、。
I went skiing and broke my leg.
Literal
Ski [obj-を] did-[when-たら], leg [obj-を] broke-bone [explanation-んだ].
したら here is the temporal-discovery conditional 'when I did X, (it turned out) Y' — one of the key uses of ~たら distinct from pure hypothetical. 骨折する '(to) fracture / break a bone' is a sinitic compound verb. 足を骨折する 'to break a leg' is the standard way to say it — compare English, which says 'broke my leg' using the anatomic noun directly.