The authors review current knowledge regarding the use of ceramic materials in prosthetic hip surgery, both as constituents of prosthetic components, and as materials used to coat metallic surfaces. A review of the literature defines the advantages and disadvantages to using ceramic-polyethylene or ceramic-ceramic combinations, based on the possibility that alumina coating may favor localized bone demineralization, and on the first promising clinical results of the use of hydroxyapatite coating.

Aluminum↗

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Computerized morphometric analysis of the femoral diaphyseal canal.

The constant increase in the use of hip arthroplasty and the continuous search for the best possible adaptation of the implant to femoral anatomy have led to the development of methods of radiographic analysis that are increasingly precise and reliable. Among these the methods that include the use of traditional radiograms-despite their limits-deserve a place of importance. In fact, these methods offer the advantage of being easy to apply and of allowing for a comparison to be made with pre-existing files. Computer science is useful in this field, in particular, computerized analysis, both morphometric and statistical, of the data acquired by digitizer. The protocol of acquisition and analysis that we applied to x-rays in anteroposterior view allowed for an evaluation to be made of some of the morphologic parameters of 354 femurs (corresponding to 264 patients), relating them with the pathologies that led to hip arthroplasty. The duration of a cementless hip prosthesis strongly depends on primary stability. For this reason, an ever-increasing number of studies tends to make a precise evaluation of the morphology of the joint, in order to obtain excellent contact between bone and prosthetic component. The methods used are essentially radiological, with the use of computerized tomography and stereophotogrammetry. Morphometric studies of the proximal femoral area have in particular considered the width of the medullary canal at various levels; the cervico-diaphyseal angle; the flare index of the femoral canal (relationship between the internal metadiaphyseal diameter and that of the isthmus) and the distance between the rotation center of the femoral head and the diaphyseal axis. The evident absence of proportion between femoral sizes and shape of the medullary canal has led to the search for parameters capable of describing in simple fashion the shape of the femoral diaphyseal canal. A good describer of femoral morphology is the flare index, that allows for classification of the various shapes of the diaphyseal canal in three families: "stove-pipe like", "normal", "champagne glass like". The distinction between these groups is not clear, as the passage from one shape to another is gradual. The idea of obtaining more knowledge on femoral morphology, also to the purpose of determining possible new criteria that may be of help in preoperative planning and in the choice of a model to be implanted, has suggested our study on modifications caused by some of the pathologies that most frequently lead to arthroplasty.

Adult↗

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Diagnostic protocol in prosthetic loosening.

The authors report the results they obtained in 35 cases studied based on a protocol to identify prosthetic loosening and to preoperatively establish its possible septic etiology. After clinical and radiographic assessment, the protocol called for a total body bone scan with Tc 99 m which, in positive cases, were associated laboratory tests and further instrumental testing (CT, bone scan and needle aspiration). Thanks above all to bone scan with labelled granulocytes the protocol provided high accuracy (91.4%) in preoperatively identifying the causes of infection.

Clinical Protocols↗

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Indications and limits of CT scan in prosthetic loosening.

The authors attempt to define the role of computed tomography (CT) in the study of loosened hip prosthesis. To this purpose they have studied 30 patients with clinical and/or radiographic findings of loosening, carrying out a conventional radiographic assessment and a CT scan of the hip in question, and then comparing them. They conclude that CT scan when carried out according to the correct procedures described is very useful. Despite the presence of technical artefacts due to the presence of the metal prosthesis, the test makes a considerable contribution, not so much to the diagnosis of loosening in itself, which continues to be a clinical-radiologic diagnosis, rather to the evaluation of the morphostructural states of the acetabular bone for correct planning of surgery.

Hip Prosthesis↗

PubMedDate not supplied

Indications for prosthetic reimplantation.

It is difficult to establish on the basis of rigorous criteria when a prosthetic implant must be considered loosened, but it is even more difficult to define with certainty whether a loosened prosthesis must be reimplanted, and particularly when it is necessary to act. The authors emphasize the need to act quickly every time there is loss of periprosthetic bone substance that progresses in time, and that may make anatomical reconstruction difficult.

Hip Prosthesis↗

PubMedDate not supplied

Which length for the revision stem?

The results of 79 stem implantations performed between 1981 and 1992 are presented. Mean clinical and radiographic follow-up was obtained 36 months after surgery. All of the prostheses were substituted due to aseptic loosening: of these 68% were cemented. Femoral osteolytic lesions secondary to loosening was classified based on the Paprosky protocol. A severe femoral osteolytic defect (type 2b, 2c or 3 according to Paprosky) was associated with 4% of the cases of loosened cementless prostheses, and with 37% of the cemented ones. Homoplastic bone grafts were used in 40% of the patients. The length of the stems used for reimplantation was short (12-13 cm) in 43%, standard (17-18 cm) in 49%, and long (> or = 22 cm) in 7% of the cases. These stems were cemented in 32% of the cases. The incidence of cementation was different in relation to length, as 62.5% of the short stems were cemented, as compared to 5.3% of the stems of standard length. Clinical results were excellent in 90% of the cases submitted to surgery with short stems, in 80% of those treated with standard stems, and in 50% of the cases of revision surgery where long stems were used. Radiographically, 97% of the short stems were osteointegrated, as compared to 94% of the standard stems and to 25% of the long ones, which were only used in a very few cases to be considered quite complex ones.

Bone Cements↗

PubMedDate not supplied

Indications and limits of acetabular reimplantations using screwed prostheses.

The clinical and radiographic results of 95 acetabular reimplantations performed between 1984 and 1992 are presented. A screwed acetabular prosthesis was used in 56 patients, the acetabulum was cemented in 15, and a press-fit acetabulum stabilized by screws (1 case without screws) was used in 24. Mean clinical follow-up was 35.6 +/- 24 months, ranging from 7 to 94 months. Clinical results were good and excellent (> or = 5 points according to Merle D'Aubigné) in 77% of the cases for pain, in 70% for walking, and in 71% for joint movement. Forty months after surgery 48% of the screwed acetabula and 44% of the cemented ones were osteointegrated. The incidence of loosening for the screwed acetabula was 24%. The preliminary results 24 months after the press-fit acetabula with screws had been inserted showed 100% osteointegration. Radiographic results of the screwed acetabula were satisfactory (92% osteointegration) only in reimplantations performed in patients with minimum acetabular osteolytic injury (Paprosky types I and IIA). The use of homoplastic bone grafts did not improve the radiographic results of the screwed acetabula in the cases with severe osteolysis: 57% of the acetabula screwed on grafts distributed throughout the acetabulum were, in fact, loosened.

Acetabulum↗

PubMedDate not supplied

Techniques for removal of the stem: transfemoral or intramedullary?

Since 1981 a total of 76 reimplantations of the prosthetic stem have been performed, substituting 52 cemented stems and 24 cementless ones. Only 7 patients (9%) required transcortical access, 3 of these stems (43%) were not osteointegrated, while of the 69 reimplantations performed by intramedullary approach, only 4% of the stems did not achieve skeletal stabilization. A total of 43% of the stems reimplanted using an intramedullary approach were short (12-13 cm). The advantages of intramedullary access may be summarized by saying that diaphyseal cortical bone is saved; in the use of short prosthetic models. The transcortical technique is limited to a minority of patients, particularly to cases where stems that show osteointegration and are cementless are removed.

Bone Marrow↗