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PubMedDate not supplied

[Differences in polyethylene wear in hip joint prostheses with ceramic- and with metal-polyethylene combination of the articulation surfaces--a study of surgical and of autopsy materials].

Pseudocapsules of artificial hip joints with ceramic- and metal on polyethylene combination of the articulating surfaces from 126 revision arthroplasties and 41 autopsies were studied histologically with semiquantitative evaluation of the polyethylene wear. The results were compared with reports of laboratory tests in the literature. We found in the autopsy specimens as well as in the biopsies from revision arthroplasties of prostheses implanted for 4 to 8 years three times less polyethylene wear particles released from the ceramic on polyethylene prostheses. The newly established synovium surrounding prostheses with ceramic heads appeared 20% reduced in thickness with minor villous transformation. Different types of metal on polyethylene prostheses revealed no differences in wear behaviour with the exception of the bipolar prostheses which showed a markedly increased polyethylene wear.

Adult↗
PubMed1996

Determination of lubricating film thickness for permeable hydrogel and non-permeable polyurethane layers bonded to a rigid substrate with particular reference to cushion form hip joint replacements.

The lubricating film thickness in a model of compliant layered bearings, using both permeable hydrogels and non-permeable polyurethane elastomers for total hip joint replacements, has been measured using optical interferometry, under both entraining and squeeze-film motion. The film thickness in the lubricated contact was measured for both water and a 40 per cent glycerol solution in water as a function of entraining velocity and squeeze-film time. The measured lubricating film thickness for the permeable hydrogel was compared to that of the non-permeable polyurethane elastomer and little difference was found when the lubricating film thickness was sufficiently large (greater than 150 nm). Comparison of the experimental results and the theoretical predictions based upon elastohydrodynamic lubrication analysis showed good agreement in the entraining experiments where the film thickness was greater than 150 nm. In the squeeze-film experiments the experimental measurements were greater than the theoretical predictions for all squeeze times due to the formation of a central pocket of fluid which was not predicted by the simple theory used. This also occurred for the hydrogels for films greater than 150 nm. For longer squeeze times the film thickness for the hydrogel fell below the theoretical prediction. This was considered to be due to the permeability of the hydrogel reducing the film thickness when the film thickness was less than 150 nm. The permeability of the hydrogel was not modelled in the theoretical lubrication analysis used in this study.

Biomechanical Phenomena↗
PubMed2003

[Impact of anesthesia methods on the course of perioperative period in endoprosthesis of the hip joint].

The impact of methods of anesthesia on the course of perioperative period was studied up in 132 patients, to whom the total endoprosthetics of the hip joint was performed. The occupation in the operation room term and analysis of the postoperative pain syndrome occurrence with its cupping served as comparative categories for general and regional methods of anesthesia. Central neuronal blockade, epidural and spinal anesthesia have predominant significance for enhancing of the intraoperative and postoperative analgetic defense.

Anesthesia↗
PubMed1998

[Treatment of chronic acetabular pelvic osteomyelitis after alloprosthetic hip joint replacement with a gluteus maximus flap].

We report on a 65-year-old man who was sent to our clinic with osteomyelitis of the hip combined with a chronic external fistula after hip joint replacement followed by several further operations including amputation of the leg. After complete removal of the fistula and repeated vacuum sealing of the wound, we used a vasculated glutaeus maximus muscle flap to close the defect. The course after the operation was without any complications. The method applied led to sufficient treatment of the osteomyelitis without weakening the trunk muscles or rendering the use of crutches more difficult.

Acetabulum↗
PubMed1997

Direct comparison of contact areas, contact stress and subchondral mineralization in human hip joint specimens.

X-ray densitometric and CT osteoabsorptiometric findings suggest that in the human hip subchondral mineralization patterns change from bicentric to monocentric as a function of age. It has been hypothesized that these changes indicate an alteration in the geometric configuration of the joint from incongruous to congruous, possibly associated with the onset of osteoarthrosis. The purpose of this study was therefore to directly compare contact rates, contact stress and subchondral mineralization in the hip joint. Twelve specimens without cartilage lesions (ages 34-86 years) were investigated. Simulating the mid-stance phase, the contact areas were determined by polyether casting and the contact stress with Fuji film. The distribution of subchondral mineralization was assessed non-invasively with CT osteoabsorptiometry. At small loads the load-bearing areas were located at the periphery of the lunate surface. In some joints they were found in the acetabular roof and expanded, with higher loads, to the center of the lunate surface and the anterior and posterior horns. In other joints, the contact areas were recorded at lower loads in the anterior and posterior horns, and only at higher forces they merged in the acetabular roof. The maximal contact stress ranged from 8 t 9 MPa at 300% body weight. Maxima of subchondral mineralization were recorded in the acetabular roof, in the anterior and posterior horns, or in all three locations. There was no clear correlation between the distribution of contact and pressure, and the pattern of subchondral bone density. Incongruity is shown to strongly affect the distribution of contact and pressure in the human hip joint. However, the pattern of subchondral mineralization cannot be readily explained in terms of the contact areas and contact stress during mid-stance. Incongruity may give rise to tensile stresses in the subchondral bone, and the construction of the pelvis as a whole may play an important role in subchondral bone loss loads and adaptation.

Adult↗
PubMed1977

[Analysis of the metaplastic disturbances in dislocated hip joints in the orthopedic hospital of the Medical Academy in Magdeburg (author's transl)].

One of the most frequent and prognostically unfavorable complications occurring with therapy for dislocated hip joints is a metaplastic disturbance at the coxal end of the femur. We undertook a differentiation between metaplastic disturbances in necrosis of the center of the femur head and restorative disturbances. In the evaluated period between 1964 and 1974, 1298 children (2236 treated hips) were examined. Between 1965 and 1968 when the old, classical therapy for dislocation was employed, we established a metaplastic disturbances rate of 20%. The rate for necrosis of the femur head was 9% and the restorative disturbance rate was 11%. The metaplastic disturbance rate was lowered to 5.65% as a result of the modern, functional, early therapy instituted between 1969 to 1974. Here we established a rate of necrosis for the femur head of 0.45% and a restorative disturbance rate of 5.2%. This falls within the range established by Huber (5.5%) and Unger (6.06%). The possibility of an endochondral dysostosis must always be considered when bilateral restorative disturbances are present. We observed that restorative disturbances always occurred more frequently in connection with dysplasias. We fell that the cause is the endogenous tendency toward restorative disturbances of the center of the femur head. With early therapy, the possibility of a dislocation can, however, be avoided. In contrast to Kiltz, our later results and follow-up examinations indicate a poorer prognosis for necroses of the center of the femur head.

Age Factors↗
PubMed1989

[Incidence and treatment of congenital dysplasia of the hip joint in the Bardejov District over the 5-year-period 1984-1988].

The author deals with the incidence and treatment of inborn dysplasia of the hip joint in the region of Bardejov which has 80,000 inhabitants. He evaluates the results achieved in the period of 5 years (1984-1988) in 7208 children. 1152 children, i.e. 16 per cent, were treated for any grade of inborn dysplasia, subluxations and dislocations amounted to 323, i.e. 4.5 per cent, the boy-girl ratio was 1:3. Preventive screening of new-born children as early as in the first days of their life, a timely diagnosis and treatment are of great importance in this inborn deformity and lead to good results. The most suitable for the treatment appeared to be the Pavlik harness.

Czechoslovakia↗
PubMed2002

Analysis of mixed lubrication mechanism in metal-on-metal hip joint replacements.

A simple mixed lubrication model has been developed to predict the asperity contact and wear for the metal-on-metal bearing couple for total hip joint replacements. It has been shown that the femoral head radius has a large effect on the predicted asperity contact and wear depending on the lubrication regime. An increase in the femoral head radius can lead to an increase in wear under a predominantly boundary lubrication regime, but this trend can be reversed under a mixed lubrication regime towards fluid film lubrication. These observations are consistent with the recent experimental findings from hip simulator studies by Smith and co-workers.

Arthroplasty, Replacement, Hip↗
PubMed1980

Arthrography of the hip in children. Technique, normal anatomy and findings in unstable hip joints.

A method by which bilateral hip arthrography was performed under general anaesthesia in 130 infants and children 1 month to 7 years of age is described. Significant contractures of the adductor muscles had been corrected before the examination. Most of the children were girls with unilateral congenital idiopathic hip instability detected before the age of one year. From films exposed in standardized projections valuable information was obtained about the configuration of the joint cavity and the size and shape of the femoral head. Criteria for normal appearance in infants of ages 2 to 12 months are presented. More reliable details on the relation between the articular surfaces, the radiographic anatomy of the acetabulum and the distribution of the contrast medium were yielded by stereoradiography. Closed reduction was usually accomplished successfully during the arthrography, which made beginning of definitive treatment under the same anaesthesia possible.

Anesthesia, General↗
PubMed1985

Contact finite element stress analysis of the hip joint.

Two-dimensional finite element analyses were conducted of the normal hip using contact elements at the joint surface. The models studied were constructed for a slice through the pubis, acetabulum, and ilium. In the analyses the proximal femur was pressed into the acetabulum and intraarticular pressures and principal stresses in the joint region were determined for different load magnitudes and directions and various boundary conditions. Three sets of boundary conditions were examined: (a) deformable pubic symphysis, (b) rigid pubic symphysis, and (c) simulations of experimental studies. In the deformable model the pubic symphysis was free to displace in the sagittal plane and rotate. In the rigid model the pubic symphysis was rigidly fixed. Superoposterior loading resulted in high-contact pressures at the acetabular dome for all sets of boundary conditions. For the deformable model subject to a more medially directed load the acetabulum closed in such a manner as to squeeze the head of the femur creating high-contact pressures superiorly and inferiorly. This resulted in significant compressive stresses in the superior dome cancellous bone and inferior cancellous bone. The cumulative effect of this squeezing action with normal biological remodeling may cause elongation of the femoral head resulting in asphericity and incongruity of the unloaded hip joint articular surfaces. Rigidly fixing the pubic symphysis stiffened the model and resulted in principal stress patterns that did not reflect trabecular density or orientations as well as those of the deformable pubic symphysis model. Finite element simulations of previous experimental studies modeled the close proximity of the fixation to the excised acetabulum. These boundary conditions prevented the squeezing caused by pelvis deformations. The resulting contact areas, pressure distributions, and bone stresses were very different from those of the more anatomic, deformable pubic symphysis model. These findings demonstrate the sensitivity of hip contact pressures and stresses to imposed boundary conditions and indicate that care should be taken to simulate anatomic conditions in experimental and theoretical studies.

Acetabulum↗
PubMed1975

[The development of the dysplastic hip joint after conservative treatment (author's transl)].

The roentgenograms were evaluated of 220 patients (159 female, 61 male) with 61 luxations, 77 subluxations and 203 dysplastic hip joints which were a maximum of 2 years old during treatment and had been under observation for between 2 and 17 11/12 years. The CCD-, CE- and Ac-angles were measured. 1. The CCD-angle develops relatively independent of the therapy for the first few months. In the long term, the abduction treatment leads to a straightening up of the femoral neck. Here a physiological component apparently has an effect which reduces the straightening after several years. 2. The CE-angle rapidly becomes enlarged during the first few months, later the rate is slower. Three years after treatment began, the CE-angle was normal in 83.6% of the patients. 3. The Ac-angle decreases rapidly during the first 6 months. Three years after the beginning of treatment, 65.7% of the patients had a norm of less than 20 degrees. 4. All angles show a positive correlation of their beginning and end values i.e. light dysplasias have the best prognosis. 5. The monotherapy with a spreader pant showed a particular advantage over the combination treatment and plaster fixation. 6. The best result was achieved with treatment beginning before the age of 6 months. Boys showed a better tendency to heal. A difference in sides could not be shown.

Age Factors↗