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G.R. Webb replies:I would like to thank Dr. Kumar for his interest in our study and for
raising several important questions. The first issue raised is the explanation
for the higher failure rate in the long-arm cast group. As stated in the
paper, this result was unexpected. Dr. Kumar suggests that this may be related
to the fact that a larger number of the fractures treated in long arm casts
involved both the radius and ulna. As seen in Figure 3, there was no
significant difference in the distribution of fracture types when they were
looked at individually. However, it does appear that when grouped by fractures
of the radius only compared with fractures of both bones, there is an uneven
distribution (twenty-six short arm and thirty-eight long arm casts). When all
fractures involving both bones are considered, these accounted for twenty-six
(49%) of the fifty-three short arm casts and thirty-eight (63%) of the sixty
long arm casts. Of the twenty-six fractures of both bones treated in short arm
casts, only one (4%) failed. Of the thirty-eight treated in long arm casts,
seven (18%) failed. If the uneven distribution were the only explanation for
the greater number of failures seen in the long-arm cast group, the total
number of failures would be larger, but the rate of failure should be similar
between the cast groups. Examining all eleven failures, eight involved
fractures of both bones, whereas six were complete fractures. It does appear
that instability may be more closely related to the involvement of both bones
than to the amount of initial displacement.