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The effects of prostheses on radiotherapy treatment planning are discussed. The compositions of commonly used materials are tabulated. Sample plots show the size of perturbations produced by typical absorbers at 8 MV. A technique for estimating the density of a prosthesis in a patient is demonstrated and the effects of prostheses on representative radiotherapy plans are illustrated.
Some of the component metals of the alloys used for total joint prostheses are toxic and dissolve in the body fluids. It is important to establish how toxic these metals are and to assess the risk of localised tissue necrosis around the prostheses. This has been investigated by incubating primary monolayer cultures of human synovial fibroblasts with various preparations of metals for periods up to 18 days. Morphological changes were evident after exposure to cobalt chloride at a concentration of 50 nanomoles per millilitre and to nickel chloride at 200 nanomoles per millilitre. Chromic chloride, ammonium molybdate and ferric chloride produced no changes up to 500 nanomoles per millilitre. Cultures exposed to particulate pure metals were poisoned by cobalt and vanadium but were not affected under the same conditions by nickel, chromium, molybdenum, titanium or aluminium. Particulate cobalt and vanadium were probably toxic due to their relatively high solubility (four and one micromoles per millilitre respectively after seven days incubation). Particulate nickel also dissolved (three nanomoles per millilitre after seven days) but not in sufficient quantities to be toxic. It appears, therefore, that potentially the most harmful components are cobalt from cobalt-chromium alloy, nickel from stainless steel, and vanadium from titanium alloy. As far as can be estimated, the only combination of materials which is likely to give rise to toxic levels of metal under clinical conditions, is cobalt-chromium alloy articulating against itself to produce relatively high levels of cobalt.
Neural prostheses partially restore body functions by technical nerve excitation after trauma or neurological diseases. External devices and implants have been developed since the early 1960s for many applications. Several systems have reached nowadays clinical practice: Cochlea implants help the deaf to hear, micturition is induced by bladder stimulators in paralyzed persons and deep brain stimulation helps patients with Parkinson's disease to participate in daily life again. So far, clinical neural prostheses are fabricated with means of precision mechanics. Since microsystem technology opens the opportunity to design and develop complex systems with a high number of electrodes to interface with the nervous systems, the opportunity for selective stimulation and complex implant scenarios seems to be feasible in the near future. The potentials and limitations with regard to biomedical microdevices are introduced and discussed in this paper. Target specifications are derived from existing implants and are discussed on selected applications that has been investigated in experimental research: a micromachined implant to interface a nerve stump with a sieve electrode, cuff electrodes with integrated electronics, and an epiretinal vision prosthesis.
The purpose of this investigation was to evaluate the ability of palatal lift prostheses to stimulate the neuromuscular activity of the velopharynx. Nasendoscopic evaluations were audio-videotaped preprosthetic and postprosthetic management for 25 patients who underwent placement of a palatal lift prosthesis for velopharyngeal dysfunction (VPD). These audio-videotapes were presented in blinded fashion and random order to three speech pathologists experienced in assessment of patients with VPD. They rated the tapes on the following parameters: VP gap size, closure pattern, orifice estimate, direction and magnitude of change, and qualitative descriptions of the adequacy of VP closure during speech. VP closure for speech was unchanged in 69% of patients and the number of patients rated as improved or deteriorated was nearly identical at about 15%. Postintervention gap shape remained unchanged in 70% of patients. The extent of VP orifice closure during speech remained unchanged in 57% of patients. Articulations that could impair VP function improved in 30% of patients, deteriorating in only 4%. Results of this study neither support the concept that palatal lift prostheses alter the neuromuscular patterning of the velopharynx, nor provide objective documentation of the feasibility of prosthetic reduction for weaning.
Photoelectric dyes absorb light and convert photon energy to electric potentials. To test whether these dyes could be used for retinal prostheses, a simple in vitro screening system was developed. Retinal neurons were cultured from the eyes of chick embryos at the 10-day embryonic stage, at which time no retinal photoreceptor cells have yet developed. Intracellular calcium elevation was observed with Fluo-4 in cultured retinal neurons before and after photoelectric dye was applied at varying concentrations to the culture medium. Five of 7 photoelectric dyes tested in this in vitro system induced intracellular calcium elevation in cultured chick retinal neurons. The intracellular calcium elevation generated by the 5 photoelectric dyes was blocked by extracellular calcium depletion in the case of all 5 dyes, and, except for one dye, by the presence of voltage-gated calcium channel blockers. The photoelectric dyes absorbed light under an inverted microscope and stimulated retinal neurons. This simple in vitro system allows the screening of photoelectric dyes which can be used for retinal prostheses.
In an experimental study, the mechanical behaviour of the ossicle-chain during changes of the static air pressure was analyzed microscopically and with a radiographic magnification technique in temporal bone preparations. Several preliminary experiments served to pinpoint methodological problems, like exsiccation-artifacts, storage procedures, preparation defects, missing air-cushion effect with the opened middle-ear cavity, absent labyrinthine pressure, relation of the optical axis to middle-ear structures and statistical reproducibility of the measured values. Variations of the static air pressure in the external ear canal ranging from 0 to +/- 400 mmH2O induce an inward-outward movement of the malleus. In the regular middle-ear, the direction of this movement is changed within the ossicular chain into a predominantly upward-downward direction of the lenticular process, due to a gliding function of the incudo-malleal (IM) joint. This results in a gliding movement of the surfaces of the incudostapedial joint (IS). In this way, the stapes and the inner-ear are decoupled from the excessive displacements of the drum membrane and malleus. This change in the mode of motion explains many former results of ossicle vibration, aroused by unphysiologically high sound pressures, like v. Békésy's description of the tilting footplate. This mode of motion, however, changes completely if the gliding function of the IM-joint is cancelled by experimental ankylosis. In that case, the predominant direction of movement at the incus and stapes is inward and outward, too. This mode of motion has been the generally accepted concept of the ossicle-chain mechanics up to now. This isodirectional motion also occurs with progressive exsiccation of the temporal bone preparations, explicable with drying and shrinking of the capsular ligament of the IM-joint. It is conceivable, therefore, that our concepts of the mechanics of the ossicle-chain were partly based on experiments with insufficiently moistened temporal bone preparations, as the methodological problem of the exsiccation became known only during recent decades. In further experiments with static air pressure, the mechanics of the reconstructed ossicle-chain, i.e. tympanoplasty and stapedial prostheses, were studied. In the columella-like chain reconstruction, the displacement of the stapes equals the values measured with the ankylosed IM-joint. This displacement is limited by the strength of the annular ligament, whose function, however, is eliminated in the case of stapedial prostheses. Now the displacement is limited by the friction of the piston at the perforation in the footplate.(ABSTRACT TRUNCATED AT 400 WORDS)
Implanted silicone breast prostheses leak silicone gel through the intact membrane. In order to determine the exact location and to achieve a semiquantitative estimation of the amount of silicone in the surrounding tissue, a method involving scanning electron microscopy (SEM) and energy dispersive analysis of X-rays (EDAX) was used. By this method we were able to demonstrate the presence of the element silicon (Si) (main component of silicone, a polymer with a general formula e.g. (CH3[Si(CH3)2O]n Si(CH3)3 along the inner border of vacuoles corresponding to the light microscopic localization of droplets and in macrophages. The tissue adjacent to the prostheses had a higher silicon content than the control tissue.
In most developing countries, the physically handicapped often have rehabilitation setbacks such as unavailability of modern rehabilitative aids which may result in non-achievement of the desired goals in activities of daily living. Children with poliomyelitis, hemiplegics, amputees and paraplegics top the list of patients requiring rehabilitation at University College Hospital, Ibadan. The amputees depend on wooden peg legs or pylons made by the occupational therapy department since modular and P.T.B. prostheses are presently not available in this hospital. Physiotherapists, therefore, encounter problems in teaching correct patterns of walking and other functional activities to the above-knee amputee because knee joints are absent. Rural amputee farmers use pylons as they can wade through water and mud with them. Calipers, toe raising devices, knee cages and spinal supports are required by 75% of the 300 children with poliomyelitis and some of the paraplegics receiving physiotherapy in this hospital. Due to lack of imported parts, materials and experienced personnel, it has not been possible to meet the required demands. The occupational therapy department, as well as indigenous shoe markers and iron welders, rescue the situation as much as possible. Similarly, cervical collars are made from PVC buckets. It is therefore necessary that research on the use of local materials for prostheses and orthoses be carried out. Difficulties encountered with imported parts and materials will be removed to the advantage of patients.
Women who have had a mastectomy for breast cancer have to cope with two major problems: first, that they have cancer, and second, that they have lost their physical appearance. The provision of an appropriate prosthesis can reduce the sense of disfigurement. If women were to obtain the full psychological benefit of wearing a breast prosthesis, they need to be informed about the available breast forms, have an opportunity to choose between them, and to be satisfied with their choice. In this study of 49 women, only 44% had had the opportunity to choose a prosthesis, 28% were dissatisfied with their prostheses, and 17% were still using temporary prostheses.
The number of partial-foot amputations performed is increasing, and many recommendations have been made regarding the use of prostheses and footwear designed to prevent higher-level amputations in this population. The present study investigated the use of prostheses and shoe inserts and the types of footwear worn by partial-foot amputees in the inner city to determine whether previous recommendations are being followed as well as whether new prosthetic styles are being used. The study surveyed 110 patients (73 men and 37 women) with a mean age of 58.6 years (range, 21 to 86 years) with partial-foot amputations of all levels. The results showed that about one-half of all patients wore a shoe-insert orthosis. Although 54% wore some form of special footwear to accommodate and protect the residual foot, no patient in this study wore a shoe with a rocker-bottom sole. Only one patient with a transmetatarsal amputation used a brace and only one patient in the entire study wore a modern cosmetic foot prosthesis.
PURPOSE: An analysis of retrospective data was conducted to establish the survival rates of osseointegrated implants used to retain orbital, nasal, and auricular prostheses over a 14-year period and to recommend guidelines in the restorative treatment of such facial defects. MATERIALS AND METHODS: Included in this study were all patients who received implant-retained prostheses for auricular, nasal, or orbital defects from 1987 to 2001 in the Maxillofacial Clinics at the UCLA and City of Hope Medical Centers. Data were obtained from patient charts. Two methods were used to determine survival rates: (1) the percentage of the total exposed implants that survived was determined, and (2) life table analysis was used to calculate cumulative survival rates at different time intervals. RESULTS: A total of 207 implants were placed in 72 patients, and 182 implants had been uncovered. During the study period, 35 implants failed to integrate, and the survival rate for all exposed implants was 80%. Auricular implants showed the highest survival rate (95%), and orbital implants showed the lowest survival rate (53%). The life table analysis demonstrated a cumulative 6-year survival rate of 92% for auricular implants and 87% for piriform/nasal implants. In contrast, the survival rate for orbital implants showed a steady downward trend and reached 59% at 66 months. CONCLUSION: It is possible to achieve high survival rates of implants in the auricular and piriform/nasal sites through careful presurgical and radiographic planning. The less favorable long-term survival of implants in the orbital rim, especially at irradiated sites, requires further study.
Currently available data demonstrate the need for balance prostheses. Recent technological and biomedical advances now make it feasible to produce miniaturized sensors, signal processors, electric stimulators, and stimulating electrodes that are roughly analogous to a cochlear implant but which provide information about self motion, instead of sound. Many areas require work before balance prostheses become a reality. Some of these include: the development of a motion sensor array, the conversion of the sensed motion into physiologically meaningful information, the delivery of the transformed information to the CNS, the training of vestibular deficient individuals to use the prosthesis, and developing methods to evaluate the efficacy of the device. In this "white paper", we consider these issues in the context of prototype baseline prosthetic devices.
PURPOSE: This article presents a novel manufacturing approach that integrates laser surface digitizing/scanning and computer-aided design (CAD) and manufacturing (CAM) to achieve automated fabrication of spatially and anatomically accurate extraoral facial prostheses. MATERIALS AND METHODS: Topologic data of the patient's face, including the site of deformity and the anatomy of a healthy "donor" organ, were acquired using laser surface digitizing. Two different CAD data manipulation techniques were developed to alleviate problems encountered in laser-digitized data sets. To reduce patient involvement, fitting of the prosthesis was conducted using a computer model of the patient's face. Once finalized, rapid prototyping techniques were employed to fabricate a master pattern to cast the final prosthesis. RESULTS: Three case studies involving different facial prostheses were conducted to evaluate the integrated manufacturing system. The results demonstrated the many advantages of the system for facial prosthesis production. CONCLUSION: With the new manufacturing approach, reduced patient discomfort, minimal dependence on the artistic skills of the prosthetist, and short turnaround times for prosthesis production can be expected.
PURPOSE: The purpose of this report is to describe a new technique for fabricating auricular prostheses by a computer-aided design/manufacturing (CAD/CAM) system. MATERIALS AND METHODS: A spiral CT was performed on a patient who had a right ear defect resulting from an accident. A 3-D image was reconstructed with the CT data. Through image ware, the image of the normal ear was extracted, mirrored, and Boolean operated with the image of the deformed side of the face. It was well modified and smoothed in the FreeForm model system so that it could precisely adapt to the deficient side of the face. A paper model ear was manufactured by rapid prototyping from the digitized data. Finally, silicone was poured into a silicone mold from the paper ear to create a silicone auricular prosthesis. RESULTS: The dimension, shape, and anatomic contour of the auricular prosthesis were quite similar to those of the normal ear and precisely matched the deformed area. CONCLUSION: The CAD/CAM system for creating auricular prostheses appears to be a practical technique.
This chapter further affirms the safety and efficacy of hemi and total temporomandibular joint (TMJ) reconstruction with the Christensen TMJ Prostheses (TMJ Implants, Inc., Golden, CO, USA). Hemi and total TMJ reconstruction with the Christensen TMJ prostheses was first introduced by Robert W. Christensen, DDS in 1961 and 1965, respectively, and is gaining widespread acceptance as a viable alternative in the treatment of temporomandibular joint disorders (TMD). The Christensen TMJ devices have been used to treat various disorders in large numbers of patients, and the pertinent results of 10 years of study are reported in this chapter.
Malignant gastroduodenal obstruction may cause significant morbidity. Insertion of enteral prostheses as a palliative treatment is an acceptable option to achieve an appropriate gastric voiding without the morbidity associated to palliative surgery, with a lesser procedure-related mortality and a lower cost, while providing a better quality of life. Its is important to unify and consolidate the endoscopic procedure for the placement of enteral prostheses, avoiding variations that may preclude an adequate analysis of this procedure outcome.
A woman with mammary prostheses developed hyperprolactinemia and galactorrhea. The condition was unresponsive to treatment with bromocriptine and abated only with removal of the prostheses.
A description is given of the different types of grafts: venous, arterial, skin and conjunctiva, as well as prostheses of plastic material, polyvinyl, silicon, used in the reparatory and reconstructive surgery of the lacrimal ducts. The author gives the indications, advantages and drawbacks of these grafts and prostheses and emphasizes the importance of prosthesis with polyvinyl probes in the reconstructive surgery of the lacrimal ducts over other methods.