Superficial Flexor Research Articles

Postnatal Contracture Of Young Horses

Summary A theoretical analysis of the pathogenesis of so-called superficial flexor and deep flexor conlracture of the forelegs or growing horses has been presented. The analysis raises a number of questions which could be addressed by observation and experiment. Given that the theoretical analysis is in some measure correct, so-called flexion contracture is, in fact, shortening of immature tendons in response to excessive or abnormal loading and consequent deformation of the immature hoof wall. The deep flexor tendon is of first importance in the pathogenesis of both syndromes as a result of the mechanical situation arising from its insertion distal to the coffin joint.

The Coordinated Action of Abdominal Postural and Swimmeret Motor Systems in Relation to Body Tilt in the Pitch Plane in the Norway Lobster Nephrops Norvegicus

ABSTRACT The responses of the abdominal positioning system and the swimmerets of the Norway lobster Nephrops norvegicus to tilts in pitch and in other vertical planes have been investigated in intact and semi-intact preparations. Tilt of the intact animal in the pitch plane evoked abdominal flexion with the head up and extension with the head down. The response amplitudes were largely independent of tilt angle, and the null point for switching between flexion and extension responses was at the 10° head-up position, which corresponds to the normal posture of the animal. Intersegmental joint angles in the abdomen were significantly different for head-up and head-down tilts. These pitch responses were dependent upon the integrity of the statocysts. Tilts in different vertical planes demonstrated that the abdominal flexion/ extension response was restricted to a range of tilts within ±5° of true pitch. Outside this range, tilts in both directions elicited abdominal extension, which was accompanied by asymmetrical movements of the uropods and swimmerets. In semi-intact preparations, recordings from the motor supply to the abdominal superficial flexor muscles demonstrated a modulation of activity in response to tilt in the pitch plane: several small excitatory axons increased their discharge in the head-up position, while the inhibitory axon f5 fired when the head was down. With tilts in different vertical planes this pattern of firing persisted from pitch almost to roll. The effects of tilt in the pitch and roll planes on the temporal and spatial parameters of swimmeret beating were studied in intact animals. Swimmeret beating was bilaterally symmetrical in pitch: vigorous in the head-down position, when the powerstrokes were directed about 25° to the side, and weak in the head-up position, when the powerstrokes were directed to the rear. Responses in roll were asymmetrical, with the powerstroke of the upper swimmerets directed at about 41° to the side. Recordings of the tonic returnstroke motor neurone of the swimmeret demonstrated that its activity was modulated by tilt in the pitch plane: increasing and becoming rhythmic in the head-down position in active preparations, with the activity phase-locked to the tilt stimulus. With tilts in different vertical planes this unit showed a phase shift at intermediate angles between pitch and roll. Simultaneous recordings of motor activity to the abdominal superficial flexor muscles and the swimmeret tonic returnstroke unit demonstrate closely similar, but not completely coupled, patterns of firing. These results are discussed in terms of the nature of statocyst control of postural and rhythmic abdominal motor systems, the different relationships of motor activities and behavioural responses to tilts in pitch and other vertical planes, and possible neuronal mechanisms that control the interaction of the two abdominal motor systems.

Intrinsic healing of the laceration site in human superficialis flexor tendons in vitro

The intrinsic capability of the human superficialis flexor tendon to heal a reapproximated laceration site in vitro was examined. Segments of lacerated and sutured human superficialis flexor tendons from zone II were cultured for two, four, or eight weeks in vitro and analyzed by use of light and electron microscopy. We noted a specific pattern of intrinsic healing at the repair site during the incubation period. After two weeks, the cells of the epitenon from both tendon stumps proliferated and appeared to migrate into the repair site. Elongated cells of the thickened epitenon bridged the laceration and synthesized new collagen fibers. By eight weeks, a smooth contiguous tendon surface was restored and the internal collagen bundles were brought into intimate contact. The fibroblasts bridging the laceration, both in the epitenon and centrally in the repair site, were oriented perpendicular to the cut surfaces. The cells in the repair site were active in protein synthesis, and new collagen fibers were present. No cellular necrosis was observed in the internal repair site. Our results indicate that human superficialis tendons possess an intrinsic capacity to heal with diffusion and without dependence on extratendinous cells or on adhesions.

Carpal tunnel changes and median nerve compression during wrist flexion and extension seen by magnetic resonance imaging

Magnetic resonance imaging was done on the wrists of 14 volunteer subjects with the wrists in the neutral position, then flexed and extended at 45 degrees. Computer enhanced cross-sectional areas were measured on each subject at the level of the hook of the hamate. In the neutral position the distance between confining structures around the median nerve is 2.0 ± 0.2 mm in the anteroposterior direction, and the mean cross-sectional area of the carpal tunnel is 1.52 cm 2. With the wrist in the extended position the distance available for the median nerve measures 2.2 ± 0.4 mm and the cross-sectional area increases to 1.75 cm 2. When the wrist is flexed, the distance available for the median nerve between the flexor tendons and transverse carpal ligament decreases to 1.1 ± 0.4 mm, and the cross-sectional tunnel area decreases to 1.36 cm 2. Flexion of the wrist and/or fingers both produces a palmar rearrangement of the flexor tendons creating potential compression of the median nerve. The nerve responds to these forces by becoming interposed in various positions between the superficial flexor tendons.

Participation of human superficialis flexor tendon segments in repair in vitro

We analyzed the healing capability of the human superficialis (sublimus) flexor tendon in response to injury in vitro by performing a morphologic study of tendon repair. Tendon segments were cultured in cell-free medium for 2, 4, or 8 weeks, and the cut-end repair sites were compared with those in fresh control segments on light and electron microscopy. Tendon encapsulation had occurred at 2 weeks, by the proliferation and migration of elongated fibroblasts from the epitenon and from collagen bundles of the endotenon to cover the surface of the cut tendon ends. As migrating epitenon cells approached the cut margin, they consistently shifted from a parallel to a circumferential orientation with respect to the tendon axis. By 4 weeks, the encapsulating surface cells had lost their membranous ruffles and had become flattened. Within the capsule, phagocytic cells engulfed collagen debris, and fibroblasts containing extensive rough endoplasmic reticulum profiles and secretory vesicles participated in protein synthesis. The surface of the capsule was smooth and, at 8 weeks, was almost indistinguishable from the epitenon surface of uncultured controls. The capsule now had a collagen-synthesizing layer of fibroblasts superimposed on layers of maturing collagen bundles that separated resting-phase fibroblasts. These findings demonstrate that segments of human superficialis flexor tendons participate in an intrinsic repair response without contributions from extrinsic cells.

Avulsion sous-cutanée des tendons fléchisseurs profonds et superficiels des IV e et V e doigts par blast

The authors report a case of subcutaneous avulsion of flexor profundus and flexor superficialis tendons of the ring and little finger, caused by a blast injury. Treatment consisted of excision of the flexor superficialis tendon with transosseous reinsertion of the flexor profundus tendon. The functional result was good. Subcutaneous traumatic rupture of flexor tendons occurs infrequently, but simultaneous rupture of both flexor tendons is extremely rare. Knowledge of the subject is limited and treatment of this disorder is poorly defined.

Regeneration of an identifiable motoneuron in the crayfish. II. Patterns of reconnection and synaptic strength established in the presence of an extra nerve

The regeneration of neuromuscular connections to the superficial flexor muscle system in the crayfish has been studied under a variety of experimental manipulations. These have provided insight into the factors that can influence the regeneration program of neurons. In this work the regeneration of the largest excitor motoneuron was studied under two different conditions: (1) when the original neuron and a transplanted neuron were growing simultaneously into a denervated target, and (2) when a transplanted neuron was growing into a target that had its original nerve supply intact. In condition 1 both the transplanted and the original neuron formed normal patterns of connectivity and synaptic strength in comparable periods of time. In condition 2 the rate of growth of the transplanted neuron is significantly reduced and does not extend into the lateral fibers of the muscle. It is concluded that the regeneration program of this neuron is not affected by the presence of other neurons growing at the same time into a denervated muscle. Since regeneration is seriously affected if growth occurs into a fully innervated target area, it is suggested that lack of growth stimuli from the target or competitive interactions between established and growing synaptic terminals could influence the regeneration program of this neuron.

Regeneration of an identifiable motoneuron in the crayfish. I. Patterns of reconnection and synaptic strength established in normal and altered target areas.

The superficial flexor muscles of the crayfish are innervated in a position-dependent connectivity pattern, which can be reestablished when the nerve to the muscle is cut. This article deals with the regeneration of the largest excitor motoneuron under three different target scenarios: (1) a normal target with all the muscle fibers present, (2) a reduced target lacking the medial or the lateral muscle fiber population, and (3) when the nerve enters the target in the middle of the muscle field. In scenario 1 the neuron is able to regenerate the normal connectivity pattern within 10 weeks after surgery: all the lateral fibers become innervated, with a linear decline in the probability of connections over the medial fibers. The medial fibers become transiently hyperinnervated before the normal pattern of connections is established. In scenario 2 the normal pattern of connections is established only when the lateral fibers were present; with only medial cells as a target, the transient hyperinnervation stage is stable and no decline in connections was observed. Analysis of regenerated junction potential sizes during the stable hyperinnervation stage show abnormal patterns, suggesting that some aspects of the regeneration program of this neuron can be affected when signals from its prime target cells are missing. In scenario 3 growth begins in both directions until the entire muscle becomes innervated. The normal pattern of connectivity finally emerges after continued lateral growth and diminished medial growth, suggesting that the position of the muscle fibers influences connectivity patterns during the final stages of regeneration.

Phosphorylation of the Cardiac Ryanodine Receptor by cAMP-Dependent Protein Kinase1

The phosphorylation of canine cardiac and skeletal muscle ryanodine receptors by the catalytic subunit of cAMP-dependent protein kinase has been studied. A high-molecular-weight protein (Mr 400,000) in cardiac microsomes was phosphorylated by the catalytic subunit of cAMP-dependent protein kinase. A monoclonal antibody against the cardiac ryanodine receptor immunoprecipitated this phosphoprotein. In contrast, high-molecular-weight proteins (Mr 400,000-450,000) in canine skeletal microsomes isolated from extensor carpi radialis (fast) or superficial digitalis flexor (slow) muscle fibers were not significantly phosphorylated. In agreement with these findings, the ryanodine receptor purified from cardiac microsomes was also phosphorylated by cAMP-dependent protein kinase. Phosphorylation of the cardiac ryanodine receptor in microsomal and purified preparations occurred at the ratio of about one mol per mol of ryanodine-binding site. Upon phosphorylation of the cardiac ryanodine receptor, the levels of [3H]ryanodine binding at saturating concentrations of this ligand increased by up to 30% in the presence of Ca2+ concentrations above 1 microM in both cardiac microsomes and the purified cardiac ryanodine receptor preparation. In contrast, the Ca2+ concentration dependence of [3H]ryanodine binding did not change significantly. These results suggest that phosphorylation of the ryanodine receptor by cAMP-dependent protein kinase may be an important regulatory mechanism for the calcium release channel function in the cardiac sarcoplasmic reticulum.

1989 ARRS Executive Council Award. Exercise-enhanced MR imaging of variations in forearm muscle anatomy and use: importance in MR spectroscopy.

31P MR spectroscopic studies of forearm exercise frequently assume that the volume sampled is appropriate for the muscle of interest and that individual variations in muscle anatomy and use are not important. Postexercise MR imaging was used to assess variations in the size, location, and use of forearm flexors and the accuracy of palpation as a method for locating the muscle of interest. By using the information obtained with MR, the effects of errors in surface-coil position relative to the muscle of interest on 31P MR spectroscopy were examined. In the midforearm of seven men, the greatest diameter of the flexor carpi ulnaris was 29 +/- 4 mm, and that of the flexor digitorum superficialis was 28 +/- 6 mm. However, in the proximal forearm, 58 +/- 10% of the diameter was covered by the palmaris longus, when present (79% of subjects). An unexpected finding was that a focal portion of the superficial finger flexor was used primarily as a wrist flexor in 26% of subjects. Palpation incorrectly identified flexor muscle margins by more than 15 mm in 50% of attempts. When a surface coil was positioned over wrist flexors during handgrip, attenuation of exercise-induced changes in 31P spectra resulted. Exercise-enhanced MR imaging reveals variations in forearm muscle anatomy and use that are common and difficult to appreciate by palpation. It therefore allows improved localization of the sensitive volume for MR spectroscopic studies of muscle physiology.

An evaluation of early motion management following primary flexor tendon repair: Zones 1–3

This study examined consecutive clinic charts for 95 patients with primary or delayed primary repair of traumatically severed flexor superficialis or profundus tendons without concomitant fractures or joint trauma, in digits 2–5, zones 1–3. Patient traits, wound characteristics, surgical variables, therapeutic programs, and intervention outcomes including rupture, need for tenolysis, and total active motion (TAM) were examined. The study included 117 injured fingers and 174 lacerated tendons. The average number of therapy visits was 8.6. The dorsal blocking splint was almost universally used in conjunction with a modified Duran approach. Outcomes of intervention included the following: 7% of patients required follow-up tenolysis; 4% of repaired tendons ruptured; mean TAM at discharge was 217°. Mann-Whitney U and one-way analysis of variance tests indicated that discharge TAM for injuries involving both tendons in a finger and injuries occurring in zone 2 were significantly lower than TAM for injuries involving only the profundus or occurring in zone 1. Pearson correlation identified independent variables that correlated with TAM. Further investigation of the effects of wound and intervention variables on outcome is warranted.

Anatomic relations between the median nerve and flexor tendons in the carpal tunnel: MR evaluation in normal volunteers.

To ascertain the dynamic changes between the median nerve and flexor tendons in the carpal tunnel, MR images of 16 wrists in eight volunteers were studied in flexion, extension, and neutral positions. T1-weighted axial images, 600/20 (TR/TE) were obtained with the wrists straight, extended at 45 degree, and flexed at 45 degree. Each scan was evaluated with regard to positional changes of the median nerve and flexor tendons in the carpal tunnel as well as alterations in nerve shape. In the neutral position, the median nerve was found in one of two standard positions: either anterior to the superficial flexor tendon of the index finger or interposed more posterolaterally between this tendon and the flexor pollicis longus. During extension, the nerve always maintained or assumed an anterior position between the superficial index finger flexor and the flexor retinaculum, while the flexor tendons moved posteriorly. With flexion, the tendons shifted anteriorly toward the retinaculum, and the median nerve was found in one of three positions. It either remained in its anterior position between the superficial index finger flexor and retinaculum or became interposed between the superficial flexor tendons of the index finger and thumb or middle finger and ring finger. Nerve shape varied with its position. Anteriorly positioned nerves were flattened in the anteroposterior plane between the tendon and flexor retinaculum; this was greatest with flexion and least with extension. Interposed nerves were flattened in the mediolateral plane or rounded in configuration. In conclusion, the alignment of the median nerve in the carpal tunnel, its shape, and its relationship to the flexor tendons were variable and dependent on wrist positioning. These findings may explain why certain wrist motions, flexion in particular, predispose a person to carpal tunnel syndrome.

Gantzer's muscle-like variation inserted into the forearm flexor retinaculum.

A rare muscle variation belonging to the forearm flexor muscle group has been observed in three forearms out of nearly 200 Japanese cadavers. It arose from the well developed fascia of the superficial forearm flexor group, crossed the median nerve obliquely and posteriorly lying radial to that nerve, and was inserted into the flexor retinaculum. The muscle variations in the three cases were discussed according to the concept of "corrected" nerve-muscle specificity and conservative morphology. They were conclusively ascribable to the original antebrachial flexor group of Yamada. This seemed to indicate that the variations were related or identical to Gantzer's muscle, and that they showed a possible original or archaic pattern of the original antebrachial flexors.

Regeneration studies on a crayfish neuromuscular system. II. Effect of changing the nerve entry point into the muscle field on the gradient of innervation.

The superficial flexor muscle of the crayfish is a neuromuscular system in which the neurons form position-dependent connectivity patterns with the muscle fibers. This system could be formed with the help of a single medial-to-lateral gradient during development that embodies positional information. To test this gradient hypothesis we changed the nerve's normal medial entry point into the muscle by transplanting it to the middle of the muscle sheet. When all the muscle fibers were present in the target area, most of the neurons studied passed through a stage during regeneration in which they showed preference for either medial or lateral synapse formation. Those neurons that in normal animals innervated preferentially the medial fibers showed a medial preference for new contacts; the neuron that normally innervated the lateral fibers showed a lateral preference for new contacts; the neuron that normally innervated everywhere regenerated equally well into both medial and lateral fibers. Therefore, these neurons are able to detect information regarding their position within the muscle mass and respond to it by preferential synapse formation. The effect of a positional gradient could not be detected when half of the target field was removed prior to regeneration. In this instance, the neuron that innervated the missing target area now regenerated to almost all the available fibers. It is suggested that the interplay of positional cues with other factors at different points in time could determine the final connectivity patterns formed by these cells.

Regeneration studies on a crayfish neuromuscular system. I. Connectivity changes after intersegmental nerve transplants.

The superficial flexor muscles of the crayfish are a neuromuscular system of a few muscle cells innervated by six neurons in a precise position-dependent pattern. The neurons are capable of regenerating their normal connectivity patterns within a short span of time when conditions are favorable. The superficial flexor muscles of the second and third segments, despite their similarities in neuronal and muscle cell size and number, have distinctive connectivity patterns; some homologous neurons form similar patterns but other homologous neurons form patterns that are reversed between segments. We transplanted each segment's nerve into each other's muscle in order to observe regeneration of the nerves into a target area that differed in connectivity patterns from their original muscle. During the first weeks of regeneration all neurons formed a connectivity pattern with more connections medially and declining connections laterally, a pattern determined by the medial location of the nerve transplant. This pattern is maintained for most of the neurons, but for some there is an eventual reduction in medial connections as maximum synapse formation shifts to the lateral muscle fibers. Three of the eight neurons studied were able to regenerate connectivity patterns that corresponded to their segment of origin and not to their host muscle. This suggests that intersegmental muscle differences are not influencing the formation of these connectivity patterns, so the neurons will follow their inherent synaptogenesis program.

Delayed repair of flexor profundus tendon in the palm (zone 3) with superficialis transfer

Transfer of a flexor superficialis tendon was done in an attempt to restore flexor profundus function, as a secondary procedure, in the palm (zone 3) in 16 hands. These were cases in which direct repair was not possible. Eight patients achieved a total active motion (TAM) above 200 degrees and two more were above 180. Of those eight with TAM above 200 degrees four required a secondary tenolysis to improve to that level. Transfers in six patients were regarded as failures. Failures were associated with a poor tendon bed and noncompliant patients. This is a procedure that has limited indication in a cooperative patient with a good tendon bed who reports late with both flexor tendons cut in zone 3.

Interactions between the tonic and cyclic postural motor programs in the crayfish abdomen.

1. In the crayfish (Procambarus clarkii) abdomen, the superficial flexor and extensor muscles and the motoneurons that innervate them are employed during two completely different modes of behavior: (1) tonic postural adjustments and (2) cyclic movements associated with backwards terrestrial walking. We have tested the possibility that these two behavioral subsystems share at least some of the same tonic premotor interneurons. 2. Of the 108 tonic flexion- and extension-producing interneurons monitored during cyclic pattern generation, only 25 were recruited while 36 were inhibited. None of the recruited interneurons made a measurable contribution to the cyclic motor output. Similarly, none of the 20 inhibitory interneurons of the tonic subsystem recorded in this study was found to play a role in shaping the cyclic motor pattern. 3. Simultaneous activation of single tonic postural interneurons with the cyclic motor pattern revealed that the two behavioral subsystems interact in complex ways. Some tonic interneurons produced motor outputs that overrode the cyclic motor outputs while the motor outputs of other tonic interneurons were completely overwhelmed by the cyclic motor program. Still other tonic interneurons generated motor outputs that predominated over cyclic patterned outputs in some ganglia but were masked by the cyclic motor pattern in other ganglia. 4. Although weak interactions between the two subsystems occur at the premotor level, they have little effect on the normal generation of the cyclic pattern. Stronger interactions apparently occur at the level of the motoneurons and these interactions presumably may form the basis of switching from one behavior to the other. We conclude, therefore, that each behavioral subsystem relies upon its own unique set of premotor interneurons. Finally, those interneurons contributing to the cyclic motor pattern have not yet been identified.

Technique de prélèvement du tendon fléchisseur superficiel de l'annulaire

Raising of the superficial flexor of the ring finger for tendon transfer may leave major sequelae, especially if the blood supply of the deep tendon is damaged. For this reason, the authors stress two important points: raising of the flap proximal to the chiasma to avoid damage to the blood supply of the deep tendon, stepped section for opening of the tendon sheath to prevent any mechanism of adherence. The intersection should be followed by gentle traction by means of a splint.

Lumbrical function: Interaction of lumbrical contraction with the elasticity of the extrinsic finger muscles and its effect on metacarpophalangeal equilibrium

Since conflicting statements have been made in the literature regarding the influence of lumbrical contraction on the metacarpophalangeal (MP) joint, a study was undertaken to determine the length-tension curve for the index flexor profundus. Four fresh cadaver hands were used. Measurements for the flexor superficialis and for the common extensor were determined in there. The measurements were correlated with measured displacement of these tendons in six finger positions. Isolated lumbrical contraction was then mechanically simulated, acting against spring homologues of the index extrinsic muscles. The finger moved from the rest position toward the intrinsic position with loads of less than 5 N. This demonstrated that in addition to its effect on interphalangeal joint extension, the lumbrical acting alone can cause flexion of the metacarpophalangeal joint.

MR imaging of the carpal tunnel: normal anatomy and preliminary findings in the carpal tunnel syndrome.

MR imaging was performed through the carpal tunnel in 18 wrists of nine normal volunteers and compared with cryomicrotome sections from cadaver wrists. MR reliably imaged the flexor retinaculum and carpal bones and thus defined the borders of the carpal tunnel. In all cases the median nerve was seen as an ovoid structure of moderate signal intensity and was easily distinguished from the flexor tendons of the hands running in the carpal tunnel. The tendons were separated from each other by their tendon sheaths, and this allowed for identification of the various tendons. Anatomic variations encountered in the normal volunteers included anomalous positioning of the origin of the lumbrical muscles within the carpal tunnel in two, persistent median arteries in two, and interposition of the median nerve between the flexor pollicis longus and the superficial flexor tendon to the index finger in one. Preliminary observations in 10 wrists of patients with carpal tunnel syndrome include segmental and diffuse swelling of the median nerve in six, distortion of the nerve in one, and thickening of the tendon sheaths in one. We conclude that MR imaging accurately and reliably displays the normal anatomy of the carpal tunnel and can detect morphologic changes in patients with carpal tunnel syndrome.