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Background: Impaction grafting in hip revision surgery is widely used but studies with mid- and long-term follow-up are scarce., Patients, Methods and Results: A 5-year radiostereometric (RSA) follow-up of 15 hip revisions with the Exeter stem, morselized impacted allograft bone and cement revealed that 3 stems had not migrated between 2 and 5 years after revision, 11 stems had migrated to a minor degree in at least 1 direction, and 1 stem was loose according to RSA but without any radiographic signs of loosening or pain. The pain score was comparable to primary arthroplasties., Interpretation: From a 5-year perspective, first-time hip revisions for aseptic loosening with impacted morselized allograft bone and cement appear to yield good clinical results, although stem migration continues to a minor degree 2 years after revision.

A pure titanium cylinder or a piece of bone cement was implanted in each upper tibial metaphysis of 20 rabbits. After 4 months radiograms were taken and 10(4), 10(6), or 10(8) Staphylococcus aureus were injected into each leg through central holes in the implants in three groups of animals. Four weeks later new radiograms, bacteriological and histological biopsies were obtained. Three animals died before the end of the experiment. In animals which received 10(6) or 10(8) S. aureus radiographic signs of infection were found in 11/22 legs with both titanium and bone cement implants. No radiolucent zones developed around the implants. Bacteriological cultures from bone close to the implants were negative in all legs with titanium implants and positive in four legs with cement implants. Seven cultures were negative in spite of radiographic changes. It is concluded that after a proper time for wound healing the bone around unloaded implants of both titanium and bone cement is fairly resistant to infection. In some cases, healing of an infection in the surrounding bone seems possible.

The Miller-Galante I knee replacement was inserted in 25 women and three men (33 knees) with osteoarthrosis. All patients received a TiAlV femoral component with a commercially pure titanium fiber-mesh undersurface. Cemented or cementless fixation was used based on a randomization protocol. Micromotions of the femoral components were recorded with roentgen stereophotogrammetric analysis during the first 2 postoperative years. The magnitude of migration did not differ between cemented and uncemented fixation. The number of nonmigrating prostheses decreased from 21 (12 cemented and nine uncemented) at 3 months to six (three cemented and three uncemented) at 24 months. In both groups, the magnitude of prosthetic tilting about the longitudinal axis (internal-external rotation) was as large as that about the transverse axis (flexion-extension). Rotation into extension was as common as rotation into flexion. The largest translations were recorded at either of the posterior condyles. In 10 uncemented components, radiolucent lines were seen at the distal interface postoperatively. Proximal migration of the femoral component was recorded in these knees, and the width of the lines decreased or the lines disappeared totally at 24 months. After 2 years, lines were noted around four cemented and four uncemented replacements, mainly anteriorly or distally. All of these prostheses migrated. One prosthesis, revised because of malalignment, displayed pronounced migration after an initial period of stability. Bone ingrowth was observed anteriorly and anterodistally despite the presence of motions of 1 mm or more.

The current technique and instrumentation for contained morselized allograft with cement in dealing with femoral loosening associated with loss of bone stock is described. With a follow-up extending to 6 years, this method has proved effective in the management of these difficult problems.

A screw-shaped titanium chamber has been designed for serial in vivo observations of the bone-implant interface. First, the chamber is implanted; later a test substance, e.g. bone cement, is inserted in the chamber and brought in contact with the bone with minimal trauma. Both acute and long-term effects can be intravitally observed, photographed, and recorded.

The bone-cement interface from the tibial components in three clinically successful unicompartmental Marmor arthroplasties was studied histologically. The migratory behavior of the prostheses had been followed by roentgen stereophotogrammetic analysis (RSA) since their insertion 5-7 years prior to retrieval for reasons other than mechanical loosening. The prostheses migrated during the first 3 years, after which no further migration occurred. Clinical and RSA data thus suggest stable fixation. All interfaces were made up entirely of soft tissue. In the sagittal portion, between the prosthesis and the tibial eminence there was mostly fibrous tissue, while the region underneath the prostheses consisted largely of highly differentiated fibrocartilage. This histologic picture is compatible with a migratory pattern, as measured by RSA, of stable fixation after an initial remodelling period, which the authors believe has the potential of good long-term results.

The acute chemical trauma of bone cement was investigated in the rabbit tibia. With the experimental model used, the surgical trauma and the thermal effects of the cement could be minimized. Each animal received one implant of polymerized cement as a control and one implant of polymerizing dough as the test material. The animals were observed for up to seventy days and the specimens were then studied by various techniques of histology, microangiography, fluorochrome labeling, and microradiography. With this experimental method the monomer trauma did not add to the minimized surgical trauma. Moreover, no detectable influence on bone regeneration was noted. In view of this minor effect, we suggest that the surgical preparation of the implant bed and the very procedure of inserting bone cement are more important for the acute tissue trauma than is monomer leakage alone.

An extremely strong mechanical bond between cement and bone was observed in three patients with cemented hip protheses who underwent revision operations. The nature of the bone--cement attachment was studied by electron microscopy. The tissue at the interface was found to be made up of viable bone alternating with areas of soft tissue containing macrophages. The important qualitative differences between this reaction and the reaction seen around inert materials such as titanium are discussed.

Thirteen patients were reoperated on because of a nonseptic complication of their cemented hip replacement. In each patient, one of the two components was stable, and biopsies from this bone-cement interface were obtained for histologic and enzyme histochemical studies. Microscopy revealed a spectrum of tissue reactions, ranging from a seemingly direct bone-cement contact to a fibrous membrane, up to 1.5 mm thick. The bone necrosis incurred at the primary operation had been largely resorbed and replaced by viable bone.

An in vitro study was dthesigned to measure the effects of variable cement volumes and modified mixing techniques on the monomer leakage after simulated implantation. The cement volume as such was found to be an irrelevant parameter for calculations of the monomer loss from bone cement. The leakage was directly related to the surface area of the cement. Variations in the thickness of the cement mantle from 1 to 5 mm did not affect the leakage. Late cement insertion should reduce the total monomer leakage into the tissues. It is doubtful whether an increased stirring speed during mixing reduces the monomer leakage after implantation.

The tissue trauma caused by leakage of monomer from curing bone cement was studied in rabbit bone. With a chamber method it was possible to study by intravital microscopy the tissue response in the same animal from the time of cement application to as long as 350 days afterward. The immediate monomer effects were mainly vascular: blood flow disturbances, blood flow standstill, and intravascular hemolysis. The most striking finding was that the extent of vascular disturbance was related to the type of tissue afflicted: In fatty marrow the effects were widespread, and in bone or fibrous tissue they were very limited. This is interpreted to reflect the affinity of the monomer to lipid-rich tissues. Follow-up observations showed marked resorption of marrow fat cells during the first weeks after injury, whereas very little bone was resorbed.

Cylindrical plugs of polymerized Simplex-P bone cement with and without barium sulfate were implanted in the rabbit tibial metaphysis. Titanium was used as control material. The animals were observed for 4--4.5 months. Histological analysis showed that all titanium implants were healed into the bone with a direct bone-implant contact, which was also true for about 60% of the cement implants. The remaining cement implants were encapsulated by connective tissue, probably due to biomechanical factors. It was not possible in this study to show a difference in the tissue reaction to bone cement containing barium sulfate and bone cement free from barium sulfate.

Twenty-one total hip arthroplasties were revised because of aseptic loosening. The bone and soft tissue membrane bordering the cement in a total of 37 biopsies from the acetabulum and femur were studied histologically and by enzyme histochemistry. The soft tissue membrane was infiltrated with macrophages and had high acid phosphatase activity. Other inflammatory cells were rare or absent. Concomitant bone formation and bone resorption were usually present at the bone-soft tissue border. The bone generally consisted of viable, remodeled lamellar bone. The host bone seemed to have been resorbed by a soft tissue front moving outward from the cement. Reactive new bone formation began at the bone-soft tissue border and appeared to constrain the resorptive process. Articular wear seemed to play no part in initiating the loosening process. The role of bone cement in this respect is obscure, because there were no obvious local signs of cytotoxicity. These observations support the theory of mechanical instability as the primary cause of the tissue reaction.

The aim of the present investigation was to evaluate if a bone cement monomer with a high concentration of accelerator (N,N-dimethyl-p-toluidine) is more toxic than a methyl methacrylate monomer, free from accelerator. 1) No difference in the acute local toxicity between CMW, Simplex-P and pure methyl methacrylate monomer was seen. 2) By gas chromatography. N,N-dimethyl-p-toluidine was shown to be water soluble to a small extent. Any bone cement monomer in current use can be fully dissolved in saline to a concentration of about 1 per cent.

The chemical effect of polymerizing CMW and Simplex-P bone cements was recorded by intravital microscopy in the hamster's cheek pouch. Thermal effects and pressure on the tissue were eliminated. Where a direct cement-tissue contact was present, severe, apparently irreversible, microcirculatory disturbances were recorded. Both cements caused equally extensive microvascular damage. Intact epithelium and connective tissue appeared to protect the underlying vascular bed from the effect of the monomer. No differences in tissue reaction were recorded when the cement past was applied after normal and prolonged kneading.

A method for high-resolution study of the interaction of bone and polymeric materials is described. By creating a 'mosaic' surface of polymer and pure titanium, using the titanium as an internal control, the tissue influence of the polymer surface can be deduced.