Breadth of base whilst walking: effect of ageing and parkinsonism - United Kingdom

Age and Ageing, Jan, 1998 by Andre Charlett, Clive Weller, Andrew G. Purkiss, Sylvia M. Dobbs, R. John Dobbs

Introduction

Falls occur primarily during activity [1-4]: walking is essentially an unstable condition [4, 5]. The centre of gravity projects outside the base of support for most of the gait cycle [4], the breadth of base, position of the centre of gravity and its distance from the base being critical to stability [6]. But just how good is our clinical judgement of what constitutes a normal breadth of base or, indeed, the gait of normal ageing? Clinical opinion is that the "characteristic type of gait in old age" has a "slight widening of the base" [7], "the gait of the elderly...is frequently wide-based" [6] and walking in "a classical wide-based manner...can reasonably be attributed to age rather than to current disease" [8]. Assuming that the swing paths are parallel to the line of progression, foot separation in the coronal plane can readily be estimated by monitoring foot/ground contact using talcum power or in a fixed gait laboratory. The `pocket gait laboratory' [9] gives foot separation as one foot passes the other. Alternatively, the relative position of the `tagged' left and right feet can be sampled during the cycle. Reference ranges are presented, by which the `unusualness' [10] of foot separation at mid-swing can be assessed in relation to personal characteristics. The gait of sufferers from idiopathic parkinsonism is characterized by comparison.

Subjects and methods

The 164 healthy volunteers (at least 12 men and 12 women from each decade, 30-89 years) were Caucasian, living independently and able to walk for over 40 m or 60 s, without fatigue, dyspnoea, angina, claudication or musculoskeletal pain. They did not normally use a walking aid. There was no history of parkinsonism or other specific neurological or musculoskeletal disorder. Those with a mental test score [is less than or equal to] 8 on tthe 16-point Modified Tooting Bec scale [11] or with clinical depression or other mental illness were excluded, as were those with overt abnormalities of spine, lower limbs or posture--e.g, isolated findings of a `walking stick posture' (see below), previous orthopaedic surgery to spine or lower limbs or pain in relevant joints.

Ninety-nine volunteers with idiopathic parkinsonism (up to a maximum of 12 men and 12 women in each decade between 40 and 89 years) were also recruited. Parkinsonism had been diagnosed by the presence of two or more cardinal signs: brady/hypokinesia, 'resting' rigidity, tremor and postural abnormality. There was evidence of at least three of the UK Brain Bank supportive criteria [12] for diagnosis of definite Parkinson's disease. Clear-cut, non-idiopathic parkinsonism was excluded [12, 13], as were patients in whom there were reservations about the idiopathic nature (e.g. where arteriosclerotic pseudoparkinsonism was suspected of coexisting with idiopathic [14]). All were independently mobile and without orthostatic symptoms. Those with other physical or mental disorders that might affect assessment (as above) were excluded. All but six were receiving antiparkinsonian medication. Those whose performance fluctuated in relation to individual doses were assessed in their `therapeutic window', i.e. the period in the dosage interval when optimal effects of medication occur.

All gave informed consent to participate in the study, which had local ethics committee approval.

Assessments were as follows:

1. Mid-heel separation at mid-swing was measured over 40 m or 60 s, in a 2.5-m-wide empty corridor, using the computerized, pocket-sized, infrared telemetric `shoestring' device [15]. Rested subjects walked `at their own speed', following the command "go".

2. Physiological postural correction--body sway, standing at ease with shoes on and eyes open--was measured as total angular movement in the sagittal plane [16], during three consecutive 1 min periods.

3. Anatomical postural abnormality in parkinsonism was assessed by measuring forward displacement [17] of occiput, with knees extended and buttocks and heels against a wall, but otherwise standing at ease (scoring: [is less than or equal to] 10.2cm, 0; [is greater than] 10.212.7cm, 1; [is greater than] 12.7-15.3 cm, 2; [is greater than] 15.3cm, 3).

5. Rigidity in parkinsonism: resting mid-line rigidity [17] was rated (scoring: none detectable in neck, 0; detectable, 1; moderate, 2; severe, 3).

6. Functional impairment in parkinsonism was assessed using the Hoehn and Yahr staging (stage I representing unilateral involvement with minimal or no functional impairment and stages II to IV increasing incapacity, with the first signs of impaired righting reflexes--evident in unsteadiness as the patient turns or demonstrated when he or she is pushed from standing equilibrium with feet together and eyes closed--appearing at stage III) [18].

7. Cognitive inefficiency was measured using the time required to lift the left or right index finger in response to visual signals. An alerting signal did or did not warn the subject in advance whether the imperative signal would be to lift the left or right index. A practice of four replicates of the four combinations (from random permuted blocks) preceded the test proper (15 replicates). A fixed delay of 2 s was used between alerting and imperative signals. The smaller the ratio of unwarned to warned reaction time (i.e. the lesser the ability to make use of a warning), the more inefficient the cognitive processing [19].