Significance of Absent Ankle Pulse

The inability to detect the pulsation of the posterior tibial artery behind the internal malleolus, or of the dorsalis pedis artery, is widely used as an important physical sign. In the patient with symptoms or signs of ischaemia of the foot, the absence of pulses is regarded as highly significant. On the other hand, the incidental discovery of an impalpable ankle pulse in a patient who does not present with an ischaemic foot is given widely varying interpretations by different clinicians. The finding may be dismissed as an observer error. The anatomical course of the artery may be thought to be anomalous. In older age-groups the absent pulse may be regarded as merely evidence of ageing, or it may be taken as a sign of atherosclerosis. Several widely quoted studies have been undertaken to estimate the proportion of impalpable ankle pulses in normal subjects (Kramer, 1933; Morrison, 1933; Reich, 1934; Silverman, 1946). The dorsalis pedis pulse is held to be impalpable in from 0% (Kramer, 1933) to 12.4% (Silverman, 1946) of normal limbs, and the posterior tibial pulse in from 2.8% (Silverman, 1946) to 12.8% (Morrison, 1933). The dorsalis pedis pulse is said to be misplaced in 8% of limbs (Reich, 1934). It has been stated that the peroneal artery replaces the posterior tibial in 5% of cases (Aird, 1957). Perusal of the details of these studies suggests reasons for these wide divergencies of opinion. The " normal " subjects are variously diabetics (Kramer, 1933), males with an average age of 20 years (Silverman, 1946), or healthy people of unspecified age (Reich, 1934) or of unspecified sex in the different age-groups (Morrison, 1933). In each study there seems to have been but a single observer, and when large numbers of subjects are examined in a short time-for example, Silverman (1946)-the question is raised of what constitutes an impalpable pulse. The implication of the differing subjective and objective interpretations of the impalpable ankle pulse in subjects without other evidence of atherosclerosis or ischaemic disease of the foot is that in our present state of knowledge no significance at all can be assigned to the finding. We set out to re-examine the question of impalpable ankle pulses in " normal "' subjects with certain objects in view. We hoped to arrive at some estimate of the observer error, at least between trained observers, and to redetermine the frequency of impalpable pulses in different age-and-sex groups. We sought also to determine with what degree of certainty the apparent absence of an ankle pulse could be taken as evidence of arterial disease. Method