Ultrasonographic evaluation of ulnar nerve morphology in patients with ulnar nerve instability.

INTRODUCTION/AIMS: Ulnar nerve instability (UNI) in the retroepicondylar groove is described as nerve subluxation or dislocation. In this study, considering that instability may cause chronic ulnar nerve damage by increasing the friction risk, we aimed to examine the effects of UNI on nerve morphology ultrasonographically. METHODS: Asymptomatic patients with clinical suspicion of UNI were referred for further clinical and ultrasonographic examination. Based on ulnar nerve mobility on ultrasound, the patients were first divided into two groups: stable and unstable. The unstable group was further divided into two subgroups: subluxation and dislocation. The cross-sectional area (CSA) of the nerve was measured in three regions relative to the medial epicondyle (ME). RESULTS: In the ultrasonographic evaluation, UNI was identified in 59.1% (52) of the 88 elbows. UNI was bilateral in 50% (22) of the 44 patients. Mean CSA was not significantly different between groups. A statistically significant difference in ulnar nerve mobility was found between the group with CSA of <10 versus ≥10 mm2 (p = .027). Nerve instability was found in 85.7% of elbows with an ulnar nerve CSA value of ≥10 mm2 at the ME level. DISCUSSION: The probability of developing neuropathy in patients with UNI may be higher than in those with normal nerve mobility. Further prospective studies are required to elucidate whether asymptomatic individuals with UNI and increased CSA may be at risk for developing symptomatic ulnar neuropathy at the elbow.

Radial nerve compression: anatomical perspective and clinical consequences.

The radial nerve is the biggest branch of the posterior cord of the brachial plexus and one of its five terminal branches. Entrapment of the radial nerve at the elbow is the third most common compressive neuropathy of the upper limb after carpal tunnel and cubital tunnel syndromes. Because the incidence is relatively low and many agents can compress it along its whole course, entrapment of the radial nerve or its branches can pose a considerable clinical challenge. Several of these agents are related to normal or variant anatomy. The most common of the compressive neuropathies related to the radial nerve is the posterior interosseus nerve syndrome. Appropriate treatment requires familiarity with the anatomical traits influencing the presenting symptoms and the related prognoses. The aim of this study is to describe the compressive neuropathies of the radial nerve, emphasizing the anatomical perspective and highlighting the traps awaiting physicians evaluating these entrapments.

Assessment of ulnar nerve stability at the elbow by ultrasonography in children.

BACKGROUND: Elbow fractures are common in children. While Kirschner wire (K-wire) is the most commonly used fixation material in children, medial entry pins may be needed for fracture stability. This study aimed to assess ulnar nerve instability by ultrasonography in children. METHODS: We enrolled 466 children aged 2 months to 14 years between January 2019 and January 2020. There were at least 30 patients in each age group. Ulnar nerves were observed under the ultrasound equipment with the elbow fully extended and flexed. If ulnar nerves were subluxated or dislocated, they were considered to have ulnar nerve instability. The children's clinical data, including sex, age, and elbow sides, were analyzed. RESULTS: Of 466 enrolled children, 59 had ulnar nerve instability. Ulnar nerve instability rate was 12.7% (59/466). Instability was prevalent in children aged 0-2 years (P = .001). Among 59 children with ulnar nerve instability, 52.5% (31/59) had bilateral ulnar nerve instability, 16.9% (10/59) had right ulnar nerve instability, and 30.5% (18/59) had left ulnar nerve instability. Logistic analysis of the risk factors of ulnar nerve instability showed no significant difference in terms of sex and left or right ulnar nerve instability. CONCLUSIONS: Ulnar nerve instability correlated with age in children. Children aged <3 years had a low risk of ulnar nerve instability.

Risk of nerve injury during elbow arthroscopy: ultrasonographic evaluation of preoperative patients.

BACKGROUND: To clarify the real risk of nerve injury during elbow arthroscopy, the distances of the radial and median nerves to the elbow joint were investigated using ultrasonography in patients who underwent surgery. METHODS: A total of 35 patients who underwent arthroscopic surgery of the elbow were investigated. The distances of the nerves to the capsule and bony landmarks were measured using ultrasonography. The radial nerve distances were measured at the capitellum, joint space, radial head, and radial neck levels. The median nerve distances were measured at the trochlear, joint space, and coronoid process levels. The patients were divided into 2 groups: nine patients in the hydrarthrosis (HA) group and 26 patients in the non-hydrarthrosis (non-HA) group. HA was defined as the intra-articular effusion on magnetic resonance imaging scans. RESULTS: The radial nerve ran closer to the capsule at the radial neck level in the HA group than in the non-HA group (2.0 mm vs. 5.9 mm, P < .01). In the non-HA group, the radial nerve ran closer to the radial head than in the HA group (6.3 mm vs. 8.5 mm, P = .01). The median nerve ran closer to the capsule at the trochlear level in the HA group than in the non-HA group (5.2 mm vs. 8.8 mm, P < .01). Nerves at a distance of ≤2 mm from the capsule were found in 7 patients at the radial neck of the radial nerve and in 2 patients at the trochlear region of the median nerve in the HA group. In the non-HA group, they were found in 3 patients at the radial head and in 1 patient at the joint space of the radial nerve. CONCLUSIONS: The dangerous locations for nerve injury during elbow arthroscopy vary according to hydrarthrosis, and this risk should be recognized during arthroscopic surgery.

Correlation between Elbow Flexor Muscle Strength and Needle Electromyography Parameters after Musculocutaneous Nerve Injury.

OBJECTIVES: To explore the changes of elbow flexor muscle strength after musculocutaneous nerve injury and its correlation with needle electromyography (nEMG) parameters. METHODS: Thirty cases of elbow flexor weakness caused by unilateral brachial plexus injury (involving musculocutaneous nerve) were collected. The elbow flexor muscle strength was evaluated by manual muscle test (MMT) based on Lovett Scale. All subjects were divided into Group A (grade 1 and grade 2, 16 cases) and Group B (grade 3 and grade 4, 14 cases) according to their elbow flexor muscle strength of injured side. The biceps brachii of the injured side and the healthy side were examined by nEMG. The latency and amplitude of the compound muscle action potential (CMAP) were recorded. The type of recruitment response, the mean number of turns and the mean amplitude of recruitment potential were recorded when the subjects performed maximal voluntary contraction. The quantitative elbow flexor muscle strength was measured by portable microFET 2 Manual Muscle Tester. The percentage of residual elbow flexor muscle strength (the ratio of quantitative muscle strength of the injured side to the healthy side) was calculated. The differences of nEMG parameters, quantitative muscle strength and residual elbow flexor muscle strength between the two groups and between the injured side and the healthy side were compared. The correlation between elbow flexor manual muscle strength classification, quantitative muscle strength and nEMG parameters was analyzed. RESULTS: After musculocutaneous nerve injury, the percentage of residual elbow flexor muscle strength in Group B was 23.43% and that in Group A was 4.13%. Elbow flexor manual muscle strength classification was significantly correlated with the type of recruitment response, and the correlation coefficient was 0.886 (P<0.05). The quantitative elbow flexor muscle strength was correlated with the latency and amplitude of CMAP, the mean number of turns and the mean amplitude of recruitment potential, and the correlation coefficients were -0.528, 0.588, 0.465 and 0.426 (P<0.05), respectively. CONCLUSIONS: The percentage of residual elbow flexor muscle strength can be used as the basis of muscle strength classification, and the comprehensive application of nEMG parameters can be used to infer quantitative elbow flexor muscle strength.

Mass effect of the distal triceps brachii muscle on ulnar nerve movement during elbow flexion.

INTRODUCTION/AIMS: Hypertrophic triceps brachii contributes to ulnar nerve movement, but the location of the mass effect of the triceps brachii muscle is not known. In this study we aimed to determine the mass effect of the distal medial head of the triceps brachii (DMTB) muscle on ulnar nerve movement. METHODS: In 48 arms, movement of the ulnar nerve at the medial epicondyle and muscle thickness (medial and long head of the triceps brachii [MLTB], medial head of the triceps brachii [MTB], DMTB, and biceps brachii [BB]) were measured using ultrasonography. RESULTS: Ulnar nerve movement at the elbow was consistently correlated with the DMTB muscle thickness (horizontal ulnar nerve movement at the elbow [HM] / vertical ulnar nerve movement at the elbow [VM] with 90° elbow flexion: r = 0.668 / r = 0.313, HM/VM with full elbow flexion: r = 0.481 / r = 0.391). With multiple linear regression, the DMTB was the most important muscle with regard to contribution of thickness to ulnar nerve movement. Individuals with partial and complete dislocation showed a thicker DMTB than those without dislocation. DISCUSSION: Our data suggest that the mass effect of the triceps brachii muscle is exerted primarily by its distal portion. When ulnar nerve dislocation is observed, thickness and anatomical variation of DMTB in the retrocondylar area during elbow flexion should be assessed.

Total Denervation of the Elbow: Cadaveric Feasibility Study.

PURPOSE: Total elbow arthroplasty for the treatment of patients with severe elbow osteoarthritis is associated with postoperative activity limitations and risk of midterm complications. Elbow denervation could be an attractive therapeutic option for young, active patients. The aim of our study was to assess the feasibility of selective total elbow denervation via 2 anteriorly based approaches. METHODS: Selective total elbow denervation was performed in 14 cadaver elbows by 2 fellowship-trained elbow surgeons. Lateral and medial approaches to the elbow were used. The length of skin incisions and the minimum distance between them were noted. The number of articular branches identified and their respective distances from the lateral or medial epicondyle of the humerus were recorded. RESULTS: The anterolateral and anteromedial approaches allowed for the identification of all mixed and sensory nerves in all 14 cases. The mean number of resultant articular branches per cadaver was 1 for the musculocutaneous nerve, 2 (range, 1-3) for the radial nerve, 1 (range, 1-3) for the posterior cutaneous nerve of the forearm, 2 (range, 1-3) for the ulnar nerve, and 2 (range, 1-3) for the medial antebrachial cutaneous nerve; the collateral ulnar nerve was connected directly to the capsule. The length of the medial and lateral incisions was 15 cm (range, 12-18 cm) and 12 cm (range, 10-16 cm), respectively. The mean minimum distance between the incisions was 7.5 cm (range, 6.7-8.5 cm). CONCLUSIONS: The findings suggest that selective elbow denervation via 2 approaches is feasible. CLINICAL RELEVANCE: Selective elbow denervation via 2 approaches is feasible. Surgeons should target the articular branches of the musculocutaneous, radial, ulnar, and collateral ulnar nerves, posterior cutaneous nerve of the forearm, as well as medial antebrachial cutaneous nerves when carrying out this procedure.

Is There an Association Between Ulnar Nerve Hypermobility and Neuropathy at the Elbow?

OBJECTIVE: To systematically review the association between ulnar nerve hypermobility (UNH) at the elbow and ulnar neuropathy (UNE). DATA SOURCES: Cumulative Index to Nursing and Allied Health, MEDLINE, and Embase databases were searched for English language studies published up to July 4, 2020. STUDY SELECTION: We included case-control, cohort, and randomized controlled studies that established the presence or absence of UNH and UNE. Twenty out of 654 studies identified met the inclusion criteria. DATA EXTRACTION: Two reviewers independently extracted data for analysis. Risk of bias and applicability were assessed with the QUADAS-2 tool. DATA SYNTHESIS: We compared rates of UNH between patients diagnosed with and without UNE and found no significant difference. The meta-analysis pooled rate of UNH was 0.37 (95% confidence interval, 0.20-0.57) for those without UNE and 0.33 (95% confidence interval, 0.23-0.45) for those with UNE. CONCLUSIONS: The clinical finding of UNH is unhelpful when assessing for UNE, as the presence of UNH does not make the diagnosis of UNE more likely.

Ulnar nerve subluxation and dislocation: a review of the literature.

The pathogenesis of ulnar nerve subluxation and dislocation is widely debated. Upon elbow flexion, the ulnar nerve slips out of the groove for the ulnar nerve, relocates medial or anterior to the medial epicondyle, and returns to its correct anatomical position upon extension. This chronic condition can cause neuritis or neuropathy; however, it has also been suggested that it protects against neuropathy by reducing tension along the nerve. This article reviews the extant literature with the aim of bringing knowledge of the topic into perspective and standardizing terminology.

The anconeus muscle revisited: double innervation pattern and its clinical implications.

PURPOSE: The aim of the present study is to describe in detail the morphology and innervation pattern of the anconeus muscle, bearing in mind clinical implications such as iatrogenic injuries during surgical elbow approaches. METHODS: A cadaveric study was performed; 56 elbows from 28 formalin-fixed cadavers belonging to the Anatomy Department of Universidad Complutense of Madrid were dissected. The triceps-anconeus nerve was located and dissected. A second innervation to the anconeus muscle from a branch of the posterior interosseous nerve (PIN) was occasionally detected. Taking the lateral epicondyle as a landmark, the entry points of both nerves in the muscle were referenced, the triceps-anconeus nerve was referenced at 0°, 30°, 45°, 70° and 90° of elbow flexion, and the PIN branch at 0°. RESULTS: Anconeus muscle was present in all specimens. The triceps-anconeus nerve was present in all of the dissected elbows. A branch from PIN to the anconeus muscle was present in 38 of the 54 elbows (70.4%). There were statistically significant differences in all measurements regarding the specimens' gender, being higher for men. CONCLUSIONS: There is evidence of a high frequency of a double innervation pattern for the anconeus muscle: the main branch of triceps-anconeus muscle depending on the radial nerve, which is liable to being damaged during posterior elbow approaches, and a secondary branch depending on the PIN. There are very few references to this finding in Anatomical literature and none with such a large sample size.

Fascicular constrictions above elbow typify anterior interosseous nerve syndrome.

INTRODUCTION: In this study we tested the hypothesis that fascicular constrictions (FCs) of the median nerve proximal to the elbow joint characterize anterior interosseous nerve syndrome (AINS). METHODS: Magnetic resonance neurography (MRN) and ultrasound (US) examinations were evaluated in 45 patients with clinically suspected AINS. All 22 patients at site 1 underwent MRN and 8 underwent US; all 23 patients at site 2 underwent US. RESULTS: Median nerve FCs were identified in all MRN cases; FCs and/or fascicular enlargements were identified in 88% of US cases. Most FCs were in the mediannerve posterior/posteromedial region and were proximal to the elbow joint line (mean distance: MRN, 5.4 cm; US, 7.5 cm), with the exception of a single FC (located 1 cm distal). No extrinsic compression of median or anterior interosseous nerves was identified in the arm or forearm. DISCUSSION: AINS is a noncompressive neuropathy characterized by median nerve FCs in the arm.

Validity of computed tomographic measurements and morphological comparison of cubital tunnel in idiopathic cubital tunnel syndrome.

BACKGROUND: Ulnar neuropathy is a common reason for referral to hand surgeons, and 10 to 30% of cubital tunnel syndrome (CuTS) is idiopathic. We hypothesized that the cause of idiopathic CuTS is in the bony structure. METHODS: We analyzed 79 elbows (39 idiopathic CuTS and 40 without CuTS symptom) using computed tomography and Materialize Mimics software to compare the differences between the two groups. We proposed a new bony cubital tunnel with a new boundary that could play a role in ulnar nerve compression symptom. RESULTS: The mean cubital tunnel volume was 1245.6 mm3 in all patients, 1180.6 mm3 in CuTS patients, and 1282.3 mm3 in the control group. A significant difference (p = 0.015) between two groups was found. Bony cubital tunnel cross-sectional area, cubital tunnel depth, and cubital tunnel angle also showed significant differences. CONCLUSION: The shape of the bony cubital tunnel is an important cause of CuTS, and the normal variation of the volume and cross-sectional area of the cubital tunnel and cubital tunnel angle could influence the occurrence of idiopathic CuTS.

Ulnar neuropathy at the elbow in 413 Japanese patients: An assessment of pathological elbow lesions and neurological severity.

BACKGROUND: Various pathological elbow lesions are often complicated with ulnar neuropathy at the elbow (UNE), although the precise pathology, incidence, and clinical and neurological features of these lesions have not been identified. We therefore investigated elbow pathology and neurological severity in Japanese patients with UNE. METHODS: The medical records of 457 Japanese UNE patients who were surgically treated among 6 hospitals were retrospectively examined. Eligible patients had UNE diagnosed by physical findings and nerve conduction studies according to the criteria of the American Association of Electrodiagnostic Medicine. The elbows were analyzed with regard to age, gender, occupation, pathology at the elbow, and severity of nerve palsy. RESULTS: A total of 398 patients with 413 UNE elbows of a mean age of 63 years (range: 15-87) met the inclusion criteria. UNE elbows were predominantly in male patients (69.0%). Overall, 310 elbows (75.1%) had 1 or more elbow lesions: 238 elbows (76.8%) had a single lesion and 72 elbows (23.3%) had 2 or more lesions. The most common lesion was primary elbow osteoarthritis (EOA) occurring in 54.5% of elbows, followed next by medial elbow ganglion in 8.5% and cubitus valgus in 6.5%. Most elbows with medial elbow ganglion or cubitus valgus were associated with EOA. Entrapment sites were at the cubital tunnel in 84.5%-91.3% of UNE elbows, regardless of an association with elbow lesion. The incidence of McGowan grade III lesion was 50.8% in elbows with primary EOA, which was higher than the 35.0% in elbows with no lesion. CONCLUSIONS: This study revealed that UNE had various isolated or combined elbow lesions. In Japanese UNE, primary or secondary EOA was found in 62.2% of cases and severe motor weakness was noted in 47.2%. The incidences of EOA and severe ulnar nerve palsy in the Japanese UNE are higher than those in Caucasians. LEVEL OF EVIDENCE: Level IV; Prognostic-Investigating the effect of a patient characteristic on the outcome of a disease; Case series.

Safe zone for lateral pin placement for external fixation of the distal humerus.

External fixation is a common, efficient technique used for humeral shaft stabilization and elbow fractures. There are reports of radial nerve injuries associated with this procedure. In this study, we investigated the course and variability of the radial nerve along the lateral humerus in relation to the elbow joint to determine a relatively safe zone for lateral pin placement in external fixation. Twenty upper extremities from 10 cadavers were studied. The nerve branches and course of the radial nerve along the lateral humerus were carefully dissected. Straight lines (a, b, and c) were made connecting three landmarks (the acromion, coracoid process, and anterior wall of the axilla) in the proximal upper extremity to the lateral condyle (LC) of the humerus; their intersections with the radial nerve (A, B, and C) were marked. We analyzed whether the intersection positions were correlated with the connecting line lengths. The mean lengths of the connecting lines were (a) 27.24 ± 2.57, (b) 26.18 ± 2.79, and (c) 20.95 ± 1.44 cm; the distance between the intersection points and the LC of the humerus were (Aa) 7.56 ± 1.31, (Bb) 6.90 ± 2.27, and (Cc) 5.01 ± 0.83 cm; and the measured intersection points of the radial nerve in the lateral aspect of the humerus were (A) 18.48%-34.82%, (B) 13.48%-40.00%, and (C) 19.27%-28.05% of the lengths of lines a, b, and c, respectively. Our data provide a more reliable reference to predict the course of the radial nerve on the lateral humerus and define a safe zone for pin placement. Clin. Anat., 33:637-642, 2020. © 2019 Wiley Periodicals, Inc.

Sensory innervation of the human elbow joint and surgical considerations.

Based on the currently available literature, total denervation of the elbow joint is considered impossible. However, consensus with respect to the anatomic location of sensory branches is lacking. The aim of this literature review was to establish consensus with respect to the anatomic features of the articular branches innervating the elbow joint, as well as the distribution of sensory receptors about its capsule. Four electronic databases were queried, between January 1945 and June 2019. Twenty-one original articles providing a detailed description of the distribution of sensory receptors about the elbow joint capsule (5) and its articular branches (16) were reviewed. The posterior capsule was found to be primarily innervated by the ulnar and radial nerves via combined articular branches and sensory branches of the medial antebrachial cutaneous nerve. The anterior capsule was found to be primarily innervated by a plexus of articular ramifications from muscular branches of mixed nerves (ulnar, musculocutaneous, radial, and median nerves). A higher density of nociceptors and mechano-receptors was identified within the posterior and anterior capsules, respectively. Thorough denervation, via the technique proposed herein, is likely to be sufficient in eliminating pain from degenerative conditions of the elbow joint.

Evaluation of the supinator muscle and deep branch of the radial nerve: impact on nerve compression.

PURPOSE: The aim of this study was to investigate the superficial head of supinator muscle (SM) and deep branch of the radial nerve (DBRN) course in SM to see whether the texture characteristics of the superficial head of SM might have a potential compressive effect on the nerve. MATERIALS AND METHODS: Elbow and proximal forearm region of 20 preserved cadavers (n 40, 12 M, 8 F) were dissected in order to measure total and part of DBRN lengths between some reference points. The texture characteristics of both the proximal (where DBRN enters SM) and distal arcade (where DBRN exits SM) of the superficial head of SM were evaluated based on its structure's being muscular, musculotendinous, tendinous, or membranous. RESULTS: The total length of DBRN between sexes without taking side (L/R) into consideration (P = 0.030) and left radiocapitellar joint (RCJ)-arcade of Frohse (AF) length between sexes (P = 0.050) were statistically significant. There was a gradual increase in caliber getting more flattened in every consecutive level which was statistically significant when every two consecutive levels were compared. When compared according to the texture type, there were also significant differences. CONCLUSIONS: Flattening of DBRN in the supinator canal suggests a chronic compression on the nerve. Differences in the texture of the superficial head of the supinator might facilitate this compression. An understanding of the anatomy and nerve topography is of utmost importance in the accurate diagnosis and effective management of peripheral nerve compression.

The effect of paired corticospinal-motoneuronal stimulation on maximal voluntary elbow flexion in cervical spinal cord injury: an experimental study.

STUDY DESIGN: Randomised, controlled, crossover study. OBJECTIVES: Paired corticospinal-motoneuronal stimulation (PCMS) involves repeatedly pairing stimuli to corticospinal neurones and motoneurones to induce changes in corticospinal transmission. Here, we examined whether PCMS could enhance maximal voluntary elbow flexion in people with cervical spinal cord injury. SETTING: Neuroscience Research Australia, Sydney, Australia. METHODS: PCMS comprised 100 pairs of transcranial magnetic and electrical peripheral nerve stimulation (0.1 Hz), timed so corticospinal potentials arrived at corticospinal-motoneuronal synapses 1.5 ms before antidromic motoneuronal potentials. On two separate days, sets of five maximal elbow flexions were performed by 11 individuals with weak elbow flexors post C4 or C5 spinal cord injury before and after PCMS or control (100 peripheral nerve stimuli) conditioning. During contractions, supramaximal biceps brachii stimulation elicited superimposed twitches, which were expressed as a proportion of resting twitches to give maximal voluntary activation. Maximal torque and electromyographic activity were also assessed. RESULTS: Baseline median (range) maximal torque was 11 Nm (6-41 Nm) and voluntary activation was 92% (62-99%). Linear mixed modelling revealed no significant differences between PCMS and control protocols after conditioning (maximal torque: p = 0.87, superimposed twitch: p = 0.87, resting twitch: p = 0.44, voluntary activation: p = 0.36, biceps EMG: p = 0.25, brachioradialis EMG: 0.67). CONCLUSIONS: Possible explanations for the lack of effect include a potential ceiling effect for voluntary activation, or that PCMS may be less effective for elbow flexors than distal muscles. Despite results, previous studies suggest that PCMS is worthy of further investigation.

Safety of Anteromedial Portals in Elbow Arthroscopy: A Systematic Review of Cadaveric Studies.

PURPOSE: To systematically review available literature comparing location and safety of 2 common anteromedial portals with nearby neurovascular structures in cadaveric models and to determine the correct positioning and preparation of the joint before elbow arthroscopy. METHODS: The review was devised in accordance with Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. Inclusion criteria consisted of original, cadaveric studies performed by experienced surgeons on male or female elbows evaluating anteromedial portal placement with regard to proximity of the arthroscope to neurovascular structures. Exclusion criteria consisted of case reports, clinical series, non-English language studies, and noncadaveric studies. Statistical analysis was done to measure reviewer reliability after scoring of each study. RESULTS: During screening, 2,596 studies were identified, and 10 studies met final inclusion as original, cadaveric investigations of anteromedial portal proximity to neurovascular structures. The difference in distance between proximal and distal portals was <1 mm for the brachial artery and <1.5 mm for the medial antebrachial cutaneous nerve, whereas the ulnar nerve was 4.17 mm further from the distal portal and the median nerve was 5.07 mm further from the proximal portal. Joint distension increased the distances of neurovascular structures to portal sites, with the exception of the ulnar nerve in distal portals. Elbow flexion to 90° increased distances of all neurovascular structures to portal sites. CONCLUSION: The results show that the proximal anteromedial portal puts fewer structures at risk compared with the distal portal. Elbows in 90° flexion with joint distension carry a lower risk for neurovascular injury during portal placement. These findings suggest the proximal anteromedial portal to be the safer technique in anteromedial arthroscopy of the elbow. CLINICAL RELEVANCE: Discrepancies in placement of portals have existed in the literature, indicating differing safety margins regarding surrounding neurovascular anatomy. The present study aims to link together the literature-based evidence to describe the safest anteromedial portal variation.

The change in position of the axillary nerve with rotation of the arm.

The axillary nerve is the most commonly injured nerve around the arm. In the deltopectoral approach, classical teaching states that lateral rotation of the humerus increases the distance between the subscapularis and the axillary nerve. This is the first anatomical study to quantify the distance change between the axillary nerve and subscapularis produced by arm rotation. Eight arms were placed in the supine position and a classical deltopectoral approach was performed. With digital calipers, measurements were made from the closest identifiable margin of the nerve to the inferior extent of the tenotomy. All measurements were made with the arm in 0° abduction and elbow in 90° of flexion, and repeated with the arm in 45° of medial rotation, 0° lateral rotation and 45° of lateral rotation. The mean d Axillary Nerve to subscapularis was recorded as 30.9 mm (95% CI:25.3-36.3), 39.4 mm(95% CI:34.1-44.8), and 46.1 mm (95% CI:41.1-51.2) for 45° MR, 0°, and 45° LR, respectively. Using paired-samples T-testing, the mean change in distance when moving from 45° MR to 0° was +8.5 mm (P < 0.0001), and from 0° to LR 45°, +6.7 mm (P < 0.0001). There is a significant difference in the distance between the subscapularis tenotomy and the axillary nerve with medial and lateral rotation. Laterally rotating the arm increased the distance by 6.7 mm, reaffirming that positioning the glenohumeral joint in a position of LR during subscapular tenotomy is protective against iatrogenic injury of the axillary nerve. Clin. Anat. 32:268-271, 2019. © 2018 Wiley Periodicals, Inc.

The sensory origin of the sense of effort is context-dependent.

The origin of the sense of effort has been debated for several decades and there is still no consensus among researchers regarding the underlying neural mechanisms. Some advocate that effort perception mainly arises from an efference copy originating within the brain while others believe that it is predominantly carried by muscle afferent signals. To move the debate forward, we here tested the hypothesis that there is not one but several senses of effort which depend on the way it is evaluated. For this purpose, we used two different psychophysical tests designed to test effort perception in elbow flexors. One was a bilateral isometric force-matching task in which subjects were asked to direct similar amounts of effort toward their two arms, while the other consisted of a unilateral voluntary isometric contraction in which subjects had to rate their perceived effort using a Borg scale. Throughout two distinct experiments, effort perception was evaluated before and following different tendon vibration protocols intended to differentially desensitize muscle spindles and Golgi tendon organs, and to affect the gain between the central effort and muscle contraction intensity. By putting all the results together, we found that spindle afferents played divergent roles across tasks. Namely, while they only acted as modulators of motor pathway excitability during the bilateral task, they clearly intervened as the predominant psychobiological signal of effort perception during the unilateral task. Therefore, the sensory origin of the sense of effort is not central or peripheral. Rather, it is context-dependent.