High-performance total knee replacement.

The concept of a high-performance total knee replacement has gained prominence because of continued technological improvements by implant manufacturers and the changing expectations of an increasingly younger, more active patient population. Improvements in surgical technique, instrumentation, implant design, biomaterials, and implant fixation have occurred in recent years. The literature is inconclusive whether novel approaches can lead to improvements in patient satisfaction rates, address objectively measured parameters, and improve implant survival rates, while doing so in a cost-efficient manner.

Matrix metalloproteinases that associate with and cleave bone morphogenetic protein-2 in vitro are elevated in hypertrophic fracture nonunion tissue.

OBJECTIVES: A delayed union or a nonunion of a fracture is a potentially adverse complication. Understanding the mechanisms of nonunion development may lead to improved treatment modalities. Proteases such as the matrix metalloproteinases play important roles in bone remodeling and repair, in which an imbalance or a nonfunctioning enzyme may lead to defects in bone healing (nonunion). The purpose of this pilot study was twofold: first to define an mRNA expression profile of all the matrix metalloproteinases (MMPs), a disintegrin and metalloproteinases with thrombospondin motif (ADAMTS) enzymes, and their inhibitors (TIMPs) within fracture nonunion tissue, and second to compare this profile with mineralized fracture callus. METHODS: Using a systematic real-time polymerase chain reaction, we screened the gene expression profiles of all members of the MMPs, ADAMTS, and their inhibitor TIMPs on human fracture nonunion tissue and matched mineralized callus tissue. Significant results were further analyzed using Western immunoblotting, immunohistochemistry, and in vitro protein interaction assays with bone morphogenetic protein-2. RESULTS: This analysis confirmed MMP-7 and MMP-12 as two unidentified enzymes expressed in fracture nonunion tissue. Both MMP-7 and MMP-12 mRNAs were significantly elevated in nonunion tissue when compared with local mineralized callus from the same site (P < 0.001); the elevated protein levels of interest were visualized through immunoblotting and immunohistochemistry. In addition, these two MMPs were found to directly bind to and degrade bone morphogenetic protein-2 in vitro. CONCLUSION: Collectively, our findings indicate that tissue present at the site of hypertrophic nonunions commonly expresses significantly higher levels of MMP-7 and MMP-12 in relation to mineralized fracture callus. Both were found to directly inactivate bone morphogenetic protein-2 in vitro, the best established growth factor in bone formation and repair.

A broken scalpel blade tip: an unusual complication of knee arthroscopy.

The case of a patient is presented in whom a No. 11 scalpel blade was inadvertently broken and embedded within the lateral femoral condyle during initial arthroscopic portal creation. After a thorough diagnostic arthroscopy and synovectomy to expose the distal femoral articular surface was unsuccessful, luoroscopy was performed to localize the blade fragment in orthogonal planes. The blade tip was eventually retrieved from its position below the surface of the cartilage. The details of the loss and recovery of the blade fragment reinforce that exceptional care must be taken and attention given during the creation of portals, particularly when resistance is encountered. Additionally, all instruments, especially scalpel blades, should be exam- ined carefully when removed from the knee joint.

Cartilage oligomeric matrix protein associates with granulin-epithelin precursor (GEP) and potentiates GEP-stimulated chondrocyte proliferation.

Mutations in human cartilage oligomeric matrix protein (COMP) have been linked to the development of pseudoachondroplasia and multiple epiphyseal dysplasia; however, the functions of both wild-type and mutant COMP in the skeletogenesis remain unknown. In an effort to define the biological functions of COMP, a functional genetic screen based on the yeast two-hybrid system was performed. This led to the identification of granulin-epithelin precursor (GEP), an autocrine growth factor, as a COMP-associated partner. COMP directly binds to GEP both in vitro and in vivo, as revealed by in vitro pull down and co-immunoprecipitation assays. GEP selectively interacts with the epidermal growth factor repeat domain of COMP but not with the other three functional domains of COMP. The granulin A repeat unit of GEP is required and sufficient for association with COMP. COMP co-localizes with GEP predominantly in the pericellular matrix of transfected rat chondrosarcoma cell and primary human chondrocytes. Staining of musculoskeletal tissues of day 19 mouse embryo with antibodies to GEP is restricted to chondrocytes in the lower proliferative and upper hypertrophic zones. Overexpression of GEP stimulates the proliferation of chondrocytes, and this stimulation is enhanced by COMP. In addition, COMP appears to be required for GEP-mediated chondrocyte proliferation, since chondrocyte proliferation induced by GEP is dramatically inhibited by an anti-COMP antibody. These findings provide the first evidence linking the association of COMP and GEP and identifying a previously unrecognized growth factor (i.e. GEP) in cartilage.