How the Forearm Works.

SUMMARY: Hand rotation and the ability to apply force and overcome external load are due to the coordinated activity of forearm bones, the interosseous ligament, and involved muscles. The following review is a detailed description of the anatomy and mechanics which illustrates how the forearm works.

Exclusive extragenital lichen sclerosis in a child presenting in a lichen planus distribution.

Lichen sclerosus (LS) is a chronic inflammatory dermatosis primarily affecting the genitalia, commonly characterized by pearly-white papules and plaques. Although predominantly affecting females, LS can manifest across all age groups, with a bimodal distribution observed in prepubescent girls and postmenopausal women. This case report presents an unusual instance of exclusive extragenital LS in a 10-year-old girl, showcasing hyperpigmented patches and wrinkled plaques resembling lichen planus on her forearms and lower legs. Histopathological analysis confirmed LS, revealing distinctive epidermal changes and lymphocytic infiltrates. The absence of mucosal involvement and unique clinical presentation differentiated this case from typical LS manifestations. Treatment with topical clobetasol propionate demonstrated significant improvement in pruritus. Extragenital LS is infrequent, particularly among children, and its diagnosis necessitates a comprehensive clinicopathological correlation. The reported case contributes valuable insights into this uncommon variant, emphasizing the importance of accurate diagnosis and tailored treatment strategies. Additionally, it highlights the efficacy of high-potency topical corticosteroids in managing this condition.

[Application of free forearm flap in reconstruction of postoperative defect of external nasal malignant tumor].

Objective:To investigate the therapeutic effect of free forearm flaps in repairing the postoperative defect of external nasal malignant tumor. Methods:Six patients with nasal malignant tumor were treated with radical operation of external nasal malignant tumor and simultaneous reconstruction of external nasal defects with free forearm flap. Preoperative Allen experiment, ultrasonic Doppler blood flow meter or CT angiography confirmed that the forearm blood vessels were in good condition. Results:The free forearm flaps were obtained from six patients, and completely survived. During the follow-up period of 6-12months, all patients had good external nasal morphology, good nasal function, no nasal obstruction and anterior nostril stenosis, no obvious complications in donor hand and no local cancer recurrence. Conclusion:The free forearm flap is a reliable method to reconstruction the postoperative defect of external nasal malignant tumor, with a high success rate and good recovery of morphology and function recovery.

Acute effects of energy drink consumption on microvascular reactivity in young male volunteers at rest: a randomized trial.

Energy drinks are nonalcoholic beverages whose main ingredients are sugar, taurine, and caffeine. The consumption of energy drinks is increasing worldwide, but only a few conflicting studies have investigated the vascular effects of energy drinks in young adults. The aim of this study was to evaluate microvascular reactivity before and after energy drinks consumption in young healthy male volunteers. This was a cross-sectional prospective study. Microvascular reactivity signals were evaluated in the skin of the forearm using laser speckle contrast imaging with acetylcholine (ACh) iontophoresis before and 90 and 180 min after the randomized consumption of one ED or the same volume of water (control), followed by a postocclusive reactive hyperemia (PORH) test. Thirty-two volunteers were evaluated (age: 25.4±4.3 years). Energy drink consumption prevented the rest-induced reduction in cutaneous vascular conductance over time that was observed in the control group. In the control group, there were significant reductions in microvascular vasodilation at 90 and 180 min compared to baseline (P=0.004), but this was not the case in the energy drink group (P=0.76). Our results demonstrated that the reduction in microvascular conductance associated with prolonged immobility can be prevented by the consumption of one energy drink, highlighting the vasodilator effects of this beverage in young individuals at rest. The between-study variability in terms of the brand of energy drinks and the ingested volume, as well as the method of vascular evaluation and the inclusion criteria, may explain the discrepancies among previous studies on the vascular effects of energy drinks.

An Ergonomic Golf Grip Leads to Lower Forearm Muscle Activity - A Prospective Case Series of 30 Right-Handed Amateur and Professional Golfers.

BACKGROUND: The elbow is a common site for overuse injuries in golfers. Tendinopathies, such as medial and lateral epicondylitis, are frequently diagnosed in amateur and professional golfers. The aim of our study was to determine the effect of an ergonomic golf grip on forearm muscle activity during the five phases of the golf swing. METHODS: Thirty right-handed golfers with a mean age of 32 years (range, 18-70 years) and a mean handicap of 15 (range, 0-43) performed 10 golf swings with a standard and ergonomic golf grip respectively. The mean and maximum muscle activity of the Musculus (M.) extensor carpi radialis brevis (ECRB), M. flexor carpi ulnaris (FCU), M. pronator teres (PT) and M. biceps brachii (BB) of the lead and trail arms were assessed during the five phases of the golf swing using surface electromyography (EMG). Subgroup analyses were performed regarding sex, playing ability (handicap < 10 vs. ≥10), weekly playing time (≤ 5 h, 5-20 h, > 20 h) and preexisting elbow pain during golfing (VAS < 2 vs. VAS ≥ 2). Significance was set at p < 0.05. RESULTS: An ergonomic golf grip resulted in a reduction in muscle activity in at least one but up to three consecutive phases of the golf swing for the ECRB, FCU and PT of the lead arm and for the PT of the trail arm. Amateurs, a playing time < 20 h per week and golfers without preexisting elbow pain were factors that were associated with greater reductions in muscle activity. CONCLUSION: Forearm muscle activity can be decreased using an ergonomic golf grip, indicating the possible role of an ergonomic golf grip as a preventive measure against overuse syndromes such as medial and lateral epicondylitis. TRIAL REGISTRATION NUMBER: This study was retrospectively registered at the German Clinical Trials Register DRKS-ID: DRKS00033732 (01/03/2024).

Radial Forearm Flap for Esophageal Perforation After Anterior Cervical Hardware Removal: Surgical Technique and Case Report.

CASE: A 51-year-old woman, who had previously undergone C5-C7 anterior cervical discectomy and fusion, presented with symptomatic hardware failure and subsequently underwent instrumentation removal. Her postoperative course was complicated by an esophageal perforation. Despite initial repair using a rotational flap, the leak persisted, prompting esophageal reconstruction with a radial forearm free flap (RFFF). CONCLUSION: Persistent esophageal perforation is exceedingly rare and difficult to treat. This report discusses the surgical technique for RFFF, an excellent option for revising failed sternocleidomastoid rotational flaps. The decision between rotational repair and free flap reconstruction depends on factors such as defect size, vascularization, wound condition, and donor site morbidity.

Integration of Motor Unit Filters for Enhanced Surface Electromyogram Decomposition During Varying Force Isometric Contraction.

Muscles generate varying levels of force by recruiting different numbers of motor units (MUs), and as the force increases, the number of recruited MUs gradually rises. However, current decoding methods encounter difficulties in maintaining a stable and consistent growth trend in MU numbers with increasing force. In some instances, an unexpected reduction in the number of MUs can even be observed as force intensifies. To address this issue, in this study, we propose an enhanced decoding method that adaptively reutilizes MU filters. Specifically, in addition to the normal decoding process, we introduced an additional procedure where MU filters are reused to initialize the algorithm. The MU filters are iterated and adapted to the new signals, aiming to decode motor units that were actually activated but cannot be identified due to heavy superimposition. We tested our method on both simulated and experimental surface electromyogram (sEMG) signals. We simulated isometric signals (10%-70%) with known MU firing patterns using experimentally recorded MU action potentials from forearm muscles and compared the decomposition results to two baseline approaches: convolution kernel compensation (CKC) and fast independent component analysis (fastICA). Our method increased the decoded MU number by a rate of 135.4% ± 62.5 % and 63.6% ± 20.2 % for CKC and fastICA, respectively, across different signal-to-noise ratios. The sensitivity and precision for MUs decomposed using the enhanced method remained at the same accuracy level (p <0.001) as those of normally decoded MUs. For the experimental signals, eight healthy subjects performed hand movements at five different force levels (10%-90%), during which sEMG signals were recorded and decomposed. The results indicate that the enhanced process increased the number of decoded MUs by 21.8% ± 10.9 % across all subjects. We discussed the possibility of fully capturing all activated motor units by appropriately reusing previously decoded MU filters and improving the balance of activated motor unit numbers across varying excitation levels.

Closed-Loop Force Control by Biorealistic Hand Prosthesis With Visual and Tactile Sensory Feedback.

The ability of a novel biorealistic hand prosthesis for grasp force control reveals improved neural compatibility between the human-prosthetic interaction. The primary purpose here was to validate a virtual training platform for amputee subjects and evaluate the respective roles of visual and tactile information in fundamental force control tasks. We developed a digital twin of tendon-driven prosthetic hand in the MuJoCo environment. Biorealistic controllers emulated a pair of antagonistic muscles controlling the index finger of the virtual hand by surface electromyographic (sEMG) signals from amputees' residual forearm muscles. Grasp force information was transmitted to amputees through evoked tactile sensation (ETS) feedback. Six forearm amputees participated in force tracking and holding tasks under different feedback conditions or using their intact hands. Test results showed that visual feedback played a predominant role than ETS feedback in force tracking and holding tasks. However, in the absence of visual feedback during the force holding task, ETS feedback significantly enhanced motor performance compared to feedforward control alone. Thus, ETS feedback still supplied reliable sensory information to facilitate amputee's ability of stable grasp force control. The effects of tactile and visual feedback on force control were subject-specific when both types of feedback were provided simultaneously. Amputees were able to integrate visual and tactile information to the biorealistic controllers and achieve a good sensorimotor performance in grasp force regulation. The virtual platform may provide a training paradigm for amputees to adapt the biorealistic hand controller and ETS feedback optimally.

Movement Diversity and Complexity Increase as Arm Impairment Decreases After Stroke: Quality of Movement Experience as a Possible Target for Wearable Feedback.

Upper extremity (UE) impairment is common after stroke resulting in reduced arm use in daily life. A few studies have examined the use of wearable feedback of the quantity of arm movement to promote recovery, but with limited success. We posit that it may be more effective to encourage an increase in beneficial patterns of movement practice - i.e. the overall quality of the movement experience - rather than simply the overall amount of movement. As a first step toward testing this idea, here we sought to identify statistical features of the distributions of daily arm movements that become more prominent as arm impairment decreases, based on data obtained from a wrist IMU worn by 22 chronic stroke participants during their day. We identified several measures that increased as UE Fugl-Meyer (UEFM) score increased: the fraction of movements achieved at a higher speed, forearm postural diversity (quantified by kurtosis of the tilt-angle), and forearm postural complexity (quantified by sample entropy of tilt angle). Dividing participants into severe, moderate, and mild impairment groups, we found that forearm postural diversity and complexity were best able to distinguish the groups (Cohen's D =1.1, and 0.99, respectively) and were also the best subset of predictors for UEFM score. Based on these findings coupled with theories of motor learning that emphasize the importance of variety and challenge in practice, we suggest that using these measures of diversity and complexity in wearable rehabilitation could provide a basis to test whether the quality of the daily movement experience is therapeutic.

Acute Sympathetic Blockade Improves Insulin-Mediated Microvascular Blood Flow in the Forearm of Adult Human Subjects With Obesity.

BACKGROUND: Obesity is associated with resistance to the metabolic (glucose uptake) and vascular (nitric-oxide mediated dilation and microvascular recruitment) actions of insulin. These vascular effects contribute to insulin sensitivity by increasing tissue delivery of glucose. Studies by us and others suggest that sympathetic activation contributes to insulin resistance to glucose uptake. Here we tested the hypothesis that sympathetic activation contributes to impaired insulin-mediated vasodilation in adult subjects with obesity. METHODS AND RESULTS: In a randomized crossover study, we used a euglycemic hyperinsulinemic clamp in 12 subjects with obesity to induce forearm arterial vasodilation (forearm blood flow) and microvascular recruitment (contrast-enhanced ultrasonography) during an intrabrachial infusion of saline (control) or phentolamine (sympathetic blockade). Insulin increased forearm blood flow on both study days (from 2.21±1.22 to 4.89±4.21 mL/100 mL per min, P=0.003 and from 2.42±0.89 to 7.19±3.35 mL/100 mL per min, P=0.002 for the intact and blocked day, respectively). Sympathetic blockade with phentolamine resulted in a significantly greater increase in microvascular flow velocity (∆microvascular flow velocity: 0.23±0.65 versus 2.51±3.01 arbitrary intensity units (AIU/s) for saline and phentolamine respectively, P=0.005), microvascular blood volume (∆microvascular blood volume: 1.69±2.45 versus 3.76±2.93 AIU, respectively, P=0.05), and microvascular blood flow (∆microvascular blood flow: 0.28±0.653 versus 2.51±3.01 AIU2/s, respectively, P=0.0161). To evaluate if this effect was not due to nonspecific vasodilation, we replicated the study in 6 subjects with obesity comparing intrabrachial infusion of phentolamine to sodium nitroprusside. At doses that produced similar increases in forearm blood flow, insulin-induced changes in microvascular flow velocity were greater during phentolamine than sodium nitroprusside (%microvascular flow velocity=58% versus 29%, respectively, P=0.031). CONCLUSIONS: We conclude that sympathetic activation impairs insulin-mediated microvascular recruitment in adult subjects with obesity.

Comparative analysis of volumetric changes between resection volume of oral tongue cancer and post operative volume of radial forearm flaps.

OBJECTIVES: This study investigates the relationship between the total volume of oral tongue cancer pre-operatively and the RFFF volume post-operatively. MATERIALS AND METHODS: A total of 52 DICOM imaging datasets (CT or MRI) of 26 patients were included in this study. The volume of the desired structure was quantified using semi-automatic segmentation using the software ITK-SNAP. All extracted measurements were validated by two further clinicians at separate instances. RESULTS: The variation of MeanVolTu can be predicted by MeanVolFlap moderately reliable with 59.1% confidence (R-Qua: 0.591). ANOVA Testing to represent how well the regression line fits the data, resulted in the overall regression model being statistically significant in predicting the MeanVolTu (p < 0.001). The flap volume may be predicted using the following algorithm: MeanVolFlap0 = 3241,633 + 1, 322 * MeanVolTu. CONCLUSION: The results of this study show positive correlation between tumor volume and flap volume, highlighting the significance of efficient flap planning with increasing tumor volume. A larger extraction volume of the radial forearm free flap from the donor site compromises the forearm more, thus increasing the probability of post-operative complications. CLINICAL RELEVANCE: Radial forearm free flap design in accordance with its corresponding 3D tumor volume.

Intraneural Nodular Fasciitis of the Radial Nerve: A Case Report.

CASE: We report a case of intraneural nodular fasciitis in the forearm initially suspected as a schwannoma, emphasizing the importance of accurate diagnosis. A 40-year-old woman presented with mass on the lateral aspect of her right forearm and radial neuropathy symptoms for 2 months. An excisional biopsy and histopathological examination confirmed nodular fasciitis. Postoperative evaluation at 4.5 years found no pain, paralysis, or recurrence. CONCLUSION: Awareness of nodular fasciitis is crucial to prevent misdiagnosis and unnecessary treatment. Despite its rapid growth, nodular fasciitis generally has an excellent prognosis without long-term consequences.

Extensive mycetoma in forearm, chest and neck due to Nocardia mexicana.

INTRODUCTION: Mycetoma is a chronic granulomatous inflammatory disease of the subcutaneous tissue, which affects deep structures and bone. Most cases of actinomycetoma are caused by members of the genus Nocardia. CASE PRESENTATION: Here we report the case of a 43-year-old male who presented a disseminated mycetoma on the forearm, chest and neck, characterized by enlarged and erythematous lesions through which seropurulent material drains, and numerous atrophic scars. Molecular identification was performed by 16S gene amplification and sequencing. Nocardia mexicana was identified with 100% identity. Trimethoprim-sulfamethoxazole, diaminodiphenyl sulfone and amikacin was a successful treatment after 6 months. CONCLUSIONS: Nocardia mexicana is a rare organism that causes mycetoma. We report a case of extensive mycetoma on the forearm with spread to the neck and thorax associated with manipulation of the mouth of a calf.

Consistency between the ACGIH TLV for hand activity and proposed action levels for wrist velocity and forearm muscular load based on objective measurements: an example from the assembly industry.

Objectives. This study aimed to investigate the consistency between results of the American Conference for Governmental Occupational Hygienists (ACGIH) threshold limit value (TLV) for hand activity and proposed action levels of objective measurements in risk assessments of work-related musculoskeletal disorders. Methods. Wrist velocities and forearm muscular load were measured for 11 assemblers during one working day. Simultaneously, each assembler's hand activity level (HAL) during three sub-cycles was rated twice on two separate occasions by two experts, using a HAL scale. Arm/hand exertion was also rated by the assemblers themselves using a Borg scale. In total, 66 sub-cycles were assessed and assigned to three exposure categories: A) below ACGIH action limit (AL) (green); B) between AL and TLV (yellow); and C) above TLV (red). The median wrist velocity and the 90th percentile of forearm muscular load obtained from the objective measurements corresponding to the sub-cycles were calculated and assigned to two exposure categories: A) below or C) above the proposed action level. Results. The agreement between ACGIH TLV for hand activity and the proposed action level for wrist velocity was 87%. Conclusions. The proposed action level for wrist velocity is highly consistent with the TLV. Additional studies are needed to confirm the results.

Treatment of Patients With Electrical Injury by Using Modified Forearm Venous Flap: Retrospective Case Series Study.

OBJECTIVE: Severe hand electrical injuries often occur in functional areas such as joints; the repair requires attention to both appearance and function due to the visibility of the hand. This study aimed to present the clinical experience of successfully repairing hand electrical injuries using improved forearm venous flaps. METHODS: From 2020 to 2022, 15 cases of severe hand electrical injuries were diagnosed, including 10 males and 5 females. Among them, 6 cases were repaired in the first web space, 4 in the thumb, 3 in the index finger, 2 in the middle finger, 2 in the ring finger, and 2 in the little finger. The size of venous flaps ranged from 2.0 cm × 1.8 cm to 12 cm × 4.0 cm. All patients underwent repair using improved forearm venous flaps. The follow-up period ranged from 5 to 8 months. RESULTS: All flaps survived without serious complications. All patients were satisfied with the postoperative aesthetics and function of their hands. CONCLUSION: The improved forearm venous flap is a simple and reliable method for repairing hand electrical injuries.

An accessory head of the extensor indicis: a rare case report.

PURPOSE: A deep knowledge of the variations of the posterior forearm musculature is crucial for assessing and diagnosing conditions in this region. Extensor indicis (EI) is one of the muscles in this region, which exhibits diverse anatomical variations. This report documents an extremely unusual form of the EI with an accessory head on the dorsum of the hand. METHODS: During routine dissection, an extremely rare presentation of the EI was found in the left forearm of a 94-year-old female cadaver. RESULTS: This unusual EI consisted of two muscle bellies. The traditional belly originated from the distal two-thirds of the ulna. The muscle became tendinous around the carpal area, distal to the extensor retinaculum. The tendon was subsequently joined by an accessory muscle belly originating from the distal radioulnar ligament. The EI tendon inserted onto the dorsal expansion of the index finger, ulnar to that of the extensor digitorum. The posterior interosseous nerve innervated the muscle. CONCLUSION: Herein, we report an extremely rare form of the EI. To our knowledge, EI with an accessory head has only been reported rarely over the past 200 years. Moreover, our report appears to be the first case with photographic details of this anatomical variation. Clinicians should be aware of this variation for proper diagnosis and treatment.

The osteocutaneous radial forearm free flap: A multidisciplinary review of the evidence.

The osteocutaneous radial forearm (OCRFF) is a versatile free flap option for bony defects of the head and neck, given the thinness and pliability of the forearm cutaneous paddle, pedicle length, reliability, lack of atherosclerosis, and functional concerns common to other osseous donor sites. The OCRFF was once associated with a high risk of radial fracture, in addition to concerns about the quality and durability of bone stock for osseous reconstruction, particularly for the mandible. Following the introduction of prophylactic plating of the radius, the incidence of symptomatic radial fracture has drastically decreased. Furthermore, modifications of the bony osteotomies and other evolutions of this flap harvest have increased the use of the OCRFF throughout the head and neck. Despite these advantages, the OCRFF is not widely utilized by microvascular reconstructive surgeons due to perceived limitations and risks. Herein, we present a multidisciplinary, contemporary review of the harvest technique, outcomes, and perioperative management for the OCRFF.

Comparing online wrist and forearm EMG-based control using a rhythm game-inspired evaluation environment.

Objective.The use of electromyogram (EMG) signals recorded from the wrist is emerging as a desirable input modality for human-machine interaction (HMI). Although forearm-based EMG has been used for decades in prosthetics, there has been comparatively little prior work evaluating the performance of wrist-based control, especially in online, user-in-the-loop studies. Furthermore, despite different motivating use cases for wrist-based control, research has mostly adopted legacy prosthesis control evaluation frameworks.Approach.Gaining inspiration from rhythm games and the Schmidt's law speed-accuracy tradeoff, this work proposes a new temporally constrained evaluation environment with a linearly increasing difficulty to compare the online usability of wrist and forearm EMG. Compared to the more commonly used Fitts' Law-style testing, the proposed environment may offer different insights for emerging use cases of EMG as it decouples the machine learning algorithm's performance from proportional control, is easily generalizable to different gesture sets, and enables the extraction of a wide set of usability metrics that describe a users ability to successfully accomplish a task at a certain time with different levels of induced stress.Main results.The results suggest that wrist EMG-based control is comparable to that of forearm EMG when using traditional prosthesis control gestures and can even be better when using fine finger gestures. Additionally, the results suggest that as the difficulty of the environment increased, the online metrics and their correlation to the offline metrics decreased, highlighting the importance of evaluating myoelectric control in real-time evaluations over a range of difficulties.Significance.This work provides valuable insights into the future design and evaluation of myoelectric control systems for emerging HMI applications.