A comparative analysis of several crutch-length-estimation techniques

The purpose of this study was to determine which of several crutch-fitting techniques best predicts ideal crutch length. One hundred seven active-duty military volunteers were measured for crutches using each of the following methods: (1) axillary fold to heel in the supine position, (2) olecranon to opposite third fingertip, (3) olecranon to opposite fifth fingertip, (4) 77% of height, (5) height minus 16 in (40.6 cm), (6) 77% of arm span, and (7) arm span minus 16 in (40.6 cm). The subject's self-reported heights and their actual measured heights were both used in calculations involving height. Ideal crutch length was determined by an experienced orthopedic physical therapist, with placement of the axillary pad 2.5 in (6.4 cm) below the axillary fold. Mean squared error indices were then computed as the average of the squared deviations of the technique measurements from the ideal crutch length. Of the techniques studied, the two involving minor arithmetical adjustments to the subjects' self-reported height were found to be good predictors: 77% of height and height minus 16 in (40.6 cm). The poorest predictor was axilla to heel in the supine position. Finally, two additional length estimates were derived using linear regression analyses. These estimates provided the best overall predictions based on actual height and reported height. A quick-reference table for crutch-length estimates based on patient heights was developed from these regression results.