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PubMed1998

A critical look at cementless stems. Taper designs and when to use alternatives.

The clinical and radiographic efficacy of cementless taper design femoral components in total hip arthroplasty was determined. Cementless, taper design, femoral components have been shown to offer comparable clinical results to cemented femoral implants in a double blind, randomized, clinical trial. No differences were observed in terms of disease specific, patient specific, global health, functional capacity, or cost to utility outcome measures. The prevalence of pain in the thigh was the same in each group. Fixation of cementless, taper design, femoral stems depended on three-point fixation as shown on lateral radiographs. A clinical algorithm for femoral stem selection, based on more than 10 years experience with more than 1000 cementless, taper design femoral stems has been developed. Cementless, taper design, femoral implants currently are used in 75% of the authors' patients, provided they are younger than 75 years of age and have funnel shaped proximal femoral medullary canals. Cemented femoral stems are used in older patients, those who have cylindric medullary canals, and those who have inflammatory or unusual bone diseases (Paget's disease, previously irradiated bone).

Activities of Daily Living↗
PubMed1995

[Echocardiographic diagnosis of intermittent failure of a mitral valve prosthesis].

Three cases are reported who had intermittent diastolic jamming of a mitral tilting disc valve. The clinical presentation of this unfrequent but catastrophic early postoperative complication was different in all cases: the first patient presented with heart failure, the third patient had loss of consciousness with enuresis and the second patient was asymptomatic at the time of the diagnosis. Electromechanical dissociation was first suspected by clinical examination in 2 cases but it was confirmed in all 3 cases by 2 dimensional and Doppler echocardiography. Transesophageal echocardiography did not provide any additional information. Besides opening failure of the valve Doppler echocardiography also demonstrated incomplete or delayed opening in the asymptomatic period. Survival is dependent on correct diagnosis and urgent surgical treatment of this type of prosthetic valve dysfunction.

Echocardiography, Doppler↗
PubMed2006

Acetabular cup geometry and bone-implant interference have more influence on initial periprosthetic joint space than joint loading and surgical cup insertion.

Environmental variations in patient-dependent and surgical factors were modeled using robust optimization with a finite element acetabular cup-pelvis model. A previously developed statistical optimization scheme was used to: (1) determine the cup geometry and the optimal cup-bone interference that maximized bone-implant contact areas and minimized changes in the gap volume between the implant and bone surface during gait loading and unloading; and (2) determine the relative contributions of design, patient-dependent, and surgical factors to variations in bone-implant contact areas and a change in gap volume. The statistical analyses indicated that the design variables, namely the equatorial diameter and eccentricity, explained most of the variations in the performance measures. Further, the hemispherical designs performed better than the nonhemispherical designs. The 58 mm hemispherical cup, with 2 mm diametral interferences, minimized the change in gap volume and attained 82% and 81% of the maximum predicted total and rim contact areas, respectively. The equatorial diameter and eccentricity, not the patient-dependent and surgical factors, explained most of the variations in the performance measures. Perfect surface apposition was not attained with any of the cup designs.

Acetabulum↗
PubMed2006

Comparison of static and dynamic computer-assisted guidance methods in implantology.

The planning of dental implant position and its transfer to the operation site can be considered as one of the most important factors for the long-term success of implant-supported prosthetic and epithetic restorations. This study compares computer-assisted fabricated surgical templates as the static method with intro-operative image guided navigation as the dynamic method for transfer of three-dimensional pre-operative planning. For the static method, the systems Med3D, coDiagnostix/ gonyX, and SimPlant were used. For the dynamic method, the systems RoboDent und VectorVision2 were applied. A total of 746 implants were inserted between August 1999 and December 2005 in 206 patients. The static approach was used most frequently, accounting for 611 fixtures in 168 patients. The failure ratios within the first 6 months were 1.31% in the statically controlled insertion group compared to 2.96% in the dynamically controlled insertion group. Complications related to an incorrect position of the implants have not been observed so far in either group. All computer-assisted methods included in this study were successfully applied in a clinical setting after a certain start-up period. The indications for application of computer-assisted methods in implantology are currently given in difficult anatomical situations. Due to uncomplicated handling and low resource demands, the static template technique can be recommended as the method of choice for the majority of all cases falling into this category.

Adult↗
PubMed2000

Clinical experience with long-term use of implantable left ventricular assist devices: indications, implantation, and outcomes.

We describe our clinical experience with 205 implantable left ventricular assist devices at the Cleveland Clinic between December 1991 and January 2000, along with manufacturers' data submitted to the Food and Drug Administration. In patients with end-stage cardiac failure who are suitable candidates for transplantation, these devices serve as excellent bridges to transplantation. Recent modifications have increased pump reliability and reduced thromboembolic rates. The vented electric HeartMate (Thermocardiosystems Inc, Woburn, MA) and the Novacor (Baxter-Novacor, Oakland, CA) left ventricular assist systems allow patients to be discharged from the hospital while awaiting a donor heart. Experience with long-term support is providing insights into permanent implantation of these devices as destination therapy. Although infection remains a major impediment to long-term support, patient-pump interactions leading to changes in the coagulation and immune systems are being recognized, and these interactions may have important implications with respect to thromboembolism, infection, and sensitization to human leukocyte antigens (HLAs). Better understanding of these factors may eventually lead to the development of permanently implantable pumps as an alternative to transplantation.

Assisted Circulation↗
PubMed2004

Intraocular lenses, bacterial adhesion and endophthalmitis prevention: a review.

Postoperative endophthalmitis following intraocular lens (IOL) implantation is still one of the most feared complications of cataract surgery. Bacterial adhesion to IOLs during their insertion is a prominent etiological factor. Polypropylene was the first biomaterial that allowed this relation of cause and effect to be proven. Following adhesion, bacteria replicate, congregate and form multiple layers of microcolonies which actually represent the basic structural unit of the biofilm. The bacteria are embedded in a slime layer. Personal photographs illustrate the different steps of biofilm formation. This slime matrix is not only an adhesive medium; it also affects virulence. Adhesion to IOLs has been studied by several in vitro studies and discrepancies can be found between them which are due to variations of experimental conditions. The strains, the incubation times and the methods all varied. Adhesion is affected by the nature of the IOLs, the isolates and the surrounding medium. Since this medium is very difficult to model because of its complexity, in vivo studies seemed essential. We have recently determined in vivo evolution of the amount of attached bacteria to five types of IOLs. Crystalline lenses from 90 domestic pigs were removed aseptically and replaced with previously infected IOLs. There have been few epidemiological studies published to determine the relationship between endophthalmitis and the IOL type. However, the perfect biomaterial that could prevent postoperative endophthalmitis does not yet exist. Globally, hydrophilic materials and hydrophobic acrylic seem to be less sticky than silicone or PMMA, but this remains to be proven clinically.

Animals↗
PubMed2006

Long-term follow up of the Biocor porcine bioprosthesis in the mitral position.

BACKGROUND AND AIM OF THE STUDY: The study aim was to review the long-term results of mitral valve replacement (MVR) with the Biocor porcine bioprosthesis, in order to investigate patient survival and valve-related complications. METHODS: Data were presented for 546 patients (320 females, 226 males; mean age 49.2 +/- 17.1 years) who underwent MVR with the Biocor porcine bioprosthesis between March 1983 and December 2000. Preoperatively, rheumatic fever was present in 42.3% of patients. Associated procedures were performed in 179 patients (32.7%), and myocardial revascularization in 54 (9.9%). Preoperatively, 41.9% of patients were in NYHA class IV. Postoperative follow up was conducted by telephone interviews, questionnaires, or examination of hospital records. RESULTS: The hospital mortality was 9.5% (n=52); of these patients, 30 died after their first MVR and 22 after mitral reoperation. Mortality after isolated MVR was 7.6%. The total follow up was 2,148.9 patient-years, and actuarial survival was 45.0 +/- 15.8% at 15 years. Freedom from structural valve deterioration (SVD) was 51.8 +/- 13.8% for patients aged <50 years, 88.7 +/- 5.1% for those aged 51-60 years, and 84.0 +/- 9.8% for those aged 61-80 years. The incidence of prosthetic valve endocarditis was low, with 88.8 +/- 6.1% non-recurrence in 15 years. Freedom from reoperation was 33.9 +/- 10.4%, and from thromboembolism was 82.3 +/- 15.0%. Freedom from valve-related mortality was 80.7 +/- 12.5% during a 15-year period. CONCLUSION: The 15-year clinical results with the Biocor porcine bioprosthesis in the mitral position were excellent in a young, predominantly rheumatic, patient population which, preoperatively, was in a grave clinical condition. The incidence of valve-related complications was low, as was that of SVD in patients aged >50 years.

Adolescent↗
PubMedDate not supplied

Tube occlusion from the external ostium after implantation of an aqueous shunt.

Two patients had undergone double-plate Molteno shunt implantation. Both patients required surgical revision, the first at 41 months and the second at 8 months postoperatively, because of a failure of previously functioning tube shunts caused by blockage of the external ostium and intraluminal invasion of the tube by fibrous tissue. At the time of surgical revision, fibrous tissue extended down the lumen of the tube, occluding its external ostium. After excision of this tissue, both shunts became fully functional. When functioning aqueous shunts fail and there is no evidence of a bleb over the shunt reservoir or blockage of the internal ostium, ingrowth of fibrous tissue into the external ostium should be considered as a potential cause, especially if a ripcord or Latina suture has been left in place.

Aqueous Humor↗
PubMed1994

Ten years of experience with various penile prosthesis in Korean.

Currently there are more than 10 types of penile prosthesis available, ranging from the very simple to the very sophisticated. We review our experiences with various penile prosthesis, with particular regard to the complication rate. From Dec. 1983 to Jul. 1993, we implanted 295 penile prosthesis of eight different types. The average age of patients was 44 years. Every patient was evaluated with various multidisplinary diagnostic approaches. The etiologies of impotence were vasculogenic 29%, diabetogenic 22%, spinal cord injury 16%, pelvic bone injury 11%, etc. The types of implanted prosthesis were AMS malleable 143, Jonas 42, Dynaflex 36, Hydroflex 8, Uni-Flate 1000 2, AMS 700 CXM 58, Ultrex 3, Mentor alpha-1 3 and the mean follow-up period was 34 months. The diameters of implanted prosthesis were from 9.5 mm to 13 mm, mostly 9.5 mm (52.9%). The length of implanted prosthesis were from 10 cm to 20 cm, mostly 16 approximately 18 cm (68.8%). Cases with uneven diameters or lengths were 20 (6.8%). The int aoperative complications were 1 corporeal rupture and 1 bladder rupture, and the postoperative complications were 2 prosthesis infections, 2 mechanical failures, and 1 prosthesis infection with mechanical failure. In those 4 patients reimplantations were successful. More than 99% (290/291) patients still have functioning prosthesis. Every prosthesis has their advantages and disadvantages. Factors to be analysed in the selection of proper prosthesis should include patients economic status, education, personality, social activity, hand dexterity, and penile size.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2005

A 3D finite element model of an implanted scapula: importance of a multiparametric validation using experimental data.

In order to help to understand the loosening phenomenon around glenoïd prostheses, a 3D finite element model of a previously tested implanted scapula has been developed. The construction of the model was done using CT scans of the tested scapula. Different bone material properties were tested and shell elements or 8 nodes hexaedric elements were used to model the cortical bone. Surface contact elements were introduced on one hand between the bone and the lower part of the plate of the implant, and on the other, between the loading metallic ball and the upper surface of the implant. The results of the model were compared with those issued from in vitro experiments carried out on the same scapula. The evaluation of the model was done for nine cases of loading of 500 N distributed on the implant, in terms of strains (principal strains of six spots around peripheral cortex of the glenoïd) and displacement of four points positioned on the implant. The best configuration of the model presented here, fits with experiments for most of the strains (difference lower than 150microdef) but it seems to be still too stiff (mainly in the lower part). Nevertheless, we want, in this paper, to underline the importance of doing a multiparametric validation for such a model. Indeed, some models can give correct results for one case of loading but bad results for another kind of loading, some others can give good results for one kind of compared parameters (like strains for instance) but bad results for the other one (like displacements).

Aged↗
PubMed2003

Biomechanical investigation of pedicle screw-vertebrae complex: a finite element approach using bonded and contact interface conditions.

This study used finite element simulation to investigate the load transfer mechanisms within the screw/vertebra complex under different interface conditions, and under varying screw lengths. Both bonded and contact conditions were employed to demonstrate the interface between the screw and vertebra. Loadings were applied at the superior surface of the vertebra and screw unthreaded end, respectively, to represent two modes of flexion loads. The results indicated that the screw within the vertebra underwent a series of discontinuities of loading, identified by the localized high contact pressures, thus creating localized bending moments. The peak stress of screw was located at the junction of the screw's hub and thread, which is consistent with the location of screw failure observed in a clinical setting and the values of peak stress in the screw were proportional to the amount of moments generated by the two loading modes. The interface condition plays an important role in transferring the force within the screw/vertebra complex. A contact interface condition induces significantly higher stress in the screw than the bonded condition. Therefore providing a binding surface (with HA, or porosity coating on the screw surface) between the screw and the vertebra might be the most effective way to prevent screw failure. The influences of screw length on the peak stress in the screw become negligible when the screw is of sufficient length to extend fully into the vertebral body.

Bone Screws↗
PubMed2000

Large tumor endoprostheses and extracortical bone-bridging: 28 patients followed 10-20 years.

Aseptic loosening is a common cause of failure in large tumor endoprostheses. The concept of extracortical bone-bridging was developed to tackle the problem of loosening. New bone which forms across the junction of the bone-prosthesis junction is believed to improve fixation by controlling the transfer of stresses across the junction as well as by giving additional stability to the prosthesis. We present the long-term experience with this concept following major reconstruction after tumor and non-tumor conditions in 31 patients. The overall function was good for upper and lower limb prostheses. Most patients had extracortical bone bridging which was maintained for over 10 years. In 1/3 of patients this involved over 75% of the prosthetic circumference. Prosthetic survival was best with intercalary devices, followed by proximal femoral and distal femoral prostheses. Survival of prostheses in young active patients was similar to that reported in older patients undergoing primary joint replacement.

Adolescent↗
PubMed1997

[Complications and failures of total ankle prosthesis. Apropos of 21 cases].

PURPOSE OF THE STUDY: The authors relate a heterogeneous series of twenty one total ankle prosthesis performed by the same surgeon with an average follow up of 37 months. MATERIAL AND METHODS: Four types of prosthesis were implanted: 4 Ramses, 8 New Jersey, 5 Star, 4 Freeman. The etiology was seven times a rheumatoid polyarthritis, ten times post-traumatic, two idiopathic arthrosis, an hemochromatosis and a late clubfoot sequelae. RESULTS: Results were appreciated according to Bousquet's criteria: 4 excellent results, 5 good, 3 fair, 9 bad. The ankle mobility was not improved by arthroplasty. We noticed 7 loosening whose 2 septic occurring between 18 and 38 months after implantation of prosthesis. DISCUSSION: This series indicates that prosthesis should be only suggested for patients over sixty years old. No difference was found between post-traumatic and rhumatoîd. The pre-operative subtalar arthrosis promoted in significant way an unexpected failure occurrence. CONCLUSION: Indications for total ankle arthroplasty must remain selected. Arthrodesis remains in the immediate future, the best solution for young patients with post-traumatic arthrosis.

Adult↗
PubMed2004

Chronic response of adult rat brain tissue to implants anchored to the skull.

Using quantitative immunohistological methods, we examined the brain tissue response to hollow fiber membranes (HFMs) that were either implanted intraparenchymally, as in a cell encapsulation application, or were attached to the skull as in a biosensor application (transcranially). We found that the reaction surrounding transcranially implanted HFMs was significantly greater than that observed with intraparenchymally implanted materials including increases in immunoreactivity against GFAP, vimentin, ED-1 labeled macrophages and microglia, and several extracellular matrix proteins including collagen, fibronectin, and laminin. In general, these markers were elevated along the entire length of transcranially implanted HFMs extending into the adjacent parenchyma up to 0.5 mm from the implant interface. Intraparenchymal implants did not appear to have significant involvement of a fibroblastic component as suggested by a decreased expression of vimentin, fibronectin and collagen-type I at the implant tissue interface. The increase in tissue reactivity observed with transcranially implanted HFMs may be influenced by several mechanisms including chronic contact with the meninges and possibly motion of the device within brain tissue. Broadly speaking, our results suggest that any biomaterial, biosensor or device that is anchored to the skull and in chronic contact with meningeal tissue will have a higher level of tissue reactivity than the same material completely implanted within brain tissue.

Acrylic Resins↗
PubMedDate not supplied

Mobile bearings in primary knee arthroplasty.

Mobile-bearing knee arthroplasty (MBKA) has potential advantages compared with conventional fixed-bearing total knee arthroplasty (TKA). By allowing unconstrained axial rotation, MBKA can offer greater articular conformity without an increased probability of loosening due to increased axial torque. Increased articular conformity minimizes polyethylene contact stresses, thereby reducing linear wear and subsurface fatigue failure. Axial rotation of the platform also enables self-correction of tibial component malrotation. Despite these advantages, the long-term clinical results obtained with current MBKA devices are similar to those obtained with well-designed fixed-bearing TKA prostheses, with no data suggesting their superiority. The disadvantages of MBKA include bearing dislocation and breakage, soft-tissue impingement, a steep technique learning curve, and concerns about volumetric wear. Hypothetically, longer-term follow-up of MBKA results may reveal a significant difference from fixed-bearing TKA results as the fatigue failure threshold of incongruent polyethylene is exceeded.

Biomechanical Phenomena↗
PubMed1998

Intraoperative assessment of tibiofemoral contact stresses in total knee arthroplasty.

The production of polyethylene wear debris in total knee arthroplasty (TKA) is due to multiple factors. In particular, inadequate implant alignment and high bearing surface contact stresses are associated with polyethylene failure. Optimal implant placement and soft tissue balancing may contribute to reducing wear and the production of polyethylene particles. We present a case in which a quantitative technique was used to measure tibiofemoral contact stresses during implantation of a total knee prosthesis in vivo. In a knee with preoperative varus and fixed flexion deformity, medial compartment contact stresses after initial resection were reduced from 14.3 MPa to 11.3 MPa in neutral alignment by additional bone resection. Posterior cruciate release was required to reduce contact stresses further and to provide satisfactory balance between medial and lateral compartments, as determined by the operating surgeon, and was confirmed by the measurement system (3.8 MPa medially; 3.0 MPa laterally). This technique has potential to fine-tune implant positioning and ligament balancing during TKA.

Aged↗