
Entrapment within the radial tunnel can potentially affect both the deep and superficial branches of the
radial nerve. However, it often occurs before the deep branch has given off all of its muscular branches,
meaning some muscles may still function normally. In addition, the deep branch of the radial nerve primarily
innervates the extensor muscles in the forearm that control wrist and finger extension. These muscles have some
functional redundancy due to multiple muscles contributing to the same movements, so weakness may not be as
noticeable.
That being said, if the entrapment is severe or prolonged, it can lead to noticeable motor dysfunction,
including weakness of the extensor muscles in the forearm, difficulty in extending the wrist and fingers, and in
some cases, a condition known as "wrist drop". The primary symptom, however, is often pain in the forearm
and back of the hand, particularly with extension of the wrist and fingers. This pain can sometimes be
misdiagnosed as lateral epicondylitis or "tennis elbow".
LOWER EXTREMITY NERVE ENTRAPMENTS AND INJURIES

Obturator Nerve
o Entrapment Point 1 - Obturator Canal: Compression within the obturator canal can lead to Obturator
Neuropathy, which can cause weakness in adduction of the thigh, and sensory loss over the medial
aspect of the thigh.
o Common Injury 1 - Pelvic Surgery: Iatrogenic injury during pelvic surgeries can lead to damage to
the obturator nerve, causing weakness in adduction of the thigh, and sensory loss over the medial
aspect of the thigh.
o Common Injury 2 - Pelvic Fractures: Fractures or trauma to the pelvis can potentially injure the
obturator nerve, resulting in similar deficits to those described above.

Sciatic Nerve
o Entrapment Point 1 - Piriformis Muscle (Hip): When the sciatic nerve is compressed by the
piriformis muscle in the hip, it can lead to Piriformis Syndrome. This can cause pain, numbness, and
tingling in the buttock and down the leg, and sometimes foot.
o Common Injury 1 - Hip Dislocation or Fracture: These injuries can potentially damage the sciatic
nerve, leading to weakness in many of the muscles in the leg, and sensory loss in the posterior and
lateral aspects of the leg and foot.
o Common Injury 2 - Iatrogenic Injury: Injuries from injections into the buttock or surgeries in the hip
area can potentially damage the sciatic nerve, leading to similar deficits as those described above.

Tibial/Posterior Tibial Nerve
o Entrapment Point 1 - Tarsal Tunnel (Ankle): Compression of the tibial nerve within the tarsal tunnel,
an anatomical structure located on the medial of the ankle, (formed by the bony prominence of the
medial malleolus of the tibia and the flexor retinaculum) can lead to Tarsal Tunnel Syndrome. This
can cause pain, numbness, and tingling in the foot and toes.
o Common Injury 1 - Ankle Sprain or Fracture: These injuries can potentially damage the tibial nerve,
leading to weakness in the muscles that move the foot and toes, and sensory loss in the sole of the
foot.
o Common Injury 2 - Iatrogenic Injury: Injuries from surgeries or injections in the ankle area can
potentially damage the tibial nerve, leading to similar deficits as those described above.

Plantar Nerves and Calcaneal Nerves
o Entrapment Point 1 - Abductor Hallucis Muscle: Compression of the medial plantar nerve within the
abductor hallucis muscle can cause Jogger's Foot. This can result in pain, numbness, and tingling in
the area of the big toe??? and the adjacent part of the foot. Overpronation is usually a contributing
factor to this scenario due to the increased tension that it puts on the nerves.
o Common Injury 1 - Prolonged Pressure or Trauma: Activities that put prolonged pressure on the foot
or sudden trauma can potentially damage the plantar nerves, leading to pain, numbness, and tingling
in various parts of the sole of the foot.

Common Fibular (Peroneal) Nerve
o Entrapment Point 1 - Fibular Head (Knee): Compression or entrapment of the common fibular nerve
at this location can lead to Foot Drop. Symptoms include weakness in foot and toe dorsiflexion and
foot eversion, as well as sensory loss over the lateral aspect of the leg and the dorsum of the foot.
o Entrapment Point 2 - Neck of the Fibula: The nerve can also be compressed at the neck of the fibula,
causing similar effects to those of entrapment at the fibular head.
o Common Injury 1 - Leg Trauma or Fracture: Direct trauma or fracture in the fibular head region can
potentially damage the common fibular nerve, leading to similar deficits as described above.
o Common Injury 2 - Prolonged Compression: Prolonged compression, such as due to habitual leg
crossing or wearing tight boots, can potentially damage the common fibular nerve, resulting in
similar deficits. Acutely, this can result in the sensation of your foot falling asleep.

Superficial Fibular (Peroneal) Nerve
o Entrapment Point 1 - Crural Fascia (Lower Leg): Entrapment here can cause pain, numbness, and
tingling along the lateral lower leg and the dorsum of the foot, except for the area between the first
and second toes.
o Entrapment Point 2 - Fibularis Longus Muscle: The superficial fibular nerve can be entrapped where
it penetrates the deep fascia of the leg through an opening in the fibularis longus muscle. This can
lead to pain, numbness, and tingling along the lateral lower leg and the dorsum of the foot, except
for the area between the first and second toes.
o Common Injury 1 - Leg Trauma: Direct trauma in the lateral lower leg can potentially damage the
superficial fibular nerve, leading to sensory deficits as described above.
o Common Injury 2 - Ankle Sprain: Severe ankle sprains can potentially stretch or tear the superficial
fibular nerve, leading to similar sensory deficits.

Deep Fibular (Peroneal) Nerve
o Entrapment Point 1 - Anterior Tarsal Tunnel (Foot): Compression of the deep fibular nerve in the
anterior tarsal tunnel can lead to Anterior Tarsal Tunnel Syndrome. Symptoms include pain,
numbness, and tingling in the area between the first and second toes, as well as weakness in toe
dorsiflexion.
o Entrapment Point 2 - Extensor Retinaculum: The deep fibular nerve can also be entrapped under the
extensor retinaculum at the ankle, leading to similar effects to those of compression in the anterior
tarsal tunnel.
o Common Injury 1 - Ankle Sprain or Fracture: These injuries can potentially damage the deep fibular
nerve, leading to similar deficits as described above. More proximal injuries can affect the ability to
evert, resulting in increased inversion that may result in equinovarus (clubfoot) in some individuals.
o Common Injury 2 - Iatrogenic Injury: Injuries from surgeries or injections in the foot can potentially
damage the deep fibular nerve, leading to similar deficits.
How over pronation may contribute to Tarsal Tunnel syndrome:
Flat Feet and Stretching of the Tibial Nerve: Flat feet are a common cause of overpronation. The arch of
the foot normally helps absorb shock. When the arch is collapsed, the tibial nerve (running through the tarsal
tunnel) may be stretched or compressed, contributing to tarsal tunnel syndrome.
Excessive Forces on the Medial Side of the Foot: Overpronation often leads to more weight and force
being transmitted through the medial (inner) side of the foot. This can cause inflammation or swelling of
structures within the tarsal tunnel, potentially leading to nerve compression.