Intertendinous Connections Research Articles

Role of intertendinous connections in distribution of force in the human extensor digitorum muscle.

The human extensor digitorum (ED) muscle gives rise distally to multiple tendons that insert onto and extend digits 2-5. It has been shown previously that the spike-triggered average forces of motor units in ED are broadly distributed across many tendons. Such force dispersion may result from linkages between the distal tendons of ED and may limit the ability to move the fingers independently. The purpose of this study, therefore, was to determine the extent to which the connections between tendons of ED distribute force across the fingers. Stimulation of ED muscle fibers was performed at 107 different sites in four subjects. The isometric force exerted on digits 2-5 resulting from the stimulation was measured separately. Stimulus-triggered averaging of each of the four force channels yielded the force contribution to each of the digits due to the stimulation at each site. A selectivity index from 0 (a site that distributes force equally across the fingers) to 1.0 (a site that produces force on a single finger) was computed to describe the distribution of force across the four fingers. The selectivity index resulting from electrical stimulation of ED averaged 0.70 +/- 0.21. These selectivity index values were significantly greater (P < 0.001) than those obtained for single motor units using spike-triggered averaging. These findings suggest that linkages between the distal tendons of ED probably play only a minor role in distributing force across the fingers and, therefore, other factors must be primarily responsible for the inability to move the fingers independently.

An anatomic study of the extensor tendons of the human hand.

A total of 548 upper limbs (276 right and 272 left hands) from Japanese cadavers were dissected. The arrangements of extensor indicis proprius, extensor digitorum communis (EDC), and extensor digiti minimi tendons and the intertendinous connections were studied. The most common pattern of extensor tendons was as follows: the index finger had a single EDC tendon, the middle finger had a single EDC tendon, the ring finger had a single EDC tendon, and the small finger had a single EDC tendon or a single common EDC tendon distributed to the ring and small finger. A single extensor indicis proprius tendon ran along the ulnar side of the EDC, and the extensor digiti minimi tendon consisted of 2 slips. Intertendinous connections were classified into 3 types: type 1 with a filamentous band, type 2 with a fibrous band, and type 3 with a tendinous band subdivided to r-shaped and y-shaped. The most common patterns were type 1 in the second intermetacarpal space (IMCS), type 3r in the third IMCS, and type 3y in the fourth IMCS.

Measuring force transfers in the deep flexors of the musician's hand: Theoretical analysis, clinical examples

In the present paper the anatomical and functional interdependencies which regularly exist between the deep flexor tendons of the different fingers are modelled. The model results are validated by measurements on real hands. The results show that intertendinous force transfers may be caused by (i) coactivation of muscle fibres inserting in different tendons, and (ii) passive connections between tendons or muscle bellies. The coactivation is validated by the measuring results of a hand in which all intertendinous connections were surgically removed. The present models and measurements are currently used for diagnosis of hand problems in musicians at our hand clinic.

A generic morphological model of the anatomic variability in the m. flexor digitorum profundus, m. flexor pollicis longus and mm. lumbricales complex.

In the present study a generic model is presented of the anatomic variability in the muscle group formed by the m. flexor digitorum profundus, m. flexor pollicis longus and mm. lumbricales. This model provides a hypothesis about the structural causes of the frequent interdependence of tendons and muscle bellies in this muscle group. The model considers the muscle group as composed of two simple elementary building blocks: the monogastric contractile units of the FDP-FPL, and the digastric contractile elements of the lumbrical, and shows that these units can be assembled into complex entities, to which in reality a third structural element, the synovial membranes, not discussed in the present paper, adds a further complexity. The model allows to generate homologues of the existing anatomical variants, which are illustrated by typical dissection results. The present study should be of relevance to the morphologist, embryologist, surgeon, and musician/pedagogue. To the morphologist, it presents an alternative method of description or understanding of anatomic variability, based on (i) the 'atomary' concept that the anatomic structure is assembled from simple basic elements, and (ii) the local spatial constraints. To the embryologist, it raises the question to what degree the 'atomary' anatomical components of this model, which describes the macroscopic anatomy of the muscle group in detail, have an embryological basis. To the surgeon, the study presents detailed information about the scope of the variability in the deep flexor group, and the nature of its intertendinous connections. To the musician/pedagogue, it presents a visual illustration of the congenital interdependence of the muscles and tendons of an important finger motor group, as a possible cause of lack in finger independence which may hamper a fluent instrumental technique.

Connections between the tendons of the musculus flexor digitorum profundus involving the synovial sheaths in the carpal tunnel.

In the carpal tunnel anatomical interconnections between the tendons of the musculus flexor digitorum profundus are systematically present. These interconnections limit the mutual tendon displacements, which decreases finger independence and may be problematic in a musician's hand. The present study investigates a possible role of the synovial sheaths in the formation of these intertendinous connections in the carpal tunnel. To this end a morphological model is provided which correlates the often distinctly fibrous structure of the deep flexor tendons in the carpal tunnel and the frequent exchange of tendon fibres between the tendons to the different fingers, with the tendency of the synovial membranes to strongly adhere to the tendons. This model is validated by gross dissection results, and by cross sections of the flexor tendons in the carpal tunnel. In agreement with the model, the anatomic data show that the synovial membranes tend to invade and become trapped in tendons made up from individualised tendon strands, and also strongly adhere to the substantial amounts of tendon fibres which may be exchanged between the flexor tendons proximal to the lumbrical origins. These fibres and the synovial membranes may form a strong fabric able to withstand substantial stretching forces of interconnected oppositely pulled flexor tendons.

Traumatic dislocation of extensor II and V fingers at the level of the metacarpophalangeal joint and its treatment

The extensor tendons of fingers II and V on the back of the hand have intertendinous connections (connectors) that prevent their displacement during flexion-extension movements of the finger in the metacarpophalangeal joints. According to anatomical studies, the main phalanx is covered by spiral aponeurotic fibers from the back to the level of the metacarpophalangeal joint. However, the functional significance of this anatomical formation is not fully elucidated. As our clinical observations have shown, this formation carries a great functional load, especially for the II and V fingers of the hand.

The accessory tendon of the extensor indicis muscle.

The extensor indicis and the extensor pollicis longus muscles differentiates from the extensor digitorum profundus muscle. The extensor indicis muscle is an unstable muscle concerning its variations. Kosugi (1989) found the frequency of variations of this muscle to be 20% and described 18 different types of variations of this muscle. This study describes a rare case of the extensor indicis muscle. The extensor indicis muscle develops an accessory tendon in between the extensor indicis and extensor pollicis longus muscle. It passes under the extensor retinaculum. At the level of 2nd metacarpal bone, the accessory extensor indicis tendon is connected to the tendon of the extensor pollicis longus muscle by a intertendinous connection.

Extensor tendons of the fingers: Arrangement and variations‐ii

One hundred eighty-one dissected hands were examined to study the pattern of extensor tendons on the dorsum of the hand. Extensor digitorum often had multiple tendons for the middle and ring fingers. Its contribution to the little finger was usually by a bifurcating tendon common with that of the ring finger. The index finger always received a single tendon. Intertendinous connections between the various tendons of the extensor digitorum were variable but were most frequent between ring and middle fingers. Extensor indicis had one tendon in most of the specimens and it was always on the ulnar side of the extensor digitorum tendon. This remained true even when there were multiple tendons. Extensor digiti minimi had two tendons in most cases. It was always linked to extensor digitorum either by receiving one or part of its tendon or by an intertendinous connection. Two accessory muscles were seen, one was extensor indicis brevis replacing the proper muscle. The other, the extensor medii brevis, was distributed to the middle finger.

A cadaveric study of the peroneus tertius muscle

AbstractMost anatomy textbooks state that peroneus tertius arises from the distal third of the fibula and is inserted into the fifth metatarsal. In a study of one limb from each of 40 cadavers, peroneus tertius was absent in 2 limbs, and in 35 it arose from the lower middle quarter of the fibula. The origin was continuous with that of extensor digitorum longus in 33 limbs, and the length of the origin was correlated with the width of the tendon (r = 0.67). The tendon was single in 37 limbs and double in 1. Intertendinous connections between peroneus tertius and extensor digitorum longus were found in 6 limbs. The trapezoidal insertion of peroneus tertius into the fifth metatarsal was bifurcate in two cases and trifurcate in one. Our study suggested that the standard textbook descriptions of peroneus tertius need to be revised. © 1993 Wiley‐Liss, Inc.

Distribution of the extensor tendons on the dorsum of the hand

AbstractThe patterns of the tendons of extensor digiti minimi, extensor digitorum, and extensor indicis have been studied on the dorsum of the hands of 25 embalmed cadavers.Each of the tendons of extensor digitorum (ED) is usually single, but those of the middle and ring fingers are occasionally multiple. Intertendinous connections are of variable pattern. The ED tendon of the little finger lies closely to that of the ring finger, with which it may be fused, or it may be absent. It is suggested that it may be undergoing evolutionary reduction.Extensor digiti minimi (EDM) usually has two tendons, but may have three or four. In addition to EDM, the little finger also receives either a separate tendon, or a tendinous slip, from ED.Extensor indicis (EI) varies in the number of its tendons, in its position relative to the ED tendon to index finger, and in its connection to extensor pollicis longus tendon.Examples of supernumerary muscles (extensor digitorum brevis manus, extensor indicis brevis, and extensor pollicis et indicis communis) were also found. © 1992 Wiley‐Liss, Inc.

The E-flat hand

The disability suffered by a professional pianist because of difficulty in carrying out certain of the finger movement sequences involved in playing in the key of E flat appeared to be caused by limitation of independent flexion movements between the index and long fingers of his right hand. The range of independent movement of the fingers was considerably increased, with relief of his disability, by dividing the intertendinous connection between the extensor tendons of the two fingers on the dorsum of the hand.

Twitch contraction for identification of human muscle afferents.

A classical test to differentiate between Golgi tendon organs and muscle spindles is the twitch contraction elicited by electrical stimulation. The possibility of producing maximal twitches in the finger extensor muscles using surface stimulation over the muscle belly was investigated as well as the feasibility of the test in microneurography experiments. Electrical stimuli were applied either over the muscle in the forearm or the radial nerve in the upper arm, while the resulting torque output at single metacarpophalangeal joints was measured. The relationship between current intensity and maximal contraction force was determined and stimulus response plots were constructed over a large range of current intensities. Stimulation of the radial nerve always yielded plots with a steep and monotonous rising limb up to a plateau. It was concluded that the plateau represented maximal twitch contractions. With transcutaneous stimulation over the muscle belly, the stimulus response plots were usually more complex. However, this could be explained by force transmission through the intertendinous connections on the dorsum of the hand and by antagonist activation. It was concluded that maximal twitch contractions can readily be elicited in the human extensor digitorum muscle with nonpainful transcutaneous electrical stimulations. Moreover, maximal twitches are compatible with single unit recording from muscle afferents in microneurography experiments.

弾ぱつを伴った指伸筋けん脱臼の１例

Dislocation of the extensor tendon at the MP joint is uncommon. We reported dislocations of both long-finger and ring-finger extensor tendons ulnarward, and the left little finger radialward. Most authors found the lesion to be tear of expansion hood or intertendinous fascia. But, our patient had thinning of radial expansion hood of the left long-finger, normal expansion hood of the right long and ring-fingers. And, both intertendinous connection between the index and long fingers were absent. So, we find that the lesion is not tear of expansion hood but absence of intertendinous connection. We treated dislocation of extensor tendons operatively with intertendinous connection. No recurrence of dislocation is present 10 months after surgery.