Development and prevalence of femoroacetabular impingement-associated morphology in a paediatric and adolescent population: a CT study of 225 patients.

We investigated the development of CT-based bony radiological parameters associated with femoroacetabular impingement (FAI) in a paediatric and adolescent population with no known orthopaedic hip complaints. We retrospectively reformatted and reoriented 225 abdominal CTs into standardised CT pelvic images with neutral pelvic tilt and inclination (244 female and 206 male hips) in patients ranging from two to 19 years of age (mean 10.4 years). The Tönnis angle, acetabular depth ratio, lateral centre-edge angle, acetabular version and α-angle were assessed. Acetabular measurements demonstrated increased acetabular coverage with age and/or progressive ossification of the acetabulum. The α-angle decreased with age and/or progressive cortical bone development and resultant narrowing of the femoral neck. Cam and pincer morphology occurred as early as ten and 12 years of age, respectively, and their prevalence in the adolescent patient population is similar to that reported in the adult literature. Future aetiological studies of FAI will need to focus on the early adolescent population.

Arthroscopic reconstruction of the ligamentum teres: technique and early outcomes.

Femoroacetabular impingement causes groin pain and decreased athletic performance in active adults. This bony conflict may result in femoroacetabular subluxation if of sufficient magnitude. The ligamentum teres has recently been reported to be capable of withstanding tensile loads similar to that of the anterior cruciate ligament, and patents with early subluxation of the hip may become dependent on the secondary restraint that is potentially provided by the ligamentum teres. Rupture of the ligamentum may thus cause symptomatic hip instability during athletic activities. An arthroscopic reconstruction of the ligamentum teres using iliotibial band autograft was performed in an attempt to restore this static stabiliser in a series of four such patients. Early clinical results have been promising. The indications, technique and early outcomes of this procedure are discussed.

Characterization of pro-apoptotic and matrix-degradative gene expression following induction of osteoarthritis in mature and aged rabbits.

OBJECTIVE: The genetic and molecular changes leading to the distinctive alterations of aged cartilage and its propensity for developing osteoarthritis (OA) are unknown. We hypothesized that pro-apoptotic and matrix-degradative gene expression in a rabbit model of induced OA using mature and aged animals might elucidate this relationship. METHODS: Groups of six mature and aged rabbits underwent anterior cruciate ligament transection (ACLT) and were sacrificed 4 weeks after surgery to create an Outerbridge grade II OA. RNA was extracted from the articular cartilage and menisci of the affected knee and was examined with regard to expression of the following genes: Caspase 8, Fas, Fas ligand (Fas-L), p53, aggrecanase, matrix metalloproteinase (MMP)-1, and MMP-3-MMP-13. A second cohort of mature and aged animals was sacrificed with no intervention to the joint and gene expression was assessed in a similar manner. RESULTS: Fas and Caspase 8 showed significantly increased expression in the cartilage of mature animals with induced OA when compared to unoperated controls while induction of OA in aged rabbits did not significantly increase expression of any of the apoptosis genes. Among unoperated animals, the aged cohort showed significantly increased expression of MMP-1 and aggrecanase in cartilage when compared to mature animals. MMP-13 expression was upregulated in aged cartilage following induction of OA. Although ACLT animals showed gross thinning and irregularities within the meniscus, only the expression of Caspase 8 in the aged rabbits was significantly increased after induction of OA. CONCLUSIONS: Aging of articular cartilage shares some qualities with the development of OA, as seen in the parallel increases in gene expression of Caspase 8 and Fas. Although this may imply a common mechanism of cartilage degeneration in aging and OA or even a spectrum of disease, both are complex processes requiring further study.

Growth dynamics in a natural biofilm and its impact on oral disease management.

Measurements of the microbial growth dynamics in natural biofilm communities are almost non-existent. In a recent study, the biofilm formation on teeth was examined. A previously unknown active period of bacterial division occurred at a certain density of plaque bacteria on tooth enamel. The density-dependent cell-division phase of plaque formation contributed 90% of the biomass in the first 24 hrs of plaque formation. This suggested that growth was induced by the bacteria. In vitro assays were developed for rapid evaluation of the growth of surface-linked bacteria by the measurement of cellular components associated with growth on a per cell per time basis. Cell-free supernatants (termed START) of media in contact with bacteria were assayed for their effects on DNA synthesis and other cellular components associated with growth. START was found to increase the incorporation of [3H-methyl]-thymidine on a per cell per time basis, when compared with media not in contact with bacteria. Additional in vivo studies and in situ-based models of complex biofilms are needed if all of the mechanisms involved in the rapid accumulation of biofilm bacteria on teeth and other surfaces are to be understood.

Physical characterization of the replication origin of the cryptic plasmid pCB101 isolated from Clostridium butyricum NCIB 7423.

The complete nucleotide sequence of a 3484-bp Sau3A fragment, previously shown to carry the replication origin of the Clostridium butyricum NCIB 7423 plasmid pCB101 (6.05 kb), has been determined. Of the four open reading frames (ORF A-D) identified within this fragment, two (B and C) were shown to be encoding by in vitro transcription/translation assays. Evidence was obtained that both polypeptides are required for autonomous replication of the plasmid in Bacillus subtilis. ORF C is immediately preceded by a small ORF (C') that encodes a relatively small polypeptide (50 amino acids) that demonstrates significant homology with RepA of plasmid pLS1. Whereas the ORF C polypeptide (27,100 Da) exhibits no homology to any known protein, that encoded by ORF B (RepB, 43,039 Da) exhibits significant homology with the Rep proteins of the pC194/pUB110 subfamily of single-strand (ss) DNA plasmids, which are widely distributed in gram-positive bacteria. Conserved amino acids include the presumed active site of topoisomerase activity and four cysteine residues in the N-terminus of all Rep proteins compared. The repB gene is preceded by a sequence motif exhibiting substantial homology to the "plus" origins of this family of ss DNA plasmids and was shown to act as a "hot spot" for deletion formation in certain plasmid chimaeras. The compelling suggestion that pCB101 replicates via a rolling circle mechanism was substantiated by the demonstration of ss DNA replication intermediates in B. subtilis cells carrying a pCB101-derived plasmid.

Transfer of Tn1545 and Tn916 to Clostridium acetobutylicum.

Tn1545, a conjugative transposon originally discovered in Streptococcus pneumoniae, has been transferred from Enterococcus faecalis and Bacillus subtilis to Clostridium acetobutylicum NCIB 8052. Transfer between different strains of C. acetobutylicum has also been observed. Insertion of Tn1545 into the C. acetobutylicum chromosome occurred at multiple sites, as shown by Southern hybridization. Although ermAM (erythromycin-resistance) was the most satisfactory marker for primary selection of transconjugants, all three Tn1545-encoded antibiotic resistance genes (aphA-3, ermAM, and tetM) were apparently expressed in C. acetobutylicum. Our results indicate that Tn1545 is potentially useful for undertaking mutagenesis and mutational cloning in this industrially important organism. Transfer of another conjugative transposon, Tn916, from E. faecalis to C. acetobutylicum NCIB 8052 was also apparently detected. Circumstantial evidence suggests that there may be a hot spot for Tn916 insertion in the C. acetobutylicum NCIB 8052 chromosome.