Risk Factors for Injuries from in-Line Skating and the Effectiveness of Safety Gear

Abstract

Of the estimated 22.5 million people participating in in-line skating in the United States in 1995, about 100,000 were sufficiently injured so as to require emergency department care. We investigated the effectiveness of wrist guards, elbow pads, knee pads, and helmets in preventing skating injuries.
We used data from the 91 hospital emergency departments participating in the National Electronic Injury Surveillance System, a national probability sample of randomly selected hospitals with 24-hour emergency departments. Injured in-line skaters who sought medical attention between December 1992 and July 1993 were interviewed by telephone. We conducted a case-control study of skaters who injured their wrists, elbows, knees, or heads as compared with skaters with injuries to other parts of their bodies.
Of 206 eligible injured subjects, 161 (78 percent) were interviewed. Wrist injuries were the most common (32 percent); 25 percent of all injuries were wrist fractures. Seven percent of injured skaters wore all the types of safety gear; 46 percent wore none. Forty-five percent wore knee pads, 33 percent wrist guards, 28 percent elbow pads, and 20 percent helmets. The odds ratio for wrist injury, adjusted for age and sex, for those who did not wear wrist guards, as compared with those who did, was 10.4 (95 percent confidence interval, 2.9 to 36.9). The odds ratio for elbow injury, adjusted for the number of lessons skaters had had and whether or not they performed trick skating, was 9.5 (95 percent confidence interval, 2.6 to 34.4) for those who did not wear elbow pads. Non-use of knee pads was associated with a nonsignificant increase in the risk of knee injury (crude odds ratio, 2.2; 95 percent confidence interval, 0.7 to 7.2). The effectiveness of helmets could not be assessed.
Wrist guards and elbow pads are effective in protecting in-line skaters against injuries.

Full text

1630

November 28, 1996
The New England Journal of Medicine
RISK FACTORS FOR INJURIES FROM IN-LINE SKATING
AND THE EFFECTIVENESS OF SAFETY GEAR
R
ICHARD
A. S
CHIEBER
, M.D., M.P.H., C
HRISTINE
M. B
RANCHE
-D
ORSEY
, P
H
.D., G
EORGE
W. R
YAN
, P
H
.D.,
G
EORGE
W. R
UTHERFORD
, J
R
., M.S., J
UDY
A. S
TEVENS
, M.S., M.P.H.,
AND
J
OANN
O’N
EIL
, B.S.
A
BSTRACT
Background
Of the estimated 22.5 million people
participating in in-line skating in the United States in
1995, about 100,000 were sufficiently injured to re-
quire emergency department care. We investigated
the effectiveness of wrist guards, elbow pads, knee
pads, and helmets in preventing skating injuries.
Methods
We used data from the 91 hospital emer-
gency departments participating in the National Elec-
tronic Injury Surveillance System, a national proba-
bility sample of randomly selected hospitals with
24-hour emergency departments. Injured in-line skat-
ers who sought medical attention between Decem-
ber 1992 and July 1993 were interviewed by tele-
phone. We conducted a case–control study of skaters
who injured their wrists, elbows, knees, or heads as
compared with skaters with injuries to other parts of
their bodies.
Results
Of 206 eligible injured subjects, 161 (78
percent) were interviewed. Wrist injuries were the
most common (32 percent); 25 percent of all injuries
were wrist fractures. Seven percent of injured skat-
ers wore all the types of safety gear; 46 percent wore
none. Forty-five percent wore knee pads, 33 percent
wrist guards, 28 percent elbow pads, and 20 percent
helmets. The odds ratio for wrist injury, adjusted for
age and sex, for those who did not wear wrist guards,
as compared with those who did, was 10.4 (95 per-
cent confidence interval, 2.9 to 36.9). The odds ratio
for elbow injury, adjusted for the number of lessons
skaters had had and whether or not they performed
trick skating, was 9.5 (95 percent confidence interval,
2.6 to 34.4) for those who did not wear elbow pads.
Nonuse of knee pads was associated with a nonsig-
nificant increase in the risk of knee injury (crude
odds ratio, 2.2; 95 percent confidence interval, 0.7
to 7.2). The effectiveness of helmets could not be as-
sessed.
Conclusions
Wrist guards and elbow pads are ef-
fective in protecting in-line skaters against injuries.
(N Engl J Med 1996;335:1630-5.)
©1996, Massachusetts Medical Society.
From the National Center for Injury Prevention and Control, Centers
for Disease Control and Prevention, Atlanta (R.A.S., C.M.B.-D., G.W.
Ryan, J.A.S., J.O.); and the Directorate for Epidemiology and Health Sci-
ences, Consumer Product Safety Commission, Washington, D.C. (G.W.
Rutherford). Address reprint requests to Dr. Schieber at the National Cen-
ter for Injury Prevention and Control, Centers for Disease Control and
Prevention, Mailstop K-63, 4770 Buford Hwy., NE, Atlanta, GA 30341.
The views expressed by the authors do not necessarily represent those of
the Consumer Product Safety Commission.
N-LINE skating is a fast-growing recreational
sport in the United States. In-line skates, with
three, four, or five low-friction wheels set in a
single row, afford greater maneuverability and
speed than traditional quad skates, which have four
wheels arranged in two rows. An estimated 22.5 mil-
lion people participated in 1995, reflecting a 79 per-
cent increase over the 1993 figure.
1
During the same
I
two-year period, the estimated number of in-line
skaters injured badly enough to require emergency
department care increased by 169 percent to an an-
nual level of 99,500 (in 1995).
2
The most common
site of injury is the wrist, accounting for 37 percent
of all skating injuries, and two thirds of wrist injuries
are fractures.
3,4
Wrist guards are designed to prevent
sudden extreme hyperextension, to absorb shock
and dissipate kinetic forces by enabling the skater to
slide forward on the guard’s hard volar plate, and to
prevent gravel burns. Helmets, elbow pads, and knee
pads are designed to absorb shock during a fall. The
use of all four of these items of safety gear has been
recommended,
5-7
but their effectiveness, although
suggested,
3-5,8
had been untested. We surveyed a rep-
resentative sample of injured in-line skaters who re-
ceived emergency department treatment in order to
identify behavioral and environmental risk factors
for injury, the mechanism and nature of injury, and
the degree of protection afforded by safety gear.
METHODS
Sample Design and Data Acquisition
Subjects were drawn from a sampling frame consisting of all pa-
tients injured during the study period who were wearing in-line
skates and sought treatment at 1 of the 91 hospital emergency
departments participating in the National Electronic Injury Sur-
veillance System (NEISS).
9
NEISS is a national probability sam-
ple, stratified into four levels according to the annual number of
emergency visits, of randomly selected U.S. hospitals with 24-hour
emergency departments. The study period had two parts: Decem-
ber 25, 1992, through April 7, 1993, and July 1 to July 31, 1993.
We developed a list of possible risk factors for injury by con-
ducting focus-group discussions with skaters
10
and by interview-
ing novice and experienced skaters. We constructed a 20-minute
questionnaire to gather information on the characteristics of in-
jured skaters, the circumstances surrounding the injury, and the
use of safety gear.
Injured skaters were interviewed by telephone by Dr. Schieber
during August 1993 after providing informed consent. If the
skater was a minor, consent was obtained from the participant
and a parent. Children were interviewed directly (although a par-
ent was present in a few instances); the parent was then inter-
viewed privately to verify the child’s reported level of experience,
the account of the injury, and the use of safety gear at the time.
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EFFECTIVENESS OF SAFETY GEAR IN PREVENTING INJURIES FROM IN-LINE SKATING
Volume 335 Number 22

1631
The study was conducted with approval from the Office of Man-
agement and Budget, which authorized the Consumer Product
Safety Commission to conduct confidential, selective telephone
surveys of persons with product-related injuries to learn of the in-
teractions among the product, the victims, and the environment.
Definitions and Analytic Design
Subjects were assigned to case and control groups for our anal-
yses of the relative benefits of the use of wrist guards, elbow pads,
knee pads, and helmets. To enhance precision, we defined four
risk groups according to the four anatomical sites shielded by the
various types of safety gear: the wrist, elbow, knee, and head (or
face). Subjects were classified in a particular risk group if the giv-
en anatomical region had been exposed to injury in the subject’s
fall. For example, subjects were included in the wrist risk group if
they fell on one or both outstretched arms or otherwise struck
the wrist or lower arm during the fall. Within each risk group, we
defined as case patients those skaters who injured the specified
anatomical site seriously enough to require medical attention.
The controls were skaters in the risk group who did not injure
the specified site, although they did injure another part of their
body. The main exposure variable was the self-reported use (or
*The percentages given are calculated for an esti-
mated 6331 persons treated in emergency depart-
ments nationally during the study period. They are
based on data from 161 injured skaters, weighted ac-
cording to the hospital in the NEISS sample in
which they were treated. These values do not include
subjects for whom the following were unknown:
ability level (1 percent of the total), number of les-
sons taken (2 percent), or condition of skates (1 per-
cent).
†Subjects could give more than one reason.
‡Of subjects who gave this reason, 34 percent
were injured while playing roller hockey.
§Of subjects who gave this reason, 40 percent
were injured while doing tricks.
T
ABLE
1.
S
ELECTED
C
HARACTERISTICS
OF
I
NJURED
I
N
-L
INE
S
KATERS
IN
THE
N
ATIONAL
S
AMPLE
.*
C
HARACTERISTIC
%
OF
S
AMPLE
Ability level
Novice 10
Beginner 34
Intermediate 37
Expert 18
No. of times in-line skating
1–5 25
6–12 12
13–99 26

100 37
Reasons for participation†
To get exercise 75
To play roller hockey‡ 37
For transportation 35
To perform tricks§ 31
No. of lessons taken
050
1–5 37

611
Ownership of skates
Owned 72
Rented or borrowed 28
Condition of skates
Good 85
Fair or poor 14
*The values given are calculated for an estimated
6331 persons treated in emergency departments na-
tionally during the study period. They are based on
data from 161 injured skaters, weighted according to
the hospital in the NEISS sample in which they were
treated.
†The hazard was usually a defect or debris in the
road.
‡Collisions usually occurred with another skater,
and less than 1 percent involved a motor vehicle.
§More than one response was allowed. Percentag-
es given for key-cause citations are of those who cit-
ed the factor.
¶Thirteen percent of skaters had more than one
injury.

Seventy-two percent of wrist injuries, 48 percent of
elbow injuries, 38 percent of head injuries, and 34 per-
cent of knee injuries were major. Six percent of patients
with major injuries were admitted to the hospital.
T
ABLE
2.
C
HARACTERISTICS
OF
F
ALLS
AND
OF
I
NJURIES
S
USTAINED
BY
I
N
-L
INE
S
KATERS
.*
C
HARACTERISTIC
%
OF
S
AMPLE
Location of fall
Sidewalk or driveway 26
Street 22
Park or bike path 19
Indoors 10
Parking lot 9
Other 14
Proximate cause of fall
Spontaneous loss of balance 41
Striking a stationary hazard† 40
Striking a moving object‡ 11
Swerving to avoid hazard or collision 4
Other 4
Special factors§
Hazardous road condition†
Cited 53
Cited as key cause 63
Skating out of control
Cited 25
Cited as key cause 67
Poor visibility (twilight or darkness)
Cited 17
Cited as key cause 6
Fatigue
Cited 11
Cited as key cause 37
Anatomical site of primary injury¶
Wrist 32
Lower leg (including ankle) 13
Face (or chin) 12
Elbow 9
Knee 6
Head 5
Other 23
Type of injury
Wrist fracture 25
Face or chin laceration 10
Wrist sprain 6
Elbow fracture 5
Lower-leg fracture 5
Ankle sprain 4
Severity of injury

Major 51
Minor 49
Safety gear worn at time of injury
Wrist guards 33
Elbow pads 28
Knee pads 45
Helmet 20
All the above gear 7
No gear 46
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1632

November 28, 1996
The New England Journal of Medicine
nonuse) of the appropriate safety gear for the specified anatomical
site. The outcome variable was the presence or absence of an in-
jury to that anatomical site, as reported by the skater and con-
firmed by the NEISS record.
Selected characteristics of the skaters were considered as covar-
iates. The subjects were classified according to age into groups:
elementary-school children (6 to 12 years), junior or senior high-
school youth (13 to 18 years), and adults (19 years or older).
Subjects comfortable standing up on skates were classified as nov-
ices; beginners were those who could make a simple turn on two
skates; intermediates could perform a crossover turn (made with
a sequence of short, alternating cross-steps); and experts could do
two or more stunts. In-line skating experience was classified ac-
cording to the number of times the skater had participated in the
sport. Ice hockey, ice skating, alpine skiing, roller skating, bicycle
racing, and mountain bicycling were defined as cross-training
sports. Lessons were defined as prior training with an instructor
or accompaniment by a more skilled skater. The levels of per-
ceived exertion at the time of injury, as assessed by the skaters
themselves, were warming-up, cruising, and fatigued. Other covar-
iates in the analysis were sex, handedness, and whether the skater
performed tricks (as a covariate, considered a proxy for risk-taking
behavior). Characteristics of the fall that were considered as co-
variates included the subject’s reported inability to stop just be-
fore injury and the severity of injury. A fracture, a dislocation, or
an internal injury constituted a major injury; a laceration, abra-
sion, contusion, sprain, or strain was a minor injury.
We evaluated the possibility that selection bias might result
from the use of controls who also were injured while skating. For
example, many subjects treated as case patients in the analysis of
wrist injury were used as controls for the analysis of elbow injury.
If nonuse of wrist guards was highly correlated with nonuse of
elbow pads, then these subjects might be less likely than the gen-
eral population to wear gear and have protection. Therefore, sep-
arate covariates were defined for each type of gear used as well as
for a composite variable indicating the use or nonuse of any ad-
ditional safety gear not related to the injury site.
Statistical Analysis
All data reported have been weighted according to the proba-
bility of hospital selection from the four levels based on hospital
size in the total NEISS sample. All analyses were conducted with
SUDAAN statistical software to account for complex sampling.
11
T
ABLE
3.
S
ELECTED
C
HARACTERISTICS
OF
THE
I
N
-L
INE
S
KATERS
WITH
W
RIST
OR
E
LBOW
I
NJURIES
AND
T
HEIR
C
ONTROLS
.*
C
HARACTERISTIC
W
RIST
R
ISK
G
ROUP
E
LBOW
R
ISK
G
ROUP
CASE
PATIENTS
(
N

2471)
CONTROLS
(
N

2933)
P
VALUE
CASE
PATIENTS
(
N

1724)
CONTROLS
(
N

2984)
P
VALUE
no. (%) no. (%)
Age group
Elementary school
Junior or senior high school
Adult
1357 (55)
558 (23)
557 (23)
696 (24)
608 (21)
1629 (56)
0.002
765 (44)
377 (22)
582 (34)
1149 (39)
643 (22)
1192 (40)
0.83
Sex
Male
Female
993 (40)
1478 (60)
1638 (56)
1295 (44)
0.14
728 (42)
996 (58)
1783 (60)
1201 (40)
0.13
Dominant hand†
Right
Left
2100 (86)
337 (14)
2711 (95)
137 (5)
0.08
1492 (94)
87 (6)
2676 (90)
291 (10)
ND‡
Ability level
Novice
Beginner
Intermediate
Expert
317 (13)
978 (40)
849 (34)
327 (13)
310 (11)
891 (30)
1181 (40)
551 (19)
0.75
188 (11)
574 (33)
687 (40)
275 (16)
249 (8)
1124 (38)
950 (32)
661 (22)
0.82
No. of times in-line skating
1–5
6–12
13–99

100
479 (19)
196 (8)
1013 (41)
783 (32)
764 (26)
421 (14)
573 (20)
1176 (40)
0.35
420 (24)
179 (10)
678 (39)
447 (26)
384 (13)
361 (12)
849 (28)
1390 (47)
0.70
Cross-training
No other sports
One or more other sports
188 (8)
2283 (92)
343 (12)
2590 (88)
0.45
120 (7)
1605 (93)
335 (11)
2649 (89)
ND‡
No. of lessons taken§
0
1–5

6
1346 (54)
799 (32)
327 (13)
1355 (47)
1218 (43)
283 (10)
0.57
496 (29)
824 (48)
404 (23)
1748 (60)
909 (31)
249 (9)
0.03
Performed tricks¶
Yes
No
300 (12)
2171 (88)
377 (13)
2513 (87)
0.60
69 (4)
1613 (96)
532 (18)
2452 (82)
0.05
Level of perceived exertion at time
of fall
Warm-up
Cruise
Fatigue
205 (8)
1949 (79)
317 (13)
214 (7)
2361 (81)
358 (12)
0.97
120 (7)
1383 (80)
222 (13)
256 (9)
2308 (77)
419 (14)
0.93
Fall related to difficulty stopping

Yes
No
455 (20)
1784 (80)
919 (32)
1945 (68)
0.27
585 (35)
1071 (65)
480 (17)
2315 (83)
0.08
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EFFECTIVENESS OF SAFETY GEAR IN PREVENTING INJURIES FROM IN-LINE SKATING
Volume 335 Number 22

1633
Log-linear chi-square tests were used to test for association be-
tween groups and for significant differences in proportions.
11,12
Association was assessed with unadjusted odds ratios and 95 per-
cent confidence intervals. Logistic regression was used to com-
pute adjusted odds ratios with control for confounding factors.
Population-attributable risks were calculated with established
methods.
13
A P value of less than 0.05 (two-tailed) was consid-
ered to indicate statistical significance, with the use of variances
derived from the weighted sample.
RESULTS
Demographic Characteristics of the Skaters
and Circumstances of the Injuries
We interviewed 161 of 206 eligible subjects (for a
78 percent response rate
14
); their data were weight-
ed, on the basis of hospital selection, so as to repre-
sent the distribution of characteristics of the estimat-
ed 6331 in-line skating injuries treated in emergency
departments nationally during the study period. The
skaters ranged from 6 to 59 years of age (mean, 20.8;
median, 15). Forty-eight percent were male, and 89
percent were right-handed (other characteristics of
the skaters are provided in Table 1; data on their falls
and consequent trauma are provided in Table 2). The
most typical fall involved young novice or beginner
skaters wearing little or no safety gear, who either
spontaneously lost their balance while skating out-
doors or fell after striking a road defect or debris.
The falls typically occurred on outstretched arms
without any attempt to stop. The wrist was the most
common site of primary injury (32 percent); 25 per-
*The values given are calculated for two subgroups of the estimated national sample of 6331 injured in-line skaters:
5404 case patients and controls in the wrist risk group and 4708 case patients and controls in the elbow risk group.
Values are based on weighted data from 141 interviewed subjects in the wrist risk group and 122 interviewed subjects in
the elbow risk group. The values shown do not include subjects for whom data on a given variable were missing. For
categories within each variable, the values may not add up to the totals in the estimated national samples (N values)
because of rounding involved in the estimating process or missing data (see below). P values are for the comparisons of
case patients and controls by the log-linear chi-square test. Because of rounding, percentages may not total 100. ND
denotes not determinable.
†An additional 85 subjects in the wrist risk group and 85 in the elbow risk group were ambidextrous, and data on
handedness were missing for an additional 34 in the wrist risk group and 77 in the elbow risk group. The subjects were
not included in the analysis of handedness.
‡The small number of left-handed subjects precluded chi-square analysis.
§Data were missing for an additional 77 subjects in the wrist risk group and 77 in the elbow risk group; they were not
included in this analysis.
¶Data were missing for an additional 43 subjects in the wrist risk group and 43 in the elbow risk group; they were not
included in this analysis.

Data were missing for an additional 301 subjects in the wrist risk group and 258 in the elbow risk group; they were
not included in this analysis.
**Data were missing for an additional 17 subjects in the wrist risk group and 18 in the elbow risk group; they were
not included in this analysis.
††Data were missing for an additional 34 subjects in the wrist risk group and 34 in the elbow risk group; they were
not included in this analysis.
‡‡“Additional gear” refers to safety gear intended to protect anatomical sites other than the site by which the risk
group was defined (e.g., the use of both wrist guards and elbow pads in the wrist risk group).
T
ABLE
3.
C
ONTINUED
.
C
HARACTERISTIC
W
RIST
R
ISK
G
ROUP
E
LBOW
R
ISK
G
ROUP
CASE
PATIENTS
(
N

2471)
CONTROLS
(
N 2933)
P
VALUE
CASE
PATIENTS
(N 1724)
CONTROLS
(N 2984)
P
VALUE
no. (%) no. (%)
Wrist guards worn at time of fall
Yes
No
154 (6)
2317 (94)
1356 (46)
1577 (54)
0.001
446 (26)
1278 (74)
755 (25)
2229 (75)
0.96
Elbow pads worn at time of fall**
Yes
No
360 (15)
2094 (85)
1058 (36)
1875 (64)
0.03
111 (6)
1613 (94)
1056 (36)
1910 (64)
0.003
Knee pads worn at time of fall††
Yes
No
780 (32)
1657 (68)
1495 (51)
1438 (49)
0.05
652 (39)
1038 (61)
1305 (44)
1679 (56)
0.66
Helmet worn at time of fall
Yes
No
403 (16)
2069 (84)
499 (17)
2434 (83)
0.93
336 (19)
1388 (81)
420 (14)
2564 (86)
0.56
Additional gear worn at time
of fall‡‡
Yes
No
865 (35)
1606 (65)
1563 (53)
1370 (47)
0.06
720 (42)
1004 (58)
1399 (47)
1585 (53)
0.66
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1634  November 28, 1996
The New England Journal of Medicine
cent of all injuries were wrist fractures. Seven percent
of the injured skaters wore all four types of safety
gear; 46 percent wore none. Of the total, 45 percent
wore knee pads, 33 percent wrist guards, 28 percent
elbow pads, and 20 percent helmets.
The Case–Control Study
Case patients and controls in the wrist risk group
and in the elbow risk group are compared in Table
3. The projected national total in the wrist risk
group (5404 persons) was estimated on the basis of
weighted data on 141 interviewed subjects; the pro-
jected total in the elbow risk group (4708) was es-
timated on the basis of 122 subjects. Case patients
and controls in the wrist group differed significantly
in age distribution (case patients tended to be young-
er) and in their use of wrist guards and elbow pads.
Case patients and controls in the elbow group dif-
fered only in their use of elbow pads, the number of
lessons taken (case patients tended to have taken
more lessons), and history of trick skating (controls
had more frequently performed tricks).
Analysis of crude odds ratios indicated that among
those at risk for wrist injury, skaters who did not
wear wrist guards had a likelihood of actually sus-
taining a wrist injury that was 12.9 times that among
those who did wear wrist guards (95 percent confi-
dence interval, 4.5 to 37.1) (Table 4). Among skat-
ers at risk for injury to the elbow, those not wearing
elbow pads had a risk of sustaining an elbow injury
that was 8.0 times that among skaters who did wear
such gear (95 percent confidence interval, 2.1 to
30.1). Nonuse of knee pads was associated with an
increase, but not a significant increase, in the risk of
knee injury (crude odds ratio, 2.2; 95 percent con-
fidence interval, 0.7 to 7.2). The association be-
tween not using a helmet and sustaining a head or
facial injury was also not significant (odds ratio, 0.9;
95 percent confidence interval, 0.1 to 6.8).
Bivariate analysis showed a significant association
between the likelihood of wrist injury and both the
use of wrist guards and age and an association be-
tween the likelihood of elbow injury and the use of
elbow pads, the taking of lessons, and a history of
doing tricks (for all associations, P0.05). The rela-
tion between wrist injury and the use of wrist guards
was confounded by age and sex; the relation be-
tween elbow injury and the use of elbow pads was
confounded by having taken lessons and a history of
performing tricks. When we controlled for these
confounders, the multivariate analysis indicated that
the nonuse of wrist guards was associated with a risk
of sustaining a wrist injury that was 10.4 times that
among skaters who did wear wrist guards (95 per-
cent confidence interval, 2.9 to 36.9), and nonuse
of elbow pads was associated with an odds ratio of
9.5 for sustaining an elbow injury (95 percent con-
fidence interval, 2.6 to 34.4) (Table 4). The use of
wrist guards was not significantly associated with in-
jury to the elbow (data not shown).
In calculations of population-attributable risk, the
nonuse of wrist guards accounted for 87 percent (95
percent confidence interval, 84 to 96 percent) of all
wrist injuries. Failure to use elbow pads accounted
for 82 percent (95 percent confidence interval, 78
to 95 percent) of all elbow injuries. Failure to use
knee pads accounted for 32 percent (95 percent
confidence interval, 27 to 79 percent) of all knee in-
juries.
DISCUSSION
Our analysis of several environmental and behav-
ioral risk factors for in-line skating injuries in a na-
tionally representative sample of skaters found that
wrist guards and elbow pads afforded skaters a high
level of protection, but that their rate of use among
injured patients was relatively low. The degree of
protection afforded by wrist guards and elbow pads
is similar to the degree of protection afforded the
head by bicycle helmets (85 percent) in a study of
bicycle crashes.
15
The NEISS data set permits the estimation of the
national incidence of an injury with known vari-
ance.
9
Even using unweighted data (thereby convert-
ing the probability sample to a sample of conven-
ience), we found that the adjusted odds ratio for
wrist injuries associated with the failure to use wrist
guards was 5.9 (95 percent confidence interval, 1.8
to 18.8), and that for elbow injuries associated with
the failure to use elbow pads, 7.9 (95 percent confi-
dence interval, 2.2 to 27.5). To bolster the strength
of our analysis, we used a single interviewer and
multiple lines of inquiry, sought parental confirma-
tion for important data, controlled the analysis for
many potential confounders, sampled a wide age
range, sought (and achieved) a high response rate,
and increased precision by restricting the selection
of case and control patients to those exposed to the
risk of injury to a specific anatomical site.
Our study, however, has several potential limita-
*Odds ratios are for subjects not wearing appropriate gear as compared
with those who were wearing it. CI denotes confidence interval.
†Odds ratios for wrist injury have been adjusted for age group and sex.
Odds ratios for elbow injury have been adjusted for the number of lessons
taken and whether or not the subject performed tricks.
TABLE 4. ODDS RATIOS FOR INJURIES TO IN-LINE SKATERS
NOT WEARING APPROPRIATE SAFETY GEAR.*
SITE OF INJURY
CRUDE
ODDS RATIO
(95% CI)
A
DJUSTED
ODDS RATIO
(95% CI)†
Wrist: wrist guards not worn 12.9 (4.5–37.1) 10.4 (2.9–36.9)
Elbow: elbow pads not worn 8.0 (2.1–30.1) 9.5 (2.6–34.4)
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EFFECTIVENESS OF SAFETY GEAR IN PREVENTING INJURIES FROM IN-LINE SKATING
Volume 335 Number 22  1635
tions. Selection bias may have resulted from our use
of emergency department patients as controls, rather
than skaters drawn from the general population.
Controls who have sustained a skating injury may be
more similar to case patients than population-based
controls would be, which would have biased our re-
sults toward the null hypothesis. However, any po-
tential bias of this type would not have altered the
public health consequences of our findings because
the point estimates of the odds ratios are so large.
On the other hand, had a significant correlation
existed among the use of different kinds of safety
gear, our results might have been biased away from
the null hypothesis. The use of more than one type
of gear was not a significant confounder, either when
use of a given type was examined individually or when
we assessed a composite indicator (data not shown).
Forcing these variables for use of more than one
type of gear into the final model decreased the point
estimate of the odds ratio for wrist injury minimally
and increased the odds ratio for elbow injury sub-
stantially, but it did not change the significance of
these ratios. However, the level of precision was re-
duced considerably (data not shown). To recruit
geographically matched, population-based controls
would have been prohibitively costly; controls from
a single area only might not have had attributes
(e.g., skill level) that properly matched those of the
case patients; and seeking to select controls from a
random national telephone survey might not have,
in 1993, yielded many in-line skaters.
Information bias may be present because these data
were reported by the skaters themselves. The recall
period ranged from several weeks to eight months,
and some respondents may not have remembered de-
tails well. Some variables, such as skating frequency,
were difficult for the youngest children to quantify.
Lifetime person-hours of skating experience, the ideal
measure of exposure to possible injury, was crudely
approximated by the number of times a subject re-
membered having skated. This number may not have
been recalled accurately. The study lacked sufficient
power to detect a significant association between
knee injury and the use of knee pads (the point esti-
mate, however, was elevated) as well as between head
injury and the use of a helmet. Some potential con-
founders could not be assessed, including skating
speed, crash forces on impact, cross-training experi-
ence with cross-country skiing, the use of poorly fit-
ting safety gear, and household income.
The nature of in-line skating has some practical
implications for the use of safety gear. The wide-
spread availability of gear in child and adult sizes and
its relatively low cost should facilitate use. Automatic
braking devices, which slow the wheels or apply a
heel brake without dorsiflexion of the foot, may re-
duce the injury rate; such devices became available
after the conclusion of the study. Currently, wrist
guards may not be practical for participants in roller
hockey because the wrist guards interfere with the
player’s ability to hold the hockey stick firmly or
make a wrist shot. This limitation warrants further
attention on the part of product designers, given the
popularity of roller hockey and the large proportion
of the skaters in our study who were injured while
playing hockey.
In conclusion, we recommend that in-line skaters
wear wrist guards, elbow pads, knee pads, and hel-
mets. Although the small number of skaters who
sustained a head injury did not allow us to deter-
mine the degree of protection afforded by helmets,
other studies
15,16
indicate that helmets that meet ex-
isting standards for bicycle helmets
17
are strongly
protective against head injuries in physical environ-
ments quite similar to that of skaters.
We are indebted to the NEISS coding nosologists from each hospi-
tal, who retrieved the information needed to contact injured persons;
to the adult skaters, parents, and children who permitted interviews;
and to Marcie-jo Kresnow, M.S. (National Center for Injury Pre-
vention and Control) and instructors Tammy Kesting and Liz Mil-
ler for their assistance in developing the questionnaire.
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Copyright © 1996 Massachusetts Medical Society. All rights reserved.