Joan C. Monllau

Simvastatin and atorvastatin enhance gene expression of collagen type 1 and osteocalcin in primary human osteoblasts and MG‐63 cultures

To clarify the mechanism of the stimulatory effect of statins on bone formation, we have assessed the effect of simvastatin and atorvastatin on osteoblast activity by analysing cell proliferation, as well as collagen, osteocalcin, and bone morphogenetic protein‐2 (BMP2) gene expression in primary human osteoblast (hOB) and MG‐63 cell line cultures. Explants of bone from patients without any metabolic disease under orthopedic hip procedures were used to obtain hOB. Cell cultures were established, synchronized, and different concentrations of simvastatin or atorvastatin were added (10−9 M, 10−8 M, 10−7 M, 10−6 M) during the experiment. Cell proliferation was analyzed after 24 h. Collagen polypeptide α1 type 1 (COL1A1) gene expression, osteocalcin, and BMP2 expression levels were quantified by real‐time PCR after 24 h incubation with statins. There was a statistically significant decrease in cell proliferation related to simvastatin or atorvastatin addition at all concentrations in primary hOB compared with those not treated. A significant increase in COL1A1, osteocalcin, and BMP2 gene expression was detected when hOB cultures were treated with simvastatin or atorvastatin at different concentrations. Similar but less significant effects were found on MG‐63 cells. After statin treatment we observed both an arrest of proliferation in hOB cells and an increase in collagen, osteocalcin, and BMP2 gene expression, consistent with a stimulatory effect towards mature osteoblast differentiation. These findings support the bone‐forming effect of statins, probably through the BMP2 pathway. J. Cell. Biochem. 101: 1430–1438, 2007.

Factors affecting meniscal extrusion: correlation with MRI, clinical, and arthroscopic findings.

The existence of meniscal extrusion is well known in the natural history of the osteoarthritic knee. However, extruded menisci are also seen in non-pathologic knees. To ascertain the prevalence of meniscal extrusion in non-arthritic patients, the MRIs of 100 knees were prospectively studied. The data were correlated both with clinical and operative arthroscopic findings. The results showed 68.5% of the medial menisci to have some degree of extrusion, averaging at 28% of the meniscal size. While the lateral meniscus were extruded in 18.8% of cases at an average of 15% of the meniscal size. Furthermore, a relationship between the anterior insertion variant of the anterior medial meniscus and meniscal extrusion was found (P=0.001) in this series. The results suggest meniscal extrusion to be much more common in non-arthritic knees than previously estimated. The results also suggest that when the anterior horn of the medial meniscus inserts anteriorly in the tibial plateau, the meniscus tends to be extruded. It must be kept in mind that one of the limitations of this work is that the MRIs are taken in a non-weightbearing position.

In Vivo Evaluation of 3-Dimensional Polycaprolactone Scaffolds for Cartilage Repair in Rabbits

Background Cartilage tissue engineering using synthetic scaffolds allows maintaining mechanical integrity and withstanding stress loads in the body, as well as providing a temporary substrate to which transplanted cells can adhere. Purpose This study evaluates the use of polycaprolactone (PCL) scaffolds for the regeneration of articular cartilage in a rabbit model. Study Design Controlled laboratory study. Methods Five conditions were tested to attempt cartilage repair. To compare spontaneous healing (from subchondral plate bleeding) and healing due to tissue engineering, the experiment considered the use of osteochondral defects (to allow blood flow into the defect site) alone or filled with bare PCL scaffold and the use of PCL-chondrocytes constructs in chondral defects. For the latter condition, 1 series of PCL scaffolds was seeded in vitro with rabbit chondrocytes for 7 days and the cell/scaffold constructs were transplanted into rabbits’ articular defects, avoiding compromising the subchondral bone. Cell pellets and bare scaffolds were implanted as controls in a chondral defect. Results After 3 months with PCL scaffolds or cells/PCL constructs, defects were filled with white cartilaginous tissue; integration into the surrounding native cartilage was much better than control (cell pellet). The engineered constructs showed histologically good integration to the subchondral bone and surrounding cartilage with accumulation of extracellular matrix including type II collagen and glycosaminoglycan. The elastic modulus measured in the zone of the defect with the PCL/cells constructs was very similar to that of native cartilage, while that of the pellet-repaired cartilage was much smaller than native cartilage. Conclusion The results are quite promising with respect to the use of PCL scaffolds as aids for the regeneration of articular cartilage using tissue engineering techniques.

Decreased metalloproteinase production as a response to mechanical pressure in human cartilage: a mechanism for homeostatic regulation

Articular cartilage is optimised for bearing mechanical loads. Chondrocytes are the only cells present in mature cartilage and are responsible for the synthesis and integrity of the extracellular matrix. Appropriate joint loads stimulate chondrocytes to maintain healthy cartilage with a concrete protein composition according to loading demands. In contrast, inappropriate loads alter the composition of cartilage, leading to osteoarthritis (OA). Matrix metalloproteinases (MMPs) are involved in degradation of cartilage matrix components and have been implicated in OA, but their role in loading response is unclear. With this study, we aimed to elucidate the role of MMP-1 and MMP-3 in cartilage composition in response to mechanical load and to analyse the differences in aggrecan and type II collagen content in articular cartilage from maximum- and minimum-weight-bearing regions of human healthy and OA hips. In parallel, we analyse the apoptosis of chondrocytes in maximal and minimal load areas. Because human femoral heads are subjected to different loads at defined sites, both areas were obtained from the same hip and subsequently evaluated for differences in aggrecan, type II collagen, MMP-1, and MMP-3 content (enzyme-linked immunosorbent assay) and gene expression (real-time polymerase chain reaction) and for chondrocyte apoptosis (flow cytometry, bcl-2 Western blot, and mitochondrial membrane potential analysis). The results showed that the load reduced the MMP-1 and MMP-3 synthesis (p < 0.05) in healthy but not in OA cartilage. No significant differences between pressure areas were found for aggrecan and type II collagen gene expression levels. However, a trend toward significance, in the aggrecan/collagen II ratio, was found for healthy hips (p = 0.057) upon comparison of pressure areas (loaded areas > non-loaded areas). Moreover, compared with normal cartilage, OA cartilage showed a 10- to 20-fold lower ratio of aggrecan to type II collagen, suggesting that the balance between the major structural proteins is crucial to the integrity and function of the tissue. Alternatively, no differences in apoptosis levels between loading areas were found – evidence that mechanical load regulates cartilage matrix composition but does not affect chondrocyte viability. The results suggest that MMPs play a key role in regulating the balance of structural proteins of the articular cartilage matrix according to local mechanical demands.

Etiology of surgical site infections after primary total joint arthroplasties

We sought to characterize the causative pathogens of surgical site infections (SSIs) following primary total joint arthroplasties and to evaluate trends in the microbial etiology. We analyzed the etiology of SSIs following 2,632 total hip arthroplasty and knee arthroplasty procedures performed at our institution from 2004 through 2010. We calculated the annual proportion of SSIs accounted for each of the most common organisms and evaluated trends using the χ2 test for trend. SSIs were identified in 111 procedures (4.2%). The annual incidence of SSIs did not change significantly during the study period. Staphylococci were the most common cause of infection (59.6%) and most of infections were monomicrobial (82.8%). From 2004 to 2010, the annual proportion of infections due to gram‐negative bacilli (GNB) increased from 21.4% to 66.7% (p = 0.085 for trend). This increase was accompanied by a decline in the proportion of SSIs from coagulase‐negative staphylococci (p = 0.003). Additionally, we found an increase in the percentage of polymicrobial infections (from 7.1% in 2004 to 41.7% in 2010, p = 0.014). Multivariate analysis corroborated these trends. Our study reports an emergence of GNB as a cause of SSIs after primary total joint arthroplaties and an increase of polymicrobial infections.

Cell-free cartilage engineering approach using hyaluronic acid–polycaprolactone scaffolds: A study in vivo

Polycaprolactone scaffolds modified with cross-linked hyaluronic acid were prepared in order to establish whether a more hydrophilic and biomimetic microenvironment benefits the progenitor cells arriving from bone marrow in a cell-free tissue-engineering approach. The polycaprolactone and polycaprolactone/hyaluronic acid scaffolds were characterized in terms of morphology and water absorption capacity. The polycaprolactone and polycaprolactone/hyaluronic acid samples were implanted in a chondral defect in rabbits; bleeding of the subchondral bone was provoked to generate a spontaneous healing response. Repair at 1, 4, 12, and 24 weeks was assessed macroscopically using the International Cartilage Repair Society score and the Oswestry Arthroscopy Score and microscopically using immunohistological staining for collagen type I and type II, and for Ki-67. The presence of hyaluronic acid improves scaffold performance, which supports a good repair response without biomaterial pre-seeding.

Use of antibiotic-loaded cement in total knee arthroplasty

Bone cement has the capacity to release antibiotic molecules if any antibiotic is included in it, and these elution properties are improved as cement porosity is increased. In vitro studies have shown high local antibiotic concentration for many hours or few days after its use. Antibiotic loaded bone cement (ALBC) is helpful when treating an infection in total knee arthroplasty (TKA) revision surgery. The purpose of this paper was to review the evidence for the routine use of ALBC in TKA in the literature, its pros and cons. Many authors have recommended the use of ALBC also in primary TKA for infection prophylaxis, but the evidence based on data from National Registries, randomized clinical trials and meta-analysis suggest a protective effect of ALBC against infection when used in hips, but not (or only mild) in knees. A possible explanation to this finding is that the duration and quantity of locally elevated antibiotic levels after surgery are smaller in TKA, due to the smaller amount of cement used for fixation in TKA-only a layer in the bone surface. There are some concerns about the routine use of ALBC in primary TKA as prophylaxis against infection: Firstly, there is a risk of hypersensivity or toxicity even when the chance is highly improbable. Secondly, there is a reduction in the mechanical properties of the cement, but this can be probably neglected if the antibiotic is used in low doses, not more than 1 g per 40 g cement package. Another significant concern is the increased economic cost, which could be overlooked if there were enough savings in treating fewer prosthetic infections. Finally, there is also a risk of selection of antibiotic-resistant strains of bacteria and this could be the main concern. If used, the choice of the antibiotic mixed in ALBC should consider microbiological aspects (broad antimicrobial spectrum and low rate of resistant bacteria), physical and chemical aspects (thermal stability, high water solubility), pharmacological characteristics (low risk to allergic reactions or toxicity) and economic aspects (not too expensive). The most commonly used antibiotics in ALBC are gentamicin, tobramycin and vancomycin. In conclusion, there is a paucity of randomized clinical trials in the use of ALBC in primary TKAs and the actual evidence of the effect of ALBC in reducing the risk of infection is insufficient. This, in addition to concerns about patient safety, risks of increase in the antibiotic resistance of microorganisms and the increase in costs in the procedure, lead us to recommend a cautious use of ALBC, perhaps only in high-risk patients (immunocompromised, morbidly obese, diabetic and patients with previous history of fracture or infection around the knee) unless the benefits of ALBC use were fully proven. Meanwhile, the rigorous use of peri-operative prophylactic systemic antibiotics and adoption of efficient antiseptic procedures and improved surgical techniques must be considered the gold standard in infection prevention in TKA surgery.

Reduced Proliferation and Osteocalcin Expression in Osteoblasts of Male Idiopathic Osteoporosis

Osteoporosis is characterized by low bone mineral density (BMD), resulting in increasing susceptibility to bone fractures. In men, it has been related to some diseases and toxic habits, but in some instances the cause of the primary—or idiopathic—osteoporosis is not apparent. In a previous study, our group compared histomorphometric measurements in cortical and cancellous bones from male idiopathic osteoporosis (MIO) patients to those of control subjects and found reduced bone formation without major differences in bone resorption. To confirm these results, this study analyzed the etiology of this pathology, examining the osteoblast behavior in vitro. We compared two parameters of osteoblast activity in MIO patients and controls: osteoblastic proliferation and gene expression of COL1A1 and osteocalcin, in basal conditions and with vitamin D3 added. All these experiments were performed from a first-passage osteoblastic culture, obtained from osteoblasts that had migrated from the transiliac explants to the plate. The results suggested that the MIO osteoblast has a slower proliferation rate and decreased expression of genes related to matrix formation, probably due to a lesser or slower response to some stimulus. We concluded that, contrary to female osteoporosis, in which loss of BMD is predominantly due to increased resorption, low BMD in MIO seems to be due to an osteoblastic defect.

Arthroscopic Treatment of Hip Chondral Defects With Bone Marrow Stimulation and BST-CarGel

Microfracture, the current standard of care for the treatment of non-degenerative chondral lesions in the hip joint, is limited by the poor quality of the filling fibrocartilaginous tissue. BST-CarGel (Piramal Life Sciences, Laval, Quebec, Canada) is a chitosan-based biopolymer that, when mixed with fresh, autologous whole blood and placed over the previously microfractured area, stabilizes the blood clot and enhances marrow-triggered wound-healing repair processes. BST-CarGel has been previously applied in the knee, with statistically significant greater lesion filling and superior repair tissue quality compared with microfracture treatment alone. In this report we describe the application of BST-CarGel for the arthroscopic treatment of hip chondral lesions. Our preliminary data suggest that our BST-CarGel procedure provides high-quality repair tissue and therefore may be considered a safe, cost-efficient therapeutic choice for the treatment of hip chondral defects.

Preoperative antibiotic prophylaxis in prosthetic joint infections: not a concern for intraoperative cultures

BACKGROUND Culture negative prosthetic joint infections (PJI) still remain an issue even with the advantages of the new diagnostic tools for PJI. This is why some orthopedic surgeons have reservations relative to the use of preoperative antibiotic prophylaxis when a PJI is suspected. The purpose of the present study was to evaluate the influence of preoperative antibiotic prophylaxis on intraoperative cultures. MATERIAL AND METHODS An enhanced diagnostic protocol for PJI (Zimmerli criteria) was used for the inclusion criteria in order to collect all PJI that were seen in a university hospital. Patients were prospectively randomized into two groups. The control group received the classical preoperative antibiotic prophylaxis. The study group did not receive prophylaxis prior to surgery. RESULTS There were 14 patients in each group. They correspond to 13 total hip arthroplasty infections, 12 total knee arthroplasty infections and 3 reverse shoulder prosthesis infections. There were 10 patients in the study group and 10 patients in the control group with at least one positive microbiological criterion (P > 0.05). There were 4 patients in each group with a culture negative PJI (P > 0.05). CONCLUSIONS Preoperative antibiotic prophylaxis does not affect intraoperative cultures in suspected or confirmed PJI. Therefore it is essential to deliver antibiotic prophylaxis in any patient in which a prosthesis is to be implanted in order to protect the prosthesis from infection.