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.

Tertiary resurfacing after one of the first free flaps in Europe, a reflection on 30 years of microsurgical progress.

Free flaps have been used for over 30 years. During this period, improved anatomical understanding has increased donor options and available pedicle lengths, permitting safer, single-stage reconstructions with simpler anastomoses. Refinements, such as perforator flaps in particular, have greatly improved donor morbidity, recipient site cosmesis, and the ability to replace 'like with like' while retaining options for innervation. This case highlights the evolution from one of Europe's first free tissue transfers, effectively a perforator flap, through the advent of free muscle flaps to the current generation of contourable perforator flaps. Free flap transfer has become increasingly sophisticated, safer, and more predictable, yet the potential quality of reconstructive outcome has changed little.

Alendronate prevents bone loss in patients with acute spinal cord injury: a randomized, double-blind, placebo-controlled study.

CONTEXT: Patients who sustain an acute spinal cord injury (SCI) experience rapid dramatic reductions in bone mineral density (BMD), especially marked in sublesional areas and sometimes leading to hypercalcemia and hypercalciuria, as well as increased fracture risk. OBJECTIVE: In this prospective, double-blind, randomized, placebo-controlled study, we evaluated the hypothesis that oral alendronate administration would preserve BMD when administered soon after acute SCI. PATIENTS AND INTERVENTION: Thirty-one patients with acute SCI were randomly allocated to receive oral alendronate 70 mg/wk or placebo, within 10 d of acute SCI, for 12 months. MAIN OUTCOME MEASUREMENTS: At entry and at 3, 6, 12, and 18 months, total body bone density, lumbar and hip BMD, ultrasound of the calcaneus, 24-h urinary calcium, and serum C-telopeptide (betaCTX) were measured. RESULTS: At study entry, patients in the two groups were well matched for age, gender, severity of neurological deficit, BMD, urinary calcium, and betaCTX. BMD indices declined steadily in the placebo group, and this effect was attenuated significantly by alendronate. After 12 months, there was a 5.3% difference (P<0.001) in total body BMD and a 17.6% difference (P<0.001) in the total hip BMD between the two groups. Alendronate compared with placebo induced significant (P<0.001) reductions in urinary calcium excretion and serum betaCTX. No treatment-related side effects were noted. CONCLUSIONS: We conclude that alendronate therapy, 70 mg/wk, initiated soon after acute SCI, prevents bone loss and is not associated with side effects.

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.

Inferior angle of the scapula as a vascularized bone graft: an anatomic study.

In reconstructing patients with massive midface losses, the authors required a vascularized bone graft that could be used to reconstruct the palate and orbital floor, provide vertical maxillary support, and provide soft tissue. The inferior angle of the scapula appears to be a promising source of vascularized bone stock, and until now, there has been no clear description of its vascular anatomy. The purpose of this study was to define the vascular anatomy of the inferior angle of the scapula. Thirteen fresh cadavers were studied. The subscapular artery was injected with Microfil (Flow Tec, Carver, MA) at its origin. Two branches of the subscapular artery were found to converge on the angle of the scapula: the descending osseous branch of the circumflex scapular, and the transverse branch of the thoracodorsal. The descending osseous branch of the circumflex scapular artery supplied the inferior angle of the scapula in 100 percent of cases. The transverse branch of the thoracodorsal artery supplied it in 76 percent of cases. The descending osseous branch of the circumflex scapular artery is the principal artery supplying the inferior angle of the scapula.

Inframammary fold: a histologic reappraisal.

The inframammary fold is a defining element in the shape and structure of the female breast. It should be preserved whenever possible in ablative procedures and recreated accurately when the breast is reconstructed after mastectomy. To date, no accurate anatomic description of this essential structure exists. Previous studies have suggested that the fold is produced by a supporting ligament running from the dermis in the fold region to a variety of locations on the rib cage. This clinic's experience with mastectomy, augmentation mammaplasty, and breast reconstruction does not support the existence of a ligamentous structure. To define the structure of the inframammary fold, 10 female and 2 male cadavers were studied. The anterior chest wall was removed en bloc and frozen in orthostatic position. Parasagittal sections were made of the inframammary fold with the chest wall intact. After decalcification of the ribs and routine histologic preparation, thin sections were stained with Gomori's trichrome. On light microscopic examination, no demonstrable ligamentous structure of dense regular connective tissue could be identified in the fold region in any of the 12 specimens. Superficial and deep fascial layers were uniformly observed anterior to the pectoralis major and serratus anterior muscles. The superficial fascia was connected to the dermis in the fold region in a variety of configurations. In some cases, the deep fascia fused with the superficial fascia and dermis at the fold level. In other cases, bundles of collagen fibers arising from the superficial fascial layer were found to insert into the dermis at the inframammary fold, slightly inferior to it, or both. These bundles were observed consistently in sections from the sternum to the middle axillary line. They were distinct from Cooper's suspensory ligaments, which are seen more superiorly in the glandular tissue.

Endothelin-1 does not contribute to ischemia/reperfusion-induced vasoconstriction in skeletal muscle.

The experiment reported was designed to investigate whether endothelin-1 (ET-1) contributes to vasospasm and poor perfusion during the reperfusion after prolonged ischemia in skeletal muscle. Male Sprague-Dawley rats weighting 100 to 120 g were anesthetized with Nembutal. The vascular isolated rat cremaster muscle, coupled with local interarterial infusion, was the model used in this study. The diameters of feeding arterioles and terminal arterioles were measured utilizing intravital microscopy. The number of terminal arterioles with temporary cessation of flow were counted in each cremaster. Group 1: ET-dose response (8 rats)--various concentrations of ET-1 (from 10(-8) M to 10(-5) M) were infused into the cremaster to test whether this muscle was responsive to the agent in a dose-dependent manner. Group 2: ET-antagonist response (12 rats)--PD-142893, 10(-4) M (ETab receptor antagonist) plus ET-1 10(-7) M were infused into the cremaster to test whether vasospasm caused by exogenous ET-1 could be prevented by pretreatment with this specific ETab receptor antagonist. Group 3: ischemia/reperfusion response (12 rats)--PD-142893, 10(-4) M was infused into the cremaster before ischemia (4 hr warm ischemia) and during reperfusion to test whether ETab receptor antagonism was effective in preventing the vasospasm associated with ischemia/reperfusion injury. The results from this study show that a mixed ETab endothelin antagonist, PD-142893, infused before ischemia and during reperfusion at a dose which virtually abolished the vasoconstriction produced by a high concentration of exogenous endothelin-1, had no effect on ischemia/reperfusion-induced vasoconstriction in this model. These results suggest that ET-1 probably does not contribute to the ischemia/reperfusion-induced vasoconstriction and poor reflow in rat skeletal muscle.

Lack of nitric oxide contributes to vasospasm during ischemia/reperfusion injury.

Vasospasm can be a complication after free tissue transfer and replant operations. Recent studies suggest that vasospasm may be due to endothelium dysfunction, resulting in impairment of nitric oxide production. The present experiment was designed to investigate acute responses of the microcirculation of skeletal muscle to local interarterial infusion of sodium nitroprusside (a direct donor of nitric oxide and thus an endothelium-independent vasodilator) or acetylcholine chloride (which stimulates endothelium release of endogenous nitric oxide) during reperfusion after 4 hours of warm ischemia. Male Sprague-Dawley rats, each weighing 100 to 120 gm, were anesthetized with sodium pentobarbitone and were surgically prepared with vascular isolated and denervated cremaster muscles that were subjected to 4 hours warm ischemia and 2 hours of reperfusion. Sodium nitroprusside (10(-3) M), acetylcholine chloride (10(-4) M), or normal saline (eight rats for each group) were administered by local infusion (0.1 ml/hour) through the femoral artery into the natural blood flow of the cremaster. The arterial tree in the cremaster was observed and arteriole diameters (A1-A4) were measured using intravital microscopy. The number of arteriole branches having temporary stoppage of flow were counted in each cremaster. The results from this study show that local infusion of sodium nitroprusside, but not acetylcholine chloride, prevents ischemia/reperfusion vasoconstriction in A3 and A4 arterioles and thus improves microvascular blood flow. Generalized vasoconstriction caused by topically applied norepinephrine (10(-6) M) to sham ischemia cremasters could be completely reversed by the local infusion of 10(-4) M acetylcholine chloride. These results indicate that vasospasm after ischemia/reperfusion may be related to temporary endothelial cell dysfunction, resulting in the inability to produce sufficient nitric oxide during early reperfusion. Vascular smooth muscle, however, is responsive to locally administered sodium nitroprusside infusion (which is thought to provide exogenous nitric oxide).

Platelet-derived thromboxane A2 decreases microvascular perfusion after arterial repair.

Previous work suggests that cod liver oil helps to protect the microcirculation from the consequence of thromboembolic events. The possibility that altered synthesis of thromboxane A2 accounts for the protective effects seen with cod liver oil was investigated in the present study. This was done using the combined thromboxane A2 synthetase inhibitor and thromboxane A2-prostaglandin H2 receptor blocker R68070 (Ridogrel). A standardized microvascular injury was inflicted on the right iliac artery of the rat to generate emboli. The downstream cremaster muscle was used to visualize the passage of the ensuing emboli and to assess the effects of this arterial injury on capillary perfusion and arteriole diameters. The number of visible emboli was not changed by either cod liver oil diet or Ridogrel administration. However, capillary perfusion was preserved by using cod liver oil (n = 7) and was significantly increased by using Ridogrel (n = 7) in comparison with untreated controls (n = 7) in which capillary perfusion was decreased because of the emboli. The administration of Ridogrel to cod liver oil-treated animals (n = 7) provided no additive benefit. The percentage change in A-2 vessel diameters in cod liver oil-treated (n = 7) animals was no different from the control group (n = 7). Ridogrel (n = 7), on the other hand, produced a significant increase in A-3 vessel (n = 21) diameters, but its effects were comparatively less in the cod liver oil-treated animals (n = 7). The formation of platelet aggregates (emboli) appears relatively independent of thromboxane A2 in the rat. Ridogrel is very effective in protecting the microcirculation, and these effects appear to be mediated by A-3 vasodilatation, which, therefore, is at least partially thromboxane A2-dependent. The positive effects of cod liver oil may be mediated by a mechanism that reduces thromboxane A2 synthesis, but further studies are necessary.

Oral presentations for surgical meetings.

Each year the Association for Academic Surgery sponsors the "Fundamentals of Surgical Research" course which is established for residents who are beginning research training. A lecture outlining various aspects of effective scientific presentations, such as that delivered at a national or regional surgical meeting, is part of the course. Faculty from our institution have organized this lecture for several years. The lecture content has been revised each year to reflect the recommendations of the participating residents and faculty. Herein, we summarize the requirements for composing and delivering a scientific surgical presentation that is noted for its clarity, easily understood methods, interpretable data, and scientific and/or clinical implications.

In vitro platelet aggregation studies in microvascular surgery research: a method in the rat model.

There is now a growing awareness of the central role of platelet function in microvascular thrombosis. Platelet aggregation studies remain one of the most useful ways of studying platelet function and response to different stimuli. This brief communication highlights some of the main variables that can affect platelet aggregation in rats and emphasizes the existence of important differences in these variables compared with human platelet aggregation.

Can varying flow velocity across an arterial anastomosis prevent thromboembolic injury?

In this study, simulated "poor" repairs applied to transverse incisions in the iliac arteries of 40 rats were the basis for comparing the effect of variations in blood flow on thromboembolism. Using vital microscopy and digital image processing, we performed 2 experiments. In the first experiment (n = 20), the reduction of post-repair blood flow by approximately 50% resulted in an 83% reduction in the total number of emboli appearing in the microcirculation of the cremaster muscle distal to the repair. In the second experiment (n = 20), the same reduction in blood flow typically resulted in larger repair-site thrombi which required significantly more time to grow to their maximum size. We conclude that reducing pedicle artery blood flow to approximately half in our rat model during reperfusion can protect the downstream microcirculation from embolic injury without increasing the incidence of thrombotic occlusion.

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.

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.

Effect of human IgG antiphospholipid antibodies on an in vivo thrombosis model in mice.

High levels of IgG antiphospholipid antibodies (aPL) have been associated with clinical thrombosis. It is uncertain however whether these antibodies play a direct role in thrombosis or are merely epiphenomena. To investigate whether antiphospholipid antibodies might play a role in thrombosis, we utilized a novel mouse model in which the dynamics of in vivo thrombosis can be studied. CD1 mice (26-30 g) were passively immunized with 25 mg of human IgG from a patient with the Antiphospholipid Syndrome (IgG-APS) (n = 17), IgG from normal pooled sera (IgG-NHS) (n = 9), or saline solution (n = 12), followed by 40 mg of the same preparations at 48 h. At 72 h, levels of human aPL antibodies, detected using the anticardiolipin ELISA test (aCL ELISA test), in mice immunized with IgG-APS, were 50-100 GPL units. Each animal was anesthetized, femoral vein minimally mobilized and subjected to a standardized "pinch" injury to induce thrombosis. The vessel was transilluminated using acrylic optical fibers connected to a light source, and clot formation and dissolution were visualized by a standard surgical microscope equipped with a video camera, video recorder, and computer assisted analysis system. Results showed that average clot size was significantly larger in mice immunized with IgG-APS compared to those treated with saline (p < 0.037). In addition, the thrombus persisted longer in a significantly higher number of mice immunized with IgG-APS (10/17) compared to mice immunized with IgG-NHS (1/9) or saline (2/12) (p < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Microcirculatory consequences of microvascular surgery.

Although free tissue transfer success has been greatly improved by developments in operating microscopes, microsutures, microinstruments, and technique, free flap and replant failure remain a significant problem under certain adverse circumstances. The nature of these failures is often multifactorial and remains poorly understood. A greater understanding of the processes involved would provide the potential for greater pharmacological control of any adverse conditions prevailing and would thus offer the prospect of more effective adjunctive therapy in the presence of such adverse conditions. Research endeavors in this area have been hindered by the absence of good research models. The isolated rat cremaster muscle model is a recently developed model that simulates the conditions of free tissue transfer. Using this model, both thrombus formation and numerous microcirculatory parameters can be measured. The microcirculatory parameters studied to date include the formation of thromboembolism, capillary perfusion, vessel diameters, red blood cell velocity, leukocyte-endothelium interaction, and microvascular leakage. The isolated rat cremaster muscle model addresses many of the shortcomings of earlier research models and offers the promise of answering at least some of the many unanswered questions relating to free flap and replant failure.