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PubMed1994

Within-subject comparisons of implant-supported mandibular prostheses: choice of prosthesis.

Although previous studies have demonstrated that implant-supported prostheses are more satisfactory and efficient for edentulous patients than are conventional prostheses, until now no investigation has directly compared different types of implant-supported prostheses. We carried out a within-subject cross-over clinical trial with fixed and long-bar removable implant-supported mandibular prostheses. Fifteen subjects were randomly divided into two groups. One group received the fixed prosthesis first, while the other first received the removable. After a two-month adaptation period, psychometric measurements of various aspects of the prostheses and physiological tests of masticatory efficiency were carried out. The prostheses were then changed, and the procedures repeated. At the end of the study, subjects chose the prosthesis they wished to keep. In this paper, we report on the data gathered at this last appointment. Eight subjects chose the fixed (F group), and seven chose the removable (R group). Both groups rated stability and ability to chew with the fixed as significantly better than with the removable. However, the R group rated ease of cleaning as the most important factor governing their decision, followed by esthetics and stability. The F group considered stability to be the most important factor in their decision, followed by chewing ability and ability to clean. There was a tendency for the removable to be chosen by older subjects (+50 years). These results suggest that patients choose fixed or removable implant-supported prostheses for specific reasons, and that patient attitudes should be considered when the design of a prosthesis is being planned for an individual patient.

Adaptation, Psychological↗
PubMed1996

Maximum likelihood estimates for the lifetime of bonded dental prostheses.

Clinical studies measuring the lifetime of dental prostheses produce censored data when not all specimens have failed during the course of the study. Such clinical data can be analyzed by the Weibull probability distribution function. Algorithms are presented that provide the maximum likelihood estimates of the distribution's parameters. These parameters are the characteristic lifetime (time to failure for 63% of the specimens of the total sample) and the Weibull or shape parameter. Two iterative methods for solving the maximum likelihood equations are given. These mathematical methods have been applied to the results from a retrospective clinical investigation into the lifetime assessment of resin-bonded prostheses. This study evaluated 164 resin-bonded prostheses (for 146 patients) placed between January, 1980, and May, 1985. To date (April, 1995), 47 prostheses (29%) have failed with a median time in service of 74 months (6.2 yr). For the surviving prostheses, the median time in service is 123 months (10.3 yr) and still increasing. The maximum likelihood estimate of the characteristic lifetime for these restorations is 255 months (21.3 yr). Differences in the characteristic lifetime were observed between prostheses placed anteriorly, 338 months (28 yr), and posteriorly, 207 months (17 yr). Since there are no rigorous confidence intervals for deeply censored samples, only provisional confidence bounds could be determined, which substantiated the observed differences. The Weibull modulus value of 1.5 indicates that the probability of failure for resin-bonded prostheses begins to decrease after 10 years in service.

Algorithms↗
PubMed1992

Hydroxylapatite ossicular replacement prostheses: a four-year experience.

Between 1987 and 1991, I have used 215 hydroxylapatite middle ear implants, in various styles, for hearing reconstruction. The first such implants were composed entirely of hydroxylapatite. Because of intraoperative difficulties in shaping and trimming these prostheses, hybrid prostheses using Plasti-Pore were developed. For each of four implant designs (incus, incus-stapes, PORP, and TORP), the head is constructed from hydroxylapatite and the shaft from Plasti-Pore. Extrusion rate for the hybrid prostheses is low (4.3%). Hearing results from 47 patients with the hybrid hydroxylapatite prostheses, 140 patients with total hydroxylapatite prostheses, and 75 control group patients with homograft bone or Plasti-Pore prostheses were compared. A "successful" hearing result was achieved in 51.1%, 51.4%, and 60.0% of the three groups, respectively. Surgical technique for use of the new hybrid hydroxylapatite prostheses is described.

Adolescent↗
PubMed2001

Risk assessment for surgical site infections following total hip and total knee prostheses.

The purpose of the study was to assess the relative importance of risk factors for surgical site infections (SSI) following total hip and total knee prostheses in The Netherlands. In the period 1996-99 63 hospitals in The Netherlands registered SSI after 36,629 orthopedic operations. Total hip and total knee prostheses were analyzed in detail. The results of our study showed that a long preoperative stay was a risk factor for deep SSIs after both procedures. A dirty or contaminated wound and a serious systemic condition were risk factors for deep SSIs after total hip prostheses. If post-discharge surveillance was carried out, more SSIs were found, for total knee prostheses more than twice as many. Independent risk factors for SSIs after total hip prostheses were a contaminated/dirty wound and for total knee prostheses a short operation duration. The authors conclude that surveillance of surgical site infections following total hip and total knee prostheses revealed different risk factors for (deep) SSIs.

Adolescent↗
PubMedDate not supplied

Patient education for women being fitted for breast prostheses.

Women who undergo mastectomy or other types of breast surgery often will be fitted for breast prostheses for therapeutic weight replacement as well as cosmetic purposes. Nurses are instrumental in educating women about issues related to breast surgery and in helping to promote psychosocial adjustment to the diagnosis and subsequent treatment. Nurses often are involved in the referral process for breast prostheses. Prostheses and bras that fit properly can be very important in the recovery process and ultimately improve quality of life for cancer survivors. Unlike in the past, many choices are available today for women who opt to use breast prostheses. Prostheses come in different colors, shapes, and weights, and some adhere to the chest wall. Many options also are available for bras, camisoles, and swimsuits, which are helpful adjuncts to the fit of the prosthesis. The purpose of this article is to describe the fitting process and options currently available for breast prostheses. Nurses can use this information to inform women of available breast prostheses options and help prepare them for a fitting.

Breast↗
PubMed2004

Scanning electron microscope and energy dispersive X-ray spectrometry studies on the material surface of extruded Polycel ossicular prostheses.

BACKGROUND: The cause of ossicular prosthesis extrusion remains an issue of interest to many otologists. This study evaluated the change in material surfaces and chemical elements of extruded total ossicular replacement prostheses (TORPs) and partial ossicular replacement prostheses (PORPs). METHODS: A total of nine extruded Polycel ossicular prostheses (four TORPs, five PORPs) from nine patients was investigated using scanning electron microscope and energy dispersive X-ray spectrometry (EDX). Three prostheses (TORPs) obtained during revision surgery for hearing restoration were used as control subjects for EDX study. RESULTS: All subjects from the study group showed loss of fibrous capsule at both platform and shaft in the extruded prostheses. In comparison with the control group, the extruded prostheses had a lower level of carbon element (Wilcoxon signed-rank test, p < 0.05). CONCLUSION: Loss of fibrous capsule and micro-degradation are probably two of the many factors that contribute to the extrusion of ossicular prostheses.

Carbon↗
PubMed1992

Hydroxylapatite ossicular replacement prostheses: results in 157 consecutive cases.

The use of hydroxylapatite for ossicular chain reconstruction is increasing. In this study, hearing results and extrusion rate for 157 consecutive patients receiving hydroxylapatite prostheses were evaluated. Results were compared to those of a control group of patients who had received either homograft bone or Plasti-Pore prostheses. Four (2.6%) cases of extrusion have occurred. Hearing success was defined as a postoperative puretone average air-bone gap of < or = 15 dB for incus prostheses and partial ossicular replacement prostheses (PORPs) or < or = 25 dB for incus-stapes prostheses and total ossicular reconstruction prostheses (TORPs). Overall success rate in the hydroxylapatite group was 51.4% for the 140 patients with postoperative data (mean follow-up, 11.5 months) and 46.7% for 90 patients who were followed for more than 6 months (mean follow-up, 16 months). PORP results were significantly poorer than those of the other prostheses. The success rate for the control group was 58.6% for 58 patients. The difference between hydroxylapatite and control group success rates appears to be due to the poorer results of the hydroxylapatite PORP.

Adult↗
PubMed1989

Patency and durability of small diameter silicone rubber vascular prostheses.

This study evaluated the long-term patency and durability of 6 mm internal diameter (ID), 18-30 micron pore size replamineform silicone rubber vascular prostheses as canine aortic interposition and arteriovenous (A-V) grafts. Six prostheses (6 mm ID x 8 cm length) were evaluated as aortic grafts for 24 to 30 months, and 10 prostheses (6 mm ID x 8-10 cm length) were studied as A-V grafts from 2 weeks to 10 months. Three of the A-V prostheses were punctured for sham dialysis once or twice/week with two 16 gauge needles (total of approximately 50 needle punctures). The porous wall of the silicone rubber prostheses was incorporated with capillaries and fibrohistiocytic cellular elements from 2 weeks of implantation. This cellular incorporation remained constant up to 2 1/2 years. Needle puncture of the arteriovenous grafts over a 3 to 5 month period produced no complications such as thrombosis, perigraft hematoma formation or bleeding through the puncture site. The silicone rubber sealed the holes with no evidence of tearing. Explanted prostheses had no evidence of enlargement or false aneurysm formation. This study supports our hypothesis that Replamineform silicone rubber prostheses are hemocompatable and demonstrate long-term durability for dialysis access. Clinical evaluation of this graft is planned in the near future.

Animals↗
PubMed1999

Comparison of stapes prostheses: a retrospective analysis of individual audiometric results obtained after stapedotomy by implantation of a gold and a teflon piston.

PURPOSE: Evaluation of hearing results after implantation of a Teflon piston (type Causse; Xomed Surgical Products, Jacksonville, FL) and of a pure gold piston (K-piston; Heinz Kurz GmbH Medizintechnik, Dusslingen, Germany), both with a shaft diameter of 0.4 mm in cases of otosclerosis requiring stapedotomy. An important difference between both prostheses is the difference in mass: the gold piston is three times heavier than the Teflon piston. METHODS: Retrospective analyses were carried out of the presurgery and postsurgery audiologic results obtained after primary stapedotomy by implantation of 62 Teflon pistons and 66 gold pistons. The results were compared according to mean values of several audiometric parameters. Furthermore, individual audiometric results have been evaluated with the "Amsterdam Hearing Evaluation Plots" (AHEPs) as a method for visual presentation of hearing results from each operated ear. With this method, "unsuccessfully" and "successfully" inserted prostheses can be recognized easily and a more realistic comparison between prostheses is possible. RESULTS: It was found that in the overall group the heavier gold prosthesis gives a significantly larger gain in air-conductive hearing at 2 kHz (p < 0.05) and in the speech frequency range 0.5 to 2 kHz (p < 0.05). There were no significant intergroup differences with regard to change in bone-conduction and air-bone gaps. Analysis of the hearing results of the subgroup that included only the "successfully" implanted prostheses according to the criteria of the AHEPs had mainly consequences for improvement of air-conduction thresholds: none of the intergroup differences were statistically significant. CONCLUSIONS: For a fair comparison between prostheses, it is necessary to take only the prostheses into account that are inserted properly and that are functioning under normal conditions with regard to transmission of sound vibrations. After analysis of the hearing results of these "successfully" implanted prostheses, a trend was noticed that the heavier gold piston gives more gain in the low- and mid-frequency range and the light-weighted Teflon piston gives more gain in the high-frequency range, although none of the differences were significant.

Adolescent↗
PubMed1999

Aortic valve replacement with small-sized disc prostheses (medtronic hall).

BACKGROUND AND AIM OF THE STUDY: Several studies have demonstrated a worse performance of small prostheses in the narrow aortic root. However, modern low-profile mechanical prostheses have improved hemodynamic performance, are easy to implant, and have been used increasingly in elderly patients, where narrow roots are most frequently observed. We describe our experience in patients with aortic annuli >21 mm with the use of Medtronic Hall prostheses. METHODS: Between April 1988 and December 1997, a total of 332 patients (218 females, 114 males; mean age 59.3 +/- 9.8 years (range: 29-75 years) received Medtronic Hall size 20 (n = 140), 21 (n = 96) or 22 (n = 96) prostheses. The mean body surface area was 1.59 +/-0.12 m2 (range: 1.27-2.01 m2); 140 patients were in NYHA functional classes III/IV. There were no significant differences in clinical characteristics of patients in the three prosthesis-size groups. RESULTS: The mean preoperative systolic left ventricular/aorta gradient was 64.5 +/- 24.8 mmHg (no significant inter-group difference). After cardiopulmonary bypass, peak gradients through the aortic prostheses were 13.9 +/- 8.0 mmHg in size 20 valves, 14.0 +/- 8.1 mmHg in size 21, and 10.1 +/- 8.9 mmHg in size 22. Four patients died in hospital (mortality rate 1.2%); there were no significant inter-group differences in hospital morbidity. Follow up was complete for 97% of the patients (mean 4.3 years; range: 1-11 years). The late mortality rate was 9.3% (n = 31; 2.56% per pt-yr); of these patients, 20 (14.3%) had size 20 prostheses, seven (7.3%) size 21, and four (4.2%) size 22 (p = 0.01). Fourteen patients (4.2%) died from cardiac causes, and six (1.8%) from prosthesis-related causes. Preoperative older age and aortic regurgitation were the only independent predictors of late mortality. Eight patients had systemic thromboembolic events (0.66% per pt-yr), two had prosthetic thrombosis (0.17% per pt-yr) and five had hemorrhagic episodes (0.41% per pt-yr). Seven patients had prosthetic valve endocarditis (0.58% per pt-yr). Among survivors, 97% are currently in NYHA class I/II. CONCLUSIONS: The small (size 20, 21 and 22) Medtronic Hall prostheses have good hemodynamic performance and are an excellent option as valve substitutes in patients with narrow aortic roots.

Adult↗
PubMed2000

Vertical alignment axis for transtibial prostheses: a simplified alignment method.

BACKGROUND AND PURPOSE: To evaluate a simplified method of alignment for fitting a transtibial prosthesis known as the vertical alignment axis method. METHODS: We measured the relationship between the vertical projection of the prosthetic socket center (geometric center of the cross section of the transtibial prosthetic socket at the level of the patella tendon bar) and the alignment reference center (junction of the middle and posterior thirds of the longitudinal axis of the shoe) in 36 dynamically aligned transtibial prostheses. The prostheses were fabricated by students, and the fit (proper vs improper) was assessed by the faculty. RESULTS: The faculty members found 26 of the 36 prostheses to be properly fitted. The vertical projections of the socket centers of the properly-fitted prostheses were concentrated within a small area of the shoe tracing (a mean value of 1.3 mm medially and 6.4 mm anteriorly from the alignment reference center). Conversely, in the improperly-fitted prostheses, the vertical projections of the socket center were scattered well away from the alignment reference center; the mediolateral deviation was significantly greater for improperly-fitted prostheses than for those that were properly fitted (p < 0.001). CONCLUSIONS: These results demonstrate the usefulness of the vertical alignment axis procedure. This procedure may help clinicians to better understand the alignment of transtibial prostheses and gait deviations associated with improper prosthesis fit.

Adult↗
PubMed2001

Pre-load on oral implants after screw tightening fixed full prostheses: an in vivo study.

The fit of implant supported fixed prostheses is said to be of clinical concern because of the rigid fixation of an oral implant in its surrounding bone. The influence of the torque sequence of the set screws during fixation of implant supported fixed full prostheses on the final pre-load was investigated in vitro. No significant effect of the torque sequence of the set screws on the final pre-load was observed. The main objective of this study was to quantify and qualify the pre-load in vivo on implants supporting a fixed full prosthesis. This was performed when the prostheses were supported by all five or six implants and was repeated when the prostheses were supported by only four and three implants. A total of 13 patients with a fixed full implant supported prosthesis were selected. The existing abutments were changed for strain gauged abutments. After tightening the set screws with a torque of 10 N cm, the pre-load conditions were registered. The average (SEM) axial forces and bending moments in case of five or six, four and three supporting implants were 323 N (43 N), 346 N (59 N), 307 N (60 N) 21 N cm (3 N cm) and 21 N cm (2 N cm), 23 N cm (5 N cm), respectively. In addition, the pre-load was registered after fixation of a machined gold cylinder, as delivered by the manufacturer, on each of the supporting implants, representing the 'optimal fit' situation. The corresponding average (SEM) axial forces and bending moments in case of five or six, four and three supporting implants were 426 N (36 N), 405 N (40 N), 413 N (46 N) and 8 N cm (1 N cm), 8 N cm (1 N cm), 8 N cm (1 N cm), respectively. The induced axial forces after tightening the prostheses were significantly lower then after tightening the gold cylinder in case of five or six supporting implants (P < 0.02). The induced bending moments after tightening the prostheses were statistically significantly higher (P < 0.0001) then after tightening the gold cylinder in all test conditions (five or six, four or three supporting implants). This study underlines the static load present after screw tightening implant supported fixed full prostheses.

Adult↗
PubMed1991

Total knee arthroplasty in rheumatoid arthritis. A comparison of the polycentric and total condylar prostheses.

From 1971 to 1985, 393 total knee arthroplasties (TKAs) were performed in patients for rheumatoid arthritis. Of these, 112 used polycentric prostheses and 131 used total condylar prostheses. One hundred seven of the patients with polycentric prostheses and 102 of the patients with total condylar prostheses were followed for a minimum of two years (average, 61 and 55 months, respectively). At the time of the latest examination, nine knees with polycentric prostheses required revision surgery: six for tibial component loosening and instability and three for patellofemoral pain. Five knees with total condylar prostheses required revision: one for chronic instability, one for a late posttraumatic patellar fracture, and three for late hematogenous infections. The total condylar prostheses with patellar resurfacing had better scores for pain (8.5 points) than the polycentric prosthesis without patellofemoral resurfacing (7.0 points). The total condylar prosthesis appeared more durable in terms of fixation, with no evidence of aseptic loosening of femoral or tibial components noted in this series thus far.

Arthritis, Rheumatoid↗
PubMed1990

Prostheses and the forward reach of sitting lower-limb amputees.

The hypothesis that prostheses improve the forward reach of sitting lower-limb amputees was tested. While sitting with only ischial support, ten unilateral below-knee (BK) amputees could reach farther when they wore their prostheses than when they did not, when reaching at 45 degrees toward or away from the side of the amputation, with mean differences (+/- 1 SD) of 10.7cm (+/- 6.9, p less than 0.0001) and 4.4cm (+/- 4.1, p less than 0.01), respectively. With ten unilateral above-knee (AK) amputees, the differences were not statistically significant. Seven bilateral amputees (mixed levels) were able to reach farther with their prostheses on than off, with mean differences of 41.2cm (+/- 9.5) and 31.5cm (+/- 7.9) for reaches at 0 degrees and 45 degrees, respectively (p less than 0.0001). With the prostheses off, their reach was significantly greater when their thighs were supported than when they were sitting with only ischial support. These findings suggest that (1) prostheses improve the anterolateral reach of unilateral BK amputees, and the straight forward and anterolateral reach of bilateral amputees; (2) when prostheses are not being worn, a sitting surface which provides support through the residual limbs improves forward reach; and (3) the design of AK prostheses should reflect the patient's needs, both standing and sitting.

Adult↗
PubMedDate not supplied

Polish vascular prostheses.

Vascular prostheses have been manufactured in Poland since 1960. Double velour crimped tube and bifurcation prostheses are currently available under the Trade Mark Dallon. The Authors present and discuss 812 grafting procedures for the aorto-iliac occlusive disease with the use of 457 Polish and 355 foreign-made vascular prostheses. Wound infection occurred in 7% of the patients with implanted Polish prostheses and in 6.8% of the patients with implanted foreign-made vascular grafts. The acute thrombosis of the operated artery was similarly frequent in case of Polish and foreign-made prostheses implantation, 7% and 6.8% respectively. Haemorrhagic complications were more frequent in patients with implanted Polish prostheses (1.7%) than those with foreign-made vascular grafts (0.8%). Early results of the grafting procedures (6-month follow-up) were nearly the same in both groups and the results reported in the available literature. The Authors conclude that the Polish knitted vascular prostheses have properties similar to the foreign-made ones.

Adult↗
PubMed1985

[Biological studies of Gore-Tex vascular prostheses].

In 1981 we received the Gore-Tex PTFE vascular prostheses, 12 mm in diameter, in order to test their value. Experimental studies were carried out on 6 piglets, in which 5 cm long sections of the prostheses under study were grafted into surgical defects of the thoracic aorta. The dissections were made 1, 3, 6 months after grafting, each time detailed pathomorphological studies were carried out. The results show that PTFE prostheses, grafted into a piglet thoracic aorta was surrounded by fibrinous connective tissue. The tissue on the outside of the prostheses differs in histological structure from that inside. After 6 months it was found that the prosthesis has inside a thin layer of fibrinous connective tissue, connected to the prostheses wall; the layer did not constrict the internal diameter. The Gore-Tex prostheses fulfill biological requirements on vascular prostheses after their grafting into operational defects of the aorta.

Animals↗
PubMed1984

[Experimental studies of Dallon vascular prostheses after superficial alkaline hydrolysis].

Within the research on improving polyester vascular prostheses DALLON there was made a superficial alkaline hydrolysis in the manufactured product, which greatly enhanced the prostheses wettability without lowering their resistance parameters. In preliminary laboratory research and in biological studies in vitro, made with model prostheses and with those having been hydrolyzed, the results were better for hydrolized ones. Biological studies in vivo were made on piglets by implanting the prostheses into surgical defects of the thoracic aorta. In the course of the operations it was found that the prostheses were, apart from having better wettability, far more tight intraoperationally, as compared to the model ones. Pathomorphological studies, carried out 3 and 6 months after the operation, showed that, besides the hydrolized prostheses being less calcified, there were no significant qualitative and quantitative changes in the tissues around the implanted prostheses.

Animals↗
PubMed1984

Echocardiographic assessment of the subaortic root after implantation of high or low profile mitral prostheses.

In order to evaluate the influence of the profile of mitral prostheses on the outflow tract of the left ventricle, 99 patients underwent M-Mode echocardiography before and after surgery. In 67 cases high profile mitral prostheses had been implanted (48 mechanical and 19 biological); in 32 cases low profile mitral prostheses had been implanted (22 mechanical, 10 biological). Echocardiography showed that the implantation of high profile mitral prostheses did not induce changes of left ventricular diastolic and systolic dimensions ( EDDLV and ESDLV ) while induced significant reduction of left ventricular outflow tract (LVOT) dimension and LVOT/ EDDLV index with subsequent changes in transaortic flow. On the other hand, low profile prostheses did not induce significant changes of left ventricular dimensions, LVOT and LVOT/ EDDLV index. Finally, low profile biological mitral valve prostheses ( Liotta type) induced a significant increase of post-operative dimension of LVOT and LVOT/ EDDLV index. Authors conclude: that the implantation of high profile mitral prostheses changes LVOT dimension and transaortic flow and, that M-Mode echocardiography is a reliable technique to point out these changes.

Adult↗