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Biomedical subjects

W W Shaw

Publications and source records attributed to W W Shaw.

At least 19 recordsLinked to original sources
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↗
PubMed1991

Laser-assisted venous anastomosis: a comparison study.

A low-powered carbon dioxide laser was used to perform 25 vein grafts (50 anastomoses) on the femoral veins of Sprague-Dawley rats. The patency rate, clamp time, and bleeding time were compared with 50 conventional microvascular vein grafts (100 anastomoses). The patency of the laser-assisted anastomoses (LAVA) was 84 percent, while the conventional vein grafts yielded a 94 percent patency rate. The average clamp time and bleeding time for the LAVA were 47.2 min and 4.88 sec, respectively, while the conventional anastomoses required 57.6 min and had an average bleeding time of 9.44 sec. Histologically, both specimens healed at the same rate, but the laser-assisted anastomoses produced less inflammation and granulation tissue. These results suggest that the laser has potential as a tool for clinical application in microsurgery. In addition, the 94 percent patency rate achieved with the vein interposition graft would suggest that a decrease in the tension across the anastomosis can improve patency.

Anastomosis, Surgical↗
PubMed1991

The fasciovascular pedicle for revascularization of other tissues.

A fasciovascular pedicle based on the epigastric vessels was developed in a rat model to determine if it could be used as a "universal carrier" to revascularize a new composite flap. The effects of time course, carrier size, and flap ischemia on the revascularization process were studied. A 2.5 x 4-cm or 1 x 4-cm fascial patch pedicled on the vessels was transferred under bipedicled 2.5 x 4-, 6-, or 8-cm abdominal panniculocutaneous flaps. At different time intervals, the flap was raised as an island flap connected only by it vascular bundle and then sutured back in place. The skin perfusion by dermofluorometry and flap survival were both markedly increased on day 5 (p less than 0.001). The wide carrier had a 93% survival area, whereas the narrow carrier had only 71%. The wide carrier induced relatively faster and better revascularization (p less than 0.05). Moderate ischemia promoted revascularization (p less than 0.01). An india ink injection study and histological examination provided visual evidence of revascularization. This fasciovascular pedicle is a promising model for prefabrication of complex new composite flaps and for studying the process of revascularization between the layers. Based on these findings and further investigations, a thin, prefabricated abdominal free flap was successfully transferred for facial resurfacing in humans.

Abdomen↗
PubMed1991

The role of microvascular free flaps in salvaging below-knee amputation stumps: a review of 22 cases.

Twenty-two cases of traumatic below-knee amputation stumps with inadequate soft-tissue coverage salvaged with microvascular free flaps were reviewed retrospectively. All patients would have required an above-knee amputation for prosthesis fitting had microvascular free flaps not bee utilized. A total of 24 flaps were used in 22 patients; parascapular 11 (46%), foot filet six (25%), latissimus dorsi four (17%), lateral thigh, tensor fascia lata, and groin one (4%). Free flaps were performed immediately after injury in five (21%) cases, within the first week in two (8%), between 1 and 3 months in 12 (50%), and after 3 months in five (21%). Fifty per cent of the patients had significant other injuries. The patients had a total of 107 operations (mean, 4.9) related to their injury: 33 (mean, 1.5) of those operations were after the free flap, 27 (25%) of which were either performed because of a complication of the free flap or for revision of the free flap. Complications included partial necrosis in five (21%), neuroma in three (13%), hematoma in two (8%), donor site complication in two (8%), thrombosis requiring reoperation in one (4%), and flap failure in one (4%). Patient followup ranged from 12 to 116 months. All patients maintained a functional below-knee prosthetic level. The mean time to ambulation was 5.75 months, and was not significantly affected by flap complications. Most patients employed before their injury were employed after their injury. Despite a protracted course in these severe injured trauma patients, a functional below-knee amputation level was preserved in all cases utilizing microvascular free flaps.

Activities of Daily Living↗
PubMed1991

Prefabrication of composite free flaps through staged microvascular transfer: an experimental and clinical study.

The feasibility of prefabricating free flaps by inducing, through the process of staged reconstruction, an arteriovenous bundle and its surrounding fascia to perfuse a selected block of tissue was investigated experimentally and clinically. Sixteen rat knee joints were wrapped with their ipsilateral superficial inferior epigastric (SIE) fascia. In 8 joints, the composite flaps were resected en bloc and were immediately replaced orthotopically pedicled upon the superficial inferior epigastric vessels. In the remaining joints, the resection and orthotopic transfer were performed 2 weeks later. Only the joints in the latter group, which benefited from the staging period, were found to be perfused. The long finger proximal interphalangeal joint of a child was reconstructed by the staged microvascular transfer of his second toe proximal interphalangeal joint. At the first stage, a temporalis fascia flap was wrapped around the toe proximal interphalangeal joint and revascularized to the dorsalis pedis vessels. Six weeks later, the joint and its temporalis fascia envelope were dissected, and the "prefabricated" joint flap was transferred to the hand and revascularized to the wrist vessels. Bony union progressed uneventfully with excellent recovery of the range of motion. We conclude that regardless of the indigenous vascular anatomy, an unlimited array of composite free flaps can be constructed and transferred based on induced large vascular pedicles.

Animals↗
PubMed1989

Reconstruction of the lower extremity with microvascular free flaps: a 10-year experience with 304 consecutive cases.

A retrospective review of 304 consecutive microvascular free flaps to the lower extremity was done to identify the patterns of usage, results, and problems. The most common indication (91%) was for the replacement of extensive tissue loss caused by motor-vehicle injuries. Most of the defects were below the mid-tibia (73%). The associated compound fractures were predominantly gradable as Gustilo type IIIb&c. The latissimus dorsi, the rectus abdominus, and the scapular skin were the flaps used most commonly for coverage (77%). The overall flap failure rate was 8%, compared with 3% for our series of non-lower extremity cases, and 0% for the non-traumatic lower extremity cases. The magnitude of the traumatic insult was the most significant factor associated with anastomotic failure. The rate of anastomotic thrombosis doubled in the presence of vascular trauma, increased threefold in the presence of larger bony defects, and increased fivefold when vein grafts were needed. Experience was important in reducing the complications and improving the results. Fourteen patients (6%) underwent an amputation within the first 3 months, ten of them because of flap failure. Of 85 patients followed up for over one year, 91% had recovered good to excellent leg function. The ability to add healthy and well vascularized tissue to the traumatized limb is critical for the achievement of: 1) early definitive wound healing and restoration of function; 2) salvage of many impending amputations; 3) better prosthetic stump reconstructions; 4) better esthetic results.

Amputation, Surgical↗
PubMed1988

Vasoactive prostaglandins in the impending no-reflow state: evidence for a primary disturbance in microvascular tone.

The impending no-reflow (NRF) state was studied in the rat hindlimb to identify possible biochemical mediators producing the no-reflow phenomenon. After 5 hours of ischemia, the venous effluents draining the ischemic limb and the contralateral nonischemic limb were collected for three 30-minute time periods. Thromboxane B2 (TxB2), prostaglandin E2 (PGE2), and 6-ketoprostaglandin F1 alpha, the stable metabolite of prostacyclin (PGI2), were measured by radioimmunoassay. Venous outflow rate, distal skin perfusion assessed by dermofluorometry, and histology of muscle and skin were examined in control limbs, ischemic limbs, and limbs with impending no reflow. The no-reflow state was characterized by a significantly decreased venous outflow (less than 0.01 ml per minute), decreased skin perfusion (index of fluorescence of 15 percent in no-reflow limbs versus 70 percent in reflow limbs), and absence of thrombosis of the vasculature. The no-reflow state also was associated with 2.4 times more thromboxane B2 and 1.5 times more 6-ketoprostaglandin F1 alpha than that observed in ischemic limbs with reflow. The biosynthesis of vasodilating prostaglandin E2 in the no-reflow state, however, was only 40 percent of the prostaglandin E2 measured in limbs with reflow. We propose that the impending no-reflow state may reflect a state of global microcirculatory "agonal" vasoconstriction, most probably due to an overabundant release of the vasoconstrictor thromboxane relative to the vasodilating prostaglandin E2 and prostacyclin. The likelihood of specific biochemical mechanisms producing the no-reflow state suggests that pharmacologic agents may be able to reverse the impending no-reflow state to improve tissue survival.

6-Ketoprostaglandin F1 alpha↗
PubMed1987

A historical perspective on the changing methods of management for major trauma of the lower extremity.

The quantity of severe injuries to the extremities challenging the modern, civilian surgeon cannot compare with that produced at Gettysburg or other battles of the Civil War. Nonetheless, the extent and severity of the trauma to the extremity generated on our "civilian battlefields" match and often surpass the wounds confronted by our predecessors. In the Civil War, as it had been for many preceeding years, amputation remained the dominant approach to managing a great variety of injuries to the extremities. However, constant surgical progress, as reflected by a gradual reduction in recourse to amputation, had enabled each succeeding generation of surgeons to surpass and distance themselves from their predecessors. Amputation of the traumatized extremity had always defined and continues to represent the prevalent abilities and limitations of conservative and reconstructive surgical efforts. Operative treatment, for much of its existence, represented a collection of dangerous ablative procedures which were used reluctantly when all other measures were exhausted. Its transformation into a successful reconstructive endeavor evolved primarily in this century. The understanding of bone healing and the functional importance of the knee joint led to a transformation in amputation and to changes in the management of fractures which are still evolving. The next revolution in operative treatment came with the ability to restore blood flow in injured extremities. Finally, the recent introduction of a variety of free flaps enables the reconstitution of extensive soft tissue and bony defects and further lowers the number of obligatory amputations. These innovations enabled the surgeon to reduce his or her recourse to amputation of severely injured extremities. Nonetheless, the significant number of amputations still performed constitute a reminder that there is still work to be done.

Amputation, Surgical↗
PubMed1987

Vascularized calvarial flaps.

Vascularized calvarial transfers offer many advantages. In this article the anatomic (soft tissue, vascular, osseous) basis of flap design is summarized, and the technical details of two calvarial flaps, the temporoparietal and the frontoparietal, are presented.

Adult↗