Diagnosis and treatment of median nerve entrapment at the elbow

by lacertus fibrosus

A. HAMOUYA, G. MEYER ZU RECKENDORF, J-L ROUX

Institut Montpelliérain de la Main

Montpellier, FRANCE

• First description of the Pronator Syndrome: Seyffarth 1951 (1)

• Common sites of Proximal Median Nerve Entrapment (PMNE) at the elbow:

• Ligament of Struthers

• Between the heads of the pronator teres

• The Gantzer’s muscle

• Sublime bridge (tendinous arch connecting the radial and humeral heads of the flexor digitorumsuperficialis muscle)

• Lacertus fibrosus LF (bicipital aponeurisis)

• The first case of PMNE by LF reported in the literature: 1978 (2)

Introduction

1. Seyffarth H. Primary myoses in the M. pronator teres as cause of lesion of the N. medianus (the pronator syndrome). Acta psychiatry Neurol Scand Suppl. 1951;74:251–4.2. Laha RK, Lunsford LD, Dujovny M.Lacertus fibrosus compression of the median nerve. J Neurosurg 1978;48:838-841.

• Lacertus fibrosus is not an anatomicvariation

• LF: Myofascial connection of the biceps brachii muscle to antebrachial fascia

• The myofascia connections create an anatomical continuity between differentmuscles, basis of the chaînes musculaires, sequences ,and myofascialtrains (1).

Biceps Tendon Lacertus

Fibrosus

MedianNerve

Anatomy

1. Steccoa A, Macchib V, Steccoc C, Porzionatob A, Day JA, Delmase V, De Caro R.Anatomical study of myofascial continuity in the anterior region of the upper limb. J of Body work and Mov Ther. 2009; 13:53–62

“This fascial sling seems to be a mechanism of

nature to keep the tendon of biceps angulated

during flexion so that it can work efficiently as a

supinator, while the 2 heads together can bring

about flexion at the elbow joint”.

Forearms dissected

LF present

LF was thickened

LF resting directly on the median nerve

High insertion of the pronator teres

Anatomy

60

55

44

27

17

Diagnosis• PMNE by the LF is a clinical diagnosis (1)

1) Elbow Pain

at the level of the lacertus fibrosus

reproductive by a pressure of the median nerve at this level

2) Muscle Weakness

loss of strength: key pinch,

dropping objects

FPL, FDP II, FCR

3) Scratch Collapse Test (SCT)

1. Elisabet HagertClinical diagnosis and wide-awake surgical treatment of proximal median nerve entrapment at the elbow: a prospective study.Hand. 2013;8:41–46

Surgical technique

Anesthesia

Wide Awake Local Anesthesia Non Tourniquet (WALANT)

Axillary block

Surgical approach

Anterior minimally invasive approach

LFBT

MELE

LFMN

Our series

44 Patients 28 Women Mean Age 43.7 y16 Men Range 24-66 y

46 nerves released 29 Right17 Left

Antecedent 11 Carpal Tunel Syndrome (CTS)02 Epicondylitis01 Wrist arthrodesis01 Forearm compartment syndrome01 De Quervain01 Raynaud

Anesthesia WALANT 14Axillary blocks 32: 29 CTS associated

01 Synovial cyst01 Epicondylitis

Results

41

28

9

4642

0

5

10

15

20

25

30

35

40

45

50Clinical Examination

Paresthesia Tinel MuscleWeakness

SCTPain

After release:

All patients recovered muscle strength

Complications:

01 case: hyperesthesia of the forearm, patient with fibromyalgia

• The motor branches to the forearm muscles are most superficial at the elbow whereas the sensory branches destined for the hand are more centrally located (1,2).

1. Jabaley ME, Wallace WH, Heckler FR.Internal topography of major nerves of the forearm and hand: a current view. J Hand surg am. 1980 jan;5(1):1-18.2. Sunderland S.The intraneural topography of the radial, median and ulnar nerves. Brain. 1945 Dec;68:243-99.

Loss of strenght first!

Scratch Collapse Test

Scratch Collapse Test

• Substance P, a neurotransmitter, is a modulator of nociception which is involved in the signaling of noxious stimuli (2).

• Elevated levels of Substance P has been documented in the carpal tunnel (3).

• The stimuli used with the SCT would not be

considered a noxious stimulus to normal tissue (1).

• The response correlates to the prevalence of

Substance P in the injured area (1).

1. Kahn LC et al.Important Details in Performing and Interpreting the Scratch Collapse Test. Plastic and Reconstructive Surgery:2018 Feb;141(2):399-407.2. DeVane CL. Substance P: a new era, a new role. Pharmacotherapy: The Journal of Human Pharmacology and Drug Therapy. 2001;21(9):1061-9.3. Öztürk N, Erin N, Tüzüner S. Changes in tissue substance P levels in patients with carpal tunnel syndrome. Neurosurgery. 2010;67(6):1655-61.

What Is Substance P?

And Paresthesia…

• 26/28 of patients with paresthesia have CTS confirmed by EMG/NCS

Double Crush Syndrome

• Concept first introduced in 1973 by Upton and McComas (1).

• Constraints to axoplasmic flow from a proximal nerve compression or lesion can make the

distal nerve more prone to compression (2).

1. Upton AM, Mccomas A. The double crush in nerve-entrapment syndromes. The Lancet. 1973;302(7825):359-62.2. Osterman AL. The double crush syndrome. The Orthopedic clinics of North America. 1988;19(1):147-55.

Recommendations…

• Surgical treatment should be provided only in cases where the diagnosis of PMNE has been confirmed by abnormal EDS (1).

But…

• Entrapment at the elbow is less apt to cause abnormalities in conduction (2).

• EMG/NCS in PMNE may simulate CTS (3).

• PMNE can be intermittent, dependent on the position of the elbow and/or the rotational position of the forearm (4).

𝑫𝒚𝒏𝒂𝒎𝒊𝒄 𝑪𝒐𝒎𝒑𝒓𝒆𝒔𝒔𝒊𝒐𝒏 = 𝑫𝒚𝒏𝒂𝒎𝒊𝒄 𝑬𝒙𝒑𝒍𝒐𝒓𝒂𝒕𝒊𝒐𝒏

1. Franklin GM, Glass L, Javaher SP, Kearney RN. Work-related proximal median nerve entrapment (PMNE) diagnosis and treatment. In: Industries WSDoLa, ed. Seattle, Washington 2009:1–11.2. Buchthal F, Rosenfalck A, Trojaborg W. Electrophysiological findings in entrapment of the median nerve at wrist and elbow. J Neurol Neurosurg Psychiatry. 1974;37:340 –360.3. Chang MH, Lee YC, Hsieh PF. The real role of forearm mixed nerve conduction velocity in the assessment of proximal forearm conduction slowing in carpal tunnel syndrome.J Clin Neurophysiol. 2008;25(6):373–7.4. Olehnik WK, Manske PR, Szerzinski J, Louis ST. Median Nerve Compression Proximal Forearm. J Hand Surg Am. 1994;19(1):121-126.

What about Electrodiagnostic?

Take Home Message

Clinical diagnosis

Motor testing in CTS is capital

SCT: new diagnostic tool for nerve entrapments

WALANT: Intraoperative testing/Comfort/Low morbidity