Neuroma transposition and intramuscular implantation using the Mitek "soft-tissue anchor": a new technique

The authors describe a new technique for intramuscular implantation of a nerve ending after peripheral neuroma excision. Sixteen peripheral neuromas in 10 patients were excised and then implanted into muscle tissue using the Mitek anchor. The positions of the anchors were documented by immediate anteroposterior and lateral radiographs. These views were repeated at 2 months to assess any migration. All patients had resolution of the symptoms related to their neuromas. No substantial migration was noted in any of the patients. The Mitek anchor can be used as a "soft-tissue" anchor to position a nerve ending reliably at a precise depth and tension in muscle tissue with minimal trauma.

Nerve growth factor inhibition prevents traumatic neuroma formation in the rat

Nerve growth factor (NGF) is thought to play a role in the pathogenesis of neuroma formation as well as in the development of neuropathic pain. In this study we attempted to antagonize NGF by using trkA-IgG, an inhibitor of NGF, consisting of the NGF receptor linked to an immunoglobulin. It was delivered by an implanted osmotic pump directly to the site of a sciatic nerve transection in 16 rats for 30 days. The animals were monitored daily for the first 2 weeks for evidence of auto-cannibalization (autotomy) of the denervated foot (a sign of neuropathic pain). Four (25%) of the 16 rats receiving trkA-IgG exhibited such cannibalization compared with 9 of 15 control rats (60%) that underwent an identical procedure but were not treated with the trkA-IgG solution. One month after surgery the sciatic nerves and representative dorsal root ganglia (DRG) from these rats were evaluated histologically. Six of the 16 experimental rats (38%) demonstrated histological evidence of neuroma formation compared with 12 of the 15 controls (80%). There were no histological differences between the DRG from the two groups. These results support the notion that inhibiting NGF following peripheral nerve injury in the rat can reduce neuroma formation and neuropathic pain without damaging the cell bodies of the transected neurons.

Reconstruction of ureteral defects with microvascular vein grafts in a rat model

This study was undertaken to test the performance of an autologous vein graft as a ureteral replacement in the rat model. Twenty-six rats were divided into three groups. In Group 1 (n = 10), the animals had a 3-mm segment of the ipsilateral ureter excised and the ureteral defect repaired, using a superficial epigastric vein graft. In Group 2 (n = 10), the same ureteral defect was created and again repaired, using a superficial epigastric vein graft, with the addition of a Silastic stent. The control, Group 3 (n = 6), had the ureter transected and repaired solely by means of primary anastomosis. Animals from each group underwent urography and were sacrificed for histology at three different postoperative intervals: 1, 4, and 12 weeks. Postoperative urography results showed normal renal function in the animals with ureteral reconstruction using vein grafting aided by a stent, as well as in those with primary ureteral anastomosis. No renal function return was seen in the animals with ureteral reconstruction by vein grafting alone, without stent support. Histologically, a progressive loss of the vascular endothelium, and replacement with the urothelium typical of the ureter, was seen in the stented vein grafts. Severe ureteral obstruction at the proximal site of the graft and hydronephrosis were seen in the vein-graft group without stenting. This study demonstrates that autologous vein grafts can be used successfully to correct a ureteral deficit, contingent on accurate microsurgical technique and immediate stenting.

Improvement of skin paddle survival by application of vascular endothelial growth factor in a rat TRAM flap model

The effect of vascular endothelial growth factor (VEGF) on skin flap survival and its ability to induce a pharmacological delay by promoting angiogenesis in a flap was studied in a rat transverse rectus abdominis musculocutaneous flap, using a 3 x 8-cm skin paddle with the inferior epigastric vessels as its main vascular supply. Forty-three Sprague-Dawley rats were divided into four groups. In group 1, VEGF was injected into the femoral vein after the flap was elevated. In group 2, VEGF was injected intra-arterially into the flap through the superior epigastric artery after the flap was elevated. In group 3, VEGF was injected into the subcutaneous fascial layer in the area where the flap would be dissected, and the flap was then raised 7 days after injection. In group 4, the flap was dissected and replaced, using saline injection as the control. On postoperative day 5, the survival area of each skin paddle was measured and the flap was harvested for histological analysis. The results showed that the mean survival area +/- standard deviation for the skin paddle was 6.82 +/- 4.89 cm2 (28.4 +/- 20.4% of the whole skin paddle) in the control group, and 4.2 +/- 3.0 cm2 (17.5 +/- 12.5%) and 6.02 +/- 5.97 cm2 (25.1 +/- 24.9%) in the groups with VEGF systemic and intra-arterial administration respectively. The skin survival area in the group with preoperative subcutaneous administration of VEGF was 17.85 +/- 2.88 cm2 (74.4 +/- 12%), which was significantly higher than the other three groups (p < 0.01). Histological semiquantitative analysis showed increased neovascularization in the flap treated with VEGF preoperatively. The data demonstrate that preoperative treatment with VEGF can induce angiogenesis and enhance skin paddle survival in a musculocutaneous flap.

Role of medical students in microsurgery research

Microsurgery is an integral element in many surgical specialties, as well as an important technique for surgical research. Student participation in microsurgery research programs can be a source for both high quality training in skills and for research contributions. In this article, the authors review their experience in developing general principles for setting up medical student microsurgery research programs, and analyze the research output and career choices made by the students who have participated.

A phase II trial of intraluminal irrigation with recombinant human tissue factor pathway inhibitor to prevent thrombosis in free flap surgery

A multicenter, multinational, blinded, randomized, parallel-group, phase II study was conducted to investigate the use of recombinant human tissue factor pathway inhibitor (rhTFPI; SC-59735) as an antithrombotic additive to the intraluminal irrigating solution during microvascular anastomosis in free flap reconstructive surgery. A total of 622 patients undergoing free flap reconstruction were randomly assigned to three groups. For each group, a different intraluminal irrigating solution was administered at completion of the microvascular arterial and venous anastomoses and before blood flow to the flap was reestablished: rhTFPI at a concentration of 0.05 or 0.15 mg/ml (low-dose or high-dose group, respectively) or heparin at a concentration of 100 U/ml (current-standard-of-practice group). There were no other differences in treatment among the groups. Patient characteristics, risk factors, and surgical techniques used were similar among all three groups. Flap failure was lower (2 percent) in the low-dose rhTFPI group than in the high-dose rhTFPI (6 percent) and heparin (5 percent) groups, but this difference was not statistically significant (p = 0.069). There were no significant differences in the rate of intraoperative revisions of vessel anastomoses (11 percent, 12 percent, and 13 percent) or postoperative thrombosis (8 percent, 8 percent, and 7 percent) among the low-dose rhTFPI, high-dose rhTFPI, and heparin groups, respectively. The rate of postoperative wound hematoma was significantly lower in the low-dose rhTFPI group (3 percent) than in the high-dose rhTFPI (8 percent) and heparin (9 percent) groups (p = 0.040). There were no differences in blood chemistry or coagulation values among the three study groups. Other than hematomas, there were no differences in the incidence or severity of adverse reactions among the three groups. It is concluded that use of rhTFPI as an intraluminal irrigant during free flap reconstruction is safe, well tolerated, and as efficacious as use of heparin for preventing thrombotic complications during and after the operation. Furthermore, the lower dose of rhTFPI (0.05 mg/ml) may reduce the occurrence of postoperative hematoma and help prevent flap failure.

Microvascular transplantation of the rat submandibular gland

Xerostomia results from salivary gland irradiation during treatment of head and neck malignancies. In addition to having difficulty with speech and swallowing, these patients experience loss of taste, dental caries, and chronic fungal infections. The paired submandibular glands provide 70 percent of the normal salivary flow and are difficult to shield during radiation therapy. Another sicca condition, xerophthalmia, may result from facial nerve injury or other medical disorders and results in pain, corneal ulceration, and possible vision loss. Treatment options for xerostomia are limited, and management of xerophthalmia usually focuses on the eyelids, rather than the fundamental problem of inadequate secretory protection. In this study, a rat model for submandibular gland microvascular transplantation was developed to assess the feasibility of salivary tissue transfer. Sixteen rats underwent submandibular gland transplantation from the neck to the groin. Fourteen of these rats underwent microvascular anastomosis of the vascular pedicle. Ten glands were assessed for viability at 4 days after transplantation, and four glands were examined after 7, 10, 14, or 21 days. By gross and histologic examination, 93 percent of transplanted glands showed expected long-term viability after at least 4 postoperative days. Microvascular techniques were shown to be applicable to the transplantation of submandibular gland salivary tissue. This has not previously been shown in a rat model. It is possible that submandibular glands could be transplanted to the eye for treatment of xerophthalmia and out of the neck during irradiation of the head and neck, with subsequent replantation after treatment as a means of preventing permanent xerostomia.

Free microvascular transfer of the acromiotrapezius osteomuscular flap in rats

The acromiotrapezius-scapular spine osteomuscular flap is a new osteomuscular research model for use in microvascular free tissue transfer in rats. We performed anatomical studies to collect data on muscle weight, dimension, vessel calibre and bone size in 20 flaps. This flap has a triangular shape with an average size of 38 x 39 x 32 mm and an average weight of 1.25 g; the scapular spine of 20 mm in average length can be harvested with the flap. The pedicle can be taken in continuity with the cervical trunk (average diameter of artery and vein were 0.5 mm and 0.6mm, respectively, with an average pedicle length of 12 mm). The flap was harvested and transferred to the groin area of the same rat and anastomosed to the superficial epigastric vessels. Fifteen transplantations were performed and the 7-day flap survival was 93.3%. The acromiotrapezius flap is believed to be a new and reliable osteomuscular model in the rat.

Rat tail replantation as a training model for microvascular procedures of digit replantation

In this study we sought to evaluate the potential of rat tail replantation as a tool for very-small-vessel microvascular anastomoses. We used 10 adult Sprague-Dawley rats. The tail was completely amputated 2.0-cm distal to the base of the tail. Then the tail was replanted with anastomoses of two superficial dorsal veins from both sides and one artery. All 10 replanted tails were pink, viable, and normal-appearing at all daily inspections performed from the first to the fourteenth postoperative days. This model can provide a training tool for the acquisition of superior microvascular surgical technique for the repair of very small vessels that stimulate digital replantation.

New simplified radio-opaque injection technique for visualization of rat arteries

We have developed a new and simplified injection technique based on a mixture of latex and lead oxide. This injection technique is unique in its possession of both color and radio-opacity. We have developed and refined this methodology in rats, and have demonstrated it to possess superior qualities of injectability. Depiction of small vessels is highly detailed both radiographically and grossly.

Fibromuscular proliferation in finger arteries after hand replantation: a case report

We report on a case where a digit of a previously replanted hand was amputated 3 years after injury. Histologically, the finger arteries demonstrated a marked intimal thickening due to fibromuscular proliferation, with narrowing of the lumen. The media showed muscular hyperplasia and fibrosis, whereas the adventitia was normal. These changes are probably a consequence of ischemia and reperfusion injury and might explain the persistent vasomotor insufficiency found in replantation patients.

Results of termino-lateral neurorrhaphy to original and adjacent nerves

In this comprehensive investigation, we studied three different neurorrhaphy models in an attempt to elucidate the potential of termino-lateral nerve repair to original and adjacent nerves. In experimental group 1, the peroneal nerve was sectioned and then attached to the posterior tibial nerve in a termino-lateral fashion. In experiment group 2, the motor nerves to the gastrocnemius muscle were sectioned and then attached to the posterior tibial nerve in a termino-lateral fashion. In experimental group 3, the obturator nerve (L2-4) was sectioned and attached to the sciatic nerve (L4-6) in a termino-lateral fashion. For the control in each group, the same type of nerve used in each respective group was transected without repair. Experimental groups 1 and 2 showed viable axons in the peroneal nerve distal to the neurorrhaphy site. Experimental group 3 showed no viable axons at these sites. No regeneration was observed in the transected nerve without repair in all three control groups. This study suggests that termino-lateral neurorrhaphy is a viable means of repairing damaged nerves if the distal segment of the sectioned nerve is reattached to its original trunk distal to its original branch point. However, the results from experimental group 3 demonstrate that termino-lateral neurorrhaphy cannot be used to repair nerves when the donor and recipient nerves originate from different spinal cord levels.

Application of hemodilution in microsurgical free flap transplantation

The intra-operative hemodilution and blood auto-transfusion is a blood-saving technique that can be performed when major blood loss is expected. The effects of this technique were studied in 30 microsurgical free flap transplantation patients. Between 400-600 ml blood was collected from the patients before surgery. The patients received dextran, a balanced salt solution, and glucose with the ratio of 3:1 to the collected blood volume, bleeding, and urine before the blood auto-transfusion. There were no significant changes in RBC, HCT, MCV, blood pressure, or heart rate. Of the 30 free flaps, 28 were successful with a 93.3% survival rate. The safety of intra-operative hemodilution and autologous blood transfusion in microsurgery as well as the effect of hemodilution on transplanted flap survival are discussed in this study.

Effect of anastomosis and geometry of vessel curvature on blood flow velocity and patency in microvessels

The effect of the geometry of the vessel and the number of anastomoses on the blood flow was studied. Four different shapes of the vessel were constructed by using a 6-cm-long double vein graft model with three anastomoses: (1) an alpha loop, (2) an omega loop, (3) a sigmoid curve, and (4) straight. Blood flow was measured by an ultrasound Doppler flowmeter. The result showed no alternation in blood flow across different geometry and through three patent microanastomoses. However, six out of seven vein grafts were thrombosed at 24 hr postoperative due to vascular kinks. This model demonstrates potential sites of kinking at the dissection end of the femoral artery, the microanastomoses, the side branches of the vein graft, and the adventitial adhesions. This model is recommended to microvascular trainees for the study of kinking and the management of redundant pedicles and vein grafting.

Effect of vein grafting on the survival of microvascularly transplanted muscle flaps

Since vein grafting is often required during transplantation of free muscle flaps but is associated with a higher failure rate than those flaps transplanted with primary anastomoses, we sought to compare primary repair with the use of vein grafting in an experimental setting. We transplanted the gracilis muscle to the contralateral side in 98 rats using four different methods of vessel repair. In the Control group (n = 28), both femoral vessels were anastomosed primarily. In Experimental Group 1 (n = 25), the femoral artery was anastomosed with an epigastric vein graft and the femoral vein was anastomosed primarily. In Experimental Group 2 (n = 25), the femoral vein was anastomosed with a femoral vein graft and the femoral artery was anastomosed primarily. In Experimental Group 3 (n = 20), both femoral vessels were anastomosed with vein grafts. The Control and Experimental Groups 1-3 survival rates were 89.3, 76.0, 84.0, and 70.0%, respectively; none of the experimental group survival rates was significantly different from that of the control (P < 0.5). This study demonstrates that the use of size-matched, interpositional vein grafts in the arterial or venous pedicle of the rat gracilis muscle flap during transplantation did not significantly decrease flap survival as compared to primary arterial or venous anastomoses. If the observed failure rate persisted with expansion of the study groups to 60-100 animals each, the failure rate of flaps with vein grafts would be significantly lower and comparable to failure rates reported in some clinical series. The large numbers necessary to significantly show this decrease make this model impractical for further studies.

Microvascular hand surgery-transplants and replants-over the past 25 years

Two hundred eighty articles related to microvascular transplants and replants published in The Journal of Hand Surgery over the past 25 years were reviewed. Every facet of microsurgery was covered. One hundred seventy-one articles are referenced and discussed under the following major categories: microvascular transplants, replants, nerve grafts, vein grafts, cold intolerance, vasospasm, monitoring, immediate reconstruction, and historical. Contributions were received from 37 countries and 175 authors or groups of authors.

The effects of VEGF on survival of a random flap in the rat: examination of various routes of administration

The purpose of the present study was to determine the effects of vascular endothelial growth factor (VEGF) on survival of a full thickness random pattern, McFarlane musculocutaneous flap in the rat. In addition, this study examined a number of different methods of VEGF delivery in an attempt to determine the most effective route of administration. A 2 x 8 cm full thickness dorsal flap with the pedicle remaining attached at the anterior end was elevated in 72 male Sprague-Dawley rats. The rats were randomised into six groups and immediately received the following treatment: Group I (n = 12): systemic VEGF injection into the femoral vein (50 microg/ml); Group II (n = 10): multiple systemic VEGF injections at 0, 24 and 48 h post flap elevation (50 microg/ml); Group III (n = 12): subdermal VEGF injection into the flap (1 microg/ml); Group IV (n = 12): subfascial VEGF injections into the recipient bed (1 microg/ml); Group V (n = 10): topical VEGF onto the recipient bed (1 microg/ml); Group VI (n = 16): control group with no treatment. Following 5 days recovery, the area of flap survival was measured. Mean flap survival ranged from 91% in Group II to 78% in Group V, and was significantly greater in all experimental groups (P< 0.001 for Groups I-IV and P< 0.05 for Group V) as compared to the control group (mean survival of 66%). The only significant difference between the experimental groups was between the mean survival in Group II and Group V (P< 0. 05). Histological analysis demonstrated a qualitatively greater amount of granulation tissue and neovascularisation in the experimental groups. These results support the notion that VEGF rescues tissue at risk of hypoxic damage by inducing angiogenesis, and the use of growth factors such as VEGF holds promise as a method of increasing skin viability.

[Relation of venous drainage and inadequate circulation in the rat pedicled TRAM flap model]

OBJECTIVE

To evaluate the circulatory characteristics of the TRAM flap because the vascular supply to lateral portion of the conventional TRAM (zone 4) occasionally may become compromised resulting in necrosis of fat tissue or requiring segmental excision of the poor perfused tissue.

METHODS

In this study, we designed a rat pedicled TRAM flap model with either inadequate arterial or venous circulation. The skin paddle was photographed and the survival areas were measured on the tenth postoperative day.

RESULTS

The results showed that the group with poor arterial inflow of the flap, which resulted from ligation of the superior deep epigastric artery, exhibited skin necrosis in zone 1 and 2. Venous stasis due to selective ligation of the venous pedicle resulted in necroses of a major area in the lateral part of the flap, especially in zone 4. However, venous stasis may be alleviated by an additional cutaneous venous return system.

CONCLUSIONS

Our results demonstrated that conventional rat TRAM flap with poor arterial inflow differs from that with venous stasis in terms of manifestations and extent of inadequate circulation. Necrosis of the lateral portion of human TRAM flaps may therefore be attributed to problems of venous stasis. Such problems might then be ameliorated by creating an additional cutaneous venous return system.

Free vascularized fibular bone flap in the rat

Free vascularized fibula bone flap has been widely used in reconstruction of the mandible, long segment defect, congenital pseudarthroses, and osteomyelitis. Such applications stirred an interest in basic studies of bone biology, bone healing process, and incorporation of recipient bone defect. An experimental free vascularized fibula rat model is presented here for such investigations. We performed 16 angiograms and anatomic dissections in eight rats for collecting data on fibular length, blood supply, and the caliber of significant vessels. The fibula was harvested with part of the flexor hallucis longus muscle with an average length of 28 mm. The pedicle can be taken in continuity with the popliteal vessels (average diameter of 0.8 mm and 0.9 mm of artery and vein, respectively, with an average pedicle length of 14 mm). This vascularized fibula bone was harvested and transferred to the groin area of the same rat and anastomosed to the saphenous vessels. Twelve transplantations were performed, with a 7-day flap survival rate of 100%. The free fibula vascularized bone flap in the rat is a reliable model for further investigations.

Biliary tract reconstruction using an autologous vein graft in rats

Numerous biologic and synthetic materials have been used with limited success as an interposed graft to repair segmental common bile duct (CBD) defects. The authors report here that an autologous vein graft can be successfully used to correct a CBD deficit contingent on accurate microsurgical technique immediate stenting and rapid graft vascularization. Thirty Sprague-Dawley rats underwent laparotomy and the experimental group (n=25) had a 3-mm segment of the CBD excised. The CBD defect was repaired using an interposed femoral vein graft aided by a plastic stent. The control group (n=5) had the CBD cut and repaired by means of primary anastomosis. The experimental group was subdivided into three sub-groups each examined at three different postoperative intervals: 1, 4 and 12 weeks. The results showed that inflammation was apparent in the venous wall following the first postoperative week. A progressive loss of the vascular endothelium and replacement with the columnar epithelium typical of the CBD was seen in the vein graft. Nineteen of the 25 experimental rats (76 percent) of the animals survived without complication from the surgery and there were no abnormalities in the liver biochemical tests of these animals. Any biliary tract obstruction that developed was attributed to dislocation of the stent leading to collapse of the vein graft (experimental group), or constriction of the anastomosis (control group). This study demonstrates that biliary tract reconstruction using an autologous vein graft can be successfully performed in a rat model of CBD repair. The application of this method to the clinical setting is also discussed.

Effect of hyperbaric oxygen on microvascular anastomosis healing and patency in the rat

Recent evidence has shown that changes in blood viscosity and marked increases in both platelet count and fibrinogen concentration occur after exposure to hyperbaric oxygen (HBO). The purpose of the present study was to address whether repeated HBO therapy would increase either hematocrit or platelet count, and to determine if these changes would influence the patency of the microvascular anastomosis, as well as anastomotic healing. Eighty femoral arteries from 40 rats were divided into four groups (n = 10), and arterial anastomoses were performed on normal arteries in the first two groups, and on crushed arteries in the second two groups. One of the normal artery groups and one of the crushed artery groups received repeated HBO treatments for 5 days. Anastomotic patency rates, platelet count, hematocrit, and breaking strength were recorded. Among the results of this study were that: (1) there was no difference in patency rate following HBO treatment in both the normal and crushed artery groups; (2) platelet count was significantly higher following HBO treatment in the groups with the undamaged arteries; (3) breaking strength was significantly increased following HBO treatment in the groups with the crushed arteries. The authors concluded that HBO therapy may be useful in improving the healing of microvascular anastomoses in vessels that have undergone crush injury. Although HBO treatment results in an increased platelet count, this does not influence anastomotic patency.

Saphenous neurocutaneous island flap model in the rat: evaluation of vascular supply

Neurocutaneous flaps are utilized routinely in reconstructive surgery and even more so during the past decade. In this study, the vascular supply of the neurocutaneous flap in the rat model is presented and evaluated. Thirty-six flaps (3.5x3 cm2) were dissected on the medial aspect of the leg based on a pedicle of the saphenous nerve, saphenous artery, great saphenous vein, and the surrounding fascial tissues. Animals in the experiment were divided into five groups with different circulatory patterns of pedicle dissections. In group I (N = 12), the pedicle artery, vein, nerve, and fascia were preserved. In group II (neurocutaneous flap model, N = 24), the saphenous artery was transected and the vein, nerve, and fascia were preserved. In group III (intraneural vascular plexus circulation pattern, N = 12), the saphenous artery and the fascia were transected. In group IV (extraneural vascular plexus circulation pattern, N = 12), the saphenous artery and nerve were transected. In group V (N = 12), the entire pedicle was transected completely. Flap survival was evaluated grossly on postoperative day 7. All flaps survived in group I, but in group II 19 of 24 flaps survived completely, 3 of 24 had partial necrosis, and 2 of 24 were completely necrotic. Complete necrosis was observed in all group III flaps. In group IV, 6 of 12 flaps survived completely, 3 of 12 flaps survived partially, and 3 of 12 flaps were necrotic (p<0.05 vs. group I). Only one flap with partial necrosis survived in group V. In group II, the average survival area was not significantly different from group I (p>0.05). In conclusion, the saphenous neurocutaneous flap in the rat is a reliable microsurgical model. The saphenous neurocutaneous flap is commonly supplied by both the intraneural and extraneural vascular plexus, and although the latter is more important, neither provides sufficient vascular supply on its own.

Prolonged perivascular use of verapamil or lidocaine decreases skin flap necrosis

During this experiment the authors investigated whether prolonged local use of verapamil or lidocaine prevents vasoconstriction and establishes better blood supply to the rat epigastric skin flap, hence reducing the necrosis that occurs otherwise. Abdominal wall skin flaps of 45 Sprague-Dawley rats, based on a single pedicle of the femoral vessels, were elevated. A subcutaneous pocket for the microport valve was created, and the adjacent catheter tip was sewn next to the femoral vessels. In the control and the two treatment groups, 0.5 ml saline or vasodilator solution respectively was injected through the microport every 12 hours for 5 days. On postoperative day 5 there was no statistical difference between the flap surfaces in all groups. The area of flap necrosis was significantly lower in the verapamil- (p = 0.001) and the lidocaine-treated (p = 0.012) groups vs. the control group as determined by analysis of variance with Bonferroni's post hoc test. In conclusion, topical application of verapamil and lidocaine solutions for 5 postoperative days decreased flap marginal necrosis significantly. Prolonged injection of vasodilators in the vicinity of the vascular pedicle prevents vasospasm and improves blood supply to the flap.

Effects of VEGF administration following ischemia on survival of the gracilis muscle flap in the rat

The incidence of free flap transplantation failure is only 3% to 5%, yet still occurs in cases in which the flap suffers prolonged ischemia. The purpose of the current study was to determine the effects of vascular endothelial growth factor (VEGF)--a potent angiogenic agent with a suspected role in the protection of endothelium--on flap survival in a model of ischemia-reperfusion injury. The model chosen was the rat gracilis muscle flap. A total of 36 adult male Sprague-Dawley rats were divided into three groups (N = 12). One experimental group received VEGF treatment and the other received heparin. A third group was treated with saline and served as the control. The gracilis muscle flap was dissected and isolated based on a vascular pedicle originating at the femoral vessels. Following 3.75 hours of ischemia, induced by clamping the femoral vessels, either VEGF, heparin, or saline was infused directly into the pedicle of the flap via a cannula. The flaps were evaluated both grossly and histologically after 72 hours of reperfusion. Eleven of the 12 flaps from the VEGF group survived, whereas the survival rate was 6 of 12 and 5 of 12 flaps for the heparin- and saline-treated groups respectively. Flap survival was significantly greater in the VEGF-treated group compared with the heparin- and saline-treated groups (p < 0.025, p < 0.01 respectively). Furthermore, there was no significant difference between the heparin and saline groups. These results indicate that VEGF plays a role in reducing the damage that occurs in ischemia-reperfusion injury, and that the use of VEGF holds promise as a potential therapy for increasing flap survival.

Quadriceps femoris muscle flap: largest muscle flap model in the rat

The purpose of this paper is to present a new muscle flap in the rat: the quadriceps femoris muscle flap based on a pedicle consisting of the femoral vessels. In order to establish the anatomic details of this model, seven rats were explored bilaterally, and the regional anatomy of the thigh was examined. The technical aspect of the model was established by the unilateral harvesting of 18 quadriceps femoris muscles. Findings were that this muscle is primarily supplied by a muscular branch originating at the superficial circumflex iliac artery. The average muscle weight was 6 g and the average pedicle length with femoral vessels was 6 mm. Eight of the harvested flaps were transplanted to the contralateral thigh, and the pedicle was anastomosed to the femoral vessels. The other ten flaps were resutured back to their beds. At 72 hr postoperatively, all flaps were viable with the exception of one of the transplanted flaps which was found to be necrotic. The quadriceps femoris muscle flap is technically both a reliable and simple model. With an average weight of 6 g, this flap is by far the largest described in the rat, and offers a convenient model for testing flap-related techniques and outcomes.

Patterns of flap loss related to arterial and venous insufficiency in the rat pedicled TRAM flap

Vascular supply to the contralateral portion of the conventional transverse rectus abdominis musculocutaneous (TRAM) flap (zone IV) may become compromised, resulting in partial flap loss and requiring segmental excision. The etiology of this necrosis is not clear. This study determines skin necrosis patterns on a superiorly pedicled caudal TRAM flap during conditions of venous and arterial insufficiency, and determines whether cutaneous venous outflow can sustain a flap with venous insufficiency. Twenty-eight adult male Sprague-Dawley rats underwent superior pedicled TRAM flap elevation, and the zones were marked on the skin paddle. The animals were divided into four groups: control (group A, N = 6), arterial ligation (group B, N = 6), venous ligation (group C, N = 8), and venous ligation with cutaneous venous outflow (group D, N = 8). After 10 days, the skin paddle was photographed and the areas of necrotic skin were measured. Results showed that group B (selective arterial ligation) had 51.7 +/- 2.8% and 40.0 +/- 2.0% skin necrosis in zones I and II respectively. Zone I necrosis was significantly greater in group B compared with the control (p < 0.05). Group C (selective venous ligation) resulted in 73.8 +/- 16.4% and 93.8 +/- 33.4% skin necrosis in zones III and IV respectively. This necrosis was significantly greater compared with the control (p < 0.001). Group D rats' lateral skin necrosis compared significantly less with group C (p < 0.001). These results demonstrate that the patterns of flap necrosis in rat TRAM flaps with poor arterial inflow differ from those with venous stasis. Necrosis of the contralateral portion (zone IV) of human TRAM flaps may be related to problems with venous stasis; thus, a cutaneous venous outflow may prevent this problem.

Development of a mouse limb transplantation model

A tremendous amount of research has been dedicated to laying the groundwork that will eventually lead to successful limb transplantation in humans. Limb transplantation in animal models has also been widely used for evaluating composite tissue allografts and various immunosuppressive regimens. Currently, there is no mouse model of limb transplantation. Such a model is attractive because it would allow investigators to apply the well-defined genetic characteristics of the mouse to the challenging field of limb transplantation. In this study, 12 mice underwent orthotopic hind limb transplantations using end-to-end anastomoses of the femoral vessels. The success rate of this surgical procedure was 83%, with 10 of the 12 limbs surviving. Experimental devices, operative procedures, and the major elements of success are discussed.

De novo autoimmunity to cardiac myosin after heart transplantation and its contribution to the rejection process

Allograft rejection is initiated by an immune response to donor MHC proteins. We recently reported that this response can result in breakdown of immune tolerance to a recipient self Ag. However, the contribution of this autoimmune response to graft rejection has yet to be determined. Here, we found that after mouse allogeneic heart transplantation, de novo CD4+ T cell and B cell autoimmune response to cardiac myosin (CM), a major contractile protein of cardiac muscle, is elicited in recipients. Importantly, CM is the autoantigen that causes autoimmune myocarditis, a heart autoimmune disease whose histopathological features resemble those observed in rejected cardiac transplants. Furthermore, T cell responses directed to CM peptide myhcalpha 334-352, a known myocarditogenic determinant, were detected in heart-transplanted mice. No responses to CM were observed in mice that had received an allogeneic skin graft or a syngeneic heart transplant, demonstrating that this response is tissue specific and that allogeneic response is necessary to break tolerance to CM. Next, we showed that sensitization of recipient mice with CM markedly accelerates the rejection of allogeneic heart. Therefore, posttransplant autoimmune response to CM is relevant to the rejection process. We conclude that transplantation-induced autoimmune response to CM represents a new mechanism that may play a significant role in cardiac transplant rejection.

Shortening of rat teeth prevents autocannibalization of surgical flaps

Self-biting in laboratory rats is an irritating problem that can impede progress and affect the credibility of experimental interventions. Autocannibalization frequently complicates the epigastric skin flap model that is often used to evaluate flaps. In one of the authors' studies, the autocannibalization rate of 55.6 percent in nine rats with unprotected skin flaps of the entire abdominal wall necessitated the application of previously reported plastic collars and protective vests to hinder self-biting. Because the use of these devices resulted in distress symptoms in nine of 11 rats with collars and flap congestion in five of five rats with vests, rat incisor teeth shortening was introduced as a stress-free method to prevent chewing. Careful teeth cutting obviated autocannibalization in 19 of 20 rats (p<0.01) during a 5-day follow-up. Rat incisor teeth shortening performed every 3 or 4 days is a simple, inexpensive, and reliable method to prevent autocannibalization in the rat, while maintaining the well-being of the animal.

Ischemic preconditioning of skeletal muscle improves tissue oxygenation during reperfusion

Ischemic preconditioning (IPC) renders tissue resistant to the deleterious effects of prolonged ischemia and reperfusion by prior exposure to brief, repeated periods of vascular occlusion. Although the mechanism by which IPC exerts its effect is unclear, it likely mediates an attenuation in capillary no-reflow. Tissue oximetry provides a potential technique to assess microvascular flow during ischemia/reperfusion and to measure the effect of IPC on muscle tissue oxygenation. The authors aimed to (a) establish that tissue oximetry is a sensitive method to assess the "no-reflow" phenomenon in skeletal muscle; and (b) to test the hypothesis that IPC would increase tissue oxygenation during reperfusion. In Group 1 (n = 5), the rabbit rectus femoris muscle was subjected to 2-hr ischemia. In Group 2 (n = 5), the muscle was subjected to 3.5-hr ischemia. In Group 3 (n = 6) the muscle was subjected to 3.5-hr ischemia preceded by three cycles of 10 min of pedicle occlusion and 10 min of reperfusion. Muscle oxygen tension was continuously monitored during the ischemic interval and for 6 hr of reperfusion. It was found that muscle oxygen tension in the flap at 5, 10, 30, 60, and 360 min after reperfusion was significantly decreased after 3.5-hr ischemia, compared with 2-hr ischemia (p < 0.05). Muscle oxygen tension at 30 and 60 min after reperfusion was significantly improved in the preconditioned group (p < 0.05). The results suggest that tissue oximetry is a sensitive method to assess tissue perfusion in reperfused skeletal muscle. Ischemic preconditioning improves tissue oxygenation during reperfusion following prolonged ischemia, which likely reflects an attenuation in capillary no-reflow.

Serratus anterior-rib composite flap: anatomic studies and clinical application to hand reconstruction

Because of its relative ease of dissection, increased length of the vascular pedicle, and excellent diameter for anastomosis, the serratus anterior-rib composite flap has been used to reconstruct bony and soft-tissue defects in the face and lower extremities. However, no data are available on optimal rib level or harvest location. The authors report the results of the vascular anatomy of this flap in 6 fresh cadavers and 2 clinical patients using this flap to reconstruct a defect in the hand. Arteriograms were performed through the thoracodorsal artery, and microscopic dissections were done at the rib periosteum. The sixth through the ninth ribs showed consistent filling of their respective intercostal vessels. The rib segments near the anterior axillary line had the most abundant communicating vessels between the serratus and the periosteum. In two patients, the serratus-rib composite free flap provided excellent bone and muscle length for reconstructing the first metacarpal defect.

Effect of cryopreservation on survival of composite tissue grafts

The problems in cryopreserving complex tissues remain poorly understood. In the present study, the viability of cryopreserved complex tissue, including skin and muscle flaps, and tail, was compared to simple artery and vein grafts in a rat model. Forty-four grafts, including the femoral artery (n = 15), femoral vein (n = 9), gracilis muscle flap (n = 8), groin cutaneous flap (n = 9), and tail (n = 3) were cryopreserved at -196 degrees C for 1 to 2 weeks, and then microvascularly transferred to analogous sites in inbred recipient animals. Three to 60 days post-transplant, all cryopreserved femoral arteries and veins were patent. Host groin cutaneous flaps with cryopreserved vessels grafted into the arterial pedicle survived with no complications However, severe endothelial-cell damage with extensive sloughing in the grafts was demonstrated at 30 min and 1 week following reperfusion, using factor VIII immunologic stain. Reendothelialization was evident at 2 months postoperatively. All cryopreserved composite tissue underwent early pedicle thrombosis The muscle and cutaneous tissue also showed gross and microscopic edema, with extensive red-cell extravasation within 30 min of reperfusion Cryopreservation thus can maintain the functional integrity of simple vessel grafts, but these grafts survive only as a conduit, given the severe endothelial-cell damage The failure of transferred complex cryopreserved tissue may reflect a combination of cellular or architectural damage to the capillary bed from ice formation during the freezing process and from reperfusion injury.

Effect of hyperbaric oxygen on survival of the composite ear graft in rats

In this study the authors set out to determine whether postoperative hyperbaric oxygen (HBO) therapy increases the survival rate of the composite graft in the rat ear model. A composite graft (1 x 0.5 cm2) that included skin, subcutaneous tissue, and cartilage was created from the left ear, and was transferred onto the posterior auricular site of the right ear. The animals were divided into two groups: a control group (N = 10) and an experimental group receiving HBO (N = 10). The experimental group was given HBO immediately following reattachment for 4 hours, and then for 6 hours each day for 5 days (2 atm). The results showed the average ear flap survival area in the experimental group was 82%, and it was 26.5% in the control group (p < 0.01). Histology demonstrated the existence of neovascularization in the experimental group. We have concluded that postoperative HBO therapy increases the survival of the rat ear composite graft, and that the effect of this therapy is influenced by the magnitude (size and thickness) of the graft.

Microsurgical replantation of the lip: a multi-institutional experience

Traumatic amputation of the lip is a rare yet devastating event affecting both form and function. Considering the available methods for reconstruction, replantation may offer a reasonable solution. We sought to characterize the variables associated with lip replantation and to assess the outcome in a retrospective review of 13 lip replantations performed in 12 institutions utilizing a form database and clinical and photographic analysis. Lip replantation was successful in all 13 patients; partial flap loss occurred in one patient owing to iatrogenic injury. Follow-up averaged 3.1 years. Average patient age at the time of injury was 21.1 years. There were six male and seven female patients. Injuries in two patients were the result of a human bite, the remaining injuries resulted from dog bites. One patient had significant associated injuries. Average length of hospital stay was 11.9 days. Ten patients suffered amputations of the upper lip, and three suffered amputations of the lower lip. Average defect size was 10.6 cm2. Operative time averaged 5.7 hours (range 2.5 to 12 hours). Warm ischemia time averaged 2.9 hours, and cold ischemia time averaged 2.7 hours. Donor and recipient veins were often scarce; all patients had at least one arterial anastomosis, whereas no vein was available in 7 of 13 patients; vein grafts were required in one patient. Leech therapy was employed in 11 of 13 patients. Anticoagulant therapy was administered in the majority of patients. Systemic heparin was utilized in 10 of 13 patients, low molecular weight dextran was used in 7 of 13 patients, and aspirin was given to 7 of 13 patients. One bleeding complication was incurred. An average of 6.2 units of packed red blood cells was administered to 12 of 13 patients (adjusted to 250 cc/unit). Antispasmodic therapy was employed in six of eight patients intraoperatively and in two of eight patients postoperatively. Intraoperative complications included difficulty identifying veins in 7 of 13 patients, arterial spasm in 1 of 13 patients, and vessel diameter < 0.5 mm in 4 patients. Postoperatively, one patient suffered vein thrombosis requiring anastomotic revision. Broad spectrum antibiotics were administered to all patients, and there were no infections. Nearly one-third (4 of 13) patients suffered prolonged edema lasting > 4 months. Color match of the replanted lip segment was rated excellent in all cases. Hypertrophic scarring occurred in 6 of 13 patients. A total of 12 revision procedures was performed in six patients. Interestingly, leech therapy resulted in permanent visible scarring as a result of the leech bite in 6 of 11 patients treated. Ten patients demonstrated active orbicularis muscle contraction in the replanted lip segment. Stomal continence was present in all lips. Sensibility return in the replanted lip segment was quite good with 12 of 13 patients demonstrating at least protective moving two-point sensibility (> or = 10 mm). Partial replant necrosis in one patient resulted in significant scar and contraction that compromised the aesthetic appearance. Overall, however, all patients were uniformly pleased with their final results. This clinical study is one of the largest of its kind on lip replantation. Although this represents a multi-institutional experience, the data are remarkably consistent. Re-establishment of venous outflow seems to be the most problematic technical challenge. By incorporating the adjuncts of anticoagulation, leech therapy, and antispasmodics, a successful outcome can be expected despite the paucity of vessels and small vessel size. The risks of blood transfusion, lengthy operative time, and hospital stay must be weighed against the functional benefits.

Transfer of the rat tail: an experimental model for free osteocutaneous transfer

A new experimental model for free transfer of the rat tail has been developed. The vascular and nerve anatomy of the tail was studied in ten Wistar rats. The caudal artery (average diameter: 0.8 mm) provides the principal arterial supply to the tail. The main venous drainage is from bilateral dorsolateral subcutaneous veins (average diameter: 1.2 mm). The inferior caudal trunk establishes the cutaneous nerve branches to the skin of the tail. Free transfer of the tail to the carotid artery and external jugular vein, with the attachment of the tail to the dorsum, allows for clinical monitoring of the transfer, without risk of autophagia. This transfer is easy to perform, simple to monitor, and provides consistent yet challenging microsurgery for the beginning microvascular surgeon. In addition to its utility as a training model, it may also have an application as an easy research model for composite tissue transfer.

Physeal growth arrest of the distal phalanx of the thumb in an adolescent pianist: a case report

A case of premature closure of the distal phalanx growth plate of the thumb is reported in an adolescent, presumably caused by accumulated repetitive trauma incurred during years of piano playing. The injury may be analogous to overuse injury to certain growth plates reported in child and adolescent athletes. Upper extremity problems in musicians due to the unusual and excessive demands of playing an instrument are discussed.

The effect of an implantable Doppler probe on the salvage of microvascular tissue transplants

One hundred forty-seven flaps in 135 consecutive patients undergoing microvascular transplantation were monitored using a miniature Doppler ultrasonic probe. Using a modification of a technique described previously by Swartz, the probes were secured to the outflow vein of the flap with Vicryl mesh. Twenty instances of thrombosis or spasm were detected in 16 patients, and all flaps were salvaged (100 percent). There were four false positive and no false negative results. This probe allows for safe, continuous monitoring of flap blood flow, which permits the rapid detection and hence rapid treatment of postoperative complications. Our experience suggests that a significant improvement in the salvage rate of microvascular transplants may be attainable with the use of this device.

A new heart failure model in rat by an end-to-side femoral vessel anastomosis

OBJECTIVE

The aim of this study was to develop a new shunting procedure for producing heart failure in the rat incorporating microvascular techniques and avoiding an abdominal operation.

METHOD

We performed an end-to-side anastomosis between the femoral vein and the femoral artery just proximal to their trifurcation into the saphenous, epigastric, and distal femoral vessels.

RESULTS

Of the 15 rats which underwent this procedure, six died within 48 h. The nine surviving animals were sacrificed and examined six weeks following surgery. All nine had developed cardiac hypertrophy and cardiac failure.

CONCLUSION

This model provides a relatively simple and reproducible means of creating high output heart failure and cardiac hypertrophy in the rat without necessitating abdominal surgery.

Blood-flow velocity as a factor in postoperative microvascular patency

The authors attempted to develop a reliable and reproducible new animal model in which the blood-flow velocity to a flap could be varied. This model was utilized to study the effects of different blood-flow velocities on the patency rate of small 1- to 2-mm vessels after common microsurgical procedures. Male Sprague-Dawley rats, weighing 450 to 550 gm, were used to develop a model creating either a "high blood flow" or a "low blood flow" state by ligating the rat femoral artery, either distally or proximally, to an epigastric artery based on a groin cutaneous flap. Blood-flow velocities were measured by microvascular flowmeter, and statistical analysis was performed on the data collected. The model was next used to determine the effects of different blood-flow velocities on the patency rates of rat femoral vessels after primary anastomosis vs interpositional vein grafting. Interpositional vein grafting was subsequently repeated by a more senior microsurgeon, to determine the potential effects of increased surgical experience. The animal model was reliable, easily reproducible, and efficacious in producing two separate groups of rats with significantly different blood-flow velocities (3.98 vs. 2.14 +/- 0.5 ml/min), as was confirmed by electromagnetic flowmeter and statistical analysis. In experienced hands, decreased blood-flow velocity did not result in decreased patency rates of these small vessels after primary anastomosis, or even after vein grafting. As long as microvascular vein grafting and primary anastomosis procedures are done properly, even 1-mm vessels can tolerate significantly decreased blood-flow velocity without a decreased patency rate. Although many known factors can contribute to thrombosis and failure of anastomoses in clinical microsurgery, blood-flow velocity appears not to be a significant factor. Also described is a new, reliable animal model that can be used in small-vessel blood-flow velocity studies.

DNA amplification determines donor-cell fate in cryopreserved skin allografts

Cryopreserved donor skin-cell survival was tested after allo- and isotransplantation by DNA amplification of male donor-cell genes which detects trace quantities of cells. Essentially, all cryopreserved allograft skin cells were rejected at the recipient site. Fine-haired, cryopreserved, belly skin of male BALB/c mice was transplanted onto the coarser-haired back of either female Swiss-Webster mice (allograft) or female BALB/c mice (isograft). Six weeks later, skin samples from the graft sites were tested by DNA polymerase chain reaction (PCR) amplification. Although allografts initially engrafted, more than 99.9 percent of male allograft skin cells were subsequently rejected, and gradually replaced by hairless host scar tissue. Clinically, all isografts, including hair follicles, engrafted permanently and maintained donor-cell SRY gene sequences in fine-haired graft site cells. Thus, cryopreservation maintained both the viability and antigenicity of mouse skin cells, because allografts were rejected and isografts survived. Furthermore, DNA amplification, quantified at multiple control dilutions and amplification cycles, can conclusively determine the fate of transplanted cells.

Arterialization of the venous system in a rat lower limb model

Creation of alternative vascular conduits has been one of the most challenging subjects in the history of vascular surgery. In the past, afferent arteriovenous fistulas have been used by vascular surgeons to rescue ischaemic extremities. We have undertaken a comprehensive investigation to characterize arterialization of the venous system at different levels of the rat lower limb. In Group 1 (n = 28), we performed an end-to-end anastomosis between the proximal saphenous artery and the distal saphenous vein (Superficial venous system), and ligated all other branches of the femoral artery. In Group 2 (n = 28), we performed an end-to-end anastomosis between the proximal saphenous artery and the distal femoral vein (Deep venous system). In Group 3 (n = 24), the control group, the femoral artery was ligated proximal to its trifurcation into the saphenous, epigastric, and distal femoral vessels. Group 4 (n = 10), the normal group, underwent no surgery. Animals were sacrificed at the first, third, and eighth postoperative weeks. Arteriographic, India ink injection, latex injection, and histological studies were performed on all groups. Successful arterialization of veins, significant neovascularization, and less ischaemic injury of muscles were noted in the arterialized vein groups (Groups 1 and 2) when compared with the ligated group (Group 3). This model appears to depict successfully arterialization of the lower limb venous system in a small animal model.

Using the Internet for rapid exchange of photographs and X-ray images to evaluate potential extremity replantation candidates

OBJECTIVE

To implement a low-cost system of transmitting high-quality digital photographs of mutilating extremity injuries using the speed of the Internet.

DESIGN

A high-resolution digital camera and simple hardware and software platform are used to take and transmit images via electronic mail. The images are received within minutes by the consultant, and an assessment can be made.

RESULTS

A low-cost and high-quality system can easily be implemented. Images can be seen by consultants only a few minutes after they are obtained. The quality of the reproductions is excellent, and they are handled exactly as other photographs.

CONCLUSION

This technique can be widely applicable and inexpensive to initiate in any emergency room. It allows rapid assessment of extremity injuries and x-ray images by expert consultants, who can then evaluate the replantation or revascularization potential of extremity trauma cases. This can eliminate unnecessary and often expensive transfer of patients who are not candidates for replantation.

Total ear replantation

Since the first report of successful microsurgical ear replantation in 1980, there have been 12 other cases reported in the English literature. As the number of trained microsurgeons increases, the opportunity to treat the amputated ear with microsurgical techniques should become more common. The reported cases have involved a variety of different mechanisms of injury and methods of treatment. There have been three techniques used to revascularize the amputated ear successfully: primary vascular repair, vein grafting, and use of the superficial temporal vessels as a pedicled vascular leash. Through our own experience and a review of the literature, we have been able to identify certain clinical characteristics that help dictate which technique to use. We report four cases of successful ear replantation, review the various techniques that have been used successfully, and provide treatment recommendations for future consideration.

A clinical study of end-to-end versus end-to-side techniques for microvascular anastomosis

The choice of microvascular anastomotic technique, end-to-end versus end-to-side, is still an item of debate. A review of the literature reveals no difference in patency rates in animal models where there is no size discrepancy. The available clinical evidence stems from Godina's early experience, proclaiming a higher failure rate with end-to-end anastomoses. Factors such as size mismatch and use of injured vessels, rather than anastomotic technique, may have been responsible. This clinical study examines the fate of over 2000 microvascular anastomoses performed in more than 900 tissue transplants. Complications attributable to the anastomosis were considered failures of the anastomosis, were tabulated, and were compared between the two techniques. The end-to-end and end-to-side microvascular techniques were found to be equally effective when properly applied. The choice of technique therefore should be secondary to factors influencing the choice of recipient vessel, such as the condition of the vessel, its accessibility, and the preservation or augmentation of maximal distal flow to an extremity.

Comparison of muscle mass preservation in denervated muscle and transplanted muscle flaps after motor and sensory reinnervation and neurotization

The gracilis muscle model was used either as a denervated muscle in situ or as a transplanted flap in 273 rats to compare the trophic effects of muscle reinnervation and neurotization using sensory and motor nerves. The average gracilis muscle flap weighed 626 +/- 94 mg at the time of the initial procedure. Experimental muscles were examined 6 months following the procedure. In denervated, nontransplanted muscles, both motor nerve reinnervation and neurotization resulted in significantly preserved muscle mass, averaging 570 +/- 69 and 521 +/- 116 mg, respectively, compared with the denervated control average of 178 +/- 22 mg (p < 0.05). Sensory nerve reinnervation and neurotization produced much smaller trophic effects (p > 0.05). In transplanted gracilis free flaps, however, only direct reinnervation with motor or sensory nerves resulted in improved bulk preservation, with average weights of 313 +/- 83 and 327 +/- 91 mg compared with the control average of 201 +/- 76 mg (p < 0.05). Neither sensory nor motor neurotization was significantly effective in the free-flap model (p > 0.05). These data suggest that transplantation may alter the response of muscle to reinnervation.

Midgestational sciatic nerve transection in fetal sheep results in absent nerve regeneration and neurogenic muscle atrophy

In order to test whether fetal nerve healing and regeneration result in complete functional recovery, we transected the sciatic nerve at trunk level in 13 midgestational sheep fetuses. In 10 fetuses immediate microsurgical nerve coaptation was performed. The neonatal lambs were evaluated clinically, electrophysiologically, and histologically. On the transected side, the 10 surviving lambs showed a sensorimotor sciatic nerve paralysis and atrophy of the muscles innervated by the sciatic nerve. Somatosensory evoked potentials were weakly present in 5 animals and absent in 5 animals. Histologically, minimal signs of axonal regeneration, massive degeneration of the entire nerve, and a marked neurogenic muscle atrophy were found. These unexpected results differ from the findings after peripheral nerve transections in late gestational sheep fetuses and also from the classic wallerian degeneration-regeneration pattern that follows adult nerve injury. We speculate that the almost absent regenerative potential at midgestation is related to axotomy-induced neurotrophic factor deprivation during a developmental phase where the neurons are critically dependent on growth factor for survival.

Salvage of the severely traumatized lower extremity

The use of microsurgical techniques has significantly altered the management of lower extremity trauma. Indications for amputation or salvage continue to change, as microsurgical transplants have become more commonplace. Reconstruction of a severely traumatized leg usually involves multiple complicated procedures, each of which can cause its own set of complications. The historically high rate of complications of these procedures and the fact that the resultant limb is never completely normal has led some to the conclusion that severely traumatized limbs should not be salvaged. In order to evaluate our own results in light of these considerations we have reviewed our most recent experience with this difficult problem.