The Impact of Muscular Variation on the Neurodynamic Test for the Median Nerve in a Healthy Population With Langer's Axillary Arch

Effect of cervical contralateral lateral flexion on displacement and strain in the median nerve and flexor digitorum superficialis at the wrist during the ULNT1 - Cadaveric study

INTRODUCTION

A key issue in neurodynamic testing is whether a manoeuvre designed to produce differential biomechanical behaviour (structural differentiation) of nerve compared to adjacent muscle is mechanically accurate. The aim of this study was to investigate the capacity of cervical contralateral lateral flexion to produce differential biomechanical behaviour of the median nerve at the wrist (mechanical specificity) in relation to the adjacent muscle (flexor digitorum superficialis) at different ranges of upper limb neurodynamic test 1 in cadavers.

MATERIAL AND METHODS

A cross-sectional study was carried out. In fresh frozen cadavers, with microstrain devices and Vernier calipers, strain and excursion in the median nerve and flexor digitorum superficialis muscle were measured during cervical contralateral lateral flexion at 0°, 30°, 60° and 90° of elbow flexion of the upper limb neurodynamic test 1.

RESULTS

The cervical movement resulted in proximal excursion and significant changes in strain in the median nerve at 0°, 30° and 60° of elbow flexion during the upper limb neurodynamic test 1 (p < 0.05). In contrast, the structural differentiation manoeuvre did not affect the strain nor the excursion in the muscle at any position of the elbow (p > 0.05).

CONCLUSION

Adding CCLF to each ULNT1 median elbow angle increased strain and created proximal excursion of the median nerve at the wrist. Neck movement produced no changes in strain nor excursion of the flexor digitorum superficialis. This study adds to evidence that, in certain circumstances, neck movement may be used in differentiation of nerve and muscle disorders in the wrist.

The Role of the Axillary Arch Variant in Neurovascular Syndrome of Brachial Plexus Compression

Axillary arch muscles are often found. In their course through this area, they might interfere with regional neurovascular structures. This case report will examine the presence of the axillary arch muscle and its implication in brachial plexus compression. During routine dissection of the left axilla and upper limb, a variant muscle (axillary arch muscle) was identified arising from the distal tendon of the latissimus dorsi and extending laterally to insert onto the deep surface of the tendon of insertion of the deltoid muscle. In adduction of the upper limb, the muscle was lax without compression of any underlying neurovascular structures. However, in abduction, the aberrant band of muscles compressed the proximal branches of the brachial plexus. Clinicians should be aware of this anatomical variant and its clinical significance in neurovascular compression including brachial plexus compression, thoracic outlet syndrome, and hyperabduction syndrome. This literature will review the anatomy of the axillary arch and its clinical correlate regarding signs, symptoms, diagnosis, and treatment in brachial plexus compression.

Prevalence and anatomy of the axillary arch and its implications in surgical practice: A meta-analysis

PURPOSE

The following research aimed to investigate the prevalence and anatomical features of the axillary arch (AA) - a muscular, tendinous or musculotendinous slip arising from the latissimus dorsi and that terminates in various structures around the shoulder girdle. The AA may complicate axillary lymph node biopsy or breast reconstruction surgery and may cause thoracic outlet syndrome.

METHODS

Major electronic databases were thoroughly searched for studies on the AA and its variations. Data regarding the prevalence, morphology, laterality, origin, insertion and innervation of the AA was extracted and included in this meta-analysis. The AQUA tool was used in order to assess potential risk of bias within the included studies.

RESULTS

The AA was reported in 29 studies (10,222 axillas), and its pooled prevalence estimate in this meta-analysis was found to be 5.3% of the axillas: unilaterally (61.6%) and bilaterally (38.4%). It was predominantly muscular (55.1% of the patients with the AA), originated from the latissimus dorsi muscle or tendon (87.3% of the patients with the AA), inserted into the pectoralis major muscle or fascia (35.2% of the patients with the AA), and was most commonly innervated by the thoracodorsal nerve (39.9% of the patients with the AA).

CONCLUSION

The AA is a relatively common variant, hence it should not be neglected. Oncologists and surgeons should consider this variant while diagnosing an unknown palpable mass in the axilla, as the arch might mimic a neoplasm or enlarged lymph nodes.

Effect of glenohumeral forward flexion on upper limb myoelectric activity during simulated mills manipulation; relations to peripheral nerve biomechanics

BACKGROUND

It is generally accepted that muscles may activate via the common nociceptive flexion reflex (NFR) in response to painful stimuli associated with tensile or compressive forces on peripheral nerves. Following the basic assumption that the radial nerve may be stressed around the elbow during the execution of the Mills manipulation, two positions considered to have different mechanical effects on the radial nerve and the brachial plexus were tested in order to i) explore whether muscles are activated in certain patterns with concomitant changes in nerve tension, ii) establish whether muscle responses can be modified with mechanical unloading of the brachial plexus.

METHODS

Muscle responses were quantified bilaterally in eight subjects (N = 16) during Mills Manipulation (MM) pre-manipulative positioning and a Varied position that putatively produces less mechanical tension in the brachial plexus. End range pre-manipulative stretch was used in order to simulate the effects of Mills manipulation. Electromyographic signals were recorded with a 16 channel portable EMG unit and correlated with kinematic data from three charge-coupled device adjustable cameras which allowed for precise movement tracking.

RESULTS

Compared with the Standard Mills manipulation position, the Varied position produced significantly reduced myoelectric activity (P ≤ .001) in all test muscles. Additional subjective data support the notion that certain muscle activity patterns were protective.

CONCLUSION

It seems that protective muscles are selectively activated in a specific pattern in order to protect the radial nerve from mechanical tension by shortening its pathway, suggesting integration of muscle and neural mechanisms. Furthermore, the significantly decreased myoelectric activity with reduced mechanical tension in the brachial plexus may help controlling collateral effects of the Mills manipulation itself, making it potentially safer and more specific.

Common interlimb asymmetries and neurogenic responses during upper limb neurodynamic testing: implications for test interpretation

STUDY DESIGN

Clinical measurement pilot study.

INTRODUCTION

Upper limb neurodynamic testing (ULNT1) uses interlimb comparisons to investigate nerve sensitivity to movement.

PURPOSE OF THE STUDY

To establish the magnitude of range of motion asymmetries between limbs and the frequency of neurogenic sensory responses during ULNT1.

METHODS

Elbow extension range of motion (EE-ROM) and sensory responses were measured during ULNT1 in dominant and nondominant limbs for 40 asymptomatic participants. Structural differentiation was performed to examine if sensory responses were associated with neurogenic sources.

RESULTS

The average intraindividual EE-ROM asymmetry was 7.28 deg (6.68 standard deviation) (95% confidence interval: 5.18, 9.28). Sensory responses in the limbs during ULNT1 were altered by structural differentiation in 95% of participants. An intraindividual, interlimb difference of ≥10 deg exceeds the range of common asymmetry during ULNT1.

CONCLUSIONS

Neurogenic sensory responses are common findings in healthy individuals and should be acknowledged when interpreting ULNT1 findings.

LEVEL OF EVIDENCE

3a.

Effect of cervical spine position on upper limb myoelectric activity during pre-manipulative stretch for Mills manipulation: a new model, relations to peripheral nerve biomechanics and specificity of Mills manipulation

OBJECTIVES

(A) Describe a new method of investigation of the possible muscular effects of the commonly practiced Mills manipulation for lateral elbow pain (epicondylalgia), (B) ascertain if myoelectric activity is influenced during the pre-manipulative stretch for Mills manipulation, (C) establish whether muscle responses are influenced by ipsilateral lateral flexion of the cervical spine which reduces mechanical tension in the peripheral nerves of the upper limb.

SAMPLE

Eight asymptomatic subjects were tested bilaterally (N=16).

METHODS

Myoelectric measurements - EMG signals were recorded with a 16 channel pocket EMG patient unit and processed off-line. Measurement of joint positions-three CCD adjustable cameras sensitive to 10mm reflective passive markers applied at specific locations on the subjects' bodies were used to reconstruct and verify accuracy of body movements and were correlated with EMG recordings.

RESULTS

Compared with the standard (anatomical) position of the cervical spine in which Mills manipulation is typically performed, cervical spine ipsilateral lateral flexion produced significantly reduced activity in muscles that restrain the manipulation movement (elbow extension), namely biceps brachii (P=0.018) and brachioradialis (P=0.000). The affected muscles may therefore produce protective effects during the manipulation.

CONCLUSIONS

Changes in myoelectric activity were in a pattern that suggests that muscle and neural mechanisms may be an integral part of the Mills manipulation. Cervical spine ipsilateral lateral flexion may be used to reduce mechanical stresses in the peripheral nerves and extraneous muscle activity, making Mills' manipulation potentially safer and more specific.

Pain catastrophizing predicts pain intensity during a neurodynamic test for the median nerve in healthy participants

Psychological factors within the Fear-Avoidance Model of Musculoskeletal Pain (FAM) predict clinical and experimental pain in both symptomatic and asymptomatic individuals. Clinicians routinely examine individuals with provocative testing procedures that evoke symptoms. The purpose of this study was to investigate which FAM factors were associated with evoked pain intensity, non-painful symptom intensity, and range of motion during an upper-limb neurodynamic test. Healthy participants (n = 62) completed psychological questionnaires for pain catastrophizing, fear of pain, kinesiophobia, and anxiety prior to neurodynamic testing. Pain intensity, non-painful sensation intensity, and elbow range of motion (ROM) were collected during testing and served as dependent variables in separate simultaneous regression models. All the psychological predictors in the model accounted for 18% of the variance in evoked pain intensity (p = .02), with only pain catastrophizing (beta = .442, p < .01) contributing uniquely to the model. Psychological predictors did not explain significant amounts of variance for the non-painful sensation intensity and ROM models. These findings suggest that pain catastrophizing contributed specifically to evoked pain intensity ratings during neurodynamic testing for healthy subjects. Although these findings cannot be directly translated to clinical practice, the influence of pain catastrophizing on evoked pain responses should be considered during neurodynamic testing.

Effects of upper extremity neural mobilization on thermal pain sensitivity: a sham-controlled study in asymptomatic participants

STUDY DESIGN

A single-blinded, quasi-experimental, within- and between-sessions assessment.

OBJECTIVES

To investigate potential mechanisms of neural mobilization (NM), using tensioning techniques in comparison to sham NM on a group of asymptomatic volunteers between the ages of 18 and 50.

BACKGROUND

NM utilizing tensioning techniques is used by physical therapists in the treatment of patients with cervical and/or upper extremity symptoms. The underlying mechanisms of potential benefits associated with NM tensioning techniques are unknown.

METHODS AND MEASURES

Participants (n = 62) received either a NM or sham NM intervention 2 to 3 times a week for a total of 9 sessions, followed by a 1-week period of no intervention to assess carryover effects. A-delta (first pain response) and C-fiber (temporal summation) mediated pain perceptions were tested via thermal quantitative sensory testing procedures. Elbow extension range of motion (ROM) and sensory descriptor ratings were obtained during a neurodynamic test for the median nerve. Data were analyzed with repeated-measures analysis of variance (ANOVA).

RESULTS

No group differences were seen for A-delta mediated pain perception at either immediate or carryover times. Group differences were identified for immediate C-fiber mediated pain perception (P = .032), in which hypoalgesia occurred for the NM group but not the sham NM group. This hypoalgesic effect was not maintained at carryover (P = .104). Group differences were also identified for the 3-week and carryover periods for elbow extension ROM (P = .004), and for the participant sensory descriptor ratings (P = .018), in which increased ROM and decreased sensory descriptor ratings were identified in participants in the NM group but not the sham NM group.

CONCLUSION

This study provides preliminary evidence that mechanistic effects of tensioning NM differ from sham NM for asymptomatic participants. Specifically, NM resulted in immediate, but not sustained, C-fiber mediated hypoalgesia. Also, NM was associated with increased elbow ROM and a reduction in sensory descriptor ratings at 3-week and carryover assessment times. These differences provide potentially important information on the mechanistic effects of NM, as well as the description of a sham NM for use in future clinical trials.