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Three cemented femoral components from total hip arthroplasties retrieved at autopsy were examined in regard to the migration of birefringent polyethylene particles across the fixation interfaces. They were obtained from two patients who died from unrelated causes. They had been in place, respectively, for 8 and 9 years (first patient) and for 9 years (second patient). Osteolysis was present in the acetabular side only. The femoral components were not loosened. Histologic sections were performed at four levels of the femoral components, and polyethylene particles were counted with the use of a semiautomatic image analyzer. Sections below the tip of the stem were treated by deorganification and the lysate was centrifuged in the attempt to isolate wear debris. Particles were found at both interfaces (bone-cement and metal-cement) and in the cancellous bone between the trabeculae. They were also present in the Haversian canals of the cortical bone. Particles of various sizes were found in the medullary canal beneath the tip of the stem. In scanning electron microscopy, they appeared to have irregular shapes. Wear debris can migrate across the cement-bone interface of nonloosened implants. They appear to progress through the porosity of the cancellous bone., (Copyright 2004 Wiley Periodicals, Inc.)

Implants, consisting of smooth Inox cylinders, were cemented into the lower femur and upper tibia of nine sheep to study the distal migration of polyethylene particles. Some implants had a titanium-bead porous coat at the proximal end. These were of three types: In the first type, the porous coat was covered with hydroxyapatite to obtain a bony seal; the second type was prepared for a polymethylmethacrylate seal; in the third type, the porous zone was surrounded by a 2-mm-thick space to allow the formation of a fibrous seal. Small polyethylene particles were injected into the knees once a week during the third and fourth months after implantation. The animals were euthanized 2 months later. Major longitudinal sections of the implants and the surrounding bone were examined under a polarized light microscope. Birefringent particles were counted at the cement-bone and cement-implant interfaces. Osteolysis was not observed. None of the seals significantly decreased the migration of particles around the cemented part of the implants. Particles were observed in cement fissures and vacuoles. They migrated at both interfaces and in the bone itself. They were visible in marrow spaces between bone trabeculae., (Copyright 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 68B: 140-148, 2004)

Purpose of the Study: In order to limit the consequences of prior total patellectomy on knee function after total knee arthroplasty, we propose an original technique using an en bloc patellar graft to reconstruct the quadriceps lever arm. The purpose of this work was to describe the technique and present preliminary results obtained in seven patients., Patients and Methods: Seven en bloc patellar grafts were performed in seven patients (6 women and 1 man) during total knee arthroplasty procedures for femorotibial degenerative joint disease after prior patellectectomy (mean 13 years before arthroplasty, range 5-20 years). We implanted three posterior stabilized prostheses, one ultracongruent prosthesis, two prostheses preserving the posterior cruciate ligament, and one bi-cruciate prosthesis. The patella was reconstructed with an autologous bone graft fashioned from the tibial plateau in six cases, and with a homologous graft fashioned from a bone-bank femoral head in one. Transosseous sutures were used to fix the graft to the extensor system. A polyethylene button was cemented on five of the grafts., Results: Active extension was defective in five knees prior to the patellar graft and in only one knee after patellar reconstruction. The IKS knee score improved from 41 points (range 35-45) before surgery to 78 points (range 55-95) after grafting and the IKS function score from 35 (range 5-50) to 72 (range 40-100). Four of the seven grafts were removed (eight weeks to five years after implantation, mean two years) mainly due to failure of fixation leading to progressive migration. Follow-up varied from eight weeks to six years. Mean follow-up for the three grafts still in place was 4.6 years (4-6 years). After removing the patellar graft (4 knees) the IKS knee score decreased to 68 points (20-95) and the IKS function score to 62 points (30-100). Lack of active extension reappeared in three of the knees after removing the patellar graft but was not observed in the three knees with the patellar graft in place (and flexion was at least 110 degrees ). Microradiography of the patellar graft explanted after two years revealed peripheral corticalization with areas of living bone tissue seen on the pathology specimens. Inversely, the autografts explanted at eight weeks and at five years exhibited bone necrosis., Conclusion: This preliminary study shows that patellar autograft can improve the performance of total knee arthroplasty on patellectomized knees. The fixation technique must be improved using transosseous transverse sutures in addition to peripheral sutures in order to limit secondary migration of the graft. A patellar autograft fixed into the extensor system can remain viable two years after implantation. This technique can be proposed when total knee arthroplasty is indicated for a patellectomized knee, particularly in patients with lack of active extension.

Injectable calcium phosphate hydraulic cements are known to have a high clinical potential in bone reconstruction for mini-invasive orthopaedic surgery, interventional radiology, and rheumatology. Previous in vivo experiments in rabbit have shown that the presence of beta-TCP granules in injectable bone cement help maintain the transient biomechanical function of the implanted bone and promote the formation of good-quality new bone. Histomorphometric analysis of two brushite hydraulic cement (BHC) mixtures selected from previous results (referred to in this work as BHC-A and BHC-B) was performed at three postoperative delays (0, 12, and 24 weeks): histomorphometric analysis of bone colonization within beta-TCP shows that, just before implantation, the beta-TCP granule area is significantly higher in BHC-B; the residual granule area decreases steadily over time in BHC-A, whereas it goes through a maximum of 30% at 12 weeks in BHC-B; the residual granule porosity increases steadily up to 35% in BHC-A, whereas it goes through a maximum of 35% at 12 weeks and decreases somewhat until 24 weeks in BHC-B. New bone formation within granules appears higher in BHC-A (58% Area) compared to BHC-B (38% area) at 12 weeks. At 24 weeks bone colonization levels off in both cements at about 50% area. Irrespective of the cement matrix composition, beta-TCP granules contribute actively to the conduction of new bone formation., (Copyright 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 413-417, 2002)

Tissue engineering, a cross between the science of the living organism and that of engineering, aims to replace, maintain or improve human tissue functions, by means of tissue substitutes containing living elements. Thus, it is about production of artificial tissue, using (alone or in combination) cells, matrix or bioactive factors. Their association gives rise to a hybrid biomaterial combining biological components (cells, growth factors or adhesion proteins) and materials (polymers, ceramics). The applications are wide-ranging, from the skin, to the liver, or to the cornea as well as to the locomotor system. Bone tissue engineering has advanced the most in this field, partly because of the progress made by research into bone substitutes, although cartilage and tendons are also concerned. This technology requires cell culture (committed cells or more often bone marrow stem cells), biomaterials (porous materials with controlled architecture and cements), growth factors (such as 'Bone Morphogenetic Proteins'), the proteins implicated in cell adhesion (such as fibronectin or the aminoacid sequences specifically recognised by integrin subunits) or gene therapy (notably using transfected stem cells). Tissue engineering and regenerative stimulation of tissue are now booming on experimental and industrial levels and clinical applications are increasingly numerous. Considering the potential of these technologies, they should continue to develop widely.

Restenosis remains the major limitation of coronary angioplasty. The objective of this study was to develop microspheres able to be delivered at the angioplasty site for long-term drug release and to test their effects in a model of balloon angioplasty. Polylactic-co-glycolide acid microspheres (5-10 microm in diameter) were prepared by using an oil-in-water emulsion-solvent evaporation method. In vitro experiments with hydrocortisone-loaded microspheres revealed a hydrocortisone release for 4 weeks. We studied the in vivo effect of injection of microspheres into the arterial wall of New Zealand White rabbits by using a perforated balloon. Deep penetration of microspheres in the arterial wall was documented immediately after angioplasty. Intimal hyperplasia was assessed in iliac arteries 4 weeks after angioplasty. The morphometric analysis was performed in four groups of animals; the first group was subjected only to conventional angioplasty (control, n = 10), whereas the other three groups after conventional angioplasty were received perforated balloon angioplasty with saline (n = 10), microspheres (n = 10), or hydrocortisone-loaded microspheres (n = 7). Intramural injection of saline did not induce greater intimal hyperplasia compared with control (0.17 +/- 0.03 vs. 0.18 +/- 0.03 mm2, respectively). Microspheres injection was associated with a trend toward a greater degree of intimal hyperplasia that did not reach statistical significance. Hydrocortisone-loaded microspheres were associated with a significant reduction in intimal hyperplasia compared with unloaded microspheres (0.16 +/- 0.02 vs. 0.26 +/- 0.03 mm2, respectively). The polylactic-co-glycolide acid microspheres are well tolerated, easily injected into the arterial wall, and the increase of intimal hyperplasia is easily inhibited by release of hydrocortisone for 4 weeks after initial injury.

Biomechanical properties of a biodegradable calcium phosphate hydraulic cement (CPHC) were tested with rabbits. The cement was composed of beta-tricalcium phosphate (beta-TCP), monocalcium phosphate monohydrate (MCPM), and calcium sulfate hemihydrate (CSH), beta-TCP-MCPM-CSH cement. Cylinders of 4.7 mm in diameter and 10 mm in length were put into bone cavities created in the distal epiphysis of femurs in rabbits. Cylinders of the same size of porous biphasic calcium phosphate ceramics (BCPC, 75% hydroxyapatite and 25% beta-TCP) were implanted as references. Two, 4, 12, and 16 weeks after the operation, the rabbits were sacrificed. Histomorphometry showed that the cement was resorbed, leaving only 7.67 +/- 1.81% of bone cavity after 12 weeks. Newly formed bone occupied 34.59 +/- 4.00% of the cavity. Cylindrical bone-material composites were cut out with a small dental burr. Compressive force was applied to the specimens and compressive strength, elastic modulus, and toughness were calculated. The same tests were performed on cylinders of normal bone from the same site, which served as controls. The compressive strength and the toughness of the cement-bone composite were higher than those of normal bone and porous ceramics 12 weeks after the operation (p < 0.05). At 16 weeks the compressive strength and the toughness returned to the normal bone values. The elastic modulus of the porous ceramic-bone composite was higher than the normal bone at 4, 12, and 16 weeks after surgery (p < 0.05). We found that the beta-TCP-MCPM-CSH cement is replaced by new bone and that the cement-new bone composite has similar or better mechanical properties than normal bone within 16 weeks. This study suggests the usefulness of a particular cement for filling bone defects or for temporary fixation of orthopedic implants.

New percutaneous filling techniques are beginning to be used in bone tumor pathology. The purpose of this study was to develop a reproducible model for testing new injectable bone substitutes. A closed cancellous bone defect was created in the distal femoral condyles of rabbit. Bone defect was filled by a percutaneous injection. Several situations were tested: spontaneous evolution of unfilled cavities, evolution of cavities filled either with a conventional orthopedic cement (PMMA), either with a mixed collagen-hydroxyapatite material, either with a biomaterial derived from the vegetal protein zein, either with a calcium phosphate cement brushite type. The new bone formation was quantified in the defect for each group in which several delays were tested. A bone defect of reproducible size was obtained consistently. A partial bone formation was observed in the unfilled group. The best bone formation rate was obtained in the phosphate cement group. This model showed the interest of injectable biomaterials and more precisely the interest of the phosphate calcium cements as brushite.

We observed, after 38 months of follow-up, the rupture of the metallic shell of a Harris-Galante cup implanted in a dysplastic acetabulum augmented with a femoral head autograft. Bone ingrowth was extended to 53% of the porous surface, but only in the areas in contact with the true acetabulum. No bone ingrowth was identified in the fiber mesh in contact with the autograft. The graft was necrotic on histologic examination and showed collapse radiographically. These last conditions were responsible for shear stress in the part of the cup that was in contact with the graft-acetabulum junction. These stresses were involved in the fatigue rupture mechanism identified on microscopic examination of rupture surfaces. We observed metallic structure anomalies in the failed cup by comparing with another Harris-Galante cup considered as a reference: larger alpha elements, reduction of the titanium equiaxial structure. These defects could be related to uncontrolled temperature during the sintering process utilized for fiber mesh fixation. These structural anomalies, by reducing the metallic fatigue strength, potentiated the deleterious effect of partial bone ingrowth and graft collapse.

On T1 and T2 weighted MR Imaging, normal Achilles tendon is generally described as a homogeneous low signal structure. However, punctuate and/or short linear high signal foci are often seen, especially on the anterior part of axial sections. These images are not artifacts. The aim of this study was to correlate MR images of 20 normal Achilles tendons with micro-anatomic and histologic studies of 2 cadaver tendons. Intratendinous vessels were found in connective tissue septa called mesotenon. Foci of high signals result from this mesotenon. On T1 weighted images, a normal Achilles tendon can present high signal images without any disease process.

Hard cylinders (4.7 x 10 mm) of two kinds of beta-tricalcium phosphate-monocalcium phosphate monohydrate-calcium sulfate hemihydrate (beta-TCP-MCPM-CSH) cements with and without beta-TCP granules (500-1000 microns) were implanted into holes drilled in rabbit femoral condyles for up to 16 weeks. Empty cavities were used as control. Cement resorption and new bone formation in the cylinders were evaluated with contact microradiography and quantified through an automatic image analysis system. At 4 weeks, both kinds of cement cylinders were surrounded by new bone. At 8 weeks, except for beta-TCP granules, both cement cylinders were almost completely resorbed and replaced by bone tissue. At 16 weeks the bone in the cavities of both cements recovered a trabecular pattern, but only the bone trabeculae in the initial cavity of the cement with beta-TCP granules became thick and mature. However, the cavities of the empty control were still empty and large. These results show that the beta-TCP-MCPM-CSH cements stimulate bone formation and are rapidly replaced by bone tissue. When added with nonresorbable beta-TCP granules, this cement maintains bone formation for a longer time.