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

An alternative bent-knee prosthesis.

Prosthetic fitting in patients with below-knee amputations and concurrent knee flexion contractures poses inherent difficulties to the prosthetic rehabilitation team. The standard bent-knee prosthesis is bulky and awkward. It treats the patient functionally as a knee disarticulation and yields no potential for improving the patient's degree of contracture. This paper describes a case report with an alternative to the bent-knee prosthesis that not only offered improved function relative to the standard bent-knee prosthesis, but also acted therapeutically by reducing the patient's knee-flexion contracture.

Amputation, Surgical↗
PubMed1990

Knee motion in total knee arthroplasty. A roentgen stereophotogrammetric analysis of the kinematics of the Tricon-M knee prosthesis.

The three-dimensional kinematics of the Tricon-M knee prosthesis during active knee flexion and extension were recorded in 11 patients with arthrosis or rheumatoid arthritis using roentgen stereophotogrammetric analysis. Twenty-three normal knees constituted the control group. The prosthetic knees displayed the same degrees of freedom regarding rotational and translational movements as the normal knees, although the kinematics were different. A combination of internal rotation, abduction, and lateral translation of the tibia was recorded during flexion, and the reversed movements were recorded during extension. During the first 25 degrees of flexion, these movements were small, reflecting the high congruency between the articular surfaces, while beyond 25 degrees they increased. The normal knees displayed a combination of internal rotation, adduction, and medial translation of the tibia during flexion and the reversed movements during extension. The prosthetic knees also exhibited an increased posterior displacement during increasing flexion when compared with the normal knees. There was a correlation between the positioning of the femoral component in the sagittal plane and the recorded anterior/posterior translations. In conclusion, the kinematics of the Tricon-M knee prosthesis significantly differ from the normal knee, probably because of the design of the prosthesis and the absence of the cruciate ligaments.

Aged↗
PubMed2005

[Procedures for treatment of joint mechanics impairment in the rotating Endo-model knee prosthesis].

In cases of mechanical damage of the Endo model rotating knee prosthesis, it is not necessary to change the complete prosthesis. Isolated replacement of the mechanics is possible. We changed a sled prosthesis of a 66-year-old patient to a rotating knee prosthesis because of ligament instability. After the patient fell and traumatized the operated knee, she experienced pain during weight bearing and instability. Because clinical and fluoroscopic examinations verified instability of the prosthesis, we decided to change the mechanics of the rotating knee prosthesis. In conclusion, mechanical damage of a rotating knee prosthesis is a rare complication. Operative treatment is easy to manage if replacement parts and instruments to change the mechanics have been organized preoperatively.

Aged↗
PubMed2004

[Medial unicompartmental knee prosthesis for patients with unicompartmental gonarthrosis].

The function and survival time of unicompartmental knee prostheses for patients with severe gonarthrosis have been improved the past few years by developments in their design, the instrumentarium and the surgical technique. A medial unicompartmental knee prosthesis may be indicated in patients with arthrosis of the medial tibiofemoral compartment. The prerequisites are an intact anterior cruciate ligament, an intact lateral compartment, a correctable varus axis and sufficient flexion in the knee. Contraindications are inflammatory arthropathies and a recent episode of septic arthritis. Relative contraindications are: old age, excess body weight, patellofemoral arthrosis and chondrocalcinosis. A unicompartmental knee prosthesis can be placed via a small parapatellar incision. The postoperative recovery is more rapid than following the classical open approach, while the knee function after 5 years is comparable. The knee function also seems better following a medial unicompartmental knee prosthesis than after valgusising tibial head osteotomy. The latter is still preferred for young active patients. Medial unicompartmental knee prostheses fail in 6-8% of patients. Revision to a total knee prosthesis is then the treatment of choice. In the long term, unicompartmental prostheses with a mobile bearing become loose less often than comparable prostheses with a fixed bearing.

Arthroplasty, Replacement, Knee↗
PubMed1991

Total knee arthroplasty using the total condylar III knee prosthesis.

Twenty-seven total knee arthroplasties (TKAs) were performed in 24 patients using the total condylar III knee prosthesis (TCP III) and were evaluated clinically and radiographically with a mean follow-up period of 4 years. Eighteen were revision TKAs, and nine were primary knee arthroplasties. Evaluations were made using the Hospital for Special Surgery (HSS) knee scale as well as the Knee Society radiographic evaluation method. Clinical results for all knees were 11% (3 of 27) excellent, 70% (19 of 27) good, 15% (4 of 27) fair, and 4% (1 of 27) poor. The one poor rating resulted from an intraoperative vascular injury. The results showed no statistical difference between revision and primary TKA. After operation, pain relief, range of motion, walking, function, and activity level improved in both the primary and revision patients. Radiolucencies 2 mm or greater in width were found in 6 of the 27 tibial components, in none of the 27 femoral components, and in 1 of the 19 patellar components. Only two tibial implants showed progressive radiolucencies. No correlation was found between the radiographic position of the implants and the clinical results. The authors conclude that the TCP III is a satisfactory choice for TKA in selected knees in which there is significant instability and in which intramedullary fixation is required.

Adult↗
PubMed1981

Results of the total-condylar knee prosthesis.

The Total-Condylar knee prosthesis is a non-hinged, semi-restricted prosthesis with partial intrinsic stability, incorporating a prosthetic surface covering the patella. The surgical technique involved includes release of the contracted soft tissues, so as to obtain symmetry and balance of the ligaments before the bone is cut. These bone cuts are made at a right angle to one another and are standardised. The cases presented comprise forty-eight knees (in forty-one patients), of whom thirty-eight were affected by arthrosis and ten by rheumatoid arthritis. The mean age of the patients was sixty-five years. They were examined not less than twenty-four months nor more than seventy months after operation. This was a prospective survey and the cases were consecutive. Excellent or good results were obtained in 89.5 per cent of cases. Only one case had to undergo re-operation, due to loosening of the tibial component, not to deep infection. The results were permanent over the review period, and the quality was as good as in prostheses of the hip.

Aged↗
PubMed1983

Total knee-replacement arthroplasty. Results with the intramedullary adjustable total knee prosthesis.

One hundred and thirty knees (112 patients) in which the intramedullary adjustable total knee prosthesis was inserted were followed for four to nine years. This prosthesis is designed to permit unconstrained rotation and includes a metal tray supporting the high-density-polyethylene tibial component as well as an intramedullary stem and two condylar intramedullary projections on both the femoral component and the tibial component. Using a rating system in which pain, function, stability, and motion each was graded independently on a scale of 1 to 6, the preoperative scores were 73 per cent poor and 27 per cent fair, while the postoperative scores were 77 per cent good, 15 per cent fair, and 8 per cent poor. If only the patients with unilateral or bilateral involvement of the knee without other functional disabilities were considered, four to nine years after the arthroplasty 92 per cent could be classified as good; 5 per cent, as fair; and 3 per cent, as poor. There were two deaths (one due to pulmonary embolism and the other, to overwhelming sepsis after attempted arthrodesis for a deep would infection) and five deep infections, four of which necessitated reoperation for arthrodesis. In addition, reoperations were necessary in five other knees: in two for secondary closure of the wound, in one for evacuation of a hematoma, in one for synovectomy and skin-grafting because of infection, and in one for recentralization of the patella. At final evaluation, 117 knees had radiographs of sufficiently good quality for assessment, and thirty-seven (32 per cent) of these showed evidence of a nonprogressive radiolucent line about the tibial component. In addition, two were considered clinically loose (one due to a traumatic injury and the other, to malpositioning of the tibial component).

Adult↗
PubMed2005

Change in UHMWPE properties of retrieved ceramic total knee prosthesis in clinical use for 23 years.

The alumina-ceramic total knee prosthesis developed by Kyocera Corp. was implanted in 1979, and was in clinical use for 23 years until total knee arthroplasty revision surgery in January 2002. It is believed that this is the longest clinical period of a ceramic total knee prosthesis reported to date in the world. In the present study, we gave consideration to the long-term clinical stability of the alumina-ceramic femoral component as well as the mechanism of in vivo degradation of ultrahigh molecular weight polyethylene (UHMWPE) based on the evaluated wear, oxidation, and fracture toughness of the retrieved UHMWPE. We concluded that the degradation of UHMWPE by progressive oxidation is an issue to be solved in the future. To moderate stress concentration, use of a thin UHMWPE insert should be avoided. The low wear rate and the mild wear pattern observed this time suggest the possibility of reduced wear of the UHMWPE against the alumina-ceramic femoral component, and the usefulness of the alumina-ceramic total knee prosthesis component was recognized even after long clinical use.

Ceramics↗
PubMed2004

Contact stresses and fatigue life in a knee prosthesis: comparison between in vitro measurements and computational simulations.

The evaluation of contact areas and pressures in total knee prosthesis is a key issue to prevent early failure. The first part of this study is based on the hypothesis that the patterns of contact stresses on the tibial insert of a knee prosthesis at different stages of the gait cycle could be an indicator of the wear performances of a knee prosthesis. Contact stresses were calculated for a mobile bearing knee prosthesis by means of finite element method (FEM). Contact areas and stresses were also measured through in vitro tests using Fuji Prescale film in order to support the FEM findings. The second part of this study addresses the long-term structural integrity of metal tibial components in terms of fatigue life by means of experimental tests and FEM simulations. Fatigue experimental evaluations were performed on Cr-Co alloy tibial tray, based on ISO standards. FEM models were used to calculate the stress patterns. The failure risk was estimated with a standard fatigue criterion on the basis of the results obtained from the FEM calculations. Experimental and computational results showed a positive matching.

Computer Simulation↗
PubMed1991

Optimal control for the active above-knee prosthesis.

Control of an active above-knee prosthesis has been simulated for a selected gait activity using a hierarchical closed-loop method. An extension of finite-state control, referred to as artificial reflex control, was adopted at the strategic level of control. At the actuator level of control an optimal tracking method, based on dynamic programming, is applied. This deals mainly with the actuator level of control, but considers the interaction of the leg dynamics and the switching effects of artificial reflex control. Optimal tracking at the actuator level of the above-knee prosthesis reduces the on-off effects of finite-state methods, such as artificial reflex control. The proposed method can also be used for the design of prosthetic elements. Specific attention is paid to the limited torque and power in the prosthetic joint actuator, which are imposed by the principle of self-containment in the artificial leg. The hierarchical structure, integrating artificial reflex control and optimal tracking, can be used in real time, as estimated from the number of computer operations required for the suggested method.

Artificial Limbs↗
PubMed2002

[In situ connection of a hollow intramedullary nail to the stem of a knee prosthesis in periprosthetic fracture].

Periprosthetic fractures often reveal problems and complications because of poor bone quality. A case report is presented, in which a hollow intramedullary nail was connected, in situ, with the stem of a knee prosthesis (Blauth knee). Two plate osteosyntheses had previously failed. As ultima ratio, a hollow intramedullary nail was placed antegrade on the stem of the knee prosthesis. Afterwards excellent callus formation developed and resulted in consolidation.

Aged↗
PubMed2001

The influence of inserting a Fuji pressure sensitive film between the tibiofemoral joint of knee prosthesis on actual contact characteristics.

OBJECTIVE: To investigate the influence of inserting a Fuji pressure sensitive film between the tibiofemoral joint of knee prosthesis on actual contact characteristics. DESIGN: A finite element analysis was used to investigate the alteration of contact characteristics of the tibiofemoral joint due to inserting a pressure sensitive film between the contacting surfaces. BACKGROUND: The discrepancy between actual contact behaviors of tibiofemoral joint of knee prosthesis and the measurement using Fuji pressure sensitive film was not discussed extensively. The change of direct contact circumstance of the tibiofemoral joint due to inserting a pressure sensitive film was not well reported. METHOD: A two-dimensional finite element model of the tibiofemoral joint of knee prosthesis in the sagittal plane was constructed. Four different radii of the femoral component were used to investigate the conformity effect. Two-layers of plane strain element were used to model the pressure sensitive film. The influence of inserting a pressure sensitive film on the actual contact characteristics was analyzed by comparing the results of the change in contact radius. RESULTS: Inserting a pressure sensitive film between contacting surfaces would disturb the original contact behaviors, especially in the lowest conformity design. The maximum difference of contact radius between the model simulating actual contact circumstance and the model with inserting a pressure sensitive film between contacting surface was 77% in the lowest conformity condition at the smallest load. CONCLUSIONS: This study proposes a quantitative analysis of contact characteristics in the tibiofemoral joint of knee prosthesis between the models with and without inserting a pressure sensitive film into the contact surface. The measurement of contact area in artificial tibiofemoral joints by using Fuji pressure sensitive film is always overestimated its true contact area by 14-77%. RELEVANCE: This study revealed the measurement of contact characteristics of artificial tibiofemoral joints by using Fuji pressure sensitive film which depends on not only the applied load, but also the conformity and material properties of the contact surface. Therefore, the information of the conformity and material properties of the contact surface should be provided as well as the applied load wherever a measurement of contact characteristics using Fuji pressure sensitive film is analyzed and interpreted.

Biomechanical Phenomena↗
PubMed1984

The posterior cruciate condylar total knee prosthesis. A five-year follow-up study.

Remarkable results were demonstrated for the nonlinked, semiconstrained total condylar knee prosthesis in the first long-term follow-up study. The posterior cruciate condylar prosthesis, a variation of the basic design, leaves the posterior cruciate ligament intact. Ninety-four consecutive knees were observed for a minimum postoperative follow-up period of five years. Apart from this design modification and a slightly different program of postoperative care, the methods and techniques used were identical to those used with the total condylar knee prosthesis. By the same method of assessment (The Hospital for Special Surgery Knee Rating Scale), 54 of the ninety-four knees (57.4%) were rated excellent; 37 (39.4%), good; two (2.1%), fair; and one (1.0%), poor. The average preoperative score was 48 points, and the average postoperative score was 81 points (85-100 points = excellent). The posterior cruciate condylar total knee prosthesis represents an excellent prosthetic design for a wide variety of knee deformities and maintains the posterior cruciate ligament for supplementary posterior support.

Adult↗
PubMed1986

The influence of tibial-patellofemoral location on function of the knee in patients with the posterior stabilized condylar knee prosthesis.

Function of the knee and patellofemoral symptoms were correlated with the position of the implant in 101 consecutive patients with 116 posterior stabilized condylar knee prostheses. All of the patients were followed for a minimum of two and a half years with sequential physical examinations, radiographs, and functional evaluation of the knee. In sixteen knees (14 per cent), clicking or catching of the patella in terminal extension or painless crepitation throughout the arc of flexion developed without lowering the functional knee-evaluation score. Pain or mechanical problems, or both, that lowered the functional knee-evaluation score occurred in another fourteen knees (12 per cent), within the first postoperative year. Of these fourteen, eight required revision solely for patellofemoral complaints. Critical analysis of the tibial-patellofemoral mechanical axis identified three surgical variables that were found to markedly affect the functional result of the prosthesis: the distance from the center line of the tibial prosthesis to the center line of the tibial plateau, a change in the position of the joint line of the prosthesis relative to the hip and ankle, and the patellar height, measured as the perpendicular distance from the inferior pole of the patellar implant to the joint line of the prosthesis. Functional knee scores, range of motion, patellofemoral pain or mechanical symptoms, the need for revision, and the necessity of manipulation could all be statistically significantly correlated with the three independent variables. In addition, a range of neutral alignment was developed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

The "caviar" madreporic knee prosthesis.

The madreporic ("caviar") prosthesis is a hinged knee prosthesis that can be inserted without the use of cement. The surfaces of the intramedullary stems are constructed with contiguous spheres one mm in diameter. These spaces are filled by bone trabeculae and haversian bone, providing permanent biologic fixation. Experimental madreporic knee arthroplasties in dogs show that bone probes these surfaces and produces solid attachments. Histologically, the trabeculae remain separated from the metal by a fine layer of fibrous tissue. The method of insertion of the prosthesis is simple. Preparing the epiphyses before any bone resection avoids the possibility of rotational positioning errors. The form of the intramedullary stems offers good positioning in the frontal plane. The analysis of an initial series of 15 cases shows results that are far from outstanding. The 2 deaths, the 2 cases of sepsis, and the recuperation of only mediocre motion can be explained, at least in part, by the advanced age of the patients and the poor bone quality of the rheumatoid patients. Nevertheless, this type of prosthesis has 2 important advantages. It avoids the complications from the use of acrylic cement and allows for a revision operation for cases of failed surface replacement designs. Obviously further experimentation with noncemented designs will continue and definitive studies will be reported later.

Animals↗