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At least 379 records · Page 21Linked to original sources
PubMed2002

In vitro kinematic patterns are similar for a fixed platform and a mobile bearing prosthesis.

In vitro dynamic simulation of knee flexion was performed to quantify knee kinematics for a mobile bearing prosthesis that allows the tibial insert to translate and rotate with respect to the baseplate. Six cadaver knees were tested in the intact state, after implanting a fixed platform prosthesis, and after implanting a mobile bearing prosthesis. The mobile bearing prosthesis significantly increased the tibial internal rotation and medial shift compared with the intact knee, near 90 degrees of flexion. Both prostheses increased the patellar medial shift near 90 degrees of flexion. The patellar flexion was significantly larger for the mobile bearing prosthesis than for the fixed platform prosthesis for most of flexion. Motion of the insert with respect to the baseplate may have contributed to the variations in tibiofemoral kinematics, whereas tibiofemoral kinematic changes influenced the patellofemoral kinematics. Although the kinematics were similar for the 2 types of prosthesis, the possibility of complications related to increased patellar flexion and backside wear of the tibial insert should be considered.

Aged↗
PubMed2006

[The custom-fit voice prosthesis, for treatment of periprothetic leakage after tracheoesophageal voice restoration].

BACKGROUND: Leakage around an indwelling voice prosthesis is detected during 13% up to 27% of all replacement procedures of voice prosthesis and causes serious complications in further voice restoration of the laryngectomee. Lots of therapeutic options to stop periprothetic leakage have been described (Injection of Bioplastique, autologous fat or collagen, suture techniques, spacer therapy) without convincing success rates. METHODS: Custom-fit voice prostheses are ordinary indwelling voice prostheses (Blom-Singer low pressure Indwelling 20 fr) with enlarged flanges and reduced shaft length that are individually sized for the shunt of the laryngectomee. Especially enlarging the esophageal flange provides a tight sealing of leakage around the prosthesis. PATIENTS: In a one year lasting clinical trial 692 voice prostheses were changed. In 77 cases periprothetic leakage was detected and fistulas were fitted with individually sized voice prostheses. RESULTS: In 76 cases total control of leakage was achieved without any specific complications taking place. Moreover two types of leaking tracheoesophageal fistulas were distinguished, a dilated-atrophic and an infected-necrotic type. 57% of the fistulas were dilated-atrophic type and 43% of the fistulas were classified infected-necrotic type. Infected-necrotic fistulas needed enlarged flanges tracheal an esophageal for tight sealing in 91% of the cases whereas dilated-atrophic fistulas needed double flanges only in 45%. 70% of infected-necrotic type fistulas needed only one singular history of a custom-fit prosthesis and could be changed back to ordinary indwelling prostheses after healing had taken place. CONCLUSIONS: As the insertion of a modified prosthesis is only slightly more effort than an ordinary voice prosthesis insertion, the success rate is high und complications are rare we recommend the custom-fit voice prosthesis for treatment of periprothetic leakage.

Aged↗
PubMed2002

Hydroxyapatite prosthesis extrusion.

OBJECTIVE: To examine the mechanism of prosthesis extrusion and evaluate preoperative and postoperative variables associated with extrusion of hydroxyapatite prostheses for ossicular reconstruction. STUDY DESIGN: Retrospective case review. SETTING: Tertiary referral, university medical center. PATIENTS: Patients undergoing ossiculoplasty with a hydroxyapatite prosthesis and having at least six months follow-up. MAIN OUTCOME MEASURE: Prosthesis extrusion, defined as loss of the tympanic membrane resulting in exposure of the prosthesis. Extrusion is further classified into early (< 2 months) and late (> 6 months). RESULTS: Early extrusion or tympanoplasty graft failure occurred in 15/195 cases (8%). Late extrusion was seen in 17/125 cases (14%). Cases exhibiting late extrusion had a significantly greater incidence of postoperative atelectasis (p < 0.0001), recurrent otitis media (p < 0.0001), and myringitis (p = 0.003) than those with retention of the prosthesis. Regression analysis found an abnormal contralateral ear increased the risk of postoperative recurrent otitis media, while staged surgery reduced the risk, odds ratios of 3.56 (95% confidence interval 2.20-9.37) and 6.84 (95% CI 4.24-17.76) respectively. There were no preoperative variables that predicted postoperative atelectasis or myringitis. CONCLUSIONS: Recurrent otitis media, myringitis, and atelectasis developing after ossiculoplasty are associated with a greater risk of prosthesis extrusion. Predicting postoperative complications from preoperative and intraoperative findings proved difficult. Measures to prevent atelectasis, such as covering the prosthesis with cartilage, are recommended at the time of ossiculoplasty.

Cartilage↗
PubMed1997

Development and clinical evaluation of a second-generation voice prosthesis (Provox 2), designed for anterograde and retrograde insertion.

Prosthetic voice restoration has considerably improved the results of vocal rehabilitation after total laryngectomy, and is presently the method of choice for many health-care providers treating laryngectomized patients. The Provox voice prosthesis, developed in the Netherlands Cancer Institute, is an indwelling device that has been applied in recent years with regular success. Its retrograde replacement method, using a disposable guide wire, assures reliable, atraumatic positioning of the prosthesis in the tracheoesophageal fistula. However, the method sometimes may be uncomfortable for the patient; therefore an adapted prosthesis and new replacement equipment were developed, which enable bidirectional insertion, i.e. not only in the traditional retrograde manner through the pharynx, but especially in an anterograde manner through the stoma. This second-generation voice prosthesis (Provox 2) was studied in a prospective clinical trial in 44 patients (33 experienced patients, seven first-time replacements and four primary insertions). The study demonstrated that the anterograde insertion with the Provox 2 system was applicable in all patients, making the voice prosthesis even easier to handle than with the traditional retrograde method. A stenosis of the pharyngoesophageal segment no longer interfered with the replacement. In addition, the patients judged the new method as being favourable, reporting significantly less discomfort during the replacement procedure (paired Student's t-test: p < 0.0001). Furthermore, the adapted voice prosthesis could be removed from the tracheoesophageal fistula without excessive force (mean 7.9 N, range 6.0-14.0 N), more easily than the original Provox (mean 20.9 N, range 5.5-25.0 N). It can be concluded that this second-generation indwelling voice prosthesis (Provox 2) seems to be a further improvement in the application of this voice rehabilitation system, not only simplifying the replacement procedure, but also diminishing the discomfort for the patient.

Aged↗
PubMed1999

[Revision of infected total hip prostheses by ablation reimplantation of an uncemented prosthesis. 57 case reports].

PURPOSE OF THE STUDY: 57 cases of infected total hip prosthesis treated by removal of the implant and implantation of unncemented prosthesis, were studied to evaluate functional and sepsis results. MATERIAL AND METHODS: 57 patients treated by reimplantation of an uncemented total hip prosthesis after removal of the infected prosthesis were observed. 16 patients underwent a single-stage exchange, 41 a two-stage reimplantation. 46 cases were analysed for infection findings (clinical, radiological and biological assessment) and only 34 cases for functional evaluation (PMA scale, Harris score) with a mean follow-up of 6.6 years. The antibiotic therapy was adapted to each patient but generally, the treatment was prolonged. RESULTS: At follow-up time (which might be too short in time), only 2 patients had a recurrence of infection. One had a single-stage exchange (reoperated by two stage exchange with a good final result at 6 years follow-up), the other a two-stage exchange. In both cases we found that postoperative antibiotic therapy was inadequate. Functional results were better with PMA scale (23 good results of 34) than with Harris score (14 excellent or good results only). 5 patients were reoperated for mechanical implant failure. DISCUSSION: Since 1991, we adopted a standardized procedure to treat chronic infected total hip prosthesis including: routine preoperative aspiration of symptomatic prosthesis; removal of the implant and around debridement followed at a later date (6 weeks) by reimplantation using uncemented implants (hydroxyapatite coated implant). Postoperative antibiotic therapy has to be massive (parenteral bitherapy for at least 21 days after each operative stage) and has to last 6 months after reimplantation. This procedure seems reliable and corroborate the validity of two-stage treatment. The using of uncemented implants allows a good bone reconstruction and does not seem to increase the risk of septic recurrence. CONCLUSION: It is quite difficult to find a hard and fast rule in infected prosthesis treatment, because many factors can influence results. The proposed procedure seems reliable, even if antibiotherapy is long and hard, but requires a strong collaboration between bacteriologist infectiologist and surgeon.

Adult↗
PubMedDate not supplied

Biomechanical considerations of multiple-component hip prostheses. Analysis of three failures of the Lippman transfixation hip prosthesis.

Three cases are presented and analyzed in which a Lippman Transfixion Hip Prosthesis had to be replaced because of the discomfort of the patient. In each case, there was evidence of wear between the head of the prosthesis and the flange. The different wear patterns indicated problems which exist in the alignment of component parts of the prosthesis. In each case there was low grade sepsis to which the debris may have contributed. Because of phagocytosis, amount of debris accumulation was difficult to evaluate. The factors which appear to have contributed to the amount of debris accumulation were: the length of time the prosthesis had been used; the degree of alignment and amount of debris which may be formed and is phagocytized; the degree of manufacturing control. The design of this prosthesis incorporated mechanical problems which are generally undesirable because of: the eventual deformation of the end of the pivot rod or hole in the head of the prosthesis: progressive loosening of the movement due to this and inherent malalignment; the difficulty in fabrication, assembly and installation of the prosthesis because of the multiplicity of parts; the difficulty in maintaining adequate control of surface finishes.

Arthroplasty↗
PubMed2004

The use of synthetic vascular prosthesis in the surgical treatment of secondary aorto-duodenal fistulas.

In this paper the methods with synthetic vascular prosthesis used in surgical treatment of the secondary aorto-intestinal fistula are presented. 10 cases of 22 patients treated in the years 1993-2003 for secondary aorto-intestinal fistulas as a complication of vascular prosthesis infection are analysed. In all patients the abdominal CT, scintigraphy with technetium 99m labeled leucocytes and endoscopy were performed. The patients underwent the operation of infected dacron prosthesis' replacement with silver/collagen coated prosthesis or extraanatomic bypass (subclavian to femoral). To close the intestinal fistula the duodenectomy with gastroenterostomy was performed or the duodenum was sutured and protected with the use of pedicled omentum. In 4 patients extraanatomic subclavian-femoral of polytetrafluoroethylene (PTFE) bypass was used. In these cases the intestinal surgery was composed of the partial duodenectomy with fistula excision and duodenal stumps formation followed by antecolic gastrojejunostomy with the Braun's enteroanastomosis and pyloroplasty. In this group 2 patients (50%) died in the follow up period. There were two extraanatomic bypass thromboses in the 30 days follow up and one amputation (25%). The infected vascular prosthesis was replaced with silver/collagen coated prosthesis in the 6 patients. In these cases duodenal fistula was closed with two layers of stitches and additionally protected with pedicled fragment of the greater omentum, which was sewn on the duodenum. In this group 1 patients (16.7%) died in the follow up period. In one case (16.7%) in 9 months after operation reinfection od silver prosthesis was observed. There were no significative differences (p = 0.45) in terms of early mortality between both group of patients. The treatment of the fistula is a difficult and hazardous surgical procedure, results of which are unpredictable.

Adult↗
PubMed2004

[Experimental study on the reconstruction of circumferential tracheal defects with novel prosthesis].

OBJECTIVE: To investigate the feasibility of using new tracheal prosthesis made of biomaterials to replace extensive circumferential tracheal defects in mongrel dogs. METHODS: Three types of tracheal prostheses were developed, whose basic skeleton of tubular mesh was knitted with polypropylene monofilament and poly (lactic-co-glycolic acid) fiber. The inner side of type-I tubular mesh was first coated with polyurethane solution and then with collagen. The exterior of type-I was then immobilized with collagen-hydroxyapatite composites. In contrast, the internal and external walls of type-II were coated with polyurethane solution, which produced a prosthesis similar to a nonporous one, while type-III was coated only with collagen solution. Surgical resection and replacement of a segment of the cervical trachea was performed in 16 adult mongrel dogs. The efficacy of the implanted prosthesis periodically evaluated postoperatively. RESULTS: In group A, only one died from prosthetic dehiscence, another from anastomotic leakage, and the others had uneventful postoperative courses. The implanted prosthesis was completely incorporated with the recipient trachea, where different length of reepithelialization occurred on the luminal surface of the reconstructed trachea. Macroscopic examination showed scattered and different sizes of neo-ossification surrounding the implanted prosthesis. The prosthesis was roentgenopaque when exposed to routine X rays. In contrast, a relatively high number of complications occurred postoperatively in group B and C. CONCLUSION: Type-I tracheal prosthesis may be used effectively for long-segment circumferential tracheal replacement, and appears very promising for clinical application, with further improvements in promoting the epithelialization.

Animals↗
PubMed2005

[Design, production and clinical application of custom total hip prosthesis].

The key to the research of the hip prosthesis is to prolong the effective using time of the hip prosthesis, but bone loss and aseptic loosening are the influential factors in this aspect. Since each person has his own characteristic, it is difficult for the standard hip prosthesis to fit with the patient's femoral canal, so the stability can not the ensured. Moreover, some patients have congenital abnormality or a serious defect in bone or arthrosis, which makes an obvious deviation from the normal, therefore they can not use the standard hip prosthesis. CAD/CAM is useful for to individual three-dimensional femoral reconstruction, which can improve the stability of the prosthesis and effectively prevent the loosening of prosthesis. This article introduces the advantage, design, production and the problems of custom CAD/CAM hip prosthesis.

Arthroplasty, Replacement, Hip↗
PubMed1990

Reconstruction of the ossicular chain using a multistrand wire spring prosthesis.

A multistrand wire spring prosthesis is presented for ossicular reconstruction. This device offers a workable solution not only to the ossiculoplasty problems associated with lateralization of the tympanic graft and displacement of the prosthesis, but also to other problems such as fixation to middle ear wall, tissue reaction, resorption, degeneration, biodegradation, or poor sound conduction, which are obviated using a stainless steel wire for the ossicular prosthesis. The spring also protects the inner ear from external trauma. Long-term reconstruction results of 14 cases using first generation coil spring prosthesis are presented. A freely mobile prosthesis head composed of cartilage with perichondrium on a wire-mesh platform distributes pressure evenly to the undersurface of the tympanic membrane and further ensures the prevention of pressure necrosis and extrusion. When the handle of the malleus is present, the head-loop assembly of the spring prosthesis is designed to securely capture the handle. There is no practical loss of sound energy passing through the spring. Over a period of 14 years none of the wire prosthesis was found to have eroded through the stapedial footplate.

Bone Conduction↗
PubMed1989

[The 4 mm plasma-tetrafluoroethylene prosthesis as a coronary vessel replacement in the animal experiment].

For coronary artery revascularisation the availibility of a prosthesis may be useful, which in case of insufficient or inadequate veins may be used as a biocompatible substitute. The new 4 mm Plasma TFE prosthesis consisting of a woven fiber of polyethylenteraphtalate (PET) coated with an ultrathin layer of Tetrafluoroethylene (TFE) has shown to be highly non thrombogenic in vitro and was therefore regarded as being promising. In an experimental study 10 beagle dogs underwent aortocoronary bypass grafting in order to evaluate the in vivo behavior of the prosthesis. In group 15 dogs received a Plasma TFE prosthesis of 7 cm length. To overcome the problems of inadequate caliber at the distal side of the anastomosis another 5 dogs in group II received a composite sequential graft composed of a 4 cm proximal Plasma TFE prosthesis and a 3 cm distal autologous saphenous vein. Treatment with antiplatelet drugs (Aspirin) was started during the operation and continued by daily doses of 500 mg p. os. Control-angiography 1 week after the operation demonstrated patency of 1 out of 5 grafts in group I and 4 out of 5 grafts in group II. Half a year later the only graft from group I was still patent, whereas in group II all grafts had thrombosed. Histological examinations showed the graft coated with a layer of 50-250 microns fibrous tissue mear the aortic anastomosis, while more distally the prosthesis was completely occluded. In conclusion the 4 mm Plasma TFE prosthesis though promising from in vitro experiments has proven to be not suitable as a substitute for aortocoronary artery bypass grafting in the dog.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1979

[Experimental and clinical studies on the Jikei total knee prosthesis (author's transl)].

Total knee prostheses for a dog were developed and were inserted into knee joints of seven adult dogs to study the mobility of the artificial joint, the degree of fixation to bone and the durability of the prosthesis, to examine the reactions in the surrounding tissues and the internal organs in the JIKEI total knee prosthesis in clinical use. As a result of surgery, it was proved that the length in the hinged part of the prosthesis needed to be seventy percent of the length of the excised area of the joint to gain good mobility and supportability of the knee joint after surgery. As a result of findings based on necropsy, wear at the hinged part of the prosthesis was mild and debris caused in wear was not harmful for the living body if breakage does not occur there. Histopathological findings revealed that collagenous fibrous tissue with new bone formation was observed on the inner wall of the bone around the stem of the prosthesis four months after surgery. Then it was proved that the fixation of the prosthesis to the bone was sufficient. Therefore the author would like to mention that bone cement is not necessary for the fixation between bone and prostheses. The JIKEI total knee prosthesis (universal type) based on the results of these experimental studies has been developed and was used to the clinical cases. The clinical results until four years after surgery have been most satisfactory with loss of pain, good supportability and movement of joints in almost all of the cases.

Adolescent↗
PubMed1997

[Is SnorEx also ApneaEx? A study with a new intra-oral prosthesis as a form of therapy of obstructive sleep apnea syndrome].

UNLABELLED: In recent years different kinds of dental devices have been advocated for treating sleep apnoea. In this study we report on our results with a kind of prosthesis ("Snor-Ex", DEPITA, 29336 Nienhagen) designed to relieve upper airway obstruction in sleep in pulling forward the tongue by a truss pad positioned in the posterior area of the tongue. We performed the study to test the effectiveness of the device in reducing the number of obstructive events. PATIENTS: 23 patients with OSA (22 male, age: 53.7 +/- 8.6 years, Body mass index: 31.1 +/- 3.9 kg/m2, Apnoea index: 33.5 +/- 18.4, Respiratory disturbance index: 45.6 +/- 19.7, mean apnoea duration: 20.4 +/- 4.4 sec) were included. STUDY DESIGN: Before the study was started, polysomnography was performed and the OSA associated symptoms/claims were standardised with the help of visual analogue scales (VAS). The prosthesis were made by the dental laboratory. Between the 28th and 42nd day after beginning with the study the patients had to come to the hospital for control. The effect of the therapy was documented only by a further polysomnography in patients who could sleep for at least 2.5 hours with the prosthesis. The effects of the device on changing OSA-associated symptoms and snoring were reevaluated by the above mentioned VAS. During the control the patients were divided into non-responders (NR) and responders (R) according to the results. RESULTS: The NR prevail in the study with 75% (17/23). They are characterised by inacceptable loco-regional side effects of the prosthesis, missing improvement of the state of daytime wellbeing and constant obstructive events. Only 25% of the patients are R. They locally tolerated the prosthesis, which is the precondition for long-term therapy. The severity of OSA diminished. Snoring also diminished significantly. CONCLUSION: According to our results the insufficient acceptance and the low effectivity of the SnorEx-prosthesis preclude large-scale indication for OSA patients. The prosthesis should not be prescribed without contacting a sleep lab.

Adult↗
PubMedDate not supplied

[Effect of prosthesis type and size on the hemodynamic response of mitral valve prostheses to exertion].

BACKGROUND: Doppler echocardiography is current tool for hemodynamic evaluation of mitral prosthetic heart valves. It's accepted that the area and the gradients by Doppler echocardiography are not influenced at rest by valvular type and valvular size. We evaluated the influence of valvular type, mechanical-biological, and size on exercise hemodynamic of normally-functioning mitral prosthesis. Thirty-seven patients with mitral prosthesis, mean age 56 +/- 10 years, underwent exercise Doppler echocardiography. Peak and mean prosthetic gradient were obtained at rest, during and at maximal exercise with a nonimaging transducer. Mechanical prosthesis were 23 and biological valves 14. Valvular size was less than 26 mm in 7 patients and more than 28 mm in 20 patients. Exercise increased the heart rate from 80 +/- 14 to 143 +/- 22 (p < 0.001), peak gradient from 11.4 +/- 4 to 26.1 +/- 7 mm Hg (p < 0.001) and mean gradient from 4.8 +/- 1 to 13.7 +/- 5 mm Hg (p < 0.001). We found similar peak (11.4 +/- 3 & 11.3 +/- 4) and mean gradient (3.4 +/- 1 & 2.9 +/- 0.7) at rest between mechanical and biological valves; at maximum exercise, peak (26 +/- 7 & 26 +/- 6) and mean gradient (13.9 +/- 6 & 13.2 +/- 4) were also similar. Prosthesis with > 28-mm-size compared with prosthesis < 26-mm-size showed minor peak gradient at second step (21.3 +/- 4 & 26.4 +/- 6, p < 0.05) and at peak exercise (25.4 +/- 7 & 29.8 +/- 8, ns). Hemodynamics on exercise using Doppler echocardiography was not influenced by valvular type (mechanical-biological) in normal mitral prosthesis. However, mitral prosthesis of small size showed worse on hemodynamics exercise than bigger ones.

Bioprosthesis↗
PubMed1995

Penile prosthesis insertion with corporeal reconstruction with synthetic vascular graft material.

Difficulty with penile prosthesis insertion may be encountered in patients with severe cavernous scarring or tunica albuginea deficiencies. Eleven patients who underwent penile prosthesis implantation required simultaneous corporeal reconstruction due to prior prosthesis infection and/or erosion in 6, priapism in 2 and Peyronie's disease in 1. One patient underwent prior neophallus construction with a tubularized abdominal wall flap for gender reassignment and 1 had congenitally deficient corporeal bodies. In 4 patients previous additional attempts at prosthesis replacement were unsuccessful. The reconstruction techniques included exposure of the corpora usually through a ventral midline incision and repair with synthetic vascular graft material. Accessory sub-coronal incisions were used when the disease was localized to the distal corpora. Six patients required reconstruction of more than half of the corporeal lengths bilaterally and in 5 smaller portions were repaired. Two patients received a semirigid and 9 an inflatable implant. Mean followup was 46 months (range 5 to 81). One patient required early reexploration for separation of the graft from the tunica and 2 required late surgical revision for distal tip divergence. Healing has been excellent and prosthesis function satisfactory in all patients. Infection, erosion and mechanical failure have not occurred. Penile prosthesis insertion with corporeal reconstruction using synthetic graft material is possible in these cases with acceptable morbidity rates and satisfactory erectile function.

Abdominal Muscles↗
PubMed1996

Numerical and experimental stress analysis of a polymeric composite hip joint prosthesis.

A comparative stress analysis of a polymeric composite hip joint replacement was performed. A prototype short carbon-fiber reinforced PEEK (CF/PEEK) prosthesis was manufactured by injection molding. Finite element (FE) analysis was conducted on intact femurs and femurs fitted with the CF/ PEEK and the titanium prostheses under various loading conditions. FE models were validated by experimental strain gauge measurements by using synthetic femurs. There was a good agreement between the two methods except in the hoop strain of the femur in the calcar region because of the assumption of the isotropic material properties. The stem stresses were lower for the CF/PEEK prosthesis than for the titanium prosthesis. The maximum stress was in the spigot of the CF/PEEK prosthesis, but in the middle third of the stem of the titanium prosthesis. Stress generated in the cement was almost equal for both prostheses although more load was transferred, via cement, to the femur with the CF/ PEEK prosthesis because the load transfer took place over a larger area. An out-of-plane component of the joint load causes higher prosthesis and cement stresses.

Benzophenones↗
PubMed1994

Effects of variation of prosthesis size on cement stress at the tip of a femoral implant.

With the resurgence of the use of bone cement in total hip arthroplasty, a renewed interest in techniques or designs that may reduce cement fixation failure has arisen. Analysis of the stresses at the tip of the prosthesis may suggest strategies to reduce loosening. This study analyzed stresses in the cement near the tip of a femoral component as a function of cement thickness, using a three-dimensional finite element model. A section of an idealized circular femoral shaft with implanted prosthesis and cement was modeled with loading conditions representing the stance phase of gait. Increasing cement thickness from 2 to 5 mm by reducing the prosthesis diameter from 15 to 9 mm is predicted to reduce stress significantly in the cement mantle of a femoral implant. Peak tensile stresses are reduced 45%, whereas peak von Mises and shear stresses are reduced 40%. Such a reduction in stress can increase fatigue life by an order of magnitude. Peak interface tensile stresses occur on the medial side at the tip of the prosthesis in a transverse direction, indicating likelihood of failure due to debonding. The shear and tensile stresses predicted by our model greatly exceed the fatigue endurance limit values for both bulk cement and the cement-prosthesis interface, indicating the likelihood of premature fatigue failure, even allowing for considerable uncertainty. These analytical results suggest that the surgeon should adopt a strategy of selecting a prosthesis that permits a 5-mm cement mantle near the tip of the prosthesis.

Bone Cements↗
PubMed1987

A physico-mathematical model for the human femur, with and without a prosthesis, under the static constraints of one-legged stance.

The authors present a physico-mathematical model of a human femur, under "monopodal" static constraints, using the finite elements method. Three examples are considered: a normal femur, a femur implanted with a short-stem prosthesis without cement, and a femur implanted with a long-stem prosthesis without cement. The lines of isoconstraints were compared in the three examples, as well as the main constraints (direction and intensity). From the results, the authors suggest that a prosthesis made of titanium is currently best even though its YOUNG's modulus differs from that of the bone. A prosthesis of composite material is possible in the future. While the intensity of the constraints is nearly the same at the level of the epiphysis for the short-stem and long-stem prosthesis it seems that the short-stem prosthesis fitted accurately without cement is the best solution. The introduction of a hip prosthesis modifies the normal curve of the loaded femur by changing the center of this curve.

Biomechanical Phenomena↗