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1.  Insufficient Bone Regenerate after Intramedullary Femoral Lengthening: Risk Factors and Classification System 
Control of distraction rate with an intramedullary skeletal kinetic distractor (ISKD) may be problematic and a high distraction rate may result in insufficient bone regenerate.
Are distraction problems preventable when using the ISKD, and what are the risk factors for and radiologic types of insufficient bone regenerate during ISKD lengthening?
Patients and Methods
We analyzed 37 consecutive ISKD femoral lengthening procedures in 35 patients with a mean age 33 ± 11 years and minimum followup of 12 months (average, 27 ± 9 months; range, 12–55 months). The average length gain was 42.8 ± 12.9 mm.
Eight patients had problems during distraction: seven had “runaway nails” and one had a nondistracting nail. Insufficient bone regenerate developed in eight patients. Important risk factors were a distraction rate greater than 1.5 mm/day (9.1 times higher risk), age 30 years or older, smoking, and lengthening greater than 4 cm. Less important risk factors identified were creation of the osteotomy at the site of previous trauma or surgery and acute correction of associated deformities. We proposed a radiologic classification for failure of bone regeneration: partial regenerate failure (Type I) or complete failure resulting in a segmental defect subdivided according to a length of 3 cm or less (Type IIa) or greater than 3 cm (Type IIb).
Distraction problems with the ISKD were related mostly to internal malfunction of the lengthening mechanism. A distraction rate greater than 1.5 mm/day should be avoided in femoral intramedullary lengthening. Smoking should be a contraindication for femoral lengthening.
Level of Evidence
Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.
PMCID: PMC3008908  PMID: 20361281
2.  Collagen type I hydrogel allows migration, proliferation and osteogenic differentiation of rat bone marrow stromal cells 
Hydrogels are potentially useful for many purposes in regenerative medicine including drug and growth factor delivery, as single scaffold for bone repair or as a filler of pores of another biomaterial in which host mesenchymal progenitor cells can migrate in and differentiate into matrix-producing osteoblasts. Collagen type I is of special interest as it is a very important and abundant natural matrix component. The purpose of this study was to investigate whether rat bone marrow stromal cells (rBMSCs) are able to adhere to, to survive, to proliferate and to migrate in collagen type I hydrogels and whether they can adopt an osteoblastic fate. rBMSCs were obtained from rat femora and plated on collagen type I hydrogels. Prior to harvest by day 7, 14, and 21, hydrogels were fluorescently labeled, cryo-cut and analyzed by fluorescent-based and laser scanning confocal microscopy to determine cell proliferation, migration, and viability. Osteogenic differentiation was determined by alkaline phosphatase activity. Collagen type I hydrogels allowed the attachment of rBMSCs to the hydrogel, their proliferation, and migration towards the inner part of the gel. rBMSCs started to differentiate into osteoblasts as determined by an increase in alkaline phosphatase activity after two weeks in culture. This study therefore suggests that collagen type I hydrogels could be useful for musculoskeletal regenerative therapies.
PMCID: PMC2891839  PMID: 20186733
Collagen type I hydrogel; bone marrow stromal cells; cell migration; osteogenic differentiation; bone regeneration

Results 1-2 (2)