E. A. Masson

Relationship of Limited Joint Mobility to Abnormal Foot Pressures and Diabetic Foot Ulceration

Objective To investigate the role of limited joint mobility (LJM) in causing abnormal foot pressures and foot ulceration. Research Design and Methods The subjects were recruited from a general diabetes clinic where patients were screened for neuropathy, retinopathy, and elevated plantar foot pressure. Sixty-four patients in five groups were matched by age and sex in the following groups: group 1, patients with LJM and neuropathy; group 2, nonneuropathic diabetic patients with LJM; group 3, patients with neuropathy and no LJM; group 4, diabetic control subjects; and group 5, nondiabetic control subjects. Joint mobility was assessed in the foot at subtalar and metatarsophalangeal joints; plantar foot pressures were assessed by optical pedobarography and neuropathic status by a Biothesiometer and electrophysiology. Results Joint mobility was reduced at both sites in groups 1 and 2 compared with groups 3, 4, and 5 (P < 0.001). Plantar foot pressures were significantly higher in groups 1 and 2 compared with groups 3, 4, and 5 (P < 0.001). No differences in plantar foot pressures were observed between groups 1 and 2. There were strong correlations between plantar foot pressures and joint mobility in the foot (r = −0.7, P < 0.001). Previous foot ulceration was present in 65% of patients in group 1, none in group 2, and 5% in group 3. Conclusions 1) LJM may be a major factor in causing abnormally high plantar foot pressures, 2) abnormal plantar foot pressures alone do not lead to foot ulceration, and 3) LJM contributes to foot ulceration in the susceptible neuropathic foot.

Current perception thresholds: a new, quick, and reproducible method for the assessment of peripheral neuropathy in diabetes mellitus

SummaryThe Neurometer is a variable constant current sine wave stimulator, and has recently been proposed as a simple non-invasive and quantitative measure of peripheral nerve function. The device is portable and battery operated; assessment of upper and lower extremities takes only a few min, in contrast to conventional assessment techniques. In order to assess its potential in the quantification of diabetic neuropathy, detection thresholds for constant current electric sine wave stimulation were measured at three different frequencies in different sites in 31 healthy control subjects and 90 diabetic patients with and without neuropathy. The device provides good discrimination between neuropathic and non-neuropathic groups (p<0.001) and is quick and easy to use. Comparisons with results of conventional tests of nerve function show that high frequency detection thresholds correlate best with tests of large fibre function (r= 0.42–0.69, p<0.001), and low frequency detection thresholds correlate with tests of small fibre function (r=0.34–0.46, p<0.005). It is concluded that the device may be a simple and comprehensive way of assessing peripheral nerve function.

Abnormal Foot Pressures Alone May not Cause Ulceration

Both rheumatoid arthritis and diabetes have been associated with the development of abnormally high pressures under the feet, and ulceration has been considered to be a problem in both conditions. In order to examine further the relationship between high foot pressure, neurological abnormalities, and ulceration, we have studied two groups of patients: (a) 38 diabetic patients and (b) 37 patients with rheumatoid arthritis who had similar clinical abnormalities of the feet. Thirty‐two percent of diabetic patients had a history of plantar ulceration compared with none of the rheumatoid group (p < 0.01). However, the diabetic group had considerably more severe neuropathy (peroneal nerve motor conduction velocity 35.4 ± 4.8 m s−1 vs 44.4 ± 5.2 m s−1 (mean ± SD), p < 0.001; vibration perception threshold 33.5 ± 13.4 vs 16.9 ± 10.9, p < 0.001), with a similar frequency of elevated plantar pressures (51 % vs 61 %, NS). These data emphasize the importance of the loss of sensory awareness in the pathogenesis of diabetic foot ulceration, and suggest that high pressure alone is not a direct cause of ulceration.

Hypoxic neuropathy: relevance to human diabetic neuropathy

SummaryClinical and neurophysiological studies were conducted in 47 patients with chronic obstructive airways disease and compared with 46 age-matched control subjects. Symptomatic neuropathy was reported in 13% and ankle jerks were absent in 45% of hypoxic patients. Peroneal and median nerve conduction velocities and median and sural sensory nerve amplitudes were significantly reduced in hypoxic patients (p<0.01). Six hypoxic patients underwent biopsy of the sural nerve, soleus muscle and overlying skin. Nerve glucose, sorbitol, fructose and myo-inositol concentrations were normal. Detailed light and electronrmicroscopy revealed both nerve fibre and microvascular pathology. Segmental demyelination (32%) and unmyelinated fibre degeneration were found to be prominent lesions. The sural nerve perineurium was thickened due to an increase in the number of perineurial lamellae and an increase in intraperineurial space. Basement membrane thickening was observed in capillaries of nerve, muscle and skin. Endothelial cell hyperplasia and hypertrophy were observed in nerve and muscle capillaries but not in skin capillaries. In conclusion, this study has provided neurological, neurophysiological and neuropathological evidence of a neuropathy in hypoxic patients with chronic obstructive airways disease. These findings may be of relevance to some aspects of the aetiology of human diabetic neuropathy.

The Neurometer: Validation and Comparison with Conventional Tests for Diabetic Neuropathy

The Neurometer is a portable constant current sine wave stimulator, which has recently been advocated for the quantification of peripheral nerve dysfunction by the measurement of detection thresholds for constant current stimulation. Stimuli are applied through surface electrodes at three frequencies and a forced choice method is used to determine the minimum amplitude for detection. The possible application of the Neurometer to the diagnosis and measurement of diabetic neuropathy was evaluated. The preliminary Neurometry results in comparison to those of conventional nerve testing techniques, including thermal and vibration detection thresholds, are discussed. It appears that the device may be a useful screening instrument which could give a fairly comprehensive idea of the functional integrity of different nerve fibre populations, and a full assessment takes only 10 to 15 min, in contrast to the conventional alternatives.

Endoneurial capillary abnormalities in mild human diabetic neuropathy.

Microvascular factors have been implicated in the pathogenesis of human diabetic neuropathy. The extent of microangiopathy was assessed in 15 diabetic patients with clinically mild neuropathy and compared with eight age matched control subjects. Endoneurial capillary density was reduced (p less than 0.04) and correlated significantly with reduced myelinated fibre density (p less than 0.01). Both basement membrane area (p less than 0.0001) and endothelial cell profile number per capillary (p less than 0.002) were significantly increased in diabetic patients and correlated significantly with both neurophysiological and neuropathological measures of neuropathic severity. There was no evidence of endothelial cell hypertrophy as assessed by either cross sectional endothelial cell area or a reduction in luminal size. Furthermore, the percentage of closed vessels did not differ between diabetic patients and control subjects and failed to relate to measures of neuropathic severity. It was concluded that microvascular abnormalities are prominent in patients with clinically mild human diabetic neuropathy, and that these data provide further support for the role of endoneurial capillary disease in the development of this condition.

Studies of Experimental Hosiery in Diabetic Neuropathic Patients with High Foot Pressures

High plantar pressures and painless trauma are associated with the development of foot ulcers in diabetic patients. Padded hosiery has been reported to reduce plantar pressures in patients at risk of ulceration. Using the optical pedobarograph we have studied 10 patients who regularly wore experimental padded hosiery for 6 months. The hosiery continued to provide substantial and significant reduction in peak forefoot pressures at 3 months (mean reduction 15.5 %, p < 0.01) and 6 months (17.6 %, p < 0.01), although the level of reduction was less than that seen at baseline (31.3 %, p < 0.05). In addition, commercially available hosiery designed as sportswear has been tested, and compared with experimental hosiery. Although these socks (with high or medium density padding) provided significant pressure reduction versus barefoot (mean 17.4 % and 10.4 %, p < 0.01), this was not as great as that seen with experimental hosiery (27 %, p < 0.05). Thus the use of socks designed to reduce pressure stress on diabetic neuropathic feet is effective, and continues to be so for a considerable period of time. Commercially available sports socks may also have a place in the management of the diabetic insensitive foot.

Calibration problems with the Biothesiometer.

The Biothesiometer is probably the commonest device for the quantitative assessment of vibration perception in use in diabetes research in this country. Several publications of studies of the normal population report a very large variance, particularly in the order patient. In order to try to explain these differences we have attempted a lenght calibration of the output of several Biothesiometers, which the manufacturers suggest are standardized

The use of multiple insulin injection therapy using ‘NovoPenR’ in a routine out-patient setting☆

Multiple injection therapy using self-contained cartridge devices such as NovoPen has become a standard option for the treatment of insulin-requiring diabetes in recent years. Such treatment was previously viewed as impractical by the majority of patients and their physicians. Many small pilot studies have suggested that the use of such therapy leads to improvements in glycaemic control. We have many (greater than 200) patients in our clinic who use this form of treatment in the context of a routine out-patient department, where intensive supervision, which characterises all studies involving small numbers, is not practical. We have carried out a questionnaire survey of these patients to ascertain their attitudes to this form of therapy, and made some assessment of its impact on glycaemic control. Multiple injection therapy is a very popular form of therapy, leading to improvements in lifestyle and reduction in frequency of hypoglycaemic symptoms. However, its lack of impact on glycaemic control as estimated by measurement of haemoglobin A1 is disappointing.