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PubMed1996

A method for shape optimization of a hip prosthesis to maximize the fatigue life of the cement.

The long term success of total joint replacement can be limited by fatigue failure of the acrylic cement and the resulting disruption of the bone-cement interface. The incidence of such problems may be diminished by reduction of the fatigue notch factor in the cement, so that stress concentrations are avoided and the fatigue crack initiation time maximized. This study describes a method for numerical shape optimization whereby the finite element method is used to determine an optimal shape for the femoral stem of a hip prosthesis in order to minimize the fatigue notch factor in the cement layer and at interfaces with the bone and stem. A two-dimensional model of the proximal end of a femur fitted with a total hip prosthesis was used which was equivalent to a simplified three-dimensional axisymmetric model. Software was developed to calculate the fatigue notch factor in the cement along the cement/stem and cement/bone interfaces and in the proximal bone. The fatigue notch factor in the cement at the cement/stem interface was then minimized using the ANSYS finite element program while constraining the fatigue notch factor at the cement/bone interface at or below its initial level and maintaining levels of stress in the proximal bone to prevent stress shielding. The results were compared with those from other optimization studies.

Algorithms↗
PubMed1999

Temperature elevation caused by bone cement polymerization during vertebroplasty.

Percutaneous vertebroplasty (PVP), whereby polymethylmethacrylate cement is injected into the vertebral body (VB), has been used to successfully treat various spinal lesions. The mechanism responsible for the palliative effect of PVP is unknown, but it may be the result of neural damage caused by heat liberated during polymerization of the polymethylmethacrylate. The purpose of the current study was to measure in vitro temperature histories at three key locations (anterior cortex, center, spinal canal) in VBs injected with one of two different bone cements (Simplex P and Orthocomp) to determine the role temperature plays in PVP. Twelve VBs (T11-L2) from three elderly female spines were instrumented with thermocouples and injected with 10 cc of one of the two cements. Temperatures were measured with the VBs in a bath (37 degrees C) for 15 min after injection. A Student's paired t-test was used to determine differences in peak temperature and time above 50 degrees C between the two cement groups. Peak temperatures and temperatures above 50 degrees C were significantly higher and longer, respectively, at the center of VBs injected with Simplex P (61.8 +/- 12.7 degrees C; 3.6 +/- 2.1 min) than those injected with Orthocomp (51.2 +/- 6.2 degrees C; 1.3 +/- 1.4 min). There was no significant difference in peak temperature between cements at the spinal canal location; temperature there did not rise above 41 degrees C. Although thermal damage to intraosseous neural tissue caused by cement polymerization cannot be ruled out as a potential mechanism for pain relief experienced by patients subsequent to PVP, it seems unlikely based on the worst-case conditions tested in the current study.

Aged↗
PubMed1999

Effects of various adjuvants (lactic acid, glycerol, and chitosan) on the injectability of a calcium phosphate cement.

Calcium phosphate cements are well-known orthopedic materials for filling bone. Various formulations are proposed. The current challenge is to place the material in the surgical site by methods as least invasive as possible. One approach consists of making the cement injectable by incorporation of various adjuvants. However, the requirement properties of the cement must be preserved: setting times suited to a convenient delay with surgical intervention, limited disintegration in aqueous medium, and sufficient mechanical resistance. Various additives were studied: in particular, lactic acid, glycerol, chitosan, and sodium glycerophosphate. Injectability, setting time, disintegration, and toughness after 10 days were followed in vitro. Glycerol greatly improved injectability and increased setting time, but decreased mechanical properties. Lactic acid reduced setting time, increased toughness of the material, but limited the dissolution rate. After injection, the cement did not present any disintegration. The effects lactic acid were correlated with the formation of calcium complex. Its association with sodium glycerophosphate is particularly interesting. Chitosan alone improved injectability, increased setting time, and limited the evolution of the cement by maintaining the OCP phase. Only slight disintegration was observed. These first results show that is possible to transform the cement into an injectable paste by addition of adjuvants without fundamentally modifying the chemical reactions occurring during setting and hardening.

Adjuvants, Pharmaceutic↗
PubMed1999

Volume effect on biological properties of a calcium phosphate hydraulic cement: experimental study in sheep.

Injectable calcium phosphate hydraulic cements (CPHC) are a new family of bone substitutes within the class of bone reconstruction biomaterials. In this work, CPHC were tested in two consistencies (preset blocks or liquid paste) in an experimental model of cancellous bone defect in sheep. The defects were eight times larger than those investigated previously in rabbits. Three delays (12, 24, and 52 weeks) were used. Before death, a double label of oxytetracycline and alizarine was made intravenously. The distribution of implants was randomized, histomorphometric evaluation was performed and compared with micrographic observation, and optical microscopy of stained sections was performed either under visible, ultraviolet, or polarized light. The results were compared with spontaneous healing of empty defects and with a control group of normal cancellous bone from sheeps of the same age. No significant difference has been observed between premolded and injected implants. In the sheep model, the degradation and new bone formation rates are three times slower, compared with those observed previously in rabbits. New bone formation increased from 5.9% (12 weeks) up to 11.0% (24 weeks) in the empty defect group. In the cement groups, 28.3% new bone was obtained at 12 weeks, which seemed then to level off (27.8% new bone at 24 weeks). Cement residues appear as radio-opaque cylinders on microradiographs. In all cases, a radiolucent layer was observed at the cement/bone interface at 24 weeks. Stained sections showed the formation of a fibroconnective capsule around the residual cement, which presumably slows down new bone formation. Nevertheless, quantitative bone remodeling was accelerated in the cement group; mineral apposition as well as adjusted apposition rates were higher, and the formation period as well as the mineralization of osteoid tissue were faster compared with empty cavities and controls. These results point to higher osteoblast activity and better exchange with surrounding tissues in the defects filled with cement.

Animals↗
PubMed2005

[Investigation about the clinical use of brushite- and hydroxylapatite-cement in sheep].

For future clinical use as synthetic bone replacement, an injectable brushite-(chronOS-Inject) and hydroxylapatite-(Biobon) cement were compared in a drill hole model in 10 sheep over time at 2, 4, 6, 8, 16 and 24 weeks. Results were compared regarding their practical use, biocompatibiliy, resorption mechanism and subsequent new bone formation. The cements were filled into drill holes (psi 8 x 13mm) of the proximal and distal humerus, and femur and the samples evaluated macroscopically, radiologically and microscopically including histomorphometrical quantification of percentages of new bone, fibrous tissue and remnants of cements. The cement area decreased continuously from 2 to 24 weeks with chronOS-Inject, as well as the area of granules. Inversely, the subsequent new bone formation increased from 2-24 weeks accordingly. With Biobon the cement area decreased slower between 2 and 24 weeks, and the new bone formation was less. Both cements were well integrated into the bone in long bones. chronOS-Inject demonstrated good biocompatibility and was almost completely replaced through bone within 24 weeks. Biobon was resorbed considerably slower and initially a slight inflammatory reaction including bone resorption was observed within the adjacent host bone.

Absorbable Implants↗
PubMed2003

The effect of oscillation, low seating force and dentine surface treatment on pulpward pressure transmission during crown cementation: a laboratory study.

The aim of the present research was to evaluate intra-pulpal pressure with respect to a combination of factors that are known to reduce pulpward pressure transmission in the laboratory while maintaining acceptable seating of the crowns. Thirty premolars were prepared for full crowns and individual crowns were cast. Ten teeth were etched prior to crown cementation with 100 N seating force. Crowns of groups 2 and 3 were cemented with 10 N force, after dentine sealing with bonding agent. Group two received, in addition, oscillating seating force during cementation. Pulp chamber pressure during cementation and marginal seating discrepancy after cementation were recorded. Group 1 showed significantly higher pressure mean 600 Pa and better crown seating (mean -22 microm) compared with group two (mean 144 Pa and 24 microm) and group 3 (mean 102 Pa and 44 microm) (P=0.001). Low seating forces combined with die spacer and sealing of dentinal tubules resulted in significant reduction of pressure transmitted into the pulp chamber during crown cementation. It is suggested that pre-impression sealing of dentine be considered for crown preparations on vital teeth.

Bicuspid↗
PubMed2003

Dual-setting calcium phosphate cement modified with ammonium polyacrylate.

alpha-Tricalcium phosphate bone cement, as formerly designed and developed by Driessens et al., consists of a powder composed by alpha-tricalcium phosphate (alpha-TCP) and hydroxyapatite (HA) seeds, and an aqueous solution of Na2HPO4 as mixing liquid. After mixing powder and liquid, alpha-TCP dissolves into the liquid and calcium deficient hydroxyapatite (CDHA), more insoluble than the former, precipitates as an entanglement of crystals, which causes the setting and hardening of the cement. alpha-TCP bone cement offers several advantages in comparison to calcium phosphate bioceramics and acrylic bone cements as bone graft and repairing material, like perfect adaptability to the defect size and shape, osteotransductibility, and absence of thermal effect during setting. The main handicap is its low mechanical strength. Therefore, approaching its mechanical strength to that of human bone could considerably extend its applications. In the present work, an in situ polymerization system based on acrylamide (AA) and ammonium polyacrylate (PA) as liquid reducer was added to alpha-TCP cement to increase its mechanical strength. The results showed that the addition of 20 wt% of acrylamide and 1 wt% AP to the liquid increased the compressive and tensile strength of alpha-TCP bone cement by 149 and 69% (55 and 21 MPa), respectively. The improvement in mechanical strength seems to be caused by a decrease of porosity and the reinforcing effect of a polyacrylamide network coexisting with the entanglement of CDHA crystals. The studied additives do not affect the nature of the final product of the setting reaction, CDHA, but promote the reduction of its crystal size.

Acrylic Resins↗
PubMed2002

A case report: reconstruction of a damaged knee following treatment of giant cell tumor of the proximal tibia with cryosurgery and cementation.

OBJECTIVE: Reconstruction of a knee damaged by cement packed to cure a giant-cell tumor is sometimes difficult. We reconstructed such a knee by removal of the cement, autologous bone transplantation and distraction osteogenesis using the Ilizarov apparatus. In this paper the results 29 months after the salvage surgery are given. PATIENT AND METHODS: We saw a 31-year-old woman's knee joint that showed osteoarthritic change after curettage, cryosurgery and cementation performed 4 years previously for a giant-cell tumor of the proximal tibia. We reconstructed the knee joint. This procedure included cement removal, alignment correction by tibial osteotomy, subchondral bone reconstruction by autologous bone transplantation, and filling the defect after removing the bone cement by elongating the diaphysis using the Ilizarov apparatus. RESULTS: Distraction was terminated 4 months later when 54 mm of elongation was performed. All devices were removed 12 months after the surgery. Seventeen months after the removal of the apparatus, the range of motion of the right knee was 0 degrees extension and 110 degrees flexion, and the patient was able to walk without pain. CONCLUSIONS: Although the treatment period is long and there may be some complications of Ilizarov lengthening and distraction osteogenesis, this procedure has numerous benefits. Bony defects can be soundly reconstructed and, at the same time, the alignment of the knee can be corrected. Also it is not necessary to reconstruct the ligaments because the insertions are intact. If osteoarthritis progresses, a surface type total knee replacement can be performed, not constrained type prosthesis, which would be used if the bony structure had not been reconstructed. This procedure may be one of the candidates for reconstructing such knee joints destroyed by bone cement.

Adult↗
PubMedDate not supplied

Removal of infected canine cemented total hip prostheses using a femoral window technique.

OBJECTIVE: To evaluate a femoral window technique for retrieval of cemented total hip prostheses. STUDY DESIGN: Retrospective clinical study. ANIMALS: Twelve dogs with infection of a cemented modular total hip prosthesis. METHODS: Implant removal was performed by an extended craniolateral approach to the hip and proximal femur without trochanteric osteotomy. The femoral cement mantle was fragmented and removed with simple orthopedic instrumentation by a lateral femoral window that was repaired using cerclage wires. Surgical technique, intraoperative and postoperative complications, bacterial culture results, histopathologic findings, and completeness of cement removal were recorded. Follow-up radiographs were taken 5 to 9 weeks postoperatively. Long-term follow-up information was obtained by client questionnaire. Functional outcome was assessed by scoring ability to stand, sit, walk, run, play, climb stairs, and get into a car. RESULTS: Prosthesis retrieval was performed 2 to 41 months after implantation (median, 14 months). Complete removal of femoral cement was achieved in 10 dogs. A nondisplaced femoral fissure, extending proximally from the window, was an intraoperative complication in 2 dogs. Staphylococcus spp was most commonly isolated (6 dogs) from interfacial membrane samples. Systemic antibiotic therapy, dependent on susceptibility testing, was administered for 3 to 10 weeks postoperatively. There was radiographic evidence of osteotomy healing at 5- to 9-week reassessment. Recurrence of osteomyelitis was not observed. Long-term functional outcome was considered mildly abnormal. CONCLUSIONS: The lateral window was an effective technique for retrieval of retained femoral cement. CLINICAL RELEVANCE: Removal of an infected prosthesis using this technique generally resulted in a clinical outcome comparable to that with ab initio femoral head and neck excision.

Animals↗
PubMed2000

Irrigation and suction technique to ensure reliable cement penetration for total knee arthroplasty.

We describe a new technique to enhance the preparation of the cancellous bone surfaces in total knee arthroplasty using bone suction and pressure lavage irrigation. This technique provides dry bone surfaces on which to cement (which is particularly valuable if a tourniquet is not used) and improves significantly the penetration of cement into the tibial plateau as assessed on plain postoperative radiographs. We review the results of this new technique by analyzing depths of cement penetration on postoperative radiographs to assess whether this technique offers improvements in cement penetration and bone surface preparation. This technique offers a simple, quick, and reliable method of ensuring reliable cement penetration into the bony trabeculae during cemented total knee arthroplasty.

Aged↗
PubMed2001

A critical assessment of proximal macrotexturing on cemented femoral components.

We analyzed the cement-metal interface of 3 different types of femoral components that had proximal macrotexturing after in vitro insertion and after fatigue testing designed to produce debonding and micromotion. These components were compared with clinical retrieval specimens. The cement did not flow into the macrotexturing; rather, hollow, brittle volcanoes or calderas were formed. These fragile protrusions of cement become worn down or abraded by debonded components. This abrasion of cement may contribute to the early and aggressive osteolysis seen in some of these early failures with proximal macrotextured components. The formation of these volcanos and calderas can be aborted by placing bone-cement onto the macrotexturing before stem insertion. This simple technique allows the macrotexturing to be filled with cement.

Adult↗
PubMed2003

Primary hybrid total hip arthroplasty with a roughened femoral stem: integrity of the stem-cement interface.

One hundred and two consecutive cemented femoral stems were evaluated in 92 patients at an average 9-year follow-up and a minimum 5-year follow-up (range, 5-14 years). The stem used was cobalt chromium with a collar, normalization steps, and a roughened surface (Ra 40); the stem was inserted using contemporary cementing techniques. This series demonstrated a femoral component aseptic loosening rate of 2.0% and a femoral component survivorship of 97.2 +/- 2.0% at 10 years. One of 2 failed stems was revised at 95 months for failure at the cement-bone interface. The second failed stem showed failure at the cement-bone interface with incomplete debonding radiographically at 65 months. The remaining femoral components did not demonstrate any evidence of debonding at the stem-cement interface. These results compare favorably with other series of cemented femoral stems, as well as with those with a polished surface.

Aged↗
PubMedDate not supplied

[Increasing bone screw anchoring in the femur head by cement administration via the implant--a biomechanical study].

PURPOSE: Osteoporosis reveals a higher risk of fractures. Due to the lack of possibilities to anchor fixation elements, fracture treatment often turns out to be complicated. An experimental study served to investigate the extent to which the application of bone cement through a modified gliding screw (Dynamic Hip Screw DHS) would improve the screw anchoring in osteoporotic femoral heads. METHODS: Quasi-static compressive and torsional load tests were used to assess the desired improvement of the screw anchoring. Cadaver femur pairs served to compare the cement augmentation to the uncemented contralateral control. RESULTS: The improvement of the holding strength of the screw under static compressive and torsional load depended on the cement flow into the adjacent bone tissue. The filling with additional cement was only successful after having created a small hollow space at the screw tip with a special instrument. Consequently, under compression as well as torsion, the cement application yielded improvements from 17% up to several times as much. CONCLUSION: In the application of gliding screws in osteoporotic femoral heads, the locally limited cement application through the implant has been shown to be a biomechanical possibility to improve screw fixation.

Absorptiometry, Photon↗
PubMedDate not supplied

[Femoral fissure after cement restrictor implantation].

Cement restrictors are accepted parts of modern cementing technique and reduce the risk of revision. The restrictor should seal the intramedullary cavity to ensure sustained pressurization and optimal cement penetration into cancellous bone. Significant complications after use of a cement restrictor are rarely described. Dislocation and cement leakage are well known problems. We describe the occurrence of a femoral fissure after insertion of a resorbable Gelatine cement restrictor.

Aged↗
PubMed2005

Migration of the acetabular component: effect of cement pressurization and significance of early radiolucency: a randomized 5-year study using radiostereometry.

BACKGROUND: Cementing technique is a crucial factor in prosthesis fixation. No randomized studies have been published, however, comparing the outcome of conventional fingerpacking with the outcome of pressurization of the cement prior to cup insertion. PATIENTS AND METHODS: We randomized 50 THAs to either fingerpacking or sequential pressurization (including individual pressurization of each anchorage hole) and followed the patients with RSA for 5 years. The penetration of cement into the anchorage holes was measured on digital radiographs. Postoperative radiolucent lines around the cup were correlated to later RSA results. For clinical evaluation, we used SF-36 and HHS. RESULTS: The pressurized group of THAs was more stable regarding changes in inclination. We found no other difference in the migratory behavior. The cement penetration into the anchorage holes was deeper with the pressurization technique than with fingerpacking. For the whole group taken together, there was a strong relation between the presence of radiolucent lines as measured on the postoperative radiograph and later migration observed by RSA at 2 and 5 years. INTERPRETATION: Pressurization of the cement produced better cement penetration and increased the cup stability in terms of changes in inclination. Early findings of radiolucent lines can predict later unfavorable cup migration.

Acetabulum↗
PubMed2005

Micro-tensile bond strength between a resin cement and an aluminous ceramic treated with Nd:YAG laser, Rocatec System, or aluminum oxide sandblasting.

OBJECTIVE: The aim of this study was to evaluate the effect of different surface treatments on bond strength between In-Ceram Alumina (VITA) and Panavia Fluoro Cement (Kuraray), and to verify the association between bond strength values and the percentage of remaining cement on the ceramic surface. BACKGROUND DATA: Although several conventional surface treatments have been used on aluminous ceramic, no study investigated the effect of the Nd:YAG laser. METHODS: Nine In-Ceram Alumina blocks (10 x 10 x 6 mm) received three surface treatments: group 1, Al(2)O(3) sandblasting + silane; group 2, Al(2)O(3) sandblasting + Rocatec Plus + silane; and group 3, Al(2)O(3) sandblasting + Nd:YAG Laser + silane. Resin cement was applied and light cured, followed by the application of composite. Blocks were sectioned to obtain sticks with a cross-sectional area of 1.0 mm(2). Microtensile bond strength (microTBS) was recorded in a universal testing machine at a crosshead speed of 0.5 mm/min. Scanning electron microscopy images of the fractured areas were used to calculate the amount of remaining cement on the ceramic substrate. RESULTS: All treatments yielded statistically different microTBS values (MPa): group 1, 14.38(A); group 2, 20.09(B); and group 3, 23.21(C) (ANOVAand Tukey's test, alpha = 0.05). Pearson's correlation coefficient for microTBS x percentage of remaining cement was r = 0.92 (p < 0.05). CONCLUSIONS: The Nd:YAG laser was the most effective surface treatment, followed by Rocatec and Al(2)O(3) sandblasting. A strong positive association was found between bond strength values and percentage of remaining cement.

Aluminum Oxide↗
PubMed1988

Porous acrylic cement: evaluation of a novel implant material.

The preparation and some properties of in situ curing porous acrylic cement, a modification of the traditional bone cement, are described. Through numerous animal experiments, the behavior of the porous cement in a biological environment has been studied. The histological evaluation reveals that hard and soft tissues readily grow into the pores of the cement, thus anchoring the implant to the host tissues. Some inflammatory foci, decreasing in number with residence time, together with varying numbers of multinucleated giant cells were found occasionally in the tissues in and around implants. When implanted in soft tissues, the porous cement behaved favorably with respect to solid acrylic implants because of the immobility of the implants and the absence of ectopic hard tissue formation. The biocompatibility of porous acrylic cement is judged to justify clinical trials in plastic and reconstructive surgery.

Animals↗
PubMed1998

Effect of increasing temperature on the properties of four bone cements.

This investigation uses a laboratory model to evaluate the effects of a heated femoral stem on the biomechanical properties of four common acrylic bone cements. American Society for Testing Materials dog bone shaped acrylic cement specimens made at four test temperatures, 0 degree C, 23 degrees C, 37 degrees C and 50 degrees C, were tested for modulus, ultimate tensile strength, fracture toughness, and percent porosity. Fatigue strength was tested in Simplex P at 23 degrees C and 37 degrees C. The data allow direct comparison among four cement brands at each of the four temperature conditions. No adverse changes of the mechanical properties were found for any cement at any temperature. Modulus, fracture toughness, and fatigue strength were unaffected by increased temperature. Ultimate tensile strength increased in Simplex P and Zimmer Osteobond but was unaffected for Zimmer Regular and Palacos R cements. Percent porosity was related to temperature changes inversely in all brands studied, except for Palacos R which consistently had low porosity, unaffected by temperature variation. Fatigue strength of Simplex P was unaffected by heating to 37 degrees C. Based on this laboratory model, heating of the femoral stem could save time without sacrificing mechanical properties of acrylic bone cement.

Biomechanical Phenomena↗