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Bilateral fitting of BAHAs and BAHA fitted in unilateral deaf persons: acoustical aspects.

The benefit of a bone-anchored hearing aid (BAHA) to a patient fitted bilaterally; and the benefit of a BAHA to a unilaterally deaf person was estimated by four acoustical measurements: directional sensitivity of a BAHA placed at the skull, vibration transmission in the skull, gain, and estimated transcranial attenuation of bone conducted sound. Provided a patient has a similar bone conduction hearing ability at both cochlea, it was found that a patient should, theoretically, benefit from bilateral fitting of BAHAs in terms of better hearing thresholds from the front, and better overall hearing ability from the surround. The data indicates further, that bilateral fitting facilitates extraction of interaural cues, which should lead to greater ability to determine the direction of a sound source, as well as better hearing in noise. However, due to the cross-hearing of bone conducted sound, the binaural processing for the patient fitted bilaterally with BAHAs is less than for normal binaural air conduction hearing. Finally, the data showed that the benefit of fitting a BAHA in a unilaterally deaf person, depends on that person's transcranial attenuation.

Acoustic Stimulation↗

Paired-comparison hearing aid preferences: evaluation of an unforced-choice paradigm.

Fifteen normal-hearing listeners compared nine frequency-response slopes in a round-robin paired-comparison tournament as they listened to passages of connected discourse against a competing noise background at a +3-dB signal-to-noise ratio. All participants listened in an AB paradigm, in which they were forced to choose which of two signals (A or B) produced better speech intelligibility, and an ABN paradigm, in which they were allowed a third choice of No Preference (N). For both paradigms, listeners generally preferred frequency shaping that either cut low frequencies or boosted high frequencies, and intra- and intersession reliability was high overall. Although listeners' most-preferred responses tended to converge on the same frequency-response slope in the two paradigms, the reliability of these responses was significantly higher for ABN than for AB. The use of the ABN paired-comparison paradigm deserves further study, therefore, as a method to fit multimemory hearing aids.

Adult↗

Validation of a quantitative method for defining CAD/CAM socket modifications.

A quantitative method was developed for defining manual socket modifications, averaging these modifications over a series of amputees, and using the average modifications as a template in commercial CAD/CAM systems. The CADVIEW programme (i.e. software for viewing and analysing CAD sockets) was rewritten to provide comparison functions for aligning sockets to a common axis, visualising the differences between sockets, generating modification outlines, assigning apex point values, and averaging the modification outlines. A CAD template generated in this manner should be the best general representation of a prosthetist's modification style. To test this hypothesis, 13 people with trans-tibial amputations were fitted with both a manual and a CAD/CAM socket. Questionnaires were completed by the subjects and by the prosthetist to obtain information on prosthetic comfort, function, and overall satisfaction. Ground reaction force and stride parameter data were also collected for each prosthesis during gait laboratory testing. No significant differences were found between the manually designed socket and the CAD/CAM designed socket for all data except the vertical peak forces on the amputated side. These results support the clinical application of this quantitative technique for making the transition from manual to CAD/CAM prosthetic modification procedures.

Adult↗

The use of casting investments for soldering gold implant bars: a pilot study.

The use of gypsum- and phosphate-bonded casting investments for soldering gold implant bars was investigated. Eighteen gold implant bars were sectioned and divided into two groups of nine specimens each. One group of bars was invested with gypsum-bonded investment and the other group invested with phosphate-bonded investment. The accuracy of fit of each group was measured at the gold cylinder-abutment interface in microns using a stereomicroscope. The use of gypsum-bonded investment resulted in a more accurate fit as compared with phosphate-bonded investment.

Analysis of Variance↗

The case against rigid contact lenses.

Rigid lens fitting has been an integral part of contact lens practice for decades. However, rigid lens fitting has been constantly declining since soft lenses were introduced in the 1970s to whereby, world wide, rigid lenses constitute less than 10% of new contact lens fits. It seems that many practitioners correctly or incorrectly believe that rigid lenses only need to be prescribed in specialized or extenuating circumstances. This discussion article examines the international decline in rigid lens fitting and seeks to explain the cause of this trend. I conclude that rigid lenses will be virtually obsolete by the year 2010.

Contact Lenses↗

Morphological changes during early trans-tibial prosthetic fitting.

Morphological changes in the amputation stump may have serious implications regarding the suspension and fit of the prosthetic socket. In an earlier study (Lilja and Oberg, 1997) the authors have shown that the volume of the trans-tibial amputation stump decreases according to a negative power function after amputation, and that the stump volume does not stabilise until four months after the operation. In the present study, Magnetic Resonance Imaging (MRI) technique was used to examine morphological changes in the amputation stump after trans-tibial amputation in a small number of cases. The authors expected to find a decrease in the cross-sectional area of the stump and of the separate muscles similar to the findings in earlier studies. However, two different patterns were found. The cross-sectional area of the entire stump as well as that of the medial muscle group changed according to the authors' hypothesis, i.e. an initial fast decrease, followed by a more moderate decrease of the area. In the lateral muscle group another pattern was found. After an initial rapid decrease the area increased, sometimes to a magnitude larger than the initial value. After the amputation the lateral muscle group may acquire a new function, contributing to the suspension of the socket. Despite the limited number of patients, this study presents findings which may be important in the clinical fitting of trans-tibial prostheses.

Aged↗

Check records--a chairside mounting procedure.

This article considers the logistical problems involved when the check (interocclusal) record procedure is used to remount complete dentures on an articulator. It reports the development of upper and lower "check record mounting blocks" that may be made to fit any articulator, thus enabling the procedure to be performed easily and quickly at chairside.

Dental Articulators↗

Computerized videokeratoscopy contact lens software for RGP fitting in a bilateral postkeratoplasty patient: a clinical case report.

Computerized videokeratoscopy systems now allow interactive rigid gas permeable (RGP) fitting evaluation using fluorescein pattern simulations through updated software programs. We used Computed Anatomy's Topographic Modeling System-1 (TMS-1) Custom Design Contact Lens Program successfully to refit a symptomatic bilateral post-penetrating keratoplasty patient. No trial lenses were used. For each eye the base curve, optic zone size, and edge lift were chosen from the optimal fluorescein pattern designed and titrated on the TMS-1 unit. Lens powers were based on the patient's previous lenses and overrefraction. Dispensed lenses provided a clinically acceptable fit, good comfort, and maximal visual acuity, and no adjustments were necessary. Corneal videokeratoscopy can be successfully employed to titrate an RGP fit, even on irregular corneas.

Astigmatism↗

Contact lens fitting over intrastromal corneal rings in a keratoconic patient.

BACKGROUND: Intrastromal corneal ring segments have been used as a refractive surgery method for treatment of myopia. More recently, attempts have been made to use this surgical procedure in patients with keratoconus. CASE REPORT: A 51-year-old man with keratoconus came to the clinic for a contact lens refit. He had undergone surgical insertion of intrastromal corneal rings in his right eye 7 months earlier in an attempt to obtain acceptable vision without contact lenses. At the time of presentation, the patient was not satisfied with his vision in the right eye and requested an attempt to improve his vision with a contact lens. The resulting corneal shape after surgery presented some complications, but the patient was able to achieve 20/25-vision and adequate comfort in his right eye with a piggyback contact lens system. CONCLUSIONS: Insertion of intrastromal corneal rings may be beneficial in patients with early keratoconus or who are contact lens-intolerant. However, patients with more-advanced keratoconus are not likely to achieve adequate vision after the surgery and will require a contact lens. In addition, changes in the corneal anatomy created by the intrastromal rings may make contact lens fitting more challenging. The corneal irregularity may be exacerbated due to drastic variations in corneal elevation over the intrastromal ring and directly adjacent to the ring. This irregularity in elevation leads to difficulty in centering the lens on the eye and problems with bubbles forming under the contact lens over areas of corneal depression. When successfully fitted, contact lenses over intrastromal corneal rings can improve vision significantly.

Contact Lenses↗

An in vivo quantitative analysis of the fit of Nobel Biocare implant superstructures.

Loss of osseointegration of implant fixtures and mechanical failure of superstructures have been attributed to failure to achieve a passive fit between the superstructure and the transmucosal abutment (TMA). The fit of five mandibular superstructures, fabricated on Nobel Biocare implants, was investigated in vivo, using a polyvinyl siloxane impression material to record the discrepancies. Following sectioning of the impressions, the vertical and horizontal discrepancies were analysed at four locations using a travelling microscope. The discrepancies obtained were measured both when the gold cylinder screws were maximally tightened by hand and when tightened with a torque driver to the recommended value of 10 Ncm. The vertical discrepancies for the hand tightened abutments ranged from 0 micron to 63 microns with a mean of 14 microns. In the mechanically tightened group, the vertical discrepancies ranged from 0 micron to 130 microns with a mean of 21 microns. The horizontal discrepancies for the mechanically tightened abutments ranged from 0 micron to 140 microns with a mean of 31 microns, compared with a mean of 46 microns and range of 0 micron to 113 microns, for the hand-tightened abutments. A close fit was seldom achieved. It is concluded that considerable discrepancies existed around superstructures that had been judged to have a clinically acceptable fit. These were reduced in the vertical direction by hand tightening of the gold screws.

Dental Abutments↗

[Biomechanics and evaluation of the microprocessor-controlled C-Leg exoprosthesis knee joint].

QUESTION: Also in the field of technical orthopedics, electronics and computer technology are being is used more and more often. This paper describes a microprocessor-controlled prosthetic knee joint with swing phase control and stance phase stability, the so-called C-Leg. The function of this electronic knee joint is explained. Prosthetic treatment using the C-Leg is compared with traditional prosthetic knee joints. METHOD: 15 patients using the C-Leg have been observed over periods of 6 to 14 months. The treating prosthetists have given an assessment regarding the function and the improvements in comparison with the previously fitted knee joints. The patients, too, were asked to compare function and comfort of the new prosthetic fitting with the previous one. RESULTS: Both, prosthetists and patients marked this new type of microprocessor-controlled knee joint in nearly all points with "very good" and described a clear improvement to the previous, purely mechanical prosthetic fitting. CONCLUSIONS: Obviously, this new technology seems to be a milestone in prosthetic knee joint fitting, in order to clearly improve the prosthetic fitting of transfemoral amputees and thus their quality of life, especially of people who have several disabilities.

Adult↗

Comparison of three procedures for initial fitting of compression hearing aids. II. Experienced users, fitted unilaterally.

This paper is the second in a series comparing three procedures for the initial fitting of multichannel compression hearing aids. The first paper reported the results for a group of 10 experienced hearing aid users fitted bilaterally. This paper reports the results for a different group of 10 experienced hearing aid users fitted unilaterally. The three procedures were: (1) CAMEQ, which aims to amplify speech so as to give equal loudness per critical band over the frequency range 500-5000 Hz, and to give similar overall loudness to normal over a wide range of speech levels; (2) CAMREST, which aims to amplify speech so as to restore normal specific loudness patterns, over a wide range of speech levels; and (3) DSL [i/o], which aims to map the dynamic range of normal-hearing people into the reduced dynamic range of hearing-impaired people, with full restoration of audibility. Each subject was fitted with one Danalogic 163D digital hearing aid, using each of the three fitting procedures in turn; the order was counter-balanced across subjects. Prescribed insertion gains for 55 and 80 dB SPL input levels were verified using real-ear measurements. Immediately after fitting with a given procedure, and 1 week after fitting. the gains were adjusted, when required, by the minimum amount necessary to achieve acceptable fittings. On average, the adjustments were smallest for the CAMREST procedure, slightly larger for the CAMEQ procedure, and largest of all for DSL [i/o]. For the DSL [i/o] the gain changes were mostly negative, especially for high frequencies and the higher input level. After these gain adjustments, users wore the aids for at least 3 weeks before speech reception thresholds (SRTs) for sentences in quiet and in steady and fluctuating background noise were measured. The APHAB questionnaire was also administered. The hearing aids were then refitted with the next procedure. SRTs and APHAB scores did not differ significantly between the three procedures. We conclude that the CAMEQ and CAMREST procedures provide a more appropriate initial fitting than DSL [i/o] for unilaterally experienced hearing aid wearers. Comparison with our earlier study based on bilateral fittings suggests that the preferred gains are similar for unilateral and bilateral fittings.

Acoustic Stimulation↗

[Acclimatization: speech recognition in hearing aid users].

BACKGROUND: acclimatization is the period that succeeds the fitting of hearing aids, when a progressive improvement of the hearing and speech recognition abilities is observed due to the new speech cues that are available to the hearing aid user. AIM: to verify acclimatization after the fitting of hearing aids through objective (speech tests) and subjective (Questionnaire) evaluations. METHOD: 16 hearing impaired individuals were evaluated on the first day of hearing aid fitting and were monthly reassessed for three months. In all three months the following speech tests were used: PISR - percentage index of speech recognition through monosyllabic words and SRT--speech recognition threshold through sentences, determining the speech/ noise ratio (S/N). The International Outcome Inventory of Hearing Aid (IOI-HA) was also applied in the first and third months after the hearing aids were fitted. RESULTS: the comparison between the first day, first, second and third months after the hearing aids were fitted revealed a statistically significant improvement (p<0.001) between the results, not only for the PISR but also for the S/N ratio. No statistically significant difference was found for the results obtained through the questionnaire applied in the first and third months. CONCLUSION: the objective evaluation, using speech recognition tests, presents better results in the months following the hearing aids fitting indicating a progressive improvement in the speech abilities from the first month onwards. The subjective evaluation does not reveal an improvement when comparing the first and third moths after the hearing aids were fitted.

Adaptation, Physiological↗

Scanning electron microscopy evaluation of the interfacial fit of interchanged components of four dental implant systems.

The introduction of the original Swedish implant system (Brånemark) was followed by several alternative implant systems with implants and components that closely resembled the original design and treatment protocol. Some of these alternative systems may be interchangeable. Manufacturing variations can result in as much as 0.1 mm of space between the component parts. The implant/abutment interface fit was evaluated by scanning electron micrography for each of four implant systems, as well as interchanged components between the various systems. Results showed that certain implant system abutments are interchangeable, and that the accuracy of fit meets with or exceeds the criteria set by the original Swedish system.

Dental Abutments↗

[Design, production and clinical application of custom total hip prosthesis].

The key to the research of the hip prosthesis is to prolong the effective using time of the hip prosthesis, but bone loss and aseptic loosening are the influential factors in this aspect. Since each person has his own characteristic, it is difficult for the standard hip prosthesis to fit with the patient's femoral canal, so the stability can not the ensured. Moreover, some patients have congenital abnormality or a serious defect in bone or arthrosis, which makes an obvious deviation from the normal, therefore they can not use the standard hip prosthesis. CAD/CAM is useful for to individual three-dimensional femoral reconstruction, which can improve the stability of the prosthesis and effectively prevent the loosening of prosthesis. This article introduces the advantage, design, production and the problems of custom CAD/CAM hip prosthesis.

Arthroplasty, Replacement, Hip↗

[Special case report: Gangrene of all 4 extremities caused by disseminated intravascular coagulation in pneumococcal sepsis].

The rare case of a child with gangrene of all extremities following intravascular coagulation in pneumococcus septicaemia is described. The two years old spanish girl showed a gangrene of all four extremities and accompanying celloid scars. The operative treatment, the orthopaedic technical fitting as well as the problems are discussed.

Amputation, Surgical↗