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At least 847 records · Page 47Linked to original sources
PubMed1995

Optimal control for an above-knee prosthesis with two degrees of freedom.

Our previous research and clinical tests of a self-contained powered above-knee prosthesis (AKP) showed that a knee joint with one degree of freedom (DOF) increases the energy cost of walking with respect to able-bodied subjects. Better symmetry of the gait can improve performance, so we suggest here the integration of a second powered DOF into the knee joint mechanism to control the internal-external rotation of the shank-foot complex. The control for the AKP with two DOFs is based on a method of optimal tracking. The data used for analysis were collected in able-bodied subjects braced with an ankle splint to experimentally duplicate a gait like that of amputees using a two-DOF prosthesis. The simulation showed the following: (1) the technique of optimal programming can be used for simulation of the artificial leg during locomotion; (2) the optimal tracking method is an efficient tool for selection of actuators for the above-knee prosthesis, ensuring that the tracking remains within limits. Limitation of joint torque is desirable in order to reduce the size of the motor, but beyond a certain point limiting maximal torques lead to tracking errors that are associated with higher energy costs and hence the need for a larger power source. The errors are also associated with higher forces at the interface between the socket and the prosthesis. The optimal tracking method allows the optimization of tracking with constraints on the size of the motor used and its energy cost.

Adult↗
PubMed1989

Penile prosthesis surgery: review of ten-year experience and examination of reoperations.

Our ten-year experience from September, 1975, to December, 1985, with 417 penile prostheses in 290 patients is presented. Arteriosclerosis and diabetes mellitus were the two most common causes of impotence in our patient population. The Scott inflatable penile prosthesis accounted for the majority of all implants and all device failures. Complications leading to device failure and/or reoperation occurred in 36 percent of all prostheses. However, including repairs, 91 percent of patients were left with a functional prosthesis. Examination of reoperated patients showed an average increase in corporeal length of 1.67 cm with repeat prosthesis operations (p less than 0.001). No increase in incidence of prosthesis failure could be shown after multiple reoperations.

Erectile Dysfunction↗
PubMed2004

Interactive imaging for implant planning, placement, and prosthesis construction.

PURPOSE: This review describes a new interactive imaging program that allows computed tomography (CT) images to be used to virtually place dental implants and construct a precise guide splint and final prosthesis for delivery at the time of implant placement. MATERIALS AND METHODS: Patients with edentulous arches were recruited to participate in a trial program to assess the feasibility of using CT images in a 3-dimensional image-based program (Oralim; Medicine NV, Belgium) for planning and placing dental implants. Patients meeting the criteria received a CT of the appropriate arch using a denture with radiopaque markers indexed to the opposing arch. Acquisition slices of 0.6 mm or less was required. The software allowed precise planning for implant placement after which the planned case was sent to a manufacturing facility for splint and prosthesis construction. RESULTS: The guide splint and final prosthesis were returned to the clinical site for implant placement. An implant map was provided for each patient showing the diameter and length of the implant and abutments to be used in each predetermined implant site. The surgery was accomplished without a flap, and the prosthesis was delivered immediately. Occlusion required only minor adjustments in all cases, and immediate function was accomplished. CONCLUSION: Interactive computer imaging can allow precise planning for implant position and the images can be used for guide splint and final prosthetic fabrication prior to surgery. This technology is powerful, easy to use, and is a significant advance in implant dentistry.

Computer-Aided Design↗
PubMed2005

Modified stapes prosthesis to limit postoperative vertigo.

OBJECTIVE: To investigate the anatomic relationship between utricle, saccule, and stapes footplate, and adapt the stapes prosthesis tip to reduce postoperative vertigo. STUDY DESIGN: Five temporal bones were serially sectioned and stained, and the distance from the inner lining of stapes footplate to saccule and utricle, respectively, were measured. The Fisch prosthesis was modified with a slope of 45 degrees at its tip to adapt to the anatomic configuration of the vestibule. Fisch's original piston or the modified piston was used in 174 ears (Group I) and 108 ears (Group II), randomly. RESULTS: There was no statistically significant difference in hearing improvement between the 2 groups (P > 0.5). However, postoperative vertigo was significantly reduced when the modified prosthesis was inserted (P < 0.005). CONCLUSIONS: The modified piston improved the hearing to the level of the original piston, and the incidence of postoperative vertigo was significantly decreased. SIGNIFICANCE: A modified prosthesis is presented for a patient undergoing stapedotomy.

Adolescent↗
PubMedDate not supplied

Design and evaluation of the FlexiCore metal-on-metal intervertebral disc prosthesis.

BACKGROUND CONTEXT: The technical difficulties associated with the development of an intervertebral disc prosthesis include endurance demands on the device, lack of consensus concerning the biomechanical principles governing the articulation of the spinal joint and the performance of materials available for implantation. PURPOSE: Although biologically based disc prostheses and augmentations may be the endpoint of spinal disc replacements, these devices and associated technologies will still require decades of work in order to achieve fruition. The more immediate solution will require a durable, biocompatible device capable of restoring range of motion. The evaluation of such a device must include failure testing of critical components as well as a series of fatigue experiments under overloaded conditions. STUDY DESIGN/SETTING: Recent literature citing adjacent level degeneration associated with segmental mobilization and a lack of correlation between successful fusion and clinical success has prompted the need for a dynamic intervertebral disc prosthesis. METHODS: Combined with a better understanding of the biomechanics and the prospect of an increasing percentage of more elderly patients, the future of spinal fusion for pain and instability may need to be reexamined. The authors propose a novel metal-on-metal design for an intervertebral device that features a fixed center of rotation, a mechanical torsional limit, a unique feature to allow for the location of the device in a patient-specific manner, and means by which the device may be implanted directly anterior or anterolaterally. RESULTS: Physiological ranges of motion are retained by the prosthesis. In addition, initial and long-term fixations are achieved through spines and bone ingrowth coating. The device comprises a retained ball and socket positioned between two baseplates. The ball and socket joint permits articulation through the appropriate physiological range of motion and center of rotation as the baseplates provide a stable platform for implantation. CONCLUSIONS: An intervertebral disc prosthesis has been designed and has demonstrated mechanical performance beyond what is required physiologically under preliminary testing.

Alloys↗
PubMed1988

Initial experimental experience with a "replaceable" cardiac valve prosthesis.

An easily "replaceable" cardiac valve prosthesis has been designed. It consists of two parts: (1) a sewing ring incorporating a circlip and (2) a functioning valve (either mechanical or tissue). The circlip is encased in a sewing ring, which is sutured into the natural valve annulus, and grips the functional part of the prosthesis, thereby preventing dislodgment. A simple instrument has been designed to open the circlip a few millimeters to allow easy removal or insertion of the functional element. This sewing ring/circlip with the functional element of a Björk-Shiley prosthesis was used in 10 baboons undergoing mitral valve replacement. Removal and replacement of the functional element was carried out at a second operation between 1 and 12 weeks later. There were no operative deaths. Baboons were electively killed one day to twelve months after the second operation. There were no complications related to the prosthesis; cardiac catheterization showed normal hemodynamics before and after the second operative procedure.

Animals↗
PubMed1993

Early experience with the first pre-connected 3-piece inflatable penile prosthesis: the Mentor Alpha-1.

The aim of this clinical investigation was to obtain preliminary treatment outcome data concerning the Mentor Alpha-1, the first 3-piece inflatable penile prosthesis with pre-connected tubing between the pump and the penile cylinders. The study was designed to be the first multi-institutional treatment outcome report for any clinically available penile prosthesis with data analysis to be independent of the participating surgeons. A total of 12 board-certified urologists of mixed surgical training backgrounds and practices implanted the Alpha-1 device in 112 consecutive patients. With a mean of 27 +/- 5 months of followup the surgical complication rate included a 4% mechanical malfunction, 2% infection rate and 9% reoperation rate. Patient experience with the implanted device was computed from information on 96 of the 112 patients who returned a questionnaire. Of the patients 82% stated that the device fulfilled expectations as a treatment for impotence and 83% had improved sexual intercourse by 8 weeks after implantation. Patient satisfaction was computed on a scale of 12 equally weighted interrelated variables. Of the patients 77% recorded 9 or more cumulative satisfaction points. Patient and physician questionnaire data were analyzed for their relation to the cumulative prosthesis satisfaction score. A significant difference in cumulative scores was found for physician reported long-term postoperative problems (mean satisfaction score 8.1 for patients with problems versus 10.2 for patients without problems, p = 0.018). The Alpha-1, with its feature of pre-connected tubing, is a reliable 3-piece inflatable penile prosthesis associated with a high level of patient satisfaction.

Data Collection↗
PubMed1986

Experience with the AMS 600 malleable penile prosthesis.

A malleable penile prosthesis incorporating a stainless steel core has been designed to provide a more rigid prosthesis while still ensuring concealability. A total of 56 patients in our initial series underwent implantation of this malleable penile prosthesis. Our experience indicates that this prosthesis provides ease of implantation, outstanding cosmetic results, and a much simplified and reduced inventory.

Adult↗
PubMed1995

Urolume endourethral prosthesis for the treatment of urethral stricture disease: long-term results of the North American Multicenter UroLume Trial.

OBJECTIVES: To evaluate the long-term results of the UroLume endourethral prosthesis for the treatment of recurrent bulbar urethral strictures. METHODS: In a multicenter, prospective study 175 patients with recurrent bulbar urethral strictures were enrolled in a Food and Drug Administration (FDA) trial of the UroLume endourethral prosthesis. One hundred thirty-nine patients were available for follow-up at 1 year, and 81 patients were available for follow-up at 2 years. RESULTS: Clinically and statistically significant results were seen at 1 year and sustained at 2 years. Re-treatment rate was down from 75.2% preinsertion to 14.3% 1 year postinsertion of the prosthesis. Explantation was required in only 3% of patients. CONCLUSIONS: Based on these and European data, the UroLume endourethral prosthesis offers a significant advantage over the currently available treatments for recurrent bulbar urethral strictures.

Adolescent↗
PubMed2001

Penile prosthesis implantation.

The development of effective systemic therapy for the treatment of erectile dysfunction has resulted in a significant increase in the number of men presenting for treatment. Not all men with erectile dysfunction will respond to systemic therapy; those who fail may be candidates for penile prosthesis implantation if second and third lines of treatment also fail or are rejected by the patient and his partner. Penile prosthesis implantation continues to play a role in the treatment of erectile dysfunction. There is a potential for the number of penile prosthesis implantation procedures to actually increase. The ideal penile prosthesis is a three-piece inflatable device that permits good penile flaccidity and increases in size and becomes rigid with inflation.

Humans↗
PubMed1995

Preliminary experience with the Endovascular Technologies bifurcated endovascular aortic prosthesis in a calf model.

PURPOSE: The purpose of this study was to develop a bifurcated endoluminal prosthesis for transfemoral placement in the aortoiliac position with a large-animal model that would simulate human implantation. METHODS: Fifteen calves (160 to 200 kg) underwent bilateral femoral artery exposure and transfemoral placement in the aortoiliac position of a bifurcated Dacron prosthesis, inserted through a 26F sheath with an over-the-bifurcation guide wire to retrieve the contralateral limb and secured proximally and distally with self-expanding attachment systems. The preferred location was determined before implantation and compared with final implant location by caliper measurements and angiography. Events during implantation, maneuvers used to accomplish accurate deployment, and final results, as judged by angiography and clinical evaluation, were recorded. Four animals survived and were used for chronic evaluation and healing by gross and microscopic studies. RESULTS: All grafts (n = 15) were patent at the end of the procedure. All (n = 7) noncrimped grafts had minor kinks in areas of curvature, whereas eight of eight crimped grafts (device modification) had none. Torque control of the body and individual limbs was necessary to correct twists before deployment in 10 of 15 grafts, with two greater than 30-degree twists remaining, which did not appear to affect flow. One implant was entirely deployed in the aorta because of parallax error, subsequently avoided by use of a marker board placed dorsally. Three premature deployments occurred, corrected by attachment system lock modification. The mean final implant position was within 2.9 +/- 1.4 mm (aortic), 1.6 +/- 1.1 mm, and 1.5 +/- 0.8 mm (contralateral and ipsilateral iliac limbs, respectively) of the intended position. Three of four animals intended for long-term evaluation were killed prematurely because of clinically evident spinal cord ischemia. Histologic sections at 2 weeks showed early wall repair without inflammatory cells and pannus ingrowth across the anastomosis. CONCLUSION: We conclude that implantation of a bifurcated endovascular prosthesis through the bilateral femoral approach is possible, provided the intended aortic implantation site (neck) is at least 12 mm in length (mean +/- 2 SD each direction). Torque control of each portion of the device will be needed in the majority of instances, with attention to parallax effect necessary for optimal placement. This animal model is not suitable for chronic graft evaluation because of its sensitivity for spinal cord ischemia. Healing data suggest graft incorporation similar to that of a surgically placed prosthesis.

Animals↗
PubMed1995

Failure of a proximally porous-coated femoral prosthesis in revision total hip arthroplasty.

A retrospective study was done on a consecutive series of patients who had revision of a femoral hip prosthesis using a titanium-alloy implant with proximal fibermesh pads. Of 28 patients who had revision using a Harris-Galante (Zimmer, Warsaw, IN) femoral prosthesis between 1985 and 1989, 25 of them (25 hip arthroplasties) were followed for an average of 5.5 years (range, 4-8 years); the other 3 had died. There were 12 men and 13 women whose age averaged 55 years. Thirty-two percent of the patients had moderate or severe femoral bone stock deficiency before surgery and 72% had intramedullary femoral bone-grafting. All of the patients had revision of the acetabular component using a cementless Harris-Galante prosthesis. Five (20%) of the 25 patients have undergone repeat femoral revision, 4 for aseptic loosening and 1 for persistent thigh pain. Of the 20 hips that have not been revised, 9 (45%) of the femoral prostheses have subsided 5 mm or more. Femoral endosteal lysis was present in 36% of all the hips. Only 8 (32%) of the 25 patients had radiologic signs of bone ingrowth fixation of the femoral component. The average Harris hip score rose from 46 before surgery for all 25 patients to 82 (range, 55-100) at last follow-up examination for the 20 patients not rerevised. Because of the poor clinical results (36% of patients with a poor Harris hip score [4 patients] or rerevised [5 patients]) and radiologic results (48% subsidence) of femoral reconstruction with this proximally porous-coated femoral prosthesis, its use for revision hip surgery is not recommended.

Adult↗
PubMed1991

Revision total knee arthroplasty using the total condylar III prosthesis.

Implant selection for the severely damaged knee being treated by revision is difficult. Fixed or rotating hinges have provided mixed results with a high frequency of complication. An alternative to a hinge implant is the total condylar III prosthesis, which can substitute for a deficient collateral ligament. Between August 1980 and April 1987 total condylar III prostheses were used for revision of failed total knee arthroplasties (TKA) of 21 knees in 19 patients. In the same time interval, 649 TKA revisions were performed for a frequency of 3.2% using this prosthesis. The indications for using this prosthesis were bone loss in 10 knees, instability in 9 knees, supracondylar femur fracture in 1 knee, and implant malposition in one knee. At a 4-year follow-up evaluation the knee scores were excellent in 25%, good in 25%, fair in 25%, and poor in 25%. Complications occurred in 33% of the knees. The total condylar III prosthesis provided results similar to other constrained implants used for revision in patients with severe bone loss and ligamentous instability.

Aged↗
PubMed1999

Measurement of bone mineral density by dual-energy X-ray absorptiometry around an uncemented knee prosthesis.

Dual-energy x-ray absorptiometry allows the measurement of bone mineral density (BMD) around an uncemented hip prosthesis, but has not so far been widely used to measure BMD around a knee prosthesis. We studied 16 patients undergoing total knee replacement using a Miller-Galante uncemented prosthesis for either osteoarthritis or rheumatoid arthritis of the knee. The precision of the measurement was improved by using a leg brace. The pattern of bone loss differed in the lateral projection by region (P = .001). There was significant loss of bone from the distal femur but not from the patella or proximal tibia over the 6-month period after insertion of a knee prosthesis.

Absorptiometry, Photon↗
PubMedDate not supplied

Extrinsic obstruction of a Carbomedics prosthesis in the mitral position: echocardiographic and surgical findings.

In this article a case of malfunction of a Carbomedics mitral prosthesis in a patient with mild symptoms is described. Although there was evidence by echocardiography of a thrombus in proximity to the prosthesis and leaflet immobility assumed to be caused by the thrombus, it was demonstrated, at the time of surgery, that the immobility of the prosthetic leaflet was due to a chorda tendineae stuck between the leaflet and the sewing ring. This is the first report of this occurring in a bileaflet prosthesis. It is likely that the restricted mobility of the leaflet had contributed to the thrombosis of the prosthesis.

Adult↗
PubMed1995

The Christensen prosthesis. A retrospective clinical study.

The objective of this study was to determine if the Christensen temporomandibular joint prosthesis system in an effective alternative in treating patients with severe temporomandibular joint disorders. A total of 69 patients who were not responsive to either nonsurgical or prior surgical treatments were placed into one of three treatment groups depending on the following diagnoses: (1) placement of a glenoid fossa-eminence prosthesis with meniscus retention (22 patients, 40 joints); (2) placement of a glenoid fossa-eminence prosthesis without retention of the meniscus (26 patients, 49 joints); (3) total joint replacement (21 patients, 34 joints). Patients were evaluated immediately before surgery and at regular intervals after surgery for an average of 3.1 years. Success was measured as a significant improvement of function and decrease in pain as measured on a visual analogue scale, as well as improved incisor opening as measured with a Therabite Scale (Lorenz Surgical, Jacksonville, Fla.). Comparison of mean and average pre- and postsurgical values for all groups and criteria showed significant improvement. Results of this study indicate that the Christensen temporomandibular joint prosthesis system may offer a viable method for the treatment of severe temporomandibular joint disease with a high degree of success.

Adult↗
PubMed2002

Erosion of a penile prosthesis due to an indwelling urethral catheter as a late complication.

A case of erosion of a penile prosthesis caused by indwelling of a catheter in the urethra is reported. A 73-year-old man had maintained sexual intercourse with penile prostheses (Jonas prosthesis, 19 cm) for 11 years without any complications until he developed cerebral infarction. One month after starting an indwelling urethral catheter in a neurosurgery clinic, the left-side penile prosthesis eroded from the area of the fossa navicularis, and was immediately removed. This type of complication is not unusual in patients with a neurogenic bladder. However, it is not well recognized in patients who suddenly develop a neurogenic bladder following a long-term uneventful period after the implantation of penile prostheses. Therefore, urologists should inform patients who receive this type of treatment that erosion of the prosthesis may develop when they need an indwelling urethral catheter as a late complication.

Aged↗
PubMed2000

Small diameter vascular prosthesis with a nonthrombogenic phospholipid polymer surface: preliminary study of a new concept for functioning in the absence of pseudo- or neointima formation.

The purpose of this study was to prepare a small diameter vascular prosthesis functioning without pseudointima formation. A nonthrombogenic phospholipid polymer, the 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer, has a cell membrane-like structure and has demonstrated strong nonthrombogenicity. We have recently prepared 2 kinds of vascular prostheses, 2 mm in diameter, composed of the MPC polymer and segmented polyurethane (SPU). One includes 7.5 wt% MPC polymer (SPU/MPC[7.5] prosthesis), and the other includes 10.0 wt% (SPU/MPC[10] prosthesis). These prostheses were placed in rabbit carotid arteries and were retrieved at 1 and 4 weeks after implantation. A pseudointima was observed at 4 weeks on the SPU/MPC(7.5). For the SPU/MPC(10), the surface was macroscopically clear without a pseudointima even after a 4 week implantation. It appears that the SPU/MPC(10) prosthesis, functioning without a pseudointima, possesses a stronger nonthrombogenicity and would be more applicable for clinical use.

Anastomosis, Surgical↗