1. This survey describes a series of 3,000 fractures and major soft-tissue injuries resulting from parachute jumping, with particular reference to the traumatic mechanisms involved.
2. Almost all injuries involve weight-bearing structures. The distribution and patterns of injury are generally similar to those encountered in civilian orthopaedic practice; yet there are certain minor statistical differences which are related to the peculiar stresses of parachue jumping. No injury is specific enough to be called a typical parachute lesion.
3. Almost all the injuries of parachute jumping can be attributed to four basic traumatic mechanisms:
(a) Torsion puts landing thrust. This is by far the most common mechanism of injury and is responsible for a chain of related injuries, extending from the toes to the hip.
(b) Backward landing. Vertebral compression fractures and head injuries characterize this mechanism of injury.
(c) "Opening shock" is a mechanism of injury peculiar to parachute jumping. The violent abduction stress causes many ligamentous tears and even fractures of the extremities.
(d) Violent vertical landings. Occasional parachute malfunctions increase the landing impact and cause severe multiple fractures of the legs and spine.
4. One-half of all parachute fractures involve the ankle mortise. Various authors report essentially the same statistical distribution of fractures as in the present study, although the source of the patients and the circumstances of injury are all different. The most prevalent mechanism of injury is external rotation which, together with abduction, accounts for approximately 75 per cent, of fractures at the ankle.
5. The entire lower extremity shows a preponderance of external-rotation injuries. This would imply a structural weakness of the limb as a whole,—a lack of adaptive resiliency to the stress of external torsion.
6. A classification of fractures based on etiological stresses is much more reasonable and useful than one based on anatomical location. Recognition of the etiological stresses not only relates apparently dissimilar fracture patterns, but also provides a rational approach to treatment.