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At least 181 records · Page 10Linked to original sources
PubMed2003

Muscle activation pattern and gait biomechanics after total knee replacement.

OBJECTIVE: The aim of this study is to evaluate residual muscle function abnormalities after total knee replacement, with respect to gait kinematics and kinetics. DESIGN: Longitudinal study on a follow-up of up to two years. BACKGROUND: Gait usually presents an excellent improvement after total knee replacement. Nevertheless, some kinematics and kinetics abnormalities persist even after a long period of time and they might have implications in long-term prosthesis failure. Additionally, lower limb muscle activity has not been sufficiently studied in the past directly by means of dynamic EMG. METHODS: Nine patients who had a posterior cruciate sparing total knee replacement design were evaluated by means of clinical assessment and gait analysis at the end of rehabilitation trials at six, twelve and twenty four months. EMG from trunk and lower limb muscles was registered and elaborated through a statistical detector for the on-off timing. RESULTS: Gait analysis showed a slow gait, with a "stiff knee gait pattern" and prolonged muscular co-contractions during stance. CONCLUSIONS: Knee kinematics and kinetics abnormalities during loading acceptance after total knee replacement are associated with co-contractions in muscular activation pattern. RELEVANCE: Gait pattern at two years after total knee replacement is deemed unphysiological, potentially dangerous for the implant duration in time and responsible for residual disability in patients. Muscular behavior during daily activities provides insight into the integration of the prosthetic biomechanics within the muscular-skeletal system. This information is of relevance to improve prosthetic design, rehabilitation programs and knee motor performance.

Aged↗
PubMed1999

Determination of the optimal elbow axis for evaluation of placement of prostheses.

OBJECTIVE: To present a method to determine the position and orientation of the mean optimal flexion axis of the elbow in vivo to be used in clinical research. DESIGN: Registering the movements of the forearm with respect to the upper arm during five cycles of flexion and extension of the elbow using a 6 degrees-of-freedom electromagnetic tracking device. BACKGROUND: Loosening of elbow endoprostheses could be caused by not placing the prostheses in a biomechanically optimal way. To evaluate the placement of endoprostheses with regard to loosening, a method to determine the elbow axis is needed. METHODS: The movements of the right forearm with respect to the upper arm during flexion and extension were registered with a 6 degrees-of-freedom electromagnetic tracking device. A mean optimal instantaneous helical axis of 10 elbows was calculated in a coordinate system related to the humerus. RESULTS: The average position of the flexion/extension axis was 0.81 cm (SD 0.66 cm) cranially and 1.86 cm (SD 0.72 cm) ventrally of the epicondylus lateralis. The average angle with the frontal plane was 15.3 degrees (SD 2 degrees). CONCLUSIONS: A useful estimation of the position and orientation of a mean optimal flexion axis can be obtained in vivo.

Adult↗
PubMed1993

A comparison of microscrew and suture fixation for porous high-density polyethylene orbital floor implants.

Twenty oral and maxillofacial surgeons compared the surgical features of microscrew fixation technique with a suture technique for fixation of porous high-density polyethylene orbital floor implants. One investigator then compared material features of these two fixation techniques using recently procured bovine ribs. The microscrew technique was found to be quicker (P > .01) and easier (P > .001), and it provided a higher quality of fixation (P > .001) than the suture technique. The microscrew/implant system had a greater pullout strength (P > .001) and shear strength (P > .001) than the suture/implant system.

Animals↗
PubMed2000

Hemodynamic and clinical impact of prosthesis-patient mismatch in the aortic valve position and its prevention.

Prosthesis-patient mismatch is present when the effective orifice area of the inserted prosthetic valve is less than that of a normal human valve. This is a frequent problem in patients undergoing aortic valve replacement, and its main hemodynamic consequence is the generation of high transvalvular gradients through normally functioning prosthetic valves. The purposes of this report are to present an update on the concept of aortic prosthesis-patient mismatch and to review the present knowledge with regard to its impact on hemodynamic status, functional capacity, morbidity and mortality. Also, we propose a simple approach for the prevention and clinical management of this phenomenon because it can be largely avoided if certain simple factors are taken into consideration before the operation.

Aortic Valve Stenosis↗
PubMed2000

The management of severe acetabular bone loss using structural allograft and acetabular reinforcement devices.

The cases of 37 acetabular reconstructions in 35 patients with major structural pelvic bone loss were reviewed. At an average follow-up of 7.1 years, patients rated their results as excellent in 12 cases (32.4%), good in 22 (59.5%), fair in 2 (5.4%), and poor in 1 (2.7%). Thirty-four cases (91.9%) were classified as a clinical success. Thirty-six allografts (97.3%) had radiographic evidence of full incorporation. Of the unrevised hips, 1 (2.7%) was classified as definitely loose, 2 (5.4%) as probably loose, and 4 (10.8%) as possibly loose. One revision of an acetabular component was required because of late sepsis. This is the first reported series on the use of acetabular reinforcement devices with solid bulk allograft covering more than 50% of the socket. The allograft is protected in the early postoperative period, superior migration of the cup is virtually eliminated as a complication, and the incidence of aseptic loosening is greatly diminished.

Acetabulum↗
PubMed2003

Symmetrical vs asymmetrical total knee replacement--a medium term comparative analysis.

Modifications of established implants can result in deleterious effects, as with the Capitol and the matt coated Exeter hips. In 1991 the Kinemax plus modification of the Kinematic knee was introduced in Bristol, the design changes having been made to reduce patello-femoral complications. We carried out a comparative analysis of the prospective recorded data on a consecutive series of 182 total knee replacements (95 Kinematic and 87 Kinemax plus knees) performed between 1991 and 1993. The same instrumentation and surgical technique was used. Since the design had introduced a broader trochlear, offset patella and had changed from an asymmetrical to a symmetrical femoral component, particular attention was paid to tracking and range of movement. All patients were reviewed at 5 years using the Bristol knee score and radiographs. There was no difference in the overall score (both prosthesis scoring 85-86) but the Kinemax plus group with a symmetrical trochlear had a significantly greater improvement in the range of movement (14 degrees as opposed to 4 degrees; P<0.05). In addition, secondary intervention for mal-tracking was significantly less in the Kinemax group. No deleterious effect of the changed geometry was observed. It is concluded that the introduction of a symmetrical femoral component with an offset patella reduced patello-femoral complications without detectable disadvantages.

Aged↗
PubMedDate not supplied

Does keel size, the use of screws, and the use of bone cement affect fixation of a metal glenoid implant?

The objective of this study was to determine the effect of screws and keel size on the fixation of an all-metal glenoid component. A prototype stainless-steel glenoid component was designed and implanted in 10 cadaveric scapulae. A testing apparatus capable of producing a loading vector at various angles, magnitudes, and directions was used. The independent variables included six directions and three angles of joint load, and five fixation modalities-three different-sized cross-keels (small, medium, and large), screws, and bone cement. Implant micromotion relative to bone was measured by four displacement transducers at the superior, inferior, anterior, and posterior sites. The components displayed a consistent response to loading of ipsilateral compression and contralateral distraction. Use of progressively larger keels did not significantly improve implant stability. Stability decreased as the angle of load application increased (P <.05). Screw and cement fixation resulted in the most stable fixation (P <.05).

Arthroplasty↗
PubMedDate not supplied

Fixation of humeral prostheses and axial micromotion.

Surgeons often avoid cementing a proximal humeral prosthesis. Occasionally bony augmentation is needed. This study was undertaken to compare proximal cementation in combination with distal press with total cementation or press fit alone. In phase 1 axial micromotion with axial loading was measured in 15 pairs of humeri: 5 fully cemented versus proximally cemented, 5 fully cemented versus press fit, and 5 proximally cemented versus press fit. X-ray films of the specimens were obtained to assess canal fill. In phase 2 axial micromotion was measured in 5 pairs of high mineral density and 5 pairs of low mineral density to compare proximal cementation with press fit. The 3 M modular prosthesis was used in both phases. No difference was found in phase 1 among the 3 fixation techniques. A strong reverse statistical correlation (P = .007) (r = .55) was seen between axial micromotion and fill of the canal with the prosthesis. In the second phase no statistically significant difference was found between the techniques of fixation or between the 2 bone densities. Fill of the canal at the distal end of the prosthesis was the only variable found that affected axial micromotion, but it accounted for only approximately 30% of the variance. Bone quality and augmentation of the proximal bone with cement did not affect axial micromotion in this experiment but warrant further study.

Bone Cements↗
PubMedDate not supplied

Prosthetic adaptability: a new concept for shoulder arthroplasty.

An anatomic study of 65 cadaveric humeri allowed determination of the main features of the superior part of the humerus and design of a modular and adaptable humeral prosthesis. This cemented prosthesis is made in 3 different stem sizes, 7 humeral head sizes, and a variable humeral neck component. The 4 different humeral necks (125 degrees, 130 degrees, 135 degrees, and 140 degrees) allow the head to be cut at the level of the anatomic neck and adaptation of the prosthesis to the patient's anatomy with respect to the variable inclination and retroversion. An eccentric dial is located on the undersurface of the head; 8 positions are possible reproducing the posterior and medial offset of the humeral head with regard to the diaphysis. The large variety of components used for the first 101 implanted prostheses confirm the extreme variability of the anatomy and the need for a flexible shoulder prosthesis system. The glenoid component is made of polyethylene and is available in 3 different sizes to be used with a cemented keel. Eighty-six shoulders, which were monitored from 24 to 65 months, were evaluated with the Constant score. Primary glenohumeral arthritis (46 cases) and avascular necrosis (11 cases) yielded the best results, with scores of 95% and 86%. Rheumatoid arthritis (20 cases) scored 78%, although post-traumatic arthritis (11 cases) and cuff tear arthropathy (13 cases) had a less satisfactory result: 66% and 61%, respectively. Radiologic results showed 2 glenoids loosening and 48% of glenoids with radiolucent lines, with half of them being partial. An 8% complication rate has been observed, leading to 6 revisions (6%), in 2 cases for infection, 2 cases for secondary rupture of the subscapularis, and 2 cases for glenoid loosening.

Adult↗
PubMedDate not supplied

Artificial intervertebral discs and beyond: a North American Spine Society Annual Meeting symposium.

BACKGROUND CONTENT: This is a synopsis of a symposium presented to the North American Spine Society Annual Meeting in Seattle, WA, 2001. PURPOSE: To bring to the reader who may not have attended the symposium a distillation of the material presented on this frontier of spinal surgery. METHODS: Panel presentation. RESULTS: The proposed indication for artificial disc replacement is a degenerated but contained disc, painful to the point of major life-style interruption, refractory to at least 1 year of nonoperative treatment, preferably at a single lumbar level and without infection, listhesis or major facet joint disease or spinal stenosis. Total disc replacements have been developed and used mostly in Europe. Disc nucleus replacements have also been developed. No disc replacement has been approved for general use in North America as yet. The US Food and Drug Administration is conducting investigational device exemption studies at this time. CONCLUSIONS: Artificial disc replacement is not a new concept, the first attempts having been done in the early 1950s. During the past 15 years, considerable advance has been made with large numbers of patients, mostly in Europe, having surgery with either total disc prostheses or disc nucleus replacements. Only with truly scientific studies using patient randomization, pre- and postsurgery outcome analyses by unbiased independent observers and statistical analysis by independent experts will the real value of these devices be realized.

Biocompatible Materials↗
PubMed1992

An apparatus to measure pressure, flow and speech parameters in patients producing speech using the Groningen valve prosthesis.

We present a validated method of determining in vivo pressure, flow and voice parameters from patients using tracheo-oesophageal voice prostheses post laryngectomy. This apparatus was constructed simply using equipment which should be available in most large Otolaryngology Departments. There was good agreement between measurements made over two separate sessions of in vivo opening pressure, maximum flow through the device and maximum voice amplitude and these were significant. These measurements may be useful in monitoring patient progress and also in elucidating the mechanics of prosthesis failure.

Airway Resistance↗
PubMed2003

Minimally invasive repair of pectus excavatum (MIRPE)--the Basel experience.

PURPOSE: Minimally invasive repair of pectus excavatum (MIRPE) was first reported in 1998 by D. Nuss. This technique has gained wide acceptance during the last 4-5 years. In the meantime, some modifications of the technique have been introduced by different authors. Our retrospective study reports our own experience over the last 36 months and modifications introduced due to a number of complications. METHODS: From 3/2000 to 3/2003, 22 patients underwent MIRPE. Patients median age was 15.5 years (10.7 to 20.3 years). Standardised preoperative evaluation included 3D computerised tomography (CT) scan, pulmonary function tests, cardiac evaluation with electrocardiogram and echocardiography, and photo documentation. Indications for operation included at least two of the following: Haller CT index > 3.2, restrictive lung disease, cardiac compression, progression of the deformity and severe psychological alterations. RESULTS: In 22 patients (2 girls, 20 boys) undergoing MIRPE procedure, a single bar was used in 21 patients and two bars in one boy. Lateral stabilisers were fixed with non resorbable sutures on both sides. Overall, postoperative complications occurred in six patients (27.3%). In two patients (9.1%) a redo-procedure was necessary due to bar displacement. An additional median skin incision was performed in two patients to elevate the sternum. Pneumothorax or hematothorax in two patients resulted in routine use of a chest tube on both sides. Long-term favourable results were noted in all patients. CONCLUSIONS: The MIRPE procedure is an effective method with elegant cosmetic results. Modifications of the original method help to decrease the complication rate and to accelerate acquirement of expertise.

Adolescent↗
PubMed1995

Accuracy of implant-supported prostheses in the edentulous jaw: analysis of precision of fit between cast gold-alloy frameworks and master casts by means of a three-dimensional photogrammetric technique.

Distortions of 15 routine implant-supported prostheses were measured in relation to the master casts after completion by means of a 3-dimensional (3-D) photogrammetric technique. All prostheses were designed as one-piece gold-alloy castings with resin teeth. Five of the prostheses were placed in the edentulous maxilla, and the remaining were placed in the lower jaw. Distortion of the cylinders was mostly observed in the horizontal plane (x- and y-axis) while the vertical aspect seemed to be more stable. The mean 3-D center point distortion was 42 (SD 15) and 74 (SD 38) microns for the upper and lower jaws, respectively. The measurements revealed a range of 3-D center point distortion from 16 to 80 and 15 to 165 microns for the different jaws, respectively. The corresponding 3-D mean angular distortion of the cylinders was 51 (SD 35) microns in lower and 70 (SD 75) microns in the upper jaws. A correlation was found between 3-D center point distortion and the width as well as the curvature of the implant arch, indicating more displacement the wider and the more curved the arch was. The 3-D center point distortion was also significantly higher in the upper jaws which could possibly be explained by the curvature of the implant arch and higher numbers of implants in the upper jaws. Further problems with the fit of upper jaw castings could be related to more alloy in the castings and poor alignment of implants.

Dental Prosthesis Design↗
PubMed1998

A study of the hydroxyapatite orbital implant drilling procedure.

PURPOSE: The hydroxyapatite orbital implant has been introduced as a buried, integrated implant for use in the anophthalmic patient. The second stage of the procedure involves drilling the implant and inserting a motility peg that allows direct coupling of the artificial eye to the implant. Other authors have advocated an assessment of implant vascularity by imaging prior to drilling. We aimed to see whether our practice of drilling after a predetermined time interval without assessment of implant vascularity would result in a higher complication rate. We also aimed to determine how successful the drilling procedure was in improving both the motility and the stability of the artificial eye. METHODS: The notes of 41 consecutive patients who underwent drilling were studied to determine the time interval between implantation with a hydroxyapatite sphere and drilling, the nature of any complications and any further surgical procedures undertaken. A postal questionnaire was sent to all patients asking them to grade the motility of their implant before and after drilling, and to state whether or not there had been any improvement in the stability of their artificial eye. RESULTS: The most frequent complication encountered was extrusion of the motility peg, which occurred in 3 patients. A total of 5 patients required redrilling. There was an 80% response rate to the questionnaire. Ninety-one per cent of patients felt that there had been an improvement in the motility of their artificial eye and 76% felt that the stability of their artificial eye had been improved. CONCLUSION: Pegging of the hydroxyapatite implant improves both the motility and the stability of the artificial eye in the majority of cases. Complications are infrequent and minor. If sufficient time is allowed after implantation for full implant vascularity to occur, it is not necessary to perform imaging studies. This practice does not result in an increase in complications, and significantly reduces the expense of the procedure.

Adolescent↗
PubMed2005

Primary placement of a titanium sleeve in hydroxyapatite orbital implants.

BACKGROUND: To study a new surgical option of primary placement of a titanium sleeve into hydroxyapatite implants during enucleation or evisceration. METHODS: A standard enucleation or cornea preserved evisceration was performed, followed by preplacement of a titanium sleeve into the hydroxyapatite implant by a hand drill sleeve driver. Care must be taken to ensure that the titanium sleeve is positioned centrally when the implant is put inside the orbital socket or eviscerated shell. The Tenon capsule and conjunctiva were meticulously closed with minimal tension. Complications such as sleeve exposure, coralline exposure, and infection of the titanium sleeve were closely observed. RESULTS: In all, 30 patients were treated in the above fashion with 10 enucleation and 20 evisceration procedures. The follow-up period ranged from 9 to 24 months. Three of the sleeves were found to have exposed spontaneously at 5 and 7 weeks following original surgery. They had no further complication except one sleeve loosening. The remaining 27 sleeves that did not spontaneously expose pursued secondary exposure of the titanium sleeve and peg insertion by conjunctival cutdown procedure 3 months after original surgery. Two sleeves were found to be oblique positioned after the conjunctival cutdown procedure. Fortunately, all the 30 patients were successfully fit with a peg-coupled prosthesis with good motility. CONCLUSION: Primary placement of a titanium sleeve into hydroxyapatite implants has several advantages, including high patient acceptance, technical simplicity, and office-based conjunctival cutdown pegging procedure. By avoiding the expense of postoperative imaging study and additional prosthetic modification, a more rapid and efficient rehabilitation is possible.

Adult↗
PubMed1998

The VoiceMaster voice prosthesis for the laryngectomized patient.

Since the introduction and performance of total laryngectomy, voice restoration has become an important issue. Voice prostheses are widely used for this purpose. Based on experience with previous and current prostheses, the important characteristics for any voice prosthesis can be defined. These characteristics are: indwelling fixation, low resistance to airflow, less bothersome and easier insertion into the tracheoesophageal (TE) fistula. Also, predictable long device life span (resistance to Candida deterioration) and easy removal of the prosthesis to allow inspection or cleaning and consequent re-insertion are desirable. The VoiceMaster voice prosthesis was developed with these characteristics in mind. The VoiceMaster prosthesis is described in this paper. The first results from the preliminary study in which the currently available VoiceMaster was tested are very encouraging.

Candidiasis↗