Computerized Dynamic Posturography in the Objective Assessment of Balance in Patients With Intermittent Claudication

Computerized Dynamic Posturography in the Objective Assessment of Balance in Patients With Intermittent Claudication Katherine A. Mockford,1 Fayyaz A.K. Mazari,1 Alastair R. Jordan,2 Natalie Vanicek,2 Ian C. Chetter,1 and Patrick A. Coughlin,1 Hull, United Kingdom

One-third of all elderly patients fall each year and impaired balance has been recognized as a specific risk factor. Intermittent claudication is common among the elderly population, affecting approximately 5% of the population over the age of 50. The aim of this proof-of-concept study was to assess the prevalence of impaired balance among elderly claudicants and to assess each patient’s insight into their own risk of falling. A total of 58 claudicants (45 men), median age of 70 (interquartile range ¼ 65-73) years, underwent objective balance assessment by using computerized dynamic posturography. As compared with 195 (5%) historic controls, 24 (41%) of the claudicants demonstrated abnormal balance when the Sensory Organization Test (SOT) was used. Vestibular dysfunction occurred in 52% of the claudicants. Abnormalities including somatosensory (22%), visual function (17%), and preferential reliance on inaccurate visual cues (17%) occurred less often. Prolonged Motor Control Test latency times were uncommon (n ¼ 13) and were in most cases evenly distributed between those with normal (n ¼ 7) and abnormal (n ¼ 6) composite SOT scores. There was a significant difference in history of falling between claudicants with abnormal and normal SOT scores ( p ¼ 0.003), with a higher number of patients with abnormal SOT having experienced falling in the past year. However, no correlation between fear of falling and composite SOT score was found (Spearman rank correlation, r ¼ 0.124; p ¼ 0.381). Impaired balance, particularly secondary to vestibular problems, is very common among claudicants and may predispose to a high incidence of falls. Claudicants with abnormal balance are more likely to have a history of falls but not a fear of falling, thus potentially rendering these patients to be at a greater risk.

INTRODUCTION Improving functional outcomes of older, high-risk populations is of enormous public health importance, in terms of both high social and economic value. The act of falling is extremely common, affecting one in

1 Academic Vascular Surgical Unit, Hull Royal Infirmary, Hull, United Kingdom. 2 Department of Sport, Health and Exercise Science, University of Hull, United Kingdom.

Correspondence to: Katherine A. Mockford, MBChB, Academic Vascular Surgical Unit, Vascular Laboratory, Alderson House, Hull Royal Infirmary, Hull HU3 2JZ, United Kingdom, E-mail: [email protected] Ann Vasc Surg 2011; 25: 182-190 DOI: 10.1016/j.avsg.2010.07.021 Ó Annals of Vascular Surgery Inc. Published online: October 4, 2010

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three adults aged over 65 each year, with a maximum of 20% of falls causing serious injury.1 In 2000, the cost for nonfatal falls in the United States was $19 billion dollars.1 The significant burden of falls is well recognized and prevention strategies have been devised, such as incorporating the need for identification, assessment, and prevention measures for those who are at a high risk of falling.2 A recent review on the success of fall-prevention strategies reported varying degrees of success.3 Exercise alone is effective in reducing the number of falls and it has been recommended that muscle strengthening, balance, and endurance training should be incorporated into prevention strategies.3 Therefore, the identification of patient groups with poor lower limb function, especially those with impaired balance, might be of importance in targeting patients who are at a high risk of falling.

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Intermittent claudication is a common condition, with a prevalence of >5% in patients aged >50 years, increasing with age.4 Frailty5 and functional morbidity are prevalent6 among elderly patients with atherosclerosis and peripheral arterial disease.7 However, the association between intermittent claudication, impaired balance, and the risk of falling is equivocal.8-11 Although Gardner and Montgomery8 reported a higher risk of falling among claudicants, there are others who have found no association between peripheral arterial disease (PAD) and the risk of falling.9,10 Computerized dynamic posturography (CDP) is an established test of postural stability12 which incorporates both sensory and motor testing. The aims of this study were to objectively assess the prevalence of balance impairment among elderly patients with intermittent claudication in comparison with the NeuroCom normative database of controls, with 5% of them having abnormal balance. Further, we investigate potential explanations for poor balance. In addition, the relationship between balance abnormality and a risk of falling was explored to determine whether the screening for risk of falling should be carried out among elderly claudicants.

PATIENTS AND METHODS Study Design Patients were recruited into the study, following informed written consent, from the vascular outpatient clinic. All subjects lived independently in the local community, without any assistance. Patients were confirmed by the referring consultant as claudicants during clinical assessment at the outpatient clinic before recruitment into the study. Inclusion criteria included being able to speak English and the ability to comply with simple study protocol instructions. Exclusion criteria included the inability to safely perform balance-testing as determined by either the referring consultant or study doctor (e.g., coexisting neurological or limiting cardio-respiratory or other significant medical problems). This study was approved by the local research and ethics committee, the NHS trust, and University departments of research and development.

Patient Examination A complete medical history from each patient was obtained and medical examination, including neurological and visual (VIS) acuity assessment, was conducted for all the subjects. The ankleebrachial

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pressure index (ABPI) at rest was calculated for all the patients. Patients underwent a standardized treadmill test of 10 inclination at a speed of 1.6 mph to calculate the following: intermittent claudication distance, the speed at which patients experienced the onset of pain, maximum walking distance, and when they could walk no further. Post-exercise ABPI was calculated for each patient after treadmill testing.

History of Falling History of falling within the past year was documented. Falling was defined as the act of unintentionally coming to the ground or to another lower level, and not as a result of an overwhelming hazard that would normally result in a fall in the younger population.7 Patients were questioned about their history of falling at each clinical assessment. Assessment of Balance CDP was undertaken by using the EquiTest (NeuroCom International Inc., Clackamas, OR) system. This comprises a standing platform with dual force plates that can be rotated to tip the patient forward and backward (termed as sway-referenced support), or in some cases the force plates can be translated to move the patient toward either an anterior or a posterior direction. The patient’s feet are centered on the force plates and he/she is made to wear a safety harness and then face a brightly colored visual surround that is capable of moving relative to the patient (termed as sway-referenced surround). Data were collected and analyzed using NeuroCom international software (NeuroCom System Version 8.1.0., 1996-2006, NeuroCom International Inc., Clackamas, OR). Previous reports have shown that CDP is a valid and valuable test for the assessment of chronic balance or dizziness disorders with high test-retest reliability.13,14 In this study, CDP included both the Sensory Organization Test (SOT) and the Motor Control Test (MCT).15 The Sensory Organization Test SOT assesses the ability of a patient to effectively use different sensory systems (somatosensory [SOM], visual, and vestibular [VEST]) to maintain balance during sensory conflict conditions. Sensory conflict situations are created by movement of the visual surroundings or support platform in response to the anterior posterior sway of the patient (calibrated sway referencing) with the patient’s eyes either kept open or closed. Patients with sensory dysfunction may lose their balance in response to disrupted

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Fig. 1. The six different conditions assessed during the Sensory Organization Test, used courtesy of NeuroCom International, Inc. In condition 1, the patient relies on visual, vestibular, and somatosensory inputs as indicated by the following symbols . Vision is absent when the subjects are asked to close their eyes (conditions 2 and 5). Sway referencing occurs

as the support surface (conditions 4, 5, and 6) or the surrounding (conditions 3 and 6) tilts in response to the anterior-posterior sway of the subject. During sway referencing, the concerned sensory inputs become incorrect and this is indicated by red relevant sensory symbols .

sensory information. They may either be unable to make effective use of their sensory systems or they may use inappropriate adaptive responses, which may result in the use of inaccurate senses.15 To identify functional impairment within each sensory system, different conditions were compared (Fig. 1). Each sensory condition was repeated three times (three trials) and the mean data per condition were used. The SOT is not designed to provide a specific diagnosis or site of lesion, but may indicate the ineffective or inappropriate use of a sensory system or a potential deficiency.16 The SOM score is a measure of the ability of the patient to use inputs from the SOM system or the support surface to maintain balance and it is calculated as a ratio of condition 2 to condition 1. The VIS score identifies the ability of the patient to use VIS inputs to maintain balance and it is calculated as a ratio of condition 4 to condition 1. The VEST score assesses the ability of the patient to use inputs from the VEST system to maintain balance and it is calculated as a ratio of condition 5 to condition 1. The preference score measures the degree to which a patient relies on VIS information to maintain balance even when the information is incorrect. This is calculated as the ratio of the summation of conditions 3 and 6

to the summation of conditions 2 and 5. NeuroCom software indicates the normality or abnormality of each of these sensory components, thereby suggesting that even with a normal composite score, one or more aspects of balance may be abnormal when compared with 95% of the age-matched historic control subjects with no previous history or symptoms of disequilibrium.16 The NeuroCom control data for SOT consists of 195 age-matched participants with no significant comorbidities and no balance problems. Among these control subjects, 5% were considered to have abnormal balance by the SOT. A normal subject can exhibit an anterior to posterior sway over a total range of 12.5 without losing balance.16 The equilibrium score for each trial was calculated by comparing the difference between the patient’s calculated maximum displacement and the theoretical maximum and it is expressed as a percentage, with a score of 100 representing perfect stability and a score of 0 representing a fall. The composite equilibrium score is a measure of the overall performance in terms of postural stability during the test. It is calculated as a weighted average of the scores of all the six conditions tested and an abnormal result is identified when the calculated

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score is lower than the score of the 95% agematched control group.

The Motor Control Test For the MCT, the patient is made to stand on dual force plates that translate in either an anterior (forward) or posterior (backward) direction with increasing displacement of the centre of gravity of the subject. In response to this movement, the forces exerted by both legs on the support surface can be estimated independently. When all such forces are combined into a single point, they would be positioned at the ‘‘centre of force’’. The ‘‘centre of force’’ traces generated by each leg from the force plates are used to monitor the instantaneous level of muscular effort exerted around the ankle joint for each leg. These measurements are used to calculate onset times (latency) and response strengths of the active force automatically generated by the patients. Automatic postural responses are required to prevent falling after unexpected external disturbances to balance. Responses must be quick and well coordinated between both legs. The MCT assesses the automatic stabilizing response of a patient to, or the ability to recover from, an external perturbation and helps obtain the timing, strength, and symmetry of the force response from each leg relative to the stimulus. The timing of the force response is the latency period in milliseconds, before achieving a response from the leg. Prolonged latencies may be indicative of musculoskeletal or biomechanical abnormalities or pathology within peripheral nerves, spinal pathways, or brain structures. Similar to SOT, the MCT scores are compared with scores from age-matched historic control subjects, and are considered to be abnormal if they are below the fifth percentile. NeuroCom control data for the MCT used 111 age-matched participants with no significant comorbidities and no balance problems. Similar to SOT, 5% of these control participants were considered to have abnormal balance by the MCT. The MCT also measures amplitude scaling or response strength. This reflects the ability of the subject to prevent falling by counteracting the anterior-posterior sway induced by the force plate translation. The subject must generate approximately twice as much angular momentum in the direction opposite to the sway induced by the force plate translation to stop the induced sway and to bring the body’s centre of gravity back to equilibrium. Abnormal response strengths may be as a result of musculoskeletal problems or automatic response pathway abnormalities.16

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Fear of Falling This was assessed using the 16-item Activitiesspecific Balance Confidence (ABC) scale, which has been demonstrated to be a valid and reliable measure of fear of falling.17 Using a visual analogue scale, patients are asked to score 16 scenarios analyzing their level of confidence in performing tasks which may result in a fall. Each question is scored from 0 to 100, with a score 100 representing total confidence and a score of 0 representing no confidence at all. The total score is an average of all 16 responses. Scenarios range from ‘‘walking around the house’’ to the most difficult being ‘‘walking on an icy pavement’’. Statistical Analysis All analyses were performed using SPSS version 16 (SPSS, Chicago, IL). Correlation between fear of falling and composite SOT scores was performed using Spearman rank correlation. ManneWhitney U and Wilcoxon signed-rank tests were used to analyze continuous data and c2 test was used for categorical data. Significance was set at 0.05.

RESULTS Demographics In all, 58 elderly claudicants, 45 men and 13 women, median age 70 (interquartile range [IQR] ¼ 65-73) years, were studied. Demographic data and the clinical indicators of lower limb ischemia are presented in Table I, with no statistically significant differences between patients with normal or abnormal SOT results with respect to their comorbidities. There was a statistical difference between the two genders because female subjects had a higher preponderance of abnormal SOT results as compared with their male counterparts. The median age of male claudicants was comparable with females (71 and 69 years, respectively). In addition, there was a significant difference in walking distances between the normal and abnormal balance group, with shorter distances achieved among those with abnormal balance. However, there were no differences in ABPI results between the groups. SOT Results The SOT results for our group of claudicants are compared with historic, age-matched control groups (N ¼ 195) in Table II. The overall median composite equilibrium score for the claudicants was 70

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Table I. Characteristics of all patients who underwent balance testing All patients n ¼ 58

Patient characteristics Agea Number of male patients (%) Hypertensive On statin therapy Diabetes mellitus On insulin On oral hypoglycemics Diet controlled Smoker Current Ex Nonsmoker History of ischemic heart disease History of cerebrovascular disease CVA TIA History of lower limb osteoarthritis Previous TKR/THR/Hip# Indicators of lower limb ischemia PRWDc ICDc MWDc ABPI pre-exercise worst legd ABPI post-exercise worst legd Fear of falling ABC scored

Normal balance on SOT n ¼ 34 (59%)

Abnormal balance on SOT n ¼ 24 (41%)

p

70 45 41 43 15 4 10 1

(50-79) (78%) (71%) (74%) (26%) (7%) (17%) (1.7%)

70 31 26 26 8 3 6 0

(50-79) (91%) (76%) (60%) (24%) (9%) (18%)

69 14 15 17 7 1 4 1

(56-79) (58%) (63%) (71%) (29%) (4%) (17%) (4%)

NS 0.003b NS NS NS NS NS NS

16 32 8 16

(28%) (55%) (14%) (28%)

8 21 4 10

(24%) (62%) (12%) (29%)

8 11 4 6

(33%) (46%) (17%) (25%)

NS NS NS NS

3 5 16 3

(5%) (9%) (28%) (5%)

1 4 9 3

(3%) (12%) (26%) (9%)

2 1 7 0

(8%) (4%) (29%) (0%)

NS NS NS NS

(68-275) (21-69) (43-118) (0.59-0.91) (0.23-0.59)

NS 0.041b 0.026b NS NS

200 43 77 0.71 0.34

(135-400) (30-102) (53-215) (0.59-0.91) (0.21-0.69)

85% (67-96%)

253 49 99 0.72 0.37

(137-500) (35-111) (57-215) (0.59-0.93) (0.18-0.70)

90% (72-96%)

180 33 57 0.71 0.31

80% (36-94%)

NS

SOT, sensory organization test; NS, no significant difference between groups with normal and abnormal SOT scores; CVA, cerebrovascular accident; TIA, transient ischemic attack; TKR, total knee replacement; THR, total hip replacement; Hip#, hip fracture with surgical repair; PRWD, patient reported walking distance; ICD, intermittent claudication distance; MWD, maximum walking distance; ABPI, ankleebrachial pressure index; ABC, Activities-specific Balance Confidence scale. a Median value in years (range). b ManneWhitney U test demonstrated a significant difference between the normal balance group and the abnormal balance group with significance set at p < 0.05. c Median value in meters (interquartile range/IQR). d Median value (IQR).

(IQR ¼ 58-76). Within each age group, the median scores of the claudicants remained within the normal range (76, 68, and 70, respectively) because the lowest possible normal score for each age group is 70, 68, and 64, respectively. However, a higher percentage of claudicants had abnormal scores when compared with controls. Overall, 41% (n ¼ 24) of the claudicants demonstrated abnormal balance as compared with only 5% of the control group ( p  0.001, c2 test). The most frequently observed abnormal sensory component of balance was VEST dysfunction, which occurred in 30 (52%) claudicants. Abnormalities in other sensory components of balance were also found to be common, including SOM dysfunction (n ¼ 13, 22%), VIS dysfunction (n ¼ 10, 17%), and

preferential reliance on inaccurate visual cues (n ¼ 10, 17%). With relatively high scores, it was possible to obtain abnormal scores in one or more sensory domains but an overall normal composite SOT score. The percentage of claudicants with no abnormality at all was 40% (n ¼ 23). MCT Results The MCT was performed by 54 of the total 58 subjects. Four subjects requested to be excluded from the MCT as a result of fatigue after poor performance on the SOT. The median MCT latency in claudicants was 149 ms (IQR ¼ 140-159). In comparison with the historic age-matched controls (N ¼ 111), MCT latency was found to be normal

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Table II. Comparison of balance scores between claudicants and NeuroCom’s age-matched controls Controls Age group

Claudicants

<60 years 60-69 years 70-79 years

Numbers of patients 112 Median composite equilibrium 80 SOT score Percentage of patients with 5% abnormal SOT score

54 78

29 73

5%

5%

Total

<60 years

60-69 years 70-79 years Total

195 e

4 76

25 68

29 70

58 70

48%*

38%*

41%*

5% 25%

SOT, sensory organization test. *Claudicants vs. controls p  0.001, c2 test.

in 41 (76%) of the claudicants. There was no significant difference between the normal and abnormal SOT composite balance groups in terms of normal or abnormal MCT latency scores. Of the 13 patients with abnormal MCT latency scores, seven (54%) had normal SOT composite scores and six (46%) had abnormal scores. Abnormal amplitude scaling (response strength) was demonstrated by 23 of the 54 patients who underwent MCT. There was a significant difference in response strength between forward and backward force plate translations ( p < 0.001, Wilcoxon signed-ranks test). A total of 23 subjects (43%) during forward translations and three subjects (6%) during backward translations demonstrated abnormally poor response strength to either medium and/or large force plate translations. Only one patient demonstrated an abnormal response strength that was in excess of that expected, and this was during a backward force plate translation. Abnormal response strength to forward translations was not related to MCT latency outcome; 18 (78%) claudicants with abnormal response strength had normal MCT latency scores and among those subjects with normal response strength, 74% had normal latency scores (n ¼ 23).

Fear of Falling and History of Falling Results Fear of falling assessed by the ABC score was not significantly different between the normal and abnormal balance groups (Table I) and no correlation was found between the ABC score and the composite SOT score (Spearman rank correlation, r ¼ 0.124; p ¼ 0.381). However, there was a significant difference between those with normal and abnormal SOT scores with respect to their history of falling ( p ¼ 0.003, Fishers exact test). A positive history of falling within the past year was reported by 36% (n ¼ 8/22) of the claudicants with an abnormal composite SOT

and by only 3% (n ¼ 1/30) of the claudicants with a normal composite SOT score.

DISCUSSION This is the first study to demonstrate that global balance abnormalities and, in particular, vestibular balance dysfunction are extremely common in elderly claudicants, occurring in 41% of our study population. By extrapolation, one may hypothesize that these patients might be at a higher risk for falling and therefore this aspect of their management or treatment program deserves specific attention. Impaired composite SOT scores have been demonstrated to be useful in identifying not only patients with balance disorders but also those who are at a risk for falling, two recent articles have confirmed the presence of a relationship between poor SOT scores and a history of falling.18,19 The relevance of poor balance and increased risk of falling is of prime concern among the elderly population because they are more susceptible to morbidity-associated with falling as a result of a multitude of potential contributory risk factors. Balance deteriorates with age and this has been objectively demonstrated by decreasing SOT scores reported among older populations with a continued deterioration even into the ninth decade.14 Cohen et al. tested 94 independently-living healthy control subjects who were all capable of performing selfcare tasks unaided and among their population SOT scores varied, even to the extent of being abnormal in some patients, despite a lack of symptoms. Acknowledging that people may be functionally independent but might still have abnormal balance scores is important. We would suggest that these abnormal balance scores may represent a warning sign of potential future problems and that this particular population must be targeted so as to prevent or minimize further decline, risk of

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falling, and serious injury. This is particularly pertinent given that patients with peripheral arterial disease have been shown to have a greater rate of mobility loss.20 In fact, current functional competence may allow patients the freedom to participate in programs to improve stability and may also directly motivate patients to maintain their current state of independence. The translation of objective balance assessment into clinical practice is particularly pertinent as a screening tool and in turn target rehabilitation and monitor improvement in patients with a potential risk of falling. In contrast to previous clinical and research tests, CPD offers the advantages of quantitative data, simplified results interpretation, and the ability to highlight potential specific deficiencies, such as vestibular or visual dysfunction, which may require specific attention. Ideally, this data should be used in combination with thorough physical assessment and data from other appropriate tests such as specialized vestibular tests. The relevance of balance assessment and risk of falling specific to vascular surgery is clearly demonstrated by the strikingly high prevalence of postural instability among the claudicants in our study. All of the claudicants in this study presented to the vascular service with typical symptoms of claudication, none of them reported having symptoms related to balance or increasing incidence of falling. Therefore, the detection of a potential risk factor for falling in an asymptomatic group of vascular patients, similar to those in this study, highlights the common nature of balance problems and the lack of awareness among patients. Moreover, our study triggers immediate questions regarding the etiology of such balance abnormalities. The direct cause of balance abnormalities among claudicants is currently unknown and was not the targeted aim of this work. The explanation for impaired global balance in claudicants is probably multifactorial considering that elderly claudicants have multiple comorbidities. We specifically chose older subjects to gain information on this age group which is known to be at a high risk for falling; however, no significant variation in comorbidities was observed between patients with abnormal and those with normal balance in our study population. In addition, the ABPI results did not differ between normal and abnormal balance groups suggesting that the severity of ischemia is not a key contributory factor, although interestingly, treadmill walking distances were significantly shorter in the abnormal balance group. This may reflect an impaired tolerance of treadmill testing in patients with abnormal balance. Whether impaired balance

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can be directly attributed to peripheral vascular disease remains to be proven; however, potential avenues of research must include central causes, such as small and large vessel cerebrovascular disease, and peripheral causes, such as proprioceptive pathways and muscle weakness limiting the adaptive response. Claudicants may be expected to have a higher frequency of somatosensory balance abnormality because of peripheral neuropathy and impaired sensation as a reflection of their vascular disease, in particular, those with diabetes (who exhibited no significant increased rate in abnormal balance). Instead of predominant somatosensory dysfunction, we have demonstrated a high incidence of balance abnormalities secondary to vestibular dysfunction in patients with claudication. The functional effect of an impaired vestibular function score on a firm support surface in the presence of normal vision is negligible. In contrast, on irregular surfaces and in conditions with low lighting, such patients will experience instability. This is highly significant for elderly patients who are at a high risk of falling in tricky situations including getting out of bed at night and when they are out of the house walking on irregular paving. The high incidence of vestibular dysfunction in this group was unexpected because a direct etiological link between vestibular dysfunction and peripheral arterial disease has not been previously established. However, among people with balance disorders, vestibular dysfunction is quite common and represents up to 50% of cases.14 Although the high rate of vestibular dysfunction reported in this study may be a reflection of the spectrum of balance dysfunction within society, it may also be linked to high rates of systemic atherosclerosis including microvascular disease among claudicants. Vestibular dysfunction has previously been linked to atherosclerosis, in particular, vertebrobasilar insufficiency,21 even though research in this area is sparse. The purpose of the SOT and our study was to highlight a potential area of deficiency rather than to offer an absolute diagnosis. The sensory analysis results must be interpreted with the clinical assessment of each individual and patients should be referred to a specialist for further evaluation to identify and manage vestibular deficits. Of note, we found a significant difference between male and female claudicants in terms of balance scores. In 1977, Overstall et al. measured anteriorposterior sway using an ataxiameter for 306 elderly individuals,22 and noted an increase in sway with age, in particular, increased sway among women. They suggested a decline in central postural control

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and loss of proprioceptive information with age and hypothesized that increased sway seen among women may be a function of body weight to muscle mass ratio. A limitation of our study was the small number of female claudicants tested (13 females and 45 males). Further work, particularly those that examine larger numbers of both male and female claudicants compared individually with age- and gender-matched controls would be of benefit. NeuroCom controls were not gender-matched, thus there may be further discrepancies between the two genders with respect to balance and risk of falling. In fact, different training and rehabilitation regimes may be required for older women who are selfdependent. This avenue remains unexplored at present. The incidence of abnormal MCT latency results (24%) obtained in this study was lower than expected. Prolonged latency times have been associated with peripheral neuropathy and delayed central nervous system processing secondary to ageing or cerebral atrophy.23 A strong correlation has been previously described between small MCT latency and the ability to recover from sudden minor slips;24 therefore, these findings were reported as positive for the claudicants in this study because they were able to recover from or respond quickly to perturbations. In addition, it also suggests, that abnormal MCT latency was not a strong contributing factor to impaired balance and an increased risk of falling among the claudicants. In contrast, the incidence of abnormally weak response strength during MCT testing was high among our subjects (43%, n ¼ 23). The functional effect of poor response strength is most likely to be significant; in that a poor response strength resulting from either leg suggests difficulty in recovering from instability, similar to that which occurs when stumbling. Therefore, even with adequate latency timing, if the response strength is suboptimal, a patient may still be susceptible to falling. The relationship between response strength and latency to exercise training is unknown, particularly in this patient group. It may be hypothesized that strength training, for example, would be associated with improvements in response strength results. Once poor motor function or postural instability has been identified, treatment should be initiated in each patient. Objective improvements in balance and SOT scores have been clearly demonstrated after participation in various exercise programs.13,25,26 Whether this represents an additional benefit of current exercise programs for claudication or whether adaptations to such programs are required to optimize balance benefits remains to be proven.

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In addition, the effect of revascularization on balance dysfunction requires further study. This work has confirmed that patients with abnormal balance were more likely to have a history of falling. Of specific concern, however, was the lack of correlation between the fear of falling (ABC score) and abnormal balance scores, suggesting that claudicants lacked insight into their risk of falling. The limitations of this study include the retrospective collection of data related to falling and therefore it is not possible to predict future episodes of falling from these data; however, comments could be offered on the relationship between balance and a patient’s retrospective history of falling. Although improving a risk factor does not guarantee a reduction in incidence of falling or improved outcome, we can argue that the identification of a risk factor by using means such as objective balance assessment offers a useful tool in directing therapy toward those who are at potential risk. CDP may be particularly useful in identifying individuals who are at a risk of falling and who are not capable of recalling an episode of falling or those who are not willing to disclose their history of falling. In conclusion, this study highlights the high frequency of balance abnormalities among claudicants and recognizes the link between balance abnormalities and a risk of falling. Although claudicants are at a risk of falling, this is not represented by an increased fear of falling and they themselves may be unaware of this potential danger. It is our opinion that balance abnormalities among claudicants should be investigated, facilitating identification of a group of patients who are at a high risk of falling and permitting early implementation of fall-prevention strategies.

Grant funding for the current study was provided by the Joint Royal College of Surgeons of England and Dunhill Foundation Research Fellowship, a BUPA foundation research grant, and a Royal College of Surgeons of Edinburgh small research grant.

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