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At least 631 records · Page 35Linked to original sources
PubMed1998

[Radiation protection in the use of tracers in radioguided breast surgery].

PURPOSE: Recent techniques in nuclear medicine have permitted to implement new procedures useful in surgery. Among these, the procedures for locating sentinel lymph nodes and nonpalpable breast lesions are of great interest. The protocols for the location of the sentinel lymph node and for the radioguided location of occult lesions developed at the European Institute of Oncology (IEO, Milan) are based on the administration of radiopharmaceuticals labelled with Technetium-99m (99mTc). We evaluated the dosimetric data relative to patients and hospital personnel to assess whether specific radiation protection procedures are needed. MATERIAL AND METHODS: Fifty patients with nonpalpable breast lesions and 50 patients with suspected lymph node involvement were enrolled in this study. All the patients underwent surgery the day after in-loco administration of the radiopharmaceutical (11 MBq of 99mTc). The absorbed dose to the hospital personnel was estimated from the air kerma rate measured by ionization chamber at different distances from the patients at 0 and 16 hours after the radiopharmaceutical administration. In order to evaluate radiation protection for patients, absorbed doses were measured positioning thermoluminescent dosimeters on the patient's skin for about 16 hours. In the operating room, activity was measured on some excised tissues (lymph nodes and tumors) and on surgical instruments. RESULTS: Absorbed doses were very low for the clinical staff also in case of prolonged patient assistance. After 100 cases, the surgeon mean absorbed dose to the hands and mean effective dose were .45 mGy and .09 mGy, respectively. These values correspond to 1% of the annual dose limit to the hands and to 10% of the annual equivalent effective dose recommended for the population (ICRP 60 and law by decree 230/95). The absorbed dose to healthy tissues of the patients were lower than 1 mGy (mean values: contralateral breast: .9 mGy; abdomen .45 mGy). The mean activity detected in the excised tissues was 9 kBq and 900 kBq in the sentinel lymph nodes and in the tumor lesions (injection site), respectively. The activity detected on the surgical instruments, higher on gauzes (< 100 kBq), was negligible. CONCLUSIONS: From the radiation protection point of view, the data support the validity of our protocols. Absorbed doses to the hospital personnel are low and require neither a radiation protection control nor a classification of exposed workers as classes A or B. Special containers for radioactive wastes are necessary in the administration room but not in the operating room, where the levels of possible contamination are negligible.

Breast Neoplasms↗
PubMed2002

Quantitative analysis of factors affecting intraoperative precision and stability of optoelectronic and electromagnetic tracking systems.

This study aims to provide a quantitative analysis of the factors affecting the actual precision and stability of optoelectronic and electromagnetic tracking systems in computer-aided surgery under real clinical/intraoperative conditions. A "phantom-skull" with five precisely determined reference distances between marker spheres is used for all measurements. Three optoelectronic and one electromagnetic tracking systems are included in this study. The experimental design is divided into three parts: (1) evaluation of serial- and multislice-CT (computed tomography) images of the phantom-skull for the precision of distance measurements by means of navigation software without a digitizer, (2) digitizer measurements under realistic intraoperative conditions with the factors OR-lamp (radiating into the field of view of the digitizer) or/and "handling with ferromagnetic surgical instruments" (in the field of view of the digitizer) and (3) "point-measurements" to analyze the influence of changes in the angle of inclination of the stylus axis. Deviations between reference distances and measured values are statistically investigated by means of analysis of variance. Computerized measurements of distances based on serial-CT data were more precise than based on multislice-CT data. All tracking systems included in this study proved to be considerably less precise under realistic OR conditions when compared to the technical specifications in the manuals of the systems. Changes in the angle of inclination of the stylus axis resulted in deviations of up to 3.40 mm (mean deviations for all systems ranging from 0.49 to 1.42 mm, variances ranging from 0.09 to 1.44 mm), indicating a strong need for improvements of stylus design. The electromagnetic tracking system investigated in this study was not significantly affected by small ferromagnetic surgical instruments.

Biophysical Phenomena↗
PubMed2001

Transmission of scrapie by steel-surface-bound prions.

BACKGROUND: Prions are unusually resistant to conventional disinfection procedures. An electrode used intracerebrally on a Creutzfeldt-Jakob disease (CJD) patient transmitted the disease to two patients in succession and finally to a chimpanzee, despite attempted disinfection. Concerns that surgical instruments may transmit variant CJD have been raised by the finding of PrP(Sc), a surrogate marker for infectivity, in various tissues other than brain. MATERIALS AND METHODS: Stainless steel wire was exposed to scrapie-infected brain or brain homogenate, washed exhaustively and inserted into the brain of indicator mice to measure infectivity. RESULTS: A contact time of 5 min with scrapie-infected mouse brain suffices to render steel wire highly infectious and insertion of infectious wire into the brain of an indicator mouse for 30 min suffices to cause disease. Infectivity bound to wires persists far longer in the brain than when injected as homogenate, which can explain the extraordinary efficiency of wire-mediated infection. No detectable amounts of PrP could be eluted with NaOH, however the presence of PrP on infectious wires was demonstrated by chemiluminescence. Several recommended sterilisation procedures inactivated wire-bound mouse prions, but exposure to 10% formaldehyde was insufficient. CONCLUSIONS: Prions are readily and tightly bound to stainless steel surfaces and can transmit scrapie to recipient mice after short exposure times. This system mimics contaminated surgical instruments and will allow an assessment of sterilisation procedures.

Animals↗
PubMed1980

Esophagogastrectomy using the auto suture EEA surgical stapling instrument.

A stapling instrument, which creates end-to-end inverting anastomoses, is described for esophagogastrostomy. The inverted anastomosis is held together by a double staggered row of stainless-steel wire staples. Experience with 7 consecutive patients who underwent esophagogastrectomy for carcinoma of the distal esophagus or proximal stomach using this device is reported. Postoperative complications included atelectasis in 1 patient, cardiac failure in 1, and pneumonia in 1. A fibrotic stricture developed at the anastomotic site 5 months postoperatively in 1 patient. There were no anastomotic leaks. The stapled anastomosis takes 2 to 3 minutes to perform and seems to be at least comparable to handsewn anastomoses.

Adenocarcinoma↗
PubMed1995

[Current advances and future direction of arthroscopic surgery for disorders in the knee joint].

An aim of this paper is to report current advances and future direction of arthroscopic surgery for disorders in the knee joint. Recently, advances of operative techniques and improvement of surgical instruments allow almost all disorders in the knee joint cavity to be arthroscopically treated. Patients of the age greater than 3 years can undergo this surgery. Arthroscopic surgery involves release of synovial malformation, capsular strung, and postoperative adhesion, removal of free bodies, excision of benign tumors, partial synovectomy, multiple drilling or pinning of osteochondral lesions, partial or total meniscectomy, plastic resection of bony spurs, repair of the torn menisci and ligaments, reconstruction of ligaments and menisci, and etc. Arthroscopic surgery has many advantages compared with open surgery: First, more precise operation can be performed in arthroscopic surgery, resulting in better final outcome, because this surgery gives rather wider visual field for intraarticular operation. Secondly, arthroscopic surgery is less invasive. Therefore, patients have less postoperative pain and adhesion, quickly regain the normal range of knee motion, and early return to the normal activities. Thirdly, operation scar after arthroscopic surgery is more acceptable for patients from the cosmetic viewpoint. There are few disadvantages in arthroscopic surgery if well-trained surgeons carefully operate patients according to the correct indications of this surgery. In the near future, arthroscopic surgery will be more frequently and wide-spread performed in Japan. Therefore, instructional and training systems for arthroscopic surgeons should be established as soon as possible. Improvement of the hardware involving arthroscopes and surgical instruments may be one of keys for future advances of arthroscopic surgery.(ABSTRACT TRUNCATED AT 250 WORDS)

Arthroscopy↗
PubMed2004

Patient-specific mechanical properties of a flexible multi-body model of the scoliotic spine.

The flexibility of the scoliotic spine is an important biomechanical parameter to take into account in the planning of surgical instrumentation. The objective of the paper was to develop a method to characterise in vivo the mechanical properties of the scoliotic spine using a flexible multi-body model. Vertebrae were represented as rigid bodies, and intervertebral elements were defined at every level using a spherical joint and three torsion springs. The initial mechanical properties of motion segments were defined from in vitro experimental data reported in the literature. They were adjusted using an optimisation algorithm to reduce the discrepancy between the simulated and the measured Ferguson angles in lateral bending of three spine segments (major or compensatory left thoracic, right thoracic and left lumbar scoliosis curves). The flexural rigidity of the spine segments was defined in three categories (flexible, nominal, rigid) according to the estimated mechanical factors (alpha). This approach was applied with ten scoliotic patients undergoing spinal correction. Personalisation of the model resulted in an increase of the initial flexural rigidity for seven of the ten lumbar segments (1.38 < or = alpha < or = 10.0) and four of the ten right thoracic segments (1.74 < or = alpha < or = 5.18). The adjustment of the mechanical parameters based on the lateral bending tests improved the model's ability to predict the spine shape change described by the Ferguson angles by up to 50%. The largest differences after personalisation were for the left lumbar segments in left bending (4 degrees +/- 3 degrees). The in vivo identification of the mechanical properties of the scoliotic spine will improve the ability of biomechanical models adequately to predict the surgical correction, which should help clinicians in the planning of surgical instrumentation manoeuvres.

Algorithms↗
PubMed2003

Biomechanical modeling of posterior instrumentation of the scoliotic spine.

Scoliosis is a three-dimensional deformation of the spine that can be treated by vertebral fusion using surgical instrumentation. However, the optimal configuration of instrumentation remains controversial. Simulating the surgical maneuvers with personalized biomechanical models may provide an analytical tool to determine instrumentation configuration during the pre-operative planning. Finite element models used in surgical simulations display convergence difficulties as a result of discontinuities and stiffness differences between elements. A kinetic model using flexible mechanisms has been developed to address this problem, and this study presents its use in the simulation of Cotrel-Dubousset Horizon surgical maneuvers. The model of the spine is composed of rigid bodies corresponding to the thoracic and lumbar vertebrae, and flexible elements representing the intervertebral structures. The model was personalized to the geometry of three scoliotic patients (with a thoracic Cobb angle of 45 degrees, 49 degrees and 39 degrees ). Binary joints and kinematic constraints were used to represent the rod-implant-vertebra joints. The correction procedure was simulated using three steps: (1) Translation of hooks and screws on the first rod; (2) 90 degrees rod rotation; (3) Hooks and screws look-up on the rod. After the simulation, slight differences of 0-6 degrees were found for the thoracic spine scoliosis and the kyphosis, and of 1-8 degrees for the axial rotation of the apical vertebra and for the orientation of the plane of maximum deformity, compared to the real post-operative shape of the patient. Reaction loads at the vertebra-implant link were mostly below 1000 N, while reaction loads at the boundary conditions (representing the overall action of the surgeon) were in the range 7-470 N and maximum torque applied to the rod was 1.8 Nm. This kinetic modeling approach using flexible mechanisms provided a realistic representation of the surgical maneuvers. It may offer a tool to predict spinal geometry correction and assist in the pre-operative planning of surgical instrumentation of the scoliotic spine.

Adolescent↗
PubMed1995

Real-time interactions in MRI.

With the advent of magnetic resonance fluoroscopic imaging, it is possible to obtain images at a rate which can be considered effectively real-time. Image refresh rates can be as low as 0.5 s. Such rates are fast enough to allow MR to be used for guidance of surgical instruments during micro-surgical procedures. Examples include the localization of biopsy needles within a tumor, localization of surgical tools for application of therapeutic drugs or the proper positioning of optical fibers for application of laser heat. It may also be used for long duration monitoring of a patient in an attempt to diagnose rare and short duration clinical events.

Biopsy↗
PubMed1993

Three-dimensional simulation of Harrington distraction instrumentation for surgical correction of scoliosis.

Harrington distraction rod surgery on six female patients with idiopathic scoliosis was simulated in three-dimensional osseoligamentous finite element models with individual geometry taken from preoperative stereo roentgenographic reconstructions of the spine and ribcage and compared with the measured outcome. Boundary conditions at the ends of the spine were used to maintain pelvis and head alignment. Published material and flexibility properties were used. The amount of hook distraction was calculated from measured changes in the distance between the hook sites (range, 13-27 mm). Initial simulations underestimated the Cobb angle correction by an average 6%. They underestimated the spinal elongation by 36% and predicted an average 12 degrees increase in kyphosis angle compared with an actual 10 degrees average decrease. Agreement for sagittal plane changes improved in five cases when the beams representing the motion segments were displaced posteriorly. In the sixth case (with the rod applied over a lordotic spinal region), agreement was improved with the motion segment beams displaced anteriorly. The amount of the beam displacement that gave the best agreement was variable, and we were not able to predict it for each individual. Both measured and simulated changes in vertebral transverse plane rotations and in rib angulations were small. The greatest source of errors in these simulations appeared to be inadequate representation of in vivo motion segment behavior by in vitro measured stiffness properties.

Adolescent↗
PubMed2005

Sternal split approach to the cervicothoracic junction in children.

STUDY DESIGN: We present a descriptive case series outlining the surgical technique and outcome in six patients managed with a combined anterior neck and sternal splitting approach. OBJECTIVES: To describe a surgical approach used in the management of severe cervicothoracic kyphosis and/or scoliosis in pediatric patients. SUMMARY OF BACKGROUND DATA: There are few reports in the literature that address the problem of accessing multileveled spinal deformities around the cervicothoracic junction requiring stabilization in the pediatric population. METHODS: A detailed chart and radiographic review was completed of six consecutive patients managed at our center with a combined anterior neck and sternal splitting approach. The indications, surgical technique, and outcome are reviewed for each case. This technique was employed in 6 pediatric patients, aged 3-15 years, at the authors' institution. Diagnoses included Klippel-Feil Syndrome (2 patients), Proteus Syndrome, Larsen Syndrome, and neurofibromatosis type I (2 patients). All patients had severe cervicothoracic kyphosis requiring surgical instrumentation. This technique allowed surgical access from C5-T6. RESULTS: This approach was invaluable in gaining access to the cervicothoracic junction to address complex spinal deformities in pediatric patients. In one patient, a separate thoracotomy was performed to access the lower thoracic spine. The only significant complication related to the approach was recurrent laryngeal nerve palsy experienced by one patient. This approach allowed stabilization of severe scoliotic and/or kyphotic deformities to impede curve progression. CONCLUSIONS: This approach was invaluable in gaining multileveled access to the cervicothoracic junction to address complex spinal deformities in pediatric patients.

Adolescent↗
PubMed1997

Evaluation with evoked and spontaneous electromyography during lumbar instrumentation: a prospective study.

The neuroanatomical structures that approximate the bony pedicles of the lumbar spine allow little room for technical error or compromise of the bone during pedicle screw insertion. Currently available neurophysiological monitoring techniques detect compromised bone and nerve root injury after it occurs. The purpose of this prospective study is to evaluate the reliability and efficacy of a unique neurophysiological monitoring technique. This technique provides immediate evaluation of pedicle cortical bone integrity in patients undergoing lumbar fusion with instrumentation by using electrified surgical instruments throughout the pedicle screw fusion procedure. Spontaneous electromyographic (EMG) activity was also monitored. Intraoperative evoked EMG stimulation was performed using a pedicle probe and feeler as monopolar stimulators during the insertion of 164 pedicle bone screws in 32 patients. The EMG response to subthreshold stimulation intensities indicated cortical bone compromise. Immediate and conclusive feedback via evoked EMG activity using stimulating pedicle probes in appropriate muscle groups was successful in identifying pedicle cortical bone compromise in four patients. One false-negative evoked EMG study was noted but was identified via spontaneous EMG activity. Intraoperative EMG monitoring alerted the surgeon that redirection of the pedicle probe or screw was necessary to avoid nerve root irritation or injury and served as an early warning system. Evoked EMG stimulation proved to be reliable and efficacious, especially when used in combination with spontaneous EMG. This technique may provide an added safeguard during implant placement procedures at centers where intraoperative neurophysiological monitoring is routinely performed.

Adult↗