Radial nerve

Peripheral nerves series

As I began clinical practice, I realized how often neural symptoms accompany orthopedic injuries. More often than not, these post-op or post-injury numbness/burning/tingling/radiating symptoms are not accompanied with true motor neuropathy. I just finished up a really great Con Ed course by Alison Taylor, OTR/L, CHT, CKTI, NDTc that gave me a few techniques on how to treat sensory nerve entrapments, as well as how to recognize peripheral nerve symptoms that I had not previously recognized as neural issues.

While sensory nerve disruptions usually get better with time after an injury, there are some cases that never completely resolve. But even in the routine post-op patient, if we can decrease the sensory nerve sensitivity, we can decrease pain and get people moving better and sooner.

I went back into my study materials from when I took the PT boards to get my basic neural pathways review:

I didn't include the full picture of the posterior cutaneous nerve of the arm and forearm-- based on the handwritten addition I probably forgot about that branch in my initial drawing. I completely left out the inferior lateral cutaneous nerve of the forearm! So I should probably re-draw this pathway but for now it is the best that I have.

When a nerve is involved, one of my first special tests and one of my first pieces of patient education relates to the position of neural tension. The picture below demonstrates the position of max tension for the radial nerve, although I find that when the shoulder is depressed, neural symptoms will light up with a much smaller arc of abduction.

When relevant, I teach patients nerve glides during my initial evaluation, with instructions to keep slides in a completely asymptomatic arc. The goal is to create movement rather than tension. With wrist and elbow movement alone, a 2005 study estimated that the radial nerve must move approximately 14.2 mm through the surrounding tissue. (add source from JOSPT) Something else that has worked really well for me is also teaching patients the converse-- the position that slackens the nerve maximally. While it is important to make sure the patient doesn't adopt this position permanently, this can be an important tool for quick symptom relief when it is a true neural tension issue.

Besides nerve length, a new way of looking at neural tension from the course this weekend was understanding the influence of "corners" on the nerve. The potential corners Alison includes in her discussion of the radial nerve include the neck, humeral head, lateral epicondyle, radial head*, distal radius, base of thumb CMC*, and radial collateral ligaments* of 2nd digit MP and IP. Of note, the radial nerve runs by more bony prominences than the other upper extremity peripheral nerves do. Injuries at these sites should be screened for radial nerve symptoms-- and conversely these sites may be worth investigating (see exam below) when a patient tests positive for radial neural tension. Notable in the list, and often overlooked as a potential neural issue, includes the lateral epicondyle as it relates to a common referral to physical therapy: lateral elbow pain ADD ALISON'S ARTICLE HERE 2021 JHT. The sites with an asterisk (*) are regions that Alison Taylor advises are frequent offenders when the radial nerve is involved.

Sites of muscular compression should also be considered, including the supinator, triceps, extensor pollicis longus, and brachioradialis (p. 72). The axilla can be grouped in here as well, as a potential site of compression-- most notably discussed in cases of external pressure such as from a crutch or back of a chair, sometimes called "Saturday night palsy."

Motor neuropathies can be screened in/out more easily with EMG, and with some accuracy with simple MMT at advantaged stages. Most of us graduate PT school with a fair understanding of motor nerve screening, so for the purposes of this series, I will focus on the evaluation and treatment of sensory branch pathologies.

While some anatomical variations exist, the below picture illustrates the traditional distribution of symptoms when the sensory branches of the radial nerve are involved.

Alison Taylor also had compiled a list of patterns she had observed over her 30-year career working with the upper extremity, that she advised may be a sign to evaluate the peripheral nerves further. The symptoms she listed include shaking the hand to relieve symptoms, body compensations to relieve tension (such as bending the elbow, leaning the head towards the affected arm), white and shiny OR red and irritated skin, and tremors as the patient pushes towards end-range.

My boards study picture above does show the approximate exit points of these sensory branches: the posterior cutaneous branch of the arm and forearm exits , and the superficial branch of the radial nerve exits above the radial head.

The methodology for screening that we learned this weekend involved evaluating different layers at the suspected site including skin, fascia, muscle, and joint. This order is slightly different than my traditional PT examination, during which I will typically assess the muscles and movement patterns first. However, I can see the rationale if a sensory nerve pathology is suspected, or if pain increases before we can get to a true muscle/joint assessment.

The below examination and treatment approach is adapted from Alison Taylor's techniques as taught in "Treating without Pain: Improving Outcomes for Common Conditions of the Upper Extremity."

All of the below treatment utilize the orthopedic best practice of testing and re-testing the patient's concordant sign. The concordant sign is the patient's familiar symptom report, often tested in a provocative position or action. It should be tested before and after any intervention to determine if the intervention is achieving its desired function (whether that be pain-control, ROM, fluidity of movement, etc.)

The skin and fascia: cutaneous and subcutaneous tissue layers

• Anatomy: The skin consists of the dermis and epidermis, which move together (separation of these layers would be a blister). Little ligaments called the retinaculum cutis superficialis, attach the skin to the superficial fascia that lies below. These ligaments also forms a latticework that supports the layer of fat cells between the skin and fascia. Another layer of fat lies below this superficial fascia, suspended in the retinaculum cutis profundum which connects the superficial fascia to the deep fascia. The retinaculum cutis profundum are obliquely oriented, which allow increased mobility between the skin and the deep fascia.

• Clinical significance: Both superficial nerves and receptors, as well as post-operative generalized edema are located in these layers! The dermis is also the site of visible bruising.

• Examination: With gentle pressure, the skin should glide in all directions with varying amount of give (I like to compare affected side to unaffected side in these assessments). The most common causes of decreased skin mobility I see in an orthopedic setting are scars/stitches, swelling, and immobilization. Even when the swelling decreases, the incisions heal, and the immobilizer is removed, decreased skin mobility can persist. The weekend course reminded me not to overlook old scars, because, unless actively targeted, these tissues may have remained chronically "adherent" for years. Alison demonstrates trialing skin glides during the patient's concordant sign in order to assess if a treatment targeting superficial structures may affect pain or movement.

• Treatment: Interventions targeting the mobility of the cutaneous and subcutaneous tissue layers include decompression and skin recoil taping strategies such as those by Kinesiotape, IASTM scraping tools, manual scar massage, retrograde massage, and many other manual techniques.

• For the radial nerve, areas where it runs most superficially and may benefit from the above-listed techniques include the radial head, distal radius, base of thumb CMC, and radial collateral ligaments of 2nd digit MP and IP. Decreased superficial tissue mobility at any of the sites could be contributing to decreased available length of the radial nerve, which could lead to increased nerve sensitivity.

The muscle

• Anatomy: supinator, triceps, extensor pollicis longus, and brachioradialis

• Clinical significance:

  • Adhesions at the extensor pollicis longus in the forearm present with worsening radial nerve symptoms as the thumb moves into radial abduction, such as with a wide grip

• Examination:

• Treatment:

The joint

• Anatomy: the superficial branch of the radial nerve (SBRN) runs across the anterior radial head. The biceps exert an anterior pull on the radial head, and the dynamic stabilizers that oppose this pull include the supinator, anconeus, and triceps (via radioulnar joint influence).

• Clinical significance: with repetitive or heavy lifting, a strong contraction of the bicep may translate the radial head anteriorly into a position of increased pressure on the radial nerve (as well as possibly exerting pressure on the ECRB and ECRL)

• Examination: If pain during the concordant sign decreases with either posterior radial head mobilization with movement OR manual pressure over the distal biceps; consider that anterior translation of the radial head may be contributing to SBRN irritation

• Treatment: a patient may benefit from posterior radial head mobs and high tension taping/ McConnell taping to maintain this position. After joint mobs, neuromuscular re-education is recommended to facilitate maintenance of the new position, which can include isometric elbow extension and supination through the range before progressing to isotonic training. ** the biceps long head is an accessory supinator, so be sure to cue supination from forearm and palpate to ensure biceps are not active.** Alison also recommends kinesiotaping for biceps inhibition/ triceps facilitation.

• Does she approximate ulna for radial nerve also?

p71- 73 of shoulder slides

tennis elbow assessment