Lateral Femoral Condyle Allograft in the Treatment of Elbow Capitellar Avascular Necrosis: A Case Report.

CASE: A 27-year-old woman developed capitellar osteonecrosis after long-term corticosteroid use to treat non-Hodgkin lymphoma. She underwent an osteochondral reconstruction using a lateral femoral condyle (LFC) allograft. This graft was selected because it has a similar radius of curvature to the capitellum. The patient had osseous integration, painless, near full range of motion of her elbow 6 months postoperatively and good shoulder function 1.0 year postoperatively. CONCLUSION: The LFC allograft should be considered a viable option in treating capitellar osteonecrosis.

Two synergistic types of muscles were detected during forearm rotation exercise by T2 cumulative frequency curves using 0.2 T magnetic resonance imaging.

The purpose of this study was the detection and characterization of synergistic muscle activity. Using T2-map MRI, T2 values for 10 forearm muscles in 11 healthy adult volunteers were obtained in the resting state and after isotonic forearm supination and pronation exercises with the elbow extended. T2 was normalized by Z = (T2e-T2r)/SDr, where T2e was T2 after exercise, while T2r and SDr were the reference values of 34 ms and 3 ms, respectively. Using the cumulative frequency curves of Z values (CFZ), we detected 2 and 3 synergistic muscles for supination and pronation, respectively, and divided these into 2 types, one activated by exercise strength dependently, and the other, independent of exercise strength, activated by only a smaller fraction of the participants. We also detected co-contraction for the supination. Thus, CFZ is a useful visualization tool to detect and characterize not only synergistic muscle, but also co-contraction muscle.

Free flap reconstruction of elbow soft tissue defects: Lessons learned from 15 years of experience.

BACKGROUND: The elbow is a complex joint that is vital for proper function of the upper extremity. Reconstruction of soft tissue defects over the joint space remains challenging, and outcomes following free tissue transfer remain underreported in the literature. The purpose of this analysis was to evaluate the rate of limb salvage, joint function, and clinical complications following microvascular free flap coverage of the elbow. METHODS: This retrospective case series utilized surgical logs of the senior authors (Stephen J Kovach and L Scott Levin) to identify patients who underwent microvascular free flap elbow reconstruction between January 2007 and December 2021. Patient demographics and medical history were collected from the medical chart. Operative notes were reviewed to determine the type of flap procedure performed. The achievement of definitive soft tissue coverage, joint function, and limb salvage status at 1 year was determined from postoperative visit notes. RESULTS: Twenty-one patients (14 male, 7 female, median age 43) underwent free tissue transfer for coverage of soft tissue defects of the elbow. The most common indication for free tissue transfer was traumatic elbow fracture with soft tissue loss (n = 12, [57%]). Among the 21 free flaps performed, 71% (n = 15) were anterolateral thigh flaps, 14% (n = 3) were latissimus dorsi flaps, and 5% (n = 1) were transverse rectus abdominis flaps. The mean flap size was 107.5 cm2. Flap success was 100% (n = 21). The following postoperative wound complications were reported: surgical site infection (n = 1, [5%]); partial dehiscence (n = 5, [24%]); seroma (n = 2, [10%]); donor-site hematoma (n = 1, [5%]); and delayed wound healing (n = 5, [24%]). At 1 year, all 21 patients achieved limb salvage and definitive soft tissue coverage. Of the 17 patients with functional data available, 47% (n = 8) had regained at least 120 degrees of elbow flexion/extension. All patients had greater than 1 year of follow-up. CONCLUSION: Microvascular free flap reconstruction is a safe and effective method of providing definitive soft tissue coverage of elbow defects, as evidenced by high rates of limb salvage and functional recovery following reconstruction.

CT Arthrography of the Elbow: What Radiologists Should Know.

Computed tomography (CT) arthrography is a quickly available imaging modality to investigate elbow disorders. Its excellent spatial resolution enables the detection of subtle pathologic changes of intra-articular structures, which makes this technique extremely valuable in a joint with very tiny chondral layers and complex anatomy of articular capsule and ligaments. Radiation exposure has been widely decreased with the novel CT scanners, thereby increasing the indications of this examination. The main applications of CT arthrography of the elbow are the evaluation of capsule, ligaments, and osteochondral lesions in both the settings of acute trauma, degenerative changes, and chronic injury due to repeated microtrauma and overuse. In this review, we discuss the normal anatomic findings, technical tips for injection and image acquisition, and pathologic findings that can be encountered in CT arthrography of the elbow, shedding light on its role in the diagnosis and management of different orthopedic conditions. We aspire to offer a roadmap for the integration of elbow CT arthrography into routine clinical practice, fostering improved patient outcomes and a deeper understanding of elbow pathologies.

[Comparative study of external fixator combined with Kirschner wire fixation and Kirschner wires fixation in treatment of cubitus varus deformity in children].

Objective: To analyze the effectiveness comparison of external fixator combined with Kirschner wire fixation and Kirschner wire fixation in the treatment of cubitus varus deformity in children. Methods: A retrospective case-control study was conducted to collect 36 children of postoperative supracondylar humerus fracture complicating cubitus varus deformity between January 2018 and July 2022. Among them, 17 cases were treated with distal humeral wedge osteotomy external fixation combined with Kirschner wire fixation (observation group), and 19 cases were treated with distal humeral wedge osteotomy and Kirschner wire fixation (control group). The baseline data including age, gender, deformity side, time from fracture to operation, carrying angle of the healthy side and preoperative carrying angle of the affected side, elbow flexion and extension range of motion, and lateral condylar prominence index (LCPI) showed no significant difference between the two groups ( P>0.05). The operation time, hospitalization cost, healing time of osteotomy, postoperative complications, and the carrying angle, LCPI, and elbow flexion and extention range of motion were recorded and compared between the two groups. The elbow function was assessed by Oppenheim score at 3 months after operation and at last follow-up. Results: The children in both groups were followed up 13-48 months, with an average of 26.7 months. There was 1 case of needle tract infection in the observation group and 2 cases in the control group, and no nerve injury occurred, the difference in the incidence of complication (5.88% vs 10.53%) between the two groups was not significant ( χ 2=0.502, P=0.593). There was no significant difference in the operation time and fracture healing time between the two groups ( P>0.05); the hospitalization cost of the observation group was significantly higher than that of the control group ( P<0.05). The Oppenheim score of the observation group was significantly better than that of the control group at 3 months after operation ( P<0.05), but there was no significant difference in the Oppenheim score between the two groups at last follow-up ( P>0.05). At last follow-up, the carrying angle of affected side significantly improved in both groups when compared with preoperative ones ( P<0.05); the differences of the pre- and post-operative carrying angle of affected side and elbow flexion and extension range of motion showed no significant differences between the two groups ( P>0.05), but the difference in pre- and post-operative LCPI of the observation group was significantly better than that of the control group ( P<0.05). Conclusion: External fixator combined with Kirschner wire fixation and Kirschner wire fixation both can achieve satisfactory correction of cubitus varus deformity in children, and the former can achieve better short-term functional recovery of elbow joint and reduce the incidence of humeral lateral condyle protrusion.

Upper limb motor dysfunction is associated with fragmented kinetics after brain injury.

BACKGROUND: Characterization of motor deficits after brain injury is important for rehabilitation personalization. While studies reported abnormalities in the kinematics of paretic and non-paretic elbow extension for patients with brain injuries, kinematic analysis is not sufficient to explore how patients deal with musculoskeletal redundancy and the energetic aspect of movement execution. Conversely, interarticular coordination and movement kinetics can reflect patients' motor strategies. This study investigates motor strategies of paretic and non-paretic upper limb after brain injury to highlight motor deficits or compensation strategies. METHODS: 26 brain-injured hemiplegic patients and 24 healthy controls performed active elbow extensions in the horizontal plane, with both upper limbs for patients and, with the dominant upper limb for controls. Elbow and shoulder kinematics, interarticular coordination, net joint kinetics were quantified. FINDINGS: Results show alterations in kinematics, and a strong correlation between elbow and shoulder angles, as well as time to reach elbow and shoulder peak angular velocity in both upper limbs of patients. Net joint kinetics were lower for paretic limb and highlighted a fragmented motor strategy with increased number of transitions between concentric and eccentric phases. INTERPRETATION: In complement to kinematic results, our kinetic results confirmed patients' difficulties to manage both spatially and temporally the joint degrees of freedom redundancy but revealed a fragmented compensatory motor strategy allowing patients upper limb extension despite quality alteration and decrease in energy efficiency. Motor rehabilitation should improve the management of this fragmentation strategy to improve the performance and the efficiency of active movement after brain injury.

The efficacy of pediatric elbow radiographic guidance in diagnosis of lateral humeral condyle fracture.

Although lateral humeral condyle fracture is common, the incidence of missed diagnosis is very high. Delayed and missed diagnosis led to significant morbidities and loss of functions. We designed a pediatric elbow radiographic guidance aiming to improve the accuracy of diagnosis. This study was aimed to evaluate the efficacy of the radiographic guidance for the diagnosis of lateral condyle fracture. A cross-sectional study was conducted after defining the essential parameters as a guidance for assessing the pediatric elbow radiographs. We included medical students, emergency medicine, orthopedic, and radiology residents and fellows into this study. A questionnaire was used to evaluate the efficacy of the guidance. All participants underwent a pretest evaluation, followed by studying the guidance, and then finished a posttest evaluation. Baseline characteristics, diagnostic scores, and parameter evaluation scores were collected. The pretest and posttest scores were analyzed using paired t-test. Association between baseline characteristics and diagnostic scores were analyzed using multiple regression analysis. We included 177 participants. Average diagnostic score was significantly increased after using the guidance, from 12.2 ± 1.9 to 13.0 ± 1.7 (p < 0.0001). Medical students showed the most improvement, from 11.9 ± 1.9 to 13.1 ± 1.3 (p <0.001). All means of essential parameter evaluation scores were significantly improved in overall participants.The pediatric elbow radiographic guidance is useful for evaluation and diagnosis of lateral condyle fracture, especially for young physicians and trainees. Therefore, this should be recommended in routine medical education and general practice.

[A multicenter clinical study on the treatment of lateral epicondylitis of humerus by manipulation].

OBJECTIVE: To investigate clinical effect of tendons pulling,poking and kneading for the treatment of external humeral epicondylitis. METHODS: From January 2018 to December 2021,a multicenter randomized controlled study was performed to collect 192 patients with external humeral epicondylitis in Wangjing Hospital,Beijing Dianli Hospital,and Beijing Fengsheng Osteotraumatology Hospital,respectively,and they were divided into treatment group and control group by random number table method. There were 96 patients in treatment group,including 36 males and 60 females,aged from 28 to 60 years old with an average of (41.20±5.50) years old;the course of disease ranged from 1 to 14 days with an average of (5.24±1.35) days;they were treated once every other day for 2 weeks. There were 96 patients in control group ,including 33 males and 63 females,aged from 26 to 60 years old with an average of (43.35±7.75) years old;the course of disease ranged from 1 to 14 days with an average of (5.86±1.48) days;they were treated with topical voltaalin combined with elbow joint fixation for 2 weeks. Visual analogue scale (VAS) and Hospital for Surgery Scoring System (HSS) elbow pronation and supination angles,wrist metacarpal flexion and dorsal extension angles,elbow tenderness between two groups were compared before treatment and at 1,3,5,7,11 and 13 days after treatment;Hospital for Surgery Scoring System 2 (HSS2) was compared before treatment and the final treatment. RESULTS: All patients were followed up for 10 to 14 days with an average of (12±1.6) days. VAS between treatment group and control group before treatment were 6.83±1.36 and 6.79±1.58,respectively,and decreased to 1.49±1.09 and 2.11±1.81 after the final treatment. VAS of treatment group were significantly lower than those of control group at 1,3,5,7,9,11 and 13 days after treatment (P<0.05). HSS between two groups were 61.73±11.00 and 36.47±12.45 before treatment,respectively,and increased to 94.42±5.9 and 91.44±9.11 at the final treatment. HSS of treatment group were significantly higher than those of control group at 1,3,5,7,9,11 and 13 days after treatment (P<0.05). On the 5th day after treatment,the external and internal rotation angles of elbow in treatment group were (66.41±12.69) ° and (66.35±13.54) °,while those in control group were (62.08±16.03) ° and (61.77±16.35) °. On the 7th day after treatment,the external and internal rotation angles of elbow were (69.79±12.64) ° and (70.02±13.55) ° in treatment group,and (65.28±15.86) ° and (65.09±16.67) ° in control group. Elbow joint motion in treatment group was higher than that in control group (P<0.05). On the 5th day after treatment,angles of wrist dorsiflexion and palm flexion were (39.43±15.94) ° and (46.68±11.10) ° in treatment group,and (38.51±18.49) ° and (44.27±13.58) ° in control group. On the 7th day after treatment,angles of wrist dorsiflexion and palm flexion were (42.52±16.50) ° and (49.23±10.96) ° in treatment group,and (41.18±20.09) ° and (46.64±14.63) ° in control group. The motion of wrist joint in treatment group was higher than that in control group (P<0.05). On the 13th day after treatment,HSS2 in treatment group 93.61±6.32 were higher than those in control group 92.06±7.94(P<0.05). There was no significant difference in elbow tenderness between two groups at each time point (P>0.05). CONCLUSION: Voltaren external treatment combined with elbow fixation and tendons pulling,poking and kneading could effectively improve symptoms of external humeral epicondylitis. Compared with voltaren external treatment,tendons pulling,poking and kneading has advantages of longer analgesic time and better elbow function recovery.

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).

Total Elbow Arthroplasty Historical and Current Concepts.

The evolution of total elbow arthroplasty (TEA) has laid the groundwork for modern day TEA and has contributed to our understanding of elbow biomechanics. Trends in the usage of TEA have also varied significantly over time. This article aims to review the history and evolution of the TEA implant with a focus on modern day implant biomechanics and the trends in TEA indications. Additionally, this review discusses various complications that can occur with modern day TEA and looks toward the future to identify innovation and future trends.

Impact of motor task conditions on end-point kinematics and trunk movements during goal-directed arm reach.

Task conditions significantly impact human motor control. We investigated how task type, difficulty, and constraints influence the kinematics of goal-directed arm reaching. Non-disabled young adults performed two distinct goal-directed arm reaching tasks: pointing and picking up an object with chopsticks. These tasks were carried out under various conditions, including constrained and unconstrained elbow extension and two different task difficulties. We collected kinematic data using a 3-D motion capture system and analyzed the effects of different task conditions on kinematic variables using linear mixed-effects regression analysis. Our findings revealed statistically significant differences in kinematics between the two tasks. Arm reaching during the picking-up task was slower and exhibited jerkier movements compared to the pointing task. Additionally, when arm reaching was performed with constrained elbow extension, it led to slower and jerkier movements, with an increased involvement of trunk movements compared to the unconstrained condition. These findings show that complex manipulative motor tasks requiring higher hand dexterity necessitate feedback-based control of arm reaching, but simple pointing tasks requiring less hand dexterity do not. In conclusion, our study sheds light on the influence of task conditions on goal-directed arm reaching kinematics and provides valuable insights into the motor control strategies involved in different tasks.

Understanding the capacity of children with congenital unilateral below-elbow deficiency to actuate their affected muscles.

In recent years, commercially available dexterous upper limb prostheses for children have begun to emerge. These devices derive control signals from surface electromyography (measure of affected muscle electrical activity, sEMG) to drive a variety of grasping motions. However, the ability for children with congenital upper limb deficiency to actuate their affected muscles to achieve naturalistic prosthetic control is not well understood, as compared to adults or children with acquired hand loss. To address this gap, we collected sEMG data from 9 congenital one-handed participants ages 8-20 years as they envisioned and attempted to perform 10 different movements with their missing hands. Seven sEMG electrodes were adhered circumferentially around the participant's affected and unaffected limbs and participants mirrored the attempted missing hand motions with their intact side. To analyze the collected sEMG data, we used time and frequency domain analyses. We found that for the majority of participants, attempted hand movements produced detectable and consistent muscle activity, and the capacity to achieve this was not dissimilar across the affected and unaffected sides. These data suggest that children with congenital hand absence retain a degree of control over their affected muscles, which has important implications for translating and refining advanced prosthetic control technologies for children.

The Septic Elbow Joint: Treatment Approaches for Improved Patient Outcomes.

Septic arthritis of the elbow is a serious problem requiring prompt, accurate diagnosis and urgent surgical intervention. Achieving successful patient outcomes depends heavily on early diagnosis and efficient streamlined surgical treatment. Essential tactics for treating the septic elbow joint include immediate joint irrigation and debridement in addition to administration of appropriate antibiotics. This comprehensive review delves into the cause of the septic elbow joint, identifies associated risk factors, and provides a comprehensive approach encompassing the diagnosis and treatment of the septic elbow. The aim of this review is to optimize patient care and outcomes.

Reconstruction of the elbow with distal humerus endoprosthetic replacement after tumor resection: a systematic review of the literature and institutional case series.

BACKGROUND: Distal humerus replacement (DHR) is a modular endoprosthesis mainly used for bone reconstruction after resection of primary or metastatic bone lesions. Studies on DHR failure rates and postoperative functional outcomes are scarce. We sought to assess implant survival, modes of failure, and functional outcomes in patients undergoing DHR for oncologic indications. METHODS: A systematic review of the PubMed and Embase databases was performed. PRISMA guidelines were followed for this manuscript. Our study was registered on PROSPERO (457,260). Quality appraisal of included studies was conducted using the STROBE checklist. Prosthetic failure was assessed using the Henderson classification for megaprosthetic failures. We additionally performed a retrospective review of patients treated with a DHR for oncologic indications at a large tertiary care academic center. Weighted means were calculated to pool data. RESULTS: Eleven studies with a total of 162 patients met the inclusion criteria. Mean follow-up was 3.7 years (range, 1.66-8 years). Henderson type 2 failures (aseptic loosening) were the most common mode of failure, occurring in 12% of cases (range, 0%-33%). Five-year implant survival was 72% (range, 49%-93.7%). Mean postoperative Musculoskeletal Tumor Society (MSTS) score was 81.1 (range, 74-84.3). In our institutional case series, 2 out of 5 patients had DHR revision for periprosthetic fracture and aseptic loosening at 16 and 27 months after surgery, respectively. CONCLUSIONS: Distal humerus replacement is a successful reconstruction strategy for tumors of the distal humerus, with high implant survival and good to excellent functional outcomes.

The enigmatic os supratrochleare anterius: from rarity to recognition in elbow pathology-case report and review of literature.

Accessory bones around the elbow are scarce, with a reported mean incidence rate of 0.77%. The rarest one is the os supratrochleare anterius, with only a handful of documented cases in the literature. Despite their scarcity, various types of ossicles have been documented, posing diagnostic challenges and potential misinterpretation on X-rays. Herein, we report a case of an accidentally found os supratrochleare anterius in a 43-year-old pig farmer presenting with symptoms of tennis elbow. After conservative treatment with nonsteroidal anti-inflammatory drugs and physiotherapy, he made a full recovery within 2 weeks. This report emphasizes the rarity of the ossupra trochleare anterius, the importance of accurate diagnosis, and the need for continued research and awareness of this anatomical variation.

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.

The Utility of Stress Ultrasound in Identifying Risk Factors for Elbow Ulnar Collateral Ligament Tear: A Longitudinal Study of 203 Professional Baseball Players.

BACKGROUND: Injuries to the medial ulnar collateral ligament (UCL) are common among baseball pitchers due to repetitive stress on the soft tissue stabilizers of the elbow during pitching. Dynamic stress ultrasound (SUS) can be used to evaluate the UCL and ulnohumeral joint to identify anatomic risk factors of those who will require UCL reconstruction (UCLR). PURPOSE: To determine whether any adaptive or morphological changes detectable on SUS can predict injury to the UCL in professional baseball pitchers. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: A total of 203 professional baseball pitchers who underwent SUS at preseason training sessions over the course of 18 years were categorized into 1 of 2 groups: those without a history of shoulder, arm, elbow, or forearm surgery or injuries (healthy cohort; n = 184) and those who underwent UCLR the same season as SUS (UCLR cohort; n = 19). Ligament thickness, joint spacing, and laxity were compared. An additional matched cohort analysis was conducted using 10 players from each group to detect differences in the progression of UCL and ulnohumeral joint measures in the year before injury. RESULTS: The UCLR cohort, when compared with the healthy cohort, had higher relative (ie, nondominant-side measurements subtracted from dominant-side measurements) resting ulnohumeral joint space (median, 0.50 vs 0.20 mm, respectively; P = .006) and higher rates of hypoechoic foci (57.9% vs 30.4%, respectively; P = .030). Players of both groups had similar dominant UCL thickness (P = .161), ulnohumeral joint space at rest (P = .321), space under stress (P = .498), and laxity (P = .796). Groups did not differ in terms of relative UCL thickness, ulnohumeral joint space under stress, or relative laxity. In the year before UCL injury, the UCLR cohort, compared with the matched healthy cohort, had a greater increase in mean dominant UCL thickness (0.94 vs -0.60 mm, respectively; P = .038) and a greater increase in relative median UCL thickness (1.35 vs -0.35 mm, respectively; P = .045). Players in the healthy cohort were statistically older than those in the UCLR cohort (23 vs 22 years, respectively; P = .004). No differences in ulnohumeral stress spacing or laxity were detected. CONCLUSION: SUS of players who underwent UCLR demonstrated a progressive increase in UCL thickness over 1 year, higher rates of hypoechoic foci, and increased ulnohumeral rest space compared with SUS of uninjured players.

Rotational Motion Due to Skin Shear Deformation at Wrist and Elbow.

The hanger reflex is an illusion phenomenon that induces strong force perception and rotational motion, and it occurs in multiple parts of the body. A potential application of this phenomenon is in upper limb rehabilitation for patients with upper-limb paralysis involving arm rotation. However, the only upper limb movements that have been confirmed in this phenomenon are the inward and outward movements of the wrist, which limits the applicable tasks. Therefore, we attempted to apply the hanger reflex to the elbow and use it simultaneously with the wrist. This phenomenon occurs due to shear deformation of the skin, so shear deformation was presented to the skin on the elbow. When shear deformation of the skin was presented to the elbow in the same manner as in previous studies applied to the wrist, movement and force perception of pronation and supination of the elbow were confirmed. The results of an experiment in which the hanger reflex was simultaneously presented to the elbow and wrist showed that each region independently perceived motion and force.

Evaluation of generic EMG-Torque models across two Upper-Limb joints.

Advanced single-use dynamic EMG-torque models require burdensome subject-specific calibration contractions and have historically been assumed to produce lower error than generic models (i.e., models that are identical across subjects and muscles). To investigate this assumption, we studied generic one degree of freedom (DoF) models derived from the ensemble median of subject-specific models, evaluated across subject, DoF and joint. We used elbow (N = 64) and hand-wrist (N = 9) datasets. Subject-specific elbow models performed statistically better [5.79 ± 1.89 %MVT (maximum voluntary torque) error] than generic elbow models (6.21 ± 1.85 %MVT error). However, there were no statistical differences between subject-specific vs. generic models within each hand-wrist DoF. Next, we evaluated generic models across joints. The best hand-wrist generic model had errors of 6.29 ± 1.85 %MVT when applied to the elbow. The elbow generic model had errors of 7.04 ± 2.29 %MVT when applied to the hand-wrist. The generic elbow model was statistically better in both joints, compared to the generic hand-wrist model. Finally, we tested Butterworth filter models (a simpler generic model), finding no statistical differences between optimum Butterworth and subject-specific models. Overall, generic models simplified EMG-torque training without substantive performance degradation and provided the possibility of transfer learning between joints.