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At least 379 records · Page 21Linked to original sources

PubMed1990

Measurement of the mechanical properties of the ovine anterior cruciate ligament bone-ligament-bone complex: a basis for prosthetic evaluation.

The reported ultimate tensile stress of the anterior cruciate ligament varies greatly, ranging from 13 to 147 MPa. This study shows that the orientation and degree of flexion of the bone-ligament-bone complex significantly alter the apparent ultimate tensile properties (ultimate tensile stress ranging from 60 +/- 3 to 123 +/- 15 MPa, ultimate specific extension from 37 +/- 7 to 93 +/- 20%), whilst the method chosen for measuring extension also affects the calculated specific extension of the bone-ligament-bone complex. It is suggested that, for considerations of prosthesis design and evaluation, the mechanical properties of the bone-ligament-bone complex should be measured in anterior draw and extension measured using points as close as possible to the positions of the ligamentous attachment sites.

Animals↗

PubMed1979

Predictive range of motion after total knee replacement.

Evaluation of 145 consecutive total knee arthroplasties pre- and postoperatively revealed that regardless of the preoperative deformity (varus, valgus, and flexion contracture), normal alignment of the knee with full extension was obtainable. The amount of flexion to be achieved postoperatively may be determined by the amount of flexion the patient had preoperatively, especially if the degree of flexion was less than 75 degrees. The prosthesis design, sex, age and diagnosis of rheumatoid arthritis were found not to correlate with postoperative motion and stability. In the osteoarthric knee, however, statistical analyses at 6 and 12 months generally showed less postoperative than preoperative range of motion.

Adult↗

PubMed1981

[Early hemodynamic changes after mitral valve replacement with the Hancock prosthesis].

In mitral valve replacement for mitral stenosis the persistence of a depressed cardiac performance immediately after operation has been outlined by several authors. The choice of a porcine central flow prosthesis, that has several theoretical advantages, should allow better acute hemodynamic results. Therefore ten patients have been studied by thermodilution methods and the variations in their hemodynamic parameters has been evaluated with a paired T-Test. Results confirm the persistence of a depressed cardiac function throughout the time span of the study (36 hours). This behaviour could be related to the use of Kirsch solution for myocardial protection. Therefore the authors compare a similar group of nine patients that underwent mitral valve replacement with differently designed prosthesis and the use of a St Thomas analogue cardioplegic solution. They conclude for the persistence, in the acute postoperative period, of an intrinsic myocardial dysfunction.

Adult↗

PubMed1996

Femoral articular shape and geometry. A three-dimensional computerized analysis of the knee.

An average, three-dimensional anatomic shape and geometry of the distal femur were generated from x-ray computed tomography data of five fresh asymptomatic cadaver knees using AutoCAD (AutoDesk, Sausalito, CA), a computer-aided design and drafting software. Each femur model was graphically repositioned to a standardized orientation using a series of alignment templates and scaled to a nominal size of 85 mm in mediolateral and 73 mm in anteroposterior dimensions. An average generic shape of the distal femur was synthesized by combining these pseudosolid models and reslicing the composite structure at different elevations using clipping and smoothing techniques in interactive computer graphics. The resulting distal femoral geometry was imported into a computer-aided manufacturing system, and anatomic prototypes of the distal femur were produced. Quantitative geometric analyses of the generic femur in the coronal and transverse planes revealed definite condylar camber (3 degrees-6 degrees) and toe-in (8 degrees-10 degrees) with an oblique patellofemoral groove (15 degrees) with respect to the mechanical axis of the femur. In the sagittal plane, each condyle could be approximated by three concatenated circular arcs (anterior, distal, and posterior) with slope continuity and a single arc for the patellofemoral groove. The results of this study may have important implications in future femoral prosthesis design and clinical applications.

Aged↗

PubMed1982

Silastic alar-columellar prosthesis in conjunction with rhinoplasty.

A Silastic alar-columellar prosthesis, designed by Lawrence Birnbaum, MD, is commercially available. Used as an implant in the columella and overlying the domes and lateral crura of the alar cartilages, it can aid in obtaining and maintaining tip projection and in reshaping the lobule. Its use is limited and should be reserved only for special cases, ie, those patients in whom there is substantial loss of nasal tip projection, or notable asymmetry, or absent alar cartilages and in patients in whom there is a lack of autogenous grafting material. I have used this prosthesis in 19 patients and have found it to be a valuable adjunct.

Biocompatible Materials↗

PubMedDate not supplied

Fixed partial prostheses supported by 2 or 3 implants: a retrospective study up to 18 years.

PURPOSE: The purpose of this study was to evaluate and compare the long-term performance of fixed partial prostheses supported by 2 or 3 implants. MATERIALS AND METHODS: All patients treated with fixed partial prostheses supported by either 2 or 3 implants during the period 1985 to 1998 were included in this retrospective report. Annual clinical follow-up examinations were performed, with special attention to stability of the prostheses and peri-implant and occlusal conditions. Radiographic examination was performed when the prostheses were delivered (year 0) and subsequently at 1-year, 5-year, and 10-year examinations. RESULTS: A total of 178 patients had received fixed partial prostheses (FPPs) during this period of whom 123 (77 women and 46 men) were available for follow-up (mean age = 65 years, range 32-91). These 123 patients received a total of 146 implant-supported FPPs (63 two-implant- and 83 three-implant-supported) supported by 375 implants. The mean observation periods for the 2- and 3-implant-supported restorations were 9.6 years and 9.4 years (range, 5 to 18 years), respectively. Survival rates for the 2- and 3-implant-supported prostheses were 96.8% and 97.6%, respectively. The implant survival rate after loading was 98.4% for both groups. The mean bone loss at the 5-year follow-up was 0.3 mm for the 2 groups. No significant differences in bone loss (P > .05), implant failure rate (P > .05), or incidence of mechanical complications (P > .05) were found between the 2 prosthesis designs. The complications differed, significantly, with more loose gold and abutment screws in the 2-implant-supported group (P < .05) and more porcelain fractures in the 3-implant-supported group (P < .05). CONCLUSION: The 2-implant-supported partial prostheses exhibited long-term clinical performance comparable to prostheses supported by 3 implants.

Adult↗

PubMed2002

A biomechanical analysis of the rheumatoid index finger after joint arthroplasty.

OBJECTIVE: To determine the mechanisms responsible for the recurrence of ulnar drift after metacarpophalangeal joint arthroplasty in the rheumatoid hand. DESIGN: A three-dimensional biomechanical model of the index finger joints was used to predict the implant loads during several activities of daily living. BACKGROUND: Post-operative clinical evaluation of Sutter metacarpophalangeal prostheses shows a high incidence of fracture and recurrent deformity. METHODS: A six-component force transducer in conjunction with a six-camera motion analysis system were used to obtain kinematic and external loading data from eight patients with rheumatoid arthritis during several simulated activities. These data were used as input into a three-dimensional biomechanical model of the implant and interphalangeal joints of the index finger. Tendon lines of action and moment arms were obtained using a series of MRI scans and CAD modelling techniques. RESULTS: Implant forces were oriented in a radial and dorsal direction to resist the ulnarpalmarly pull of tendons associated with the metacarpophalangeal joint. CONCLUSIONS: The recurrence of ulnar drift is attributable to fatigue failure of the prostheses. After fracture the implant is unable to support the repetitive loading patterns experienced during activities of daily living. RELEVANCE: Understanding the mechanisms responsible for the recurrence of ulnar drift and implant failure is a step towards improving the prosthesis design, surgical procedures and ultimately the patient's prognosis.

Activities of Daily Living↗

PubMed2004

Embolic myocardial infarction in a pregnant woman with a mechanical heart valve on low molecular weight heparin.

Even with continuing technical improvements in prosthesis design and the development of less thrombogenic materials, mechanical valve prostheses still carry a thromboembolic risk significant enough to warrant long-term anticoagulation therapy. Optimal anticoagulation is especially crucial during pregnancy due to the hypercoagulable state that rapidly develops after conception. Conventional anticoagulation therapy with coumarin derivatives is associated with risks of teratogenicity and hemorrhage for the fetus, and thromboembolic and hemorrhagic complications for the mother. As a result, other forms of anticoagulation, such as unfractionated or low molecular weight heparin, have been advocated as an alternative in selected cases. The present report describes a case of embolic myocardial infarction occurring in a pregnant woman with an aortic bileaflet mechanical valve prosthesis while on therapeutic low molecular weight heparin after only one dose was withheld before amniocentesis.

Adult↗

PubMed1996

Muscle strength after successful total knee replacement: a 6- to 13-year followup.

This study investigated the long term results of muscle strength of the knee joint after total knee replacement. Isokinetic testings of 120 degrees and 180 degrees per second and isometric testings at 30 degrees and 60 degrees knee flexion were studied on 1 healthy group and 3 groups of patients 6 to 13 years after total knee arthroplasty with prosthesis designs of total condylar, low contact stress meniscal bearing, or low contact stress rotating platform. The total condylar and low contact stress rotating platform prostheses were designed for use with a cut posterior cruciate ligament, whereas the low contact stress with meniscal bearing type was designed for use with a retained posterior cruciate ligament The muscle strength ratios of hamstring to quadriceps were compared among the prosthetic designs and there were no statistical differences among patient groups. Whether the posterior cruciate ligament was cut or retained did not affect the relative muscle strength of the quadriceps and hamstring. All hamstring to quadriceps ratios from the isokinetic testings of these 3 prostheses design groups were greater than those of the healthy group, but were quite close to those of patients with cut anterior cruciate ligaments or with lower levels of daily activity. The hamstring to quadriceps ratios after successful total knee replacement were not the same as those of the healthy group even after long term (6-13 years) functional adaptation.

Aged↗

PubMed1991

Reconstructions after resections of tumors involving the proximal femur.

Advances in prosthesis design, the use of allografts, and a systematic approach to the staging and surgical treatment of musculoskeletal tumors have made limb salvage possible in the proximal femoral region. With the use of effective adjuvant therapy, limb salvage is now an option for the majority of patients presenting with locally invasive neoplasms in this area. The increase in functional outcome is sufficient to warrant serious consideration of limb salvage over the corresponding amputation. Preoperative planning is discussed along with surgical techniques.

Arthrodesis↗

PubMed1995

Prevalence of knee problems in the population aged 55 years and over: identifying the need for knee arthroplasty.

OBJECTIVE: To determine the prevalence of knee problems in people aged 55 years and over and identify those who should be considered for knee arthroplasty. DESIGN: Postal survey; questionnaires were sent to a multistage stratified probability sample of residents of North Yorkshire Health Authority aged 55 and over. SETTING: A health district with a population of 210,000 aged 55 and over. RESULTS: An initial four page postal questionnaire produced an 86% response rate among 18,827 eligible patients. A subsequent detailed questionnaire sent to 1277 patients with knee problems (with a response rate of 78%) then determined the prevalence of severe pain and severe disability. Pain and disability consistent with the need to consider arthroplasty was found in 20.4/1000 (95% confidence interval 18.0 to 23.1); of these, 4.1 (2.7 to 5.8)/1000 had extreme disability. Age and sex specific rates in men who might benefit from arthroplasty were, in those aged 55-64, 12.9 (8.4 to 19.0)/1000; aged 65-74, 12.1 (7.4 to 18.4)/1000; aged 75 and over, 20.3 (12.9 to 30.5)/1000. In women aged 55-64 the rates were 12.9 (8.6 to 18.7)/1000; aged 65-74, 19.6 (13.9 to 26.7)/1000; aged 75 years and over, 42.6 (34.3 to 52.4)/1000. CONCLUSIONS: Total knee replacement has until recently been considered unreliable and often seen as a last resort for many with severe knee problems. Advances in prosthesis design and surgical and anaesthetic techniques have transformed this procedure into a reliable option with a potential for reducing disability and dependency in a large number of people in the community. Understandably, the prevalence pool of those who may benefit is large; health authorities and, increasingly, general practitioners should consider purchasing more total knee replacement surgery to offer real choice to those in need.

Aged↗

PubMed1988

Total hip acetabular component position affects component loosening rates.

Loosening is the most common long-term problem following total hip arthroplasty. Many factors, including patient selection, cement technique, femoral component placement, and prosthesis design reportedly affect the incidence of loosening. Theoretically, the location of the hip center of rotation substantially affects the load on the hip, and superior and lateral hip center location will result in higher loads than medial and inferior placement. Long-term follow-up studies (average, 9.1 years after surgery) using logistical regression analysis demonstrate significantly higher rates of femoral loosening with acetabular components placed in a superior and lateral (i.e., nonanatomic) position, compared with acetabular components placed in a nearly anatomic position.

Acetabulum↗

PubMed1998

Use of the fixed mandibular implant in oral cancer patients: a retrospective study.

PURPOSE: A retrospective review of the fixed mandibular implant (FMI) in oral cancer patients is presented. Success of the device and associated complications are discussed. PATIENTS AND METHODS: Eighteen oral cancer patients with an FMI were identified. All were treated at a single institution. Information was obtained from medical records, radiographs, and recall examination. Demographic data, surgical history, prosthesis design, and functional data were analyzed. Results were statistically compared with outcome data for the FMI in noncancer controls. RESULTS: The average patient age was 64 years. Seventeen of the 18 patients had squamous cell carcinoma, most being T3 or T4 lesions at diagnosis. Four of 18 patients received radiation therapy (XRT) followed by resection, 11 had resection followed by XRT, two had XRT alone, and one had surgery alone. The average XRT dose to the mandible was 65.4 Gy. Two of the patients received hyperbaric oxygen (HBO). Sixteen of the implants had been loaded and followed an average of 16.4 months. Early complications included soft tissue overgrowth around pins (4 of 18); tongue ulceration (2 of 18), and intraoral wound dehiscence (2 of 18). Late complications included fistula formation (3 of 18); submental erythema (2 of 18), and persistent tissue overgrowth around pins (1 of 19). No complications required removal of the implant. Only the rate of fistula formation was statistically greater than in controls (P = .005). Average time between FMI placement and prosthesis delivery was 3.6 months. Fourteen of the 16 patients with a prosthesis reported improved ability to eat solid foods and improved articulation. All 16 patients reported improved aesthetics and increased comfort in social settings. CONCLUSIONS: The FMI is a valuable device for dental rehabilitation in oral cancer patients. Success was shown in radiated patients. The complication rate is acceptable, and stability was shown over the follow-up period. Rapid rehabilitation and functional and aesthetic improvements were also reported.

Aged↗

PubMed1978

[Biomechanical aspects of arthrosis of the carpometacarpal joint of the thumb and its treatment with a special endoprosthesis].

The joint between the trapezium and the first metacarpal is anatomically like a saddle. In function, however, it is used like a ball and socket joint with the following possible movements: 1. Flexion - extension, 2. abduction - adduction, 3. opposition and circumduction. The movements in the two first planes are completely congruent, whereas in the third an incongruent motion of the joint is created by the rotation of the metacarpal on the trapezium. In this situation there is joint contact at one point only, being - biomechanically - a prearthrotic deformity as described by HACKENBROCH. Accordingly, the carpometacarpal joint of the thumb in normal use is exposed to special stress which can end in degeneration. When in arthrosis of the carpometacarpal joint of the thumb conservative measures fail, we replace the deformed joint by prosthesis having the construction of a ball and socket joint. The prosthesis (designed by FRANCOBAL) has a metallic part with body, neck and a sphereshaped head, and a polyethylene socket, which can be coupled to the head by a snap mechanism. Both parts are inserted with polymethylmetacrylate cement into the prepared bone of the trapezium and the first metacarpal. The advantages of this method are: no pain, stability of grip, and motion similar to that of a ball and socket joint. Because this motion is physiological, loosening of the implants and their insertions are avoided. The first 8 patients treated with this method show satisfying functional results. The longer follow-up time is 6 years.

Aged↗

PubMed1998

In vitro testing of a novel limb salvage prosthesis for the distal femur.

OBJECTIVE: The aim of this paper was to define strain pattern in the host bone following distal femoral resection and implantation of a massive prosthesis. Two methods of coupling the prosthesis to the bone were compared: the Compliant Pre-Stress device, and a standard cemented tumour prosthesis. DESIGN: The composite femur model was selected to minimize variables. Four femurs were tested before and after implantation. Both coaxial and cantilever loading were applied. BACKGROUND: Cemented distal femoral replacement following resection of malignant tumours has a high failure rate at 5 years and is associated with extensive bone resorption thought to be secondary to stress shielding. METHODS: Strain was measured in the medial and lateral sides at four levels with physiologic loads applied, in the intact, Compliant Pre-Stress, and cemented femurs. Repeated measurements were taken. Strains in the implanted femur were calculated as percentage of the intact, and statistically analyzed. RESULTS: The most reproducible results were noted in cantilever bending (variability <5%). The Compliant Pre-Stress device demonstrated a more physiologic strain pattern than the cemented stem. The most significant difference between the two implants was in the area adjacent to the interface. CONCLUSIONS: The Compliant Pre-Stress device shows less stress shielding than a standard cemented implant. The protocol described and the use of composite femurs demonstrated reproducible results. RELEVANCE: Massive prosthesis are commonly used following tumour resection or removal of failed primary joint replacement prostheses. The failure rate for aseptic loosening for cemented implants is 25% at 5 years with significant bone resorption about the implant. Compliant Pre-Stress is an innovative technology that allows coupling of metallic implants to bone with little stress shielding. This paper aims to define the strain patterns about the implant and compare them to a standard cemented device. The reduced stress shielding of the Compliant Pre-Stress fixation system should guarantee reduced bone loss around the implant and help to obtain improved clinical results.

Journal Article↗

PubMed2005

Immediate and early implant loading protocols: a literature review of clinical studies.

The purpose of this literature review is to present the outcomes of clinical studies on immediate and early loading protocols, identify shortcomings, and suggest a number of questions that still require exploration. English language clinical studies, limited to peer-reviewed journals between 1975 and 2004, were reviewed to identify treatment outcomes with these loading protocols. The data were tabulated from studies reporting on patients treated with fixed and overdenture prostheses. The former included partially edentulous patients treated with single or multi-unit prostheses. Within the limitations of this review, it can be concluded that these treatment protocols are predictable in the anterior mandible, irrespective of implant type, surface topography, and prosthesis design (success rates 90%-100%). Limited evidence for the edentulous maxilla (success rates 90%-100%) and the partially edentulous patient (success rates 93%-100%) are available, underscoring the need for further research. Studies suggest that to achieve predictable results in extraction sites, implant placement should be restricted to sites without a history of periodontal involvement (success rates 61%-100%). A number of questions require further exploration. There is a need to thoroughly investigate clinical outcomes to measure the economic benefit of these protocols and the impact of treatment on a patient's quality of life. Furthermore, more accurate long-term studies reporting on treatment protocols for separate clinical situations are required to allow meaningful comparisons.

Dental Implantation, Endosseous↗

PubMed2005

Total knee arthroplasty: range of motion across five systems.

UNLABELLED: Range of motion after total knee arthroplasty is an important variable in determining clinical outcome. The goal of this study was to assess range of motion across five types of posterior-stabilized knee prostheses used sequentially in the same institution during 17 years. The hypothesis was that absolute flexion would improve in newer models of this basic prosthesis design. Only primary knee arthroplasties in patients with osteoarthritis were evaluated. A retrospective analysis was done. Three hundred fifty-eight knees with osteoarthritis were reviewed. The average arc of motion was 103 degrees before surgery and 111 degrees after surgery. Absolute flexion was clinically similar but improved from before surgery (110 degrees ) to after surgery (113 degrees ). No difference was found when comparing improvements in range of motion among the different types of prostheses used. This study did not show that any knee system made a difference in determining the final range of motion postoperatively. Height emerged as a predictive factor of absolute flexion. Preoperative range of motion is the most important variable in determining improvements in range of motion, with height playing a secondary role. LEVEL OF EVIDENCE: Prognostic study, Level II-1.

Aged↗

PubMed2005

Evidence-based considerations for removable prosthodontic and dental implant occlusion: a literature review.

The dental literature is filled with discussions of dental occlusion, occlusal schemes, philosophies, and methods to correct and restore the diseased, worn, or damaged occlusion. Traditionally, these discussions have been empirical in nature and not based on scientific evidence. Due to the empirical nature of the literature, the study of occlusion has been extremely complex and troublesome to both pre- and post-doctoral students. The introduction of osseointegrated implants has further complicated the situation. Dentists may apply the principles of occlusion for the natural dentition directly to implant-supported and retained restorations. Although this may be successful, this rationale may result in overly complex or simplified treatment protocols and outcomes. There is an emerging body of scientific literature related to dental implant therapy that may be useful in formulating treatment protocols and prosthesis designs for implant-supported restorations. This review focuses on some of the "classic" removable prosthodontic literature and the currently available scientific literature involving removable prosthodontic occlusion and dental implant occlusion. The authors reviewed the English peer-reviewed literature prior to 1996 in as comprehensive manner as possible, and material after 1996 was reviewed electronically using MEDLINE. Electronic searches of the literature were performed in MEDLINE using key words-animal studies, case series, clinical trials, cohort studies, complete denture occlusion, dental implant function, dental implant occlusion, dental implant occlusion research, dental implant functional loading, dental implants, dental occlusion, dental occlusion research, denture function, denture occlusion, dentures, implant function, implant functional loading, implant occlusion, occlusion, and removable partial denture occlusion-in various combinations to obtain potential references for review. A total of 5447 English language titles were obtained, many of which were duplicates due to multiple searches. Manual hand searching of the MEDLINE reference list was performed to identify any articles missed in the original search.

Animals↗