Intermittent versus continuous sciatic block combined with femoral block for patients undergoing knee arthroplasty. A randomized controlled trial.

PURPOSE: Many institutions perform peripheral femoral and/or sciatic nerve blocks for analgesia after total knee arthroplasty. The aim of the present investigation was to compare the analgesic effect of an intermittent sciatic block (boluses on demand only) with a continuous infusion. METHODS: One hundred and forty patients receiving a femoral and a sciatic nerve block (SNB) by catheter were assessed. The femoral catheter was infused continuously in both groups. In the continuous group (n = 70), the sciatic catheter was used continuously as well. In the intermittent group (n = 70), after a single injection of 20 ml ropivacaine 0.75 %, injections into the sciatic catheter were performed on demand only. Frequency of injections, ventral and dorsal numerical pain scores (NRSs) of the knee, functional outcome (degree of flexion/extension) and additional opioid requirements were assessed during the post-operative period. RESULTS: In both groups, dorsal and ventral NRSs were below 3 at rest and below 5 during mobilisation over the complete period of assessment. Differences between the groups could not be observed. The cumulative number of supplemental injections into the sciatic catheter was higher in the intermittent group (52) compared with the continuous group (24; p < 0.05). Groups did not differ from each other with regard to functional outcome and opioid consumption. CONCLUSIONS: The use of a sciatic block performed as intermittent bolus injection on demand only did not affect post-operative outcome parameters with regard to pain scores, functional outcome or opioid requirements. This approach might therefore be considered as an alternative to a continuous infusion concept. ClinicalTrials.gov Identifier: NCT01843153.

The density of nociceptive SP- and CGRP-immunopositive nerve fibers in the dura mater lumbalis of rats is enhanced after laminectomy, even after application of autologous fat grafts.

A considerable number of patients complain about pain after lumbar surgery. The spinal dura mater has been debated as a possible source of this pain. However, there is no information if laminectomy influences the nociceptive sensory innervation of the dura. Therefore, we quantitatively evaluated the density of SP- and CGRP-immunopositive nerve fibers in the dura mater lumbalis in an animal model of laminectomy. Twelve adult Lewis rats underwent laminectomy, in six of them the exposed dura was covered by an autologous fat graft. Further six animals without surgical treatment served as controls. Six weeks after surgery, the animals were perfused and the lumbar dura was processed immunohistochemically for the detection of CGRP- and SP-containing nerve fibers. In controls, the peptidergic nerve fibers were found predominantly in the ventral but rarely in the dorsal dura mater lumbalis. After laminectomy, the density of SP- and CGRP-immunopositive neurons significantly increased in ventral as well as in dorsal parts of the dura. Axonal spines could be observed in some cases at the site of laminectomy. The application of autologous fat grafts failed to inhibit the significant increase in the density of peptidergic afferents. Thus, we have provided the first evidence that laminectomies induce an increase in the density of putative nociceptive SP- and CGRP-immunopositive neurons in the lumbar dura mater ascribable to an axonal sprouting of fine nerve fibers. This effect was not prevented by using autologous fat grafts. It is conceivable that the neuronal outgrowth of nociceptive afferents is a cause of low back pain observed after lumbar surgery.

Digital templating in total hip arthroplasty with the Mayo stem.

PATIENTS: In 40 patients undergoing total hip arthroplasty with the Mayo femoral stem we studied how preoperative digital templating corresponded to the actual intraoperative choice of implant size, position, offset and restoration of leg length. RESULTS: The preoperatively planned sizes of the components showed a high rate of coincidence with the sizes used intraoperatively [Intraclass Correlation Coefficient (ICC) 0.661-0.810]. However, the agreements in offset and CCD correction were poor (ICC 0.476, 0.253). This could be statistically attributed to the change in the distance from the medial margin of the stem to the medial margin of the medial femoral cortex and the height of osteotomy. The agreement in leg length correction was moderate (ICC 0.583), which was attributed to the change in the hip rotation center and the height of osteotomy. CONCLUSION: Careful preoperative planning was useful for accurate size choice of the Mayo prosthesis. Factors such as the height of osteotomy and the distance from the medial margin of the stem to the medial margin of the medial femoral cortex in relation to the position of the Mayo stem should be taken into account in order to restore ideal offset and leg length.

Polyethylene particle-induced bone resorption in alpha-calcitonin gene-related peptide-deficient mice.

UNLABELLED: This study investigates the impact of alpha-CGRP on bone metabolism after implantation of polyethylene particles. alpha-CGRP knockout mice showed less osteolysis compared with wildtype mice. The local neurogenic microenvironment might be a crucial factor in particle-induced osteolysis. INTRODUCTION: Periprosthetic osteolysis is the major reason for aseptic loosening in joint arthroplasty. This study aimed to investigate the potential impact of alpha-calcitonin gene-related peptide (alpha-CGRP) deficiency on bone metabolism under conditions of polyethylene particle-induced osteolysis. MATERIALS AND METHODS: We used the murine calvarial osteolysis model based on polyethylene particles in 14 C57BL 6 mice and 14 alpha-CGRP-deficient mice divided into four groups of 7 mice each. Groups 1 (C57BL/J 6) and 3 (alpha-CGRP knockout) received sham surgery, and groups 2 (C57BL/J 6) and 4 (alpha-CGRP knockout) were treated with polyethylene particles. Qualitative and quantitative 3D analyses were performed using microCT. In addition, bone resorption was measured within the midline suture by histological examination. The number of osteoclasts was determined by counting the TRACP(+) cells. Calvarial bone was tested for RANKL expression by RT-PCR and immunocytochemistry. RESULTS: Bone resorption was significantly reduced in alpha-CGRP-deficient mice compared with their corresponding wildtype C57BL 6 mice as confirmed by histomorphometric data (p < 0.001) and microCT (p < 0.01). Osteoclast numbers were significantly reduced in group 3 and the particle subgroup compared with group 1 (p < 0.001). We observed a >3-fold increase of basal RANKL mRNA levels within group 1 compared with group 3. Additional low RANKL immunochemistry staining was noted in groups 3 and 4. CONCLUSIONS: In conclusion, alpha-CGRP knockout mice did not show the expected extended osteolysis compared with wildtype mice expressing alpha-CGRP. One of the most reasonable explanations for the observed decrease in osteolysis could be linked to the osteoprotegerin (OPG)/RANK/RANKL system in alpha-CGRP-deficient animals. As a consequence, the fine tuning of osteoclasts mediating resorption in alpha-CGRP-null mice may be deregulated.

Lack of toxicological side-effects in silver-coated megaprostheses in humans.

Deep infection of megaprostheses remains a serious complication in orthopedic tumor surgery. Furthermore, reinfection gets a raising problem in revision surgery of patients suffering from infections associated with primary endoprosthetic replacement of the knee and hip joint. These patients will need many revision surgeries and in some cases even an amputation is inevitable. Silver-coated medical devices proved their effectiveness on reducing infections, but toxic side-effects concerning some silver applications have been described as well. Our study reports about a silver-coated megaprosthesis for the first time and can exclude side-effects of silver-coated orthopedic implants in humans. The silver-levels in the blood did not exceed 56.4 parts per billion (ppb) and can be considered as non-toxic. Additionally we could exclude significant changes in liver and kidney functions measured by laboratory values. Histopathologic examination of the periprosthetic environment in two patients showed no signs of foreign body granulomas or chronic inflammation, despite distant effective silver concentrations up to 1626 ppb directly related to the prosthetic surface. In conclusion the silver-coated megaprosthesis allowed a release of silver without showing any local or systemic side-effects.

Localization of SP- and CGRP-immunopositive nerve fibers in the hip joint of patients with painful osteoarthritis and of patients with painless failed total hip arthroplasties.

Using immunohistochemical methods we determined the presence of SP- and CGRP-immunopositive nerve fibers in the hip joint of patients with femoral neck fracture (controls, group 1), painful osteoarthritis (group 2), and painless failed total hip arthroplasties (group 3). Immunoreactive nerve fibers were found in the soft tissue of the fossa acetabuli as well as in the subintimal part of the synovial layer in the hip joint capsule of groups 1 and 2. In the capsule of controls the innervation density had a median of 5.7fibers/cm(2) for CGRP-ir and 3.2fibers/cm(2) for SP-ir afferents. In the osteoarthritic group, the density significantly increased to a median of 15.6fibers/cm(2) for CGRP-ir and 8.2fibers/cm(2) for SP-ir neurons (p=0.05). Patients with failed hip arthroplasties completely lacked these neuropeptide containing afferents. Innervation density in the fossa acetabuli of osteoarthritc patients showed a median of 14.1fibers/cm(2) for CGRP-ir and 5.9fibers/cm(2) for SP-ir afferents. From these data we assume that the hip joint capsule and the soft tissue of the fossa acetabuli are important triggers of nociception. This is supported by the fact, that patients with loosened total hip arthroplasties, where we failed to detect SP- and CGRP-immunoreactive fibers, did not feel pain. The upregulation of SP- and CGRP-positive neurons in response to arthritic stages suggests a mechanism involving neuropeptides in the maintenance of a painful degenerative joint disease and in mediating noxious stimuli from the periphery. Furthermore, these findings help to explain clinical observations, such as effectiveness of local therapy to control hip pain with intraarticular injection, synovectomy and denervation procedures.

Over-expression of p53/BAK in aseptic loosening after total hip replacement.

Particle-induced osteolysis is a major cause of aseptic loosening after total joint replacement. The possible induction of apoptosis has not been addressed in great detail. Thus far, it has been shown that ceramic and polyethylene particles can induce apoptosis of macrophages in vitro. The purpose of this study was to test the hypothesis that wears debris generated from total hip arthroplasty could induce cellular damage and apoptosis in vivo. We therefore determined by immunohistochemical methods if increased expression of p53, an important transcription factor, and BAK and Bcl-2, two important regulators of apoptosis, can be found in interface membranes and capsules of hips with aseptically loose implants. Strongly positive immunohistochemical staining for p53 and BAK was found in peri-implant tissues from patients with aseptic hip implant loosening. Differentiation of various cell types showed that macrophages stained positive for p53 in all capsule and interface specimens. p53 was frequently detected in giant cells. Positive staining of BAK in macrophages and giant cells was seen in all specimens. Some positive reactions were observed in fibroblasts, only two of 19 cases stained for p53 and three cases for BAK within synovial cells. Positive macrophages and giant cells were localized around polyethylene particles. While T-lymphocytes showed a regular BAK-staining, the other leukocytes were negative. Statistical analyses showed significant positive correlations (p < 0.001) between the presence of polyethylene and metal debris and the expression of BAK and p53. Polyethylene particles were surrounded by more positive macrophages and giant cells than were metal particles, indicating that polyethylene debris may be a stronger inductor of cell cycle arrest and apoptosis than metal debris. In this study apoptosis of macrophages, giant cells and T-lymphocytes in capsules and interface membranes of patients with aseptic hip implant loosening has been demonstrated in vivo. It is possible that the apoptotic cascade could evolve as a novel therapeutic target to prevent particle-induced osteolysis.

Titanium serum levels may remain elevated despite hip revision surgery for wear-through of an acetabular component.

A 62-year-old female patient showed radiographic signs of severe linear wear of the acetabular component six years after cementless total hip arthroplasty. This suggested wear-through of the acetabular liner with secondary wear of the titanium shell. At revision surgery wear-through of both the inlay and the acetabular shell were confirmed. Despite meticulous debridement serum titanium levels remained elevated for more than 12 months. Wear-through of a polyethylene acetabular liner with secondary wear of the titanium shell can lead to increased titanium serum levels. Titanium serum levels can remain highly elevated despite revision surgery.

[Pressfit of equatorially roughened cementless acetabular components--a finite element analysis]. / Der acetabuläre Pressfit bei aquatorialer Beschichtung der zementfreien Hüftpfanne--eine finite-Elemente-Analyse.

AIM: Does the pressfit anchorage of cementless acetabular cups depend on the roughness of the pole? To answer this question the primary pressfit of two cementless acetabular cups which differ only with regard to the roughness of their poles were compared by means of finite elements analysis. MATERIALS AND METHODS: It was assumed that the material properties of bone are homogeneous, isotropic and linearly elastic. Material-specific values of cancellous bone with three different bone densities were used. Assumption of isotropy represents an approximation. RESULTS: Comparison of the two prosthesis designs revealed that both designs/shapes cause similar patterns of bone deformation and tension. CONCLUSIONS: It can therefore be concluded that with regard to pressfit anchorage the prosthesis with milled polar surface is according to FEA mechanically equivalent to the prosthesis with non-milled polar surface.

Promotion of bone formation by simvastatin in polyethylene particle-induced osteolysis.

The effects of statins on bone formation in periprosthetic osteolysis have not been determined to date. We investigated the effect of the HMG-CoA reductase inhibitor simvastatin on osteoblastic bone formation under conditions of ultra-high molecular weight polyethylene (UHMWPE) particle-induced osteolysis. The murine calvarial osteolysis model was utilized in 21 C57BL/J6 mice randomized to three groups. Group I underwent sham surgery only, group II received UHMWPE particles, and group III, particles and simvastatin treatment. After 2 weeks, calvaria were processed for histomorphometry and stained with Giemsa dye. New bone formation was measured as osteoid tissue area within the midline suture. Bone thickness was quantified as indicator of net bone growth. Statistical analysis was performed using one-way ANOVA and a Student's t-test. New bone formation and bone thickness were significantly enhanced following simvastatin treatment. New bone formation was 0.008+/-0.008 mm2 in sham controls (group I), 0.015+/-0.012 mm2 after particle implantation without further intervention (group II), compared to 0.083+/-0.021 mm2 with particle implantation and simvastatin treatment (group III) (p=0.003). The bone thickness was 0.213+/-0.007 mm in group I, 0.183+/-0.005 mm in group II, and 0.238+/-0.009 mm in group III (p=0.00008). In conclusion, simvastatin treatment markedly promoted bone formation and net bone growth in UHMWPE particle-induced osteolysis in a murine calvarial model. These new findings indicate that simvastatin may have favorable osteoanabolic effects on wear debris-mediated osteolysis after total joint arthroplasty, involving local stimulation of osteoblastic bone formation.

The effect of simvastatin on polyethylene particle-induced osteolysis.

This study aimed to investigate the effects of the HMG-CoA reductase inhibitor simvastatin on ultra-high molecular weight polyethylene (UHMWPE) particle-induced osteolysis. The murine calvarial osteolysis model was used in 21 C57BL/J6 mice randomized to three groups. Group I underwent sham surgery only, group II received UHMWPE particles, and group III, particles and simvastatin treatment. After two weeks, calvaria were processed for histomorphometry. Bone resorption was measured as resorption within the midline suture using Giemsa staining. Osteoclast numbers were determined per high-power field using TRAP-staining. Statistical analysis was performed using one-way ANOVA and Student's t-test. Bone resorption in midline suture was 0.094+/-0.007 mm(2) in sham controls (group I), 0.25+/-0.025 mm(2) after particle implantation without further intervention (group II), and 0.131+/-0.02 mm(2) with particle implantation and additional simvastatin treatment (group III) (p=0.00003). Osteoclast numbers were 15.3+/-3.6 in group I, 48.7+/-7.1 in group II and 6.2+/-3.1 in group III (p=0.00002). In conclusion, simvastatin treatment markedly decreased UHMWPE particle-induced osteolysis in a murine calvarial model. This finding suggests that simvastatin may have a role for noninvasive prevention and treatment of wear debris-mediated periprosthetic osteolysis after total joint arthroplasty.

Stimulation of bone formation by zoledronic acid in particle-induced osteolysis.

We investigated the effect of a single subcutaneous dose of zoledronic acid on particle-induced osteolysis and observed excessive regional new bone formation. We utilized the murine calvarial osteolysis model and polyethylene particles in C57BL/J6 mice. Twenty-eight mice were used, seven per group. Specimens were stained with Giemsa dye. The osteoid tissue area was determined. Bone thickness was measured as an indicator of bone growth. Net bone growth was significantly increased in animals with zoledronic acid treatment: 0.02 mm(2)+/-0.03 mm(2) in animals with particle implantation only (group 2), 0.25 mm(2)+/-0.08 mm(2) with particle implantation and zoledronic acid treatment directly after surgery (group 3; p=0.0018), and 0.21 mm(2)+/-0.11 mm(2) with particle implantation and zoledronic acid treatment on the fourth postoperative day (group 4; p=0.0042). The mean bone thickness was 0.2 mm+/-0.04 mm (range 0.17 mm-0.31 mm) in group 1 (sham controls) and 0.16 mm+/-0.02 mm (range 0.14 mm-0.19 mm) in group 2, 0.31 mm+/-0.04 mm (range 0.28 mm-0.39 mm) in group 3, and 0.29 mm+/-0.02 mm (range 0.28 mm-0.34 mm) in group 4. Student's t-test revealed a statistically significant difference between groups 2 and 3 (p=0.00042), and groups 2 and 4 (p=0.0019). In conclusion, our observational study suggests that zoledronic acid may stimulate bone apposition locally in the process of particle-induced osteolysis.

Suppression of polyethylene particle-induced osteolysis by exogenous osteoprotegerin.

Alterations of the key regulators of osteoclastogenesis, receptor activator of NF-kappaB (RANK), RANK ligand (RANKL), and osteoprotegerin (OPG) have been implicated in wear particle-induced osteolysis, the most common cause for implant failure in total joint replacements. This study investigated the effect of exogenous OPG on ultra-high-molecular-weight polyethylene (UHMWPE) particle-induced osteolysis. The murine calvarial osteolysis model was utilized in 28 C57BL/6J mice randomized to four groups. Group I underwent sham surgery only, group II received UHMWPE particles, and group III and IV particles and subcutaneous OPG starting from day 0 (group III) or day 5 (group IV) until sacrifice. After 2 weeks, calvaria were prepared for histology and histomorphometry. Bone resorption was measured within the midline suture using Giemsa staining and osteoclast numbers were determined using TRAP staining. UHMWPE particle implantation resulted in grossly pronounced osteoclastogenesis and bone resorption. Both immediate and delayed treatment with OPG counteracted these particle-induced effects significantly, suppressing osteoclast formation and bone resorption (p < 0.001 and p < 0.001, respectively). In conclusion, exogenous OPG markedly suppressed UHMWPE particle-induced osteolysis in a murine calvarial model. This important finding underscores the crucial significance of the OPG-RANKL-RANK signaling in wear particle-induced osteolysis. Exogenous OPG may prove an effective treatment modality for wear debris-mediated periprosthetic osteolysis after total joint arthroplasty.

Comparison of subtraction arthrography, radionuclide arthrography and conventional plain radiography to assess loosening of total knee arthroplasty.

The value of plain radiographs, digital subtraction arthrography and radionuclide arthrography was analysed in 23 cases of failed total knee arthroplasty. The preoperative diagnosis was compared with the intraoperative assessment. Sensitivity, specificity and the positive and negative predictive value for assessing a loose component were determined separately for the femoral and tibial components. At revision we found 13 loose femoral and 12 loose tibial implants. In eight cases both components were unstable. Plain radiography had a sensitivity of 77% for loosening of the femoral and 83% for the tibial component; digital subtraction arthrography 77% for the femoral and 8% for the tibial component and radionuclide arthrography 31% and 8%. The specificity for plain radiography was 90% for the femoral and 72% for the tibial implant. For subtraction arthrography it was 50% and 82% and for subtraction arthrography 70% and 82%. Radiography had the highest positive and negative predictive values for both components compared with the other two techniques. As a diagnostic tool to detect implant loosening, plain radiography is the most effective in this study. Subtraction arthrography and radionuclide arthrography are not suitable for use as routine methods for detection of total knee arthroplasty loosening.

Medium-term results of the AMC-unicompartmental knee arthroplasty.

This study presents the outcome of patients treated by AMC-unicompartmental knee arthroplasty (UCA). The prosthesis was implanted in 361 cases for the medial or lateral compartment arthritis. The mean follow-up period was 5.5 (range: 2.3-12.5) years. Mean age at surgery was 69.5 (range: 46.3-88.6) years. Six knees were lost to follow-up (1.6%). Patients were assessed by an independent clinical observer and results were standardised using the Knee Society Rating System. The roentgenographic analyses were performed according to the Knee Society Evaluation System. Ninety-five percent of patients had no pain or slight pain at the latest follow-up, 92% had a good or excellent clinical outcome. Three knees were revised for mobile bearing dislocation after medial UCA and three for lateral mobile bearing dislocation after lateral UCA. Five revisions were necessitated by component loosening and there was one case of deep infection. The clinical results of the investigated patients demonstrate that the AMC-UCA is a successful concept with safe fixation of the prosthesis and good durability of the mobile bearings.

[Effects of clinically relevant alumina ceramic, zirconia ceramic and titanium particles of different sizes and concentrations on TNF-alpha release in a human macrophage cell line]. / Auswirkungen von klinisch relevanten Aluminium Keramik-, Zirkonium Keramik- und Titanpartikel unterschiedlicher Grösse und Konzentration auf die TNFalpha-Ausschüttung in einem humanen Makrophagensystem.

INTRODUCTION: Aseptic loosening is considered to be the main problem of modern endoprothesis. Tumor necrosis factor alpha (TNFalpha) seems to be the initiator protein of particle disease. The aim of our study was to investigate the TNFalpha response of macrophage like cells (MLC) after stimulation with periprosthetic particles, typically found during revision surgery. For this purpose alumina ceramic (Al2O3), zirconia ceramic (ZrO2) and titanium (Ti) particles of different sizes and concentrations were used. Important was to study the effects of different sizes due to TNFalpha secretion and the comparison of the biological effects of alumina ceramic and titanium. METHOD: To obtain an TNFalpha profile we used an established macrophage model (Rader et al.) with THP-1 cells (human monocytic cell line). Therefore 106 MLC were incubated with different particle concentrations and sizes for 6 h. The supernatant was then investigated for TNF using ELISA assay. RESULTS: Ti-particles provoked in both sizes (0.2 microm and 2.5 microm) the greatest TNFalpha response, 8 times and 17 times as high in comparison with control. But substantially more 0.2 microm sized Ti-particles were necessary to get the above mentioned results. Al2O3-particles were not as effective as Ti, but they released fourfold more TNFalpha compared to control. There was no difference in TNFalpha-secretion comparing Al2O3-particles of different sizes (0.6 microm and 2 microm), but a 1000 times greater concentration of the 0.6 microm sized particles were needed. Using Al2O3- and Ti-particles of the same size and concentration, Ti provoked a significant higher TNFalpha response. ZrO2 showed no effects on TNFalpha release. CONCLUSION: Because of our results we recommend ceramic articulating surfaces, which are superior to metal on metal matings ion term of biological reactions. Additionally bigger wear particles should be avoided. Revisionoperation should be done early to avoid huge amount of wear particles and to minimize local osteolysis.

The diagnostic value of digital subtraction arthrography and radionuclide arthrography in revision total hip arthroplasty.

An analysis of plain radiographs, digital subtraction arthrography, and radionuclide arthrography was performed in 25 revision hip arthroplasties to evaluate the efficacy and usefulness of these methods in the diagnosis of loosening. The findings by each method were compared with intraoperative assessment of the status of components and expressed in terms of sensitivity, specificity, and predictive accuracy. Overall accuracy for the acetabular component by plain radiographs was 80%; by digital subtraction arthrography, 88%; by radionuclide arthrography, 68%. Overall accuracy for the femoral component by plain radiographs was 92%; by digital subtraction arthrography, 84%; radionuclide arthrography, 76%. We consider subtraction arthrography and radionuclide arthrography to be adjuvant diagnostic tools which may be indicated in individual cases of suspected implant loosening of total hip arthroplasty. The routine use of these two methods is not warranted when compared to plain radiographs.

Jumbo cups for revision of acetabular defects after total hip arthroplasty: a retrospective review of a case series.

The treatment of acetabular bone defects presents a great challenge in revision total hip arthroplasty (THA). The purpose of this study was to evaluate the clinical and radiological outcome of revision THA using jumbo cups for acetabular reconstruction after applying the bone-grafting technique. We studied 17 patients with acetabular defects ranging from Type 2A to Type 3A according to Paprosky's classification. According to the AAOS-score twelve patients were classified as Type II and five patients as Type III. Uncemented press-fit cups with an outer diameter larger than 64 mm were used in all cases. Fifteen patients received morselized bone allografts. In eight patients an additional screw fixation was necessary. The mean follow-up period was 82 months (range 33-149). The mean Harris Hip Score was preoperatively 62 and at the time of the last follow-up examination 83 points (p = 0.007). Two acetabular components failed, one due to aseptic loosening and another one due to septic loosening. There was a trend of displacement of the femoral head centre towards the infero-lateral position after using jumbo cups that approached statistical significance (p = 0.065). Closure of acetabular defects of Types 2A to 3A according to Paprosky's classification and type II to III according to the AAOS-score respectively can be satisfactorily accomplished using jumbo cups after applying the bone-grafting technique.

Particle-induced osteolysis in three-dimensional micro-computed tomography.

Small-animal models are useful for the in vivo study of particle-induced osteolysis, the most frequent cause of aseptic loosening after total joint replacement. Microstructural changes associated with particle-induced osteolysis have been extensively explored using two-dimensional (2D) techniques. However, relatively little is known regarding the 3D dynamic microstructure of particle-induced osteolysis. Therefore, we tested micro-computed tomography (micro-CT) as a novel tool for 3D analysis of wear debris-mediated osteolysis in a small-animal model of particle-induced osteolysis. The murine calvarial model based on polyethylene particles was utilized in 14 C57BL/J6 mice randomly divided into two groups. Group 1 received sham surgery, and group 2 was treated with polyethylene particles. We performed 3D micro-CT analysis and histological assessment. Various bone morphometric parameters were assessed. Regression was used to examine the relation between the results achieved by the two methods. Micro-CT analysis provides a fully automated means to quantify bone destruction in a mouse model of particle-induced osteolysis. This method revealed that the osteolytic lesions in calvaria in the experimental group were affected irregularly compared to the rather even distribution of osteolysis in the control group. This is an observation which would have been missed if histomorphometric analysis only had been performed, leading to false assessment of the actual situation. These irregularities seen by micro-CT analysis provide new insight into individual bone changes which might otherwise be overlooked by histological analysis and can be used as baseline information on which future studies can be designed.