Osteomark: a surgical navigation system for oral and maxillofacial surgery.

The purpose of this project was to test a surgical navigation tool designed to help execute a surgical treatment plan. It consists of an electromagnetically tracked pencil that is used to mark bone intraoperatively. The device was tested on a precision block, an ex vivo pig mandible and during performance of six endoscopic vertical ramus osteotomies on pig cadavers. The difference between actual pencil position and that displayed by the computer was measured three times each at ten 2mm holes on the block (n=30 observations) and on the ex vivo mandible (n=11 measurements). Errors between planned and actual osteotomy locations for the cadaver procedures were measured. The mean distance between known and displayed locations was 1.55 ± 0.72 mm on the precision block and 2.10 ± 0.88 mm on the pig mandible. The error measured marking the same point on the block multiple (n=5) times was 0.58 ± 0.37 mm. The mean error on the simulated osteotomies was 2.35 ± 1.35 mm. Osteomark was simple to use and permitted localisation of holes and osteotomies with acceptable accuracy. In the future, the device and algorithms will be revised to further decrease error and the system will be tested on live animals.

The 'easy street' myth: self harm among aboriginal and non-aboriginal female sole parents in urban state housing.

OBJECTIVE: To test the hypothesis that, controlling for socio-demographic factors, destructive behaviour among Aboriginal and non-Aboriginal female sole parents will not be significantly different. METHOD: This study took place among an urban population of sole parents in Adelaide, South Australia, living in government housing. Two sample subsets were made up of 52 Aboriginal and 45 non-Aboriginal mothers from similar postcodes. Trained interviewers administered a questionnaire which, in addition to basic demographic data, elicited information concerning finance, housing, upbringing, experience of abuse and police interaction. The major issue of concern in the study was suicide attempt. RESULTS: 1-in-3 of the whole sample, 2-in-5 of the non-Aboriginal and 1-in-4 of the Aboriginal subset had attempted suicide at least once and half more than once. Statistical differences among 'attempters' vs. 'non-attempters', irrespective of ethnicity, included increased familial alcohol abuse, physical and sexual abuse, economic difficulty, poor self esteem and perceived discriminatory treatment by welfare agencies and, in the case of Aboriginals, by police. CONCLUSION: The social environment is critical to understanding destructive behaviour, including self-harm, regardless of culture or ethnicity. The data show that suicide attempts among female sole parents in State-housing is one of the few health indices for which Aboriginal statistics are less than for non-Aboriginals. IMPLICATIONS: It is evident that class, rather than ethnicity, better explains self-harm in this urban population. It is suggested that reluctance to access services, especially in times of crisis, relates in part to perceptions of care services and that, for Aboriginals, the value of culturally appropriate community-run services have specific public health and policy implications.