The vascularization of the median nerve in the distal forearm and its potential clinical importance.

PURPOSE: The aims of this anatomical study were to identify any extrinsic blood supply to the median nerve in the distal forearm and to measure the tension required to approximate the severed nerve after and before dissecting it while maintaining its extrinsic blood supply. METHODS: We injected the arterial system of 15 lightly embalmed forearms with red latex to define the vascular anatomy of the median nerve in the distal forearm. We measured the gap resulting from spontaneous retraction of the cut ends of the divided median nerve and the average tension needed to reapproximate the ends before and after resection of the attachments to the nerve on its superficial, deep, and ulnar aspects. RESULTS: A constant branch to the median nerve arises from the radial artery approximately 5 cm proximal to the radial styloid process. The mean gap between the severed nerve ends was 1.2 cm (range, 0.9-1.7 cm). The mean tension required to coapt the nerve ends was 231 g force (range, 200-280 g), reducing to 89 g force (range, 60-110 g) when only its radial attachments, including this vessel, were preserved. CONCLUSIONS: This cadaveric study suggests that it may be possible to advance the median nerve at the wrist while retaining the vascular connection and blood supply from the radial artery, and so maintain the vascularity of the nerve at the common site of nerve repair in the distal forearm. CLINICAL RELEVANCE: This cadaveric study identifies constant arterial feeding branches from the radial artery to the median nerve in the distal forearm, and is a preliminary investigation into the possibility of advancing the median nerve for repair in the distal forearm while maintaining the continuity of this branch.

Managing the outer limits of reconstruction with microsurgical free tissue transfer.

Six patients had major deficits reconstructed with microsurgical free tissue transfer. In contrast to some opinions that free tissue transfer is a "method of last resort," these patients were selected for microsurgical reconstruction as a method of first choice due to the qualities desired in the reconstruction, the reliability of the technique, and the desire to minimize the functional or aesthetic deficit at the donor site. Microsurgical techniques allowed a reconstruction in these cases that would have been difficult or impossible by conventional techniques, while they markedly improved the quality and reliability of the reconstruction and decreased the donor morbidity. Microsurgical free tissue transfer has been reported to have a success rate of 94% in centers where a significant volume of surgery is done. We believe the continued refinement of microsurgical techniques and their increased application will improve the results of reconstruction in a large category of severe traumatic and cancer defects.

Anatomic study of the collateral blood supply of the sternum.

A microdissection study was carried out on ten injected, cleared human sternal specimens. Three types of vessel were identified that have the potential to carry blood to the sternum after mobilization of the internal thoracic artery (ITA): (1) branches of the ITA that supply both the sternum and the pectoralis major ("sternal/perforating branches"), (2) branches of the ITA that supply both the sternum and an adjoining intercostal space ("sternal/intercostal branches"), and (3) posterior intercostal arteries that do not anastomose with an ITA branch but continue past the ITA to reach the sternum. All three types of vessel were found more frequently in the proximal than in the distal half of the sternum. For sternal/perforating and sternal/intercostal vessels to function as collaterals after ITA bypass grafting, their short common trunks of origin must remain intact. The data support the recommendation that the branches of the ITA be ligated as close as possible to the ITA itself to preserve collateral blood flow to the sternum.

Microsurgical two-layer vasovasostomy: word of caution.

Microsurgical technique, with separate mucosal and muscular layer anastomosis, recently has been advocated as the most successful method of vasovasostomy. Unexpected difficulties may be encountered using this method; moreover, considerable practice in the microsurgical laboratory is mandatory before actual performance of the procedure. As with any innovation in surgical technique, a judgment of the clinical superiority of the two-layer anastomotic method must await substantiating results from other investigators.

PIP: A microsurgical technique, with separate mucosal and muscular layer anastomosis, has been advocated as the most successful vasovasostomy method presently available. But the 2-layer microsurgical vas anastomosis has aspects that are foreign both to the urologist and to the experienced microvascular surgeon, and suggestions are made for mastering this microtechnique. For the urologist, practice on sheet rubber edges followed by vessel anastomosis in small animals are prerequisite to successful surgical outocme. For the microvascular surgeon, certain changes must be made from usual practices because of the stiffness, thickness of wall, and small size of lumen compared with the outer diameter of vas deferens. A summary of attempts made at 2-layer anastomosis suggests that the 2-layer method in a laboratory model appeared superior to a single-layer method. Final judgement of superiority of this 2-layer technique cannot be pronounced.

Microsurgical two-layer vasovasostomy: laboratory use of vasectomized segments.

A microsurgical laboratory model is described which uses optimally preserved human vasectomy segments. These preserved specimens retain their natural appearance and handling qualities, permitting ready availability of material for practice, which is mandatory before clinical performance. If laboratory facilities are not available, the model can be used for practice in a convenient area of the operating suite.

Comparison of the effects of commonly used wound agents on epithelialization and neovascularization.

BACKGROUND: The primary effect sought with most topical wound therapy is antimicrobial. Topical wound agents are thought to promote normal healing by protecting the wound from infection. In this study, we examined the effect of six commonly used topical wound agents (bacitracin, sodium hypochlorite, silver nitrate, silver sulfadiazine, mafenide acetate, and povidone-iodine) on epithelialization and neovascularization in noninfected wounds. For this study, a new wound model was used in which direct visualization and quantification of wound epithelialization and neovascularization were carried out throughout the entire healing process. STUDY DESIGN: We measured the effect which 500 U per g of bacitracin, 0.25 percent of sodium hypochlorite, 0.5 percent silver nitrate, 1 percent silver sulfadiazine, 8.5 percent mafenide acetate, and 10 percent povodione-iodine had on the rate of wound epithelialization and neovascularization. The agents were applied topically to 99 circular full-thickness wounds (2.25 mm diameter, 0.125 mm depth) created on the dorsum of male hairless mouse ears. This model enabled us to visualize and measure directly wound epithelialization and neovascularization repeatedly throughout healing, using intravital video microscopy and computerized digitized planimetry. RESULTS: Control wounds and wounds treated with silver sulfadiazine (n = 18) and mafenide acetate (n = 14) epithelialized in 7.2 +/- 0.7, 7.1 +/- 0.3, and 7.3 +/- 0.3 days, respectively. This was significantly (p < 0.01) faster than the wounds treated with povidone-iodine (n = 10), sodium hypochlorite, (n = 8), and bacitracin (n = 13). Wounds treated with povidone-iodine epithelialized the slowest (11.8 +/- 0.55 days). Wound neovascularization was completed most rapidly in the groups treated with povidone-iodine and silver sulfadiazine (15.0 +/- 0.4 and 15.3 +/- 0.7 days, respectively). This was significantly (p < 0.05) faster than wounds treated with silver nitrate (n = 15), which neovascularized in 18.4 +/- 0.56 days. One-half of the wounds treated with sodium hypochlorite (eight of 16) did not epithelialize or neovascularize. CONCLUSIONS: The various antimicrobial agents studied in our in vivo model affect wound epithelialization and neovascularization differently. These effects on these two very important aspects of healing should be taken into consideration when indicating a specific agent for treatment of different types of wounds.

Histopathological changes following removal of the perineurium.

Using microsurgical techniques, the perineurial sheath was stripped off the sciatic nerves of rats over a 0.5 cm length at a point where the nerve consists of a single fascicle. The nerves were excised 0 to 84 days after the injury, and were examined in semi-thin transverse section. A new sheath, closely resembling normal perineurium, became organized during the first 10 days; it appeared uniformly over the length of the injured segment. The new perineurial sheath was probably formed by endoneurial fibroblasts migrating from within the fascicle. In undamaged specimens, the asons immediately beneath the excised perineurium underwent no degenerative changes.

Experimental study of the regenerative potential of perineurium at a site of nerve transection.

A single fascicle of sciatic nerve was transected in a series of rats. The nerve was repaired by one of three experimental models: 1) perineurial suturing with bulging axons untrimmed. 2) perineurial suturing with bulging axons trimmed, and 3) perineurial suturing to produce a misaligned fascicle. Nerves were excised at 0 to 42 days and were examined in thin, longitudinal section. The complete absence of perineurial regeneration was observed at all time intervals and in all models. Regeneration of axons within the fascicle was disordered. Axonal regeneration extended into the surrounding connective tissue and infiltrated both the proximal and distal perineurium.

Immediate reconstruction of oral cavity and oropharyngeal defects using microvascular free flaps.

Eighteen patients underwent immediate reconstruction of defects involving the oral cavity and oropharynx with free groin and dorsalis pedis flaps. One partial and four complete failures occurred. In the successfully reconstructed patients, the functional results were equal to conventional flaps while the cosmetic improvements were dramatic.

Mandibular reconstruction with microvascular bone transfer. Series of 10 patients.

Mandibular reconstruction with microvascular bone transfer was carried out in 10 patients, including 8 with far advanced intraoral carcinoma and 2 with posttraumatic facial and mandibular defects. Eight patients presented with compromised defects as a result of radiation injury, infection, and scarring. Nine patients experienced primary bony union with complete functional and esthetic reconstruction of the mandible, and two patients eventually received dentures. This technique has resulted in a more effective, more reliable, and earlier reconstruction compared with conventional methods.

Omental transposition for low pelvic anastomoses.

Surgeons' opinions differ regarding the role of the omentum in low pelvic intestinal anastomoses. This study was undertaken to define the anatomy and surgical technique of omental transposition to the pelvis. We studied 45 cadavers to elucidate surgical aspects of omental mobilization, lengthening, and transposition into the pelvic cavity. In addition, intraoperative studies of omental transposition to the pelvis were performed in 20 patients with chronic ulcerative colitis, familial adenomatous polyposis, and rectal cancer who were undergoing ileal J-pouch anal anastomosis or low anterior resection. The most important anatomic variables for omental transposition are three variants of arterial blood supply: (1) In 56% of patients, there is one right, one (or two) middle, and one left omental artery. (2) In 26% of patients, the middle omental artery is absent. (3) In the remaining 18% of patients, the gastroepiploic artery is continued as a left omental artery but with various smaller connections to the right or middle omental artery. The first stage of omental lengthening is detachment of the omentum from the transverse colon mesentery. This must be performed carefully, as the omentum is closely adherent to the right transverse mesocolon. The second stage is the actual lengthening of the omentum. The third stage is placement of the omental flap into the pelvis. Creation of an omental pedicle is a simple surgical procedure. This procedure can be performed quickly, does not involve significant blood loss, and may reduce the frequency of complications after low pelvic anastomoses.

Microvascular free tissue transfer in head and neck and esophageal surgery.

Successful reconstruction for excisional defects of the head and neck and esophagus was accomplished in 93 percent of our patients using microvascular free tissue transfer. Complete failure occurred in 7 percent of the patients. Major defects after head and neck cancer surgery constituted the main indication for use of microvascular free tissue transfer for reconstruction. Ninety-four percent of the patients had undergone an extensive excisional procedure. A wide range of cutaneous, myocutaneous, and osteocutaneous free flaps, as well as free bowel autotransfers were used. Complete failure was three times higher in the previously irradiated patients (4 of 41 patients) compared with nonirradiated patients (1 of 34 patients). Morbidity and mortality rates were consistent with expected ranges in patients who were undergoing major head and neck resection. Donor site complications occurred in 23 percent. Thin flaps are favored for reconstruction of anterior defects in the oral cavity, whereas bulkier flaps are more suitable for deeper defects in the oropharynx and hypopharynx. The advantages are both aesthetic and functional. The free jejunal autograft is considered the reconstructive method of choice for defects produced by laryngopharyngoesophagectomy. Highly developed and sophisticated microsurgical skills continue to be the mainstay of success. The implication of free tissue transfer failure, especially for defects of the upper aerodigestive tract, are impressive in terms of morbidity, mortality, and cost. These considerations limit the application of this method of reconstruction to centers that have sophisticated and productive reconstructive surgeons with microsurgical skills.

Refinements in lower extremity free flap surgery.

This chapter recommends numerous factors that are significant refinements in approach and execution of lower extremity free flaps. I encourage a clear conceptual separation between the two essential phases of successful reconstruction of problem wounds: wound preparation and flap transfer. I have found that antibiotic beads maintain the sterility of temporary bony dead space. Due emphasis should be given to preparation of the surgeon, patient, and wound, allowing a nonemergency approach to lower extremity free flap coverage. The surgeon needs to be familiar with a variety of flaps beyond the usual workhorse group. Also, attention should be paid to perioperative warmth and hydration, and vessels affected by posttraumatic vessel disease must be avoided. A positive attitude toward the use of vein grafts whenever necessary is important. I also favor careful planning of the exact size and shape of the flap and length of the vessels along with use of a widely spatulated technique of end-to-side anastomoses.

Microsurgical adjuncts in salvage of the ischemic and diabetic lower extremity.

Revascularization of distal occlusive disease in the diabetic has been markedly enhanced by microsurgical techniques. Extremely small, heavily calcified vessels are able to be reliably reconstructed using microsurgical techniques and high magnification. Additionally, revascularization followed by microsurgical free tissue transfer has proven to be a valuable alternative to amputation in patients with major soft-tissue loss, or bony or tendon lesions requiring soft-tissue reconstruction. Although metabolic risks are potentially high, we have experienced a very low morbidity and mortality with a thorough medical work-up and follow-through in conjunction with these major procedures. It is our expectation that judicious application of microsurgical techniques in treatment of the ischemic diabetic lower extremity will continue to improve the chances for long-term bipedal ambulation in this patient population.

The free iliac flap: a lateral modification of the free groin flap.

A lateral modification of the free groin flap, called the free iliac flap, is presented. By moving the outline of the free groin flap laterally, so that the medial margin lies lateral to the underlying femoral triangle, a flap is obtained which is uniformly slender and which has a long vascular pedicle. The anatomical findings, a method for safe dissection of the superficial circumflex iliac vessels, and the results of 18 clinical cases are presented.

Photomicrography through the operating microscope.

In summary, the production of high quality photomicrographs through the operating microscope requires considerable attention to detail. The author describes all the details which he has found essential for obtaining good photomicrographs for documentation and/or publication.

The histopathology of small arteries following experimental microvascular anastomosis.

We studied the histopathological changes present at various intervals after microsurgical anastomoses in the femoral arteries of 30 rats. The principal findings were (1) widespread loss of intima, (2) widespread necrosis of media, and (3) dehiscence of sutures. The possible causes for these, and their possible significance, are discussed.

The microarterial anatomy of the dorsalis pedis flap and its clinical applications.

This study was undertaken to clarify the microanatomic details of the cutaneous branches of the dorsalis pedis artery. The microarterial anatomy of the dorsalis pedis flap area and its clinical implications are described.

Direct in vivo observations of embolic events in the microcirculation distal to a small-vessel anastomosis.

This study was done to determine whether microemboli are produced by an arterial anastomosis. Direct in vivo observations were made in an isolated microcirculatory bed lying directly downstream from a newly made anastomosis. The tissue used was the isolated rat cremaster muscle, a new experimental model. The vessel anastomosed was the external iliac artery. Following anastomosis, microemboli were clearly observed in eight of eight animals during the first 30 minutes after clamp release. Embolic events were sometimes of impressive magnitude and in one case were associated with cessation of blood flow throughout the preparation. No microemboli were observed in eight of eight animals subjected only to dissection of the cremaster, nor were any observed in eight of eight animals in which the isolated cremaster was subjected only to 2 hours of clamp ischemia. These findings may be significant in explaining perturbations to blood flow following free-tissue transfer and instances of partial tissue necrosis following apparently successful arterial repair. These findings also identify an important factor (microemboli) to be considered in research on reperfusion injury.

Microcirculatory disturbances following the passage of emboli in an experimental free-flap model.

Following completion of arterial repair in an experimental free-flap model, platelet emboli have been observed passing through the microcirculation downstream. The purpose of this experimental study was to observe and quantitate changes in capillary perfusion occurring subsequent to these events. The isolated rat cremaster model was used. For 6 hours subsequent to surgical injury of the main artery in this model, the number of emboli and the number of perfused capillaries downstream were counted. In eight rats having an intentional arterial wall injury, emboli were consistently seen during the first hour of reflow. In the nine control animals having no arterial injury, no emboli were seen. The presence of emboli in the cremaster muscle, resulting from the arterial injury, was associated with a significant reduction in the number of perfused capillaries. We suggest that the observed decrease in capillary perfusion was associated with microemboli that produced an adverse effect for several hours after their initial presence in the circulation.