Energy expenditure and biomechanical characteristics of lower limb amputee gait: the influence of prosthetic alignment and different prosthetic components

In this study, the influence of different prosthetic alignments and components on oxygen consumption and the important biomechanical characteristics of the normal gait pattern of leg amputees was investigated. With 15 transtibial and 12 transfemoral amputees, the oxygen consumption during walking on a treadmill was analyzed and biomechanical parameters during walking on even ground at a self-selected speed were defined. The amputation of all patients was caused by trauma. Variations of the prosthetic alignment affect the energy consumption of transfemoral amputees more significantly than that of transtibial amputees. Comparison of different prosthetic feet worn by transtibial amputees did not show significant differences regarding metabolic parameters. Compared with conventional hydraulic knee controls, the oxygen consumption of transfemoral amputees provided with an electronically controlled hydraulic knee joint is reduced. All investigated variations can be clearly characterized by the sagittal moments acting on the joints of the prosthetic limb during gait.

A clinical overview of removable prostheses: 3. Principles of design for removable partial dentures

Removable partial dentures (RPDs) should not be made for patients unless they are necessary. Most partial dentures have the potential to cause some damage to the teeth and supporting tissues, however well they are designed and constructed; the criteria for selecting such devices were described in a previous article. In general there is merit in, wherever possible, reducing tissue coverage as much as possible when RPDs are being planned. This article, the third in a series on the prescription of RPDs, discusses the design principles involved.

Opting for two hearing aids: a predictor of long-term use among adult patients fitted after screening

This study is a follow-up of patients fitted with one or two hearing aids, approximately 10 years previously. Our patients were identified through population screening for hearing difficulties when they were aged 50-65 years. At the time, they had a trial of unilateral and bilateral fittings, and then they made their own choice to keep one or two aids. We found that 10 of the 12 who had opted for two aids and were available for follow-up 10 years later continued using at least one aid (83%, 95% CI 55-95). Six of the 17 who opted for unilateral fitting and were available for follow-up used a hearing aid in the long term (35%, 95% CI: 17-59%). Therefore, this study suggests that people who are identified through population screening, are bilaterally impaired, are willing to try bilateral fitting, and choose to continue with two aids, are likely to become long-term users of (one or two) hearing aids. Those who choose to continue with one aid after a trial of bilateral fitting are at high risk of rejecting the aid in the long term. Our sample is small, and we took a number of steps in the analysis in order to clarify whether these findings are reliable. We could not identify any confounding factors. The patients' preference for continuing with bilateral or unilateral aids after fitting was the only predictor of long-term use in our sample. Remarkably, bilateral preference was a better predictor of long-term use than the degree of hearing impairment. We discuss how this study provides useful information for planning population screening for hearing difficulties in middle age.

Factors that allow a high level of speech understanding by patients fit with cochlear implants

Three factors account for the high level of speech understanding in quiet enjoyed by many patients fit with cochlear implants. First, some information about speech exists in the time/amplitude envelope of speech. This information is sufficient to narrow the number of word candidates for a given signal. Second, if information from the envelope of speech is available to listeners, then only minimal information from the frequency domain is necessary for high levels of speech recognition in quiet. Third, perceiving strategies for speech are inherently flexible in terms of the mapping between signal frequencies (i.e., the locations of the formants) and phonetic identity.

Treating the modern complete denture patient: a review of the literature

This article reviews the physical and mental compromises of today's patients, techniques, materials, occlusion, impressions, and soft liners and makes recommendations as to managing these compromises when fabricating complete dentures. References used were primarily from the "classical literature," and an effort was made to ascertain whether these treatment recommendations are appropriate for today's more difficult patients. An effort was made to incorporate recent recommendations where appropriate.

Developing an optimal emergence profile of the definitive restoration with a modified impression cap technique for ITI solid abutment

There appears to be no convenient method for fabricating an optimal emergence profile for the definitive restoration of an ITI solid abutment when the implant is installed subgingivally. This article describes an efficient technique to solve this problem and reviews its advantages and disadvantages.

Clinical performance and factors affecting the physical fit of a soft toric frequent replacement contact lens

BACKGROUND

Differences in ocular parameters between Chinese and Caucasian eyes may lead to differences in the success rate of soft contact lens fittings. As most disposable or frequent replacement lenses are manufactured based on data of Caucasian eyes, the aim of this study was to investigate the clinical performance and factors affecting the preliminary fitting of a 'one-fit' bi-weekly replacement soft toric lens on Hong Kong (HK)-Chinese.

METHOD

Forty-one HK-Chinese were fitted with Acuvue soft toric lenses (on one eye only). The success rate, the comfort, vision and the effects of central corneal curvature, horizontal visible iris diameter (HVID) and palpebral aperture size (PAS) on the physical fit of the toric lenses were determined.

RESULTS

Twenty-four of 41 eyes (58.6 per cent) attained acceptable fit and satisfactory vision with these lenses. The main reason for unsuccessful lens fit was loose fitting. Only central corneal curvatures were significantly correlated (statistically) to the looseness of the lens.

DISCUSSION

The results showed that about 40 per cent of our subjects were unable to obtain acceptable fit with this one-fit frequent replacement lens, the main reason for which was loose fit. This was expected due to the steeper corneas of the Chinese eyes and we would expect similar results with other one-fit soft lenses. Only the central corneal radii were significantly correlated with the looseness of the lens fit. However, this factor was not the main factor affecting the contact lens fitting. HVID and PAS did not appear to play any significant role in the physical fit of this lens. As there are individual variations of lens fitting behaviour, trial lens fitting assessment is the most suitable way to select the appropriate lens.

Periprosthetic modelling of femoral component fit using computed tomography data for total hip arthroplasty: a feasibility study

The aim of the work was to create a new three-dimensional periprosthetic multi-criteria optimisation technique to identify the best six degrees of freedom transform to position a porous-coated anatomic cementless femoral component for three factors, including: first, maximisation of the degree of contact achieved between designated bone ingrowth surfaces and the periprosthetic bone; secondly, minimisation of the bone mass to be removed to accommodate the component and thirdly, the extreme constraint of the component to be positioned so that it does not project beyond the periosteum. Discrete integrals were computed over regions of interest derived from the polyhedral component mesh in transaxial CT scan planes, using a polygon scan-conversion algorithm. A new biomedical imaging volume rendering technique utilising dynamic virtual textures was developed to visualise the design trade-offs. Pareto-optima were identified for four femora that matched an average-sized component. The non-linear, multi-modal fit metric was quadratic near minima, with a narrow trough of equivalent fit values within 3mm of translation and 3 degrees of rotation with respect to the canal axis, and possessed a dependence most pronounced for distal-directed insertion against varus/valgus rotation. The study gives previously unavailable data on the three-dimensional femoral component fit and is the first report that demonstrates that fitting the implant using several design criteria in a multi-criteria optimisation scheme is feasible.

The Asian nose: augmentation rhinoplasty with L-shaped silicone implants

Few procedures in facial plastic surgery elicit the controversy that surrounds augmentation of the Asian nose. Asian surgeons generally advocate augmentation with custom-fabricated silicone prostheses, a technique that Western surgeons, who strongly recommend autogenous material, condemn as inherently dangerous. Analysis of the evidence relating to augmentation with silicone prostheses suggests that there is little factual support for Western dogma and indicates that, when properly executed, augmentation with silicone implants yields reliable and consistently superior aesthetic results. A detailed blueprint for execution of augmentation rhinoplasty with custom- fabricated silicone implants is provided.

Preliminary ossiculoplasty results using the Kurz titanium prostheses

OBJECTIVE

Limitations in biocompatibility and hearing improvement with ossicular chain reconstruction prostheses are addressed with new, lightweight titanium prostheses designed to maximize visualization of the capitulum and footplate regions. The effectiveness of these new prostheses is being tested in a prospective multicenter study.

STUDY DESIGN

Prospective case series.

SETTING

Multicenter (8 sites), primarily tertiary private practice or academic otologic clinics.

PATIENTS

A convenience sample of 31 patients undergoing ossiculoplasty, with 16 partial ossicular chain reconstructions using the Bell prosthesis and 15 total reconstructions using the Aerial prosthesis.

INTERVENTION

Ossiculoplasty using new Kurz titanium prostheses. Cartilage was interposed between the tympanic membrane and the prosthesis.

MAIN OUTCOME MEASURES

Air-bone gap for pure tone average and 3,000 and 4,000 Hz, assessed preoperatively and 3 months, 6 months, and 12 months postoperatively; percent of patients obtaining an air-bone gap of </=20 dB; high-frequency average (1,000, 2,000, and 4,000 Hz) to evaluate sensorineural hearing loss; and extrusion rate.

RESULTS

A postoperative air-bone gap of </=20 dB was obtained in 81% of Bell prosthesis patients and 67% of Aerial prosthesis patients at 3 months. The results were stable to improved for later time intervals. High-frequency gaps were similar to the pure tone average gap. To date, there have been no instances of extrusion, and all the surgeons found the prostheses easy to use and thought that the design characteristics facilitated accurate placement.

CONCLUSIONS

Initial evaluation of the Kurz titanium prostheses produced low extrusion rates (none to date) with excellent hearing results, including good high-frequency conduction. Good visualization and accurate placement were easy to achieve. Further studies are needed to confirm long-term efficacy.

Practice of orthokeratology by a group of contact lens practitioners in Hong Kong--Part 1. General overview

PURPOSE

To describe orthokeratology (ortho-k) as practised by a number of practitioners in Hong Kong.

METHODS

Twelve optometrists who had been practising ortho-k for between 2.5 and four years were interviewed in the period 1 March to 30 June 2001.

RESULTS

The number of ortho-k cases seen by each practitioner ranged from 50 to 800, and the main reason for fitting was myopia control in children. All practitioners were using advanced ortho-k lens designs and most recommended night therapy. In general, patients were accepted if they had less than five dioptres of myopia; one or two lenses were required for a myopia reduction of four dioptres or less, whereas two to four lenses were required to achieve reduction of more than four dioptres. Success, defined as the percentage of the target reduction agreed with patients that was actually achieved, was reported as better than 80 per cent for most practitioners. The time for trial lens wear was from 15 minutes to four hours and was 30 minutes in most cases. Suction holders were generally used for lens removal. Foggy vision was the most frequently reported adverse symptom and mild corneal staining the most frequent sign.

CONCLUSIONS

It is clear that there is considerable variation in the practice of ortho-k in Hong Kong even among the relatively experienced practitioners interviewed here. The skills of contact lens practitioners in Hong Kong vary considerably because of the nature of the registration arrangements. We suggest that a statement of best clinical practice for ortho-k should be developed to assist practitioners to carry out this procedure effectively and safely.

Fit of current glenoid component designs: an anatomic cadaver study

The glenoids of 412 scapula specimens were templated with the use of 6 currently available glenoid systems to determine the goodness of fit for the various designs. When a fitting criterion of a mismatch of less than 2 mm between the template and the actual glenoid periphery for 8 radial locations was used, the various designs fit from 0% to 48% of the glenoids. Because glenoid component fixation longevity can depend on the degree of osseous support, these results indicate that glenoid component design and sizing can be improved.

Speech perception in nucleus CI24M cochlear implant users with processor settings based on electrically evoked compound action potential thresholds

Adjusting the speech processor of a cochlear implant, per electrode, to the individual's response is a laborious task that may interfere with a user-friendly start of implant-mediated hearing, particularly in children. This research concerns the possibility of processor adjustment based on a profile derived from measurements of the electrically evoked compound action potential (ECAP) thresholds across the electrode array, followed by adjustment of the overall level of the profile to the hearing threshold and maximum comfortable loudness level using live voice. The results for CVC word lists show that speech perception is quite insensitive to the threshold setting of the speech processor. On average, the speech score does not decrease by more than 10% when, with the new method, the threshold setting comes out so much lower that the dynamic range has doubled. In contrast, the speech score appears to be sensitive to an increase of the maximum high-frequency stimulation settings for the basal electrodes, resulting in lower scores at these higher settings. The correlation between the overall ECAP thresholds and conventionally measured subjective thresholds is weak (r = 0.64). However, the correlation between the slopes of these threshold curves is satisfactory (r = 0.82). The correlation between the ECAP thresholds and the maximum stimulation levels is poor, both with respect to overall level and slope (r = 0.39 and 0.36, respectively). Applicability of the ECAP threshold in processor adjustment could not be demonstrated in this study. Prediction of the most critical factor in speech perception, the slope of the maximum stimulation curve, from the ECAP thresholds is poor. However, considering habituation to the initial processor setting of at least 6 months, the small decrease in the CVC scores with the new setting suggests that a more user-friendly adjustment procedure can be developed.

[Revision total hip arthroplasty: how do metaphyseal onset, diaphyseal fill and a three-point-stem-fixation influence the postoperative subsidence of a revision straight-stem?]

AIM

It was the purpose of this study to determine the postoperative subsidence of a cementless hip revision stem in regard to the degree of metaphyseal onset, diaphyseal fit and a three-point contact of the stem in the femur.

METHODS

Data of 50 revision total hip replacements using a cementless revision straight stem (PFM-R) could be investigated. The degree of subsidence was measured on pelvic X-rays 6 and 12 months postoperatively. The degree of metaphyseal onset, diaphyseal fit and a three-point contact of the stem in the femur was determined on the immediate postoperative X-rays.

RESULTS

The amount of subsidence was strongly related to the degree of metaphyseal onset. With minor onset (up to 25 % of the possible) stems subsided 9.4 (6 months), respectively, 13.2 millimeters (12 months) in average within the investigation periods. If there was a large degree of metaphyseal onset (more than 75 % of the possible) the average subsidence was only 1.6 (6 months) or 0.9 millimeters, respectively (12 months). Neither the amount of diaphyseal fit nor the presence of three-point contact of the stem in the femur influenced the subsidence significantly. Conclusion The amount of the postoperative subsidence of stems in cementless revision total hip arthroplasty is predominantly influenced by the degree of the metaphyseal onset of the prosthesis.

Interface pressures during ambulation using suction and vacuum-assisted prosthetic sockets

Interface pressures were measured during ambulation with a normal total-surface weight-bearing suction socket and a vacuum-assisted socket. The vacuum-assisted socket has been shown to eliminate daily volume loss. Urethane liners were instrumented with five force-sensing resistors to measure positive pressures and one air pressure sensor at the distal end of the liner to document negative pressures. Nine unilateral transtibial amputees participated in the study. The vacuum-assisted socket created significantly lower positive-pressure impulse (42.8, 39.6 kPa x s) and peak pressures (83.5, 80.0 kPa) during the stance phase. The pressure impulse (-10.5, -13.3 kPa x s), average (-21.2, -26.5 kPa), and peak (-28.5, -36.3 kPa) negative pressures during swing phase were significantly greater in magnitude with the vacuum-assisted socket. We believe that lower positive pressures seen during stance using the vacuum-assisted socket reduces the fluid forced out and greater negative pressures seen during swing increases the amount of fluid drawn into the limb, thereby preventing volume loss.

Contact lens fitting to correct irregular astigmatism after corneal refractive surgery

PURPOSE

To study a technique of contact lens fitting and its visual results in patients with irregular astigmatism induced by corneal refractive surgery.

SETTING

Department of Cornea and Refractive Surgery, Instituto Oftalmológico de Alicante, Alicante, Spain.

METHODS

This prospective noncomparative study comprised 29 eyes with irregular astigmatism after corneal refractive surgery. Different types of contact lenses were used to correct the astigmatism: hard, gas permeable, hybrid, and toric hydrophilic. Preoperative and postoperative data were analyzed for proper fitting including the preoperative keratometeric reading and corneal ablation zone.

RESULTS

Proper contact lens fitting was achieved in 23 eyes (79.3%). In 6 eyes (20.7%), fitting was not possible despite an improvement in best corrected visual acuity (BCVA). Of the eyes with proper fitting, 14 (60.9%) had rigid gas-permeable lenses (9.80 mm), 6 (26.1%) had hydrophilic lenses (14.00 mm), and 3 (13.0%) had hybrid lenses (14.3 mm). Comparing the BCVA with that with spectacles, 23 eyes (79.3%) gained 2 lines or more of BCVA, 4 (13.8%) gained 1 line, and 2 (6.9%) maintained the same acuity as with spectacles. No eye lost lines of BCVA.

CONCLUSIONS

Results indicate that contact lens fitting is a good-and sometimes the only-alternative for patients with induced irregular astigmatism. Rigid gas-permeable contact lenses provided the best visual performance and patient tolerance.

[Endoprosthesis implantation in the elbow joint]

Previously used total elbow prostheses were mainly constrained hinged implants. Their early clinical results were favourable but they failed due to a high rate of loosening already a few years after implantation. The cause for the early loosening was the great forces across the elbow joint which were directly transmitted to the prosthesis-bone interface in these implants. Therefore, these implants were abandoned. Afterwards, unlinked, semiconstrained or non-constrained resurfacing devices were introduced. In these devices, the soft tissues constrain the joint and therefore absorb part of the transmitted forces. The rates of loosening were significantly improved and rarely the cause of early failure. But resurfacing implants require intact condyles and collateral ligaments. These implants can, therefore, only be used in a limited number of indications, and postoperative instabilities are known complications. The currently most frequently used device is the semiconstrained Coonrad-Morrey prosthesis. It is a floppy hinge which allows valgus-varus and rotational laxities. Therefore, a part of the forces across the elbow joint are absorbed by the soft tissues. The loosening rate is not a clinical problem any more, and is with 4% 10 years after implantation (rheumatoid arthritis) similar to that of total hip or knee replacement. Furthermore, this device is stabilised with a small anterior flange to the anterior cortex of the humeral shaft. Condyles and collateral ligaments are therefore not necessary neither for short nor for long-term stability. The Coonrad-Morrey total elbow prosthesis can therefore be used for almost every indication, such as severe destruction of the elbow joint and even in case of complete loss of the distal humerus. The long-term outcome with this prosthesis for the treatment of rheumatoid arthritis is favourable with 96% of very good and good results. Function is restored with an average flexion of 131 degrees, a mean loss of extension of 28 degrees, and an unrestricted pronation and supination. The rate of complications for patients with rheumatoid arthritis is 10%. Similarly, the results for Coonrad-Morrey total elbow replacement for posttraumatic arthrosis are favourable with 83% of satisfactory results. Most patients consider their elbow as improved compared to preoperatively, but pain relief is obtained only in three quarters of the patients. The rate of complications is high with 30%, indicating the total elbow replacement is contraindicated for strenuous labour and sports activities.

Evaluation of electroacoustic test signals I: comparison with amplified speech

OBJECTIVE

To evaluate the ability of clinical test signals to match the aided levels of real speech, across a range of hearing aid circuit types and strengths.

DESIGN

Hearing aids (N = 41) were set to DSL targets for moderate, severe, and profound hearing losses. These hearing aids were tested with three test signals (Fonix Pure Tones, Fonix Composite Noise, and Audioscan Swept), as well as with running speech. The difference between the aided test signal and the aided speech was calculated.

RESULTS

Accuracy of matches between aided test signals and aided speech levels depended on circuit type, signal type, and test level.

CONCLUSIONS

Clinical test signals can more accurately match the aided levels of speech for all types of hearing aids if they are 1) speech-weighted and 2) temporally modulated. Matches were more accurate at low to moderate test levels (i.e., 50 to 70 dB SPL), and less accurate at high test levels (i.e., 85 dB SPL).

[Bone defects in revision total knee arthroplasty: classification and management]

The goal of bone reconstruction in revision total knee arthroplasty is to provide a stable support for the implant and to re-establish the correct joint line. Therefore, a useful, therapy-based classification of the defects is necessary. According to Stockley et al. (1992), the defects are classified into contained and uncontained defects. Uncontained defects can be reconstructed using structural allografts or metal wedges. In contained defects, cancellous allograft can be used. For aseptic loosening of total knee arthroplasty, the defect classification according to Engh and Parks (1994) can be helpful because of its recommendations for reconstruction. In case of the more common first or second graded defects, reconstruction is performed using modular revision components or allografts. For the rare third graded defects, bulk allografts or modular tumour endoprostheses are recommended. On the basis of more than 150 revision total knee arthroplasties performed in our hospital the classification of bone defects and their clinical consequences are presented in this review.

Comparison of total hip arthroplasty performed with and without cement : a randomized trial

BACKGROUND

This study was designed to compare the fixation of a Mallory-Head total hip prosthesis with and without cement.

METHODS

Two hundred and fifty patients with osteoarthritis of the hip were randomized to receive a Mallory-Head total hip prosthesis designed for insertion with cement or the same prosthesis designed for insertion without cement. Neither the patient nor the outcomes assessor was aware of the type of prosthesis. Outcomes were assessed with respect to mortality, revision arthroplasty, health-related quality of life (evaluated with the Harris hip score, Merle d'Aubign and Postel hip score, McMaster-Toronto Arthritis Patient Preference Disability Questionnaire (MACTAR), Western Ontario and McMaster University Osteoarthritis Index (WOMAC), and the time trade-off technique), and the six-minute-walk test. Patients were seen at three, six, and twelve months and yearly thereafter.

RESULTS

The prosthesis was inserted with cement in 124 patients and without cement in 126 patients. The mean age of the patients was sixty-four years, 48% were female, and the mean duration of follow-up was 6.3 years. There were thirteen revisions in the group that had fixation with cement and six in the group that had fixation without cement (p = 0.11), and more femoral components were revised in the group that had fixation with cement (twelve versus one; p = 0.002). All health-related quality-of-life measures improved postoperatively in both groups.

CONCLUSIONS

In this randomized trial, the group that had the cemented Mallory-Head hip prostheses required more revisions of the femoral component than did the group with the cementless Mallory-Head prostheses, which was perhaps related to the titanium-alloy femoral stem. Our findings are specific to the implants evaluated in this study.

Initial selection of soft contact lenses based on corneal characteristics

PURPOSE

To determine apical radius, surface asphericity, and horizontal visible iris diameters (HVID) in normal subjects and to find out which has the greatest influence on the corneal sagittal depth.

METHODS

Videokeratoscopic data were analyzed to determine the apical radius and the p-value of the near horizontal principal meridian for 73 right and 77 left eyes. The HVID also were measured.

RESULTS

Scatterplots of sagittal depth versus apical radius, p-value, and HVID indicated the strongest association between the sagittal depth and the HVID.

CONCLUSIONS

Normal variations in corneal asphericity have the least influence whereas normal variations in HVID have the greatest influence in changing the corneal sagittal depth. The most appropriate measurement to take to select the optimum soft contact lens specification may be the HVID.

Effect of lens base curve on subjective comfort and assessment of fit with silicone hydrogel continuous wear contact lenses

PURPOSE

To study the effect of base curve on subjective comfort of silicone hydrogel extended wear lenses.

METHODS

Ninety-five subjects were first trial fitted with 8.6-mm base curve lotrafilcon A (Focus Night & Day) lenses and then with 8.4-mm lenses only if poor subjective comfort or poor fit was present. Comfort and fit were assessed after 15 min. Subjects with discomfort or signs of poor fit were then trial fitted with 8.4-mm lenses.

RESULTS

Of 190 eyes, 74.2% were fitted with 8.6-mm lenses, and 23.7% required 8.4-mm lenses. Two (2.1 %) subjects could not be fitted with either base curve. Mean steep keratometry (K) reading for eyes dispensed with 8.6-mm lenses was 43.88 D and 45.56 D for eyes dispensed in the 8.4-mm lenses (p < 0.001).

CONCLUSIONS

A clinically useful criterion showing the need for 8.4-mm lenses was steep K of > or = 45.50 D; 77% of these eyes required the steeper lens for good comfort and fit. Subjective discomfort with 8.6-mm lenses was also a useful signal for the need of a steeper lens; mean comfort scores for those subjects rose from 6.33 with 8.6-mm lenses to 9.44 with the 8.4-mm lenses for eyes requiring the steeper lens (p < 0.001).