Flap Formation Research Articles

Effect of ectopic epithelial tissue within the stroma on keratocyte apoptosis, mitosis, and myofibroblast transformation

The purpose of this study was to examine the effects of the epithelium on processes involved in stromal wound healing. Lamellar epithelial-stromal flaps were produced in rabbit corneas with a microkeratome. Peripheral corneal epithelial tissue, central corneal epithelial tissue, or no epithelial tissue (control) was introduced beneath the flap. Corneas were removed at time points from 4 hr to 1 month after surgery. Tissue sections were analyzed with immunocytochemistry for Keratin 3 (K3) to detect epithelial antigen, terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick-end labelling (TUNEL) assay to detect apoptosis, immunocytochemistry for Ki67 to detect cell proliferation, and immunocytochemistry for α-smooth muscle actin (SMA) to detect myofibroblasts. K3 was detected at the level of the interface from 4 hr to 1 month after surgery in corneas in which epithelial tissue was introduced, but not control corneas, with the exception of one that developed epithelial in growth. Keratocyte apoptosis was significantly higher at 4 hr after flap formation in both groups in which corneal epithelial tissue was introduced beneath the flap compared with controls. Keratocyte proliferation was significantly greater at 72 hr in corneas in which epithelial tissue was introduced beneath the flap compared to the controls. Corneas in which epithelial tissue was introduced into the interface, but not control corneas, had stromal cells expressing α-SMA in the stroma anterior and posterior to the interface at 1 week and 1 month after surgery. This was also noted in the control cornea in which there was epithelial ingrowth. Signals derived from the corneal epithelium promote keratocyte apoptosis. Keratocyte proliferation is higher in corneas that have lamellar surgery when epithelial tissue is introduced into the interface. Epithelium-derived signals also participate in the generation and/or maintenance of myofibroblasts in the corneal stroma.

Head and neck extension-fixation with a head frame for exposure of the distal internal carotid artery in carotid endarterectomy--technical note.

Adequate exposure of the distal internal carotid artery (ICA) for carotid endarterectomy may be difficult to achieve because of the position of the mandible and associated soft tissues. A simple yet effective use of a head frame is described to gain several centimeters of exposure of the distal ICA. The patient's head and neck are fixed in an extension position using a radiolucent head frame. Nasotracheal intubation and secure taping of the chin are also employed to keep the mouth closed and to prevent the mandible from spontaneously hanging down. The head frame tightly fixes the patient's neck, so the mandible does not disturb the surgical field throughout the operation. This simple method maximizes exposure of the distal ICA. The radiolucent head frame also enables intraoperative angiography to confirm the patency of the ICA and the absence of flap formation. This simple technique is useful for exposing the distal ICA.

Induced optical aberrations following formation of a laser in situ keratomileusis flap

Purpose To determine how refractive error, visual acuity, and high-order aberrations (3rd- and 4th-order) are affected by the formation of a lamellar corneal flap during laser in situ keratomileusis (LASIK). Setting University refractive surgery center. Methods The effect of lamellar corneal flap formation was analyzed in 15 myopic eyes (mean preoperative refraction −4.72 diopters [D] [range −1.25 to −7.25 D]). The flap was created using a 2-step procedure: (1) a nasally hinged lamellar corneal flap was created; (2) the flap was lifted and stromal ablation performed 2 months after the flap was made. A Hartmann-Shack aberrometer was used to measure the aberrations. Results There was no significant change in the refractive error (spherical equivalent pre-flap −4.72 ± 1.99 D and post-flap −4.62 ± 1.99 D [ P = .28]) or visual acuity (pre-flap uncorrected visual acuity [UCVA] 0.07 and best corrected visual acuity [BCVA] 0.96; post-flap UCVA 0.08 and BCVA 0.95 [ P = .16 and P = .33, respectively]). A statistically significant increase in total higher-order wavefront aberrations was observed following flap formation (root mean square pre-flap 0.344 ± 0.125 and post-flap 0.440 ± 0.221 [ P = .04]). Conclusion Flap formation during LASIK can modify the eye’s existing natural higher-order aberrations (especially spherical and coma-like aberrations along the axis of the flap’s hinge), while visual acuity and refractive error remain unaffected.

Lack of a significant effect of deletion of the tachykinin neurokinin-1 receptor on wound healing in mouse skin

The tachykinin neurokinin-1 (NK 1) receptor mediates the vasoactive effects of substance P and related members of the tachykinin family. Substance P acts via the NK 1 receptor to mediate increased microvascular permeability leading to oedema formation as confirmed in NK 1 receptor knockout mice. In addition there is evidence that neuropeptides such as substance P can have a modulatory effect on the wound-healing process. In this study male and female wild-type and NK 1 knockout mice were investigated for their comparative ability to induce acute oedema formation in response to topical application of capsaicin, as measured by the extravasation of intravenous radiolabelled-albumin, and wound healing in response to a cut, as measured by area of wound over the following days. Significant ( P<0.001) oedema, approximately three-fold over basal, was induced by capsaicin in both male and female wild-type mice, an indicator of a similar responsiveness irrespective of sex. However, as expected, the oedema was not observed in the knockout mice. Wounding was achieved through a 1-cm full-thickness cut into the interscapular area of dorsal skin. Wound healing was then followed in two different protocols. The wound was left to heal naturally over 14 days in the first protocol and no significant changes in healing were observed in wild-type compared to knockout. In the second protocol, the skin was sutured open for the first 48 h, to prevent the elasticity of the skin from initiating a natural healing process through flap formation. This caused a significant increase in the area of the wound. Despite this, wounds in both wild-type and knockout mice healed in an identical manner that was complete after 17 days. In conclusion, it is shown that deletion of a functional NK 1 receptor has little effect on wound healing in response to a simple cut in mouse skin.

Discussion by Eric D. Donnenfeld, MD

Dr. Busin et al have evaluated the effect of performing a hinged lamellar flap on refraction, visual acuity, and corneal topography in postkeratoplasty eyes with high astigmatism. Their data suggest that graft/host wound biomechanics are influenced by the lamellar cut that occurs in laser in situ keratomileusis (LASIK) after penetrating keratoplasty. They note a reduction in refractive sphere and cylinder up to 3 months after formation of the lamellar flap and suggest that LASIK after penetrating keratoplasty be performed as a two-step procedure to improve predictability of results. In addition, some patients may not require excimer laser photoablation because of reduction in cylinder and sphere, which is associated with flap formation.

Experience With the Nidek MK-2000 Microkeratome in 1220 Cases

To evaluate the performance of the Nidek MK-2000 microkeratome. The Nidek MK-2000 microkeratome was used in 1,220 cases of LASIK with the Nidek EC-5000 excimer laser. Patients had a wide range of myopia (-0.75 to -25.00 D), hyperopia (+0.75 to +9.00 D) and/or astigmatism (-7.00 to +6.50 D). The flap was created with the 130-microm microkeratome plate for 859 eyes, and the 160-microm plate for 361 eyes. In 632 eyes, the 8.5-mm ring was used, and the 9.5-mm ring was used in 588 eyes. The flap hinge was placed nasally, superiorly, or inferiorly depending on the needs of the case. An easy external modification allowed us to gently increase and decrease the vacuum level and to perform the procedure using a low vacuum regimen, if necessary. The edges of the flaps and the corneal surface were of good quality in all eyes. No free flaps were noted. One case was aborted because of inappropriate flap formation in a patient with a large difference (6.50 D) in corneal curvature in two main meridians. This patient successfully underwent LASIK 1 month later, placing the flap hinge in the opposite direction. Small epithelial shrinkage was noted in 38 eyes. No other flap complications were noted. In all patients the flap diameter and thickness were close to that estimated by the manufacturer. The vacuum level was adequate and stable in all cases. The Nidek MK-2000 microkeratome was easy to use, predictable, and safe. However, we suggest a modification, adding an adjustable head movement to create wider hinge-to-center-of-pupil distance and an additional 9.0-mm suction ring.

Pedicled bone flap formation using transplanted bone marrow stromal cells.

Transplanted osteoprogenitor cells derived from cultured bone marrow stromal cells (BMSCs) can be used to fabricate pedicled bone flaps. Prospective, randomized experimental trials. Basic science research laboratory. Immunodeficient female NIH-Bg-Nu-Xid mice, aged 3 months. The BMSCs were harvested from the long bones of C57Bl/6 transgenic mice carrying the type Ialpha1 collagen-chloramphenicol acetyl transferase reporter gene construct; their numbers were expanded in tissue culture. Treated mice received BMSC transplantations around the common carotid artery and internal jugular vein, the aorta and its venae comitantes, or the saphenous artery and vein; control mice received a sham transplant in comparable recipient sites. Mice underwent harvesting from 4 weeks to 2 years after transplantation. Transplants were evaluated via histological, immunohistochemical, and angiographic analyses. Compared with the controls, which formed no bone, 32 of 37 BMSC-containing transplants formed a vascularized bone island that was perfused specifically and solely by its common carotid artery vascular source. Mature transplants consisted of well-developed lamellar, corticocancellous bone whose osteocytes were derived from the grafted BMSCs; hematopoietic tissue derived from the recipient mouse. Transplants formed as early as 4 weeks and remained stable in size as late as 108 weeks. Bone marrow stromal cells can be used to create vascularized bone flaps in mice; these bone constructs are vascularized by their pedicle and therefore can potentially be transferred to a recipient site using microsurgical techniques. These findings provide proof of principle of an additional clinical application of BMSC transplantation techniques.

Evolution toward dissection of an intramural hematoma of the ascending aorta

Intramural hematoma of the aorta is a condition increasingly observed in clinical practice. Uncertainty exists whether such lesions represent a different pathology or simply the precursors of classic dissecting aneurysm. The patient was a 76-year-old woman with intramural hematoma of the ascending aorta. Clinical course, progression of the lesion to type A aortic dissection, and surgical treatment are described. Although natural history of intramural hematoma of the ascending aorta is not clearly elucidated, the case presented confirms that the evolution toward intimal flap formation is possible and that we cannot foresee the stabilization of these lesions. We stress that intramural hematoma of the ascending aorta has to be managed as an aortic type A dissection and that aggressive treatment is advisable.

Effect of resection velocity and suction ring on corneal flap formation in laser in situ keratomileusis

PurposeTo determine the effects of microkeratome-cutting velocities and the suction ring on corneal flap creation. SettingDepartment of Ophthalmology, College of Medicine, The Catholic University of Korea, Seoul, Korea. MethodsProcedures were performed under clinical settings in 65 pig eyes. Keratometric diopters (D) were measured before and after application of the suction ring. Corneal thickness was measured before and after resection cutting, and the difference was taken as flap thickness. The microkeratome was initially set at a resection thickness of 160 μm. The blade oscillation (turbine velocity) was set at 30, 35, and 42 psi. The translational velocity was arbitrarily divided into high (1 to 2 seconds), moderate (3 to 5 seconds), and low (6 seconds or more). Data were analyzed by varying the velocities consecutively. Photographs of the cut surface were acquired by scanning electron microscopy to evaluate resection morphology by comparison. ResultsMean refractive powers were 39.94 D ± 0.66 (SD) and 39.69 ± 0.98 D before and after application of the suction ring, respectively; however, no significant difference was observed (P = .216). Lower surgeon translational velocity resulted in a significantly thicker corneal flap in 8 of the 9 paired comparisons (P < .05). Higher turbine velocity resulted in a significantly thicker corneal flap in 7 of the 9 paired comparisons (P < .05). The cut surface was smoother at higher turbine and lower translational velocity. The initial cut margin was steeper at higher translational velocity. ConclusionsThe increase in intraocular pressure induced by the suction ring had no significant effect on keratometric power. At higher turbine and lower translational velocities, the corneal flap was thicker and the cut surface smoother. Higher translational velocities made the initial cut margin steeper.

Corneal perforation during laser in situ keratomileusis

Two cases of corneal perforation that occurred during laser ablation but not during flap formation in laser in situ keratomileusis (LASIK) are reported. In the first case, no problem in flap formation occurred, and stromal bed thickness was assumed to be about 239 μm after laser application. However, a stromal bed perforation was found when 608 pulses were applied (theoretical ablation depth was 140 μm). Excessive dehydration due to prolonged exposure to the operating microscope light may change the ablation rate and cause corneal perforation. In the second case, LASIK retreatment was performed using the original flap for correction of regressed myopia (−4.0 diopters). Although the stromal bed thickness was assumed to be about 175 μm after the laser application, a stromal bed perforation was found when 151 pulses were applied (theoretical ablation depth was 37 μm). Unexpected corneal ectasia after the first LASIK treatment may cause a corneal perforation in LASIK retreatment. In conclusion, excessive dehydration of the cornea should be avoided, and careful examination of the corneal shape is necessary to prevent corneal perforation during laser ablation in LASIK.

Combined method for the restoration of radial and ulnar margin of the hand

New approach to fingers reconstruction which provides the achievement of adequate functional outcome and minimum loss for donor sites is elaborated. The indications to this method are given. It is detected that the use of the blood-supplied segments of tubular bones enables to form the bone base of finger resistant to the resorption. It is also shown that in the forming of first interfinger interval is reasonable to use dermal-fatty flaps on temporary nutrition pedicles. The method of double flap formation for the prevention of necrosis is suggested.

Dilatation mechanism of balloon angioplasty in children: assessment by angiography and intravascular ultrasound.

Little information is available about the dilatation mechanism in children. This prospective study aimed to (1) evaluate the dilatation mechanism of balloon angioplasty in children with arterial stenosis, and (2) compare the morphological changes seen by intravascular ultrasound (IVUS) and angiography. Twenty consecutive patients, who had undergone a total of 23 procedures, were examined before and immediately after balloon angioplasty with a 4.3 Fr, 30 MHz rotational tip IVUS system. The lesions for IVUS study had resulted from coarctation of the aorta in six patients, pulmonary arterial stenosis in five, Blalock-Taussig shunt stenosis in three, subclavian artery stenosis in two, renal artery stenosis in two, coronary artery stenosis in one and ductus arteriosus in one. Four distinctive morphological types were identified: type I with arterial stretching, type IIa with superficial tearing, type IIb with deep intimal-medial tearing, type III with flap formation, and type IV with dissection. The diameter of the narrowest site before and after balloon angioplasty increased significantly from 2. 1 +/- 1.4 mm to 4.6 +/- 3.4 mm (p < 0.001). Eighteen of the 23 angioplasty procedures (78%) were considered to be successful, with a dilatation ratio of more than 50%. In most patients with successful dilatation, non-stretch mechanisms such as tearing, flap formation, or dissection were found. The positive percent (70%) of non-stretch mechanisms seen by IVUS was significantly higher than the positive findings (39%) by angiography (Chi2 = 6.47, p < 0.02). Non-stretch morphology of the arterial wall may be a common mechanism of dilatation after balloon angioplasty in children with arterial stenosis. IVUS is a useful modality for evaluating the effectiveness of balloon angioplasty and the mechanism of dilatation in individual cases.

Combined carotid endarterectomy and coronary artery bypass graft.

Atherosclerosis is a generalized disease which afflicts a considerable number of patients in both the carotid and coronary arteries. Although the risk of stroke or death use to combined carotid endarterectomy (CEA) and coronary artery bypass graft (CABG) is thought to be higher than that of each individual operation, the combined procedure is generally preferred over staged operations to treat such patients. We performed the combined procedure safely with the aid of intraoperative portable digital subtraction angiography (DSA). This report describes our experience with the operative strategy of simultaneous CEA and CABG. Ninety CEA and 404 CABG were carried out between January 1989 and December 1997. A total of six patients received the combined procedure with the aid of intraoperative DSA; they were studied retrospectively. Postoperative mortality and morbidity after the combined procedure was 0%. In the combined procedure, neurological complications are difficult to detect after CEA because the patient must be maintained under general anesthesia and extracorporeal circulation during the subsequent CABG. However, intraoperative DSA can confirm patency of the internal carotid artery and absence of flap formation after CEA, and the CABG can be performed safely. Intraoperative portable DSA between CEA and CABG is helpful in preventing perioperative stroke in the combined procedure.

Induction of rabbit cyclooxygenase 2 in the anterior uvea following glaucoma filtration surgery

PURPOSE. This study was undertaken to evaluate for the presence of cyclooxygenase 2 (COX2) gene expression in the anterior uvea of rabbits following glaucoma filtration surgery. METHODS. One of the following surgical procedures were performed on the right eye of New Zealand white albino rabbits: (1) paracentesis (2.5 mm limbal incision); (2) iridectomy through a 2.5 mm limbal incision; (3) lamellar scleral flap formation or (4) full glaucoma filtration surgery. The animals were sacrificed within 3 hours of post-surgery, and the anterior uveal tissues were isolated. Polymerase chain reaction-based techniques were employed to assay for the presence of COX2 transcript. RESULTS. A partial coding sequence of the previously unreported rabbit COX2 gene was obtained. COX2 mRNA was detected in the operated eyes of animals that underwent either full filtration surgery or iridectomy through a limbal incision. CONCLUSIONS. In normal rabbit anterior uveal tissue, there appears to be minimal expression of COX2 message. After experimental glaucoma filtration surgery, there is rapid induction of COX2 message.

Picosecond laser in situ keratomileusis with a 1053-nm Nd:YLF laser.

Excimer laser in situ keratomileusis requires a microkeratome to generate an anterior corneal flap, plus an excimer laser to ablate the underlying stromal tissue. In this paper we introduce the concepts of laser flap formation and in situ keratomileusis using a picosecond laser. A neodymium-doped yttrium-lithium-fluoride (Nd:YLF) laser with a plano-plano quartz applanation lens was used to generate various patterns of intrastromal photodisruption in human donor eyes to fashion anterior corneal flaps and generate intrastromal lenticules. Smooth intrastromal dissections, 6 mm in diameter, were generated 160 microns below the corneal surface when the laser delivered pulses at 1 kHz with energies of either 40 microJ/pulse or 60 microJ/pulse, placed 20 microns apart in an expanding spiral. This enabled us to fashion anterior corneal flaps. The ease of the surgery and quality of the dissection corresponded well, and it was evident that both deteriorated noticeably when the laser pulses were separated by 25 microns or 30 microns, regardless of pulse energy. Using 40 microJ laser pulses placed 20 microns apart we also created a 5-mm diameter, 320 microns thick (130 microns-450 microns deep) stromal lenticule below a corneal flap that was easily extracted when the flap was raised. Anterior corneal flaps were easily fashioned using a Nd:YLF laser. Picosecond laser in situ keratomileusis with a Nd:YLF laser could offer a favorable alternative to combined microkeratome/excimer laser in situ keratomileusis.

Porcine model of stent thrombosis: platelets are the primary component of acute stent closure.

Acute stent thrombosis remains a major concern of coronary stent implantation. Animal studies using stents do not adequately mimic this clinical problem, since stent placement is rarely associated with acute closure. The purpose of this study was to develop and characterize a porcine model of stent thrombosis. Improved understanding through such a model may be useful toward preventing and treating acute stent closure. Whole blood was drawn from domestic crossbred swine one day before study. Platelets were isolated, labeled with 111-In tropolone, and reinjected within 18 hr of the study. Bilateral carotid arteries were exposed, and severe injury induced by a series of mechanical crushes. This method produced histologic injury similar to human coronary angioplasty, with medial disruption and large dissections protruding into the lumen. Stenting was performed in standard fashion with 3.5-mm JJIS stents. Local platelet deposition was measured and recorded as 111-In radioactivity using a miniaturized scintillation detector (Dosimeter Corp.) mounted directly at the artery injury site. This measurement was made in real time at 1-min intervals. Similarly, volumetric blood flow was measured in real time by Doppler flowmeter. Eighteen arteries of nine pigs were studied. In nine arteries from nine pigs, crush injury only was performed and monitored. In the contralateral artery, crush injury was followed immediately by placement of a 3.5-mm Palmaz-Schatz (coronary) stent. Blood flow decreased rapidly following injury in both groups and followed a cyclic pattern. Eight arteries of the crush alone and two arteries of the crush plus stent groups were totally occluded 1 hr after crush. 111-In counts normalized to baseline were significantly higher at 1 hr in both groups compared to baseline; in the stented group, counts were higher than in the unstented group. Blood flow was higher in the stented group than in unstented group for 1 hr. Histopathologic observation of the thrombi forming in both crush-only and crush-stent injuries showed severe medial dissections with obstructing medial flap formation. The thrombi forming in both groups were highly platelet rich. This model of stent and arterial thrombosis showed rapid formation of platelet-rich thrombus, cyclic blood flow variations, and acute occlusion in 20% of cases. Stent placement at arterial injury sites is associated with thrombus that is predominantly platelet rich. Stent placement at injury sites enhances platelet deposition over crush injury alone. Despite greater numbers of platelets, as shown by increased 111-In counts, stenting improved vessel patency. These were likely due to higher volumetric blood flow, continuous deposition, and embolization of labeled platelets.

Conservative management of transverse partial flexor digitorum profundus tendon lacerations in zone 2

The experience with six patients managed conservatively following transverse partial flexor digitorum profundus tendon lacerations in zone 2 is presented. Four patients who were mobilized using elastic traction experienced no triggering; however, two patients who had unrestricted mobilization immediately following injury developed triggering. The mechanism of triggering and tendon flap formation in the clinical cases is discussed.

Long-term fate and effects of exercise on sternal cartilage autografts used for repair of large osteochondral defects in horses

Summary Bilateral osteochondral defects (10 mm2 × 3 mm deep) were created on the distal articular surface of the radial carpal bone of ten, 2- to 3-year-old horses. One defect of each horse was repaired, using a sternal cartilage autograft (treated), and the other was left untreated (control). The horses were exercised on a high-speed treadmill at incrementally increased speed and duration over the course of 12 months. Horses were evaluated arthroscopically at 6 to 7 weeks, and clinical examinations were conducted weekly at exercise. Twelve months after surgery, carpuses of each horse were radiographed and clinically examined prior to euthanasia. A gross pathologic evaluation of each joint was conducted, and samples were collected for histologic, histochemical, histomorphometric, and biochemical evaluation. Radio-graphically, the grafted joints had more extensive evidence of arthropathy, and clinically, 8 of the 10 horses were more lame in the grafted limb. On the basis of histomorphometry, the repair tissue of the grafted defects contained a greater median percentage of hyaline cartilage (45%) than that of control defects (4.5%), and the control defects contained a greater percentage of fibrocartilage (82%) than did grafted defects (28.5%). A greater median percentage of repair tissue stained with safranin-O in the grafted defects (24.5%) than in the control defects (3.5%). On gross pathologic and histologic evaluation, repair tissue of the control defects had better continuity and was more firmly attached to the subchondral bone than was repair tissue of the grafted defects. Repair tissue of the grafted defects had extensive fissure and flap formation. Histologically, subchondral bone reactivity and fibroplasia was extensive in grafted joints. Repair tissue of grafted defects had a greater percentage of type II collagen (mean ± SEM, 83.5 ± 2.95%) than did controls (mean, 79.4 ± 3.87%) that was not statistically significant. Hexosamine content was significantly higher (P &lt; 0.05) in repair tissue of the grafted defect (mean, 28.9 ± 3.00 mg/g of dry weight) vs control (mean, 20.6 ± 1.85 mg/g of dry weight). On the basis of this experimental model, sternal cartilage autografts cannot be recommended at this time for repair of osteochondral defects in athletic horses.

Mobility of the Intimal Flap and Thrombus Formation in Aortic Dissection: A Transesophageal Echocardiographic Study

The mechanisms of the motion of the intimal flap and of thrombus formation in acute or chronic aortic dissection are not definitively elucidated. Transesophageal echocardiography seems to be a technique of choice to analyze the flow in the true and false lumina. Twenty‐one consecutive patients were studied in order to define the mobility of the intimal flap, the color Doppler flow patterns, the presence of spontaneous echocardiographic contrast, and thrombus formation at different levels of the aorta. The results suggest that clotted false lumen is more often seen in chronic aortic dissection at the level of the descending thoracic aorta. However, thrombosed false lumen in the aortic arch is suggestive of a retrograde aortic dissection. In cases of complete obliteration of the false lumen, the differentiation between aortic dissection and aortic ectasia with mural thrombus may be extremely difficult.

Triggering after partial tendon laceration

Triggering and tendon flap formation were studied after a transverse laceration of 50% of the width of the flexor digitorum profundus tendons of the hind limb of 14 adult sheep at various intervals after injury. The tendon laceration was not repaired and there was no post-operative immobilization. Triggering was not caused by bulbous scar formation but by the bunching of the tendon fibres proximal or distal to the laceration site. This bunched part of the tendon appeared to become incorporated into the healing process, with gradual spontaneous resolution of triggering. Failure of incorporation of this bunched part resulted in the formation of a flap in two tendons.