Initial Experience With Percutaneous IM Rodding of the Humeri in Children With Osteogenesis Imperfecta.

BACKGROUND: To report a single-center surgical experience treating humeral deformity and fractures in children with osteogenesis imperfecta (OI) using the Fassier-Duval (FD) intramedullary elongating rods. METHODS: A retrospective review was conducted between December 2005 and July 2013 of all OI patients who underwent FD rodding with a minimum of 1-year follow-up. All patients were also being concurrently treated with bisphosphonates. RESULTS: Eighteen patients underwent internal fixation on a total of 35 humeri: 7 males and 11 females with an average age of 49 months. Thirty-five procedures were performed using FD rodding, with 5 utilizing only the male portion. Thirty procedures were primary FD implantation and 5 were revisions. Twelve patients had type III OI and 6 patients type IV OI. Indications for surgery included recurrent fracture, severe bowing deformity, and pain. Osteotomy methods included closed osteoclasis, percutaneous, or open osteotomies. Two patients required transfusions during their hospital stay. At our determined endpoint, 23 humeri (65.7%) had acceptable results with a mean follow-up time of 43 months (SD=27) with no revision. The remaining 12 humeri (34.3%) necessitated revision with a mean time to revision of 35 months (SD=29). Reasons for revision included: migration resulting in pain and functional difficulty (8.6%), migration with bowing (8.6%), and hardware failure secondary to trauma (8.6%). In addition, 2 revisions were required for nonunion (5.7%) and 1 for malunion (2.9%). To our knowledge, all other osteotomies performed during surgery resulted in bony union. CONCLUSIONS: The use of the FD system for correction of humeral deformity demonstrates a reasonable option to improve comfort and function in children with recurrent fractures and deformity secondary to OI. The FD system allows for decreased revision rates and less morbid instrumentation. LEVEL OF EVIDENCE: Level IV-retrospective case series.

Drosophila muller f elements maintain a distinct set of genomic properties over 40 million years of evolution.

The Muller F element (4.2 Mb, ~80 protein-coding genes) is an unusual autosome of Drosophila melanogaster; it is mostly heterochromatic with a low recombination rate. To investigate how these properties impact the evolution of repeats and genes, we manually improved the sequence and annotated the genes on the D. erecta, D. mojavensis, and D. grimshawi F elements and euchromatic domains from the Muller D element. We find that F elements have greater transposon density (25-50%) than euchromatic reference regions (3-11%). Among the F elements, D. grimshawi has the lowest transposon density (particularly DINE-1: 2% vs. 11-27%). F element genes have larger coding spans, more coding exons, larger introns, and lower codon bias. Comparison of the Effective Number of Codons with the Codon Adaptation Index shows that, in contrast to the other species, codon bias in D. grimshawi F element genes can be attributed primarily to selection instead of mutational biases, suggesting that density and types of transposons affect the degree of local heterochromatin formation. F element genes have lower estimated DNA melting temperatures than D element genes, potentially facilitating transcription through heterochromatin. Most F element genes (~90%) have remained on that element, but the F element has smaller syntenic blocks than genome averages (3.4-3.6 vs. 8.4-8.8 genes per block), indicating greater rates of inversion despite lower rates of recombination. Overall, the F element has maintained characteristics that are distinct from other autosomes in the Drosophila lineage, illuminating the constraints imposed by a heterochromatic milieu.