New research indicates that even in the absence of peripheral neuropathy, patients with long-standing diabetes mellitus are prone to impaired ankle function. Peripheral neuropathy is a main cause of sensory and motor deficit in patients with diabetes. Nerve degeneration may cause muscle weakness and atrophy, leading to ulcers and limited mobility at the foot and ankle, but other causes may also be involved, such as hyperglycemia leading to tendon and fascial damage.
This is a controlled, experimental study of patients with longstanding diabetes with and without peripheral neuropathy vs healthy control subjects without diabetes to examine alterations in foot-ankle biomechanics and in strength and mobility. Functional alterations were measured with an ankle dynamometer under active unloaded conditions in patients who were seated.
The findings suggest that mechanisms besides neuropathy may play a role in altered foot-ankle biomechanics seen in diabetics, lead author Dr. Claudia Giacomozzi, from Istituto Superiore di Sanita in Rome, and colleagues state in the July 4th online issue of BMC Musculoskeletal Disorders.
The sensory and motor deficits that accompany diabetic neuropathy can compromise gait control, result in nerve degeneration causing muscle weakness and atrophy, and lead to plantar ulcers, the investigators note. Prior research has suggested that neuropathy is needed for altered foot-ankle biomechanics in diabetics, but due to various methodologic issues, definitive conclusions could not be reached.
In the present study, Dr. Giacomozzi’s team addressed this topic by evaluating muscle performance and ankle mobility in 46 diabetics with and without neuropathy and in 21 controls under controlled conditions. The tests were conducted using dedicated equipment designed by the researchers, with the subject seated and the examined limb virtually unloaded.
Three-dimensional active ranges of motion and force moments were recorded, the authors note. The latter was performed during maximal isometric contractions with the foot blocked in various positions.
Compared to controls, ankle mobility was impaired in all of the diabetic patients. In the sagittal and transverse planes, ankle mobility was reduced by 11% and 20%, respectively, in diabetics without neuropathy compared with controls. The corresponding values for diabetics with neuropathy were 20% and 21%.
A significant drop in dorsal-flexing moments was also noted in diabetics with the greatest reductions being 28% and 37% for diabetics without and with neuropathy, respectively. Similarly, plantar-flexing moments were reduced by up to 15% for diabetics without neuropathy and up to 24% for those with neuropathy.
The authors conclude. "From a clinical point of view, the findings…may help design ad hoc rehabilitative paths, in order to maintain an adequate level of gait performance in the presence of long-term diabetes, thus preventing excessive loading of foot tissues at risk of ulceration."
- Patients with diabetes, with and without neuropathy, demonstrate reduced foot and ankle mobility and strength.
- Reductions in mobility and muscle performance at the ankle in patients with diabetes are greater in patients with neuropathy vs patients with diabetes without neuropathy.
BMC Musculoskelet Disord. 2008;9:99.
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