Elsevier

Clinical Biomechanics

Volume 15, Issue 3, March 2000, Pages 196-202
Clinical Biomechanics

A study of biomechanical parameters in gait analysis and sensitive cronaxie of diabetic neuropathic patients

https://doi.org/10.1016/S0268-0033(99)00060-1Get rights and content

Abstract

Objective. The present investigation aims at studying the sensitive cronaxie in neuropathic and non-neuropathic diabetic patients as a measure of sensorial deficit. We seek to describe the gait using dynamic and temporal parameters. We have compared the results of the neuropathic patients to the results of a non-diabetic group. We have looked for relationships between peak plantar pressure and sensitive cronaxie in selected plantar areas.

Design and methods. The experimental procedures were divided in: (a) determination of the sensitive cronaxie in four selected plantar areas, (b) determination and description of peak plantar pressure, ground reaction force variables and single and double stance time. We analyzed and compared the results of the sensitive cronaxie and the biomechanical parameters obtained by three experimental groups: diabetic, neuropathic and non-diabetic subjects.

Results. The pathological response of the sensitive cronaxie worsened progressively for neuropathic and diabetic patients, respectively. Longer double and single stance times, lower minimum vertical force and lower growth rates were seen in the neuropathic patients when compared to diabetic and non-diabetic subjects.

Conclusions. These results indicate an alteration in the neuropathic patient movement structure. We have speculated that compensatory musculoskeletal mechanisms have been developed by neuropathic patients to compensate for their sensorial deficit. Future research is necessary to verify the relationship between neurophysiological and dynamic variables, since this relationship seems to be a good parameter for the interpretation and comprehension of the peripheral neuropathy.
Relevance

Peripheral neuropathy is one of the most insidious chronic complications of diabetes. It has been observed that dynamic changes in gait are usually associated with the peripheral neuropathy somatosensory deficits. Biomechanical studies have highlighted that dynamic gait evaluation can identify functional alterations, besides the analysis of sensitive cronaxie as a measure of sensorial deficits. They are also useful as a complimentary routine in the clinic treatment of diabetes and its further long-term complications.

Introduction

The human gait may present biomechanical differences depending on individual characteristics, such as morphological nature, physical activity, age and the presence of some disease. Pathological gait is commonly characterized by the presence of unusual biomechanical patterns. In this study, we will focus on the peripheral neuropathy, which is one of the most insidious chronic complications of diabetes [1]. The association of metabolic, neurophysiological and vascular factors seems to be responsible for the characteristic picture of the so-called “diabetic foot” [2]. The disease is initially characterized by a reduction in somesthesic sensitivity that can be tested by several techniques to quantify neurological deficits. Kimura [3], using a universal pulse generator, has highlighted electrodiagnostic evaluations which include the sensitive cronaxie. These electrophysiological tests can predict the actual physiological state of peripheral nerve fibers [4]. Sensitive cronaxie is defined as the minimum time of an electrical pulse required to excite a sensitive nerve with twice the rheobase intensity [3]. The rheobase is defined as the minimum intensity of an electrical pulse to incite a sensitive or motor response.

This disease can lead diabetic patients to plantar pressure distribution and ground reaction force changes during gait, as well as moments of force, probably because of its somatosensory deficits. Neuropathic patients can develop ulceration if deficits in somesthesic sensitivity are associated with these biomechanical changes expressed in some way as higher mechanical loads in gait [5]. According to Masson et al. [6] and Cavanagh et al. [7], morphological feet alterations associated with the neuropathy progress are the main causes of ulcer development if associated with higher peak plantar dynamic pressure. Mueller [8] argued that higher mechanical loads are the most important permissive factors of injuries and ulcers development in long-term diabetic patients. The incidence of ulceration due to excessive loading during gait has been shown to increase in this patients [9].

Musculoskeletal mechanisms and strategies are probably developed to compensate for some characteristics of a pathological condition of the human body [10]. These mechanisms can be studied through the biomechanical evaluation of reaction forces and pressure distribution over the plantar surface statically or dynamically. Such biomechanical parameters suggest characteristics of mechanical loads in the locomotor apparatus depending on the movement. They may even indicate functional gait alterations, as it is highlighted in some studies [10]. They reveal structure and function of foot, posture and movement control [11], [12]. Especially for the diabetic population, they have been important parameters for prevention and diagnosis of future risks of ulcer development and for diabetes therapy control [13], [14]. As far as ground reaction force is concerned, growth rates related to first and second vertical force peaks are influenced by some factors that define the locomotor apparatus capacity to adjust and attenuate loads during heel contact in gait [10]. Within these growth rates, we have been able to identify movement adaptations in the present study.

Due to the somatosensory threshold reduction in peripheral neuropathy, diabetic patients may develop changes in the foot contact phase during gait in order to reduce pressure in the injured areas, overloading other plantar areas [14]. Pollard and Quesne [15] and Duckworth et al. [14] have demonstrated close relationships between peak plantar pressure during gait and ulcer regions in diabetic neuropathic patients. Some longitudinal studies have also demonstrated close relationships among peak plantar pressure, ulcer regions and plantar areas of diminished sensibility [16]. Boulton et al. [17] have detected altered plantar pressure in gait even in patients with minimum evidence of neuropathy. Masson et al. [6] correlated peak pressure in some plantar areas with nerve conduction data, but they did not find any correlation between these dynamic responses and electrophysiological responses.

When some specific factors that have been described by Morag and Cavanagh [18] are present, higher peak plantar pressure during gait could also be observed. These factors were foot structure, gait style, physical characteristics and intrinsic and extrinsic muscle action. Each factor listed above involves a series of other elements. When one of such elements are changed, there is an alteration in the dynamic response. For example, motor dysfunctions related to diabetic neuropathy – such as deficits in foot joint mobility and orthopedic deformities – have altered peak plantar pressure and ground reaction forces [6], [7]. Masson et al. [6] observed higher plantar pressures over the forefoot in some patients with foot structural deformations independently of their etiology. Based on the discussion above, we can conclude that the dynamic changes under study are not restricted to diabetic neuropathy and although peak plantar pressure and neuropathy coexist in diabetics, the relationship between the two is only speculative.

The present investigation aims at studying sensorial deficits in neuropathic patients using the sensitive cronaxie. We have evaluated and described the gait in neuropathic diabetic patients using plantar pressure distribution, ground reaction force variables and temporal parameters. We have compared the results obtained in the investigation of neuropathic patients to the results obtained in the investigation of a non-diabetic group. Within this gait characteristics description, we speculate about dynamic mechanisms in gait developed by neuropathic diabetic patients to compensate for sensorial deficits. We also have looked for relationships between peak plantar pressure and sensitive cronaxie in corresponding selected plantar areas.

Section snippets

Subjects

Thirty-six voluntary adults of both sexes from the National Association of Diabetics and from the University Hospital of the University of Sao Paulo were assigned by the University Hospital's medical staff to one of the following three groups: diabetic group (DG) with no diagnosed neuropathy; diabetic neuropathic group (DNG) with neuropathy confirmed by symptomatology and electrodiagnostic exam; and a non-diabetic group (CG).

Experimental procedures

The experimental procedures took place during the morning in the

Results

The experimental groups’ demographic data is described in Table 1. And as far as anthropometric feet measures are concerned, there were no statistical differences among those studied groups (P>0.05), nor between the right and the left foot in each group. The DG and the CG subjects presented normal arch index, matching the report by Cavanagh and Rodgers [20], that is, values between 0.21 and 0.26. However, the arch index of the DG patients was high: smaller or equal to 0.21 for the right foot.

Discussion

This investigation studies somatosensory loss due to diabetic neuropathy by determining sensitive cronaxie. We also describe and compare dynamic and temporal gait data of diabetic neuropathic patients, diabetic patients and a non-diabetic control group. In particular, this study seeks to investigate if neuropathic patients develop dynamic changes during gait to compensate for sensorial deficits. The relationship between peak plantar pressure and sensitive cronaxie, as a measure of somatosensory

Conclusion

The present investigation identifies significant differences in somatosensory responses in the studied plantar areas among the groups. The pathological response of the sensitive cronaxie worsened progressively for DNG and DG patients, respectively. The method used to determine the electrophysiological response was valuable for the identification of deficits in sensitivity. Longer double and single stance times, lower minimum vertical force and lower growth rates were seen in DNG patients when

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