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At least 37 records · Page 2Linked to original sources
PubMed1992

The influence of lateral release on patello-femoral joint loading in knee arthroplasty. An experimental in vitro study.

Eight fresh, cadaveric knees have been fitted with four different total knee cemented prostheses. Loading forces at the bone implant fixation interface of the patella component have been measured in a knee joint testing rig by four miniaturized force transducers, before and after a lateral release of the patellar retinaculum. The lateral release resulted in a significant local force reduction in the lateral and/or proximal quadrant of the patella resection plane depending on the knee flexion angle, quadriceps tensile force direction, and the patellar prosthesis design.

Humans↗
PubMed1976

Comparison of an EMG-controlled prosthesis and the normal human biceps brachii muscle.

An electromyographically-controlled elbow prosthesis, the "Boston arm", was tested with constant and sinusoidally-modulated inputs under different loading conditions. These tests were used to determine the frequency response of the EMG amplifier, the range of motor speeds, the force-velocity curve, and the frequency response of the prosthesis for cyclic movements. Human biceps muscle was tested during movements under similar loads, and under isometric conditions using random, electrical stimuli to determine its frequency response. The results were compared to evaluate the performance of the prosthesis and contrast its characteristics to those of the physiological system it replaces. The prosthesis minimizes quiescent power drain, and the possibilities of instability or "tremor" by employing velocity control, an overdamped mechanical system, and an electrical "dead-band". These factors limit the ability of the prosthesis to follow rapidly changing inputs or to move rapidly and accurately to a desired position. These comparisons should provide a useful supplement to the usual clinical evaluations, and a starting point for further improvements in prosthesis design.

Arm↗
PubMedDate not supplied

[Reconstruction prosthesis after upper epiphyseal and diaphyseal resection of the femur for tumor. Results of 16 cases and a biomechanical study].

The authors have treated 16 cases of tumours of the upper end of the femur by resection over at least 12 centimetres and insertion of a massive prosthesis. The tumour was secondary in 9 cases and primary in 7. This treatment was used for metastases where conservative surgery was impossible or had failed. In primary tumours, when the excision was very extensive, the main problem was of stability of the prosthesis and its long-term future. A new type of total massive prosthesis, designed by the authors after biomechanical studies, is described.

Biomechanical Phenomena↗
PubMed1991

[Joint prostheses components of warm-forged and surface treated Ti-6Al-7Nb alloy].

In 1978 development of a TiAl alloy with the inert alloying element niobium was initiated. In 1984, the optimal composition was found to be Ti-6Al-7Nb (Protasul-100). This custom-made alloy for implants has the same alpha/beta micro-structure and equally good mechanical properties as Ti-6Al-4V. The corrosion resistance of Ti-6Al-7Nb is better than that of pure titanium and Ti-6Al-4V, due to the very dense and stable passive layer. Since 1985, highly stressed anchoring stems of various hip prosthesis designs have been manufactured from hot-forged Ti-6Al-7Nb/Protasul-100. Polished surfaces of hip, knee or wrist joints made of Ti-6Al-7Nb intended to articulate with polyethylene are surface-treated by the application of a very hard, 3-5 microns thick titanium nitride coating (Tribosul-TiN), or by oxygen diffusion hardening (Tribosul-ODH) to a depth of 30 microns.

Alloys↗
PubMed1992

Functional evaluation of patients fitted with total knee prostheses.

Degenerative or inflammatory diseases of the knee joint account for a large proportion of diseases affecting the elderly. Treatment aims to eliminate pain, correct the deformity and maintain complete joint mobility. In cases of total joint degeneration, fitting of a joint prosthesis is the technique currently favoured since elimination of pain and correction of the deformity, accompanied by recovery of joint mobility (the fundamental requirements for normal everyday life) can only be obtained if the knee joint is completely replaced. With the discovery of new materials and increasingly sophisticated knowledge about articular mechanics, the knee prosthesis, although more recent than the hip prosthesis, has become ever more widespread to the point that it now represents an irreplaceable aid in the treatment of this common disease. The clinical results obtained are already stable and particularly encouraging and prosthesis design is sophisticated and accurate. There is, however, still the suspicion that current prostheses can be considered "rudimentary" in comparison with the physiological and biomechanical behaviour of the human joint. We therefore wanted to begin an evaluation using a gait analysis system to assess patients fitted with knee prostheses. The first impressions gained in this study are the subject of this article.

Activities of Daily Living↗
PubMed1992

Prosthetic rehabilitation of the edentulous patient requiring a partial maxillectomy.

A variety of problems faces the prosthodontist attempting reconstruction of maxillary defects. This article reviews developments in materials and techniques of obturator prosthesis design for patients experiencing maxillectomy. The size of the maxillectomy defect is one of the main factors governing the prognosis for treatment. Many patients require special prosthodontic techniques. However, routine attention to extension of the prosthesis and balanced occlusion is essential. Obtaining satisfactory retention and stability in the definitive obturator prosthesis can be elusive. Resilient denture base materials are extremely useful in retaining the prosthesis, which obturates small defects. However, the flexibility of these materials makes them unsuitable in large maxillectomy cavities because of the deformation that occurs during mastication. Alternative forms of retention, eg., osseointegrated implants and sectional prostheses retained by magnets, are discussed.

Animals↗
PubMed1975

Syme's amputation. Follow-up study of weight-bearing in sixty-eight patients.

Sixty-eight patients with Syme amputations resulting from industrial injuries were reviewed. The amount of end-weight-bearing was measured with a capacitance transducer. The majority of patients required fitting with a prosthesis designed to relieve end-weight-bearing. The old-fashioned prosthesis with a leather corset was the most effective in achieving reduction of end-weight-bearing.

Accidents, Occupational↗
PubMed1992

[Transesophageal echocardiography study of mitral valve prosthesis].

OBJECTIVE: Transesophageal (TEE) and Transthoracic (TTE) comparative echocardiographic analysis of patients with mitral valve prosthesis. DESIGN: Prospective study. SETTING: In hospital and out patients with mitral prosthesis in a follow-up study by the Cardiology Department and referred to the echocardiographic laboratory of Gregorio Marañon General Hospital, Madrid. PATIENTS: We studied 90 consecutive patients with mitral prosthesis diagnosis. INTERVENTIONS: Comparative and prospective echocardiographic study of transthoracic and transesophageal techniques in mitral prosthesis pathology. RESULTS: TTE diagnosed 18% of dysfunctioning mitral prosthesis patients compared to 56% of cases identified by TEE. TTE observed 1% of mitral prosthesis vegetation compared to 8.8% by TEE. TEE diagnosed left atrial thrombosis in 2.2% and TEE in 10%. Left atrial spontaneous dynamic contrast was identified exclusively by TEE in 55% of all cases. Paravalvular mitral prosthesis leak was correctly identified exclusively by TEE in 20% of cases. CONCLUSIONS: TEE has a greater diagnostic capacity compared to TTE in mitral prosthesis patients. This technique can give a greater security in evaluating mitral prosthesis thrombi, vegetations and leak, establishing a more precise diagnosis of mitral prosthesis dysfunction. The authors concluded that TEE is the technique of choice in noninvasive evaluation of patients admitted with the suspicion of mitral prosthesis dysfunction.

Adult↗
PubMedDate not supplied

[Requirements for design of total prosthesis of the hip joint].

Analysis of the forces acting on the total endoprosthesis of the hip joint and studies carried out for 16 years of the outcomes of 546 operations have demonstrated the position at an angle of 25-40 degrees to the horizontal to be the best variant of establishing the nest of an endoprosthesis. There is a necessity of designing endoprostheses having a cervico-diaphysial angle of 145-150 degrees.

Hip Prosthesis↗
PubMed1977

Interposition arthroplasty of the carpo-metacarpal joint of the thumb.

Nine patients with osteoarthrosis of the carpo-metacarpal joint of the thumb were treated surgically with the metacarpo-trapezial silicone rubber prosthesis designed by Kessler. Patients with pantrapezoidal changes were specifically excluded. All patients at follow-up had chronic synovitis and in five the prosthesis was dislocated. In three patients who had revision operations the previously inserted prostheses were found to be badly torn.

Arthroplasty↗
PubMed1992

Joint replacement components made of hot-forged and surface-treated Ti-6Al-7Nb alloy.

We have developed a titanium-aluminium alloy with the inert alloying element niobium. The optimal composition was found to be Ti-6Al-7Nb (Protasul-100). This custom-made alloy designed for implants shows the same alpha/beta structure as Ti-6Al-4V and exhibits equally good mechanical properties. The corrosion resistance of Ti-6Al-7Nb in sodium chloride solution is equivalent to that of pure titanium and Ti-6Al-4V. This is due to a very dense and stable passive layer. Highly stressed anchorage stems of different hip prosthesis designs have been made from hot-forged Ti-6Al-7Nb. The polished surfaces of hip, knee and wrist joints made of Ti-6Al-7Nb and articulating against polyethylene are surface-treated by means of a very hard and 3-5 microns thick titanium nitride coating (Tribosul-TiN) or by oxygen diffusion hardening (Tribosul-ODH) to a depth of 30 microns.

Humans↗
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↗
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↗
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↗
PubMed1991

Catheter balloon valvuloplasty of stenotic porcine bioprosthetic valves: Part II: Mechanisms, complications, and recommendations for clinical use.

During the last several years dilating balloons have been applied in the treatment of stenotic cardiac valves. This interest has been extended to stenotic porcine bioprosthetic valves. Part I of this review discusses the pathologic changes producing stenotic porcine prosthetic valves. Part II of this review describes an in vitro study of porcine prosthetic valve valvuloplasty defining the mechanisms, complications, and clinical applications. Results of this study indicate a limited and cautious role in balloon dilation of stenotic bioprosthetic valves.

Adult↗
PubMed1992

Tissue ingrowth into titanium and hydroxyapatite-coated implants during stable and unstable mechanical conditions.

Lack of initial mechanical stability of cementless prostheses may be responsible for fibrous tissue fixation of prosthetic components to bone. To study the influence of micromovements on bony ingrowth into titanium alloy (Ti) and hydroxyapatite (HA)-coated implants, a loaded unstable device producing movements of 500 microns during each gait cycle was developed. Mechanically stable implants served as controls. The implants were inserted into the weight-bearing regions of all four femoral condyles in each of seven mature dogs. Histological analysis after 4 weeks of implantation showed a fibrous tissue membrane surrounding both Ti and HA-coated implants subjected to micromovements, whereas variable amounts of bony ingrowth were obtained in mechanically stable implants. The pushout test showed that the shear strength of unstable Ti and HA implants was significantly reduced as compared with the corresponding mechanically stable implants (p less than 0.01). However, shear strength values of unstable HA-coated implants were significantly greater than those of unstable Ti implants (p less than 0.01) and comparable to those of stable Ti implants. The greatest shear strength was obtained with stable HA-coated implants, which was threefold stronger as compared with the stable Ti implants (p less than 0.001). Quantitative determination of bony ingrowth agreed with the mechanical test except for the stronger anchorage of unstable HA implants as compared with unstable Ti implants, where no difference in bony ingrowth was found. Unstable HA-coated implants were surrounded by a fibrous membrane containing islands of fibrocartilage with higher collagen concentration, whereas fibrous connective tissue with lower collagen concentration was predominant around unstable Ti implants. In conclusion, micromovements between bone and implant inhibited bony ingrowth and led to the development of a fibrous membrane. The presence of fibrocartilage and a higher collagen concentration in the fibrous membrane may be responsible for the increased shear strength of unstable HA implants. Mechanically stable implants with HA coating had the strongest anchorage and the greatest amount of bony ingrowth.

Analysis of Variance↗