Nerve injury in sports is not very frequent. According to the report of the Japanese Athletic Association in 1971, peripheral nerve injuries accounted for only 0.3% of sports injuries. Among all peripheral nerve injuries treated in their centre within 18 years, 5.7% were related to sports. The nerves most frequently involved were brachial plexus, radial nerve and ulnar, peroneal and axillary nerves in order of frequency [1]. The common mechanisms of injury were compression, traction, ischaemia and laceration [2].

A recent paper published in 2017 reported that sports-related nerve injuries accounted for around 0.5% of all traumatic peripheral nerve injuries [3]. Better understanding of sports biomechanics and preventive measures during sports could effectively reduce the number of injuries.

Nerve injury in sports could be classified into acute or chronic.

Acute injuries included:

  • Blunt trauma

  • Sharp injury

  • Fracture ends laceration

  • Acute traction

Chronic injuries were commonly caused by irritation or compression due to repetitive stress. For example:

  • Muscle hypertrophy, fascial edge or increased compartment pressure causing compression

  • Chronic inflammatory tissue causing compression

  • Poor flexibility causing excessive traction at relative fixed point

  • Subluxation with frictional injury

The underlying pathology of chronic nerve injury was usually due to ischaemia. When the critical threshold of 40–50 mmHg compression force was reached, inflammatory response and scar tissue formation would initiate. The sequel would be neurapraxia or axonotmesis types of nerve injury.

18.1 A List of Common Sports-Related Nerve Injuries of Upper Limb

Nerves affected

Possible related sports

Brachial plexus

Rugby, football, wrestling

Spinal accessory nerve

Hockey

Suprascapular nerve

Weightlifting, volleyball, racquet sports

Long thoracic nerve

Ball games with overhead positioning of upper limb

Axillary nerve

Baseball

Musculocutaneous nerve

Body building, basketball

Ulnar nerve at elbow

Throwing sports, volleyball, weightlifting, racquet sports

Low ulnar nerve

Cycling, volleyball

Anterior interosseous nerve of median nerve

Long flexors hypertrophy

Low median nerve

Sports requires lots of wrist motion

Radial nerve at arm level

Direct contusion of humerus

Superficial sensory branch of radial nerve

Handcuff

Posterior interosseous nerve of radial nerve

• Proximal at radial tunnel (radial tunnel syndrome)

• Distal at forearm extensor compartment (PIN compression syndrome)

• Swimming, tennis, powerlifting (repeated forceful pronation and supination)

• Windsurfing (prolonged repeated strong wrist dorsiflexion)

Digital nerve

Bowling

18.2 Brachial Plexus

Brachial plexus injury could occur in rugby, football or wrestler. In a study of Canadian football, brachial plexus injuries were reported to be 26% of players during the 2010 football season [4]. In an American football study, the lifetime rate of brachial plexus injuries was 50.3% [5].

The following three mechanisms were common to brachial plexus injury [6,7,8,9,10,11]:

  1. (a)

    Traction caused by lateral flexion of the neck away from the involved side (similar to the mechanism in birth trauma)

  2. (b)

    Direct impact to the Erb point causing compression to the brachial plexus (often associated with poor-fitting shoulder pads)

  3. (c)

    Nerve compression caused by neck hyperextension and ipsilateral rotation (The neural foramen narrows in this mechanism.)

‘Cervical nerve pinch syndrome’, ‘burner’, ‘stinger’ or ‘pinched nerve’ were some popular terms to describe the injuries. Symptoms included burning or electric shock sensation over the arm. There might be arm numbness and weakness immediately following the injury.

Athletes were recommended to stop their sports activity until their symptoms were completely gone. This could avoid further injury. In case of recurrent symptoms, a special neck roll or elevated shoulder pads could be used during sports activities.

18.3 Spinal Accessory Nerve

Spinal accessory nerve was the eleventh cranial nerve. Common injury mechanism was blunt trauma or traction injury, such as lacrosse stick hitting across the posterior neck during hockey game, traction injury from a fall onto the shoulder.

Patient could experience shoulder pain, weakness in forward elevation and abduction of the shoulder. It might be associated with rotary winging of the scapula, in which drooping of the entire shoulder girdle with lateral displacement of the scapula could be seen.

18.4 Suprascapular Nerve

Sports requiring repeated shoulder abduction and external rotation could injure suprascapular nerve easily. Players in volleyball, weightlifting, racquet sports and basketball and free stroke swimmers were vulnerable. Mechanism was usually traction with excessive excursion.

Interestingly, studies reported that 10–30% of elite volleyball athletes had signs of suprascapular neuropathy. This observation lent credence to the term ‘volleyball shoulder’ [12, 13].

Traction injury and entrapment were common mode of injury. Limited excursion of the suprascapular nerve, less than 3 cm, was a risk factor for traction injury. Suprascapular nerve entered the infraspinatus fossa through the spinoglenoid notch, which was a potential compression site [14, 15]. Congenital narrow notch, a bifid transverse scapular ligament, calcified transverse ligament, and fractures predisposed to entrapment.

Patient with suprascapular nerve injury might complain of poorly localized pain at posterolateral portion of the shoulder. Atrophy of supraspinatus and infraspinatus can be seen. There may be insidious onset of shoulder weakness, especially abduction and external rotation. Injuries occurring at the spinoglenoid notch could result in isolated infraspinatus muscle atrophy and are pain-free. The condition could mimic rotator cuff tear.

Notch view x-ray, electromyogram (EMG) and magnetic resonance imaging (MRI) could be used as diagnostic tool. Imaging could also identify muscle atrophy and rule out other causes of external compression, e.g. ganglion.

Conservative treatment options included resting, activity modification, non-steroidal anti-inflammatory drugs (NSAIDs) and steroid injection. Rehabilitation exercise was also useful, e.g. rotator cuff strengthening, peri-scapular stretching and strengthening, scapular depression and retraction training. Surgical release of transverse scapular ligament was reserved when the above fails.

18.5 Long Thoracic Nerve

Typical injury mechanism of long thoracic nerve was stretching or traction upper limb in an overhead position, especially when the neck was turned to the contralateral side. Winging of scapula was the clinical sign.

Nonoperative management was the mainstay of treatment and included rest, symptomatic relief and therapy to maintain shoulder range of motion and strength and stability. The athlete should avoid heavy lifting or participating in activities that put the nerve at risk. Most cases subsided within 6–9 months, and almost all resolve satisfactorily within 12 months. Surgery was indicated only after 1–2 years of failed conservative management and no improvement in nerve function documented by electromyography (EMG) testing [16].

18.6 Axillary Nerve

Axillary nerve injury could occur in baseball pitcher. It was also called ‘quadrilateral space syndrome’. The cause of axillary nerve irritation could be due to traction or osteophytes formation at posterior-inferior glenoid. Patient might present with vague posterior-superior shoulder pain. There might be deltoid weakness with extension lag sign. Electromyography (EMG) and magnetic resonance imaging (MRI) could help to make the diagnosis.

Patients should undergo an extensive rehabilitation training, involving scapular depression and retraction exercise to maintain normal scapulo-humeral pattern. Shoulder joint contracture should be avoided at all costs as a loss of shoulder mobility might ultimately affect functional outcome despite a return of axillary nerve function. If no axillary nerve recovery was observed by 3–4 months following injury, surgical exploration was indicated [17].

18.7 Musculocutaneous Nerve

Isolated musculocutaneous neuropathy was rare. Patients with non-traumatic musculocutaneous neuropathies have been reported due to strenuous physical activity causing vigorous biceps hypertrophy, e.g. body builder, slam-dunker in basketball, athletes in weightlifting or rowing, throwers, etc. [18]. Sensory branch of musculocutaneous nerve was compressed during elbow extension and forearm pronation, as the lateral edge of the biceps aponeurosis impinged on it.

Patient might complain of burning or dysaesthetic pain in the forearm. There might be lateral bicep tenderness. Nerve conduction studies could find absent antebrachial cutaneous response.

Local lignocaine and steroid injection test could be both diagnostic and therapeutic. Operation might be needed for removal of a wedge of biceps aponeurosis at the nerve compression site.

18.8 Ulnar Nerve at Elbow

Ulnar nerve neuropathy was the most commonly injured nerve in sports. It was highly susceptible to injury during overhead athletic activity and particularly vulnerable in throwing athletes. The combination of valgus forces and rapid extension resulted in tensile forces along the medial side and compression on the lateral portion of the elbow as well as shear forces in the posterior compartment. This combination was referred to as valgus extension overload syndrome and was the basic pathological model for most sports-related elbow injuries [19].

The ulnar nerve could be injured acutely via a direct blow to the back of the elbow during contact sports. Nevertheless, ulnar nerve injury more commonly results from traction or compressive forces at the elbow due to repetitive overuse during overhead athletic activity. Ulnar nerve dysfunction could be caused by excessive elbow valgus forces, especially in baseball pitchers, compression at the cubital tunnel associated with repetitive stress or spur formation in the ulnar groove with subsequent nerve compression [20, 21]. Patients with subluxation of ulnar nerve were prone to injury by friction.

Ulnar nerve passed through arcade of Struthers. It then travelled posterior to medial epicondyle through cubital tunnel underneath the ligament of Osborne. After it exited the tunnel, it passed between two heads of flexor carpi ulnaris. Free gliding of ulnar nerve in cubital tunnel was crucial during elbow flexion and extension. Ulnar nerve elongated an average of 4.7 mm from elbow extension to full flexion [22].

Traction injuries to ulnar nerve could be due to sustained repeated valgus stress at the elbow, together with tension overload during late cocking and acceleration phase of throwing. Pressure in cubital tunnel increased threefold during elbow flexion and wrist extension and up to sixfold during the late cocking phase. Similar biomechanics occurred in volleyball spiking. Ligament of Osborne, the roof of cubital tunnel, stretched 5 mm for every 45′ elbow flexion. Medial head of triceps translated 7 mm medially during elbow flexion; therefore, hypertrophy of the muscle could cause compression to ulnar nerve [23]. Similarly, hypertrophy of flexor carpi ulnaris could be another reason of nerve compression. Space-occupying lesions like scar adhesions, calcium deposits and osteophytes could also lead to nerve compression.

The clinical presentation was similar to cubital tunnel syndrome. Symptoms could be exacerbated by overhead activities or extreme elbow flexion. Diagnosis was confirmed with nerve conduction studies.

Nonoperative treatment aimed at optimization of throwing biomechanics and correction of movement pattern. Options of surgery included open or endoscopic cubital tunnel release, anterior transposition of ulnar nerve and medial epicondylectomy. All options yielded comparable results [24, 25]. Endoscopic cubital tunnel release could hasten rehabilitation time. Anterior transposition of ulnar nerve could effectively deal with traction and subluxation problem of ulnar nerve. In case of medial epicondylectomy, maximally 20% of medial epicondyle could safely be removed without detachment of medial collateral ligament [26]. Otherwise, there might be complication of elbow instability.

18.9 Low Ulnar Nerve

Low ulnar nerve injury was associated with cycling or mountain biking. Chronic external compression over ulnar palm with the wrist in dorsiflexion caused compression at deep terminal branch of ulnar nerve. There was high load over the nerve especially going downhill, while the body weight of athletes was supported by the base of the palm.

Clinical presentation depended on the exact compression site within Guyon’s canal. There might be intrinsic hand muscle wasting. Patient might have motor or sensory deficit or both.

Other possible differential diagnoses included:

  1. 1.

    Ulnar hammer syndrome in judo or karate player (post-traumatic digital ischaemia from thrombosis of ulnar artery at Guyon’s canal)

  2. 2.

    Ulnar nerve compressed by ulnar artery aneurysm (presented with cold intolerance and ulnar finger numbness)

  3. 3.

    Fracture hook of hamate

  4. 4.

    Ganglion cyst in Guyon’s canal

  5. 5.

    Ulnar carpal instability

  6. 6.

    C8, T1 radiculopathy

  7. 7.

    Motor neuron disease

Treatment was usually conservative, which included adaptation and accommodation of sitting position of bikers, proper use of padding and gloves, adjustment of bike handle bar design, etc.

18.10 Anterior Interosseous Nerve of Median Nerve

Anterior interosseous nerve of median nerve palsy was a rare condition. Marked forearm muscle hypertrophy caused effort compression to the nerve. If conservative treatment failed, operation for release of all related fascial bands (flexor digitorum superficialis, pronator teres, accessory bicipital aponeurosis) was indicated.

18.11 Low Median Nerve

Median nerve at carpal tunnel could be affected by sports requiring gripping or prolonged repetitive flexion and extension of the wrist. Clinical presentation was basically the same as carpal tunnel syndrome. Patient might present with exertional paraesthesia in the hand, wrist and forearm. There might be sensory deficit at radial 3.5 digits and thenar muscle weakness. Tinel’s sign and Phalen’s sign could be positive. Nerve conduction studies could be used to confirm diagnosis.

Conservative treatment worked in majority of cases. It included nocturnal splint to keep the wrist in neutral or dorsiflexed position and modification of sports movement. Surgical treatment was indicated if there was no improvement after conservative management. Operation for carpal tunnel release could be done by open or endoscopic method. However, there might be post-operative weakness of forearm flexors due to loss of flexor retinaculum as a pulley [27]. It could be an important concern for athletes.

18.12 Radial Nerve at Arm Level

Injury to radial nerve could cause dropping of wrist and digits. It was associated with sensory deficit over anatomical snuff box. It could be caused by direct contusion of humerus. Majority of the radial nerve injuries in sports were neurapraxia. Anti-wrist drop splint could be used to wait for recovery.

18.13 Superficial Branch of Radial Nerve

Superficial branch of radial nerve at the wrist could be compressed by handcuff, wristbands or taping. The condition could worsen by repetitive ulnar deviation, pronation and supination of the wrist. Patient might complain of vague pain or paraesthesia over dorsoradial aspect of the wrist or thumb. Diagnosis could be confirmed by nerve conduction studies. Treatment included resting splint with the wrist in supination. Surgical release was rarely needed.

18.14 Posterior Interosseous Nerve of Radial Nerve

18.14.1 Radial Tunnel Syndrome

Radial tunnel started from the level of the radiocapitellar joint, extending distally past the proximal edge of the supinator boundaries. It was about 5 cm in length. Sports requiring repeated forceful pronation and supination of the forearm, e.g. swimming, tennis and powerlifting, could lead to radial tunnel syndrome. Patient might complain of pain over lateral elbow distal to lateral epicondyle. It could mimic tennis elbow. Physical examination showed increased pain with resisted middle finger extension with the forearm in pronation and elbow in extension. Conservative treatment was usually effective.

18.14.2 PIN Compression Syndrome

Windsurfing always required prolonged repeated strong wrist dorsiflexion. This could lead to exertional compartment syndrome of the posterior muscle compartment of the forearm. Patient could present with progressive weakness of finger extensors during training. Conservative treatment options included resting, non-steroidal anti-inflammatory drugs (NSAID) and muscle stretching programme. Sometimes, patient might require prophylactic fasciotomy to release the posterior interosseous nerve of radial nerve.

18.15 Digital Nerve Compression

A common example was repeated trauma to ulnar digital nerve of the thumb in bowling players. Compression was caused by scar tissue formed around the nerve. It could be prevented by use of protective padding during the game. Temporary resting splints for the finger were a conservative treatment option. Surgery was rarely needed, e.g. decompression or nerve transfer.

Conclusion

Nerve injuries in sports were frequently caused by overuse. Clinical presentation could be vague at early stage, as symptoms usually occur after exertion. Protective measures (e.g. padding, splint, gear) could help to prevent injuries. Primary and secondary prevention by appropriate training programme and proper execution of movement pattern would always be essential.

For medical management in nerve injuries in sports, conservative treatment frequently worked. Sometimes, surgery like release operation or fasciotomy might be required.