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Biomedical subjects

W W Shaw

Publications and source records attributed to W W Shaw.

At least 55 records · Page 3Linked to original sources
PubMed1994

Clinical experience with the 3M microvascular coupling anastomotic device in 100 free-tissue transfers.

The microvascular surgical anastomosis remains one of the most technically sensitive aspects of free-tissue transfers. To facilitate these often time-consuming, difficult anastomoses, various anastomotic coupling systems have been introduced. The 3M microvascular anastomotic coupling device, a polyethylene ring-pin device, was found to be highly successful in numerous animal studies. It has been available for use in human subjects for the last 4 years, but clinical experience remains sparse. Our clinical experience with the 3M coupler is reported in 100 free-tissue transfers. The average anastomotic time was 4 minutes. Mean follow-up was 8.6 months, and flap survival was 100 percent. The overall success rate for 3M (MACD) coupler use in microvascular anastomoses is 98.4 percent (121 of 123). Nine abandoned anastomoses were converted to sutured anastomoses intraoperatively. The over-all failure rate for 3M coupler anastomoses is 1.6 percent (2 of 123). We conclude that the 3M device is best suited for minimally discrepant, soft, pliable venous microvascular anastomoses and is unsuitable for end-to-side anastomoses in clinical situations. When carefully and selectively employed by a trained microvascular surgeon, the 3M coupler can be a safe, fast, and reliable adjunct for free-tissue transfers.

Adult↗
PubMed1994

Comparative silicone breast implant evaluation using mammography, sonography, and magnetic resonance imaging: experience with 59 implants.

With the current controversy regarding the safety of silicone implants, the detection and evaluation of implant rupture are causing concern for both plastic surgeons and patients. Our study obtained comparative value analysis of mammography, sonography, and magnetic resonance imaging (MRI) in the detection of silicone implant rupture. Twenty-nine symptomatic patients (total of 59 silicone implants) were entered into the study. Intraoperative findings revealed 21 ruptured implants (36 percent). During physical examination, a positive "squeeze test" was highly suggestive of implant rupture. Mammograms were obtained of 51 implants (sensitivity 11 percent, specificity 89 percent). Sonography was performed on 57 implants (sensitivity 70 percent, specificity 92 percent). MRI was performed on 55 implants (sensitivity 81 percent, specificity 92 percent). Sonographically, implant rupture is demonstrated by the "stepladder sign." Double-lumen implants may appear as false-positive results for rupture on sonography. On MRI, the "linguine sign" represents disrupted fragments of a ruptured implant. The most reliable imaging modality for implant rupture detection is MRI, followed by sonogram. Mammogram is the least reliable. Our study supports the clinical indication and diagnostic value of sonogram and MRI in the evaluation of symptomatic breast implant patients.

Breast Diseases↗
PubMed1994

Silicone breast implant ruptures in an animal model: comparison of mammography, MR imaging, US, and CT.

PURPOSE: To determine the most accurate imaging modality for detection of silicone implant ruptures. MATERIALS AND METHODS: Forty single-lumen silicone implants were surgically placed in 20 rabbits. Each rabbit received one intact and one ruptured implant and was examined with mammography, magnetic resonance (MR) imaging, ultrasound (US), and computed tomography (CT). Five radiologists reviewed all images in a random fashion and graded each for rupture. The radiologist who performed US also graded her impression during examination with US. Receiver operating characteristic (ROC) analysis was performed. RESULTS: MR imaging and CT were the most accurate modalities in detection of implant ruptures, with areas under the ROC curves (Az) of .95 and .91. Mammography and US were statistically significantly inferior, with Az of .77 for each (P < .05). CONCLUSION: MR imaging and CT are statistically more accurate than US and mammography for detection of intracapsular silicone implant ruptures when only the images are reviewed.

Animals↗
PubMed1994

Silicone breast implant rupture: comparison between three-point Dixon and fast spin-echo MR imaging.

OBJECTIVE: This study was designed to compare the three-point Dixon technique with our present MR protocol incorporating T2-weighted fast spin echo and fast spin echo with water suppression to detect ruptured silicone breast implants. SUBJECTS AND METHODS: Eighty-two symptomatic women with silicone breast implants were examined with both the three-point Dixon technique and fast spin-echo MR sequences. Of these patients, 41 had surgery to remove their implants. Four radiologists reviewed the images from only those patients who had surgery and graded each for rupture by using a scale of 1-5. Receiver-operating-characteristic analysis was performed. RESULTS: Of 81 implants removed, 18 were ruptured. Silicone implant ruptures were identified more frequently on the fast spin-echo sequence than on the three-point Dixon sequence, with areas under the ROC curves of .95 and .84, respectively. Although the difference was not statistically significant, the sensitivity for detecting silicone implant rupture was 89% for the fast spin-echo sequence and 61% for the three-point Dixon sequence. The specificity was 97% for both sequences. CONCLUSION: Silicone implant ruptures were detected more frequently with fast spin-echo MR sequences than with the three-point Dixon technique, although the difference was not significant. The greater spatial resolution used for the fast spin-echo sequence partially accounts for the difference in detection of implant ruptures in this study.

Breast↗
PubMed1994

Bilateral free flap breast reconstruction.

Bilateral mastectomies are relatively frequent. Free flaps from the abdomen, buttock, and lateral thigh can be used for simultaneous or staged reconstructions. The more extensive surgery is well rewarded by the permanent and gratifying results achieved. For patients unsuitable for implants or who have had failed implant reconstructions, such autologous tissue reconstructions are important alternatives.

Adult↗
PubMed1993

Definitive diagnosis of breast implant rupture using magnetic resonance imaging.

Breast implant rupture is an important complication of augmented and reconstructed breasts. Although several techniques such as mammography, xeromammography, ultrasound, thermography, and computed tomographic (CT) scanning have been proven to be useful to detect implant rupture, they have several disadvantages and lack specificity. In the current study, we have established magnetic resonance imaging (MRI) as a definitive, reliable, and reproducible technique to diagnose both intracapsular and extracapsular ruptures. The study was conducted in 100 symptomatic patients. Our imaging parameters were able to identify ruptures in implants with silicone shells. All the ruptures showed the presence of wavy lines, free-floating silicone shell within the gel ("free-floating loose-thread sign" or "linguine sign"). We had a 3.75 percent incidence of false-positive and false-negative results. The sensitivity for detection of silicone implant rupture was 76 percent, with a specificity of 97 percent. In addition, we also were able to identify the artifacts that may interfere with the definitive diagnosis of implant rupture.

Adult↗
PubMed1993

Silicone breast implants: US evaluation.

PURPOSE: To determine the value of breast ultrasonography (US) in the assessment of silicone breast implants for rupture. MATERIALS AND METHODS: Seventy-four women with local or systemic symptoms related to silicone implants underwent breast US. Of these, 28 underwent surgical removal of the implants. RESULTS: Of 57 implants removed, 37 were intact. The most reliable sign of an intact implant was an anechoic interior, although reverberation artifact and radical folds could be seen. Of 20 ruptured implants, 16 were intracapsular and four were extracapsular ruptures. The most reliable US sign of rupture was echogenic, horizontal ("stepladder") lines (14 of 20 ruptures). Two of the four extracapsular ruptures were accurately identified as echogenic nodules outside the implant; two were false-negative findings. Three intracapsular ruptures identified at US were false-positive; six were false-negative. Overall sensitivity for rupture was 70%, specificity was 92%, positive predictive value was 82%, and negative predictive value was 85%. CONCLUSION: Breast US is capable of depicting intracapsular and extracapsular rupture of breast implants.

Adult↗
PubMed1993

MR imaging of the breast in patients with silicone-gel implants: spectrum of findings.

Because of recent concerns about the potential dangers of rupture and leakage of silicone-gel implants, radiologists are often requested to evaluate the integrity of normal breast implants. Clinical studies suggest that MR imaging can accurately depict implant rupture. The purpose of this pictorial essay is to illustrate the spectrum of MR appearances of breasts in patients with silicone-gel implants. Types of prostheses range from the more common single-lumen silicone-gel implants to the rare foam-filled implants. Recognition of the variable appearance of intact implants is emphasized in order to distinguish these from intracapsular or extracapsular ruptures. Finally, we briefly review various investigational MR sequences designed to improve the evaluation of the integrity of silicone-gel implants and the localization of free silicone. This article is based on our experience in performing MR imaging in more than 350 patients with breast implants. In more than 50% of these patients, the MR imaging findings have been correlated with surgical and pathologic findings.

Adult↗
PubMed1992

Prefabrication of free flaps using the omentum in rats.

The omentum used as a vascular carrier is a new experimental model for prefabrication of free flaps in the rat. A 2.5 x 4 cm patch of omentum with gastroepiploic vessels and its rich vascular arcades was transferred under a bipedicled 2.5 x 6 cm right abdominal panniculocutaneous flap. At subsequent time intervals (postoperative days 0, 3, 5, 7, and 14), the skin pedicles were divided and the skin flap was raised as a composite island flap vascularized only by the underlying omental patch. The composite flap was then sutured back in place. Prefabricated flaps examined postoperatively demonstrated a dye fluorescence index (DFI) of 4.60% +/- 2.82% and 1.67% +/- 4.08% flap survival (FS) in the day 0 group; in the day 3 group, 9.83% +/- 1.47% of DFI and 15.00% +/- 10.35% of FS; in the day 5 group, 28.39% +/- 5.25% of DFI and 86.0% +/- 12.74% of FS (P less than 0.05); in the day 7 group, 38.19% +/- 7.52% of DFI and 98.13% +/- 3.72% of FS (P less than 0.05); and, in the day 14 group, 49.55% +/- 6.70% of DFI and 100% of FS (P less than 0.05). India-ink injection and histologic examination confirmed revascularization of the overlying skin by day 5.

Animals↗
PubMed1992

Computed tomography versus standard radiography in the assessment of fractures of the mandible.

Twenty-nine fractures of the mandible were studied by standard radiographs and axial computed tomographic scans (hard copy). Independent reviewers analyzed each study in a blinded, non-paired fashion. When radiographic diagnostic sensitivities were compared on the basis of known surgical findings, the plain films were found to have a higher diagnostic sensitivity (89%) than the hard copy computed tomograms (64%). This difference occurred primarily with images of nondisplaced fractures in posterior portions of the mandible, and is likely the result of tomographic orientation and volume averaging. Though computed tomography has emerged as the standard diagnostic test in evaluating intracranial and maxillofacial trauma, this study demonstrates that computed tomographic scanning alone is inadequate in excluding nondisplaced fractures of the posterior mandible.

Fracture Fixation, Internal↗
PubMed1992

Silicone breast implants in vivo: MR imaging.

This study was designed to evaluate pulse sequences and patient positioning for MR imaging of silicone breast implants in patients. One hundred forty-three patients (281 silicone implants) underwent imaging over a 21-month period. The combination of a T2-weighted fast spin echo technique (SE), T2-weighted fast SE with water suppression, and T1-weighted SE with fat suppression is recommended to reliably differentiate silicone from other breast tissues and to identify intracapsular and extracapsular ruptures or leaks. Seventy of the 143 patients underwent removal of their silicone implants. The sensitivity for detection of silicone implant rupture was 76%, with a specificity of 97%. Positioning the patient prone improved image quality.

Adult↗
PubMed1992

Principles of flap prefabrication.

Clinical flap prefabrication can be classified according to the basic technique of plastic surgery used for the prefabrication. There are currently three methods: (1) delay or expansion; (2) grafting; and (3) vascular induction by staged transfer. Illustrative cases are given to point out the advantages and indications for each method. A fourth, still experimental, method is based on cell biology advances that are looming on the horizon and may have revolutionary future clinical applications.

Adult↗
PubMed1992

Microvascular free flaps in breast reconstruction.

There is no longer any doubt that free flaps can achieve the best breast reconstruction. Proof is the rapidly increasing popularity of the method. Its many advantages, the indications for each flap, and the technical refinements are presented.

Female↗
PubMed1992

Monitoring of free flaps with surface-temperature recordings: is it reliable?

Surface-temperature recording (STR) is one of the oldest and simplest methods of postoperative monitoring of free flaps. Its usefulness, however, remains poorly documented, and its problems, not well understood. To assess its value, we reviewed our series of 600 consecutive free flaps where surface-temperature recording was the main method of monitoring used and a detailed temperature record was kept. Seventy flaps suffered a postoperative microvascular compromise necessitating a surgical reexploration. Of these, 62 charts were satisfactory for review and were matched with 62 charts from similar but uncomplicated flaps. The derived value C delta T, which represents the change in temperature difference (delta T) between flap and control sites over a specified time period, was calculated at each time point. Of 10,000 derivations, only once did C delta T greater than 1.8 degrees C fail to identify a microvascular thrombosis, and 17 times a false alarm was given. Therefore, when properly applied and interpreted, the sensitivity of surface-temperature recording is 98 percent, and its predictive value is 75 percent, making it a simple, inexpensive, and highly reliable technique of free-flap monitoring. The thermodynamics behind surface-temperature recording is reviewed, pointing out the pitfalls that have to be avoided in order to improve the reliability of this technique.

Humans↗
PubMed1991

Simultaneous comparison of pre- and post-microanastomotic hemodynamic profiles using a Tandem Doppler Probe.

The use of High-Frequency Pulsed Doppler Ultrasound (HFPDU) for evaluation of microvascular hemodynamics is well established. Due to technical limitations of existing probes, quantitation of anastomotic stenoses and detailed waveform analyses are difficult to perform and impractical for clinical use. We present a new Tandem Doppler Probe (TDP) for simple and accurate study of blood flow in vessels smaller than 1 mm in diameter. Its unique ability to compare the pre- and post-anastomotic waveforms simultaneously allows for quantitative detection of anastomotic narrowing of as little as 5%, as well as identification of subtle pathologic anastomotic waveform changes not seen with single probes. Such early and precise delineation of anastomotic problems in the operating room can provide an invaluable, objective assessment of the technical adequacy of the anastomoses as well as an important baseline for later post-operative monitoring of free-tissue transfers with implantable Doppler devices.

Anastomosis, Surgical↗
PubMed1991

A new technique for microvascular sleeve anastomosis.

This study describes our experience using an improved technique for microsurgical sleeve anastomosis of arteries. Modifications of previously described techniques include utilization of a sidecut and placement of the two stitches within separate vertical planes. In 40 arteries, we attained a patency rate of 97.5%. Histology, in vivo observation, and flow study using high-frequency pulsed ultrasound Doppler at 2 hr to 8 weeks demonstrate that the sidecut sleeve anastomosis shows patency and flow characteristics similar to those of standard end-to-end anastomosis, but with a dramatic decrease in operative time.

Anastomosis, Surgical↗