Relationship between ligamentous laxity and the site of upper extremity fractures in children: Extension supracondylar fracture versus distal forearmfracture

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 hypere xtension, (b) knee hyperextension, (c) the ability to touch the thumb to th e ipsilateral forearm, and (d) the ability to extend the thumb past the uln ar 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 ave raged 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 grou p 2 (19%) could touch the thumb to the ipsilateral forearm (P < 0.001). Twe nty-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 ligam entous laxity is more likely to sustain an extension supracondylar humerus fracture than a distal forearm fracture when he or she falls on the outstre tched hand to break the force of the fall.