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At least 1,315 records · Page 73Linked to original sources
PubMed2006

Objective and subjective responses in patients refitted to daily-wear silicone hydrogel contact lenses.

PURPOSE: Silicone hydrogel (SiH) lenses offer many physiological advantages for daily wear (DW) in addition to the continuous-wear modality for which they were originally developed. The purpose of this study was to investigate the clinical performance and physiological responses in a group of successful long-term wearers of conventional hydrogel lenses when refitted with DW SiH contact lenses. METHODS: Eighty-seven successful soft lens wearers (8.4+/-4.7 years of prior lens wear) participated in this study. Bulbar and limbal hyperemia were subjectively graded and digitally photographed for subsequent masked objective evaluation. Subjective symptoms were scored using visual analog scales. In addition, refractive error, corneal curvature, and corneal thickness were measured. All subjects were refitted with Focus Night & Day (lotrafilcon A) SiH lenses; however, to reduce the potential for bias, they were informed that they were being randomly assigned to wear either low oxygen permeability (Dk) lenses or high Dk SiH lenses and were "masked" as to their lens assignment. Subjects returned after 1 week, 1 month, and 2 months of DW, at which time all gradings, photographs, and measurements were repeated. End-of-day subjective symptoms were also graded periodically during the study. RESULTS: Ninety-three percent of subjects were successfully refitted. Both objective and subjective evaluations showed that bulbar and limbal hyperemia decreased significantly in all quadrants during the study (p<0.001), particularly for those subjects with greater baseline hyperemia (p<0.001). Subjects reported a concurrent reduction in end-of-day dryness and improved end-of-day comfort compared with their habitual lenses (p<0.001). No significant changes in refractive error, tarsal papillary response, corneal curvature, or corneal thickness were found during the study. CONCLUSIONS: Hyperemia in contact lens wearers may be attributed to a number of factors, including hypoxia. Refitting existing low Dk lens wearers with SiH lenses on a DW basis can result in a decrease in hyperemia, which may be significant for some subjects and also results in improvements in symptoms of dryness and discomfort.

Adolescent↗
PubMed2006

Skin problems in an amputee clinic.

OBJECTIVE: To document the type and frequency of individual residual limb skin problems among patients using a lower extremity prosthesis, including the suggested etiology and management of each type of skin problem. DESIGN: This is a 6-yr retrospective chart review of skin lesions diagnosed in patients examined in an outpatient amputee clinic at a regional, referral rehabilitation hospital in Ottawa, Canada. Skin lesions were included if they were on a lower extremity residual limb for a patient who functionally used a prosthesis. Descriptive statistics were used to analyze data. RESULTS: A total of 528 skin problems were documented in 337 lower extremity residual limbs. Ulcers, irritations, inclusion cysts, calluses, and verrucous hyperplasia were the five most common skin problems representing 79.5% of all documented skin disorders. CONCLUSIONS: This study demonstrated that a wide variety of dermatologic conditions occurred frequently in the lower extremity amputee who functionally used a prosthesis. Five types of skin problems accounted for nearly 80% of the skin lesions identified. Future studies are required to evaluate prevention and management of the most frequent skin problems.

Adult↗
PubMed2004

Bilateral lower leg replantation versus prosthetic replacement: long-term outcome of amputation after an occupational railroad accident.

BACKGROUND: This retrospective study investigated three very similar cases of bilateral lower leg amputation. The aim was to determine which of two therapeutical procedures is associated with better long-term outcome: replantation or primary treatment of the stumps and subsequent prosthetic replacement. METHODS: Evaluation included clinical examination, gait analysis, and a workup of the psychosocial background. Health problems were documented using the Nottingham Health Profile. Follow-up assessments were performed 6, 7, and 18 years after the trauma. RESULTS: One patient underwent successful bilateral lower leg replantation and continued to work for the same employer. Two patients underwent prosthetic replacement. One became a social outcast confined to a wheelchair. The other patient had a good psychosocial background, similar to that of the patient who underwent replantation. He showed a better gait analysis on even ground than the replantation patient, but the findings were vice versa for uneven ground. CONCLUSIONS: The decision between replantation and prosthetic replacement after bilateral lower leg amputation is case related and cannot be generalized. Patients who have undergone these procedures require long-term psychological and physiotherapeutic care to achieve a good long-term surgical outcome.

Activities of Daily Living↗
PubMed2007

Alignments and clinical results in conventional and navigated total knee arthroplasty.

In this prospective, randomized, controlled study, we compared the performance of conventional and navigated total knee arthroplasties. Component alignment was measured in 60 patients operated on using navigation and in 60 patients operated on using the conventional technique. The groups then were divided into a subpopulation to measure alignments of the distal femoral cuts in the three anatomic planes, the proximal tibial cut in the frontal and sagittal planes, and the resulting lower limb mechanical axis in the frontal plane. Postoperative weightbearing long-view radiographs were evaluated as were clinical results using three standard questionnaires at 28 months followup. The intraoperative measurements (mean +/- standard deviation) at the resection planes showed navigated surgeries result in more accurate alignments than conventional surgeries for the femur: in the frontal plane, 0.1 degrees +/- 0.9 degrees and 0.7 degrees +/- 1.6 degrees valgus, respectively; in the sagittal plane, 1.1 degrees +/- 1.8 degrees and 2.8 degrees +/- 2.0 degrees flexion; and in the transversal plane, 0.1 degrees +/- 1.2 degrees and 0.9 degrees +/- 1.7 degrees internal rotation. The navigated technique also reduced the number of cases with final mechanical axes greater than 3 degrees from 20.0% to 1.7%. Postoperative radiographs showed better component alignment using navigation, particularly at the femur. However, clinical scoring systems showed this radiographic improvement did not necessarily result in a better clinical outcome at short-term followup.

Aged↗
PubMed1993

The supply of orthotist prosthetists. The application of workforce projection techniques in determining future national training places.

Discusses the application of workforce planning techniques in the context of "target" levels of demand and uses a study of the future supply of orthotists and prosthetists as an example. Describes the derivation of an appropriate model, the quantification of the labour market for the profession, and an analysis of the characteristics of the workforce. Information was gathered through two surveys and from discussions with relevant organizations.

Allied Health Personnel↗
PubMed1993

Automated tuning of a closed-loop hand grasp neuroprosthesis.

An automated tuning algorithm was developed to reduce the time and skill required to tune a closed-loop hand grasp neuroprosthesis. The time reduction results from simultaneous tuning of four gain parameters controlling the dynamic response of the system, and from automation of the calculation and decision processes. The new tuning method is therefore an automated parallel tuning method, replacing a manual sequential method in which only one parameter at a time was tuned. RMS error between the step input and the grasp output is minimized, with absence of oscillation as a constraint. The difference between the system's RMS ramp tracking errors for the two tuning methods was less than 1% of the ramp size regardless of the initial values of the parameters, implying that the tuning methods were equivalent. However, the parallel tuning method was faster and required fewer trials than the sequential method. The capability of the closed-loop system to regulate grasp output in the presence of disturbances was compared with the capability without feedback. Patients were instructed to either grasp an object at a certain force level or to match a certain grasp opening. They would then lock their command at a fixed value, and either remain immobile to test time dependence or pronate and supinate their forearm to test postural disturbances. With closed-loop control, the grasp output was better regulated in the presence of disturbances, with an average output variance 60% lower than without feedback control.

Algorithms↗
PubMed1996

Interface mechanics in lower-limb external prosthetics: a review of finite element models.

The distribution of mechanical stress at the interface between a residual limb and prosthetic socket is an important design consideration in lower-limb prosthetics. Stresses must be distributed so that the amputee is stable and comfortable, while avoiding trauma to the tissues of the residual limb. Numerical estimation of the stresses at the interface through finite element (FE) modeling can potentially provide researchers and prosthetists with a tool to aid in the design of the prosthetic socket. This review addresses FE modeling of interface stresses in lower-limb external prosthetics. The modeling methodologies adopted by analysts are described. Verification of FE estimates of interface stress against experimental data by different analysts is presented and the likely sources of error discussed. While the performance of the models is encouraging, there are definite limitations to all of them, necessitating further improvements. Parametric analysis of the sensitivity of interface stress to model parameters provides a tool to identify model weaknesses and to suggest possible refinements. Parametric analyses by different analysts are also presented and potential refinements discussed. Finally, directions for future work in prosthetic FE modeling are suggested.

Amputees↗
PubMed1996

A finite element analysis of the load transfer between an above-knee residual limb and its prosthetic socket--roles of interface friction and distal-end boundary conditions.

A nonlinear finite element model was developed to investigate the manner of the load transfer between the above-knee residual limb and its prosthetic socket. The model was two-dimensional (2-D) with consideration of nonlinear boundary conditions and large deformation. Interface elements were used to simulate the friction/slip conditions between skin and the socket. Different distal-end conditions, including air cushion distal-end loading, were simulated to explore their influences on the load transfer.

Amputation Stumps↗
PubMed1998

Effects of alignment changes on stance phase pressures and shear stresses on transtibial amputees: measurements from 13 transducer sites.

Interface pressures and shear stresses were measured at 13 sites on two unilateral below-knee amputee subjects ambulating with lower-limb patellar-tendon-bearing prostheses. Interface stresses at the time of the first peak in the shank axial force-time curve were investigated at different socket-shank alignment settings. Stress magnitudes ranged from 1.2 to 214.7 kPa for pressure and 0.4 to 79.6 kPa for resultant shear stress, and changes in stress due to misalignment ranged from 1.3 to 80.7 kPa for pressure and from 0.2 to 38.0 kPa for resultant shear stress. For both subjects interface stress changes were much greater in the anterior socket region than in the lateral or posterior regions. Thus, alignment changes had a localized effect on interface stresses. Plots of alignment versus pressure or resultant shear stress were nonlinear for both subjects, in a number of cases maximizing or minimizing at the nominal alignment, indicating complex interface stress-alignment relationships. Variation (standard deviation/mean) was not significantly different for nominal versus misaligned steps, indicating that the subjects adapted well to the alignment changes. Session to session differences in interface stresses were typically larger than interface stress differences induced by alignment modifications. Thus, while these subjects compensated well for alignment changes to maintain consistent interface stresses within a session, they did not do so for different sessions conducted weeks apart.

Adult↗
PubMed1998

A programmable sound processor for advanced hearing aid research.

A portable sound processor has been developed to facilitate research on advanced hearing aids. Because it is based on a digital signal processing integrated circuit (Motorola DSP56001), it can readily be programmed to execute novel algorithms. Furthermore, the parameters of these algorithms can be adjusted quickly and easily to suit the specific hearing characteristics of users. In the processor, microphone signals are digitized to a precision of 12 bits at a sampling rate of approximately 12 kHz for input to the DSP device. Subsequently, processed samples are delivered to the earphone by a novel, fully-digital class-D driver. This driver provides the advantages of a conventional class-D amplifier (high maximum output, low power consumption, low distortion) without some of the disadvantages (such as the need for precise analog circuitry). In addition, a cochlear implant driver is provided so that the processor is suitable for hearing-impaired people who use an implant and an acoustic hearing aid together. To reduce the computational demands on the DSP device, and therefore the power consumption, a running spectral analysis of incoming signals is provided by a custom-designed switched-capacitor integrated circuit incorporating 20 bandpass filters. The complete processor is pocket-sized and powered by batteries. An example is described of its use in providing frequency-shaped amplification for aid users with severe hearing impairment. Speech perception tests confirmed that the processor performed significantly better than the subjects' own hearing aids, probably because the digital filter provided a frequency response generally closer to the optimum for each user than the simpler analog aids.

Biomedical Engineering↗
PubMed2000

Performance of digital filtering methods in orthotic and prosthetic CAD/CAM.

This report characterizes the performance of three digital filters, when applied to residual limb shape maps. The three filters were an averaging filter, a uniform window Fourier filter, and a Hamming window Fourier filter. The frequency responses of the three filters were calculated from theory, and experimentally observed. Experimental observations consisted of responses on single-frequency lobed shapes, and on residual limb shapes. Seven trans-tibial limb molds were digitized, three times each. Each resulting shape was then passed through each of the three filters. The before and after shapes were then compared. A Hamming window filter (low-pass frequency of 10 cycles per revolution, 24 coefficients, Hamming number of 0.25) achieved the best performance based on maintained amount of residual limb frequencies, and on visual observation.

Computer-Aided Design↗
PubMed2005

Development of a force amplitude- and location-sensing device designed to improve the ligament balancing procedure in TKA.

To improve the ligament balancing procedure during total knee arthroplasty a force-sensing device to intraoperatively measure knee joint forces and moments has been developed. It consists of two sensitive plates, one for each condyle, a tibial base plate and a set of spaces to adapt the device thickness to the patient-specific tibiofemoral gap. Each sensitive plate is equipped with three deformable bridges instrumented with thick-film piezoresistive sensors, which allow accurate measurements of the amplitude and location of the tibiofemoral contact forces. The net varus-valgus moment is then computed to characterize the ligamentous imbalance. The developed device has a measurement range of 0-500 N and an intrinsic accuracy of 0.5% full scale. Experimental trials on a plastic knee joint model and on a cadaver specimen demonstrated the proper function of the device in situ. The results obtained indicated that the novel force-sensing device has an appropriate range of measurement and a strong potential to offer useful quantitative information and effective assistance during the ligament balancing procedure in total knee arthroplasty.

Arthroplasty, Replacement, Knee↗
PubMed2002

Evaluation of command algorithms for control of upper-extremity neural prostheses.

Five new command control algorithms were created to enable increased control over grasp force in upper-extremity neural prostheses. Most of these algorithms took advantage of the ability to lock or assign a steady command value to the hand neural prosthesis. Five able-bodied subjects tested the algorithms by using a shoulder controller that controlled a video-simulated hand to repeatedly complete a consistent evaluation task. A generalized estimating equations-based linear model was used to analyze the data. The algorithms were ranked via contrast analyses between the coefficient values from the linear model of the proportional control with lock algorithm, which is the algorithm presently used in neural prostheses, and each of the other algorithms. The algorithms that allowed adjustment of the command value after the hand was locked as well as algorithms that allowed a decrease in controller gain after the hand was locked performed better than the proportional control with lock algorithm. Algorithms that changed command as a function of time performed worse than the proportional control with lock algorithm. Further, the computer-based video simulator proved to be useful as a first-pass evaluation tool for neural prosthesis control.

Adult↗
PubMed2005

Learning prosthetic vision: a virtual-reality study.

Acceptance of prosthetic vision will be heavily dependent on the ability of recipients to form useful information from such vision. Training strategies to accelerate learning and maximize visual comprehension would need to be designed in the light of the factors affecting human learning under prosthetic vision. Some of these potential factors were examined in a visual acuity study using the Landolt C optotype under virtual-reality simulation of prosthetic vision. Fifteen normally sighted subjects were tested for 10-20 sessions. Potential learning factors were tested at p < 0.05 with regression models. Learning was most evident across-sessions, though 17% of sessions did express significant within-session trends. Learning was highly concentrated toward a critical range of optotype sizes, and subjects were less capable in identifying the closed optotype (a Landolt C with no gap, forming a closed annulus). Training for implant recipients should target these critical sizes and the closed optotype to extend the limit of visual comprehension. Although there was no evidence that image processing affected overall learning, subjects showed varying personal preferences.

Adolescent↗
PubMed2006

An experimental and theoretical framework for manufacturing prosthetic sockets for transtibial amputees.

Selective laser sintering (SLS) is a powerful manufacturing technology that does not require part-specific tooling or significant human intervention and provides the ability to easily generate parts with complex geometric designs. The present work focuses on developing a manufacturing framework using this technology to produce subject-specific transtibial amputee prosthetic sockets made of Duraform PA, which is a nylon-based material. The framework includes establishing an overall socket design (using the patellar-tendon bearing approach), performing a structural analysis using the finite element method (FEM) to ensure structural reliability during patient use, and validating the results by comparing the model output with experimental data. The validation included quantifying the failure conditions for the socket through a series of bending moment and compression tests. In the case study performed, the FEM results were within 3% of the experimental failure loads for the socket and were considered satisfactory.

Amputation Stumps↗