Increasing Pitch Count is Associated with Increasing Elbow Flexion Angle at Ball Release in Youth Baseball Pitchers.

BACKGROUND: Baseball is one of the most popular sports among youth athletes in the United States, and among these players, pitchers are at a particularly high risk of sustaining an injury. Overuse of the arm from repetitive pitching is a common mechanism for injury. Despite the attention that overuse injury has received, little is known regarding the mechanism that leads to elbow injury. This study aims to determine the effect of increasing pitch count on elbow flexion at ball release in a youth pitching cohort. The authors hypothesize that elbow flexion will increase as pitch count increases. METHODS: Study subjects included volunteers from youth baseball players from local teams and public advertisements. Retro-reflective markers attached to bony landmarks were placed on the players according to ISG recommendations. Pitchers threw an indoor simulated game. Three-dimensional marker trajectories were collected using a 12-camera optical motion capture system, and ball velocity was captured using a radar gun. Voluntary maximal isometric strength of the internal and external rotators was evaluated before and after pitching. Paired two-tailed t-tests were performed to determine if a significant change occurred between the fresh and fatigued sets. RESULTS: Twelve adolescent male pitchers were recruited. Eleven of 12 pitchers completed the prescribed 6 sets of 15 pitches, culminating in a 90-pitch simulated game. The ball speed in the second set was found to be the highest in all pitchers and was considered the "peak set" (p = .021) while ball speed was the slowest in the sixth set of pitches and was therefore considered the "fatigue set" (p = .001). There was a moderate but statistically significant inverse correlation between elbow flexion at ball release and maximum internal rotation velocity (p = .005). Elbow flexion at ball release was also significantly positively correlated with shoulder abduction at ball release (p = 0.004). Elbow flexion at ball release was not significantly correlated with ball velocity (p=.108). DISCUSSION: In a simulated game laboratory setting, increasing pitch count was associated with increasing elbow flexion angle at ball release in youth baseball pitchers. These findings demonstrate that pitching with fatigue may cause biomechanical changes that have been associated with increased rates of elbow injury in the adult throwing population. Further investigation on the association between elbow flexion angle and elbow injury in the youth baseball population is needed.

The Outcome of Spinal Accessory Nerve Transfer to the Musculocutaneous Nerve in Birth Brachial Plexus Palsy.

PURPOSE: Patients with brachial plexus birth injury with limited intraplexal donors require the use of extraplexal donors. Concern regarding the potential for respiratory problems resulting from the harvest of intercostal nerves or the phrenic nerve suggests the need for other options. Transfer of the spinal accessory nerve (SAN) is one option for restoring elbow flexion in adult patients; however, there are few reports of the results of this transfer in brachial plexus birth injury. This study aimed to report the result of SAN transfer to the musculocutaneous nerve (MCN) in brachial plexus birth injury. METHODS: Patients who had undergone SAN to MCN nerve transfer were included in this study. Patients were classified according to Narakas classification. The chart was reviewed for the time for recovery of elbow flexion according to the Active Movement Scale (AMS). RESULTS: Eleven patients underwent SAN to MCN transfers with interpositional sural nerve grafts. Mean birthweight was 4,070 grams (range: 3,300-4,670). Mean time to operation was 6.5 months (range: 4-10). Of the 11 patients, two were of Narakas type 3, whereas the others were of type 4. One patient did not recover elbow flexion and underwent later tendon transfer, whereas the other 10 patients reached AMS grade M6 recovery. The median time for AMS grade M1 elbow flexion recovery was eight months (interquartile range: 6.2-8.8) and for AMS grade M5 was 26 months (interquartile range: 14.2-36.5). CONCLUSIONS: Spinal accessory nerve to MCN transfer with an interposition nerve graft is a viable option for restoring elbow flexion. However, long-term outcomes of this procedure have yet to be fully demonstrated. TYPE OF STUDY/LEVEL OF EVIDENCE: Case series IV.

Upper limb motor assessment for stroke with force, muscle activation and interhemispheric balance indices based on sEMG and fNIRS.

Introduction: Upper limb rehabilitation assessment plays a pivotal role in the recovery process of stroke patients. The current clinical assessment tools often rely on subjective judgments of healthcare professionals. Some existing research studies have utilized physiological signals for quantitative assessments. However, most studies used single index to assess the motor functions of upper limb. The fusion of surface electromyography (sEMG) and functional near-infrared spectroscopy (fNIRS) presents an innovative approach, offering simultaneous insights into the central and peripheral nervous systems. Methods: We concurrently collected sEMG signals and brain hemodynamic signals during bilateral elbow flexion in 15 stroke patients with subacute and chronic stages and 15 healthy control subjects. The sEMG signals were analyzed to obtain muscle synergy based indexes including synergy stability index (SSI), closeness of individual vector (CV) and closeness of time profile (CT). The fNIRS signals were calculated to extract laterality index (LI). Results: The primary findings were that CV, SSI and LI in posterior motor cortex (PMC) and primary motor cortex (M1) on the affected hemisphere of stroke patients were significantly lower than those in the control group (p < 0.05). Moreover, CV, SSI and LI in PMC were also significantly different between affected and unaffected upper limb movements (p < 0.05). Furthermore, a linear regression model was used to predict the value of the Fugl-Meyer score of upper limb (FMul) (R2 = 0.860, p < 0.001). Discussion: This study established a linear regression model using force, CV, and LI features to predict FMul scale values, which suggests that the combination of force, sEMG and fNIRS hold promise as a novel method for assessing stroke rehabilitation.

Comparison of decrease in elbow flexion strength in patients after tenotomy and tenodesis of the long head of the biceps brachii.

NTRODUCTION: The last two decades have been leading to the development of several types of surgical techniques and procedures to manage the LHB lesions. This paper analyses and compares the difference in muscle strength pre- and post-operatively in two most commonly used surgical procedures - LHB tenotomy and tenodesis. METHOD: The study includes 68 patients who underwent surgery between 2016 and 2020. The patients who had met the prospective study inclusion criteria were divided into two groups based on type of surgery they had undergone (LHB tenotomy or tenodesis); each group consisted of 34. The muscle strength during elbow flexion was measured preoperatively and postoperatively using the Commander Echo Console ultrasound muscle testing device. All patients enrolled in the study had been assessed for elbow flexion strength preoperatively. The muscle strength was measured preoperatively and then 3 years postoperatively (12 to 60 months) on average. CONCLUSION: The study confirmed that the patients who had undergone LHB tenodesis show a significantly lower decrease in elbow flexion strength and a significantly lower incidence of "Popeye" deformity than the patients after LHB tenotomy. Moreover, in the tenodesis group, it was possible to initiate rehabilitation earlier. The incidence of postoperative complications was almost identical in both groups of patients (Tab. 10, Fig. 6, Ref. 40).

Functional Free Muscle Transfer for Reconstruction of Traumatic Adult Brachial Plexus Injuries.

Traumatic brachial plexus injury is the most common indication for functional free muscle transfer, and elbow flexion recovery is the functional target, followed by shoulder stability and hand reanimation. In this article, we provide a literature review of functional free muscle transfer (FFMT) for adult traumatic brachial plexus injuries and the surgical technical recommendations to achieve the best functional results with FFMT for adult traumatic brachial plexus injuries.

Prevalence and predictors of elbow flexion contractures during early childhood following brachial plexus birth injury.

BACKGROUND: Elbow flexion contracture development in school-age children with a brachial plexus birth injury (BPBI) is common. Reports indicate onset between 2 and 4 years; however, little is known about early childhood prevalence, development, and trajectory of these contractures. PURPOSE: To determine the prevalence and predictors of BPBI elbow flexion contractures during early childhood. STUDY DESIGN: A retrospective cross-sectional study. METHODS: Demographic, diagnostic, treatment, and elbow contracture data were collected for children with a BPBI <4 years between 2015 and 2019 from a prospectively collected database. Spinal root motor contributions and injury were determined using Active Movement Scale (AMS) scores at 6 weeks of age and used to predict contracture development. RESULTS: Of the 171 children that met inclusion criteria, 87% (n = 149) had upper plexus injuries. The mean age at the time of evaluation for an elbow contracture was 21.4 ± 12.7 months. The prevalence of elbow flexion contractures was 22% (n = 38), with mean onset at 13.4 ± 11.0 months. Mean contracture degree was -10.8 ± -6.9 degrees with 76% (n = 29) <-10 degrees. AMS shoulder abduction, flexion, and external rotation; elbow flexion; forearm supination; and wrist extension scores at a mean 2.3 ± 1.4 months were significantly lower in children who developed elbow flexion contractures (p < 0.001). Logistic regression found that low AMS elbow flexion with high elbow extension scores were a significant (p < 0.003) predictor of elbow contracture development. CONCLUSIONS: The prevalence of elbow flexion contractures in early childhood is greater than previously understood. These findings indicate that C5-C6 injury affecting elbow flexion with relative preservation of elbow extension is a predictor of contracture development. Further research is needed to investigate the nature and sequelae of C5-C6 injury and its effects on elbow flexion contracture development.

Intercostal Nerve Transfer for Biceps Reinnervation in Obstetrical Brachial Plexus Palsy: A Preferred Reporting Items for Systematic Reviews and Meta-Analysis for Individual Patient Data Systematic Review using Individualized Fusion and Comparison to Supraclavicular Exploration and Nerve Grafting.

Introduction: The objective of this study was to search existing literature on nerve reconstruction surgery in patients with obstetric brachial plexus palsy to determine whether treatment with supraclavicular exploration and nerve grafting produced better elbow flexion outcomes compared to intercostal nerve transfer. Methods: This study was a systematic review following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis for Individual Patient Data guidelines. A systematic search was conducted using multiple databases. An ordinal regression model was used to analyze the effect of using supraclavicular exploration and nerve grafting or intercostal nerve on elbow flexion with the two scores measured: elbow flexion Medical Research Council scores and Toronto active movements scale scores for elbow flexion. Results: A final patient database from 6 published articles consisted of 83 supraclavicular exploration and nerve grafting patients (73 patients with Medical Research Council and 10 patients with Toronto score) and 7 published articles which consisted of 131 intercostal nerve patients (84 patients with Medical Research Council and 47 patients with Toronto scores). Patients who underwent supraclavicular exploration and nerve grafting presented with an average Medical Research Council score of 3.9 ± 0.72 and an average Toronto score of 6.2 ± 2.2. Patients who underwent intercostal nerve transfer presented with an average Medical Research Council score of 3.9 ± 0.71 and an average Toronto score of 6.4 ± 1.2. There was no statistical difference between supraclavicular exploration and nerve grafting and intercostal nerve transfer when utilizing Medical Research Council elbow flexion scores (ordinal regression: 0.3821, standard error: 0.4590, p = 0.2551) or Toronto Active Movement Scale score for elbow flexion (ordinal regression: 0.7154, standard error: 0.8487, p = 0.2188). Conclusion: Regardless of surgical intervention utilized (supraclavicular exploration and nerve grafting or intercostal nerve transfers), patients had excellent outcomes for elbow flexion following obstetric brachial plexus palsy when utilizing Medical Research Council or Toronto scores for elbow flexion. The difference between these scores was not statistically significant. Type of study/Level of evidence: Therapeutic Study: Investigating the Result of Treatment/level III.

Telehealth-Enabled In-Home Elbow Rehabilitation for Brachial Plexus Injuries Using Deep-Reinforcement-Learning-Assisted Telepresence Robots.

Due to damage to the network of nerves that regulate the muscles and feeling in the shoulder, arm, and forearm, brachial plexus injuries (BPIs) are known to significantly reduce the function and quality of life of affected persons. According to the World Health Organization (WHO), a considerable share of global disability-adjusted life years (DALYs) is attributable to upper limb injuries, including BPIs. Telehealth can improve access concerns for patients with BPIs, particularly in lower-middle-income nations. This study used deep reinforcement learning (DRL)-assisted telepresence robots, specifically the deep deterministic policy gradient (DDPG) algorithm, to provide in-home elbow rehabilitation with elbow flexion exercises for BPI patients. The telepresence robots were used for a six-month deployment period, and DDPG drove the DRL architecture to maximize patient-centric exercises with its robotic arm. Compared to conventional rehabilitation techniques, patients demonstrated an average increase of 4.7% in force exertion and a 5.2% improvement in range of motion (ROM) with the assistance of the telepresence robot arm. According to the findings of this study, telepresence robots are a valuable and practical method for BPI patients' at-home rehabilitation. This technology paves the way for further research and development in telerehabilitation and can be crucial in addressing broader physical rehabilitation challenges.

Versatility of the double fascicular transfer in reconstruction of elbow flexion paralysis: Intermediate term follow-up and patient-related outcome measures.

OBJECTIVES: The use of fascicle transfers in the reconstruction of traumatic brachial plexus injury is well established, but limited evidence is available regarding their use in atraumatic elbow flexion paralysis. This retrospective case review aimed to verify whether median and ulnar fascicle transfers are similarly effective in atraumatic versus traumatic elbow flexion paralysis when measured using the British Medical Research Council (MRC) scale, Brachial plexus Assessment Tool (BrAT) and Stanmore Percentage of Normal Elbow Assessment (SPONEA) scores at long-term follow-up. METHODS: All median and ulnar fascicle transfer cases performed at the Queen Elizabeth Hospital Birmingham between August 2007 and November 2018 were reviewed to compare the outcomes of transfers performed for traumatic and atraumatic indications. Data on patient demographics, mechanism and nature of injury, date of injury or symptom onset, date of operation, and other nerve transfers performed were collected. Outcome measures collected included the British MRC scale and two patient-reported outcome measures (PROMs), BrAT and SPONEA. RESULTS: In total, 34 patients with 45 median and ulnar fascicle transfers were identified. This included 27 traumatic and seven atraumatic brachial plexus insults. Thirty patients had sufficient follow-up to be included in MRC analysis and 17 patients had sufficient follow-up to be included in PROM analysis. No significant differences were found between traumatic and atraumatic subgroups for median MRC, BrAT, or SPONEA scores. CONCLUSIONS: This study suggests that nerve transfers might be considered effective reconstructive options in atraumatic pathology and provides validation for further research on the subject.

Kinematic and Kinetic Comparisons of Arm Slot Position Between High School and Professional Pitchers.

Background: Throwing arm kinetics differ in pitchers at varying arm slot (AS) positions (frontal-plane arm position at ball release relative to the vertical axis). Purpose: To determine how kinematic and kinetic values differ between professional and high school pitchers with varying AS positions, and whether these differences are similarly observed in both populations. Methods: High school (n = 130) and professional (n = 288) pitchers threw 8 to 12 fastballs under 3-dimensional motion capture technology. Pitchers in each cohort were subdivided based on mean AS position at ball release: AS1 (least degree of AS: most overhand throwing styles), AS2 (intermediate degree of AS: three-quarter throwing styles), or AS3 (greatest degree of AS: most sidearm throwing styles). Kinetic and kinematic parameters were compared between groups. Study Design: Controlled laboratory study. Results: High school pitchers had a more overhand AS at ball release (50° ± 11°) compared with professional pitchers (58° ± 14°) (P < .001). In both cohorts, AS1 pitchers had significantly greater shoulder abduction (high school, P <0.001; professional, P <0.0001) and lateral trunk flexion (high school, P < 0.001; professional, P <0.0001) at ball release compared with AS3 pitchers. Professional pitchers with an AS3 position had significantly delayed timing of maximum upper trunk angular velocity compared with AS1 pitchers (64% ± 7% vs 57% ± 7% of pitch time, respectively; P < .0001). A significant positive correlation between AS and elbow flexion torque was found in high school pitchers (P = .002; ß = 0.28), and a significant negative correlation between AS and elbow varus torque (P < .001; ß = -0.22) and shoulder internal rotation torque (P < .001; ß = -0.20) was noted in professional pitchers. Conclusion: AS position was related to shoulder abduction and trunk lateral tilt. Professional and high school pitchers with varying AS positions did not experience similar changes in throwing arm kinetics. Clinical Relevance: In professional pitchers, the earlier onset of maximum upper trunk angular velocity with overhand throwing style may reflect inappropriate pelvis-trunk timing separation, a parameter implicated in upper extremity injury, and the negative correlation between AS and elbow varus and shoulder internal rotation torque suggests that both excessive and minimal AS positions have negative implications.

Functional reconstruction of elbow flexion with latissimus dorsi muscle rotational transfer: two case reports.

BACKGROUND: We report two cases of biceps brachii and brachialis paralysis due to musculocutaneous nerve injury in which elbow joint flexion was reconstructed using rotational transfer of the latissimus dorsi muscle with sutures to the radial and ulnar tuberosities, thereby enabling flexion by simultaneous activation of the humeroradial and humeroulnar joints. In cases of associated brachialis paralysis, weaker flexion strength can be expected when the forearm is in a pronated position than when it is in a supinated state. To the best of our knowledge, no previous study has reported the rotational position of the forearm during elbow joint flexion reconstruction. CASE PRESENTATION: Case 1 involved a 30-year-old Asian male who presented with a rupture of the musculocutaneous, median, radial, and ulnar nerves. Reconstruction was performed by rotational transfer of the latissimus dorsi muscle. In this case, the supination and pronation flexion forces were equal. Case 2 involved a 50-year-old Asian man who presented with partial loss of the musculocutaneous nerve, biceps brachii, and pectoralis major due to debridement. Reconstruction was performed by rotational transfer of the latissimus dorsi muscle. In this case, supination and pronation flexion strengths were demonstrated to be equal. Our reconstruction method used the rotational transfer of the latissimus dorsi muscle; the distal muscle flap was divided into radial and ulnar sides to allow elbow joint flexion by simultaneously activating the humeroradial and humeroulnar joints. These sides were then fixed to the anchors at the radial and ulnar tuberosities. Finally, they were wrapped around the myotendinous junction of the biceps brachii or brachialis and secured using sutures. CONCLUSIONS: Although larger studies are required to verify these methods, this case study successfully demonstrates the following: (1) the flexion strength in the supinated position was equal to that in the pronated position; (2) the stability of the humeroradial and humeroulnar joints was unaffected by the forearm's rotational position; and (3) a satisfactory range of motion of the elbow joint was obtained, with no complications.

Triceps-to-Biceps Tendon Transfer for Restoration of Elbow Flexion in Brachial Plexus Injury.

PURPOSE: Restoring elbow flexion is a reconstructive priority in patients with brachial plexus injuries. This study aimed to evaluate the results and assess factors contributing to outcomes of triceps-to-biceps tendon transfer in patients presenting with delayed or chronic upper brachial plexus injury. METHODS: Patients with traumatic brachial plexus injuries undergoing triceps-to-biceps tendon transfer at a single institution's multidisciplinary brachial plexus center between 2001 and 2021 were retrospectively reviewed. The entire triceps tendon was transferred around the lateral aspect of the arm, secured to the radius with a tenodesis button, and reinforced with a side-to-side tendon transfer to the biceps tendon. Primary outcomes include the modified British Medical Research Council (mBMRC) elbow flexion strength and active elbow range of motion. RESULTS: Twelve patients (eight men and four women; mean age, 45.2 years) were included. The mean follow-up was 10.4 (range, 5-34) months. Nine patients achieved mBMRC ≥3. Five patients achieved mBMRC 4. Average active elbow flexion was 119°, with average extension deficit of 11°. There were three patients with unsatisfactory results, achieving mBMRC 2 elbow flexion. CONCLUSIONS: Triceps-to-biceps tendon transfer is an excellent tendon transfer option for restoring elbow flexion in certain patients with an adequately functioning triceps muscle, who present with a delayed or chronic brachial plexus injury. Although most patients achieved mBMRC ≥3 elbow flexion, there was an expected permanent loss of elbow active extension with a residual elbow flexion contracture. LEVEL OF EVIDENCE: Therapeutic IV.

Optimal Distal Tendon Insertion Point for Elbow Flexion in Free-Functioning Gracilis Muscle Transfer for Panbrachial Plexus Injuries: A Cadaveric Study.

PURPOSE: Following pan-brachial plexus injuries, restoration of elbow flexion is widely accepted as the reconstructive priority. A gracilis free functioning muscle transfer (FFMT) can be used to restore elbow flexion alone with insertion into the biceps brachii (BIC) or brachioradialis (BRD) tendons or restore combined elbow and finger flexion with a more distal insertion into the flexor digitorum profundus (FDP) tendons. Using cadaveric experiments, we determined the peak instantaneous moment arm for each insertion option. METHODS: Six simulated gracilis transfer surgeries were performed using both arms of three fresh-frozen full body cadaveric specimens (age: 79 + 10 years. 2 female). The gracilis muscles from both legs were harvested and transferred to the contralateral upper extremity. The elbow was manually moved through three flexion-extension cycles while the instantaneous moment arm was calculated from measurements of gracilis excursion and elbow joint angle for the three distal insertion sites. RESULTS: Peak instantaneous moment arm for all three insertions occurred at an elbow angle between 83° to 92° with a magnitude ranging from 33 mm to 54 mm. The more distal (FDP/BRD) insertions produced a significantly greater (∼1.5 times) peak elbow flexion instantaneous moment arm compared to the BIC insertion. CONCLUSIONS: Based on the instantaneous moment arm, the gracilis FFMT distal insertion locations could result in greater reconstructed elbow flexion strength. In addition, direct measurement of the shape and magnitude of the moment arm curve for differing insertion sites allows high resolution surgical planning and model testing. CLINICAL RELEVANCE: This study presents the first direct experimental quantification of the gracilis FFMT instantaneous moment arm. The experimental evidence supports the use of FDP/BRD insertion locations by providing a quantitative explanation for the increased elbow flexion torque observed clinically in patients with a gracilis FFMT and distal FDP insertion.

Tendon transfer from a re-innervated triceps to the biceps for restoration of elbow flexion in total brachial plexus palsy.

OBJECTIVES: This study aimed to evaluate the outcomes of the tendon transfer from a reinnervated triceps to biceps in the context of total brachial plexus palsy. METHODS: We conducted a retrospective study. Patients had reinnervation of the triceps either by spontaneous recovery or by nerve transfer. Functional results were assessed by strength and range of motion. The level of patient satisfaction was measured on a scale from 0 to 10. RESULTS: Six patients (6 transfers) were included. Two triceps had spontaneous reinnervation and the other four through neurotization of intercostal nerves. All patients recovered strength to M4 in flexion with an average secondary deficit of 10° (5°-15°). The mean level of satisfaction was measured at 7/10 (6-8). CONCLUSIONS: This tendon transfer is a reliable and simple solution for supportive restoration of elbow flexion. Systematic reinnervation of active extension of the elbow should be proposed for the gain in function that it represents but also for the supportive therapeutic opportunity that it offers should nerve surgery for elbow flexion fail.

Unipolar Latissimus Dorsi Transfer for Restoration of Elbow Flexion in Residual Post-traumatic Brachial Plexus Palsy Associated with Distal Humeral Fractures.

Introduction Elbow flexion is indispensable for both functioning and nonfunctioning hands. It is well perceived that restoration of elbow function is the first reconstructive priority in cases of brachial plexus injuries. The authors assessed the impact of associated distal humeral fractures on the functional outcome after unipolar latissimus dorsi transfer (ULDT) for restoration of elbow flexion in patients with residual brachial plexus palsy (BPP). Patients and Methods Twenty-three patients operated for restoring elbow flexion after residual post-traumatic BPP (with or without distal humeral fracture) by unipolar latissimus dorsi transfer (ULDT) were reviewed for a retrospective study. Patients were divided into two groups; associated distal humeral fracture group (HF-group; 10 patients) and non-associated distal humeral fracture group (NHF-group; 13 patients). Elbow flexion active range of motion (AROM), flexion deformity in addition to Mayo Elbow Performance Score (MEPS) were assessed. Results In both groups there were statistically better postoperative MEPS grading ( p = 0.007, p = 0.001 , respectively) and scoring with a mean of 81 ± 16.1 and 90 ± 4.6, respectively ( p < 0.001). The mean postoperative elbow flexion AROM was statistically better in both groups. The mean supination AROM was better in NHF group ( p = 0.057). Conclusion The use of ULDT in residual post-traumatic BPP is an efficient procedure in regaining functional flexion and supination. An associated distal humeral fracture does not significantly affect the final functional outcome. Level of Evidence Level IV.

Increase in conduction velocity in myelinated nerves due to stretch - An experimental verification.

Background: Based on published experimental evidence, a recent publication revealed an anomalous phenomenon in nerve conduction: for myelinated nerves the nerve conduction velocity (NCV) increases with stretch, which should have been the opposite according to existing concepts and theories since the diameter decreases on stretching. To resolve the anomaly, a new conduction mechanism for myelinated nerves was proposed based on physiological changes in the nodal region, introducing a new electrical resistance at the node. The earlier experimental measurements of NCV were performed on the ulnar nerve at different angles of flexion, focusing at the elbow region, but left some uncertainty for not reporting the lengths of nerve segments involved so that the magnitudes of stretch could not be estimated. Aims: The aim of the present study was to relate NCV of myelinated nerves with different magnitudes of stretch through careful measurements. Method: Essentially, we duplicated the earlier published NCV measurements on ulnar nerves at different angles of flexion but recording appropriate distances between nerve stimulation points on the skin carefully and assuming that the lengths of the underlying nerve segment undergoes the same percentages of changes as that on the skin outside. Results: We found that the percentage of nerve stretch across the elbow is directly proportional to the angle of flexion and that the percentage increase in NCV is directly proportional to the percentage increase in nerve stretch. Page's L Trend test also supported the above trends of changes through obtained p values. Discussion: Our experimental findings on myelinated nerves agree with those of some recent publications which measured changes in CV of single fibres, both myelinated and unmyelinated, on stretch. Analyzing all the observed results, we may infer that the new conduction mechanism based on the nodal resistance and proposed by the recent publication mentioned above is the most plausible one to explain the increase in CV with nerve stretch. Furthermore, interpreting the experimental results in the light of the new mechanism, we may suggest that the ulnar nerve at the forearm is always under a mild stretch, with slightly increased NCV of the myelinated nerves.

Aging-induced alterations in EEG spectral power associated with graded force motor tasks.

BACKGROUND: It has been demonstrated that in young and healthy individuals, there is a strong association between the amplitude of EEG-derived motor activity-related cortical potential or EEG spectral power (ESP) and voluntary muscle force. This association suggests that the motor-related ESP may serve as an index of central nervous system function in controlling voluntary muscle activation Therefore, it may potentially be used as an objective marker to track changes in functional neuroplasticity due to neurological disorders, aging, and following rehabilitation therapies. To this end, the relationship between the band-specific ESP-combined spectral power of EEG oscillatory and aperiodic (noise) components-and voluntary elbow flexion (EF) force has been analyzed in elder and young individuals. METHODS: 20 young (22.6 ± 0.87 year) and 28 elderly (74.79 ± 1.37 year) participants performed EF contractions at 20%, 50%, and 80% of maximum voluntary contraction (MVC) while high-density EEG signals were recorded. Both the absolute and relative ESPs were computed for the EEG frequency bands of interest. RESULTS: The MVC force generated by the elderly was foreseeably lower than that of the young participants. Compared to young, the elderly cohort's (1) total ESP was significantly lower for the high (80% MVC) force task; (2) relative ESP in beta band was significantly elevated for the low and moderate (20% MVC and 50% MVC) force tasks; (3) absolute ESP failed to have a positive trend with force for EEG frequency bands of interest; and (4) beta-band relative ESP did not exhibit a significant decrease with increasing force levels. CONCLUSIONS: As opposed to young subjects, the beta-band relative ESP in elderly did not significantly decrease with increasing EF force values. This observation suggests the use of beta-band relative ESP as a potential biomarker for age-related motor control degeneration.

Risk prediction model for unsuccessful elbow flexion recovery after nerve transfer surgery in patients with brachial plexus injury.

OBJECTIVE: Nerve transfer surgery has been a mainstay treatment of brachial plexus injury, with varying success rates. Patients undergoing unsuccessful surgery are left with a useless limb for at least 2 years. Preoperative prediction has become a topic of interest to avoid an unsuccessful nerve transfer surgery. This study aimed to find strong predictive factors and develop a prediction model for unsuccessful functional elbow flexion recovery 2 years after a nerve transfer surgery in patients with brachial plexus injury. METHODS: This retrospective study reviewed the medical records of 987 patients with traumatic brachial plexus injury who underwent brachial plexus surgery by five hand and microsurgery surgeons at a single tertiary care referral center from December 2001 to July 2018. Four hundred thirty-three patients were eligible for analysis. Patient demographic data, injury factors, surgical details, and postoperative factors were collected. Multivariable logistic regression was used to identify strong prognostic factors for unsuccessful nerve transfer surgery for elbow flexion. A simplified model was developed by rounding the coefficient to the nearest 0.5 score or an integer. Both original and simplified models were validated using the Hosmer-Lemeshow goodness-of-fit test and bootstrapping. RESULTS: A full, original prognostic model from a stepwise backward logistic regression consisted of a BMI ≥ 23 kg/m2 (p = 0.015), smoking (p = 0.046), total arm-type injury (p = 0.033), donor nerve (p < 0.001), associated upper-extremity fracture (p = 0.013), and associated ipsilateral vascular injury (p = 0.095). The areas under the receiver operating characteristic curve of the original and simplified models were 0.765 and 0.766, respectively. The Hosmer-Lemeshow test showed good agreement of predicted and observed probability of the original (p = 0.49) and simplified (p = 0.19) models. Bootstrapping estimated an average optimism (1.9%) in the original model and minimal optimism (0.1%) in the simplified model. CONCLUSIONS: The prediction model for failed elbow flexion recovery after nerve transfer surgery in traumatic brachial plexus injury was developed with good predictive value and internal validity. An alternative treatment, i.e., primary free functioning muscle transfer, should be offered in preoperative counseling in cases of a very high risk of failure.

Influence of an armrest support on handgrip strength in different arm and shoulder flexion angles in overhead postures.

A study was undertaken in which the handgrip strength in three arm positions above the shoulder was measured to compare handgrip strength when arm support is used and when it is not used. Grip forces were generated in pairs of flexion angles, corresponding to shoulder and elbow at 90°-90°, 135°-45° and 160°-20°. Thirty-two participants completed the present study; 23 men and nine women with a median age of 23.1 (SD ±3.6) years. A manual handgrip dynamometer (0-90 kg) and an adjustable angle arm support (AAAS) were used during the data collection. Two-way analysis of variance (ANOVA) for repeated measurements indicates a significant effect of the AAAS factor on the handgrip strength, as well as on the AAAS × angle interaction. However, there is no significant effect of the angle factor on the AAAS × angle interaction.

Shear wave elastography characterizes passive and active mechanical properties of biceps brachii muscle in vivo.

Mechanical characterization of individual muscles in their in vivo environment is not well studied. Shear wave elastography (SWE) as a non-invasive technique was shown to be promising in quantifying the local mechanical properties of skeletal muscles. This study aimed to investigate the mechanics of the biceps brachii muscle (BB) derived from SWE in relation to elbow joint position and contraction intensity during isometric contraction. 14 healthy, young subjects participated in the study and five different joint positions (60°-180° elbow angle) were investigated. Shear elastic modulus and surface electromyography (sEMG) of the BB and elbow torque were measured simultaneously, both in passive (i.e., resting) and active states during slow, sub-maximal isometric ramp contractions up to 25%, 50%, and 75% of the maximum voluntary contraction. At passive state, the shear elastic modulus of the BB increased with increasing elbow angle (p < 0.001). Maximum elbow flexion torque was produced at 60° and it decreased with increasing elbow angle (p = 0.001). During sub-maximal contractions, both elbow angle (p < 0.001) and contraction intensity (p < 0.001) had significant effects on the shear elastic modulus but only contraction intensity (p < 0.001) affected sEMG amplitude of the BB. Although torque was decreased at extended elbow positions (150°, 180°), higher active shear elastic modulus of BB muscle was found compared to flexed positions (60°, 90°). Linear regression of the BB sEMG amplitude over elbow torque showed good agreement for all joint positions (R2 between 0.69 and 0.89) while the linear agreement between shear elastic modulus of BB and elbow torque differed between flexed (R2 = 0.70 at 60° and R2 = 0.79 at 90°) and extended positions (with the lowest R2 = 0.57 at 150°). We conclude that using SWE, we can detect length-dependent mechanical changes of BB both in passive and active states. More importantly, SWE can be used to characterize active muscle properties in vivo. The present findings have critical importance for developing muscle stiffness as a measure of individual muscle force to validate muscle models and using SWE in clinical diagnostics.