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PubMed2001

No drainage does not increase complication risk after total knee prosthesis implantation: a prospective, comparative, randomized study.

Sixty patients were operated on for primary gonarthrosis by means of a cemented, posterior cruciate preserving total knee and were randomly allocated to postoperative drainage or nondrainage. The primary criterion was duration of hospital stay. Secondary criteria included serial evaluation of knee pain, knee flexion, knee circumference, calculated blood loss after 7 days, complications, reoperations, and the need for blood transfusions. There was no difference between the two groups in any of the criteria during the entire follow-up. There was a nonsignificant trend to a decreased calculated blood loss in the nondrained group and significantly less transfused blood units in the nondrained group. Lack of drainage does not increase complication risk after total knee prosthesis implantation. We therefore recommend using no routine drainage after this procedure.

Aged↗
PubMed2004

Fracture of the polyethylene tibial post in a NexGen posterior-stabilized knee prosthesis.

We reported a case of fracture of a polyethylene tibial post in a 44-year-old woman after 3 years of NexGen posterior-stabilized total knee arthroplasty (Zimmer, Warsaw, IN). Burnishing and delamination of the polyethylene was found around the breakage site of the post, especially over the anterior aspect of the post base. It indicated that the possible failure mechanism was the repeated anterior impingement between the metal femoral cam and polyethylene tibial post. After replacement of the broken insert, the patient obtained complete relief of previous symptoms. To our knowledge, this is the first report of post breakage of a NexGen posterior-stabilized knee prosthesis.

Adult↗
PubMed1980

Results with the constrained total knee prosthesis in treating severely disabled patients and patients with failed total knee replacements.

Fifty-fix constrained total knee replacements (forty Guepar and sixteen Herbert prostheses) were performed in forty-nine severely disabled arthritic patients and they were followed for two to four years. Seventeen of these knees were operated on to salvage a failed prosthesis. Good relief of pain was achieved in 64 per cent of the knees but there was less improvement in walking and function. The over-all range of motion increased because of a reduction in preoperative flexion contractures. The results in the salvage group were less successful than in those patients who underwent a primary operation. Between six months and one year postoperatively, pain had developed in 17 per cent of the fifty-six knees, 9 per cent had walking difficulties, and 7 per cent lost function. Patellofemoral pain accounted for the unfavorable pain ratings in over half of the knees. Zonal roentgenographic analysis of each knee indicated high incidences of radiolucent lines at the cement-bone interface (75 per cent), cement-metal lucencies (68 per cent), and cement deficiencies (73 per cent). Forty-three per cent of the knees showed excessive posterior placement of the prosthesis of more than five millimeters, resulting in flexion contractures of as much as 5 degrees. Complications requiring reoperation developed in nine knees (16 per cent). There was one case of loosening and three knees had deep infections. Chronic postoperative effusions were present in 48 per cent of the knees. The use of either a cemented metal-on-metal hinged knee replacement or a metal-on-polyethylene hinge type of prosthesis was found to result in a relatively high incidence of failures and complications, and did not solve the problem of treating patients with a failed knee prosthesis.

Adult↗
PubMed1990

Development of EMG-based mode and intent recognition algorithms for a computer-controlled above-knee prosthesis.

Conventional above-knee prostheses are unable to replace normal leg function due to the lack of adaptive control. Computer-controlled prostheses offer the possibility to implement such adaptive control. For a particular locomotion mode, control algorithms can generate appropriate damping profiles as a function of selected sensory inputs and stored information on normal walking. However, it is essential in such systems that the locomotor modes can be determined accurately from the inputs of the control system. Recognition of the intent to change from one mode to another is also a necessity because the control system has to account for such transitions. The possibility of using EMG signals from hip muscles and muscle residuals of the stump for this purpose is investigated. The modes tested are level walking, ramp ascent and ramp descent with slopes of 6 degrees and 9 degrees. EMG activity curves for three muscles: gluteus maximus, gluteus medius and tensor fasciae latae, are presented for the different modes. The results are obtained from two reference groups of 12 normal individuals and from a prosthetic patient. The results show the possibility of discriminating between modes. A discussion is made of the implementation of the results obtained by a finite state approach and the difficulties relating to the use of EMG signals for control purposes.

Algorithms↗
PubMed1985

The design of a model for a three dimensional stress analysis of the cement layer beneath the medial plateau of a knee prosthesis.

Factors which have influenced the design of a large scale model for an analysis of the strain in three dimensions of the cement layer beneath the medial plateau of a knee prosthesis are discussed. Materials were selected to model the medial tibial plateau, underlying cement and bone for a typical prosthesis and a two dimensional finite element analysis was used to indicate where the strain gauges should be embedded in the model.

Bone Cements↗
PubMed1987

Radiophosphate visualization of the foreign body reaction to wear debris from total knee prosthesis.

Three patients with total knee arthroplasties, in which the tibial and patellar articulating surfaces consisted of a polyethylene-carbon fiber composite, demonstrated technetium-99m methylene diphosphonate (MDP) deposition in the intraarticular space, whereas, the gallium-67 citrate images were normal. This was shown to be due to a synovial giant cell foreign body reaction to particulate carbon fiber debris in one patient who required surgical revision of the prosthesis.

Adult↗
PubMed1996

Radiographic wear assessment in a total knee prosthesis. 5- to 9-year follow-up study of 158 knees.

One hundred fifty-eight Porous-Coated Anatomic (Howmedica, Rutherford, NJ) primary total knee prostheses were evaluated clinically and radiographically to measure the remaining thickness of the plastic insert. Anteroposterior radiographs were taken with the beam guided parallel to the tibial plate by a fluoroscope. The knees were forced into varus and valgus, and the heights of the medial and lateral joint spaces, respectively, were measured with a digitizing table. Plastic insert wear could be calculated after correction with a magnification error factor, established by dividing the projected width of the tibial plate by the true size of the used component. After a mean follow-up period of 84 months (range, 58-116 months), wear was significantly higher for patients with osteoarthritis than rheumatoid arthritis and was 1.4 mm versus 0.7 mm medially (P < .0001) and 0.7 mm versus 0.4 mm laterally (P = .01). Wear was not correlated to thickness of the plastic insert or length of follow-up period. Young age or varus alignment contributed slightly to the amount of wear.

Age Factors↗
PubMed1997

-Knee prosthesis-.

The initial radiological assessment of knee osteoarthritis includes the evaluation of the osteochondral destruction, collateral ligament laxity and the determination of the position of the patella in both the axial and the sagittal planes and the femorotibial angulation in the coronal plane. The different types of knee prostheses are described. Post-operative radiological features of knee arthroplasties are discussed including normal findings and criteria of prosthesis instability and loosening.

Arthroplasty, Replacement, Knee↗
PubMed2003

Adhesion molecules in gonarthrosis and knee prosthesis aseptic loosening follow-up: possible therapeutic implications.

The involvement of the synovium is common in phlogistic processes of various joint diseases. Apart from synoviocytes and the other cells in the synovial tissue, circulating cells recruited from peripheral blood also participate in the phlogistic process. The increased expression of adhesion molecules on both circulating and endothelial cell surface may further this recruitment. We studied 15 patients affected by serious gonarthrosis requiring a prosthetic implant (GPI) and 7 with knee prosthesis aseptic loosening (KPL) to evaluate adhesion molecule expression and phlogistic infiltration in the synovium using immunohistochemistry and microscopic analysis. As control we studied 10 subjects affected by degenerative meniscopathies undergoing a selective arthroscopic surgical meniscectomy. Analysis with Kruskal-Wallis test showed no statistical significant differences in the expression of CD54, CD11a, CD11b and CD18 in three groups examined. The model of variance analysis (Friedman test), showed that CD54 expression is greater in patients with GPI and KPL in comparison with the other molecules. Adhesion molecules and their functions are important in arthropathies not only because their evaluation can allow us to identify the degree of inflammation and to predict its evolution, but also because pharmacological control of their expression could have important therapeutic implications.

Adult↗
PubMedDate not supplied

Novel route to fatigue-resistant fully sintered ultrahigh molecular weight polyethylene for knee prosthesis.

The role of entanglements in obtaining a homogeneous product of ultrahigh molecular weight polyethylene (UHMW-PE) has been explored. Studies performed in this report show that a disentangled state before melting is a prerequisite to obtain homogeneous products of an intractable polymer like UHMW-PE. The disentangled state is obtained directly from the reactor by controlling the polymerization conditions or in the solid state when there is enhanced chain mobility along the c axis of a unit cell. The disentangled state is maintained in the melt over a period of time, invoking implications in polymer rheology. This approach is applicable to polymers in general. The homogeneous fully sintered UHMW-PE, obtained for the first time, shows a considerable decrease in oxygen permeability and an increase in toughness and fatigue resistance. Such homogeneous products of UHMW-PE are beneficial in highly demanding applications, especially in knee prosthesis, where the polymer is used as an inlay between the human bone and a metal or ceramic part, which slides against the polyethylene component during normal gait.

Knee Prosthesis↗
PubMed2003

Results of rotating-platform, low-contact-stress knee prosthesis.

Low-contact-stress (LCS) rotating-platform knee arthroplasties in 31 consecutive patients with 50 deformed knees were evaluated at a mean follow-up of 4.5 years (range, 4-6 years). Overall results were good in 72% of 22 osteoarthritic knees and 71.4% of 28 rheumatoid knees. None of the knees showed any change in component position and alignment, osteolysis, or cement-bone radiolucency during follow-up. LCS prosthesis takes care of some rotational component mismatch. Complications included 2% dislocation, 4% anteroposterior instability, and 10% subluxation of the rotating platform. The overall reoperation rate of 10% was significantly higher than reported for the fixed bearing series, and we feel that LCS prosthesis is unsuitable for severely deformed knees.

Arthritis, Rheumatoid↗
PubMed2002

99m Tc-ciprofloxacin (Infecton) imaging in the diagnosis of knee prosthesis infections.

The purpose of this study was to evaluate the usefulness of 99mTc labelled ciprofloxacin imaging in detecting the presence of infection in patients with symptomatic knee prostheses. Among 16 randomly selected patients of whom seven had infection based on clinical and microbiological findings and nine did not, 99mTc-ciprofloxacin images were obtained at 1, 4 and 24h after the injection of the tracer. While there was some diffuse non-specific accumulation of 99mTc-ciprofloxacin in large synovial joints and in prosthetic knee joints, the infected knee prostheses were found to show more intensive focal uptake, which also extended outside the synovial cavity. The infection related uptake remained visible in the 24h images, whereas non-specific uptake had a fading tendency at this time point. 99mTc-ciprofloxacin imaging showed diagnostic sensitivity of 86% and a specificity of 78% for correctly classifying the presence of infection. The data indicate that 99mTc-ciprofloxacin imaging may be used in the diagnosis of knee prosthesis infections. Infection-related uptake remains visible in the 24h images and is typically found also outside the synovial cavity, which should be noted in the evaluation of the images.

Aged↗
PubMed1989

Salvage of jeopardized total-knee prosthesis: the role of the gastrocnemius muscle flap.

Total-knee arthroplasty has provided many patients with excellent long-term functional results. However, exposure of a total-knee replacement usually eventuates in failure. The relatively superficial location of the prosthesis, the need for early active motion, previous surgical incisions, and a variety of systemic factors may militate against early wound healing. Restoration of well-vascularized soft-tissue cover can salvage an otherwise disastrous situation. The authors recommend early operative intervention upon observation of wound breakdown, devitalized skin edges, or significant subcutaneous infection leading to necrotic overlying skin. The operative procedure found to salvage the majority of prostheses consists of adequate debridement, antibiotic irrigation (of the joint, if exposed), and coverage with a well-vascularized muscle flap, preferably the medial gastrocnemius muscle. The operative technique and ultimate long-term outcome are reviewed based on experience with 10 consecutive patients presenting with a jeopardized knee prosthesis. Follow-up ranged from 1 to 6 years. Representative case histories are presented.

Adult↗
PubMed2000

Kinematic analysis of total knee prosthesis designed for Asian population.

In designing a total knee replacement (TKR) prosthesis catering for the Asian population, 62 sets of femur were harvested and analyzed. The morphometrical data obtained were found to be in good agreement with dimensions typical of the Asian knee and has reaffirmed the fact that Caucasian knees are generally larger than Asian knees. Subsequently, these data when treated using a multivariate statistical technique resulted in the establishment of major design parameters for six different sizes of femoral implants. An extra-small implant size with established dimensions and geometrical shape has surfaced from the study. The differences between the Asian knees and the Caucasian knees are discussed. Employing the established femoral dimensions and motion path of the knee joint, the articulating tibia profile was generated. All the sizes of implants were modeled using a computer-aided software package. Thereupon, these models that accurately fits the local Asian knee were transported into a dynamic and kinematic analysis software package. The tibiofemoral joint was modeled successfully as a slide curve joint to study intuitively the motion of the femur when articulating on the tibia surface. An optimal tibia profile could be synthesized to mimic the natural knee path motion. Details of the analysis are presented and discussed.

Aged↗