E.J. MacKenzie, M.J. Bosse, and the LEAP Study Team reply

Abstract

To The Editor: Recently my attention was directed to the article “Functional Outcomes Following Trauma-Related Lower-Extremity Amputation” (2004;86:1636-45, 2503), by MacKenzie et al. This multicenter study included a monumental mass of data and imparts valuable information about the psychological impact of traumatic amputations, but the authors also offered two major, unsupported conclusions. First, the outcome of above-the-knee amputations was presented as superior to those of below-the-knee amputations, but this conclusion is contradicted by other data. The SIP (Sickness Impact Profile) scores showed that the outcomes of the above-the-knee amputations equaled or exceeded those of the below-the-knee amputations. This interpretation, however, is refuted by a statement in the text that “none of the differences... was significant at the p < 0.05 level.” Another contradiction is found in the statement: “the walking speed of the patients with a below-the-knee amputation was significantly faster than that of the patients with an above-the-knee amputation.” Sixty-two percent of the patients with a below-the-knee amputation had a walking speed equal to or faster than 4 ft/sec compared with 43.5% of those with an above-the-knee amputation, and 23.1% of those with an above-the-knee amputation were unable to walk independently over uneven ground compared with 11.3% of those with a below-the-knee amputation. The statistical significance of the findings is challenged by the threefold difference between the number of subjects with an above-the-knee amputation (thirty-four) and the number with a below-the-knee amputation (109). Also, failure to identify the age distribution in each group introduces the high probability that nonmatched groups, particularly in reference to patients with an above-the-knee amputation, were being … Corresponding author: Ellen J. MacKenzie, PhD Center for Injury Research and Policy Johns Hopkins Bloomberg School of Public Health 624 North Broadway, Room 554 Baltimore, MD 21205 emackenz{at}jhsph.edu