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At least 631 records · Page 35Linked to original sources
PubMed1997

A second-generation cementless hip prosthesis: improved results over the first-generation prosthesis.

Forty-two patients who had a Porous Coated Anatomic (PCA) "E" series, second-generation, cementless hip arthroplasty (Howmedica, Rutherford, NJ) were compared with 42 patients who had a first-generation PCA prosthesis. Patients were directly matched for age, sex, diagnosis, weight, Charnley functional status, and duration of follow-up. All of the operations were done by the same two surgeons, who used the same operative approach and the same postoperative rehabilitation plan. All of the patients were followed up for at least 5 years (range, 60 to 76 months). In the "E" series group, there were 41 of 42 (98%) good and excellent clinical results with a mean Harris hip score of 94 points (range, 46 to 100 points); the first-generation group had 34 of 42 (81%) good and excellent clinical results and a mean Harris score of 81 points (range, 42 to 100 points) (P = 0.001). There was one acetabular component revision in the "E" series group (2%), which can be compared with eight revisions (19%) in the first-generation group (P = 0.012). The incidence of femoral radiolucencies was 19% (eight hips) for the "E" series group compared with 50% (21 hips) in the first-generation group (P = 0.009). The radiolucencies in the "E" series group were small, nonprogressive, and confined typically to zone I. We believe that the improvements in design of the "E" series component may account for these differences.

Adult↗
PubMed1982

The results of early clinical trials with a microporus coated metal hip prosthesis.

In an attempt to find a better method of attaching a prosthesis to bone, a microporous coating system, with a pore width of approximately 50 microns was chosen for evaluation. A microporous coated Austin-Moore type prosthesis was inserted into 34 patients, and the results were studied for a three-year period. Four cases required reoperations, and ten cases demonstrated radiolucent lines around the prosthesis suggesting that bone ingrowth had not occurred. This article analyzes the reasons for failure of ingrowth and suggests modifications in the prosthesis design and postoperative management that hopefully will be effective.

Adult↗
PubMed1997

[Pseudotumor manifestation of metallosis in a hip prosthesis].

A pseudo-tumour due to metallosis is described in association with an iso-elastic hip replacement. This is a relatively rare lesion which may be difficult to diagnose. Scintigraphy and radiography may be helpful in distinguishing the lesion from a primary or secondary neoplasm, but the presence of osteolysis adjacent to the prosthesis will suggest the true nature of the lesion.

Aged↗
PubMed1989

A five year follow-up of 605 cases of the MCCL (metal-cancellous cementless Lübeck) total hip prosthesis.

The porous surface of the MCCL prosthesis macroscopically resembles spongy bone, with a porous depth of up to 10 mm, the width of the pores measuring 1-2 mm, with reticular spaces forming an intercommunicating system. The superficial porous surface and the implant stem are combined in a single structure. The standard prosthesis is made up of four components; an acetabulum in cobalt-chrome-molybdenum alloy, an interposed layer of polyethylene, a ceramic head and a stem in cobalt-chrome-molybdenum alloy, the shape of which is anatomically matched to the proximal femur. What emerges from the present study is the possibility of using right and left stems, each available in six sizes. The ceramic head may be attached to the neck of the femoral stem, which may be long, average, or short. An "extra-long" metal head is also available.

Activities of Daily Living↗
PubMed1989

Plain radiographs inadequate for evaluation of the cement-bone interface in the hip prosthesis. A cadaver study of femoral stems.

To determine whether plain radiographs accurately represent the true cement-bone interlock, a comparison was made between radiographs and macroscopic morphology on cross sections of 11 human femora into which a cemented endoprosthesis had been inserted. Four femora had been retrieved postmortem from patients with a hip arthroplasty, and seven cadaver femora were cemented under varying conditions. All the femora were radiographed and then cut for macroscopic inspection of the cement-bone interface with respect to gross interposition, depth of cement penetration, integrity of the bone bed, and lamellation of the cement.

Bone Cements↗
PubMed1998

Salvage of a recurrently dislocating total hip prosthesis with use of a constrained acetabular component. A retrospective analysis of fifty-six cases.

Fifty-six constrained acetabular components were placed, between April 1988 and February 1993, in fifty-five patients who had had recurrent dislocations (average, six dislocations; range, two to twenty dislocations) of the femoral component after a previous total hip arthroplasty. All patients had additional factors contributing to the instability of the implant, including absence or disruption of the abductor mechanism, poor health, mental retardation, confusion, and Alzheimer disease. One patient was lost to follow-up. The remaining patients were followed clinically for a minimum of three years (average, sixty-four months; range, thirty-seven to ninety-seven months) or until the time of death. During the follow-up interval, only two (4 per cent) of the fifty-five patients had a subsequent dislocation. The use of this type of component should be considered for patients who have recurrent dislocation if other treatment modalities are unlikely to be effective.

Acetabulum↗
PubMed1998

Composite hip prosthesis design. I. Analysis.

An investigation was performed to study the mechanical performance of fiber-reinforced composite hip prostheses in a femur. The main objective of the study was to evaluate the effect of fiber orientation of a composite femoral implant on the response of the surrounding femoral bone. A three-dimensional finite element analysis was developed for analyzing a composite implant in the femur. A three-dimensional composite element was proposed to take into account ply drop-off due to a change of cross-section of the composite implant. The element could accommodate multidirectional layers and tapered composites. The material properties of the composite were treated as anisotropic and inhomogeneous while the properties of femoral bone were treated as anisotropic and homogenous. All the materials were assumed to behave linear-elastically. The thermoplastic graphite/PEEK material system was selected for the study. In this presentation, as the first part of the study, the development of the finite element analysis will be described. Numerical calculations were generated and compared with existing data and numerical results available from studies related to metal hip prostheses in the literature. Experiments on the composite hip implants were also conducted for further verification of the analysis and the computer simulations. In Part II, using the finite element code, an extensive study was performed to evaluate the stress/strain distributions, micromotions, and strain-energy density of the surrounding femoral bone, which have been related to initial fixation and long-term stability of the prosthesis in a femoral bone. Numerous fiber orientations were studied, and results of the calculations were compared with those generated by the prosthesis made of cobalt alloy and titanium alloy.

Hip Prosthesis↗
PubMed1993

Load transfer with the Austin Moore cementless hip prosthesis.

More than 1,300 Austin Moore hemiarthroplasties have been reviewed in the literature, with no reports of fracture of the stem. Many patients with these hip implants had good function. The lack of stem fractures in patients with good functions has not been explained and contrasts with stem fractures that have occurred in patients with cemented prostheses of other designs during the same time. We used three-dimensional finite-element analysis and free-body diagrams to explain the lack of fractures for this device by a description of the probable load-transfer mechanisms between the prosthesis and the bone. Results from our finite-element analysis indicate that, with good calcar-collar support, the stresses in the stem are small because the stem portion of the prosthesis and the bone are uncoupled and, consequently, do not share the resultant bending moment of the head and abductor forces. If the stem is coupled to the bone so that the resultant bending moment is shared, high stresses in the stem are predicted; such stresses are inconsistent with the complete absence of fractures of these prostheses. The results of the finite-element analysis further showed that loss of calcar-collar support with proximal fixation through the fenestrations resulted in high stresses in the stem and stress shielding of the proximal medial cortex. The uncoupled prosthesis also may be modeled with a free-body diagram as a three-force member loaded at the head, stem tip, and in the proximal region. With this model, it can be shown that the reaction force of the stem tip, and thus the peak bending stress in the stem, increases as calcar-collar support is decreased. If there is no calcar-collar support, proximal support must be provided by some combination of integration of bone in the fenestrations and wedging due to the lateral-medial taper of the device. Stresses in the stem are largest when there is no wedging, but high stresses develop in the cancellous bone in the fenestrations. When there is wedging, stresses in the stem can be low, but stresses in the supporting cancellous bone can be high; additional proximal support through the fenestrations substantially reduces these bone stresses. If reduced stresses in the cancellous bone are indicative of a stable device, these mechanisms indicate that fractures of the Austin Moore prosthesis have not occurred in normally loaded hips because load was transferred primarily either through the collar or by wedging, with additional support at the fenestrations.

Aged↗
PubMedDate not supplied

[Clinical course of a late aseptically loosened PCA hip prosthesis shaft].

The surface of the proximal part of a PCA endoprosthesis stem in total hip replacement is structured with small beads to provide good conditions for bone ingrowth. The distal part of the stem has a smooth surface. For the mechanical fixation concept, this means anchorage of the proximal part and free axial mobility of the distal part of the prosthesis. We present a clinical case in which bone remodeling processes finally led to complete loosening of the prosthesis. The described mechanism of loosening could be reconstructed by radiological findings, bone scan, two digital subtraction arthrographies of the hip and by evaluation of the fibrous tissue formation around the stem after explanation. In this case, after an initial period of no measureable bone reactions, distal endosteal bone and proximal radiolucent space developed without loss of contact with the prosthesis. Later, a mechanical interruption between the proximal part of the prosthesis and bone occurred. There was no loosening of the distal part of the prosthesis at this time. Despite remarkable hypertrophy of the distal femoral bone, eventually the distal part of the prosthesis loosened so that a revision arthroplasty had to be performed. The described mechanism of loosening has not be proven to pertain to all such prostheses.

Bone Remodeling↗