Elbow torques and EMG patterns of flexor muscles during different isometric tasks.

This paper examines the torque responses and EMG activity levels in four muscles acting at the elbow joint during different combinations of one- and two- degree of freedom isometric torque production (single and dual tasks, respectively). Flexor and supinator/pronator torques and surface EMG signals from m. biceps brachii, m. brachialis, m. brachioradialis and m. triceps brachii were measured in 16 male subjects while they performed maximal effort isometric contractions of pure flexion, pure supination, pure pronation, combined flexion and supination and combined flexion and pronation. In the single tasks, the torque responses were consistent with task requirements, but the dual task results were surprising in that flexor torque levels were reduced as compared to pure flexion, while supinator/pronator torque levels were as high or higher than in pure supination or pronation. Muscle activity levels varied with task, and could not always explain the differences observed in torque responses. These data are discussed within the framework of subpopulations of task-specific motor units within each muscle. The implications of such task-specific muscle units are related to musculoskeletal modelling and previous EMG - torque relationships found at the elbow.     

Electromyographic study of the flexor muscles of the elbow articulation in weightlifting trained subjects

The purpose of this work was to register the electromyography data of the muscles brachialis, biceps brachii long portion, biceps brachii short portion and brachioradialis in the movements of elbow flexion, in the "Larry Scott" bench, in supination and pronation positions, in weightlifting trained subjects. Ten male right-handed subjects were selected, with at least one-year experience in weightlifting exercises, without previous neuromuscular diseases, age between 21 and 26 years. After taking the "Maximum Load" (M.L.) test, or a maximum repetition, we had the percent pattern to establish the loads used in the tests, which was 80%0 of the M. L. For the electromyography records was used a six-channel electromyography (lynx) and the AqDados software in four different moments for each subject: an isometric phase lasting five seconds in supination (1), keeping a 90 degrees angle between the arm and forearm; another one in isometric pronation (2); ten repetitions lasting fifty seconds in supination (3); and ten repetitions in pronation (4). The results of the normalization showed a level of similar activation between the involved muscles in one same moment, as much in supination as in pronation. From the analysis of variance ANOVA, having as level of significance p < 0,05, concludes that it did not have significant difference in the performance of these muscles. When compared between itself all the values of p were bigger than 0,05. Of this form we can perceive a joint action of all the flexion muscle of the elbow to resist the load imposed during the effort.     

Strategies for muscle activation during isometric torque generation at the human elbow

1. We studied the patterns of electromyographic (EMG) activity in elbow muscles of 14 normal human subjects. The activity of five muscles that act in flexion-extension and forearm supination-pronation was simultaneously recorded during isometric voluntary torque generation, in which torques generated in a plane orthogonal to the long axis of the forearm were voluntarily coupled with torques generated about the long axis of the forearm (i.e., supination-pronation). 2. When forearm supination torques were superimposed on a background of elbow flexion torque, biceps brachii activity increased substantially, as expected; however, brachioradialis and brachialis EMG levels decreased modestly, a less predictable outcome. The pronator teres was also active during pure flexion and flexion coupled with mild supination (even though no pronation torque was required). This was presumably to offset inappropriate torque contributions of other muscles, such as the biceps brachii. 3. When forearm supination torque was superimposed on elbow extension torque, again the biceps brachii was strongly active. The pronator teres also became mildly active during extension with added pronation torque. These changes occurred despite the fact that both the pronator and biceps muscles induce elbow flexion. 4. In these same elbow extension tasks, triceps brachii activity was also modulated with both pronation or supination loads. It was most active during either supination or pronation loads, again despite the fact that it has no mechanical role in producing forearm supination-pronation torque. 5. Recordings of EMG activity during changes in forearm supination-pronation angle demonstrated that activation of the biceps brachii followed classic length-tension predictions, in that less EMG activity was required to achieve a given supination torque when the forearm was pronated (where biceps brachii is relatively longer). On the other hand, EMG activity of the pronator teres did not decrease when the pronator was lengthened. Triceps EMG was also more active when the forearm was supinated, despite its having no direct functional role in this movement. 6. Plots relating EMG activity in biceps brachii, brachialis, and brachioradialis at three different forearm positions revealed that there was a consistent positive near-linear relationship between brachialis and brachioradialis and that biceps brachii is often most active when brachioradialis and brachialis are least active. 7. We argue that, for the human elbow joint at least, fixed muscle synergies are rather uncommon and that relationships between muscle activities are situation dependent.(ABSTRACT TRUNCATED AT 400 WORDS)     

Transfer of resistance training to enhance rapid coordinated force production by older adults

The purpose of this study was to examine the capacity of resistance training to enhance the rapid and coordinated production of force by older people. Thirty adults (60 years) completed a visually guided aiming task that required the generation of isometric torque in 2 df about the elbow prior to and following a 4-week training period. Groups of six participants were allocated to two progressive (40–100% maximal voluntary contraction (MVC)) resistance-training (PRT) groups, to two constant low-load (10% MVC) training groups (CLO) and to one no-training control group. Training movements required the generation of either combined flexion and supination (FLESUP), or combined extension and supination (EXTSUP). In response to training, target acquisition times in the aiming task decreased for all groups; however, both the nature of the training load and the training movement influenced the pattern and magnitude of improvements (EXTSUP_CLO: 36%, FLESUP_PRT 26%, EXTSUP_PRT 22%, FLESUP_CLO 20%, CONTROL 15%). For one group that trained with progressively increasing loads, there arose a subsequent decrease in performance in one condition of the transfer task. For each group, these adaptations were accompanied by systematic changes in the coordination of muscles about the elbow joint, particularly the biceps brachii.Abbreviations MVC maximal voluntary contraction - EMG electromyography - PRT progressive resistance training - CLO constant low-load training - FLESUP flexion plus supination - EXTSUP extension plus supination - FLEPRO flexion plus pronation - EXTPRO extension plus pronation - FLEX flexion - SUPN supination - EXTD extension - PRON pronation - RMS root mean square     

Coordination and inhomogeneous activation of human arm muscles during isometric torques

1. In this study we have recorded the activity of motor units of the important muscles acting across the elbow joint during combinations of voluntary isometric torques in flexion/extension direction and supination/pronation direction at different angles of the elbow joint. 2. Most muscles are not activated homogeneously; instead the population of motor units of muscles can be subdivided into several subpopulations. Inhomogeneous activation of the population of motor units in a muscle is a general finding and is not restricted to some multifunctional muscles. 3. Muscles can be activated even if their mechanical action does not contribute directly to the external torque. For example, m. triceps is activated during supination torques and thus compensates for the flexion component of the m. biceps. On the other hand, motor units in muscles are not necessarily activated if their mechanical action contributes to a prescribed torque. For example, there are motor units in the m. biceps that are activated during flexion torques, but not during supination torques. 4. The relative activation of the muscles depends on the elbow angle. Changing the elbow angle affects the mechanical advantage of different muscles differently. In general, muscles with the larger mechanical advantage receive the larger input. 5. We have calculated the relative contributions of some muscles to isometric torques. These contributions depend on the combination of the torques exerted. 6. Existing theoretical models on muscle coordination do not incorporate subpopulations of motor units and therefore need to be amended.     

Electrophysiological studies of muscles in the human upper limb: The biceps brachii

The biceps brachii (BB) belongs to elbow flexors. However, because the BB acts not only as the flexor, but also as a forearm supinator in humans, its activities are much different from those of the other flexors (the brachialis and brachioradialis: BR and BRR, respectively). The present paper describes unique characteristics of the BB that emerged from recent studies using electrophysiological techniques (i.e. electromyography (EMG), electrical neuromuscular stimulation (ENS), Hoffmann (H)-reflex and post-stimulus time-histogram (PSTH)) in normal human subjects. The EMG studies have shown reciprocal contractions between the BB and the other flexors during forearm pronation/supination movements. Comparisons of EMG activities of the flexors between the pronated and supinated positions of the forearm have indicated clear differences of contraction properties between the BB and the other flexors. The ENS studies have shown that reciprocal activation between the BB and BRR following stimulation can produce a motion of supination with maintenance of flexion. This finding supports the theory that the reciprocal contractions should occur to keep constant force in flexion for supporting weight below the elbow. Studies using H-reflex and PSTH techniques have shown neural connections, which are spinal reflex arcs modulating motoneuron excitabilities with excitatory and inhibitory inputs from low-threshold muscle afferent fibers, among muscles in the human upper limb. These studies have demonstrated inhibitory neural connections between the BB and BRR. Moreover it has been shown that the connections concerning the BB differ from those concerning the BRR. Several reports have shown differences in connections between humans and animals. Therefore, the BB in humans has been compared with that in animals.     

Cocontraction of the elbow muscles during combined tasks of pronation-flexion and supination-flexion.

The aim of this study was to determine if the antagonist activity of the triceps brachii (TB) and anconeus (AN) muscles is modulated when the activity of the biceps brachii (BB) and brachioradialis (BR) is modulated by the performance of combined tasks and to verify if this behavior is similar at different elbow angles. Electromyographic (EMG) activity of BB, BR, AN and TB was recorded for normal subjects (N = 6) with surface electrodes during a ramp isometric contraction in elbow flexion (F) which was performed alone or combined with 20% of maximal voluntary contraction (MVC) in pronation (P) or in supination (S). Two cocontraction ratios, using the EMG root mean square (rms) values of each muscle and identified as BB/TB and BR/AN were calculated. The results indicate that for low flexion torque levels, the BB/TB ratio is higher for the S-F condition while the BR/AN ratio is higher during the pure flexion task. Variations of the EMG activity across tasks were significant only for BB (Friedman ANOVA, p less than .01) whereas there was no significant change in EMG activity (rms) for TB, BR and AN (Friedman ANOVA, p greater than .01). Furthermore, the behavior of both ratios across tasks was similar at 50 degrees, 90 degrees and 130 degrees of elbow flexion. Thus, for isometric conditions, there appears to be no evidence of modulation of EMG activity of elbow extensors while performing combined tasks of S-F and P-F. In addition, cocontraction activity during these tasks tends to be similar across elbow angles.     

Analysis of double-joint movements in controls and in parkinsonian patients

The motor performance of seven patients with Parkinson’s disease and seven control subjects was tested in a choice reaction aiming task. The subjects were instructed to aim as fast and as accurately as possible to a light stimulus, which defined one of eight possible target positions. In order to reach the targets, elbow flexions had to be combined with forearm supinations or with forearm pronations. For single-joint movements, forearm supinations or pronations were executed faster than the long elbow flexions in both groups. In the double-joint movements of the control group, the flexion movement times (flex.MTs) and the supination movement times (sup.MTs) or pronation movement times (pron.MTs) were similar to the MTs of the corresponding single-joint movements. MTs of parkinsonian patients were significantly longer than those of control subjects. MTs were most increased in the forearm supination and forearm pronation of double-joint movements. In contrast to the controls, sup.MT and pron.MT were significantly increased in double-joint movements as compared to single-joint movements. The variations in the flex.MT and sup.MT of the double-joint movements neither correlated for a control subject nor for a parkinsonian patient. For controls, the independent MTs in double-joint movements cannot be explained by minimal principles (minimum energy, minimal torque change), but suggest that two separate motor programs are superimposed. In Parkinson’s disease, there seems to be a deficit in superimposing two separate motor programs. Received: 20 May 1996 / Accepted: 8 July 1997     

Cathodal transcranial direct current stimulation of the primary motor cortex improves selective muscle activation in the ipsilateral arm

Proximal upper limb muscles are represented bilaterally in primary motor cortex. Goal-directed upper limb movement requires precise control of proximal and distal agonist and antagonist muscles. Failure to suppress antagonist muscles can lead to abnormal movement patterns, such as those commonly experienced in the proximal upper limb after stroke. We examined whether noninvasive brain stimulation of primary motor cortex could be used to improve selective control of the ipsilateral proximal upper limb. Thirteen healthy participants performed isometric left elbow flexion by contracting biceps brachii (BB; agonist) and left forearm pronation (BB antagonist) before and after 20 min of cathodal transcranial direct current stimulation (c-tDCS) or sham tDCS of left M1. During the tasks, motor evoked potentials (MEPs) in left BB were acquired using single-pulse transcranial magnetic stimulation of right M1 150-270 ms before muscle contraction. As expected, left BB MEPs were facilitated before flexion and suppressed before pronation. After c-tDCS, left BB MEP amplitudes were reduced compared with sham stimulation, before pronation but not flexion, indicating that c-tDCS enhanced selective muscle activation of the ipsilateral BB in a task-specific manner. The potential for c-tDCS to improve BB antagonist control correlated with BB MEP amplitude for pronation relative to flexion, expressed as a selectivity ratio. This is the first demonstration that selective muscle activation in the proximal upper limb can be improved after c-tDCS of ipsilateral M1 and that the benefits of c-tDCS for selective muscle activation may be most effective in cases where activation strategies are already suboptimal. These findings may have relevance for the use of tDCS in rehabilitation after stroke.     

Estimation of elbow flexion force during isometric muscle contraction from mechanomyography and electromyography

Mechanomyography (MMG) is the muscle surface oscillations that are generated by the dimensional change of the contracting muscle fibers. Because MMG reflects the number of recruited motor units and their firing rates, just as electromyography (EMG) is influenced by these two factors, it can be used to estimate the force exerted by skeletal muscles. The aim of this study was to demonstrate the feasibility of MMG for estimating the elbow flexion force at the wrist under an isometric contraction by using an artificial neural network in comparison with EMG. We performed experiments with five subjects, and the force at the wrist and the MMG from the contributing muscles were recorded. It was found that MMG could be utilized to accurately estimate the isometric elbow flexion force based on the values of the normalized root mean square error (NRMSE = 0.131 ± 0.018) and the cross-correlation coefficient (CORR = 0.892 ± 0.033). Although MMG can be influenced by the physical milieu/morphology of the muscle and EMG performed better than MMG, these experimental results suggest that MMG has the potential to estimate muscle forces. These experimental results also demonstrated that MMG in combination with EMG resulted in better performance estimation in comparison with EMG or MMG alone, indicating that a combination of MMG and EMG signals could be used to provide complimentary information on muscle contraction.     

Erratum to: Estimation of elbow flexion force during isometric muscle contraction from mechanomyography and electromyography

Mechanomyography (MMG) is the muscle surface oscillations that are generated by the dimensional change of the contracting muscle fibers. Because MMG reflects the number of recruited motor units and their firing rates, just as electromyography (EMG) is influenced by these two factors, it can be used to estimate the force exerted by skeletal muscles. The aim of this study was to demonstrate the feasibility of MMG for estimating the elbow flexion force at the wrist under an isometric contraction by using an artificial neural network in comparison with EMG. We performed experiments with five subjects, and the force at the wrist and the MMG from the contributing muscles were recorded. It was found that MMG could be utilized to accurately estimate the isometric elbow flexion force based on the values of the normalized root mean square error (NRMSE = 0.131 ± 0.018) and the cross-correlation coefficient (CORR = 0.892 ± 0.033). Although MMG can be influenced by the physical milieu/morphology of the muscle and EMG performed better than MMG, these experimental results suggest that MMG has the potential to estimate muscle forces. These experimental results also demonstrated that MMG in combination with EMG resulted in better performance estimation in comparison with EMG or MMG alone, indicating that a combination of MMG and EMG signals could be used to provide complimentary information on muscle contraction.     

Error rate in five-state myoelectric control systems

A myoelectric control system is one in which the operation of a device is controlled by the electric potential produced by voluntary contraction of a muscle. The utilisation of a single muscle site for the 3-state control of a myoelectric prosthesis has proven beneficial for certain amputees. It has been proposed that a single muscle site could be used for 5-state control, perhaps for an elbow and hand. This paper presents a preliminary study of the error probability for 5-state control.     

Movements of the elbow and shoulder during pronation of the forearm

It is known that medial and lateral movements of the lower end of the ulna occur during pronation and supination of the forearm, but there is little clear evidence as to where these movements originate. Twenty normal subjects pronated their forearm about either an undefined, lateral, or medial axis. Measurements were made from paired photographs taken at increments of 45° during the movement. Abduction of the ulna always occurred but its magnitude did not vary significantly with differing axes of pronation. During pronation about an undefined axis the abduction at the elbow produced a lateral movement of the ulna which was usually appropriate for the axis of pronation in use. Medial or lateral rotation of the humerus was used to increase or decrease the amount of lateral movement of the lower end of the ulna to suit the requirements of pronation about a medial or lateral axis.     

Force synchrony enhances the stability of rhythmic multi-joint arm coordination

Although rhythmic coordination has been extensively studied in the literature, questions remain about the correspondence of constraints that have been identified in the related contexts of inter-limb and intra-limb coordination. Here we used a 2-DOF robot arm which allows flexible manipulation of forces to investigate the effect on coordination stability of intra-limb coordination of: (i) the synchrony of force requirements and (ii) the involvement of bi-functional muscles. Ten subjects produced simultaneous rhythmic flexion–extension (FE) and supination-pronation (SP) elbow movements in two coordination patterns: (1) flexion synchronized with supination/extension with pronation (in-phase pattern) and (2) flexion synchronized with pronation/extension with supination (anti-phase pattern). The movements were produced with five different settings of the robot arm: a neutral setting that imposed balanced force requirements, and four other settings that increased the force requirements for one direction in both DOF. When combined with specific coordination patterns, these settings created conditions in which either synchronous or alternate patterns of forcing were necessary to perform the task. Results showed that synchronous tasks were more stable than asynchronous tasks (P < 0.05). Within the synchronous tasks, some robot settings were designed to either increase or decrease the use of bi-functional muscles. Although there was no difference for the bi-functional muscle biceps brachii, the coordination was more stable for the condition in which the greatest force requirements corresponded to the mechanical action of the bi-functional pronator teres (P < 0.05). In conclusion, force synchrony increases the stability of rhythmic intra-limb coordination, but further research is needed to clarify the role of bi-functional muscles in this effect.     

The Radioulnar Distance at the Level of the Radial Tuberosity

Ruptures of the distal biceps brachii tendon are generally treated operatively due to their loss of supination and flexion force. A mechanical impingement at the insertion of the tendon at the radial tuberosity is discussed to play a role in the etiology of this injury. The aim of this study was to present a detailed, three-dimensional anatomical analysis of the radioulnar space at the radial tuberosity. A total of 166 imprints of the radioulnar space in neutral rotation and pronation from 84 cadaveric specimens of both arms using silicone impression material were produced for this study. Imprints were cut in slices of 3 mm and digitally measured after picture acquisition using a high-resolution digital camera. Distances were grouped into a proximal, central, and distal groups and used for correlation to morphometric data at the elbow (radial head diameter, ulna and radius length) as well as volume calculation. The mean radioulnar distance was 8.8 ± 4.0 mm in neutral rotation and 7.8 ± 3.9 mm in pronation. In pronation, the central zone was the smallest whereas in neutral rotation the proximal zone was the smallest. The volume of the radioulnar space did not reduce significantly during pronation. Little space is provided for the insertion of the distal biceps brachii tendon especially during pronation. This could play a role in the etiology of distal biceps brachii tendon ruptures and should be considered in the fixation after rupture of the tendon. Clin. Anat., 33:661–666, 2020. © 2019 Wiley Periodicals, Inc.     

Coordination of arm muscles during flexion and supination: application of the tensor analysis approach

In order to obtain a good understanding of the coordination of the motor system several problems have to be solved. Two major issues are: (1) that muscles do not form an orthogonal coordinate system, and (2) that the number of muscles that may contribute to a movement in general exceeds the number of degrees of freedom of the movement. The latter allows the movement to be executed by an infinite variety of muscle activations. A theoretical solution to these problems has been elaborated by Pellionisz and Llinás. However, convincing experimental support for this theory is still lacking. In this paper the theory has been applied to the activation of arm muscles which contribute to flexion/extension and supination/pronation of the arm. Motor unit activity was recorded with fine wire electrodes. As reported in previous papers, the recruitment threshold of motor units in arm muscles during isometric contraction depends on a combination of forces in flexion and supination directions. This dependence is characteristic for motor units in a single muscle, but is very different for motor units in different muscles. The theoretical results are in good agreement with the behavior of the recruitment threshold for flexion, which decreases (such as m. biceps brachii), or increases (such as for m. brachialis and m. brachioradialis) with force in supination direction. The theory also correctly predicts how the recruitment threshold for motor units changes as a function of the angle between forearm and upper arm. These results give firm support to the hypothesis that the central nervous system uses a tensorial approach for the activation of the motor system, as originally proposed by Pellionisz and Llinás.     

Amplitude and frequency measures of surface electromyography during dual task elbow torque production

Summary Studies of motor unit recruitment thresholds have demonstrated the existence of task-specific motor units within the muscles controlling the elbow. Two degree-of-freedom (df) task specificity was investigated at higher levels of elbow torque using the amplitude and frequency characteristics of surface electromyography (EMG). Flexion and supination torque data were collected together with EMG from electrode pairs on the brachioradialis (BRAD), biceps brachii short head, and medial and lateral aspects of biceps brachii long head, while subjects (n=14) performed the following four combinations of isometric tasks: (1) maximum voluntary contraction (MVC) flexion (F) and (2) MVC supination (S), each with a targeted torque of zero in the second d f; (3) MVC flexion with targeted MVC supination (FS); and (4) MVC supination with targeted MVC flexion (SF). Median power frequency (MEDF) and root mean square (RMS) amplitude under steady-state torque conditions were calculated and analyzed using ANCOVA models with planned contrasts (=0.05). A significant main effect for task was found in RMS, but not in MEDF. Contrasts showed a significant increase in RMS response in the dual MVC tasks (FS and SF) over the single MVC tasks of F and S. The lack of frequency changes with alterations in RMS data indicates that the underlying recruitment/rate coding scheme in use for dual-d f tasks may be different than in single-d f tasks, and provides possible support for the notion of motor unit task groups. Task-by-site interactions were found for both MEDF and RMS, and illustrated that the three biceps sites differed from BRAD in their responses to the F versus S tasks. These results provide further support that the synergy between biceps and BRAD is not fixed, and that the concept of flexor equivalence at the elbow does not hold under all torque task conditions     

Extensor carpi radialis brevis origin,nerve supply and its role in lateral epicondylitis

Lateral epicondylitis (LE) or tennis elbow has been the subject of concern during the last 60 years, but the pathogenesis of the LE remains unclear. The LE can be due to the tendinogenic, articular or neurogenic reasons. Numerous theories have been put fourth in the recent past, out of which one of the most popular theories is that the condition results from repeated contraction of the wrist extensor muscles, especially the extensor carpi radialis brevis (ECRB) which may compress the posterior branch of the radial nerve (PBRN) at the elbow during pronation. We studied 72 upper limbs (36 formalin-fixed cadaver) for the origin, nerve supply and the course of PBRN in relation to the ECRB as one of the goal for the present study. The possible presence of an arch of the ECRB around the PBRN was also observed and recorded. The nerve to ECRB was a branch from the radial nerve in 11 cases (15.2%); from the PBRN in 36 cases (50%) and from the superficial branch of the radial nerve in 25 cases (34.7%), respectively. The ECRB had a tendinous arch in 21 cases (29.1%); a muscular arch in 8 (11.1%) cases and the arch was absent in 43 cases (59.7%). When the ECRB had a tendinous or muscular arch around the PBRN, it may compress the same and this condition may worsen during the repeated supination and pronation as observed in tennis and cricket players. The presence of such tendinous or muscular arch should be considered by orthopedicians and neurosurgeons, while releasing the PBRN during LE surgery.     

小波变换在表面肌电信号分类中的应用

针对肌电信号的非平稳特性,采用小波变换方法对表面肌电信号进行分析。通过奇异值分解有效地提取信号特征进行模式识别,能够成功地从掌长肌和肱桡肌采集的两道表面肌电信号中识别展拳、握拳、前臂摧旋、前壁外旋四种运动模式。实验表明,基于小波变换的奇异值分解方法是一种稳定、有效的特征提取方法、为非平稳生理信号的分析提供了新的手段。     

Functional anatomy of the medial ligamentous complex of the elbow. Its role in anterior posterior instability

Abstract The question remains unanswered regarding the role of repair of medial ligament injuries associated with subluxation of the elbow and non-reconstructable radial head fracture and whether or not this will decrease the risk of chronic instability and cubitus valgus. The goal of this study was to define the role of the medial ligamentous complex of the elbow in elbow instability and to describe the anatomy of the complex in 35 fresh-frozen cadaver elbows. We documented medial ligamentous complex anatomy and compared our results to those in the literature. 25 elbows were dissected in order to describe the different bundles of the medial ligament complex and to precise the positions of the elbow that placed each in tension section of the different ligamentous bundles was done to study the role of each in elbow stability. 10 other elbows were dissected and used for the ligamentous section studies which were performed subcutaneously. We found two bundles at the level of the anterior portion and termed them superficial and deep. Section of the anterior bundle lead to posterior subluxation of the elbow at 30-100° flexion in both supination and pronation. Posterior subluxation was obtained after an anterior capsulotomy medial epicondylectomy did not compromise the stability of the elbow after a complete section of the insertion of the deep fibers of the anterior bundle. Elements thus required for stability of the elbow are integrity of the articular surface of the humerus and the ulna, and the anterior bundle of the medial ligamentous complex.