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PubMed1999

[Cadaver study of acetabular cup mobility in the healthy hip and prosthesis by monopodal pressure simulation ].

PURPOSE OF THIS STUDY: The purpose of this study was to quantify relative displacement of anterior and posterior horn of the acetabulum lunate surface using Omega strain gauges while increasing loads were applied to the hip joint. Measurement were performed on fresh cadaver bones in unipodal stance using experimental method before and after socket's implantation. MATERIAL AND METHODS: [corrected] Nine skeletons, from fresh non-embalmed cadavers, including pelvis, the three last lumbar vertebrae and both femurs were maintained in unipodal equilibrium using metallic cables for muscle passive simulation. Loads were applied up to 700 N. Specific extensometric Omega strain gauges were created and tested, with 5 mu of sensibility. Measurement of displacement between horns were studied on two sides of each pelvic before and after implantation of conventional and prototype cemented or press fit implants. RESULTS: Among 81 loads on 18 acetabulum healthy and implanted, displacement was significant in 58 cases with a spacing of horn of 7 to 140 mu with average 31.1 mu and non significant in 25 cases. On healthy acetabulum, spacing was variable from 12 to 140 mu (average 43.2 mu) in 18 of 26 loads. On implanted acetabulum by different sockets, spacing was variable from 7 to 100 mu (average 27.4 mu) in 40 of 55 loads. Displacement was function of rotation hip, smaller in internal rotation and larger in external rotation. Spacing of horns was reduced in oversize sockets. DISCUSSION: The data obtains by omega strain gauge suggest acetabular displacement is not univocal under load. There were a widening of the acetabular notch on load. This can be explained by the modification of primary incongruity of the two components of the hip joint because of acetabular deformation. Such results are in agreement with recently published data obtained about length of the transverse acetabular ligament.

Acetabulum↗
PubMed1992

[Registration under the diagnosis of traumatic hip luxation in the national registry].

A national study of patients treated on account of traumatic dislocation of the hip in Denmark in 1989 and 1990 revealed that 755 cases had been registered under this diagnosis in the National Patient Register. A review of case reports from 71 departments with 755 registered identity numbers in the National Patient Register demonstrated that 121 patients had been treated for traumatic dislocation of the hip during the same period, and that seven of these had not been registered via the National Patient Register. The remaining 605 patients (80%) had either sustained dislocation of a hip prosthesis or had congenital dislocation of the hip. It is concluded that the Danish National Register, in its present form is of no value whatsoever in registration of traumatic dislocation of the hip nor congenital dislocation of the hip or dislocation of a total hip prosthesis.

Denmark↗
PubMed2004

An experimental animal model of aseptic loosening of hip prostheses in sheep to study early biochemical changes at the interface membrane.

BACKGROUND: Aseptic loosening of hip prosthesis as it occurs in clinical cases in human patients was attributed to wear particles of the implants, the response of the tissue dominated by macrophages and the production of inflammatory mediators and matrix degrading enzymes; however, the cascade of events initiating the process and their interaction regarding the time course is still open and discussed controversially. Therefore, the goal of this study was to establish an experimental animal model in sheep allowing to follow the cascade of early mechanical and biochemical events within the interface membrane and study the sequence of how they contribute to the pathological bone resorption necessary for aseptic loosening of the implant. METHODS: A cemented modular system (Biomedtrix) was used as a hip replacement in 24 adult Swiss Alpine sheep, with one group receiving a complete cement mantle as controls (n = 12), and the other group a cement mantle with a standardized, lateral, primary defect in the cement mantle (n = 12). Animals were followed over time for 2 and 8.5 months (n = 6 each). After sacrifice, samples from the interface membranes were harvested from five different regions of the femur and joint capsule. Explant cell cultures were performed and supernatant of cultures were tested and assayed for nitric oxide, prostaglandin E2, caseinolytic and collagenolytic activity. RNA extraction and quantification were performed for inducible nitric oxide synthase, cyclooxygenase-2, interleukin 1, and interleukin 6. Overall differences between groups and time periods and interactions thereof were calculated using a factorial analysis of variance (ANOVA). RESULTS: The development of an interface membrane was noticed in both groups at both time points. However, in the controls the interface membrane regressed in thickness and biological activity, while both variables increased in the experimental group with the primary cement mantle defect over time. Nitric oxide (NO) and PGE2 concentrations were higher in the 8.5 months group (P < 0.0001) compared to the 2 months group with a tendency for the unstable group to have higher concentrations. The same was true for collagenolytic activity (P = 0.05), but not for caseinolytic activity that decreased over time (P < 0.0001). CONCLUSION: In this study, a primary cement mantle defect of the femoral shaft elicited biomechanical instability and biochemical changes over time in an experimental animal study in sheep, that resembled the changes described at the bone cement-interface in aseptic loosening of total hip prosthesis in humans. The early biochemical changes may well explain the pathologic bone resorption and formation of an interface membrane as is observed in clinical cases. This animal model may aid in future studies aiming at prevention of aseptic loosening of hip prosthesis and reflect some aspects of the pathogenesis involved.

Analysis of Variance↗
PubMed1998

Application of synchrotron radiation in investigation of metal-ion release from a hip replacement prosthesis.

The aim of the present study was to measure very low concentrations of Al, V, Fe, Cr and other metal elements in a matrix of P, S, Cl, Ca and other constituent elements of the human body. These metal elements were released from a failed total hip replacement prosthesis into the surrounding tissues. The experimental results have been compared with those from proton-induced X-ray emission spectroscopy of the same specimen.

Journal Article↗
PubMed2001

Acid attack and cathepsin K in bone resorption around total hip replacement prosthesis.

Normal bone remodeling and pathological bone destruction have been considered to be osteoclast-driven. Osteoclasts are able to attach to bare bone surface and produce an acidic subcellular space. This leads to acid dissolution of hydroxyapatite, allowing cathepsin K to degrade the organic type I collagen-rich osteoid matrix under the acidic condition prevailing in Howship lacunae. Using a sting pH electrode, the interface membrane around a loosened total hip replacement prosthesis was found to be acidic. Confocal laser scanning disclosed irregular demineralization of the bone surface in contact with the acidic interface. Cathepsin K, an acidic collagenolytic enzyme, was found in interface tissue macrophages/giant cells and pseudosynovial fluid. Tissue extracts contained high levels of cathepsin K messenger RNA (mRNA) and protein. These observations suggest the presence of an acid- and cathepsin K-driven pathological mechanism of bone resorption, mediated not by osteoclasts in subosteoclastic space, but rather by the uncontrolled activity of macrophages in extracellular space.

Acids↗
PubMed1995

Implant standardization for total hip arthroplasty. An implant selection and a cost reduction program.

Total hip arthroplasty (THA) has been targeted by the United States federal government for cost control because of its high cost and rising incidence in the aging population. The hospital cost for THA during the 1980s was controlled by utilization review and a reduction in the volume of services delivered for each THA. The single largest increase in the cost of THA during the 1980s was the cost of hip implants. The Lahey Clinic Hip Implant Standardization Program was developed to provide objective guidelines for hip implant selection. These guidelines are based on the demands a patients is expected to place on his or her hip prosthesis. Because not every patient requires an expensive high-demand hip prosthesis, the standardization program also has the potential to reduce the hospital cost for hip implants without compromising patient care. Patients are assigned to four demand categories based on five objective criteria: age, weight, expected activity, general health, and bone stock. Selection of the prosthesis in each of the four demand categories is intended to match the implant's capacity with expected patient demand. The standardization program was retrospectively applied to 103 THAs performed during 1991. Analysis of variance demonstrated that patient variables and demand categories were statistically significant groupings. The cost of hip implants would have been reduced by 25.7% with the Lahey Clinic Hip Implant Standardization Program. A prospective outcome study is required to determine the long-term validity of this standardization program.

Activities of Daily Living↗
PubMed2006

[Total hip arthroplasty after failure of per- and subtrochanteric fracture fixation in elderly subjects].

PURPOSE OF THE STUDY: Most pertrochanteric fractures can be successfully fixed with osteosynthesis. Osteosynthesis fails however is a small number of patients who require re-operation for implantation of a total hip prosthesis. This situation occurs in particular when the material has penetrated the acetabulum and in elderly subjects. Although this type of arthroplasty is routine practice, few series have been reported. We present here outcome and complications of total hip arthroplasty after failure of per- and sub-trochanteric fracture fixation. MATERIAL AND METHODS: Between 1990 and 2000, twenty patients aged 79 years on average (range 62-78 years) underwent revision for total hip arthroplasty after failure of osteosynthesis for fracture of the upper femur. A gliding THS had been used for fixation in 18 patients, a plate in one and a Gamma nail in one. Osteosynthesis failure was related to early disassembly in ten patients, pseudarthrosis in eight and malunion in two. Revision was performed via a posterolateral approach in all cases. A standard total hip prosthesis was used in 16 patients, a longer femoral stem was required in four. Femoral components were cemented in 18 patients and non-cemented in two. The cup was a standard cemented cup in 12, retaining and cemented in eight. RESULTS: Mean operative time and blood loss were greater than in first-intention arthroplasties. All patients had lost their independence prior to the revision procedure. Despite their age, all recovered independence after a stay in rehabilitation. Most still required crutches. Use of a retaining cup enabled avoiding dislocation in all cases. For those who did not have a retaining cup, dislocation was the most frequent complication (3/12). The difficulties observed were: 1) elimination of associated infection before surgery; many of these elderly subjects had altered ESR and CRP values for various reasons; 2) abnormal position of the trochanteric mass because of a rotation defect; 3) malunion of the upper femur in the frontal or sagittal planes; 4) more or less easily achieved positioning of the femoral piece on the calcar; 5) difficult intraoperative identification of limb length due to loss of usual landmarks on the lesser and greater trochanter; 6) removal of fracture screws which sometimes required use of a trephine and bridging the last screw hole with a longer centromedullary stem. The most frequent postoperative orthopedic problems were leg length discrepancy (1-2 cm for eight patients), gluteus medius insufficiency, limping and pain at palpation of the trochanteric area. DISCUSSION: Despite the difficult technique and the potential complications which are more important than for first-intention arthroplasties, this series demonstrates that total hip prosthesis is a reliable solution for treating fixation failures of the upper femur.

Age Factors↗
PubMedDate not supplied

[A concept of need and construction of a hip joint prosthesis with isolation of the friction point from the tissue].

The paper presents data available in the literature and the author's own data on the causes of bone tissue resolution around endoprostheses and on the occurrence of their aseptic instability. The author's own clinical data on 546 operations and follow-ups up to 16 years are strong evidence and his experimental findings are unique in the number of animals operated on and follow-up periods. The material was examined roentgenologically, morphologically, spectroscopically and the mineral content of bone tissue microstructures were determined. With the methods applied, the author clearly shows the role of tissue metallosis in the occurrence of aseptic instability of prosthesis. The author presents two up-to-day constructions of the total-type endoprostheses with the friction point isolated from tissue. The prostheses are accessible for manufacture at the modern enterprises and require no materials in short supply.

Animals↗
PubMed1999

Traditional and MLC based dose compensator design for patients with hip prostheses undergoing pelvic radiation therapy.

Perturbations in the dose distribution caused by a hip prosthesis when treating pelvic malignancies can result in unacceptable dose inhomogeneities within the target volume. Our results, obtained by in vivo exit dose measurements with diodes, showed a 55% reduction in the dose at the exit dmax of a lateral 15 MV photon beam after passing through a bilateral cobalt-chrome alloy hip prosthesis. Such an inhomogeneous dose distribution may decrease the curability. Solutions such as treatment techniques to avoid the prosthesis are often not the best choice as the dose to the rectum may be unacceptably high. In this work an alternative method of dose compensator is presented. Two types of dose compensators were designed based on a 3-D treatment planning system and CT images of a pelvic phantom containing a hip prosthesis: one was fabricated from a polyethylene-lead slab in the representation of step fringes and placed on a tray in the path of the beam while the other was produced by the use of several fields shaped with a multileaf collimator. The calculation procedures developed by the authors for generating the compensators are described. Results of film measurements performed in a phantom with and without the compensators in place are discussed.

Alloys↗
PubMedDate not supplied

[Results of testing a non-protrusion hip joint prosthesis].

To prevent protrusion of the socket of an endoprosthesis into the pelvis, an experimental nonprotrusion endoprosthesis has been designed and tested. The endoprosthesis is of novel design; however, its production is rather simple. The efficiency of its use is strongly evidenced by reasonably long-term experiments. Comparing the results of use of a routine design endoprosthesis versus the nonprotrusion one under the same loading conditions has shown that the novel endoprosthesis is better.

Animals↗
PubMed1988

[Experiences with the self-supporting type SCL hip screw prosthesis].

After having experienced different systems of cementless bonding for 12 years the method of screwing--in prostheses has been applied for several years now. In doing so a cementless fixing-system has been created while the implants--acetabulum cup and femoral infibulum--contact the bone with the whole surface and they are primarily fixbonded to the bone. The result of the fellow-up examinations are very satisfactory and positive results are expected as well for future fellow up examinations.

Follow-Up Studies↗
PubMed2006

Improved risk adjustment for comparison of surgical site infection rates.

OBJECTIVE: To develop prognostic models for improved risk adjustment in surgical site infection surveillance for 5 surgical procedures and to compare these models with the National Nosocomial Infection Surveillance system (NNIS) risk index. DESIGN: In a multicenter cohort study, prospective assessment of surgical site infection and risk factors was performed from 1996 to 2000. In addition, risk factors abstracted from patient files, available in a national medical register, were used. The c-index was used to measure the ability of procedure-specific logistic regression models to predict surgical site infection and to compare these models with models based on the NNIS risk index. A c-index of 0.5 indicates no predictive power, and 1.0 indicates perfect predictive power. SETTING: Sixty-two acute care hospitals in the Dutch national surveillance network for nosocomial infections. PARTICIPANTS: Patients who underwent 1 of 5 procedures for which the predictive ability of the NNIS risk index was moderate: reconstruction of the aorta (n=875), femoropopliteal or femorotibial bypass (n=641), colectomy (n=1,142), primary total hip prosthesis (n=13,770), and cesarean section (n=2,962). RESULTS: The predictive power of the new model versus the NNIS index was 0.75 versus 0.62 for reconstruction of the aorta (P<.01), 0.78 versus 0.58 for femoropopliteal or femorotibial bypass (P<.001), 0.69 versus 0.62 for colectomy (P<.001), 0.64 versus 0.56 for primary total hip prosthesis arthroplasty (P<.001), and 0.70 versus 0.54 for cesarean section (P<.001). CONCLUSION: Data available from hospital information systems can be used to develop models that are better at predicting the risk of surgical site infection than the NNIS risk index. Additional data collection may be indicated for certain procedures--for example, total hip prosthesis arthroplasty.

Aged↗
PubMed2004

Critical effect of cubic phase on aging in 3mol% yttria-stabilized zirconia ceramics for hip replacement prosthesis.

The isothermal tetragonal-to-monoclinic transformation of 3Y-TZP ceramics sintered at two different temperatures (1450 degrees C and 1550 degrees C) and duration (2 and 5h) is investigated at 134 degrees C in steam. Particular attention is paid to the presence of a cubic phase and its effect on isothermal aging. Sintering at 1550 degrees C can result in a significant amount of large cubic grains in the specimens, that have a detrimental impact on aging resistance, especially for the first stage of the aging process. Cubic grains appear to be enriched in yttrium, which in turn leads to a depletion of yttrium in the neighboring tetragonal grains. These grains will act as nucleation sites for tetragonal-to-monoclinic transformation. Even for specimens sintered at lower temperature, i.e. 1450 degrees C, the presence of a cubic phase is expected from the phase diagram, leading to a significant effect on aging sensitivity.

Ceramics↗