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PubMed2004

Acetabular cementing technique in THA--flanged versus unflanged cups, cadaver experiments.

BACKGROUND: There are few studies on the effect of acetabular cup design on cement penetration. MATERIAL AND METHODS: We evaluated the effects of an acetabular flange on cement pressurization and cement penetration in 12 cadavers. Flanged or unflanged cups were implanted in paired human acetabula with simulated intraosseous bleeding pressure but without cement pressurization before insertion of the cup. Three pressure transducers were used to record intra-acetabular peak and average pressures during cup insertion. Following implantation, the whole specimens were AP-radiographed and standardized sections through the acetabula were microradiographed to evaluate cement penetration. RESULTS: Flanged cups produced greater intra-acetabular peak pressures than unflanged cups, but did not increase the average intra-acetabular pressure. Cement penetration did not differ significantly between the two groups. INTERPRETATION: Our findings do not support the use of flanged cups as the sole means of cement pressurization in the acetabulum.

Acetabulum↗
PubMed2005

Pseudomonas aeruginosa biofilm formation and slime excretion on antibiotic-loaded bone cement.

BACKGROUND: Infection is an infrequent but serious complication of prosthetic joint surgery. These infections will usually not clear until the implant is removed and re-implantation has a high failure rate, especially when Pseudomonas aeruginosa is involved. MATERIAL AND METHODS: We examined Pseudomonas aeruginosa biofilm formation on plain and gentamicin-loaded bone cement with confocal scanning laser microscopy (CSLM). Two different stains were applied in order to visualize and quantify the distribution of bacterial cells and extracellular polymeric substances (slime) from the bone cement surface to the top of the biofilm. Staining with LIVE/DEAD viability stain differentiated between live and dead bacteria within the biofilm, and slime production was evaluated after staining with Calcofluor white. RESULTS: CSLM showed that the biofilm was a nonuniform structure of variable thickness, with differences in local bacterial cell and slime densities. Incorporation of gentamicin in bone cement resulted in a 44% reduction in bacterial viability, while the slime density increased significantly. In addition, conventional plate counting showed the development of small-colony variants on gentamicin-loaded bone cement with a decreased sensitivity for gentamicin (MIC: 8 m/L), as compared with normal-sized colonies taken from plain and gentamicin-loaded bone cement (MIC: 3 m/L). The enhanced slime production on antibiotic-loaded bone cement, together with the formation of small-colony variants, resulted in decreased susceptibility to antibiotics--probably concomitant with the onset of persistent and relapsing infections. INTERPRETATION: In the clinical situation, our findings help to explain the frequent re-implantation failure of joint replacements infected with P. aeruginosa when the procedure has been performed using antibiotic-loaded bone cement.

Anti-Bacterial Agents↗
PubMed2005

Evaluation of retention of post-core system cemented with different materials on dentine surfaces treated with EDTA or Er:YAG laser irradiation.

OBJECTIVE: The aim of this study was to evaluate in vitro the post-core system retention to dentine surfaces treated with EDTA and Er:YAG laser irradiation and cemented with resin or a tradiational zinc phosphate cement. BACKGROUND DATA: One of the factors related to intracanal post-retention is the root canal wall preparation. METHODS: Forty-eight samples were divided into three groups: (1) G1 (control), dentine surfaces with no treatment, irrigated with distilled and deionized water; (2) G2, 1% NaCIO + 17% EDTA; and (3) G3, water and Er:YAG laser (8 Hz, 200 mJ, 60 J, 300 pulses). Each group was subdivided into two subgroups depending on the cement used: Panavia F or zinc phosphate. All specimens were submitted to tensile load in the Universal Instron Machine (Instron 4444) at 0.5 mm/min. RESULTS: Data were analyzed statistically with ANOVA and Tukey's test, which showed no significant difference (p > 0.01) between the dentine wall treatments performed with 1% NaCIO + 17% EDTA (6.80 Mpa) and water + Er:YAG laser (6.81 MPa), independent of the cement used; however, these were statistically different (p < 0.01) from the control group that presented the lowest values (4.82 MPa). Cementing with Panavia F and zinc phosphate presented similar results for adhesive resistance (p > 0.05). CONCLUSION: We conclude that the previous treatment of dentine walls with 1% NaCIO + 17% EDTA, or Er:YAG laser + water favored retention of the post-core system cemented with both resin and zinc phosphate cement.

Dental Bonding↗
PubMed1996

Modern cement technique and the survivorship of total shoulder arthroplasty.

Thirty-eight consecutive Neer II total shoulder arthroplasties were performed in 35 patients by one surgeon using the so called modem cement technique and followed for a mean of 5 years (range, 2-9.5 years). The preoperative diagnosis was osteoarthritis or avascular necrosis in 22 shoulders, rheumatoid arthritis in 10 shoulders, and posttraumatic arthritis in 6 shoulders. The components were implanted using specific improved techniques for cement fixation initially described for total hip arthroplasty. Twenty-six metal-backed and 12 polyethylene glenoid components were used. The humeral component was implanted with cement in 32 shoulders. There were no intraoperative fractures or postoperative neurapraxias. At most recent followup, 36 shoulders had no or slight pain with activity. The mean increase in active forward elevation was 38 degrees and in active external rotation was 29 degrees. There have been no revisions, and all components remain in place. With failure defined as definite radiographic loosening of the components, there was 97% survivorship at 5 years, and 93% at 8 years. Radiolucent lines around more than 50% of the bone cement interface of the humeral component were present in only 3 shoulders. Radiolucent lines around more than 50% of the bone cement interface of the glenoid component were seen in only 2 shoulders. Both components in 1 severely osteopenic shoulder had a complete radiolucent line and a change in position. Meticulous attention to cement technique may improve the long term survival of cemented total shoulder arthroplasty components.

Adult↗
PubMed2000

Technical considerations of cemented acetabular components: a 30-year evaluation.

The effect of porosity reduction cementing techniques with respect to radiolucent lines in Zone 1 and failure in acetabular components was studied in 2,237 consecutive cemented acetabular components done between 1970 and 1998. The minimum followup was 2 years. Radiolucencies in Zone 1 on initial radiographs obtained postoperatively were tabulated for five groups of patients based on cementing techniques. The percentage of loose or revised cups was calculated for six groups based on type of prosthesis used. The lowest percentage of Zone 1 radiolucencies was in a group in which bowl mixing was used. The lowest failure rate was in the group that received Charnley prostheses in which simple first generation cement techniques were used. Porosity reduction techniques did not reduce the incidence of Zone 1 radiolucencies. For the acetabular side of a total hip replacement, the biology of the bone and the techniques of cement insertion that include a dry cancellous bone bed, perforation and removal of peripheral sclerotic areas, pressurization of the entire cement mantle in the socket at one time, and complete burying of the acetabular component within the boundary of the bony acetabulum are the essential factors, not porosity reduction in the cement.

Acetabulum↗
PubMed2004

Depot local anesthetic in polymethylmethacrylate bone cement: a preliminary study.

Acrylic bone cement has been used successfully as a slow-release depot for antibiotics after orthopaedic surgery. The feasibility of administering local anesthetics in this way was examined in this preliminary in vitro study. Discs weighing approximately 4 g were prepared from five brands of acrylic cement (40 g) containing as much as 2 g of anesthetic base. Elution of the anesthetics into saline was measured during 72 hours. Prilocaine eluted the fastest and bupivacaine the slowest, with lidocaine between them. The elution rates were greatest in the first hour, declining thereafter. Rates also depended on the brand of cement with the quickest elution from CMW3 and the slowest from Surgical Simplex P. Using cement as a depot, therapeutic levels of a drug should be achievable in vivo at a negligible risk of toxicity. Before in vivo trials it is necessary to optimize elution of drugs in relation to the cement (brand, microstructure, method of preparation) and the concentration of a drug in the cement above which the cements' mechanical and adhesive properties are compromised.

Anesthetics, Local↗
PubMedDate not supplied

Open reduction and augmentation of internal fixation with an injectable skeletal cement for the treatment of complex calcaneal fractures.

OBJECTIVES: To describe the surgical handling, potential complications, and remodeling of an injectable, osteoconductive calcium phosphate cement (Norian SRS) for joint depression-type calcaneal fractures in humans, and to illustrate the clinical efficacy of this cement with special reference to early postoperative full weight bearing. DESIGN: Prospective cohort study. SETTING: Level I trauma centers in Bochum and Leipzig, Germany. INTERVENTION: Thirty-six joint depression type calcaneal fractures in thirty-two patients were augmented with the calcium phosphate cement after standard open reduction with internal fixation. Postoperative full weight bearing was allowed progressively earlier, and as the study progressed, the last patients were bearing full weight as early as three weeks postoperatively. Biopsies for histologic analysis were performed at time of hardware removal after one year (seven biopsies) or in case of infection at time of debridement (five biopsies). MAIN OUTCOME MEASURES: Clinical outcome was evaluated according to a calcaneal scoring system. Data were compared and statistically analyzed between patients with postoperative full weight bearing after eight to twelve weeks and three to six weeks, respectively. Histologic findings are described. RESULTS: Cement injection averaged ten cubic centimeters and could easily be performed under fluoroscopic control. Progressively earlier full weight-bearing was achieved without loss of reduction. There was no statistical difference in clinical outcome scores in patients with full weight bearing before or after six weeks postoperatively. The infection rate was 11 percent, possibly related to the skin incisions. The biopsies from clinically satisfactory cases showed nearly complete bone apposition, areas of vascular penetration, and reversal lines illustrating progressive cycles of resorption and new bone formation. Biopsy specimens from infected cases showed bone and cement surrounded by either fibrous tissue or acute inflammation without extensive bone apposition. CONCLUSIONS: Calcium phosphate cement augmentation of standard open reduction with internal fixation in joint-depression type calcaneal fractures allows postoperative full weight bearing as early as three weeks postoperatively. The injectable bone cement can easily be handled surgically under fluoroscopic control and has proved to be remodelable.

Adult↗
PubMed2002

The effect of augmentation with resorbable or conventional bone cement on the holding strength for femoral neck fracture devices.

OBJECTIVES: To compare maximum extraction torque and pull-out load for femoral neck fracture implants inserted with standard technique or after augmentation with polymethylmethacrylate (PMMA) or calcium phosphate cement (Norian SRS). DESIGN: Biomechanical study using synthetic bone. INTERVENTION: Implants were inserted in foam blocks with three different densities for simulation of normal bone or slight or severe osteoporosis. Tested implants included three screws (AO, Olmed, Hansson), one screw with both threads and a barb (Hybrid), and one pin with a hook (LIH hook-pin). Implants were inserted by standard technique and after augmentation with PMMA or Norian SRS. MAIN OUTCOME MEASUREMENT: The effect of (a) density of the synthetic bone (low, medium, high), (b) augmentation (none, PMMA, SRS), and (c) type of implant (AO, Olmed, Hansson, Hybrid, LIH) on the maximum extraction torque and pull-out load was determined using a material testing machine. Analysis of variance with Fisher's PLSD post hoc test was used to determine statistical differences. RESULTS: PMMA significantly increased maximum torque and pull-out load for all implants and block densities when compared without cement (p < 0.0001), whereas enhancement with SRS was far less pronounced and most obvious in low density blocks. For screws normally inserted without predrilling (Olmed and Hansson) the use of SRS in high density blocks caused a significant reduction in maximum torque (p < 0.0001) and pull-out load (p < 0.0001). SRS-augmented specimens failed through the cement at the periphery of the threads, whereas PMMA-augmented specimens failed between the cement and the synthetic bone. CONCLUSION: This study suggests that augmentation with PMMA around femoral neck fracture implants will increase the holding power significantly when compared with standard insertion technique as well as augmentation with calcium phosphate cement. Augmentation with calcium phosphate cement like SRS will increase the holding characteristics mainly in low density bone, whereas in high density bone it might even reduce the maximum torque because of the need for predrilling when using the cement for augmentation.

Biomechanical Phenomena↗
PubMed1998

Failure of hydroxyapatite cement to set in repair of a cranial defect: case report.

OBJECTIVE AND IMPORTANCE: Hydroxyapatite cement, a new biomaterial that is being marketed as a method for reconstructing cranial defects, offers many advantages. We document, herein, the complete dissolution and failure of this material to set in a surgically dry field, under optimal conditions, an occurrence that has not been previously reported. CLINICAL PRESENTATION: Hydroxyapatite cement was used for reconstruction of a frontal bone defect secondary to a traumatic depressed cranial fracture in a 9-year-old male patient. At the time of suture removal on postoperative Day 6, we observed serous discharge from the wound, a reappearance of the cranial defect, and brain pulsations visible subcutaneously. INTERVENTION: The patient was returned to the operating room, at which time we learned that the hydroxyapatite cement had migrated out of the defect; small concretions of the cement were scattered throughout the subgaleal space. The concretions of cement in the subgaleal space and the small amount of cement remaining in the defect were removed, and titanium mesh was used. An excellent cosmetic result was achieved. CONCLUSION: Although offering many advantages, hydroxyapatite cement does carry a risk of failure to set, despite optimal technique. Causes for failure to set, as well as possible modifications in the use of material and technique, are discussed.

Bone Cements↗
PubMed2001

The biomechanics of vertebroplasty. The effect of cement volume on mechanical behavior.

STUDY DESIGN: Ex vivo biomechanical study using osteoporotic cadaveric vertebral bodies. OBJECTIVE: To determine the association between the volume of cement injected during percutaneous vertebroplasty and the restoration of strength and stiffness in osteoporotic vertebral bodies, two investigational cements were studied: Orthocomp (Orthovita, Malvern, PA) and Simplex 20 (Simplex P with 20% by weight barium sulfate content; Stryker-Howmedica-Osteonics, Rutherford, NJ). SUMMARY OF BACKGROUND DATA: Previous biomechanical studies have shown that injections of 8-10 mL of cement during vertebroplasty restore or increase vertebral body strength and stiffness; however, the dose-response association between cement volume and restoration of strength and stiffness is unknown. METHODS: Compression fractures were experimentally created in 144 vertebral bodies (T6-L5) obtained from 12 osteoporotic spines harvested from female cadavers. After initial strength and stiffness were determined, the vertebral bodies were stabilized using bipedicular injections of cement totaling 2, 4, 6, or 8 mL and recompressed, after which post-treatment strength and stiffness were measured. Strength and stiffness were considered restored when post-treatment values were not significantly different from initial values. RESULTS: Strength was restored for all regions when 2 mL of either cement was injected. To restore stiffness with Orthocomp, the thoracic and thoracolumbar regions required 4 mL, but the lumbar region required 6 mL. To restore stiffness with Simplex 20, the thoracic and lumbar regions required 4 mL, but the thoracolumbar region required 8 mL. CONCLUSION: These data provide guidance on the cement volumes needed to restore biomechanical integrity to compressed osteoporotic vertebral bodies.

Aged↗
PubMed2004

Biomechanical comparison of kyphoplasty with different bone cements.

STUDY DESIGN: Ex vivo biomechanical study. OBJECTIVES: To compare the biomechanical properties of isolated, fractured, osteoporotic vertebral bodies after treatment by kyphoplasty with one of two cements: alpha-tri-calcium phosphate cement (Biopex-R; Mitsubishi Materials Corp., Tokyo, Japan) or polymethylmethacrylate (Simplex P; Stryker-Howmedica-Osteonics, Mahwah, NJ). SUMMARY OF BACKGROUND DATA: Kyphoplasty and vertebroplasty typically use polymethylmethacrylate cements for the treatment of osteoporotic compression fractures. Scant information exists regarding the use of alternative cements in kyphoplasty. METHODS: Simulated compression fractures were created in 24 vertebral bodies (T6-T9, L2-L5) harvested from three female cadavers. Vertebral bodies were assigned to one of two groups: kyphoplasty with Biopex-R or kyphoplasty with Simplex P. The kyphoplasty treatment consisted of inserting bone tamps bipedicularly into each vertebral body, inflating the tamp, and filling the created void with Biopex-R or Simplex P. Pretreatment and post-treatment heights were measured, and the repaired vertebral bodies were recompressed to determine posttreatment strength and stiffness values. Differences were checked for significance (P < 0.05) using a repeated-measures analysis of variance followed by Tukey's test. RESULTS: Kyphoplasty with Biopex-R restored strength in the lumbar and thoracic vertebral bodies. Kyphoplasty with Simplex P displayed significantly greater posttreatment strength than initial strength in the thoracic region. Vertebral bodies augmented with either cement were significantly less stiff than their initial conditions, except for the thoracic vertebrae treated with Simplex P, in which stiffness was restored. There was no significant difference in percentage of height restored between the cement treatments. CONCLUSIONS: Kyphoplasty with either cement restored initial strength. In general, stiffness was not restored.

Aged↗
PubMed2003

Can finite element models detect clinically inferior cemented hip implants?

Rigorous preclinical testing of cemented hip prostheses against the damage accumulation failure scenario will reduce the incidence of aseptic loosening. For that purpose, a finite element simulation is proposed that predicts damage accumulation in the cement mantle and prosthetic migration. If the simulation is to become a convincing preclinical test, it should be able to distinguish between implants in a clinically relevant way, based on accurate predictions of long-term failure mechanisms of cemented hip prostheses. The algorithm was used to simulate long-term fatigue experiments on femoral reconstructions with Mueller Curved and Lubinus SPII stems. Clinically, the Mueller Curved system performs inferior to the Lubinus SPII system. The finite element simulation predicted much more cement damage around the Mueller Curved stem and showed that the entire cement mantle was involved in the failure process, which was not the case around the Lubinus SPII stem. In addition, the Mueller Curved stem was predicted to migrate more than the Lubinus SPII. The predictions showed excellent agreement with the experimental findings: similar damage locations in the cement, more damage for the Mueller Curved, similar prosthetic migration directions, and more migration for the Mueller Curved stem. This is the first time that a finite element simulation is able to differentiate between a clinically superior and an inferior implant, based on accurate simulation of the long-term failure mechanisms in a cemented reconstruction. Its use for preclinical testing purposes is corroborated.

Cementation↗
PubMed2006

Addition of fluoride to acrylic bone cement does not improve fixation of a total hip arthroplasty stem.

UNLABELLED: Improved fixation to bone is vital for improving the long term success of cemented implants. Addition of fluoride to acrylic bone cement may be one way to improve the quality of the bone cement interface and thereby reduce the risk of loosening. Ninety patients (97 hips) with a median age of 70 years (range, 31-81 years) scheduled for total hip arthroplasty were randomized to receive a stem fixed with fluoride-containing acrylic bone cement or conventional acrylic bone cement. Fixation and bone remodeling around the femoral component was studied with radiostereometry and dual-energy xray absorptiometry up to 5 years after the operation in 73 patients (77 hips). Radiostereometric evaluation at 5 years revealed no differences in stem migration (subsidence/lift-off) or rotations. The stem subsidence inside the mantle was similar in the two groups. At 5 years the study group had lost more bone mineral in Gruen regions 5 and 7 than the controls. The Harris hip and pain score did not differ. Use of fluoride containing bone cement did not improve the stem fixation compared with a conventional cement used up to 5 years, but resulted in more pronounced loss of bone mineral density in the medial cortex. LEVEL OF EVIDENCE: Therapeutic Level I. See Guidelines for Authors for a complete description of levels of evidence.

Adult↗
PubMed2005

Biomechanical stability of intramedullary nailed high proximal third tibial fractures with cement augmented proximal screws.

OBJECTIVE: Intramedullary nailing of nonarticular proximal tibia fractures can be affected by bone density resulting in loss of stability, fixation, and malalignment in osteopenic bone. This study was designed to quantify the biomechanical effects of augmenting proximal screws with cement in intramedullary nailing of high proximal third tibial fractures. DESIGN: In vitro biomechanical study using anatomic specimens. METHODS: Reamed nails were inserted into seven pairs of fresh-frozen cadaveric proximal tibiae and secured using two oblique and two transverse proximal screws. Paired tibiae were randomly assigned into two groups: cemented and noncemented proximal screw-holes. Bone cement was injected into the screw-holes before screw insertion in the cemented tibiae. Specimens were then tested in flexion/extension and varus/valgus to 12 Nm and in torsion to 7 Nm. Physical measurements of bone density were obtained to determine the effect of density on stability. MAIN OUTCOME MEASURES: Stability of the construct in both groups was analyzed and compared statistically using paired t tests. RESULTS: Cement augmentation of the proximal screws significantly increased mechanical stability in torsion and varus/valgus load configurations, with average decreases in rotational motion of 5.4 degrees +/- 1.6 degrees and 5.1 degrees +/- 5 degrees respectively. No change in stability was observed in flexion/extension loading. A trend toward decreased stability was seen in the uncemented construct in varus/valgus; cement augmentation of the proximal screws eliminated this effect. CONCLUSIONS: Lower bone density decreased the stability of the uncemented construct; however, cement augmentation of the proximal screws showed a trend to eliminate this effect in the varus/valgus loading configuration and should be considered when nailing proximal third tibial fractures in osteoporotic patients.

Aged↗
PubMed2006

Cement augmentation techniques in traumatic thoracolumbar spine fractures.

STUDY DESIGN: Review of human cadaveric and in vivo animal studies and clinical trial. OBJECTIVE: To develop less invasive surgical techniques for reconstruction of the anterior column in thoracolumbar fractures. SUMMARY OF BACKGROUND DATA: Persistent central endplate depression can cause anterior column insufficiency after posterior surgery for traumatic thoracolumbar fractures. Reduction of the central endplate followed by intravertebral cement augmentation could restore weight-bearing capacity. MATERIALS AND METHODS: In human cadaveric burst fracture models, balloon-assisted endplate reduction (BAER) and vertebroplasty techniques have been investigated in terms of their safety and biomechanical properties. The histologic properties of different cement polymers were studied in an animal vertebral body and endplate defect model. In addition, the clinical outcome of percutaneous cement augmentation in the setting of a burst fracture examining the BAER technique and vertebroplasty with adjunctive posterior pedicle screw fixation is reviewed. RESULTS: These techniques have proven to be safe and effective, although cement leakage outside the confines of the vertebral body may occur. Calcium phosphate cements are preferable over methylmethacrylate because of their in vivo histologic properties. Using the BAER technique and posterior pedicular fixation, anterior vertebral height restoration is possible. Following balloon removal, some loss of fracture height restoration is observed. Further loss of vertebral height reduction was not observed following cement curing clinically. CONCLUSIONS: These studies show that less invasive anterior vertebral reconstruction using percutaneous cement augmentation techniques is feasible following traumatic vertebral fractures.

Animals↗
PubMed2006

Optimization of tumor volume reduction and cement augmentation in percutaneous vertebroplasty for prophylactic treatment of spinal metastases.

OBJECTIVE: Spinal metastatic disease occurs in up to one-third of all cancer patients. Metastasis can lead to vertebral burst fracture and consequent neurologic compromise. Percutaneous vertebroplasty (PV) is a minimally invasive procedure aimed at restoring vertebral stability by augmentation of weakened vertebrae with bone cement. PV is associated with a complication rate of 10% in treating vertebral metastases. Tumor ablation before cement injection has been suggested to improve PV outcome in the metastatic spine. The objectives of this study were to quantify the effects of volumetric tumor reduction and cement augmentation in the metastatic spine and to develop a protocol for recommended cement volume to achieve sufficient restoration of intact (nonpathologic) vertebral body stability. METHODS: A biphasic parametric finite element model of an L1 spinal motion segment was developed and validated against previously collected experimental data. Using this model, 12 scenarios were simulated to represent tumor volume reductions of up to 60% and cement augmentation from 1 to 8 mL. CONCLUSIONS: Restoration of intact vertebral stability is possible in metastatic vertebrae after 30% tumor ablation and 1 to 2 mL bone cement augmentation. A protocol was developed on the basis of the findings of this study suggesting recommended cement volume for injection as a function of remaining tumor volume after ablation. These findings may motivate refined methods of prophylactic treatment of metastatic vertebrae.

Bone Cements↗
PubMed2004

Endogenous cannabinoids are candidates for lipid mediators of bone cement implantation syndrome.

Acute hypotension, hypoxemia, cardiac arrhythmias, cardiac arrest, (or a combination of these), and sudden death are well-recognized complications of the cemented hip arthroplasty procedure. Collectively, these are known as the bone cement implantation syndrome (BCIS). The endogenous cannabinoids, anandamide (ANA) and 2-arachidonylglycerol (2-AG), are reported to be strong vasodilators and play a role in the hypotension associated with hemorrhagic and septic shock. In the present study, a potential role for the endogenous cannabinoids in influencing hemodynamic variables in BCIS was investigated. Thirty-five patients (35 hips) entered a prospective, randomized clinical trial. The patients were divided into two groups. Group 1 comprised 16 patients who had the component inserted using a conventional cementing technique, whereas group 2 consisted of 19 patients who had the femoral component inserted without cement. Blood samples were taken at six consecutive time points: before anesthesia, after reaming the femur, 2 min after insertion of stems with or without cement into the femur, and 10 min, 20, and 30 min after stem insertion. In group 1 (with cement), the mean levels of ANA and 2-AG significantly increased after stem insertion. In a comparison of each group after stem insertion, mean ANA and 2-AG levels in group 1 also significantly differed from those in group 2. By contrast, in group 2 (without cement) neither ANA nor 2-AG levels exhibited a significant increase or change at any point in time. In conclusion, we have shown for the first time that endogenous cannabinoids are candidates for lipid mediators of BCIS.

Aged↗
PubMed2007

Finite element-based preclinical testing of cemented total hip implants.

We developed a finite element model to preclinically test cemented hip implants for damage accumulation, including cement crack formation, creep, and stem migration. Using this model, we simulated the mechanical failure processes of four cemented total hip arthroplasty implants (Lubinus SPII, Mueller Curved, Exeter and Charnley, all with known clinical results) during cyclic normal walking and stair-climbing loads. These four implants were selected to ascertain whether the simulation predicted greater damage development around clinically inferior stems, whether clinically inferior designs could be identified by an initial stress analysis without the prediction of cement damage, and whether the simulation could predict high implant subsidence rates in combination with minimal cement damage. Based on the predicted cement crack patterns and crack formation rates, the simulation correctly identified the clinically inferior implant designs. Based only on the initial stress analysis under a stair-climbing load, it was not possible to identify clinically inferior designs. High subsidence values and minimal cement damage were predicted for the Exeter implant, similar to clinical findings. Our findings suggest the simulation may be effective in differentiating between a range of implants and design features.

Bone Cements↗