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At least 487 records · Page 27Linked to original sources
PubMed1998

Intraoperative assessment of tibiofemoral contact stresses in total knee arthroplasty.

The production of polyethylene wear debris in total knee arthroplasty (TKA) is due to multiple factors. In particular, inadequate implant alignment and high bearing surface contact stresses are associated with polyethylene failure. Optimal implant placement and soft tissue balancing may contribute to reducing wear and the production of polyethylene particles. We present a case in which a quantitative technique was used to measure tibiofemoral contact stresses during implantation of a total knee prosthesis in vivo. In a knee with preoperative varus and fixed flexion deformity, medial compartment contact stresses after initial resection were reduced from 14.3 MPa to 11.3 MPa in neutral alignment by additional bone resection. Posterior cruciate release was required to reduce contact stresses further and to provide satisfactory balance between medial and lateral compartments, as determined by the operating surgeon, and was confirmed by the measurement system (3.8 MPa medially; 3.0 MPa laterally). This technique has potential to fine-tune implant positioning and ligament balancing during TKA.

Aged↗
PubMedDate not supplied

[Knee resection prosthesis in tumor reconstructive surgery: comparative study between the use of cryopreserved bone allografts and non-biologic material].

From july 1983 to december 1990, 34 patients with aggressive or malignant bone tumors in the knee have been treated by radical resection and endoprosthesis replacement with or without allograft. The follow up was three years. We have a comparative study between allograft and plastic spacer. The functional character is better with endoprosthesis with non biologic material (75% excellent and good versus 66.6%). The complications were similar in both.

Adolescent↗
PubMed2005

Can normal knee kinematics be restored with unicompartmental knee replacement?

BACKGROUND: Unicompartmental replacement can be an alternative to tibial osteotomy in younger, active patients with unicompartmental knee disease. In unicompartmental replacement, the other compartments and knee ligaments are largely untouched. Therefore, it was hypothesized that the knee kinematics after unicompartmental replacement may also be unchanged. To test this hypothesis, knee kinematics and quadriceps tension were recorded before and after replacement with a unicompartmental design and then with a tricompartmental design. METHODS: Six human cadaver knees were tested before implantation, after implantation with a bicruciate-retaining unicompartmental knee prosthesis, and after implantation with a posterior cruciate-retaining tricompartmental knee prosthesis. The unicompartmental prosthesis was initially implanted, and it was then revised to a total condylar knee replacement. The knee kinematics were measured with use of an electromagnetic tracking device while the knee was put through dynamic simulated stair-climbing under peak flexion moments of approximately 40 N-m. Quadriceps tension was also measured for all three conditions. RESULTS: No significant differences in tibial axial rotation were noted between the intact and unicompartmental conditions. However, tricompartmental replacement significantly affected tibial axial rotation (p = 0.001). Femoral rollback was not significantly affected by either unicompartmental or tricompartmental arthroplasty. Quadriceps tension was also similar among all three conditions. CONCLUSIONS: In this in vitro cadaver study, the tricompartmental replacement significantly changed knee kinematics while the unicompartmental replacement preserved normal knee kinematics.

Aged↗
PubMed1991

Survivorship of the Total Condylar I prosthesis: Results of a series of 100 total knee arthroplasties.

The Total Condylar knee prosthesis was employed at our institution from April 1975 to October 1986; currently the posterior stabilized type is in use. The results of 100 knee arthroplasties using the Total Condylar I prosthesis, 83 of which were reviewed after an average of 7 1/2 years (maximum 14), were rated good or excellent in 82% of the subjects. Three cases were considered failures due to infection or aseptic loosening. According to the survivorship analysis, there is a 14-year success rate of 93%.

Aged↗
PubMed2003

Polyethylene wear particles in synovial fluid after total knee arthroplasty.

The aims of the current study were to examine polyethylene particles in synovial fluid at an early stage, and to compare a newly introduced medial pivot total knee prosthesis with an established posterior-stabilized total knee prosthesis. Synovial fluid was obtained 1 year after knee arthroplasty from 17 patients with well-functioning prostheses (22 knees, 11 posterior-stabilized prostheses and 11 medial pivot prostheses) under complete sterile conditions. Polyethylene particles were isolated and analyzed by scanning electron microscopy. Particle size (equivalent circle diameter) was 0.78 +/- 0.08 microm (mean +/- standard error) in posterior-stabilized prostheses and 0.67 +/- 0.06 microm in medial pivot prostheses. Particle shape (aspect ratio) was 2.30 +/- 0.22 in posterior-stabilized prostheses and 1.90 +/- 0.16 in medial pivot prostheses. The total numbers of particles were 1.16 +/- 0.57 x 10(8) in posterior-stabilized prostheses and 9.01 +/- 2.95 x 10(6) in medial pivot prostheses. Particles were smaller and rounder in medial pivot prostheses than in posterior-stabilized prostheses, but the differences were not significant. The difference in the common logarithm of particle number was significant. The medial pivot prosthesis generated less wear particles than the posteriorstabilized prosthesis, and these findings may have an impact on the incidence of osteolysis and aseptic loosening.

Arthroplasty, Replacement, Knee↗
PubMed2000

The PROSTALAC functional spacer in two-stage revision for infected knee replacements. Prosthesis of antibiotic-loaded acrylic cement.

The PROSTALAC functional spacer is made of antibiotic-loaded acrylic cement but has a small metal-on-polythene articular surface. We have used it as an interim spacer in two-stage exchange arthroplasty for infected total knee replacement. PROSTALAC allows continuous rehabilitation between stages as it maintains good alignment and stability of the knee and a reasonable range of movement. It also helps to maintain the soft-tissue planes, which facilitates the second-stage procedure. We reviewed 45 consecutive patients, treated over a period of nine years. The mean follow-up was for 48 months (20 to 112). At final review, there was no evidence of infection in 41 patients (91%); only one had a recurrent infection with the same organism. There was improvement in the Hospital for Special Surgery knee score between stages and at final review. The range of movement was maintained between stages. Complications were primarily related to the extensor mechanism and stability of the knee between stages. Both of these problems decreased with refinement of the design of the implant. The rate of cure of the infection in our patients was similar to that using other methods. Movement of the knee does not appear to hinder control of infection.

Adult↗
PubMed1996

[Use of ultrasound for the removal of cement in hip prosthesis reoperations].

PURPOSE OF THE STUDY: One of the challenges facing the surgeon during revision procedures is the harduous task of complete acrylic cement removal while leaving the surrounding cortical bone intact. A set of ultra sonic driven instruments has been evaluated revisions of total hip and total knee prosthesis. The principle is to convert standard electrical energy into mechanical energy via an ultrasonic transducer. MATERIAL: 10 revisions of cemented hip prosthesis and one of a total knee prosthesis (Guepar Howmedica) have been performed with success easily and safely. RESULTS: The ultra-sonically driven tools used have reduced the incidence of perforation (1 cases), with no need to cut cortical windows to remove the distal plug, and have also reduced the time for cement removal and the intra-operative blood loss. CONCLUSION: The author thinks that this technique provides a great facility in revision surgery. A larger study will be done soon.

Bone Cements↗
PubMed2006

Tibial slope and high tibial osteotomy using the circular external fixator.

Alteration of tibial slope is one of the important anatomical changes of the proximal tibia after high tibial osteotomy. Increased or decreased tibial slope can effect further total knee prosthesis procedure. In this retrospective study, 18 knees of 17 patients (17 female, mean age 51 range 43-61, mean BMI is 33.6 +/- 4.6 kg/m2) who were applied high tibial osteotomy using circular external fixator due to medial compartment arthrosis of the knee were evaluated in terms of tibial slope changes. While mean correction about 12.3 degrees in mechanical femoro-tibial angle was obtained in frontal plan (P = 0.0001), significant change in tibial slope was not determined in sagittal plan (P = 0.127). The mean posterior proximal femoral angle values were measured as 79.5 +/- 2.1 degrees preoperatively and as 80.3 +/- 2.7 degrees postoperatively and found to fall into the normal range (80.4 +/- 1.6 degrees). As there is no significant alteration in tibial slope after high tibial osteotomy performed with the Ilizarov system, complications due to alteration in tibial slope will not be experienced in follow-up or in further total knee prosthesis procedure.

Adult↗
PubMed1989

Bone ingrowth into the tibial component of a canine total condylar knee replacement prosthesis.

The purpose of this study was to evaluate the occurrence of bone ingrowth in a porous coated tibial component of a canine total condylar design knee replacement model. The entire undersurface of the tibial prosthesis was covered by a titanium fiber metal porous composite pad. Projecting from this surface were three short, cylindrical, fiber metal coated pegs that along with a posterior screw provided initial stabilization of the device. Left total knee replacements were performed on six dogs using alignment and cutting jigs to prepare the bony surfaces. The dogs were killed 6 months following surgery. Extensive bone ingrowth was present in all pegs of every tibial component. Bone ingrowth was present in 12% of the pad area of one component, 22.7 to 41.6% in four components, and 81.1% in another. The void spaces in other areas were filled with fibrous tissue or in the periphery of the device with fibrocartilage. Bone ingrowth in the pad was consistent in the vicinity of the pegs and was variable in regions not adjacent to the pegs, suggesting that the pegs exerted a strong influence on the pattern of bone ingrowth into the pad.

Animals↗
PubMed2004

Finding a method for optimizing risk adjustment when comparing surgical-site infection rates.

OBJECTIVE: To investigate whether stratification of the risk of developing a surgical-site infection (SSI) is improved when a logistic regression model is used to weight the risk factors for each procedure category individually instead of the modified NNIS System risk index. DESIGN AND SETTING: The German Nosocomial Infection Surveillance System, based on NNIS System methodology, has 273 acute care surgical departments participating voluntarily. Data on 9 procedure categories were included (214,271 operations). METHODS: For each of the procedure categories, the significant risk factors from the available data (NNIS System risk index variables of ASA score, wound class, duration of operation, and endoscope use, as well as gender and age) were identified by multiple logistic regression analyses with stepwise variable selection. The area under the receiver operating characteristic (ROC) curve resulting from these analyses was used to evaluate the predictive power of logistic regression models. RESULTS: For most procedures, at least two of the three variables contributing to the NNIS System risk index were shown to be independent risk factors (appendectomy, knee arthroscopy, cholecystectomy, colon surgery, herniorrhaphy, hip prosthesis, knee prosthesis, and vascular surgery). The predictive power of logistic regression models (including age and gender, when appropriate) was low (between 0.55 and 0.71) and for most procedures only slightly better than that of the NNIS System risk index. CONCLUSION: Without the inclusion of additional procedure-specific variables, logistic regression models do not improve the comparison of SSI rates from various hospitals.

Adult↗
PubMed1993

The effect of anterior cruciate ligament resection and immediate or delayed implantation of a meniscus prosthesis on knee joint biomechanics and cartilage. An experimental study in rabbits.

In a rabbit experiment with anterior cruciate ligament (ACL) resection, immediate substitution of the medial meniscus with a prosthesis was compared with delayed prosthetic implantation after a postmeniscectomy period of three weeks. The knees with a prosthetic implant were compared with their contralateral joints as well as to joints with an intact ACL and menisci. Anterior cruciate ligament resection alone led to disturbed biomechanics and cartilage degeneration. Anterior cruciate ligament resection in combination with meniscus resection increased cartilage degeneration and led to more inferior biomechanics. Ingrowth and stable fixation was less frequent when the prosthesis was inserted three weeks after meniscus resection than when inserted immediately. Furthermore, in knees with delayed prosthetic implantation, only minor improvement in terms of cartilage protection was shown when compared with knees with resection only. In contrast, knees with immediate meniscus replacement demonstrated similar joint stiffness and stress relaxation characteristics and similar cartilage protection effects as knees with a nonresected medial meniscus.

Animals↗
PubMed2001

Model-based Roentgen stereophotogrammetry of orthopaedic implants.

Attaching tantalum markers to prostheses for Roentgen stereophotogrammetry (RSA) may be difficult and is sometimes even impossible. In this study, a model-based RSA method that avoids the attachment of markers to prostheses is presented and validated. This model-based RSA method uses a triangulated surface model of the implant. A projected contour of this model is calculated and this calculated model contour is matched onto the detected contour of the actual implant in the RSA radiograph. The difference between the two contours is minimized by variation of the position and orientation of the model. When a minimal difference between the contours is found, an optimal position and orientation of the model has been obtained. The method was validated by means of a phantom experiment. Three prosthesis components were used in this experiment: the femoral and tibial component of an Interax total knee prosthesis (Stryker Howmedica Osteonics Corp., Rutherfort, USA) and the femoral component of a Profix total knee prosthesis (Smith & Nephew, Memphis, USA). For the prosthesis components used in this study, the accuracy of the model-based method is lower than the accuracy of traditional RSA. For the Interax femoral and tibial components, significant dimensional tolerances were found that were probably caused by the casting process and manual polishing of the components surfaces. The largest standard deviation for any translation was 0.19mm and for any rotation it was 0.52 degrees. For the Profix femoral component that had no large dimensional tolerances, the largest standard deviation for any translation was 0.22mm and for any rotation it was 0.22 degrees. From this study we may conclude that the accuracy of the current model-based RSA method is sensitive to dimensional tolerances of the implant. Research is now being conducted to make model-based RSA less sensitive to dimensional tolerances and thereby improving its accuracy.

Biomechanical Phenomena↗
PubMed2002

[In vitro analysis of the continuous active patellofemoral kinematics of the normal and prosthetic knee].

PURPOSE OF THE STUDY: In vitro experiments are particularly useful for studying kinematic changes from the normal knee to experimental conditions simulating different disease states. We developed an experimental protocol allowing a kinematic analysis of the femorotibial and femoropatellar joints in the healthy knee and after implantation of a knee prosthesis, according to the central pivot during simulated active loaded movement from the standing to sitting position. EXPERIMENTAL SETUP: An experimental device was designed to apply force to the femur of a cadaveric specimen including the femur, the patella and the tibia. The tibia was angled in the sagittal plane and the femur was free to move in space in response to the geometric movement of the knee joint, the capsuloligamentary structures, the quadriceps tendon and gravity. Variation in the length of the quadriceps tendon controlled the flexion-extension movement. The experimental setup included computer-controlled activation allowing continuous coordinated movement of the femur relative to the tibia and of the tibia relative to the ground. Standard activations simulated movement from the standing to the sitting position. STUDY PROTOCOL: Five pairs of fresh-frozen cadaver specimens including the entire femur, patella, tibia and fibula, the capsuloligamentary and intra-articular structures of the knee, the superior and inferior tibiofibular ligaments and the quadriceps tendon were studied. The quadriceps tendon was connected to the computer-guided activation device. Reflectors were fixed onto the anterior aspect of the femur, the superior tibial epiphysis and the center of the patella. Anatomic landmarks on the femur, the tibia, and the patella were identified to determine the plane of movement of each bone in the three rotation axes and the three translation directions. Three infrared cameras recorded movements of the reflectors fixed on the bony segments and, by mathematical transformation, the movement of the corresponding bony segment, displayed in time-course curves. RESULTS: The patella moved in continuous fashion over the femur, directly following the angle of knee flexion with a ratio of about 60%, which was constant for all knees studied and for all configurations. The patella of healthy knees and knees implanted with a unicompartmental prosthesis exhibited medial rotation during the first 30 degrees of flexion, with a movement of about of 10 degrees, then a lateral rotation of about 10 degrees to 20 degrees when the flexion reached 90 degrees; implantation of a total knee prosthesis led to a medial rotation which was continuous from 5 degrees to 15 degrees. There was a trend towards continuous abduction of about 10 degrees. The patella exhibited a continuous anterior translation of 10 to 20 mm from the tibia with increasing knee flexion, in both normal and prosthetic knees (unicompartmental prosthesis); knees implanted with a total knee prosthesis exhibited 5 to 10 mm anterior translation from 0 degrees to 50 degrees flexion, then an equivalent posterior translation for 50 degrees to 90 degrees flexion. The patella made a continuous 5 to 10 mm medial translation movement over the tibia in both normal and prosthetic (unicompartmental) knees; knees implanted with a total knee prosthesis exhibited 0 to 5 mm lateral translation starting after 50 degrees flexion. The patella also exhibited a continuous distal translation over the tibia of about 20 to 30 mm, for all configurations. DISCUSSION: The experimental set up enables a comparison of the kinetics of a normal knee with the kinetics observed after implantation of a prosthesis on the same knee. Implantation of a unicompartmental medial prosthesis, leaving the posterior cruciate ligament intact and irrespective of the status of the anterior cruciate ligament, did not, in these experimental conditions, exhibit any significant difference in the femorotibial or femoropatellar kinetics compared with the same normal knee. Implantation of a total knee prosthesis had a significant effect on the femoropatellar kinematics, compared with the same knee before implantation. The main anomalies were related to the medial-lateral rotation of the patella which exhibited an abnormal lateral rotation, possibly favorable for subluxation; these changes were directly related to femorotibial rotation after implantation of the total prosthesis and appeared to be related to the symmetry of the femoral condyles of the prosthesis model studied, perturbing the normal automatic rotation of the knee. There is thus a strong relationship between femorotibial and femoropatellar kinetics in the total knee prosthesis.

Arthroplasty, Replacement, Knee↗
PubMed1977

Current status of total knee replacement.

Correction of deformity and relief of pain in advanced arthritis of the knee joint can be obtained by implantation of a total knee prosthesis. For the painful, mildly damaged knee, the Charnley prosthesis may be used, while in the more moderately damaged knee, the geometric prosthesis may be indicated. For the unstable, severely damaged knee, a constrained prosthesis may be implanted. These knee prostheses can be used to treat knees which previously were not amenable to surgical correction, except by arthrodesis.

Humans↗