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Total knee replacement with a variable axis knee prosthesis.

The Variable Axis Knee Prosthesis was designed to accommodate a wide range of problems in the knee and to minimize the complication of loosening. The results of the series, which now spans over seven years at this institution, have confirmed the effectiveness of the prosthesis in providing stability and firm fixation. Patellar alignment remains critical for optimum results. A wide variety of abnormalities, including failed prostheses, severe flexion contractures, arthrodesed knees, and severely osteoporotic bone, can be effectively managed utilizing this device. As with any other total knee prosthesis, the use of this prosthesis should be restricted to those knees with definite radiographic evidence of joint impairment in addition to significant symptoms. Relative contraindications include previous sepsis, neuropathic joint disease, and gross ligamentous incompetency. If these indications and limitations are adhered to, the results from knee replacement can be expected to equal or exceed those from total hip replacement over the long term.

Arthritis, Rheumatoid↗

[Long-term results of Insall's total condylar knee prosthesis (10-to-13-year follow-up)].

We have studied 10 to 13 years postoperatively the first 105 total knee arthroplasties using the Total Condylar, a semiconstrained prosthesis with sacrifice of the cruciate ligaments, inserted between 1979 and 1983, in 99 patients (6 were bilateral). The average age of these patients was 73.5 years at the time of arthroplasty. At the time of this review, 46 patients had died (49 prostheses) and 10 were lost to follow-up. Five knees had failed (4 infections), requiring prosthesis removal in three cases. The other 38 patients (41 knees) survived: 35 were available for detailed clinical and roentgenographic evaluation, 6 knees had only a clinical, x-ray, questionnaire or telephone evaluation. To evaluate the results of these prostheses, we used 3 different rating systems the SOFCOT rating system the Hospital for Special Surgery rating system the new scoring system of the Knee Society. The results with the HSS system were excellent or good in 80% of the cases. The rate of satisfactory results, somewhat lower than those of North American studies, is probably explained by the advanced age of our patients. All these prostheses were cemented. There was no aseptic loosening at 10 to 13 years follow-up. In assessing these results we can confirm the reliability of the first model of the Insall prosthesis, in spite of a small range of sizes, and of a rudimentary ancillary, which resulted in important positioning mistakes. We can confirm that a cemented knee prosthesis with sacrifice of the cruciate ligaments is reliable at more than 10 years of follow-up. The technical advancements: larger range of component sizes metal backed tibial plates better ancillary, which permits exact and reproducible placement posterially-stabilized system should yield even better long-term results, approaching those of total hip arthroplasty.

Adult↗

[Axillo-femoral bypass in the treatment of aorta prosthesis infection. A special case].

The authors report a case recently brought to their observation: T.A., a 77 year old patient, operated on in July 1990, for aortic aneurysm with axillo femoral by-pass. The patient was reoperated on the 5th day for ischaemic necrosis of the descending colon. In 1992 he was operated in another hospital for right iliac branch removal of the by-pass and performing of extra-anatomic bifemoral by-pass for right iliac branch infection of anatomic prosthesis. He was brought to our observation in March 1993, after the patient was refused in other Centres because of purulent abscess located near the aortic prosthesis and in the right iliac fossa, with a fistula to right superior anterior iliac crista. The patient was operated on in April 1993, with an explorative laparatomy to drain the abscess and to remove the aortic prosthesis. The aorta was sutured with closed bottom by means of delayed points. The postoperative course was regular and an arteriography performed three months after confirms the good running of the axillo-femoral by-pass and of the bifemoral one previously performed. The authors because of their experience and the bibliographical data underline the goodness of the axillo-femoral by-pass in serious infections of an aortic prosthesis.

Aged↗

Dacron fabric-enveloped alumina ceramic prosthesis for cementless resection arthroplasty of the proximal tibia: a case report with a long-term result.

After resection of the primary lesion, the right proximal tibia of a patient with osteosarcoma was reconstructed using a Dacron fabric-enveloped alumina ceramic total knee prosthesis without cement. Dacron fabric is intended to act as a scaffold upon which connective tissue can proliferate and form new ligament and other supporting soft tissues. Usually, following wide resection of the primary lesion, the supporting system is lost. If the supporting soft tissues are not reconstructed after removal of the tumor, they will be fixed in a slackened condition and will not provide sufficient support, leading to problems of stability and function. Using alumina ceramics alone does not induce surrounding connective tissue formation; therefore, stability is not ensured. The support of the vascular tissue enables the fabric to carry out the functions of ligaments, tendons, retinaculum, periosteum, joint capsule and other supporting soft tissues. Over time, stabilization occurs, biologic fixation of the prosthesis to the supporting soft tissues is successful and the durability of the prosthesis is prolonged. Postoperative follow-up has continued for a 77-month period. At present, the patient continues to show no evidence of disease and is able to walk painlessly up and down stairs without using a knee brace or handrail. A knee brace was recommended, however, to ensure the durability of the prosthesis. Dacron fabric is useful for the repair of supporting soft tissues without significant complications. Using this unique method, a stable, functional and aesthetically pleasing reconstruction can be accomplished.

Adult↗

A computer simulation of the plasma leakage through a vascular prosthesis made of expanded polytetrafluoroethylene.

We explored the blood-retaining mechanism of a vascular prosthesis made of expanded polytetrafluoroethylene through analysis of its structure and physicochemical properties. Plasma leakage through this vascular prosthesis was simulated by computer to explore its etiology. These examinations disclosed that leakage is dependent upon the inner pressure and the density of fibers. In other words, the study revealed that the mean distance between fibers constituting the wall of the expanded polytetrafluoroethylene vascular prosthesis is increased by tension (that is, inner pressure), resulting in an increased probability of leakage. It was additionally found that a thin membrane is formed on the polytetrafluoroethylene surface if blood in contact with the surface is dried. This membrane was found to reduce the water-repelling property of polytetrafluoroethylene and to make it impossible to preserve the inter-fiber liquid surface, thus causing leakage through the expanded polytetrafluoroethylene vascular prosthesis.

Blood Vessel Prosthesis↗

The effect of prosthesis-patient mismatch on aortic bioprosthetic valve hemodynamic performance and patient clinical status.

BACKGROUND: High pressure gradients occurring through normally functioning prosthetic valves appear to be related to a mismatch between the effective orifice area of the prosthesis and the patient's body surface area. OBJECTIVE: To determine whether prosthesis-patient mismatch affects clinical and hemodynamic status, a group of patients with a bioprosthetic heart valve in the aortic position was prospectively evaluated at 6.2+/-4.4 years after implantation by transthoracic Doppler echocardiography. METHODS: Manufacturer-derived in vitro valve areas were available in 61 patients allowing classification into two subgroups, with or without mismatch, based on a valve area at implantation indexed for body surface area 0.85 cm2/m2 or less, or greater than 0.85 cm2/m2. Clinical and hemodynamic parameters evaluated at follow-up included New York Heart Association (NYHA) class distribution, mean transprosthetic gradient, prosthetic valve area and cardiac index. RESULTS: Prosthesis-patient mismatch was present in 32 of 61 patients (52%). Although NYHA class of the patients was similar in both groups, hemo-dynamic performance of the aortic bioprostheses was worse in patients with mismatch than in patients with no mismatch, as indicated by a higher mean gradient (22+/-9 versus 15+/-8 mm Hg, P=0.002) and a lower cardiac index (3.0+/-0.7 versus 3.4+/-0.7 L/min/m2, P=0.04). The prevalence and severity of intrinsic prosthetic dysfunction were similar in both groups. Despite similar NYHA functional class distribution in both groups, the occurrence of syncope, acute pulmonary edema and angina pectoris was significantly higher in patients with mismatch (50% versus 21%, P=0.017). CONCLUSIONS: Prosthesis-patient mismatch is associated with worse hemodynamic performance and higher prevalence of adverse clinical events. However, mismatch did not promote accelerated hemodynamic or structural deterioration of the bioprosthesis.

Angina Pectoris↗

Unipolar or bipolar prosthesis for displaced intracapsular hip fracture in octogenarians: a randomised prospective study.

We performed a randomised prospective trial to compare a cemented unipolar prosthesis (Thompson) with a cemented bipolar prosthesis (Monk) in the treatment of displaced intracapsular fractures of the hip in patients over 80 years of age. Patients with a mental test score of less than 5/13 were excluded but the mortality was still about 30% at one year in both groups. We therefore feel that subjective criteria such as the level of pain and the return to the preinjury state are of paramount importance. Two years after operation there was no statistical difference between the rate of complications in the two groups. After adjusting for confounding factors such as differences in the level of function before injury between the groups, the degree of return to the preinjury state was significantly greater (p = 0.04) when using the unipolar prosthesis, which is one-quarter of the price of the bipolar. We cannot therefore justify the use of an expensive bipolar prosthesis in patients over 80 years of age.

Activities of Daily Living↗

[Septic infection of hip joint prosthesis with Listeria monocytogenes].

A case of Listeria monocytogenes septicaemia and infection of a prosthetic hip joint is presented in a patient with non-insulin-dependent diabetes mellitus. The patient developed the infection five and a half years after primary alloplastic operation. The prosthesis was removed and a temporary prosthesis with gentamicin was placed ("spacer"). The antibiotic treatment included ampicillin, pivampicillin and sulfamethoxazole-trimetroprim. Six weeks after removal of the prosthesis an un-cemented prosthesis was placed, and the patient had a full functional recovery.

Aged↗

CT-generated porous hydroxyapatite orbital floor prosthesis as a prototype bioimplant.

Hydroxyapatite bioceramic was used for the manufacture of an orbital floor prosthesis from spiral CT data acquired transaxially at 1-mm beam collimation, pitch of 1, and 0.2-mm reconstruction intervals. CT data were converted to vector file format for subsequent prosthesis manufacture on a stereo-lithography machine. The orbital floor prosthesis was engrafted onto an acrylic model of the orbit as a qualitative indication of its overall accuracy. High anatomic accuracy was achieved, as determined by visual inspection. Cross-hatching of the vector file data allowed a porous internal architecture of the prosthesis. Refinements in chemical structure of the hydroxyapatite bioceramic are expected to enhance mechanical properties.

Child↗

The use of an external vacuum device to augment a penile prosthesis.

Although penile prostheses are highly effective in the treatment of erectile dysfunction, a small percentage of patients are dissatisfied. Serendipitously, a patient in this group found that using an external vacuum device to augment his prosthetic erection provided a dramatic objective improvement in his erection and increased his overall satisfaction with intercourse. Patients who had tried the combination of external vacuum device and penile prosthesis simultaneously were identified from our penile prosthesis population as well as the Osbon Medical Systems database. Telephone interviews were conducted to determine efficacy, satisfaction, and side effects from the combination. Twelve patients completed the telephone survey. Four patients had semirigid and eight had inflatable penile prostheses. After using the vacuum device to augment the erection, all reported increased rigidity and patient/partner satisfaction, and 11 of 12 described improved length and girth. Minimal complications were noted. Concomitant use of an external vacuum device and penile prosthesis was safe in this select population. The combination may be indicated in patients with penile prostheses who are dissatisfied with size and/or rigidity, and in those who refuse or who are poor candidates for prosthesis revision.

Aged↗

Replacement of the proximal aorta and aortic valve using a composite bileaflet prosthesis and gelatin-impregnated polyester graft (Carbo-Seal): early results in 143 patients.

OBJECTIVE: We report the combined early results from two centers in the United Kingdom using a composite conduit consisting of a bileaflet mechanical valve incorporated into a gelatin-impregnated, ultra-low porosity, woven polyester graft (Carbo-Seal; Sulzer Carbomedics, Inc, Austin, Tex). METHODS: Between August 1992 and March 1997, 143 patients underwent aortic root replacement with the Carbo-Seal composite prosthesis. The indication for surgery was acute type A dissection in 31 (22%), chronic type A dissection in 9 (6%), ascending aortic aneurysm without dissection in 100 (70%), and false aneurysm of the ascending aorta in 3 (2%). Twenty-seven patients (19%) had undergone previous sternotomy, and 40 (28%) were seen as emergencies. Concomitant procedures were performed in 38 (27%), including 18 aortic arch or hemiarch replacements. Total follow-up is 270 patient-years. Follow-up is 100% complete. RESULTS: The early (30-day) mortality was 7% (10 patients). Permanent neurologic events occurred in 2%. At a mean follow-up of 23 months, 94% of survivors were in New York Heart Association functional class I. Freedom from reoperation was 97.2% +/- 1.6% (1 standard error [1 SE]) at 12 months and 95.7% +/- 2.2% at 48 months. Including early mortality, survival was 90.1% +/- 2.6% at 12 months and 83.1% +/- 3. 5% at 48 months. CONCLUSIONS: Aortic root replacement with use of the Carbo-Seal prosthesis can be undertaken with a relatively low early mortality and morbidity. A low reoperation rate and high intermediate-term survival can be expected, but continued follow-up is needed to determine the long-term efficacy of this prosthesis.

Aged↗

The Reverse Shoulder Prosthesis for glenohumeral arthritis associated with severe rotator cuff deficiency. A minimum two-year follow-up study of sixty patients.

BACKGROUND: Patients who have pain and dysfunction from glenohumeral arthritis associated with severe rotator cuff deficiency have few treatment options. The goal of this study was to retrospectively evaluate the short-term results of arthroplasty with use of the Reverse Shoulder Prosthesis in the management of this problem. METHODS: We report the results for sixty patients (sixty shoulders) with a rotator cuff deficiency and glenohumeral arthritis who were followed for a minimum of two years. Thirty-five patients had no previous shoulder surgery, whereas twenty-three had had either an open or arthroscopic rotator cuff repair, one had had a subacromial decompression, and one had had a biceps tendon repair. All patients were assessed preoperatively and postoperatively with the American Shoulder and Elbow Surgeons scoring system for pain and function and with visual analog scales for pain and function. They were also asked to rate their satisfaction with the outcome. The shoulder range of motion was measured preoperatively and postoperatively. RESULTS: The average age of the patients was seventy-one years. The average duration of follow-up was thirty-three months. All measures improved significantly (p < 0.0001). The mean total score on the American Shoulder and Elbow Surgeons system improved from 34.3 to 68.2; the mean function score, from 16.1 to 29.4; and the mean pain score, from 18.2 to 38.7. The score for function on the visual analog scale improved from 2.7 to 6.0, and the score for pain on the visual analog scale improved from 6.3 to 2.2. Forward flexion increased from 55.0 degrees to 105.1 degrees, and abduction increased from 41.4 degrees to 101.8 degrees. Forty-one of the sixty patients rated the outcome as good or excellent; sixteen were satisfied, and three were dissatisfied. There were a total of thirteen complications in ten patients (17%). Seven patients (12%) had eight failures, requiring revision surgery to another Reverse Shoulder Prosthesis in five patients (one shoulder had two revisions) and revision to a hemiarthroplasty in two patients because of deep infection. CONCLUSIONS: The data from this study suggest that arthroplasty with the Reverse Shoulder Prosthesis may be a viable treatment for patients with glenohumeral arthritis and a massive rotator cuff tear. However, future studies will be necessary to determine the longevity of the implant and whether it will provide continued improvement in function.

Adult↗

The reverse shoulder prosthesis for glenohumeral arthritis associated with severe rotator cuff deficiency. a minimum two-year follow-up study of sixty patients surgical technique.

BACKGROUND: Patients who have pain and dysfunction from glenohumeral arthritis associated with severe rotator cuff deficiency have few treatment options. The goal of this study was to retrospectively evaluate the short-term results of arthroplasty with use of the Reverse Shoulder Prosthesis in the management of this problem. METHODS: We report the results for sixty patients (sixty shoulders) with a rotator cuff deficiency and glenohumeral arthritis who were followed for a minimum of two years. Thirty-five patients had no previous shoulder surgery, whereas twenty-three had had either an open or arthroscopic rotator cuff repair, one had had a subacromial decompression, and one had had a biceps tendon repair. All patients were assessed preoperatively and postoperatively with the American Shoulder and Elbow Surgeons scoring system for pain and function and with visual analog scales for pain and function. They were also asked to rate their satisfaction with the outcome. The shoulder range of motion was measured preoperatively and postoperatively. RESULTS: The average age of the patients was seventy-one years. The average duration of follow-up was thirty-three months. All measures improved significantly (p < 0.0001). The mean total score on the American Shoulder and Elbow Surgeons system improved from 34.3 to 68.2; the mean function score, from 16.1 to 29.4; and the mean pain score, from 18.2 to 38.7. The score for function on the visual analog scale improved from 2.7 to 6.0, and the score for pain on the visual analog scale improved from 6.3 to 2.2. Forward flexion increased from 55.0 degrees to 105.1 degrees , and abduction increased from 41.4 degrees to 101.8 degrees . Forty-one of the sixty patients rated the outcome as good or excellent; sixteen were satisfied, and three were dissatisfied. There were a total of thirteen complications in ten patients (17%). Seven patients (12%) had eight failures, requiring revision surgery to another Reverse Shoulder Prosthesis in five patients (one shoulder had two revisions) and revision to a hemiarthroplasty in two patients because of deep infection. CONCLUSIONS: The data from this study suggest that arthroplasty with the Reverse Shoulder Prosthesis may be a viable treatment for patients with glenohumeral arthritis and a massive rotator cuff tear. However, future studies will be necessary to determine the longevity of the implant and whether it will provide continued improvement in function.

Adult↗

Composite hip prosthesis design. II. Simulation.

An investigation was performed to study the mechanical performance of fiber-reinforced composite hip prostheses. In Part I of the study, a three-dimensional finite element code was developed for analyzing a composite hip prosthesis in a femur. The material properties of the composite were treated as anisotropic and inhomogeneous while the properties of the femoral bone were treated as anisotropic and homogeneous. All the materials were assumed to behave linear-elastically. Thermoplastic graphite/PEEK material was selected for the study. No slippage was assumed at the interface between the implant and the surrounding femoral bone. In Part II, numerical simulations were performed using the code to study the performance of a composite prosthesis in the femur. The stress/strain distributions, micromotions, and strain energy density of the surrounding femoral bone were evaluated and found to be related to initial fixation and long-term stability of the prosthesis in the femur. Numerous fiber orientations were studied, and the results of the calculations were compared with those generated from a prosthesis made of cobalt chrome and Ti-6Al-4V titanium alloys. Based on the analysis, it was shown that compared to conventional metallic implants more favorable stresses and deformations could be generated in the femur using composite implants. In addition, by changing fiber orientations according to femoral loads, a composite implant could be designed specifically for the left or the right femur.

Computer Simulation↗

A single unit digital flexor tendon prosthesis.

Historically, the surgical repair of serious injuries to the flexor tendons of the hand have met with less than satisfactory clinical results. In an attempt to solve this problem, studies have been made on the design and testing of a Dacron polyester tendon prosthesis for complete replacement of the digital flexor tendon. The prosthesis attaches proximally at the anatomical musculotendon junction via collagen ingrowth into a fabric structure and in similar manner distally via bone ingrowth at the anatomical insertion site. These fabrics are continuous with the tendon body of the prosthesis consisting of an inextensible braided cord which is silicone rubber coated to prevent tissue adherence in the glide zone of the tendon bed. An added benefit of the prosthesis is a simple means of length adjustment which can easily be carried out on the operating table. Studies have been performed in both dogs and chickens which indicate that sufficient tissue ingrowth occurs at both the distal and proximal anastomoses for retention of full load bearing capability in these animals and that postoperative adhesions are negligible, if present at all. Full prostheses have been implanted in dogs for periods of over 1 year and chickens for 2 months. The chicken is the preferred animal model as a tendency for extensive scar tissue generation was shown in the dog. Both in vivo mechanical testing and histological characterization have been made on sacrificed animals which have received the full prostheses.

Animals↗

Effect of a cement-bone composite layer and prosthesis geometry on stresses in a prosthetically resurfaced tibia.

A comparative study of stress distributions in the component materials of a number of models of a prosthetically resurfaced tibia is presented. Although the geometry is idealized to be axisymmetric, the loadings for which the finite element analyses are performed are considered to be nonaxisymmetric, simulating more realistically the loading conditions in vivo. The different models are chosen with the view of determining the influence of changes in the prosthesis design on the induced stress distribution in the component materials. The changes considered are in the thickness of the cement and the cement-bone composite layers, and in the shape of the prosthesis. Experimentally measured values of strains are compared with the analytically predicted values to check the validity of the assumptions used in the finite element modeling. The comparison of induced stresses in the different materials reveals the desirability, from a mechanical behavior point of view, of introducing a cement-bone composite layer and using a prosthesis with domed subsurface in the fixation system. It is shown that for a model incorporating these features, considerable reduction of stresses in the cement, in its bulk and at its interface with the prosthesis plate, is achieved. The reduced stresses can be expected to have beneficial effects on the long-term behavior of the cement and its interfaces in the fixation system.

Bone Cements↗

Load transfer with the Austin Moore cementless hip prosthesis.

More than 1,300 Austin Moore hemiarthroplasties have been reviewed in the literature, with no reports of fracture of the stem. Many patients with these hip implants had good function. The lack of stem fractures in patients with good functions has not been explained and contrasts with stem fractures that have occurred in patients with cemented prostheses of other designs during the same time. We used three-dimensional finite-element analysis and free-body diagrams to explain the lack of fractures for this device by a description of the probable load-transfer mechanisms between the prosthesis and the bone. Results from our finite-element analysis indicate that, with good calcar-collar support, the stresses in the stem are small because the stem portion of the prosthesis and the bone are uncoupled and, consequently, do not share the resultant bending moment of the head and abductor forces. If the stem is coupled to the bone so that the resultant bending moment is shared, high stresses in the stem are predicted; such stresses are inconsistent with the complete absence of fractures of these prostheses. The results of the finite-element analysis further showed that loss of calcar-collar support with proximal fixation through the fenestrations resulted in high stresses in the stem and stress shielding of the proximal medial cortex. The uncoupled prosthesis also may be modeled with a free-body diagram as a three-force member loaded at the head, stem tip, and in the proximal region. With this model, it can be shown that the reaction force of the stem tip, and thus the peak bending stress in the stem, increases as calcar-collar support is decreased. If there is no calcar-collar support, proximal support must be provided by some combination of integration of bone in the fenestrations and wedging due to the lateral-medial taper of the device. Stresses in the stem are largest when there is no wedging, but high stresses develop in the cancellous bone in the fenestrations. When there is wedging, stresses in the stem can be low, but stresses in the supporting cancellous bone can be high; additional proximal support through the fenestrations substantially reduces these bone stresses. If reduced stresses in the cancellous bone are indicative of a stable device, these mechanisms indicate that fractures of the Austin Moore prosthesis have not occurred in normally loaded hips because load was transferred primarily either through the collar or by wedging, with additional support at the fenestrations.

Aged↗

A combined intra- and extra-articular reconstruction using a carbon-dacron composite prosthesis for chronic anterior cruciate instability. A two to six-year follow-up study.

Fifty patients with chronic symptomatic anterior cruciate insufficiency underwent ligamentous reconstruction using the "Westminster Composite Prosthesis" which consists of a central core of carbon fibre with an external weave of polyester. In 42 patients, the prosthesis was used as an augmentation within a tube of ilio-tibial tract, combined with a MacIntosh's extraarticular reconstruction. The prosthetic replacement alone was used in eight patients where there had been a previous extraarticular reconstruction and was associated with only fair results. The average age of the patients at operation was 28.5 years (range 18 to 50 years); instability of the knee had been present for a mean of 5.3 years and the average follow-up was 3.8 years (range 2 to 6 years). Assessment included subjective functional rating (Lysholm knee score) and clinical examination for instability. Thirty-seven patients (74%) had a good or excellent result, 11 (22%) had a fair result and two (4%) had a poor result. The Lachman test was grade I or less in 35 patients and the pivot shift sign was eliminated in 37 patients. Clinical signs of instability correlated well with the Lysholm knee score (p less than 0.001). Twenty-two unselected patients (44%) underwent an arthroscopic assessment and biopsy of the "neoligament" at an average of 10.4 months post-operatively. The prosthesis was found to be stable and well covered by a thick fibrous sheath ("neoligament") in 19 patients. The prosthesis was partially ruptured in two patients and completely disrupted in one. Thirty-two patients (64%) returned to their previous sports and 13 of them (26%) achieved their pre-injury level of performance.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗