Correlation between radiographic parameters and functional scores in degenerative lumbar and thoracolumbar scoliosis.

INTRODUCTION: Adult scoliosis is a condition in which the spinal deformity occurs because of degeneration. Although various studies have agreed on the importance of restoring the sagittal balance, few have evaluated the relationship between functional scores and radiological parameters. The primary objective of this retrospective study was to demonstrate the correlation between radiographic parameters and functional outcomes in adult patients with lumbar or thoracolumbar degenerative scoliosis. The secondary objective was to assess the long-term effects of posterolateral fusion for treating this deformity. STUDY OUTLINE: This single-centre retrospective study included 47 patients over 50years of age who had degenerative lumbar scoliosis treated with an instrumented posterolateral fusion; the mean follow-up was 6.4years (range 2 to 20). METHODS: Radiographic analysis of A/P and lateral full spine standing radiographs was carried out with the KEOPS software. Three pelvic parameters (pelvic tilt, pelvic incidence, sacral slope), two spinal parameters (lumbar lordosis and thoracic kyphosis) and three sagittal balance parameters (C7 sagittal tilt, C7 Barrey's ratio and spinosacral angle) were calculated. The functional outcomes were evaluated through three self-assessment questionnaires: Oswestry Disability Index, SRS-30 and SF-36. The correlation between clinical and radiographic parameters was calculated with Spearman's correlation test. RESULTS: There was a significant correlation between the SF-36 (PCS) and the following three sagittal parameters: sacral slope (r=-0.31453; P=0.04), lumbar lordosis (r=-0.30198; P=0.0491) and spinosacral angle (r=-0.311967; P=0.0366). The mean ODI score was 33.61, which corresponds to minimal to moderate disability. The mean physical (PCS) and mental (MCS) component summary scores of the SF-36 were 37.70 and 38.40, respectively. The mean SRS-30 score was 3.07. CONCLUSION: It is essential that the sagittal balance be restored when treating degenerative lumbar scoliosis to generate better functional outcomes and better quality of life. To achieve this correction, instrumented posterolateral fusion appears to be a very reliable technique that leads to lasting improvement. LEVEL OF EVIDENCE: IV.

Inhibition of osteolysis and increase of bone formation after local administration of siRNA-targeting RANK in a polyethylene particle-induced osteolysis model.

Receptor activator of nuclear factor kappa-B (RANK) and RANK-ligand are relevant targets for the treatment of polyethylene particle-induced osteolysis. This study assessed the local administration of siRNA, targeting both human RANK and mouse Rank transcripts in a mouse model. Four groups of mice were implanted with polyethylene (PE) particles in the calvaria and treated locally with 2.5, 5 and 10 µg of RANK siRNA or a control siRNA delivered by the cationic liposome DMAPAP/DOPE. The tissues were harvested at day 9 after surgery and evaluated by micro-computed tomography, tartrate-resistant acid phosphatase (TRAP) immunohistochemistry for macrophages and osteoblasts, and gene relative expression of inflammatory and osteolytic markers. 10 µg of RANK siRNA exerted a protective effect against PE particle-induced osteolysis, decreasing the bone loss and the osteoclastogenesis, demonstrated by the significant increase in the bone volume (P<0.001) and by the reduction in both the number of TRAP(+) cells and osteoclast activity (P<0.01). A bone anabolic effect demonstrated by the formation of new trabecular bone was confirmed by the increased immunopositive staining for osteoblast-specific proteins. In addition, 5 and 10 µg of RANK siRNA downregulated the expression of pro-inflammatory cytokines (P<0.01) without depletion of macrophages. Our findings show that RANK siRNA delivered locally by a synthetic vector may be an effective approach for reducing osteolysis and may even stimulate bone formation in aseptic loosening of prosthetic implants.

Does thoracoscopic anterior release of rigid idiopathic scolioses associated with correction by posterior instrumentation result in better long-term frontal and sagittal balance?

INTRODUCTION: The aim of treatment of scolioses is to reduce deformities and restore balance in the spine. HYPOTHESES: In rigid forms of scoliosis, associating anterior release could provide greater frontal and/or sagittal plane correction and improve balance in the spine. PATIENTS AND METHODS: This study compared correction and long-term balance on two planes between two homogeneous groups of idiopathic rigid scolioses treated with and without thoracoscopic release. The study included rigid scolioses with less than 35% reducibility and a Cobb angle of more than 60°, who all underwent posterior correction using a rod rotation technique. There were 29 patients, 14 who underwent a one-step procedure (group A) and 15 a two-step procedure (group B), with the subgroups of kyphoscolioses and lordoscolioses determined in each group. Frontal balance, Cobb angle, thoracic kyphosis and the Jackson plumbline were measured on pre- and postoperative X-rays and at the final follow-up. RESULTS: The mean long-term final follow-up was 144 months for group A and 54 months for group B. Frontal plane correction was identical in groups A and B. Frontal balance was preserved in all cases at the final follow-up. Sagittal balance was not modified with or without anterior release. The thoracoscopic release step resulted in an additional correction of 15.5° (23%) of thoracic hyperkyphosis in patients with kyphoscoliosis (P=0.003). DISCUSSION: Thoracoscopy did not improve short term results in the Cobb angle or frontal or saggital balance. Nevertheless, enhanced correction of thoracic hyperkyphosis was obtained with this procedure. In this study, the association of thoracoscopic anterior release with posterior correction by rod rotation to treat rigid scolioses did not appear to improve results, except for the correction of thoracic hyperkyphosis.

Open wedge high tibial osteotomies: Calcium-phosphate ceramic spacer versus autologous bonegraft.

INTRODUCTION: Valgus tibial osteotomy (VTO) is a well-known procedure for the treatment of medial compartment femoro-tibial osteoarthritis. Good and very good results have been reported with calcium phosphate wedges, which avoid the inconveniences of autologous grafts use. The hypothesis of this study is that with equivalent results in the treatment of osteoarthritis of the knee, the use of calcium phosphate wedges (BMCaPh) to fill the bone defect created by osteotomy would result in fewer specific complications and less pain associated with autologous grafts (AUTO) harvesting. PATIENTS AND METHODS: This prospective, controlled, randomised study included one arm that received a macroporous, biphasic calcium phosphate wedge (BMCaPh group) and one arm that received an autologous tricortical graft (AUTO group) for filling. The same plate with locked screws was used for fixation in all cases. All patients underwent at least two years of clinical and radiographic post-operative follow-up. RESULTS: Forty patients were included. Loss of correction occurred in six of the twenty-two patients in the BMCaPh group (27%), resulting in three early surgical revisions, compared to one loss of correction in the AUTO group. Lateral cortical hinge tears were a risk factor for loss of correction for the entire cohort and in the BMCaPh group. (relative risk 13.3 [1.9-92]. Moreover, union took significantly longer and pain lasted significantly longer in the BMCaPh group, although results were comparable at 6 months. DISCUSSION: A significant number of undesirable events (loss of correction) occurred in this study, limiting the number of included patients. Nevertheless, the results show that although there was no difference in the two groups for overall complications, number of revisions all causes combined, or clinical results, filling with BMCaPh was less tolerated and increased the risk of loss of correction when local mechanical conditions of the knee were unfavourable (lateral cortical hinge tears). Moreover, although it is not possible to draw a conclusion because of methodology bias in this study, early weight-bearing resumption on the knee also seemed to favour these complications. LEVEL OF EVIDENCE: Level II. Prospective randomized study.

Spondylodiscitis due to Propionibacterium acnes: report of twenty-nine cases and a review of the literature.

Propionibacterium acnes is the most frequent anaerobic pathogen found in spondylodiscitis. A documented case required microbiological proof of P. acnes with clinical and radiological confirmation of inflammation in a localized region of the spine. Microbiological samplings were obtained by surgery or aspiration under radiological control. Twelve males and 17 females (median age, 42 years) with spondylodiscitis due to P. acnes were diagnosed within the last 15 years. Three patients were immunosuppressed. All patients reported back pain as the main symptom, and most were afebrile. Three patients had a peripheral neurological deficit, one a motor deficit, and two a sensory deficit attributable to the infection; and six patients had an epidural abscess. The most frequent risk factor was surgery, which was present in the history 28 of 29 (97%) patients. The mean delay between spinal surgery and onset of disease was 34 months, with a wide range of 0-156 months. Osteosynthesis material was present in twenty-two cases (76%). In 24 (83%) patients, additional surgery, such as débridement or spondylodesis, was performed. Previous osteosynthesis material was removed in 17 of the 22 (77%) patients where it was present. Total cure was reported in all patients, except one, after a mean duration of antibiotic therapy of 10.5 weeks (range, 2-28 weeks). In conclusion, spondylodiscitis due to P. acnes is an acute infection closely related to previous surgery. The most prominent clinical feature is pain, whereas fever is rare, and the prognosis is very good.

Sciatic nerve compression related to ossification of the sacrospinous ligament secondary to pelvic balance abnomalities.

The authors report an isolated case of right sacrospinous ligament ossification causing sciatic pain because of compression of the proximal sciatic nerve. The initial conservative treatment of injections in the conflict zone and the intervertebral joints was insufficient. Surgical exploration was undertaken via a posterior approach, demonstrating the conflict between the nerve and the ossified ligament. Resection of the ossified ligament eliminated the symptoms at the cost of transitory buttock hypesthesia. The anatomic and pathologic exam identified simple osseous metaplasia. Lumbar-pelvic coxometry analysis showed sagittalization of the acetabular roofs, excessive bilateral femoral torsion, and a step-off attenuation at the anterior cervicocephalic junction (low anterior cervico-cephalic femoral offset). In addition, reduced lumbar lordosis and accentuated sacral slope were noted, factors that could be related to modifications in the static balance of the lumbar-pelvic complex. This imbalance could be correlated to an increase in the forces applied to the pelvic ligament layers. The etiological hypothesis retained was that this osseous metaplasia was a reaction to excessive stresses on the sacrospinous ligament.

Friction couples in total hip replacement.

The problem of friction couples remains unresolved to this day. Improvements in femoral and acetabulum implant anchorage over the last 20 years have significantly extended total hip replacement (THR) implant lifespan; the formation of wear debris, however, leads to resorption and osteolysis, considerably shortening implant lifespan in active patients. Alumina-alumina friction couples provide an excellent friction coefficient, with wear particles that do not cause any osteolysis. There is, however, a problem of acetabulum anchorage of solid alumina, and the risk of fracture persists with ceramic implants despite improvements in their mechanical properties. Metal-metal couples also display very good tribological behavior, but at the cost of the formation of Co and Cr ions impacting surrounding bone tissue and accumulating in remote organs. The behavior of such "hard-hard" couples greatly depends on implant component positioning and on the consequences of repeated neck-insert contact. Very highly crosslinked polyethylene (PE) shows very significant improvement in terms of wear at five years' follow-up compared to conventional PE, but the behavior of this new concept will need to be monitored in the clinical situation if the disappointments experienced with previous hylamer-type improved PE are to be avoided. All these friction couples need to be validated by prospective clinical studies conducted over more than five years, to provide orthopedic surgeons with an eclectic choice of friction couples adapted to the patient's activity.

Significance of Propionibacterium acnes-positive samples in spinal instrumentation.

STUDY DESIGN: A retrospective study about Propionibacterium acnes infections after Cotrel-Dubousset (CD) instrumentation. OBJECTIVES: To analyze the significance of P. acnes-positive deep samples after CD. SUMMARY OF BACKGROUND DATA: The diagnosis of spinal infections to P. acnes after CD is difficult. METHODS: Patients with revision surgery and at least 1 P. acnes-positive deep sample, between 2000 and 2006 were included. Group A had 1 revision surgery and group B had 2 successive revision surgeries, with P. acnes-positive deep samples. Group A was divided into 2 subgroups according to the peroperative macroscopic aspect, subgroup A1 with septic tissues, subgroup A2 without septic tissues. The biologic characteristics of the patients and the surgical and medical treatments were assessed. RESULTS: Sixty-eight patients were included, 60 in group A (A1 = 33, A2 = 27) and 8 in group B. Group A: 26 patients had 1 or 2 P. acnes-positive samples and 34 had at least 3 P. acnes-positive samples. Histology showed chronic inflammatory changes. C-reactive protein value median rate was 42 (A1) and 5 mg/L (A2). Twenty-two patients had a complete implant removal (14 with antibiotics, A1 = 12, A2 = 2). Nine patients had a total implant replacement (7 with antibiotics). Twenty-two patients had a partial implant removal (17 with antibiotics, A1 = 5, A2 = 12). Seven A1 patients had an irrigation and debridement (6 with antibiotics). The evolution was favorable for 28 patients. Seven patients had a documented sepsis. Group B: during the first revision, 8 patients had a partial implant removal (2 with antibiotics); during the second revision, all patients received antibiotics 4 of whom had a total implant removal. The long-term evolution was favorable for 6 patients. CONCLUSION: P. acnes infection of spinal instrumentation is difficult to diagnose. Results of at least 4 deep sample cultures, histology, and C-reactive protein values must be compared to the peroperative macroscopic aspect.

[Treatment of deep cartilage defects in the knee with autologous chondrocyte transplantation: a review of 28 cases]. / Greffe de chondrocytes autologues dans le traitement des pertes de substance condylienne du genou: bilan de 28 implantations.

PURPOSE OF THE STUDY: The knee has little capacity for spontaneous regeneration of deep cartilage defects. In 1999, the French Society of Arthroscopy initiated a multicentric clinical trial on autologous chondrocyte transplantation using the technique described by Brittberg and Peterson. The protocol of this prospective study was validated by the ethics committee and all patients provided the informed consent for participation. MATERIAL AND METHODS: Patients underwent surgery in seven hospitals: 28 patients (7 female, 21 male, mean age 28 years, age range 18-45 years). The underlying condition was: osteochondritis (n=14), isolated posttraumatic chondropathy (n=8), chondropathy plus ACL tear (n=6). All patients presented deep condylar cartilage defects (ICRS grades 3 and 4). Mean surface area involved after debridement was 490 mm2 (range 150-1050 mm2). Patients were reviewed two years at least after transplantation for functional assessment and an MRI performed 2 to 3 years after transplantation. Control arthroscopy was also performed in 13 patients with biopsy for histology and immunohistochemistry for 10. RESULTS: Twenty-six patients were reviewed with more than two years follow-up (mean 2 years 9 months). There were no general complications; three patients presented a partial avulsion of the autograft treated arthroscopically and one arthrolysis was performed at six months. Function was improved in all patients but four, but pain persisted in one patient. The mean ICRS score improved from 41 points (19-55 points) to 74 points (54-86 points), for an 80% gain. Follow-up MRI was available for 16 knees: the graft was hypertrophied in 11, at level in 3 and insufficient in 2; marginal integration was good in 10 knees and fair in 6. Items of marginal and subchondral integration had a very high positive predictive value for good clinical outcome. The arthroscopic score was nearly normal (range 8-11) in 8 knees and abnormal (range 4-7) in 5. The Knutsen histological groups according to richness of hyaline cartilage were: group 1 (>60%) (n=1); group 2 (>40%) (n=3), group 3 (<40%) n(=4) and group 4 (bone or fibrous tissue) (n=1). The function scores (r=0.80) and the MRI scores (r=0.76) were correlated with the arthroscopy scores. There was no correlation between the histological findings but the sample size was too small for meaningful analysis. DISCUSSION: The clinical results demonstrate an improvement in more than 80% of knees, findings similar to earlier reports. The arthroscopic and histological results were equivalent to those reported by Knutsen, but less satisfactory than those reported by Bentley or Peterson. Cell injections under a periosteal patch constitute the first generation of autologous chondrocyte grafts. Resorbable matrices loaded with chondrocytes before implantation are under development and have provided promising early results.

[Metal on metal bearing surfaces in total hip arthroplasty: a survey of material incidents]. / Le frottement métal-métal en arthroplastie de hanche: aspect de matériovigilance.

This study is dedicated to the problems met with metal-metal bearing prostheses. We have analysed the results of the reports sent to the AFSSAPS relating incidents described with this interface. Only 11 incidents were reported during the last 4 years by surgeons from different centers in France. At a mean follow-up of 7 years, we collected 2614 total hip arthroplasties with metal-metal bearings and among them only 5 cases of unusual osteolysis and 10 cases of impingement. The bibliographic analysis did not show any severe specific complication due to the release of Cobalt or Chromium ions. The increased levels of Co an Cr in the patients' blood is now a well established notion (with more than 10 years follow up) and no special carcinogenetic effect has been correlated with the metal-metal bearings. Small diameter cemented cups can provide complications with high rates of acetabular loosening and metallosis; the same is true for some cementless cups also with loosening and a high revision rate. Among 143 hip prosthesis with a cemented polyethylene cup, at a mean follow-up of 42 months there were 22% of evolutive radiolucencies around the cups concerning all three De Lee and Charnley zones. Furthermore there was a statistically significant difference between small and large diameter cups (loosening of cups less than 46 mm in diameter). The same problem has been described for some cementless cups with loosening at the metal-bone interface due to a failure of osteointegration at the implant surface. However no failures were observed with an hydroxyapatite coating on the same cup. An other matter of concern is the skirted metal head: this design is responsible for a high rate of impingement and of prosthetic revision (2.3% among 642 THA). In these cases the increase of Cobalt serum levels was well correlated with the failure of the metal-metal interface. Large diameter heads decrease significantly the risks of dislocation. This is correlated with the increase in size. The release of ions in the blood was not affected by the large diameter compared to the regular size. So this overview confirms that if we respect some basic rules for the indications there are no specific complications related to the use of metal-metal bearings. In prospective studies the results of ceramic-ceramic and metal-metal bearings are similar but we must keep on observing prospectively the patients as for the release of Co and Cr.

[Correction of stiff thoracic idiopathic adult scoliosis. Prediction from the traction radiograph]. / Réduction des scolioses idiopathiques raides de l'adulte.

PURPOSE OF THE STUDY: The aim of this study was to determine the predictive value of the traction radiograph in adults with stiff curve (preoperative Cobb angle>60 degrees and reduction of less than 35% with traction) thoracic scoliosis. We wanted to compare this predictive value with that observed in reducible scoliosis. MATERIAL AND METHODS: A traction radiograph was obtained using a standard protocol with dynamometric control of the force applied. Patients with stiff scoliosis had 47 thoracic curves and 11 thoracolumbar curves (with primary anterior release for ten thoracic curves and eight thoracolumbar curves) and patients with reducible scoliosis had 56 thoracic curves. Cortre-Dubousset instrumentation was used for treatment in all patients. RESULTS: The postoperative Cobb angle for the stiff curves (without anterior release) was strongly correlated with the preoperative angle with traction (r=0.91; p<0.0001). The correlation between the postoperative Cobb angle and the preoperative Cobb angle without traction was less pronounced (r=0.86; p<0.0001). The traction radiographs were less predictive of the Cobb angle correction than the postoperative Cobb angle. The difference was 17.5+/-7 degrees , which corresponds to a supplementary gain in reduction after surgery. For the thoracic curves alone, the differences between the traction Cobb angle and the postoperative Cobb angle was 14.5 degrees for stiff curves and 6.5 degrees for reducible curves. Furthermore, the correlation between the Cobb angle with traction and the postoperative Cobb angle was stronger for stiff curve thoracic scoliosis (r=0.90) than reducible thoracic scoliosis (r=0.78). DISCUSSION AND CONCLUSION: The standard traction radiographs were highly predictive of postoperative reduction of stiff thoracic and thoracolumbar curves treated by segmental instrumentation. The postoperative result can thus be estimated with a margin of error of +/-7 degrees . For the stiff curves, the postoperative Cobb angle was 17.5 degrees on average less than predicted on the traction radiograph (on average 20% supplementary gain in reduction). This angle gain, which was greater for stiff than reducible curves, corresponds to the determining effect of release occurring with stiff curves. Finally, because of the stronger correlation between the traction Cobb angle and the postoperative Cobb angle for stiff curves, the predictive value of the traction radiograph is greater for stiff curves than for reducible curves. In conclusion, one of the contributions of the traction radiograph, which results from the predictability of the postoperative angle with a small margin of error, is to enable adequate prediction of the postoperative outcome for a given patient or a specific sub-group of patients, e.g. with or without anterior release.

Phenotypic and functional analysis of lymphocytes infiltrating osteolytic tumors: use as a possible therapeutic approach of osteosarcoma.

BACKGROUND: Osteosarcoma is the most common type of primary bone tumor. The use of aggressive chemotherapy has drastically improved the prognosis of the patients with non-metastatic osteosarcomas, however the prognosis of the patients with metastasis is still very poor. Then, new and more effective treatments for curing osteosarcoma, such as immunotherapy are needed. Tumor-infiltrating lymphocytes (TIL) have been involved in the control of tumor development and already assessed with success for the treatment of several cancers including melanoma. While TIL represent a fascinating therapeutic approach in numerous malignant pathologies, there is few report concerning adult bone-associated tumors including osteosarcoma. METHODS: Human TIL were isolated and characterized (phenotype, lytic activity) from twenty-seven patients with bone-associated tumors (osteosarcoma, Ewing's sarcoma, giant cell tumor, chondrosarcoma, plasmocytoma and bone metastases). Similar experiments were performed using rat osteosarcoma model. RESULTS: While TIL with a main CD4+ profile were easily isolated from most of the tumor samples, only TIL extracted from osteosarcoma were cytotoxic against allogeneic tumor cells. In all cases, TIL lytic activity was significantly higher compared to autologous peripheral blood leukocytes. Similar data were observed in rat osteosarcoma model where TIL were characterized by a main CD4+ profile and high lytic activity against allogeneic and autologous tumor cells. Moreover, rat TIL expansion was not accompanied by refractoriness to further activation stimulus mainly by tumor antigens. CONCLUSION: These results demonstrated that TIL therapy could be a very efficient strategy for the treatment of adult osteosarcoma.

Metatarsal giant cell tumors and giant cell reparative granuloma are similar entities.

Light and electron microscopic investigations and studies of the resorption ability in vitro of giant cells were done in two patients with giant cell osteolytic lesions of metatarsal bone. Giant cells harvested from both patients were similar in morphologic features and ability to resorb dentin. After other diagnoses of osteolytic lesions of metatarsal bone were ruled out, one lesion was considered a giant cell reparative granuloma and the other a true giant cell tumor of bone. Clinical, radiologic, ultrastructural, functional studies, and data in the literature, indicated that giant cell reparative granuloma only can be differentiated from giant cell tumor by younger age at diagnosis and the occurrence of giant cell clusters. All other features (cortical erosion, high rate of recurrence, hemorrhage areas, predominant intercellular collagenous substance) are characteristic of both lesions. If these two giant cell lesions are different entities, more accurate means are needed to distinguish them.

Efficacy of pentasaccharide on a prethrombosis model based on a calibrated stasis by the increase in up-stream venous pressure.

On a previous model using Wessler's principle in the rat, we have demonstrated that a partial ligature of the inferior vena cava leading to a 40% increase in up-stream venous pressure was thrombogenic only in association with the infusion of low dose of thromboplastin (90 microg/kg). In these thrombogenic conditions, the infusion of pentasaccharide (Arixtra, fondaparinux) should lead to a strong inhibition of thrombus formation. Therefore, we performed on five groups of 10 rats: stasis alone (group S) with a 40% increase in up-stream venous pressure; stasis and thromboplastin (group ST90); and stasis, thromboplastin and pentasaccharide (groups SPT50, SPT100 and SPT250) at three different dosages (50, 100 and 250 microg/kg). The efficacy of pentasaccharide was measured according to the variations in up-stream venous pressure, thrombus weight and thrombin-antithrombin complexes levels. Only 250 microl/kg pentasaccharide significantly reduced the thrombus weight in comparison with group ST90 (5 mg versus 23.8 mg, P = 0.01) but it was not sufficient to induce a return to the basic state (5 mg versus 0.2 mg in group S, P = 0.049). Thrombin-antithrombin complex levels measured at the end of the experiment were significantly reduced in comparison with group ST90 (16.7 versus 57.8 mg, P = 0.01) and were not statistically different from group S (16.1 versus 16.6 mg, P = 0.65). In conclusion, in a very borderline model toward thrombogenesis, pentasaccharide was able to reduce thrombus weight and abolished biological hypercoagulability.

Bilayered calcium phosphate coating to promote osseointegration of a femoral stem prosthesis.

A bilayered bioactive-gradient coating, consisting of a superficial layer of biphasic calcium phosphate (BCP) and a deep layer of hydroxyapatite (HA), promotes faster osseointegration and higher shear strength in non-loading conditions than do monolayer BCP or HA coatings. This study evaluated the biofunctionality of this coating in weight-bearing conditions at 6 and 12 months. The coating was plasma-sprayed on the metaphyseal portion of a sandblasted Ti6Al4V canine femoral prosthesis implanted using the surgical press-fit technique. An identical uncoated stem served as the control. Metaphyseal bone-to-implant apposition was increased for coated ( approximately 90% and 80% respectively at 6 and 12 months) as compared to uncoated implant ( approximately 7% at 6 and 12 months). Limited bone apposition was observed at the diaphyseal level. After 12 months, the uncoated implant interface consisted of well-organized, active fibrous tissue, whereas only inactive fibrous tissue interposition was observed at diaphyseal levels of the coated implant. At 6 months, the mineralization apposition rate (MAR) was similar, regardless of implant or bone structures. At 12 months, a significant decrease of MAR was observed around the uncoated implant. Transmission electron microscopy studies of the interface showed precipitation of biological apatite crystals in close association with mineralized collagenous bone matrix. Our results suggest a direct relationship between bioactivity and enhanced bone formation. The sandwich coating used is effective in promoting massive metaphyseal osseointegration, which ensures mechanical stability for early weight-bearing and should prevent long-term complications.

Influence of metal ion solutions on rabbit osteoclast activities in vitro.

The purpose of the present study was to compare the effects of various metal ions (aluminium, chromium, cobalt, gold, iron, strontium, titanium and vanadium) on rabbit osteoclast activities, with respect to their number, size, resorptive capacity and their capacity to release proteinases. Marked heterogeneous osteoclastic behaviour was observed early in culture with metal ions (24 h) in term of resorption parameters. In contrast, protease activities (cysteine-proteinase and metalloproteinase activities) were not modulated in our culture conditions. Aluminium, iron, gold and titanium reduced the number of osteoclasts significantly. Aluminium and gold had no effect on osteoclast-mediated resorption on dentin-slices, although aluminium induced a greater number of very small lacunae. Titanium reduced only the mean surface area per lacunae, cobalt reduced the mean surface area of lacunae and increased their number, and iron reduced both parameters. Strontium had no effect on osteoclast formation and on total dentin slice surface resorbed. However, strontium increased the number of small lacunae formed on dentin-slices by osteoclasts. Chromium had no effect on osteoclast activities. These findings indicate that metal ions induce very early effects on osteoclasts, which can contribute to periprosthetic pathologies via different cellular mechanisms.

Bone remodelling and tumour grade modifications induced by interactions between bone and swarm rat chondrosarcoma.

Chondrosarcoma is currently defined as a malignant cartilage tumour arising de novo or within a pre-existing benign cartilage tumour. Chondrosarcoma can be surgically resected, but all grades have significant rates of local recurrence. The purpose of the present study was to develop an animal intraosseous chondrosarcoma model simulating the progression of human chondrosarcoma and elucidating its behaviour and biology. An intraosseous Swarm rat model was designed to assess interactions between bone and chondrosarcoma. A comparison of tumour grading was carried out according to transplantation site. The effects of chondrosarcoma cells (SRC cells) on the mineralisation capacities of osteoblasts and on osteoclast differentiation were studied in relation to modifications observed in vivo at the cellular level. Transplantation of Swarm rat chondrosarcoma within bone marrow or contiguous to induced periosteal lesions led to extensive bone remodelling with trabecular bone rarefaction and periosteal apposition. Transplantation in close contact to bone but without any periosteal lesion had no effect on bone, suggesting that bone healing factors interact with tumour development. With the intramedullary model, the development of tumours of different grade confirms that bone environment is an important factor in malignancy. A decrease of bone nodule formation was noted after cocultures of SRC cells with rat bone marrow, but there was no modification of osteoclast differentiation after cultures of total rabbit bone cells with SRC cells. These data reveal the importance of interactions between bone environment and tumour in inducing bone remodelling and variations in tumour malignancy.

Influence of bone environment on ceramic osteointegration in spinal fusion: comparison of bone-poor and bone-rich sites.

Quantitative experimental data showed differences in bone quality and ceramic incorporation between bone-rich and bone-poor implantation sites. Bone in-growth was significantly lower for ceramic implanted at a lumbar intertransverse than a laminar site. Bone-marrow enrichment of the lumbar intertransverse site (regarded as bone-poor) greatly facilitated ceramic osteointegration. The vertebral interbody site, despite theoretical richness in osteogenic precursor cells, might be bone-poor at the time of grafting as compared to the reference iliac crest site. These data have important clinical implications concerning the potential benefit of enriching both bone-poor and bone-rich sites.