Chapter 35, Problem 3DAA

Building Better Bones Tiffany, shown in FIGURE 35.22, was born with multiple fractures in her arms and legs. By age six, she had undergone surgery to correct more than 200 bone fractures. Her fragile, easily broken bones are symptoms of osteogenesis imperfecta (OI), a genetic disorder caused by a mutation in a gene for collagen. As bones develop, collagen forms a scaffold for deposition of mineralized bone tissue. The scaffold forms improperly in children with OI. FIGURE 35.22 also shows the results of a test of a new drug. Treated children, all less than two years old, were compared to similarly affected children of the same age who were not treated with the drug.

	Vertebral
Treated	area in cm2		Fractures
child	(Initial)	(Final)	per year
1	14.7	16.7	1
2	15.5	16.9	1
3	6.7	16.5	6
4	7.3	11.8	0
5	13.6	14.6	6
6	9.3	15.6	1
7	15.3	15.9	0
8	9.9	13.0	4
9	10.5	13.4	4
Mean	11.4	14.9	2.6

	Vertebral
Treated	area in cm2		Fractures
child	(Initial)	(Final)	per year
1	18.2	13.7	4
2	16.5	12.9	7
3	16.4	11.3	8
4	13.5	7.7	5
5	16.2	16.1	8
6	18.9	17.0	6
Mean	16.6	13.1	6.3

FIGURE 35.22 Results of a clinical trial of a drug treatment for osteogenesis imperfecta (OI), which affects the child shown at right. Nine children with OI received the drug. Six others were untreated controls. Surface area of certain vertebrae was measured before and after treatment. Fractures occurring during the 12 months of the trial were also recorded.

3. How did the rate of fractures in the two groups compare?