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PubMed2005

Validation of traction force indicator in ventouse devices.

OBJECTIVE: To evaluate whether the traction force indicator in a ventouse device gave an accurate estimation of the force applied. METHODS: The study was carried out at the Derby City Hospital. An estimate of measurement errors was made by analyzing the standard deviation of the residuals for 30 Kiwi OmniCup devices (Clinical Innovations, Abingdon, Oxfordshire, England) and a standard industrial spring balance. RESULTS: The measurement errors for the traction forces were very small and acceptable for the OmniCup. The overall estimate of measurement errors was 0.45 kg (1.35 lb). CONCLUSION: The overall measurement error for the traction force indicator of the OmniCup was found to be very small. Injuries associated the ventouse, such as cephalohematomas and subgaleal hemorrhages, may be minimized if the recommended limits for a safe traction force are not exceeded.

Biomechanical Phenomena↗

PubMed2004

Treatment of refractory mesenteric traction syndrome without cyclooxygenase inhibitors.

Mesenteric traction may be necessary for surgical exposure during colonic or aortic surgery. Traction on the mesentery releases prostacyclin, producing variable degrees of hypotension. Numerous cases of severe, life-threatening hypotension have been reported. The published literature suggests that treatment of severe hypotension from mesenteric traction with routine doses of vasoconstrictors may be ineffective, but inhibition of prostacyclin synthesis with cyclooxygenase inhibitors can successfully treat or prevent hypotension. This rationale, while highly beneficial, would place patients with allergies to cyclooxygenase inhibitors at a severe disadvantage, and would also leave no therapeutic options if intravenous cyclooxygenase inhibitors were not immediately available. We report the successful use of high-dose phenylephrine in the treatment of mesenteric traction syndrome.

Colitis, Ulcerative↗

PubMed1995

Course of vitreomacular traction syndrome.

PURPOSE: Although the course of vitreomacular traction syndrome is necessary to treat patients or to establish the value of the surgical technique, little information is available about its course. In this study, we ascertained the natural history of vitreomacular traction syndrome. METHODS: We retrospectively studied 53 consecutive symptomatic eyes with vitreomacular traction syndrome. RESULTS: In 43 (81%) of 53 eyes with cystoid macular changes at the diagnostic examination, 29 (67%) of 43 had cystoid changes that persisted during the median follow-up period of 60 months. The visual acuities at the time of the final examination decreased two Snellen lines or more from the initial measurement in 34 (64%) of 53 eyes. During the follow-up period, six (11%) of 53 eyes developed complete posterior vitreous detachment. The number of eyes with resolved cystoid changes or stable visual acuity was significantly higher when complete vitreomacular separation occurred (six of six) than when it did not (three [8%] of 37, P = .01; 13 [28%] of 47, P = .01). CONCLUSIONS: Most symptomatic eyes with vitreomacular traction syndrome underwent a further decrease in visual acuity. Complete vitreomacular separation, which occurs infrequently in eyes with the disorder, allows resolution of cystoid changes and improvement of visual acuity.

Aged↗

PubMed2000

Photoreceptor-specific expression of platelet-derived growth factor-B results in traction retinal detachment.

Expression of platelet-derived growth factor (PDGF)-A and PDGF-B is increased in patients with proliferative retinopathies in which traction retinal detachments occur. Previous studies have demonstrated that increased expression of PDGF-A in the retina of transgenic mice results in retinal gliosis due to proliferation of astrocytes with different retinal phenotypes based on the time of onset and location of the PDGF-A production. In this study, we investigated the effects of PDGF-B in the retina using gain-of-function transgenic mice that express PDGF-B in photoreceptors. These mice show proliferation of astrocytes, pericytes, and, to a lesser extent, endothelial cells, resulting in ectopic cells on the surface and extending into the retina. The sheets of cells exert traction on the retina resulting in traction retinal detachments similar to those seen in humans with proliferative retinopathies. These studies suggest that PDGF-B has more dramatic effects in the retina than PDGF-A, because it acts on additional cell types, in particular on pericytes, which have a highly developed contractile apparatus. These studies in the retina suggest a means that could be used in other tissues throughout the body to achieve graded PDGF effects. They also provide a new model of traction retinal detachment that can be used to investigate new treatments for patients with proliferative retinopathies.

Animals↗

PubMed1999

Diabetic maculopathy induced by vitreo-macular traction: evaluation by optical coherence tomography (OCT).

AIM: To evaluate the role and efficacy of optical coherence tomography (OCT) in the evaluation of diabetic maculopathy induced by vitreo-retinal traction. METHODS: 12 patients affected by diabetic maculopathy induced by vitreo-retinal traction were examined using biomicroscopy with a three-mirror contact lens, fluorescein angiography (FA) and OCT scanning in order to identify the presence of a vitreomacular traction. RESULTS: OCT revealed two patterns of maculopathy which were characterised by a thickening of the superior profile of the OCT tomogram or by the disappearance and inversion of the physiologic foveal depression respectively. CONCLUSIONS: OCT may be useful in the characterisation and monitoring of diabetic maculopathy induced by vitreo-retinal traction.

Aged↗

PubMed1997

Macular-threatening traction detachment of the retina in diabetic proliferative retinopathy, treated by laser.

PURPOSE: To treat patients with traction detachment of the central retina by laser in order to avoid vitrectomy. METHODS: Focal treatment of and around the flat detached retinal area with the argon laser. RESULTS: Seven patients were treated for macular-threatening traction detachment of the retina. The non-rhegmatogenous traction detachment was flat and circumscribed. Panretinal photocoagulation (PRP) with the argon laser was performed prior to treatment of the traction in three of the cases, in four it was carried out in addition to PRP. In each of the seven patients partial or complete reattachment and stabilization for many years was achieved, rendering vitrectomy unnecessary (mean follow-up after therapy: 40.1 months). In no case was a laser-induced hole produced, and in no patient did the visual acuity decrease. CONCLUSION: The favourable results following photocoagulation can be explained by the tight retinal/choroidal scar formation (laserpexy). Laserpexy is only recommended for eyes with slight initial detachment.

Adult↗

PubMed1984

[Histology and therapy of diabetic traction detachment].

Diabetic tractional detachment of the retina is caused by shrinking processes of the vitreous, which at most detaches only partially, and by shrinking of epiretinal proliferations. The shrinking of the vitreous results in tractional forces working centripetally and toward the base of the vitreous. The shrinking of the epiretinal proliferations, however, results in a tangential gathering of the retina. The two processes are usually found together in diabetic tractional retinal detachment. Treatment consists of a vitrectomy to eliminate the centripetal forces and tractions to the vitreous base. Further relief and unfolding of the retina is achieved by segmentation of the epiretinal membranes. Additional conventional retinal surgery procedures and implantation of silicone oil may become necessary in especially unfavorable cases. The surgical technique is explained with examples of typical situations.

Adult↗

PubMed1997

A micromachined device provides a new bend on fibroblast traction forces.

We have measured the traction forces generated by fibroblasts using a novel micromachined device that is capable of determining the subcellular forces generated by individual adhesive contacts. The front of migrating fibroblasts produced intermittent rearward forces whereas the tail produced larger forward directed forces. None of the forces were steady; they all had periodic fluctuations. The transition between forward and rearward traction forces occurred at the nucleus, not at the rear of the cell or the border between the endoplasm and the ectoplasm. We propose that the coupling of lamella extensions to fluctuating rearward tractions in front of the nuclear region move the front of a fibroblast forward, while force-facilitated release of rear adhesive contacts and anterior-directed tractions allow the region behind the nucleus to advance.

Animals↗

PubMed1989

The role of prostacyclin in the mesenteric traction syndrome during anesthesia for abdominal aortic reconstructive surgery.

Mesenteric traction syndrome consists of sudden tachycardia, hypotension, and cutaneous hyperemia, and frequently occurs during mesenteric traction in patients undergoing abdominal aortic aneurysm (AAA) reconstructive surgery. The etiology and clinical impact of this phenomenon are unknown, but the symptoms suggest a release of vasoactive materials from the mesenteric vascular bed. Thirty-one patients who underwent AAA surgery were studied. Mesenteric traction was accompanied by a decrease in systolic (p = 0.005) and diastolic (p less than 0.05) blood pressures, and in systemic vascular resistance (p less than 0.005), and was accompanied by an increase in heart rate (HR) (p less than 0.005), and cardiac output (p = 0.01). These hemodynamic changes coincided with an increase (p less than 0.001) in plasma concentrations of 6-keto-prostaglandin F1 (6-K-PGF1). No apparent change was found in prostaglandin E2, thromboxane B2, and histamine concentrations. The concentration of 6-K-PGF1 was correlated with diastolic blood pressure (r = -0.52, p less than 0.005) and HR (r = 0.65, p less than 0.001). Cutaneous hyperemia was observed in 58% of the patients. In an additional six patients, who had taken aspirin daily before AAA surgery, no significant changes were observed in the hemodynamic measurements or 6-K-PGF1 concentrations. These data suggest that mesenteric traction syndrome may be mediated at least in part by a selective release of prostacyclin.

6-Ketoprostaglandin F1 alpha↗

PubMed1995

Vitrectomy for vitreomacular traction syndrome with macular detachment.

PURPOSE: To describe the clinical characteristics of the vitreomacular traction syndrome with macular detachment and to report our surgical experience with this condition. METHODS: A retrospective chart and photographic review was performed on nine patients (nine eyes) who had a symptomatic decrease in visual acuity from a macular traction retinal detachment caused by vitreomacular traction syndrome. Vitrectomy was performed in each eye to reattach the retina. RESULTS: Intraoperative observation confirmed partial posterior vitreous separation with adherence of the posterior hyaloid to the detached retina and separation of the posterior hyaloid from the attached retina. After surgery the macula was reattached in seven eyes (78%). Visual acuity was improved in four eyes, stable in four eyes, and worse in one eye. CONCLUSION: Macular detachment may occur secondary to vitreomacular traction syndrome. Although the retina may be reattached surgically in these cases, visual improvement may be limited by chronic detachment, premacular fibrosis, cystoid macular edema, or macular schisis.

Aged↗

PubMed2002

Tenon's traction sutures: an aid for trabeculectomy and aqueous drainage device implantation.

PURPOSE: To describe a surgical technique to improve visualization and surgical access for trabeculectomy and implantation of aqueous drainage devices. MATERIALS AND METHODS: After the corneal traction suture (6-0 polygalactin; S-29 needle) is placed, a second suture is passed through Tenon's capsule alone, either at the anterior edge of a limbus-based conjunctival flap for trabeculectomy or at the incisional edge of a fornix-based conjunctival flap for drainage implant surgery. RESULTS: The incision for limbus-based peritomies must be posterior enough to take advantage of the posterior thickening of Tenon's capsule when placing the traction suture. The use of traction sutures enhances visualization and limbal surgical access for trabeculectomy. They also enhance posterior ocular surface visualization and aid placement of scleral fixation sutures for securing the explants of aqueous drainage devices. CONCLUSIONS: Tenon's traction sutures are an aid to visualization and to surgical access during glaucoma filtering surgery.

Connective Tissue↗

PubMedDate not supplied

Tibial physeal closure and genu recurvatum after femoral fracture: occurrence without a tibial traction pin.

Two cases of premature closure of the anterior portion of the proximal tibial physis with associated genu recurvatum deformity in adolescent males who had sustained a closed femur fracture are reported. In both cases, physeal closure occurred without use of a proximal tibial traction pin. In one patient, treatment included distal femoral pin traction; the other patient was treated with skin traction followed by spica cast. We believe that development of recurvatum of the tibia after femoral fracture in children is not necessarily iatrogenic and related to a tibial traction pin, but instead may result from physeal injury incurred at the time of the original trauma.

Child↗

PubMed1996

Management of fixed divergent squint in third nerve palsy using traction sutures.

BACKGROUND: Long-standing fixed divergent squint is a difficult management problem, presenting marked cosmetic and functional symptoms in the patient, and a significant challenge for the squint surgeon to overcome. METHODS: We describe use of through-the-lid traction sutures in 24 consecutive patients with fixed divergent squint secondary to long-standing third nerve palsy. Very large recessions of the lateral rectus were combined with large resections of the medial rectus and traction sutures placed through the insertions of the superior and inferior rectus were brought out through the extreme medial fornices and skin of the upper and lower lids. Sutures were tied over tarsorrhaphy bolsters and left in situ for six weeks. RESULTS: After removal of the traction sutures, the eye maintained a good cosmetic position in all but two cases. Postoperative motility was extremely limited or absent. Complications were limited to transient skin ulceration in two cases. CONCLUSIONS: Supramaximal horizontal recess-resect procedure combined with adducting traction sutures left in situ for six weeks in a safe and effective procedure to restore the eye to the centre of the palpebral fissure.

Adolescent↗

PubMedDate not supplied

Cyclic traction machine for long-term culture of fibroblast-populated collagen gels.

Our research group has been investigating the effect of cyclic deformations on the evolution of fibroblast populated collagen gels (FPCG). Since existing traction machines are not designed for such an application, we had to design a cyclic traction machine adapted to tissue culture inside an incubator over an extended period of time. Biocompatible materials were used for fabrication to allow for easy sterilization and to prevent any adverse reaction from the tissue. The traction machine is based on a computer-controlled stepping motor system for easy adjustment of the deformation amplitude and frequency. The maximum stretching speed achieved is around 1 mm/s. The traction machine can measure FPCG mechanical properties and perform rupture tests to determine its ultimate strength. Several FPCGs have been successfully cultured with the machine for up to four weeks without any adverse reaction.

Biocompatible Materials↗

PubMed2006

Topographical changes of biconvex objects during equatorial traction: an analogy for accommodation of the human lens.

AIM: To assess and compare the changes in shape of encapsulated biconvex structures undergoing equatorial traction with those changes reported in the human lens during accommodation. METHODS: Equatorial traction was applied to several different biconvex structures: air, water, and gel filled mylar and rubber balloons and spherical vesicles. In the vesicles, traction was applied externally, using optical tweezers, or from within, by the assembly of encapsulated microtubules. The shape changes were recorded photographically and the change in central radius of curvature of water filled mylar balloons was quantified. RESULTS: Whenever an outward equatorial force was applied to the long axis of long oval biconvex objects, where the minor to major axis ratio was </=0.6, the central surfaces steepened and the peripheral surfaces flattened. Similar changes in the shape of the lens have been reported during human in vivo accommodation. CONCLUSIONS: All biconvex structures that have been studied demonstrate similar shape changes in response to equatorial traction. This effect is independent of capsular thickness. The consistent observation of this physical change in the configuration of biconvex structures in response to outward equatorial force suggests that this may be a universal response of biconvex structures, also applicable to the human lens undergoing accommodation.

Accommodation, Ocular↗

PubMed1999

Vitreopapillary traction in proliferative diabetic vitreoretinopathy [ssee comments].

AIM: To present the clinical profile of a new entity in advanced proliferative diabetic vitreoretinopathy (PDVR). Mechanisms of vision loss due to vitreopapillary traction on the nasal optic disc are described, followed by an introduction of methods for prevention and treatment in such cases. METHODS: 17 patients with PDVR and traction on the nasal side of the optic disc, pallor of the optic nerve head, and reduced visual acuity were included in the study. Six patients were observed retrospectively and 11 patients prospectively before and after pars plana vitrectomy. Pre- and postoperative examinations included visual acuity, Goldmann's visual field, fluorescein angiography, and measurements of visual evoked potentials (VEP). RESULTS: During a postoperative follow up period of 3 to 24.5 months (mean 14.5 months) an improvement in optic disc appearance combined with an increased visual acuity (mean increase in VA = 0.171) was observed in 15/17 (88.3%) patients. In addition, 8/17 (47%) of these patients showed higher VEP amplitudes (mean 3.83 microV), and eight (6/8 of the same patients as VEP amplitudes) patients showed a reduction of latency (mean reduction 22.25 ms) during VEP assessment. CONCLUSION: These results suggest that vitreopapillary traction may damage the anterior optic nerve, via decreased axoplasmatic flow in the optic nerve fibres and/or mechanical reduction of perfusion in the posterior ciliary arteries. The effects of each mechanism appear to be reversible, but in the long term might lead to irreversible optic nerve atrophy. Therefore, in patients with vitreopapillary traction, early vitrectomy should be considered as a method to prevent optic neuropathy.

Adult↗

PubMed2006

Branch retinal vein occlusion associated with vitreoretinal traction.

CASE REPORT: Branch retinal vein occlusion (BRVO) is believed to arise at arteriovenous crossing sites. Surgical dissection of the arteriovenous sheath has been proposed as a treatment option, yet induction of a posterior vitreous detachment may be as important in obtaining a successful surgical outcome, suggesting that vitreoretinal traction may play a role in the development of BRVO. A retrospective review of 3 patients presenting with clinical features of BRVO and evidence of vitreoretinal traction at the occlusion site was conducted. COMMENTS: All patients presented with mild vitreous hemorrhage. Intraretinal hemorrhages were distributed in an unusual linear pattern along the involved venous segment, suggesting the presence of vitreoretinal traction. Fluorescein angiography demonstrated blocked fluorescence secondary to hemorrhage with delay of venous flow at the avulsion site. Partial avulsion of the involved venous segment was evident on clinical examination, B-scan ultrasound, or optical coherence tomography. Vitreoretinal traction may contribute to the pathogenesis of BRVO in some patients.

Eye Diseases↗

PubMedDate not supplied

Optical coherence tomography and retinal thickness analyzer features of spontaneous resolution of vitreomacular traction syndrome: a case report.

PURPOSE: To report optical coherence tomography (OCT) and retinal thickness analyzer (RTA) findings in a case of spontaneous resolution of vitreomacular traction syndrome. METHODS: Qualitative and quantitative analysis of the macular region was performed with OCT and RTA. RESULTS: In the left eye of a 34-year-old woman with blurred vision, OCT and RTA examination showed a discrete linear signal anterior to the retina with attachment at the macula and secondary cystoid macular changes. OCT and RTA examination showed an increase in macular thickness (350 microm). Six months later the patient showed a spontaneous complete recovery of visual acuity. Vitreomacular traction and cystoid changes were no longer detectable at OCT and RTA examination; retinal thickness was normal (205 microm) and a posterior vitreous detachment was visible. CONCLUSIONS: Both OCT and RTA were useful tools for making the diagnosis of vitreomacular traction syndrome and demonstrating the effect of spontaneous vitreomacular traction release with resolution of cystoid macular changes.

Adult↗