Biomedical subjects

Hung-Chi Chen

Publications and source records attributed to Hung-Chi Chen.

63 records · Page 4Linked to original sources

PubMed2002

Effect of exposure to cigarette smoke on microvascular reactivity to noradrenaline in cremaster muscles in rats.

This experiment was designed to study the effects of cigarette smoking on microvascular reactivity in an intact microvascular preparation. The vasoconstrictive responses of arterioles in rat cremaster muscles to topically applied noradrenaline were measured in 8 rats after a three-week period of inhaling cigarette smoke. A parallel set of experiments was in a control group of 8 rats for comparison. All three orders of arterioles in the muscles of rats exposed to smoke were significantly narrower than those of the controls (p < 0.0001). The dose response curve of all three orders of arterioles shifted to the right of their respective controls. The effective concentrations of noradrenaline to cause 50% vasoconstriction (EC50) of all three orders of arteriole was profoundly increased in rats that inhaled smoke compared with the control group (p < 0.05). We conclude that skeletal muscle arterioles in rats exposed to cigarette smoke may become hyposensitive to noradrenaline, or their degree of freedom from constriction may be reduced. Our results suggest that cigarette smoking is associated with significant functional alterations in the microcirculation.

Administration, Topical↗

PubMed2002

Microsurgical medialis pedis flaps for reconstruction of soft-tissue defects in the hand.

The medialis pedis flap (MPF) has been used for the reconstruction of soft-tissue defects in the hand since 1990. From January 1997 through January 2000, 19 patients (15 male, 4 female) with hand injuries underwent microsurgical MDF reconstruction at Chang Gung Memorial Hospital. There were finger injuries in 16 patients and palm defects in 3 patients. The mean patient age was 32.6 years (age range, 16-58 years). Flap size ranged from 4.5 x 2 cm to 7 x 6 cm (mean, 6 x 2.8 cm). Only one flap had partial loss. The donor site was closed primarily in 9 patients, and was closed using a split-thickness skin graft in 9 patients and a full-thickness skin graft in 1 patient. At a mean follow-up of 13 months, the protective sensation was 16 mm using the static two-point discrimination test and was 10 mm using the moving two-point discrimination test. Based on this retrospective study the authors conclude that (1) the MPF has the advantages of thin and glabrous skin, (2) the size of pedicle is compatible with the recipient vessel in the hand, (3) there is low donor site morbidity, and (4) achieving protective sensation is possible.

Adolescent↗

PubMed2002

Arteriovenous malformation involving the thumb and hand: radical excision and reconstruction of multiple components.

Arteriovenous malformation of the fingers is not an uncommon presentation in daily practice. The lesions may or may not become clinically evident from birth to adulthood. Treatment of the arteriovenous malformation includes conservative treatment, selective embolization, partial excision, and radical excision. However, recurrence, repeat operations, and even deformity requiring amputation are common problems. The excision is difficult because it is easy to damage the nutrient vessels of the digit, and ischemia or necrosis develop subsequently. Embolization and partial excision are prone to recurrence as well. Radical excision and flap reconstruction are beneficial for some patients, as demonstrated by the authors. In the treatment of digital arteriovenous malformation, it is always important to maintain a balance of cure, function, and aesthetic result.

Adult↗

PubMed2002

Combined anterolateral thigh flap and vascularized fibula osteoseptocutaneous flap in reconstruction of extensive composite mandibular defects.

Extensive composite defects of the oromandibular area are usually created after the surgical treatment of T3 and T4 cancers, requiring complex reconstructive plastic surgical procedures. The preferred treatment method for this type of defect is reconstruction with two free flaps. The use of the vascularized fibula osteoseptocutaneous flap for the bone and inner lining defect is well known and accepted. Among the flaps that can be used for the outer lining and soft-tissue reconstruction, the two most commonly used have been the forearm flap and the rectus abdominis myocutaneous flap. However, these flaps have some disadvantages that restrict their use for this purpose. The forearm flap is usually too thin to cover the fibular bone and reconstruction plate, and the rectus abdominis myocutaneous flap can cause a subclinical reduction in abdominal strength. Both radial forearm and rectus abdominis myocutaneous flaps are difficult to harvest during tumor excision. Because of these drawbacks, over the past several years the authors have preferred to use the anterolateral thigh flap for outer face, neck, and submandibular region reconstructions. From October of 1998 to June of 2000, 22 extensive composite mandibular defect reconstructions using the free anterolateral thigh flap, combined with the vascularized free fibula osteoseptocutaneous flap, were performed at the Chang Gung Memorial Hospital. Complete flap survival was 90.9 percent (40 of 44 flaps). Complete loss was seen in an anterolateral thigh flap, which was then reconstructed with a pectoralis major myocutaneous pedicled flap (2.3 percent). There were five venous problems: three in osteoseptocutaneous free fibula flaps, the other two in anterolateral thigh flaps; all were revised immediately. However, the skin islands of two osteoseptocutaneous free fibula flaps and one anterolateral thigh flap developed partial necrosis (6.8 percent). The other complications were compartment syndrome in the leg in one patient, external carotid artery rupture in one patient, three donor-site infections in two patients, three neck wound infections, and one myocardial insufficiency; all were treated properly. Thirteen patients underwent revision procedures 6 months after the first operation. These procedures included debulking of the flap or revision of the mouth angle or both. Trismus or intraoral contraction was noted in none of these patients. In conclusion, the free anterolateral thigh flap combined with the vascularized fibula osteoseptocutaneous flap seems to be a good choice in the reconstruction of the extensive composite defects of the oromandibular region aesthetically and functionally.

Aged↗

PubMed2002

The reconstructive strategy for improving elbow function in late obstetric brachial plexus palsy.

Children with previously untreated obstetric brachial plexus palsy frequently have abnormal elbow function because of motor recovery with aberrant reinnervation, or because of paresis or paralysis. From 1988 to 1997 (9-year period), 62 children with obstetric brachial plexus palsy with resulting elbow deformity underwent various methods of palliative reconstruction to improve elbow function. For motor recovery with aberrant reinnervation, release of aberrantly reinnervated antagonistic muscles and augmentation of paretic muscles form the basis of surgical intervention. The surgical procedures included triceps-to-biceps transfer, biceps-to-triceps transfer, brachialis-to-triceps transfer, or combined biceps- and brachialis-to-triceps transfer. Choice of procedures was individualized and randomly determined on the basis of the degree and pattern of aberrant reinnervation between elbow flexors and extensors. In patients' motor recovery with paresis or paralysis, persistently weak elbow flexion was salvaged with a functioning free muscle transplantation or Steindler's flexorplasty, or regional shoulder muscle transfer. In addition, patients with aberrant reinnervation between shoulder abductors and elbow flexors underwent anterior deltoid-to-biceps transfer with a fascia lata graft. All patients had a minimum follow-up of 2 years. Results are assessed and discussed and a reconstructive algorithm is recommended. In general, reconstruction of elbow extension should precede that of elbow flexion. Biceps-to-triceps transfer with preservation of an intact brachialis muscle, or brachialis-to-triceps transfer with preservation of an intact biceps, allows 50 percent of these patients to achieve acceptable elbow flexion and extension in a single-stage procedure.

Adolescent↗

PubMed2002

Reconstruction of through-and-through cheek defects involving the oral commissure, using chimeric flaps from the thigh lateral femoral circumflex system.

Repairing full-thickness cheek defects involving the oral commissure in the head and neck regions after tumor resection is a challenge for reconstructive surgeons. First, they are usually relatively large defects. Second, the axes of the cheek and intraoral lining are different from each other. Third, the shape and volume of the defect and the oral sphincter should be considered individually. Lateral femoral circumflex perforator flaps with at least two independent cutaneous perforators are suitable for reconstruction of such a defect in one stage. In this study, between January and December of 1999, a total of nine patients underwent reconstruction with chimeric lateral femoral circumflex perforator flaps immediately after resection of their oral cancers. The average age of the patients was 61 years (range, 42 to 74 years). The oral lining defects were between 5 x 5 cm and 6 x 12 cm in size, whereas the cheek defects were between 5 x 6 and 8 x 12 cm. Fifteen flaps were supplied by one perforator, and three flaps were supplied by two perforators. There were nine single arterial anastomoses, eight single venous anastomoses, and one double venous anastomosis. There were no total flap failures. One case of postoperative venous congestion was successfully treated by a second venous anastomosis. The average duration of hospitalization was 31.8 days (range, 18 to 49 days). The median follow-up time was 8.6 months, and all patients were alive at the time of evaluation. Six of nine patients had satisfactory or good contours of the cheek. Five of nine patients had normal deglutition. Six of nine patients had adequate oral continence. Compared with other free flaps, use of the combined (chimeric) lateral femoral circumflex perforator flaps for the reconstruction of cheek through-and-through defects involving the oral commissure has several advantages: (1) easy three-dimensional insetting, (2) a unique character suitable for the requirements of the oral lining and cheek skin to achieve good aesthetic appearance, (3) functional preservation of the oral sphincter and the resistance of gravity by use of the tensor fasciae latae, (4) minimal donor-site morbidity, (5) economic design, and (6) no need for microsurgical fabrication, because major vascular branches such as the transverse branch, the ascending branch, and the feeding branch to the rectus femoris muscle are not sacrificed in the procedure. The disadvantages of these flaps include (1) the complicated anatomy of the perforators, (2) the learning-curve requirement for their use, and (3) the occasional need for secondary venous drainage and shifts to double flaps. Although there are some difficulties, it was concluded that use of the chimeric lateral femoral circumflex perforator flaps in the selected cases is one of the good options available for the reconstruction of cheek through-and-through defects involving the oral commissure.

Adult↗

PubMed2002

Formation of independently revascularized bowel segments using the rectus abdominis muscle flap: a rat model for jejunal prefabrication.

Reconstruction of the pharyngoesophagus with free jejunal transfer is a major challenge when recipient neck vessels are absent because of previous surgery or irradiation. In such instances, jejunal transfer using a muscle flap as a "vascular carrier" may be a problem-solving alternative. Pretransfer vascularization of the jejunum is achieved by wrapping the muscle flap around the small bowel segment. After a short staging period, the mesenteric pedicle is divided and the bowel segment is transferred up to the neck based on its new blood supply. The objectives of this study were to develop an animal model for prefabricating independently revascularized jejunal segments using the rectus abdominis muscle flap and to determine the minimal time required for independent bowel survival. Twenty-four mature (500-g to 700-g) rats were divided into six experimental groups of four animals each. In each animal, a 1.5-cm segment of proximal jejunum was isolated on two jejunal arteries and wrapped with a superior pedicled rectus abdominis muscle flap. To determine the time of neovascular takeover, the mesenteric pedicles were ligated on postoperative day 2 (group I), day 3 (group II), day 4 (group III), day 5 (group IV), day 6 (group V), and day 7 (group VI). At the time of pedicle ligation, the composite flap was transposed to a new subcutaneous position. Viability of bowel was assessed according to gross appearance and histologic examination 48 hours after transfer. Complete survival of revascularized jejunum in 11 of 12 animals was obtained after pedicle ligation on postoperative day 5 and beyond (p < 0.0001, Fisher's exact test). These bowel segments demonstrated luminal patency, intact pink mucosa, mucus production, and visible peristalsis. Histologic examination showed healthy intestinal epithelium and tissue integration along the serosa-muscle interphase. In contrast, pedicle ligation on day 4 and earlier resulted in varying degrees of bowel necrosis characterized by flattening or ulceration of mucosa (day 4), mucosal sloughing and necrosis of mural musculature (day 3), and complete loss of bowel architecture with lumen obliteration (day 2). These findings suggest that jejunal segments may be independently revascularized with the rectus abdominis muscle flap in the rat model. Complete survival and gross normal bowel function may be obtained without mesenteric perfusion after a minimal time of 5 days.

Abdominal Muscles↗

PubMed2002

Surgical strategy for improving forearm and hand function in late obstetric brachial plexus palsy.

For the purpose of treatment, obstetric brachial plexus palsy can be subdivided into two distinct phases: initial obstetric brachial plexus palsy, and late obstetric brachial plexus palsy. In the latter, nerve surgery is no longer practical, and treatment often requires palliative surgery to improve function of the shoulder, elbow, forearm, and hand. Late obstetric brachial plexus palsy in the forearm and hand includes weakness or absence of wrist or metacarpophalangeal or interphalangeal joint extension; weakness or absence of finger flexion; forearm supination, or less commonly pronation contracture; ulnar deviation of the wrist; dislocation of the radial or ulnar head; thumb instability; or sensory disturbance of the hand. Palliative reconstruction for these forearm and hand manifestations is more difficult than for the shoulder or elbow because of the lack of powerful regional muscles for transfer. This report reviews the authors' experience performing more than 100 surgical procedures in 54 patients over a 9-year period (between 1988 and 1997) with a minimum of 2 years' follow-up. Surgical treatment is highly individualized, but the optimal age for forearm and hand reconstruction is usually later than for shoulder and elbow reconstruction because of the requirement for a preoperative exercise program. Multiple procedures for forearm and hand function were often performed on any given patient. Frequently, these were done simultaneously with reconstructive procedures for improving shoulder and/or elbow function. Traditional tendon transfer techniques do not provide satisfactory reconstruction for those deformities. Many of the authors' patients required more complex techniques such as nerve transfer and functioning free-muscle transplantation to augment traditional techniques of tendon and/or bone management. Sensory disturbance of the forearm and hand in late obstetric brachial plexus palsy seems a minor problem and further sensory reconstruction is unnecessary.

Adolescent↗

PubMed2002

Technique and strategy in anterolateral thigh perforator flap surgery, based on an analysis of 15 complete and partial failures in 439 cases.

The free anterolateral thigh flap is becoming one of the most preferred options for soft-tissue defect reconstruction. Between June of 1996 and August of 2000, 672 anterolateral thigh flaps were used in 660 patients in Chang Gung Memorial Hospital. A total of 439 flaps were cutaneous or fasciocutaneous flaps based on musculocutaneous perforators. The analysis of the flap failures was done only in this perforator series. In six cases, no suitable skin vessel was found during the dissection of the flaps. The complete success rate was 96.58 percent (424 of 439). Of the 15 failure cases, eight were complete and seven were partial (10 percent to 60 percent of the flap). Thirty-four flaps were reexplored, and 19 (56 percent) were salvaged. In this study, some of the reasons for the flap failure, unique to the anterolateral thigh perforator flap, were identified. They include inadvertent division of perforator at the fascial plane as a result of inadequate knowledge of perforator anatomy, inadvertent injury to the perforator during intramuscular dissection (noted by the surgeon or ignored) as a result of inexperience, and twisting of the pedicle during inset of the flap at the recipient site. Technical pearls in the harvest of the anterolateral thigh perforator flap are as follows: mapping of the skin vessels with a Doppler probe before flap design, meticulous dissection of the perforator under surgical loupe or even lower-magnification microscope, inclusion of a small fascia cuff around the perforator, and intermittent topical use of Xylocaine during the intramuscular dissection of the perforators. During reexploration, one must search for twisting of the pedicle and small bleeders from the branches of the intramuscular perforators.

Adolescent↗