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PubMed2006

[Accuracy of lens power calculation and centration of an aspheric intraocular lens].

BACKGROUND: Aspherical intraocular lenses (IOLs) are presumed to optimize the optical characteristics of IOLs. In order to profit from these characteristics, exact calculation of the IOL power and good centration of the lens are essential. METHODS: In all, 43 eyes of 43 patients with an average age of 70.9+/-8.3 years underwent implantation of a Tecnis IOL (AMO, Ettlingen) after uneventful cataract surgery with topical anesthesia. IOL power calculation was performed using the Holladay, Haigis, and SRK II formulas. Spherical equivalent refraction and centration and position of the implanted IOLs were measured 6 months postoperatively. Centration of the IOL was analyzed using digital slit lamp photographs and an image analysis program. RESULTS: Best corrected visual acuity (BCVA) increased from 0.47+/-0.25 (LogMAR) preoperatively to 0.1+/-0.11 6 months postoperatively (spherical equivalent +0.3+/-0.6 D). The intraindividual difference between target refraction and achieved postoperative refraction was 0.64+/-0.11 D for the Holladay formula, -0.21+/-0.11 D for the Haigis formula, and 0.97+/-0.15 D for the SRK II formula. The mean decentration of the IOL from the center of the corneal limbus was 0.4+/-0.1 mm. CONCLUSIONS: For the aspherical Tecnis IOL very good postoperative functional results are reported, which are supported by an accurate calculation of the IOL power and a good centration of the IOL inside the capsular bag. In this study the Haigis formula showed the lowest difference between target refraction and achieved postoperative refraction.

Aged↗
PubMed2004

Intraoperative cutting errors in total knee arthroplasty.

INTRODUCTION: Precise reconstruction of leg alignment offers the best opportunity for achieving good long-term results in total knee arthroplasty (TKA). It was the aim of this study to evaluate the bone-cutting process as a potential source of inaccuracy in TKA. MATERIALS AND METHODS: In a consecutive series of 50 computer-assisted TKAs, cutting errors, which were defined as a difference between the cutting block position before sawing and the achieved resection plane afterwards, were measured for the distal femur and proximal tibia resection. Measurements were performed using a CT-based navigation system. RESULTS: For the distal femoral cut, there was a mean varus/valgus deviation of 0.6 degrees (SD+/-0.5 degrees ) and a mean flexion/extension deviation of 1.4 degrees (SD+/-1.3 degrees ). For the proximal tibia, varus/valgus alignment showed a mean deviation of 0.5 degrees (SD+/-0.5 degrees ). The mean sagittal variability was 1.0 degrees (SD+/-0.9 degrees ). Differences between the frontal and the sagittal plane were significant. CONCLUSION: To minimize cutting errors, techniques and instruments are needed which enable a more stable fixation of the cutting blocks or even more appropriate preparation instruments. Using a computer-assisted technique, the surgeon is aware of cutting errors occurring at each point of the operation and will therefore be able to correct these errors during surgery, while he is not aware of those errors with the conventional TKA technique.

Adult↗
PubMed2001

An individualized approach for the implantation of a humeral prosthesis with the proper retroversion in fractures.

We applied a new methodology in 7 patients with a fracture of the upper humeral head that required hemiarthroplasty, to implant a humeral prosthesis with an individualized posterior version. Our goal was to determine preoperatively the distance from the posterior edge of the bicipital groove where the lateral fin of the humeral prosthesis should sit, in order to reproduce the individual retroversion during surgery. Using three computed tomography scan sections of the upper humerus and image processing software, we estimated the above-mentioned distance in the sound humerus and implanted the prosthesis in each patient accordingly. The differences in retroversion between the left and right humeral heads permit a better approximation to normal applying this methodology than inserting the prosthesis in a standard retroversion.

Humans↗
PubMed2006

Indication for the need of flexible and frequency specific mapping functions in cochlear implant speech processors.

Categorical loudness scaling of electric and acoustic stimuli was performed in cochlear implant (CI) recipients equipped with Nucleus systems in order to achieve a normal loudness perception in the whole dynamic range of acoustic input. For each electrode, the lower and upper limits of electric stimulus were defined by the values corresponding to "very soft" and "too loud". Within this dynamic range, the stimulus strength intervals associated to the verbal categories "soft", "medium", "loud" and "very loud" were determined. The same loudness categories were used for the scaling of acoustic stimuli. From both scaling experiments, the transduction of the CI system can be assessed and the parameters of the individual mapping function yielding a normal loudness growth can be derived. Deviations from optimum mapping can be corrected at least partially by manipulating the parameters of the mapping function. In many cases, however, one mapping function is not sufficient for all channels. The results argue in favour of the development of flexible and channel-specific mapping function parameters in future CI systems.

Cochlear Implants↗
PubMed1998

Epicutaneous breast forms. A new system promises to improve body image after mastectomy.

Mastectomies will remain a treatment alternative for breast cancer in spite of efforts to perform more breast-conserving treatment. Restoration of body symmetry may then be an important issue, which can be achieved by surgical breast reconstruction or with an epicutaneous breast prosthesis. A new improved system has recently been developed, which is self-adhesive to the thorax wall. In this study we investigated the advantages and disadvantages of the new system. The body image of 55 patients after unilateral mastectomy was assessed before they entered the study and after approximately 6 months of experience with the system. The "Frankfurter Körperkonzeptskalen" plus additional questions concerning problems after mastectomy and the handling of the new breast form were used for the assessment. About 50% of the patients had problems with the adhesiveness of the breast form, which remains a problem to be solved. Patients who suffered badly from mastectomy, have a smooth and plane mastectomy scar, and who were not suffering from hot flushes, which can impair the adhesiveness of the prosthesis, were more likely to profit from the new self-supporting breast forms. Significant differences were observed in the scales "self-acceptance of the body", acceptance of the body by others" for the subsets of patients mentioned above. The differences were less pronounced in patients who were already familiar with another type of epicutaneous breast form, which is attached to an adhesive plate on the thorax wall by nylon touch and close fasteners. Most (90.7%) of the patients would recommend this new type of breast prosthesis for other patients with mastectomy. The concept of self-supporting breast forms is an improvement with respect to social and psychological rehabilitation. According to the manufacturer, the problem with adhesion has meanwhile been solved.

Adult↗
PubMed2004

Clinical accuracy evaluation of femoral canal preparation using the ROBODOC system.

The purpose of this study was to evaluate the clinical accuracy of femoral canal preparation using postoperative reconstructed computed tomography (CT) images of 75 consecutive total hip arthroplasties performed with a two-pin-based ROBODOC system. Intraoperatively, the robot milled the femoral canal according to the preoperative planning performed with preoperative CT data and the ROBODOC workstation. Postoperative CT data was obtained 1 month postoperatively. Anteroposterior and lateral synthetic radiographs and axial images were reconstructed from CT data on the workstation. The mean difference between the preoperative planning and the postoperative CT images was less than 5% in canal fill, less than 1 mm in gap, and less than 1 degrees in the mediolateral and anteroposterior alignment. Clinical femoral canal preparation using the ROBODOC system results in a high degree of accuracy.

Adult↗
PubMed2006

[Evaluation of individual ceramic implants made of Bioverit with CAD/CAM technology to reconstruct multidimensional craniofacial defects of the human skull].

BACKGROUND: Restrictions in the bone structure of the craniomandibular region caused by malformation, traumata or malignant tumours are currently of interest in reconstructive oral and maxillofacial surgery. Methods of autologous bone transplantation are well established for reconstruction of those defects. The reconstruction and remodeling of contour-shaping defects is more difficult due to atrophy and resorption of free-transplantable tissues. Artificially induced harmful effects have been reported on harvesting in the donor area. Further available methods of alloplastic reconstruction are computer-assisted design and manufacturing systems (CAD/CAM). The advantages of individual design and fabrication are obvious in the manufacturing of defect-specific implants. MATERIAL AND METHODS: In the present study the application of individual CAD-based reconstructed bioceramic implants made of Bioverit II was evaluated in the region of the facial skull. Clinical results, patient acceptance and the analysis of the postoperative observation period of 30 months are reviewed. RESULTS: Altogether 25 individual Bioverit ceramics were implanted in the facial region. All patients were satisfied with the aesthetic results of the implantations after primary surgery. Three patients developed a need for further correction during the observation period; one implant fracture was observed. CONCLUSION: Finally, it can be stated that the preoperative expenditures in time, experts, technology and fabrication of individual CAD/CAM planned and manufactured implants are justified by the following advantages: fixed volume, reduced operating time, lack of donor morbidity, easy subsequent treatment of the material and the aesthetic results achieved.

Adult↗
PubMed2001

[Management of craniofacial bone defects with individually prefabricated titanium implants. Follow-up and evaluation of 78 patients with 78 titanium implants 1994-1998].

STUDY: From 1994 to 1998, 78 prefabricated titanium implants were used for the reconstruction of large and complex cranial and craniofacial defects in 76 patients at 19 European centres. After a mean follow-up of 8 months, a clinical and radiological examination was used to determine the results of the reconstruction and the patients' satisfaction. Using a standardized questionnaire patients were also able to comment, subjectively, on improvements or alterations after the insertion of the implant. RESULTS: Two implants were removed after an early infectious complication and in a another two cases the implants were removed in order to obtain a tissue sample for histological examination. All other patients showed constant good to excellent clinical and radiological findings with high patient satisfaction. DISCUSSION: The use of titanium fulfils the highest demands of biocompatibility while at the same time allowing the possibility of an oncological examination using suitable turbo-spinecho-sequences in MRI.

Adolescent↗
PubMed2005

AneuRx device migration: incidence, risk factors, and consequences.

Success after endovascular abdominal aortic aneurysm repair (EVAR) is dependent on device positional stability. The quest for such stability has motivated different endograft designs, and the risk factors entailed remain the subject of debate. This study aims at defining the incidence, risk factors, and clinical implications of device migration after EVAR with the AneuRx endograft. In this study we included all consecutive 109 patients submitted to primary AneuRx placement for infrarenal aortic or aortoiliac aneurysms. Preoperative computed tomography (CT) scans were reviewed for the following anatomic characteristics: neck length, diameter, angulation, calcification, and thrombus load; and sac diameter and thrombus load. Percentage of device oversizing relative to the proximal neck diameter was determined. All postoperative CT scans were reviewed, and the distance between the lowest renal artery and the craniad end of the device was measured. A >/=5-mm increase in such distance was considered indicative of device migration. Migration cumulative incidence was estimated by the Kaplan-Meier method, and its association with any of the preoperative anatomical characteristics was tested using Cox proportional hazards models. Median follow-up time was 9 (range, 1-31) months. Migration occurred in nine patients, corresponding to a 15.6% estimated probability of migration at 30 months (SE = 5.1%). Migration was associated with the risk of proximal type I endoleak (hazard ratio = 3.39, 95% confidence interval = 1.46-7.87; p = 0.007). This type of endoleak occurred in three of the migration-affected patients (33.3%); all of them were resolved by additional cuff placement at the proximal landing zone. No other migration-related reinterventions were performed. The only significant associations between anatomic factors and device migration probability were the protective effects of longer necks (odds ratio [OR] = 0.71 for each additional 5 mm, p = 0.045) and longer overlapped portions of neck and device (OR = 0.56 for each additional 5 mm, p = 0.003). There was a trend toward higher probability of migration among reverse-tapered necks (OR = 1.75, p = 0.109). Percentage of device oversizing correlated with early neck dilation (between preoperative and first postoperative diameters, correlation coefficient = 0.4, p < 0.0001), but not with late neck dilatation (between first postoperative and 1.5-year scan diameters, correlation coefficient = 0.29, p = 0.112). There was a trend toward higher mean percentage of late dilation among migrators (11.4%, standard error of the mean [SEM] 2.6) than nonmigrators (5.7%, SEM = 1) (p = 0.08), but both groups had similar mean percentages of early dilation (3%, SEM = 1.6%, vs. 5.5%, SEM = 0.6%; p = 0.365). This result indicates that device migration is not a rare event after AneuRx implantation. This phenomenon is associated with proximal type I endoleaks. Deployment of the endograft immediately below the renal arteries might help to prevent migration, since use of greater lengths of overlapped device relative to the proximal neck has a protective effect. Migration seems to be independent of the degree of device oversizing.

Aged↗
PubMed2006

Correlation between the measurement of transverse diameter in the proximal neck on computed tomography and on aortography before endovascular treatment of infrarenal aortic aneurysm.

The aim of this study was to determine the correlation between the measurement of transverse diameter of the proximal neck on computed tomographic angiography (CTA) and graduated catheter aortography in patients who are candidates for endovascular graft placement in order to replace, if both measurements are equivalent, aortography for CTA alone. Preoperative dual-slice CTA and graduated catheter aortography were performed in 35 consecutive patients with infrarenal aortic aneurysm within 10 days. Transverse proximal neck diameters were measured on a true axial section on CTA reconstructions and on aortographic images, always 6 mm distal from the most inferior main renal artery. Mean, median, and standard deviation were obtained and the measurements correlated for each patient using Pearson's correlation and linear regression analysis. A significant difference in proximal neck transverse diameter measurements was found between graduated catheter aortography and CTA in all cases. CTA values were a mean of 1.74 mm higher than aortography values. Pearson's correlation indicates a strong correlation between both techniques, and a regression equation determines the predictive value of aortography on the basis of CTA values. Estimation of the transverse diameter of the proximal neck on aortography on the basis of that obtained on CTA allows us to affirm that CTA could be used as the sole method for the preoperative selection of appropriate endograft size in patients with infrarenal aortic aneurysm.

Angioplasty, Balloon↗
PubMed1998

Mechanics of end-to-end artery-to-PTFE graft anastomoses.

On some occasions vascular surgeons are called upon to construct an end-to-end anastomosis using prosthetic graft material. If a spatulated anastomosis is not fashioned, three important variables that are under the surgeon's control could affect anastomotic dimensions: (1) selection of graft material, (2) graft size relative to the native vessel, and (3) suture technique. Accordingly, studies were performed on 36 nonspatulated, end-to-end artery-to-polytetrafluoroethylene (PTFE) grafts to evaluate the effects of graft size and suture technique on anastomotic dimensions. Size-matched (3 mm) and slightly oversized (4 mm) grafts were anastomosed end-to-end to 3 mm pig carotid arteries using (1) running polypropylene (Surgilene) sutures, (2) running polybutester (Novafil) sutures, or (3) interrupted sutures. After 30 min the vessels were excised, filled with contrast material, and radiographs were obtained to measure anastomotic dimensions. Results showed that, at every comparable pressure, 4 mm grafts produced larger anastomoses than did 3 mm grafts. In addition 4 mm grafts produced smoother anastomoses without a constricted or "pinched" appearance at the graft-artery junction. Marked compliance mismatch was observed with both sized grafts. There was no significant difference in the dimensions of the anastomoses or compliance mismatch with the three different suture techniques. These studies indicate that, when using PTFE grafts for end-to-end anastomoses, a graft that is slightly larger than the artery is preferable to provide the largest and smoothest anastomosis, and that any of the three suture techniques may be used.

Anastomosis, Surgical↗
PubMed2000

The value of intraoperative intravascular ultrasound for determining stent graft size (excluding abdominal aortic aneurysm) with a modular system.

Since the introduction of endovascular stent grafts at our institution we have used intraoperative intravascular ultrasound (IVUS) to definitively determine stent graft size. In this study, expected stent graft size, based on preoperative helical CT scan measurements, was compared with the actual final size, based on intraoperative IVUS measurements. Between December 1996 and January 1998, 54 patients were treated with an AneuRxTM bifurcated stent graft. Preoperatively all patients underwent angiography and helical CT scanning. Expected stent graft size was determined according to these measurements. The final stent graft size was based on IVUS measurements acquired during the procedure. Differences in expected and final size were compared and follow-up endoleaks were also noted. Differences in diameter measurements between CT and IVUS were compared using the paired Student's t-test. Differences in expected and chosen stent graft length were compared using the McNemar's test for paired proportions of binomial outcomes. Our results showed that helical CT scanning overestimates diameter and underestimates length. This underestimation of length is explained by the tortuosity of the aorta and iliac arteries while using axial slices of the CT scan. The last-minute corrections based on the intraoperative IVUS measurements did not result in a high incidence of endoleaks at fixation zones. In our opinion, the possibility of making final corrections in the choice of diameter or length of the stent graft is the additional value of intraoperative IVUS.

Aortic Aneurysm, Abdominal↗
PubMedDate not supplied

Ocular discomfort at the initial wearing of rigid gas permeable contact lenses.

PURPOSE: To evaluate the relationship between ocular discomfort in the initial wearing of rigid gas permeable contact lenses (RGPCL) and the time required to adapt to RGPCL as measured by using the visual analogue scale (VAS). METHODS: RGPCL were prescribed for 89 patients (178 eyes) with myopia or myopic astigmatism and no history of wearing contact lenses. The patients who stopped wearing RGPCL after 1 week because of ocular discomfort were defined as dropouts, and those who adapted to regular full-time RGPCL wear were defined as successful wearers. VAS scores were measured at several intervals for 1 month after the initial wearing of the lenses. The number of days required to adapt to wearing RGPCL was defined as the adaptation time. RESULTS: Four patients were dropouts due to ocular discomfort (eight eyes; 4.5%). VAS scores were significantly lower in successful wearers than in dropouts at 1 week, although their VAS scores were not different at 1 day. VAS scores of the successful wearers at 1 week were significantly lower than those at 1 day. The average time required to adapt to RGPCL was 23.0 +/- 22.1 days for the 85 successful wearers. Lower VAS scores at 1 day or 1 week were significantly correlated with a shorter adaptation time in the successful RGPCL wearers. CONCLUSIONS: Our results indicate that the VAS score might be useful for predicting successful RGPCL use and the adaptation time required by successful wearers.

Adaptation, Ocular↗
PubMed2002

[In situ connection of a hollow intramedullary nail to the stem of a knee prosthesis in periprosthetic fracture].

Periprosthetic fractures often reveal problems and complications because of poor bone quality. A case report is presented, in which a hollow intramedullary nail was connected, in situ, with the stem of a knee prosthesis (Blauth knee). Two plate osteosyntheses had previously failed. As ultima ratio, a hollow intramedullary nail was placed antegrade on the stem of the knee prosthesis. Afterwards excellent callus formation developed and resulted in consolidation.

Aged↗
PubMed2002

[What influence do size and placement of patella resurfacing have on knee endoprosthesis?].

The aim of this study was to document the changes in retropatellar pressure, contact area and forces due to different sizes and placement of the patella resurfacing in knee arthroplasty. Six cadaver specimens (after Thiel fixation) were examined after the implantation of the total knee arthroplasty Genesis I. The patella sizes "small" and "medium" were placed as the "onlay" version, centered as well as off-centered by 0.4 cm in all four directions. Pressure and area measurements were done with Fuji pressure measuring film, which was placed between the patellar fascia of the femur and the patella in a defined position. The pressure was measured by applying a predetermined force for 5 s. The examinations were done with 60 degrees knee flexion and a force of 280 N. In our results there were no significant differences between, patella sizes. No significant differences for the medial, distal and proximal placement were found for the small patella. The lateral placement led to a significant decrease in the contact area (P = 0.0277), maximum pressure (P = 0.0422) and force (P = 0.0277). The average pressure did not change significantly (P = 0.1159). For the medium size patella there were no significant differences for medial or distal placement. The comparison of lateral and central placement revealed a significant decrease in the contact area (P = 0.0446). Comparing distal and proximal positioning, a significant increase in contact area and significant decrease in force were found (P = 0.0277 and P = 0.0277 respectively). In conclusion, the choice of small or medium patella resurfacing does not seem to have a significant influence. In comparison to the results without patella implants, the implantation of the small patella caused a significant decrease in the retropatellar contact area (P = 0.03) and force (P = 0.03). Average and maximum pressure did not change significantly (P = 0.6 and P = 0.35) even though pressure increased slightly. For the medium size, maximum pressure (P = 0.03) increased significantly and force decreased significantly (P = 0.0277) whereas contact area and average pressure increased slightly. The results of the different placements of the patella implant do not support the recommendation for a medial shift. However, at least the lateralized implantation led to a reduction of contact area and force as well as to a slight increase of pressure which is considered as unfavorable.

Aged↗
PubMed1993

Transthoracic and transesophageal echocardiographic sizing of the aortic annulus to determine prosthesis size.

To assess the accuracy of 2-dimensional echocardiography versus transesophageal echocardiography (TEE) in predicting aortic annulus diameter, and to determine which part of the cardiac cycle should be used for measuring the size of the aortic valve prosthesis in patients undergoing aortic valve replacement, the aortic annulus was measured retrospectively in a blinded fashion in a group of 94 patients who had undergone aortic valve replacement: 66 had preoperative transthoracic echocardiography (TTE), 69 had intraoperative TEE, and 41 had both. Accuracy of measurements was calculated by the mean biases (differences between annular size by echo and actual valve size chosen by intraoperative mechanical sizing of the aortic annulus). TTE was compared with TEE and end-diastolic (ED) measurements with end-systolic (ES) measurements. The mean biases +/- SD were -1.7 +/- 3.4 mm by TTE-ES versus -0.9 +/- 3.5 mm by TEE-ES measurements (p = NS), and +0.03 +/- 3 mm by TTE-ED versus +0.5 +/- 2.8 mm by TEE-ED (p = NS). Examination of the magnitudes of the biases gave the same result. ED measurements were found to have a smaller amount of bias than ES measurements, both by TTE and by TEE: -1.7 +/- 3.4 mm by TTE-ES versus +0.03 +/- 3 mm by TTE-ED (p = 0.0001) and -0.9 +/- 3.5 mm by TEE-ES versus +0.5 +/- 2.8 mm by TEE-ED (p = 0.0001). Examination of the magnitudes of the biases also gave the same result.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1985

Metal minibases in removable prosthodontics.

A description of the designs and indications for minibases in removable prosthodontics has been presented. Minibases can solve complicated space problems when surgery is contraindicated by providing a strong, thin, abrasive-resistant denture base. The result of their correct use is a prosthesis that fits well, is extended correctly, functions without opposing interferences at the correct vertical dimension of occlusion, and resists the functional stresses placed on it during service.

Dental Alloys↗
PubMed1993

Transmolar pin and magnetic carrier for midfacial reconstruction: a clinical report.

With previous prosthetic restorations of bilateral maxillary resections, tissue erosion and bleeding on the cephalic parts of the cavity have been caused by movement and pressure from the prosthesis. Retention of a prosthesis is a major determinant in its successful use. Physical and psychologic stresses are common when one is unable to use a prosthesis comfortably. The use of a musculocutaneous flap and an obturator prosthesis had provided near-immediate reconstruction of a massive midfacial defect. This method of reconstruction resulted in soft tissue replacement for appearance and functional rehabilitation of the upper lip while maintaining sound oncologic principles.

Adult↗