The Toronto District School Board (TDSB) worked with an
independent, qualified playground consultant to develop a
methodology for assessing the compliance of all playground
equipment in its jurisdiction with the 1998 CSA standards and
1990 CSA guidelines. Details of the methodology are given in the
online appendix at www.cmaj.ca/cgi/content/full/172/11
/1443/DC1. In the spring of 2000, the same consultant assessed
all playground equipment in TDSB elementary schools (n = 398)
for CSA compliance and indicated whether the equipment in each
case should be left as is, repaired or retrofitted, or removed and
replaced. Two factors were considered in making the decision: the
severity of injury that could result from using the equipment and,
where equipment was noncompliant, the feasibility of achieving
compliance through repair or retrofit.
The assessment identified 136 schools with playground equipment
that represented a severe hazard (i.e., an imminent risk of
serious and permanent injury, usually indicating risk of a fall
from more than 1.5 m or a fall onto unsuitable surfacing), did not meet CSA standards and was impractical to retrofit to make safer
(Fig. 1). The equipment was removed from all 136 schools in the
summer of 2000. By Dec. 31, 2001, the equipment had been fully
replaced in 86 schools, which constituted the intervention group;
it had not been fully replaced in the remaining 50 schools, and
they were excluded from analysis (Fig. 2). Injury rates before and
after equipment replacement were compared in the intervention
schools. A total of 225 schools had equipment that did not require
replacement, and they constituted the nonintervention
schools; injury rates in this group served as an indicator of stability
of baseline injury rates in this natural experiment. A total of
34 557 students attended the intervention schools, and 88 417 attended
the nonintervention schools. All schools included grades
1 through 6 and were public schools.
A database of incident reports from the Ontario School Board
Insurance Exchange was used to identify all injury events occurring
at TDSB schools between January 1998 and December 2002
inclusive. Information in the database is provided by school staff
whenever an incident occurs in the school during school hours.
The threshold for completing a report is “whenever medical or
dental attention is required,” and this includes injuries attended
to by teachers or school staff, as well as those in which the child
went home or to a health facility. We included all injuries to children
4–11 years of age that occurred within the school playground.
Research assistants, blinded to the study purpose and
date of injury (i.e., before or after equipment removal), coded all
playground incidents on the basis of written descriptions from
the database. Injuries where equipment was explicitly mentioned
in the written description were flagged as “equipment related”
for subanalysis.
Playground injury rates (injuries per 1000 children per month)
were compared at the intervention schools and at the nonintervention
schools before equipment removal and after equipment
replacement. Person-time denominators used the average yearly
enrollment in each school multiplied by the number of months
that the school was in session. The same 10-month calendar periods
were selected before and after the intervention to avoid bias
related to seasonal variation in injury. The pre-intervention period
was from September 1999 to June 2000, and the postintervention
period was from January 2002 to December 2002
(excluding July and August). To adjust for clustering within
schools, injury rates and relative risks (RRs), along with their confidence intervals (CIs), were estimated using random-effect metaanalytic
methods as proposed by Thompson and colleagues.13
Expected post-intervention injury rates in the intervention
schools were calculated by multiplying the pre-intervention rates
in intervention schools by the ratio of post-intervention to preintervention
rates in the nonintervention schools. The proportion
of injuries prevented (etiological fractions)14 were calculated by
subtracting observed from expected rates and expressing the result
as a percentage of the expected rate. The analysis was repeated for
the subset of injuries flagged as equipment related.