Relationship between ligamentous laxity and the site of upper extremity fractures in children: extension supracondylar fracture versus distal forearm fracture.

Eighty children who had fallen on an outstretched hand and sustained either a displaced supracondylar fracture (group 1) or a displaced distal forearm fracture (group 2) were prospectively studied. Ligamentous laxity in these 80 patients was determined by four methods: (a) contralateral elbow hyperextension, (b) knee hyperextension, (c) the ability to touch the thumb to the ipsilateral forearm, and (d) the ability to extend the thumb past the ulnar border of the clenched fist. Elbow hyperextension averaged 10.5 degrees in group 1 and 4.4 degrees in group 2 (P < 0.0001). Knee hyperextension averaged 7.2 degrees in group 1 and 2.4 degrees in group 2 (P < 0.001). Twenty-one of 38 patients in group 1 (55%) compared with 8 of 42 patients in group 2 (19%) could touch the thumb to the ipsilateral forearm (P < 0.001). Twenty-seven of 38 patients in group 1 (71%) compared with 5 of 42 patients in group 2 (12%) could extend the thumb past the ulnar border of the clenched fist (P < 0.001). The authors conclude that a child who demonstrates ligamentous laxity is more likely to sustain an extension supracondylar humerus fracture than a distal forearm fracture when he or she falls on the outstretched hand to break the force of the fall.