Effect of modification of hydroxyapatite/collagen composites with sodium citrate, phosphoserine, phosphoserine/RGD-peptide and calcium carbonate on bone remodelling.

This study describes the early interface reaction of cancellous bone to a nanocrystalline hydroxyapatite cement containing type I collagen (HA/Coll) and its modifications with sodium citrate (CI), calcium carbonate (CA), phosphoserine (P) and phosphoserine plus RGD-peptide (RGD). Cylindrical implants of HA/Coll and its modifications were inserted into the tibia of Wistar rats. We analysed 6 specimens per group at days 2, 4, 7, 14 and 28. CI, P and RGD modifications showed improved material properties (finer microstructure and higher compressive strength) compared to CA and HA/Coll implants. The powder X-ray diffraction (XRD) showed that the addition of P and CI led to an increase of alpha-TCP peaks while the diffraction patterns of the non-modified cement (HA/Coll) were quite similar with that of natural bone. All of the implants healed without adverse reactions. A significantly higher number of TRAP-positive osteoclasts were observed around CI, RGD and P on day 7 compared to CA and HA/Coll. Around CI, P and RGD a significantly delayed increase of ED1-positive mononuclear cells was detected. The amount of direct bone contact after 28 days was significantly higher around CI, P and RGD compared to CA and HA/Coll implants. The addition of CI, P and RGD appears to enhance bone remodelling at the early stages of bone healing, leading to increased bone formation around HA/Coll composite cements.

Risk-inducing activities leading to injuries in a child and adolescent population of Germany.

BACKGROUND: Injuries are the most common cause of mortality in children, also accounting considerably for childhood morbidity. However, data on injuries only provide valid information on the actual risk of each injury-causing activity when taken in consideration of the relationship with actual activity exposure data. Therefore, the primary goal of this investigation is to determine the relative risk of normal child and adolescent activities. METHODS: From January 1, 1999 to December 31, 2001, a school questioning in regard to social, pedagogic, and leisure activities was performed among 2,325 students ranging from 6 to 17 years old. A total of 3,645 injuries sustained by children and adolescents treated at the surgical emergency department of the University Hospital Dresden were analyzed. Furthermore, a danger awareness test was performed. RESULTS: Forty-three percent of all injuries happened during leisure time, 41% at school, 8% in traffic, and 8% at home. Bicycle riding was pointed out as the most frequent leisure activity, regardless of gender and age. Horse riding had a 9-fold increased risk and moped driving had a 23.75-fold increased risk for injury compared with adolescent bike riding. Horse riding and snowboarding showed an increased risk for injury in children (5.6- and 4.2-fold, relative to biking). The level of danger awareness was significantly lower in children with a history of frequent injuries. CONCLUSIONS: The riskier activities were horse-riding, moped driving, and snowboarding. The level of danger awareness did affect the frequency of injuries. The authors recommend a danger awareness test for all children to identify those who would benefit from injury prevention training.