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PubMed1991

Hardening of dual-cured cements under composite resin inlays.

This study was conducted to determine the extent of hardening of three dual-cured cements under composite resin inlays and to determine the effectiveness of a light-reflecting wedge in promoting curing of the cements in the proximal margin. The exposure times needed to optimally harden the cements were determined by directly exposing the cements to the curing light. Composite resin inlays were bonded in an extracted molar with Dual cement, Dicor light-activated cement, and Duo cement. Cure-Thru reflective wedges were placed in the gingival embrasure of half of the specimens. None of the cements hardened completely by 24 hours when we used an exposure time that met or exceeded that recommended by the manufacturers. The chemical-cure component did not completely cure the cements when light was attenuated by the tooth and restoration. The light-transmitting wedge had little effect on hardening of the cements.

Analysis of Variance↗
PubMed1998

A simple method of increasing the adhesion between resinous cements and tinplated gold alloys: a pilot study.

PURPOSE: This study: (1) tested 2 BIS-GMA resinous cements on tinplated gold alloy surfaces with shearing forces to record their bond strengths, and (2) determined whether storage of the tinplated surfaces in water before cementation affected initial bond strengths. MATERIAL AND METHODS: The bond strengths of Panavia Ex and Panavia 21 resinous cements to tinplated Type III gold alloy were measured when subjected to shearing forces. Specimens were luted in pairs with these cements. In one group, the cementation was performed after tinplating procedures. In the other group, tinplated alloy surfaces were first stored in water at 37 degrees C for 48 hours before cementation. RESULTS: A 3-fold increase in bond strength values was recorded for tinplated specimens stored in water before cementation with both cements, these differences were statistically significant. Storage of the specimen in water before cementation appeared to increase resistance of the alloy resin bond to failure with application of shearing forces. CONCLUSION: This pilot study suggested that it would be advantageous to age tinplated gold alloy surfaces in water for 48 hours before cementation.

Bisphenol A-Glycidyl Methacrylate↗
PubMed2001

The influence of mixing ratio on the toughening mechanisms of a hand-mixed zinc phosphate dental cement.

OBJECTIVE: A range of mixing ratios occur for zinc phosphate cements in clinical usage and trials. The compressive strength of these cements is dependent on mixing ratio and at a critical ratio, a sudden rise in compressive strength is known to occur. This study investigated the mechanisms behind the cement curve behavior in an attempt to explain the strength increase with mixing ratio. METHODS: Crack propagation from indentations produced in cements were examined to identify if any variation in toughening mechanism existed over the range of mixing ratios investigated (1.7-3.2g/ml). Pore distribution within the cylindrical specimens was determined using an image analysis technique. RESULTS: Increasing the powder content from 2.3 to 2.4g/ml increased the number of powder agglomerates formed in the cement mix over individual particles. The likelihood of introducing pores in excess of 42 microm diameter was enhanced when the ratio exceeded 2.6g/ml. SIGNIFICANCE: It is proposed that crack deflection by agglomerates in the cement reduces the energy of the crack fronts emanating from indentations more than would occur with individual powder particles. This decreases the cracks ability to progress and is likely to result in the marked strength increase from 2.3 to 2.4g/ml identified previously. It is suggested that cement pores in excess of 42 microm diameter were probably generated on filling the sample molds with more viscous cements. These results emphasise that the properties of cements manipulated under optimum conditions provide little information on the cement characteristics present in clinical practice.

Compressive Strength↗
PubMed2002

Radiopacity in bone cements using an organo-bismuth compound.

In a joint replacement surgery it is vital for bone cement to be radiologically detectable. Consequently, heavy metal salts of barium and zirconia are incorporated as a contrast medium for this purpose. The addition of such particulate additives, however, can be detrimental to some of the physical, mechanical and biological properties. The present study reports the feasibility of using an organo-bismuth compound, namely. triphenyl bismuth (TPB) as a radiopaque agent for orthopaedic bone cements. TPB was incorporated in the bone cement matrix by two methods, (i) blending: TPB was added to the polymer phase of the bone cement and (ii) dissolution: by dissolving TPB in the monomer phase methylmethacrylate. The results showed that the inclusion of TPB at concentrations of 15% and 25% by weight of the polymer, in the bone cement matrix did not affect the polymerisation exotherm temperature and setting time. Furthermore, the addition of TPB via the dissolution method provided a statistically significant increase in the strain to failure in comparison to commercial acrylic cements containing barium sulphate, thus reducing the brittleness of the cement. The detrimental effects on the mechanical properties post conditioning in water, was also much less pronounced in the homogeneous TPB cements in comparison to barium sulphate containing cements. These observations can be attributed to the formation of a homogeneous and continuous matrix of the resultant bone cement with a much lower porosity.

Bismuth↗
PubMed1999

Attachment of PMMA cement to bone: force measurements in rats.

The attachment of an implant material to bone relates to surface roughness and surface chemistry. There is a relatively low chemical bonding strength of so-called bioactive surfaces. Hydroxyapatite interfaces typically have an interfacial tensile strength of 0.15-1.5 MPa. An attachment force similar to that of bioactive surfaces might also be reached through mechanical interlock with ordinary bone cement. This study measured bone cement interfacial tensile strength for polished (R(a) 0.5 microm) and regular (R(a) 4.8 microm) vacuum mixed PMMA bone cement. Bone bonding was evaluated by a detachment test. We used unloaded cement surfaces, which could be detached from the bone. Titanium plates were developed such that a cement fill was contained within a plate, which was contained within a titanium holder. The cement surface came into contact with traumatized bone only, and the rest of the plate had no contact with tissue. The cement surface was either polished or left untreated after conventional preparation. Four weeks later, the plates were detached from the bone by a perpendicular force. The detaching load of the polished cement surface never exceeded 0.07 MPa, whereas for unpolished cement there was a load up to 0.9 MPa. The results suggest that surface irregularities and microinterlock enable an attachment that can resist tension between bone and a cement surface.

Animals↗
PubMed2000

Osteoconductivity of an injectable and bioresorbable poly(propylene glycol-co-fumaric acid) bone cement.

We have investigated an injectable form of a resorbable bone cement based on in situ crosslinking of the unsaturated polyester, poly(propylene glycol-co-fumaric acid) (PPF). This material, filled with calcium gluconate/hydroxyapatite (CG/HA), cures to a hard cement degradable by hydrolysis. The purpose of this study was to evaluate the osteoconductive properties of this injectable cement. The cement was used as an adjunct to fixation with an intramedullary rod in the rat femoral osteotomy model. Ingrowth of new bone into the cement was examined in vivo. Negative and positive controls with rigid and loose internal fixation were included for comparison. Animals were evaluated histologically and histomorphometrically at 4 weeks postoperatively. Results of this study showed osteoblastic activity and new bone formation at the interface between the femoral bone and the cement in the experimental group. However, there was little bone remodeling at the endosteal surface in positive and negative controls. Histologic evaluation of the cement revealed the formation of cavitations, which likely resulted from leaching of the highly soluble calcium gluconate portion of the filler from the cement. These cavitations were sites of ingrowth of vascular and bony tissues. Intimate contact between the bone cement and the endosteal surface of the cortex was found. Quantitative histomorphometric analysis corroborated these observations. Findings of this study demonstrated the osteoconductivity of this type of injectable PPF-based bone cement.

Animals↗
PubMed1996

Acrylic bone-cement. Influence of mixer design and unmixed powder.

The effects of hand mixing with two different mechanical mixing systems (fixed versus rotating central axis) on unmixed powder content, macroporosity, density, and bending strength of acrylic bone-cement are compared. The effects of voids and unmixed powder on cement bending strength are also evaluated. In acrylic cement, both unmixed powder monomer and voids 1 mm and larger can be easily visualized and analyzed on radiographs of 3-mm-thick samples. Image analysis allowed demonstration of a significant increase in unmixed powder content (P < .0001), in cement prepared using a vacuum mixing system with a fixed central axis compared with both the rotating axis system and hand mixing. The rotating-axis system produced cement of higher density compared with hand mixing only (P = .004). There was a significant correlation between the number of voids measured per square centimeter and cement bending strength (P < .0001), as well as an independent and significant correlation between unmixed powder content and cement bending strength (P < .0001). Mechanical mixing using a fixed central axis produced significantly weaker cement compared with both hand mixing (P < .015) and the rotating-central-axis system (P < .0001). A 15% drop in strength between the two mechanical mixing systems was observed. It is therefore concluded that the use of different rotating systems in mechanical mixers can influence void and unmixed powder content and, consequently, the mechanical properties of acrylic cement, and that unmixed powder is an independent factor affecting the bending strength of the cement.

Acrylates↗
PubMed2001

A clinical retrospective evaluation of 2 orthodontic band cements.

This study aimed to compare the time to first failure of stainless steel orthodontic first permanent molar bands cemented with either a modified composite (Band-Lok, Reliance Orthodontic Products) or a conventional glass ionomer cement (AquaCem, De Trey Dentsply). The effect of patient sex, patient age at the start of treatment, the presenting malocclusion, treatment mechanics, and the operator proficiency on band survival was also assessed. Data for 219 bands cemented with Band-Lok in 108 patients and for 395 bands cemented with AquaCem in 183 patients were analyzed. For each case, a single molar band, either the band that was first to fail or the band that had the shortest follow-up time, was chosen for analysis. For each cement, whether headgear was used or not, there was no significant difference in time to first band failure (P = .398). Twenty-six percent of patients had at least one band failure with Band-Lok, and 30% of patients had at least one band failure with AquaCem, representing an 18% band failure rate for each cement. There was no significant difference in time to first band failure for either cement with respect to sex of the patient (P = .842), patient age at the start of treatment (P = .257), presenting malocclusion (P = .319), or operator proficiency (P = .062). The use of headgear, however, reduced significantly the time to first band failure irrespective of cement type (P = .0069). Headgear use was identified as a predictor of first permanent molar band survival. Clinical performance of bands cemented with either cement appears to be similar and was influenced significantly by the use of headgear.

Acrylic Resins↗
PubMed1998

The role of maleic anhydride in adhesive resin cements.

The adherence of resin cements depends upon, among other factors, the polar interactions across the interface: resin cement/restorative material. The polar interactions may be augmented by inclusion of polar additives such as maleic anhydride to the cement monomer. However, maleic anhydride is slowly converted to maleic acid when exposed to an aqueous environment. This may affect mechanical properties of such a cement in a negative way. It was the aim of the present investigation to analyze the role of maleic anhydride dissolved in the monomer of resin cements. The resin cement monomers used were common methacrylates, to which maleic anhydride in amounts of up to 30 mol% was added. Polymerization initiators were included to make the materials dual curing. Finally, the preparations were mixed with silanated fillers. The adherence energy of the cements bonded to a chromium-cobalt alloy was assessed by means of the double cantilever beam test. The strength and stiffness of the resin cements were recorded at base line and after two months storage in water. The initial adherence energy increased by a factor of about two as a result of addition of maleic anhydride. However, resin cements containing maleic anhydride suffered significant reductions in long-term adherence, strength and stiffness. These reductions were particularly pronounced in non-irradiated specimens. The use of resin cements containing maleic anhydride is not a viable means of conveying adhesiveness to resin cements.

Adhesiveness↗
PubMed2004

Reconstruction of post-traumatic frontal-bone depression using hydroxyapatite cement.

The safety and efficacy of hydroxyapatite cement (Bone Source, Howmedica, Leibinger, Inc. Dallas, TX) use for the augmentation of post-traumatic frontal-bone depression was evaluated in a study of 20 consecutive oriental patients between June 1998 and July 2000 inclusively. The size of the depressed frontal bone ranged from 5 x 5 cm to 8 x 5 cm. The cement was placed in contact with the frontal sinus for 12 patients, none of whom revealed a history of paranasal sinus mucoperiosteal disease. Follow-up averaged 28 months for all 20 patients. Postimplantation evaluations included serial photographs, repeated physical examination, and 3-dimensional computed tomography for all patients. The cement paste allowed for precise and easy contouring of the bony depression's restoration. Meticulous hemostasis is essential to ensure a dry surgical field and successful application of the cement. No infection of the surgical site or extrusion of the cement was noted for any of our patients, and the contour of the reconstructed frontal bone was acceptable esthetically without any secondary depression noted during the follow-up period. Three-dimensional computed tomographic scans taken 2 years subsequent to implantation revealed good preservation of the cement restoration material. Small areas of cement loss due to cement absorption into the ambient fluid were noted for 2 patients, but such resorption did not appear to esthetically influence the final results. The results from this clinical study indicated that hydroxyapatite cement is a biocompatible, alloplastic material useful for augmentation of post-traumatic frontal-bone depression with stable volume maintenance over time. Judicious use of the hydroxyapatite cement offers an alternative to autogenous bone grafts or the use of methyl methacrylate for augmentation of the craniofacial skeleton among oriental patients.

Bone Cements↗
PubMed2005

Exothermal characteristics and release of residual monomers from fiber-reinforced oligomer-modified acrylic bone cement.

The aim of this study is to determine the peak temperature of polymerization, the setting time and the release of residual monomers of a modified acrylic bone cement. Palacos R, a commercial bone cement, is used as the main component. The cement is modified by adding short glass fibers and resorbable oligomer fillers, and an additional cross-linking monomer. The test specimens are classified according to the composition of the bone cement matrix (i.e., oligomer-filler, glass-fiber reinforcement, and/or cross-linking monomer). The exothermal characteristics during autopolymerization are analyzed using a transducer connected with a computer. The quantities of residual monomers were analyzed from different test groups using high performance liquid chromatography (HPLC). The DeltaT value for the oligomer filler and the glass-fiber-containing acrylic bone cement is lower than that for the unmodified bone cement (2.1 +/- 0.8 vs. 23.5 +/- 4.2 degrees C). The addition of a cross-linking monomer, EGDMA, shortens the setting time of the autopolymerization of the unmodified bone cement (7.1 +/- 0.9 min vs. 3.3 +/- 0.3 min). The quantity of the residual monomers released is higher in the modified bone cement than that in the unmodified cement. The cement that contains glass fibers and oligomer fillers has a considerably lower exothermal peak, whereas the total quantity of residual monomers released is increased.

Cementation↗
PubMed2005

SRS cancellous bone cement augmentation of calcaneal fracture fixation.

BACKGROUND: The proper treatment of intraarticular calcaneal fractures remains controversial. The goal of operative treatment is to achieve anatomic reduction with stable internal fixation. One method for stabilizing fracture constructs is the use of calcium phosphate bone cement. The goal of this study was to evaluate a series of patients who had open reduction and internal fixation of intra-articular calcaneal fractures with calcium phosphate bone cement augmentation. METHODS: Fifteen patients had open reduction and internal fixation through an extensile lateral approach with standard low-profile hardware. The walls of the bone defect beneath the posterior facet were impacted with a curette and the void filled with SRS bone cement. Preoperative and postoperative plain radiographs and computed tomography (CT) were obtained on each patient. The most recent radiographs were assessed for maintenance of reduction. RESULTS: Nine patients were followed for an average of 13 (6 to 60) months. Six patients had less than 6 months followup. There were five type IIA, five type IIB, four type IIC, and one type IIIB-C fractures. All 15 fractures were noted on postoperative CT to have less than 2-mm of step-off with complete cement fill of the bony void. None of the patients developed a soft-tissue reaction to the cement. The first six patients were allowed to bear weight 6 weeks after injury, and the following nine patients were allowed to bear weight at 3 weeks after injury. No patient had any visible loss of reduction on most recent radiographs. Followup CT at 7 months in one patient and 12 and 51 months in another patient revealed no change in the bone-cement interface or amount of cement remaining. One patient's CT at 12 months revealed apparent fragmentation of the cement mass without loss of reduction. There was one major wound complication necessitating cement and hardware removal and free flap coverage. CONCLUSION: In this small series, patients had no evidence of soft-tissue reaction or loss of reduction with early weightbearing after open reduction and internal fixation augmented with calcium phosphate bone cement.

Adult↗
PubMed1997

Acrylic cement creeps but does not allow much subsidence of femoral stems.

It has been suggested that the endurance of cemented femoral reconstructions in total hip arthroplasty is affected by the creep of acrylic cement, but it is not known to what extent cement creeps under loading conditions in vivo, or how this affects load transfer. We have simulated the long-term creep properties of acrylic cement in finite-element models of femoral stem constructs and analysed their effects. We investigated whether subsidence rates measured in vivo could be explained by creep of acrylic cement, and if polished, unbonded, stems accommodated creep better than bonded stems. Our findings showed that polished prostheses subsided only about 50 microm as a result of cement creep. The long-term prosthetic subsidence rates caused by creep of acrylic cement are therefore very small and do not explain the excessive migration rates which have sometimes been reported. Cement creep did, however, relax cement stresses and create a more favourable stress distribution at the interfaces. These trends were found around both the bonded and unbonded stems. Our results did not confirm that polished, unbonded, stems accommodated creep better than bonded stems in terms of cement and interface stress patterns.

Acrylic Resins↗
PubMed1999

Cement migration after THR. A comparison of charnley elite and exeter femoral stems using RSA.

Studies using roentgen stereophotogrammetric analysis (RSA) have shown that the femoral components of cemented total hip replacements (THR) migrate distally relative to the bone, but it is not clear whether this occurs at the cement-implant or the cement-bone interface or within the cement mantle. Our aim was to determine where this migration occurred, since this has important implications for the way in which implants function and fail. Using RSA we compared for two years the migration of the tip of the stem with that of the cement restrictor for two different designs of THR, the Exeter and Charnley Elite. We have assumed that if the cement restrictor migrates, then at least part of the cement mantle also migrates. Our results have shown that the Exeter migrates distally three times faster than the Charnley Elite and at different interfaces. With the Exeter migration was at the cement-implant interface whereas with the Charnley Elite there was migration at both the cement-bone and the cement-implant interfaces.

Aged↗
PubMed2006

CT analysis of defects of the cement mantle and alignment of the stem: in vitro comparison of Charnley-Kerboul femoral hip implants inserted line-to-line and undersized in paired femora.

Using a modern cementing technique, we implanted 22 stereolithographic polymeric replicas of the Charnley-Kerboul stem in 11 pairs of human cadaver femora. On one side, the replicas were cemented line-to-line with the largest broach. On the other, one-size undersized replicas were used (radial difference, 0.89 mm sd 0.13).CT analysis showed that the line-to-line stems without distal centralisers were at least as well aligned and centered as undersized stems with a centraliser, but were surrounded by less cement and presented more areas of thin (< 2 mm) or deficient (< 1 mm) cement. These areas were located predominantly at the corners and in the middle and distal thirds of the stem. Nevertheless, in line-to-line stems, penetration of cement into cancellous bone resulted in a mean thickness of cement of 3.1 mm (sd 0.6) and only 6.2% of deficient and 26.4% of thin cement. In over 90% of these areas, the cement was directly supported by cortical bone or cortical bone with less than 1 mm of cancellous bone interposed. When Charnley-Kerboul stems are cemented line-to-line, good clinical results are observed because cement-deficient areas are limited and are frequently supported by cortical bone.

Arthroplasty, Replacement, Hip↗
PubMed2002

A biomechanical analysis of fixation of intra-articular distal radial fractures with calcium-phosphate bone cement.

BACKGROUND: Calcium phosphate cement has been used to treat unstable fractures of the distal end of the radius with the intent of avoiding the stiffness and morbidity associated with prolonged immobilization in a cast or external fixation. The purpose of this study was to compare the stability of the fracture fragments after fixation with augmented calcium phosphate cement with that after alternative methods of percutaneous fracture treatment. METHODS: Both an osteotomy and osteoclasis were used to create a model of an intra-articular fracture of the distal part of the radius (AO type C2) with dorsal bone loss in seven pairs of fresh-frozen upper extremities. One wrist from each pair was fixed with an external fixator and three Kirschner wires, and the contralateral wrist was fixed with calcium phosphate cement (Norian SRS) and three Kirschner wires (augmented calcium phosphate cement). Sequentially increasing loads, up to a total of 100 N, were then applied to the major flexors and extensors of the wrist. Fracture fragment motion was measured by the Optotrak three-dimensional system. RESULTS: Fixation with cement alone failed at the bone-cement interface at <80 N in all specimens. With use of an analysis of variance, augmented external fixation was found to provide significantly increased stability to the radial fragment compared with that provided by augmented calcium phosphate cement in four of the six axes tested (e.g., mean motion [and standard deviation] in flexion-extension was 3.0 degrees +/- 2.93 degrees versus 11.1 degrees +/- 13.08 degrees, respectively; p = 0.001). Augmented calcium phosphate cement was found to provide greater stability for the radial fragment than were Kirschner wires alone in three axes (e.g., mean motion in flexion-extension was 11.1 degrees +/- 13.08 degrees versus 36.5 degrees +/- 13.03 degrees, respectively; p = 0.001). CONCLUSIONS: Calcium phosphate cement alone is insufficient to withstand physiologic flexion-extension motion of the wrist without supplemental wire fixation. When supplemented with Kirschner wires, fixation with bone cement is more stable than are Kirschner wires alone, but it is significantly less stable than augmented external fixation.

Biomechanical Phenomena↗
PubMed2003

rhBMP-2 release from injectable poly(DL-lactic-co-glycolic acid)/calcium-phosphate cement composites.

BACKGROUND: In bone tissue engineering, poly(DL-lactic-co-glycolic acid) (PLGA) microparticles are frequently used as a delivery vehicle for bioactive molecules. Calcium phosphate cement is an injectable, osteoconductive, and degradable bone cement that sets in situ. The objective of this study was to create an injectable composite based on calcium phosphate cement embedded with PLGA microparticles for sustained delivery of recombinant human bone morphogenetic protein-2 (rhBMP-2). METHODS: (125) I-labeled rhBMP-2 was incorporated in PLGA microparticles. PLGA microparticle/calcium-phosphate cement composites were prepared in a ratio of 30:70 by weight. Material properties were evaluated by scanning electron microscopy, microcomputed tomography, and mechanical testing. Release kinetics of rhBMP-2 from PLGA/calcium-phosphate cement disks and PLGA microparticles alone were determined in vitro in two buffer solutions (pH 7.4 and pH 4.0) for up to twenty-eight days. RESULTS: The entrapment yield of rhBMP-2 in PLGA microparticles was a mean (and standard deviation) of 79% +/- 8%. Analysis showed spherical PLGA microparticles (average size, 17.2 +/-1.3 micro m) distributed homogeneously throughout the nanoporous disks. The average compressive strength was significantly lower (p < 0.001) for PLGA and calcium-phosphate cement composite scaffolds than for calcium-phosphate cement scaffolds alone (6.4 +/- 0.6 MPa compared with 38.6 +/- 2.6 MPa, respectively). Average rhBMP-2 loading was 5.0 +/- 0.4 micro g per 75-mm (3) disk. Release of rhBMP-2 was limited for all formulations. At pH 7.4, 3.1% +/- 0.1% of the rhBMP-2 was released from the PLGA/calcium-phosphate cement disks and 18.0% +/- 1.9% was released from the PLGA microparticles alone after twenty-eight days. At pH 4.0, PLGA/calcium-phosphate cement disks revealed more release of rhBMP-2 than did PLGA microparticles alone (14.5% +/- 6.3% compared with 5.4% +/- 0.7%) by day 28. CONCLUSIONS: These results indicate that preparation of a PLGA/calcium-phosphate cement composite for the delivery of rhBMP-2 is feasible and that the release of rhBMP-2 is dependent on the composite composition and nanostructure as well as the pH of the release medium.

Bone Cements↗
PubMed2003

Contemporary total hip arthroplasty with and without cement in patients with osteonecrosis of the femoral head.

BACKGROUND: The rate of failure of primary total hip arthroplasty in patients with osteonecrosis of the femoral head is higher than that in patients with osteoarthritis. The purpose of this prospective study was to document the clinical and radiographic results of arthroplasty with so-called third-generation cementing and the results of second-generation cementless total hip arthroplasty in ninety-eight consecutive patients with osteonecrosis of the femoral head. METHODS: Fifty patients who had had simultaneous bilateral total hip arthroplasty with a cemented stem in one hip and a cementless stem in the other and forty-eight patients who had had a unilateral total hip arthroplasty with a cementless stem were included in the study. A cementless acetabular component was used in all hips. The presumed cause of the osteonecrosis was ethanol abuse in fifty-seven patients, unknown in twenty-seven, fracture of the femoral neck in nine, and steroid use in five. There were eighty men and eighteen women. The mean age at the time of the arthroplasty was 47.3 years (range, twenty-six to fifty-eight years). Clinical and radiographic evaluations were performed preoperatively; at six weeks; at three, six, and twelve months; and yearly thereafter. The average duration of follow-up was 9.3 years. RESULTS: The average Harris hip scores in the group treated with unilateral arthroplasty (97 points) and the group treated with bilateral arthroplasty (94 points) were similar at the time of final follow-up. They were also similar between the group treated with cement (mean, 96 points) and that treated without cement (95 points). No component had aseptic loosening in either group. In one hip, a cemented femoral stem (2%) and a cementless cup were revised because of infection. Two cementless stems (2%) were revised because of fracture of the proximal part of the femur with loosening of the stem. Annual wear of the polyethylene liner averaged 0.22 mm in the group treated with cement (a zirconia head) and 0.14 mm in the group treated without cement (a cobalt-chromium head). The prevalence of osteolysis in zones 1 and 7 of the femur was 16% in the group treated with cement and 24% in the group treated without cement. CONCLUSIONS: Advancements in surgical technique and better designs have greatly improved the long-term survival of cemented and cementless implants in young patients with osteonecrosis of the femoral head. Although there was no aseptic loosening of the components, a high rate of linear wear of the polyethylene liner and a high rate of osteolysis in these high-risk young patients remain challenging problems.

Adult↗