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PubMed2007

The oblique cord of the forearm in man.

There is minimal and often conflicting data in the literature regarding the oblique cord of the forearm. The current study seeks to elucidate further the anatomy of this structure of the upper extremity. In adult cadavers, the oblique cord was observed for and, when found, measurements were made of it. Ranges of motion were carried out while observation of the oblique cord was made. An oblique cord was found on 52.6% of sides. Gantzer's muscle was found on 55% of sides and, when present, had attachment into the oblique cord on five sides. The oblique cord was present on 13 sides with a Gantzer's muscle. Of the 20 sides with an oblique cord, no Gantzer's muscle was found on 10. The mean length of the oblique cord was 3.4 cm. In the majority of specimens, this cord tapered from proximal to distal. The proximal, middle, and distal widths of this structure had means 9, 7, and 4 mm, respectively. The oblique cord was found to travel approximately 45 degrees from a line drawn through the ulna and more or less traveled perpendicular to the insertion site of the bicipital tendon. This ligament was lax in the neutral position and with pronation became lax in all specimens. The oblique cord progressively became taut with increased supination from the neutral position and was maximally taut with the forearm fully supinated. Tautness of this cord was also found with distal distraction of the radius. Following the transection of the oblique cord, no discernable difference was observed in regard to maximal supination of the forearm or distal distraction of the radius. No obvious instability of the proximal forearm was found following transection of the oblique cord. Functionally, although the oblique cord may resist supination, it is unlikely that this structure affords significant stability to the proximal forearm, as it was often absent, of a very small caliber, and based on our observations, following its transection, the amount of supination of the forearm did not increase. Moreover, one would expect that this structure would never resist supination alone, as the larger overlying muscles would become taut prior to calling upon the action of this cord. Based on our findings, the function of the oblique cord appears insignificant in providing significant stability to the proximal forearm; however, further investigative studies are now necessary to confirm these data.

Aged↗

PubMed2006

Anatomic study of distally based pedicle compound flaps with nutrient vessels of the cutaneous nerves and superficial veins of the forearm.

The purpose of this study was to describe the anatomic basis for a distally based neurovenovascular pedicle compound flap, with nutrient vessels of the cutaneous nerves and superficial veins of the forearm. In this study, the origins, branches, and anastomoses of nutrient vessels of the cutaneous nerves and superficial veins of the forearm and their relationships with the blood supply of adjacent muscle, bone, and skin were assessed in 96 adult cadavers by perfusion of red gelatin into the superior limb arteries. The results showed that the nutrient vessels of cutaneous nerves and superficial veins of the forearm were found to have multiple origins, consisting of six longitudinal vascular plexuses and one transverse vascular plexus of the forearm, as follows: 1) the anterior-lateral vascular plexus from cutaneous branches of the radial artery; 2) the anterior-medialis vascular plexus from cutaneous branches of the ulnar artery; 3) the dorso-lateral vascular plexus from radial osteal and cutaneous branches; 4) the dorso-medialis vascular plexus from ulnar osteal and cutaneous branches; 5) the radial vascular plexus from osteal and cutaneous branches of the radial artery, cutaneous branches of the radial artery in the upper wrist, recurrent branches of the styloid process of the radius, and the radialis vascular plexus of cutaneous branches of the tabatière anatomique (anatomical snuffbox); and 6) the ulnar lateral vascular plexus from cutaneous branches of the ulnar artery in the upper wrist and osteal and cutaneous branches. The transverse vascular plexus is composed of dorsal branches of the ulnar and radial arteries. These perforating branches give fascial branches, cutaneous branches, periosteal branches, and nutrient vessels of cutaneous nerves and superficial veins. These results suggest that nutrient vessels of the cutaneous nerves and superficial veins of the forearm have the same origins as those of the nutrient vessels of adjacent muscles, bones, and skin of the forearm, which can be designated as five types of distally based pedicle flaps with nutrient vessels of cutaneous nerves and superficial veins of the forearm, whose rotation point is at the wrist joint. This flap can be applied to repair tissues of distal parts of the hand.

Adult↗

PubMed1985

Myoelectric response of the human triceps brachii to displacement-controlled oscillations of the forearm.

The dynamic relations between the surface myoelectric activity in tonically contracting triceps brachii and the forearm rotation (proportional to triceps stretch) were measured by imposing small, sinusoidal, displacement-controlled perturbations on the forearm position. Three normal, adult, male subjects participated in these experiments. The amplitude of the forearm rotation, the driving frequency, and the tonic contraction level were all carefully regulated. The mean rectified triceps EMG (the output) showed a strong harmonic at the driving frequency, and the frequency-response characteristics were computed directly by comparing the amplitude and phase of this harmonic to that of the forearm flexion angle (the input). The (electrical) reflex gain is defined as the amplitude ratio of output to input. The system response was measured from 2 to 18 Hz, at two tonic contraction levels and two forearm rotation amplitudes, about a mean position of 90 degrees forearm flexion. The results show clearly that the system response is nonlinear: the reflex gain decreases with forearm rotation amplitude. (This gain also increases with tonic contraction level for sufficiently low values of the latter variable.) The measured frequency-response characteristics of the system can be modeled approximately as a second-order linear lead filter with a single time delay, followed by a saturating nonlinearity. Both model-independent estimates and least-squares model fitting, yielded values of the time delay of the order of 25 ms, suggesting that a segmental mechanism mediates reflex activity. Simplified calculations and limited measurements are presented to show that a nonlinear system of the type we have identified with constant displacement driving may appear linear under constant torque driving. Our directly-measured frequency-response characteristics differ from those reported by investigators employing random, rather than periodic, driving; possible reasons for these apparent discrepancies are discussed.

Arm↗

PubMed1988

Bone mineral content by photon absorptiometry of the mandible compared with that of the forearm and the lumbar spine.

A new method for measuring the bone mineral content (BMC) of the mandible by dual-photon absorptiometry (DPA) has recently been introduced. The purpose of the present investigation therefore was to examine the long-term precision for 32 months in vitro and in vivo for assessment of BMC in the mandible and to examine the relationship in vivo among BMC of the mandible, the forearms, and the lumbar spine as measured by DPA and/or single-photon absorptiometry (SPA). For comparison, the relationship between forearm BMC as measured by DPA and SPA was studied. The long-term precision of the mandibular BMC was 0.8% in vitro, independent of age and change of radioactive source, and 2.1% by assessment in vivo. A significant relationship (P less than 0.01) was found between BMC of the lumbar spine and the forearms and between the two sets of forearm BMC measured by DPA and SPA. Thus, relative BMC changes of the forearms can be compared without respect to type of forearm bone scanner used. The BMC changes of the mandible can only be evaluated by scanning of the mandible itself. The present DPA bone scanner is suitable for follow-up analyses of the BMC changes of the mandible and the forearms.

Adult↗

PubMed2002

The transposed forearm loop arteriovenous fistula: a valuable option for primary hemodialysis access in diabetic patients.

The distal forearm is the site of first choice for creation of an arteriovenous fistula for hemodialysis. The archetypal procedure, the primary radial-cephalic fistula as described by Brescia, yields excellent functional patency for many patients. Results are much less favorable in patients with diabetes mellitus, for whom non-maturation rates as high as 70% have been reported. This is likely due to inadequate inflow caused by atherosclerotic disease of the forearm arteries in diabetics. Secondary autologous access procedures often involve upper arm configurations such as transposed brachial-basilic fistulas. The present study focuses on a valuable alternative for hemodialysis access in diabetic patients, the transposed forearm loop arteriovenous fistula. Over a 2-year period, 16 forearm loop fistulas were created in 16 diabetic patients who either had a failed radial-cephalic fistula or had arterial anatomy deemed inadequate for wrist fistula formation. In each case, the forearm segment of the basilic or cephalic vein was transposed to form a U-shaped loop and anastomosed to the brachial, proximal radial, or proximal ulnar artery distal to the antecubitai fossa. Functional patency was defined as usability for dialysis. Patency rates were calculated by Kaplan-Meier survival analysis. From our results we determined that the forearm loop fistula is an excellent but underutilized technique that exploits the forearm veins while circumventing the distal arterial supply, thus preserving the upper arm vasculature for future use.

Aged↗

PubMed1995

Local angiotensin-converting enzyme inhibition blunts endothelin-1-induced increase in forearm vascular resistance.

OBJECTIVE: The physiologic role of endothelin-1 is not well established; however, it may have a role in modulation of peripheral vascular tone complimentary to angiotensin II. In vitro and animal studies suggested an interrelationship between angiotensin II and endothelin-1 vasoconstriction. We hypothesized that local vascular or systemic renin-angiotensin II systems must be intact for endothelin-1-mediated vasoconstriction in humans. METHODS: To test this hypothesis, responses to brachial artery infusion of endothelin-1 alone and endothelin-1 plus local low-dose infusion of enaliprilat were studied in seven healthy male and seven healthy female volunteers. RESULTS: In these subjects, baseline forearm vascular resistance (mean +/- SEM; 24 +/- 3.5 mm Hg.ml/dl forearm vol/min) increased with a 38.2 ng/min endothelin-1 infusion (61.8 +/- 6.8 mm Hg.ml/dl forearm vol/min; p < 0.01). Forearm vascular resistance decreased when 38.2 ng/min endothelin-1 was infused concomitantly with a local 5 micrograms/min infusion of enaliprilat (45.5 +/- 5.9 mm Hg.ml/dl forearm vol/min; p < 0.01 compared with endothelin-1 alone). CONCLUSIONS: These data indicate that an endothelin-1-induced increase in forearm vascular resistance is inhibited by local forearm angiotensin-converting enzyme inhibition.

Adult↗

PubMed1984

Post-traumatic insulin resistance in uninjured forearm tissue.

Insulin resistance is a hallmark of post-traumatic metabolism. The mechanism and site of this resistance, however, have not been elucidated. To further define the site of this abnormality, glucose uptake across the uninjured forearm was measured in conjunction with hyperinsulinemic glucose clamp studies in 21 normals and 5 patients with multiple trauma. Under these conditions, glucose infused approximates whole body glucose disposal (M, milligrams/kilogram/min). Forearm glucose flux (Q, milligrams/100 ml tissue/min) is the product of blood flow and arterial-deep venous glucose difference (A-DV). In the basal, unperturbed state forearm glucose uptake (Q) was significantly lower in the patients (0.01 +/- 0.04 mg/100 ml/min) than in the normals (0.06 +/- 0.02) and not significantly different from zero. Basal serum insulin in patients (17 +/- 3 microU/ml) was significantly greater than controls (11 +/- 1). During steady-state conditions of euglycemia and hyperinsulinemia, forearm glucose uptake in the patients (0.36 +/- 0.18 mg/100 ml/min was not significantly different from the basal value. At comparable serum insulin levels in controls, forearm glucose uptake was approximately three times that of the injured patients. This is the first in vivo confirmation of the hypothesis that post-traumatic insulin resistance occurs in uninjured forearm tissue, primarily skeletal muscle. Diminished forearm glucose uptake is present in the resting basal state and cannot be overcome by increasing insulin concentrations.

Adult↗

PubMed1991

Glycerol and lactate uptake in human forearm.

Arteriovenous differences for lactate and glycerol reported across the human forearm are inconsistent in direction and magnitude. Such inconsistency could represent the effects of differing forearm compositions. The hypothesis was tested by examination of 37 studies of forearm arteriovenous differences for lactate, glycerol, glucose, and oxygen (only measured in 25 studies) in 23 normal subjects after overnight fast. In 16 studies, glycerol was taken up rather than released by the forearm, and in 12 of these the arteriovenous difference was greater than could be accounted for by analytical variation. The arteriovenous differences for glycerol and lactate were positively correlated (r = .44, P less than .01). The hypothesis that glycerol and lactate uptake might reflect a more "oxidative" forearm was not borne out, since neither glycerol nor lactate arteriovenous differences correlated with that for oxygen, although oxygen and glucose arteriovenous differences and fluxes were correlated (fluxes: r = .60, P less than .01). The arteriovenous difference for glycerol was positively related to body mass index, arguing against a variable contribution from fat. The hypothesis that the direction of glycerol and lactate exchange would reflect the forearm composition was not borne out by the analysis of repeated studies on the same individual, which showed that the variation within subjects was not significantly less than that between subjects. Therefore, we conclude that in approximately 40% of studies in normal subjects after an overnight fast, the forearm will show glycerol uptake, although we have been unable to identify any physiological reason for this phenomenon. Peripheral glycerol uptake has implications for studies in which glycerol release is taken as a measure of lipolysis.

Adult↗

PubMed1994

Effect of L-arginine on acetylcholine-induced endothelium-dependent vasodilation differs between the coronary and forearm vasculatures in humans.

OBJECTIVES: The goal of this study was to determine whether the effect of L-arginine on endothelium-dependent vasodilation evoked with acetylcholine differs between the coronary and forearm vasculatures in humans. BACKGROUND: Administration of L-arginine, a substrate in the production of endothelium-derived nitric oxide, may stimulate the release of nitric oxide. METHODS: Seven patients with normal coronary angiograms and seven with mild coronary artery disease and hypertension underwent coronary arteriography and an intracoronary Doppler catheter technique, and the diameter of the large epicardial coronary artery and coronary blood flow were measured. Forearm blood flow was measured by use of a strain gauge plethysmograph. RESULTS: Before L-arginine administration, acetylcholine (1 to 30 micrograms/min) increased coronary blood flow with modest vasoconstriction of a large coronary artery. Acetylcholine (4 to 24 micrograms/min) also increased forearm blood flow. The acetylcholine-induced increases in coronary and forearm blood flow were significantly less in patients with coronary artery disease than in control patients. Intracoronary infusion of L-arginine at 50 mg/min did not alter responses of the large coronary artery diameter or coronary blood flow to acetylcholine in either group. In contrast, L-arginine at 10 mg/min significantly (p < 0.01) augmented the forearm blood flow response to acetylcholine (4 to 24 micrograms/min) to a similar extent in the two groups. CONCLUSIONS: The effect of L-arginine on acetylcholine-induced vasodilation differs between the coronary and forearm vasculatures in humans. It is suggested that impaired acetylcholine-induced coronary and forearm vasodilation in patients with coronary artery disease and hypertension may not be related to a limited availability of L-arginine.

Acetylcholine↗

PubMed1995

Angiotensin II inhibits the forearm vascular response to increased arterial pressure in humans.

OBJECTIVES: This study tested the hypothesis that angiotensin II may inhibit the forearm vascular resistance response to an increase in arterial pressure in normal humans. BACKGROUND: Angiotensin II inhibits baroreflex-mediated reductions in heart rate and peripheral sympathetic activity during increases in arterial pressure in experimental animals. If present in humans, such effects could contribute to the pathophysiologic role of angiotensin II in hypertension and heart failure. METHODS: Two investigations were performed. In the first, forearm vascular resistance responses were compared during equipressor infusions of angiotensin II and phenylephrine. In the second, heart rate, forearm vascular resistance and systemic venous norepinephrine spillover responses were compared during head-down tilt and head-down tilt plus phenylephrine with concomitant angiotensin II or vehicle infusions. RESULTS: In the first study, forearm vascular resistance increased from 44 +/- 12 (mean +/- SD) to 54 +/- 13 U (p < 0.05) during angiotensin II but did not change during phenylephrine infusions (39 +/- 8.5 to 40 +/- 14 U) that increased mean arterial pressure comparably (88 +/- 9.8 to 103 +/- 14 mm Hg during angiotensin II, p < 0.001; 91 +/- 7.6 to 104 +/- 9.2 mm Hg during phenylephrine, p < 0.001). In the second study, the decrease in heart rate and forearm vascular resistance during the combination of head-down tilt and phenylephrine were both attenuated during concomitant angiotensin II compared with vehicle infusions: delta HR/delta MAP = -2.2 beats/min per mm Hg during vehicle and -0.87 beats/min per mm Hg during angiotensin II (p = 0.07); delta FVR/delta MAP = -2.8 U/mm Hg during vehicle and -0.19 U/mm Hg during angiotensin II (p = 0.01), where delta HR = change in heart rate; delta MAP = change in mean arterial pressure; and delta FVR = change in forearm vascular resistance. Norepinephrine spillover declined during vehicle infusions (612 +/- 367 to 418 +/- 196 ng/min, p < 0.05) but not during angiotensin II infusions despite a greater increase in mean arterial pressure when the subpressor angiotensin II was combined with head-down tilt and phenylephrine (6.0 +/- 7.0 mm Hg during vehicle; 14 +/- 9.4 mm Hg during angiotensin II, p < 0.01). CONCLUSIONS: Both pressor and nonpressor infusions of angiotensin II immediately inhibit the forearm vascular response to mild baroreflex loading in normal humans. If present over the long term, such effects could contribute to inappropriate peripheral resistance in diseases such as hypertension and congestive heart failure.

Adult↗

PubMed1991

Cutaneous responses to topical methyl nicotinate in human forearm and vulvar skin.

In order to identify and define differences in percutaneous absorption and microcirculatory sensitivity between forearm and vulvar skin we studied the response of human forearm and vulvar (labium majus) skin to topical methyl nicotinate (MN) in 11 healthy premenopausal volunteers. MN-induced erythema was assessed by laser Doppler velocimetry (LDV). The following parameters were compared: 1) basal cutaneous blood flow, 2) the time to peak response, 3) the magnitude of LDV peak response, 4) the area under the LDV response-time curve and 5) the decay time to 75% of peak response. Basal cutaneous blood flow at the vulva was higher than at the forearm (P less than 0.05); the magnitude of peak response was lower at the vulva than at the forearm (P less than 0.01); the area under the curve was lower at the vulva than at the forearm (P less than 0.001); the decay time to 75% of peak response was shorter at the vulva than at the forearm (P less than 0.001). The time to peak response showed no significant differences between sites. The results indicate that the MN-induced vasodilatation is less intense and lasts shorter in vulvar compared to forearm skin.

Administration, Cutaneous↗

PubMed2004

The use of digital X-ray radiogrammetry and peripheral dual energy X-ray absorptiometry in patients attending fracture clinic after distal forearm fracture.

Despite the fact that 50% of postmenopausal women with Colles' fracture have evidence of osteoporosis, the vast majority of women with forearm fractures are neither investigated nor treated for osteoporosis. Digital X-ray radiogrammetry (DXR) provides an attractive option in patients with distal forearm fracture, as it requires no additional X-rays over and above those performed as part of clinical management. We have compared DXR analysis of nonstandardised plain films taken routinely in accident and emergency with peripheral dual energy X-ray absorptiometry (pDXA) in a group presenting with distal forearm fracture. Women presenting with a fracture of the distal forearm underwent pDXA measurements of the calcaneus. Plain X-rays performed at the time of presentation were taken to allow adequate fracture treatment. No additional radiographer training or standardisation of films was performed. The DXR technique relies upon visualisation of the metacarpal shafts and this was not visualised on 123 of 201 (61%) films. The AP plain film was thus assessed using DXR for BMD in the remaining 78 patients with a mean age of 70.6 years (SE = 1.3). Mean BMD for DXR was 0.46 g/cm2 (SE = 0.01) and for pDXA was 0.40 g/cm2 (SE = 0.01). The correlation between BMD measured using the two techniques was 0.55 (P < 0.001). Although DXR measurements could not be performed in all patients, this proportion could easily be increased by routinely including the metacarpal shaft region in X-rays obtained after suspected distal forearm fracture. The correlation between the pDXA and DXR results is comparable with those reported between DXA measurements at the forearm, spine and hip. Our study suggests that DXR may provide a feasible method for the assessment of future fracture risk. The potential advantage of DXR over calcaneal pDXA measurements is that standard forearm X-ray obtained as part of fracture management could be used.

Absorptiometry, Photon↗

PubMedDate not supplied

Both-bone forearm osteotomy for supination contracture: a cadaver model.

PURPOSE: To quantify the magnitude of rotational correction possible when comparing a single forearm bone osteotomy and fixation with stepwise osteotomy and fixation of both bones in a cadaver model and to determine if the order in which the stepwise osteotomies are performed influences the amount of correction. METHODS: Ten fresh-frozen cadaveric forearms were fixed to a frame positioned in the field of view of a motion-capture system. An experimental supination contracture was induced in full supination. Cadaver forearms were assigned randomly to group I (ulna osteotomy, rotation, plating) or group II (radius osteotomy, rotation, plating). Cadavers in group I were used later in group III (ulna + radius) by completing a radial osteotomy, rotation, and fixation in the forearms with the plated ulna. Similarly the specimens assigned to group II were used later in group IV (radius + ulna) by completing an ulna osteotomy, rotation, and fixation in the forearms with the plated radiuses. Measurements of forearm pronation were made after single-bone (groups I, II) and stepwise both-bone (groups III, IV) rotational osteotomies. RESULTS: Stepwise rotational osteotomy and fixation of the ulna followed by the radius produced significantly more corrective pronation (101 degrees) than rotating the radius followed by the ulna (65 degrees). Rotating the radius gave only moderate correction (58 degrees) and minimal correction was produced by ulna osteotomy alone (15 degrees). CONCLUSIONS: Rotational osteotomy of both forearm bones can create approximately 100 degrees of correction when performed at the proximal ulna followed by the distal radius. If less rotation is needed then the distal radius osteotomy alone can provide approximately 60 degrees of correction.

Biomechanical Phenomena↗

PubMed1999

A new methodology to measure load transfer through the forearm using multiple universal force sensors.

Previous approaches to measuring forces in the forearm have made the assumption that forces acting in the radius and ulna are uniaxial near the wrist and elbow. To accurately describe forces in the forearm and the forces in the interosseous ligament, we have developed a new methodology to quantitatively determine the 3-D force vectors acting in forearm structures when a compressive load is applied to the hand. A materials testing machine equipped with a six degree-of-freedom universal force-moment sensor (UFS) was employed to apply a uniaxial compressive force to cadaveric forearms gripped at the hand and humerus. Miniature UFSs were implanted into the distal radius and proximal ulna to measure force vectors there. A 3-D digitizing device was used to measure transformations between UFS coordinate systems, utilized for calculating the force vectors in the distal ulna, proximal radius, and the interosseous ligament (IOL). This method was found to be repeatable to within 3 N, and accurate to within 2 N for force magnitudes. Computer models of the forearm, generated from CT scans, were used to visualize the force vectors in 3-D. Application of this methodology to eight forearm specimens showed that the radius carries most of the load at the wrist while force in the IOL relieves load acting in the radius at the mid-forearm. For a 136 N applied hand force, the force in the IOL was 36 + 21 N. Advantages of this methodology include the determination of 3-D force vectors, especially those in the IOL, as well as computer generated 3-D visualization of results.

Biomechanical Phenomena↗

PubMed1999

In vivo motion analysis of forearm rotation utilizing magnetic resonance imaging.

OBJECTIVE: To analyse in vivo normal forearm rotation utilizing the image processing method on axial magnetic resonance imaging. DESIGN: Rotatory motion and translation of the radius and rotation of the ulna were analysed in vivo, utilizing features of the bone image; axial centre of gravity and axis of the bone. METHODS: Axial magnetic resonance images at the proximal, middle and distal portion of the right forearms of 20 healthy volunteers were examined in five rotational positions, maximum pronation, 45 degrees pronation, neutral, 45 degrees supination and maximum supination. The axis of forearm rotation, the rotation angle of the radius, the rotation of the radius around its axial centre of gravity, and the rotation of the ulna around its axial centre of gravity were calculated on these axial MR images. RESULTS: The radius rotates in a near-circular ellipse around its rotational centre located on a line through the radial head and the ulnar head from maximum supination to 45 degrees pronation. There was discrepancy between the calculated maximum rotational angle of the radius and the pronation-supination angle showed on the goniometer. This discrepancy was due to motion at the radiocarpal, midcarpal and carpometacarpal joints. The rotation of the ulna ranges within 6 degrees. At maximum pronation, there was palmar translation of the radius. CONCLUSIONS: The forearm rotation is not a simple rotatory motion but a complex motion with rotation and translation. The palmar translation of the radius at maximum pronation may be caused by incongruity of the distal radioulnar joint and contraction of the pronator quadratus muscle. RELEVANCE: To date there exist few methods for the accurate and non-invasive assessment for motion analysis of the forearm rotation. Such a technique utilizing magnetic resonance image characteristics is, however, helpful to reveal accurate self- and relative-rotatory motion of both radius and ulna as well as the translation movement on forearm rotation in normal forearm.

Adolescent↗

PubMed2003

Salvaging prosthetic dialysis fistulas with stents: forearm versus upper arm grafts.

OBJECTIVE: We compared results of angioplasty with those of concomitant stent placement to treat thrombosed forearm hemodialysis grafts with results for upper arm grafts. MATERIAL AND METHODS: Between October 1998 and July 2002, stents were deployed in 61 patients undergoing balloon angioplasty because of venous anastomotic stenosis causing graft thrombosis. Stents were used only in cases of inadequate angioplasty results. Twenty-three forearm grafts and 38 upper arm grafts were treated. All procedures were performed in an endovascular operating suite, with fistulography. Primary and secondary patency rates were analyzed and compared for graft location with the life table method. RESULTS: Grafts had undergone a mean of 1.56 previous revisions because of thrombosis (forearm: 1.52, upper arm: 1.58; P = NS). Excluding early thrombosis, a single graft infection was the only procedural complication. Cumulative primary patency rate at 3, 6, and 12 months (from stent placement) was 36.4%, 15.6%, and 0%, respectively, for forearm grafts, which was inferior to the 59.5%, 34.0%, and 17.0% primary patency rate observed for upper arm grafts (P =.0307) Secondary patency rate was 40.9%, 40.9%, and 30.7%, respectively, for forearm grafts, and 64.9%, 42.3%, and 19.7% for upper arm grafts (P = NS). CONCLUSION: Stent deployment can salvage thrombosed dialysis grafts. However, sustained patency occurs infrequently, with better results for upper arm grafts than for forearm grafts. Inasmuch as surgical revision of forearm grafts is usually straightforward, stenting should be reserved for use in high axillary grafts and other sites where surgical repair is difficult.

Adult↗

PubMed2003

Crosstalk in surface electromyography of the proximal forearm during gripping tasks.

Electromyographic (EMG) crosstalk was systematically analyzed to evaluate the magnitude of common signal present between electrode pairs around the forearm. Surface EMG was recorded and analyzed from seven electrode pairs placed circumferentially around the proximal forearm in six healthy individuals. The cross-correlation function was used to determine the amount of common signal, which was found to decrease as the distance between electrode pairs increased, but was not significantly altered by forearm posture (pronation, neutral, supination). Overall, approximately 40% common signal was detected between adjacent electrode pairs (3 cm apart), dropping to about 10% at 6 cm spacing and 2.5% at 9 cm. The magnitude of common signal approached 50% between adjacent electrode pairs over the extensor muscles, while over 60% was observed between neighbouring sites on the flexor aspect of the forearm. Although flexor and extensor EMG amplitude was similar, less than 2% common signal was present between flexor and extensor electrode pairs during both pinch and grasp tasks. Maximum grip force production was not affected by forearm rotation for pinch, but reduced 18% from neutral (mid-prone) to pronation during grasp (p=0.01). In spite of differences in grip force, mean muscle activity did not vary between the three forearm postures during maximum pinch or grasp trials. While this study improved our knowledge of crosstalk and electrode spacing issues, further examination of forearm EMG is required to improve understanding of muscle loading, EMG properties and motor control during gripping tasks.

Adult↗

PubMed1996

Role of endothelium in control of forearm blood flow in patients with heart failure.

We studied the role of endothelium in control of forearm blood flow during reactive and exercise hyperemia in patients with heart failure as well as in normal subjects. First, endothelium-dependent forearm vasodilation in response to acetylcholine (ACh), substance P, and endothelium-independent forearm vasodilation in response to sodium nitroprusside (SNP) were examined in patients with heart failure and in normal subjects. Endothelium-dependent forearm vasodilation in response to ACh but not to substance P was impaired in patients with heart failure. Endothelium-independent forearm vasodilation to SNP was also preserved in patients with heart failure. Second, the role of nitric oxide (NO) in reactive hyperemia and exercise hyperemia was examined in normal subjects using NG-monomethyl-L-arginine (L-NMMA), a blocker of NO synthesis. Results suggest that NO plays a minimal role in peak reactive hyperemia and exercise hyperemia in normal human forearm vessels. Finally, we determined if L-arginine, a precursor of NO, improves impaired endothelium-dependent vasodilation due to ACh and reactive and exercise hyperemia in patients with heart failure. L-Arginine augmented impaired ACh-induced vasodilation as well as reactive and exercise hyperemia in patients with heart failure. Our results suggest that defective endothelial function may contribute to abnormal control of forearm blood flow in patients with heart failure.

Acetylcholine↗