A Closer Look At Gait Analysis In Patients With Diabetes
A recent study by Raspovic reported that patients with an ulcer history had significant sagittal plane decreases in range of motion for the ankles and first metatarsophalangeal joints.10 Otherwise, most gait analysis studies I reviewed had surprisingly little to say regarding sagittal plane abnormalities in patients with diabetes. However, I have often observed sagittal joint motion reversal associated with functional or structural hallux limitus in my own patients with diabetes. This pattern of gait changes, as documented by Dananberg, includes decreased great toe dorsiflexion during propulsion, delay in ankle plantarflexion (heel lift), delay or failure to achieve knee extension, decreased hip extension, straightening of the lumbar spine, and cervical flexion.13
What Factors Alter Diabetic Gait?
Although research has not firmly established causal relationships for gait changes in patients with diabetes, peripheral neuropathy remains suspect number one. Kanji and colleagues have suggested that large fiber neuropathy, which affects gait with the loss of pain sensation and proprioception, occurs often in the insensate foot and many patients are unaware of this condition.14 Accordingly, it is likely that a proprioceptive deficit causes patients with diabetes to walk more carefully than those without diabetes and at a slower speed. Study outcomes comparing patients with and without diabetes are not clear regarding which gait alterations are specific to peripheral neuropathy and which also affect those without neuropathy. However, it is most likely that gait abnormalities occur across the spectrum of diabetes and increase with disease severity.15
There are some other interesting factors to consider besides neuropathy and proprioception. Research has suggested that decreased plantarflexor strength and ankle mobility contribute to a slower walking speed.9 Also, patients with a history of diabetes-related ulceration have less knee and ankle strength.10 Additionally, tissue changes can influence gait, foot-ground interface and the risk for ulceration in patients with diabetes.11 These tissue changes include poor skin quality, thickening of tendons and the plantar fascia, decreased joint mobility, muscle stiffness, and fat pad atrophy.
While obesity is another consideration, most studies I reviewed did not comment on body mass index even though the patients in control groups usually weighed much less. It is well documented that increasing excess body weight decreases walking speed and increases double limb support.16 More studies are needed that compare patients with diabetes to those without diabetes with appropriate controls for gender, age and body mass index.
What About Ground Reactive Forces?
Ground reactive forces act in all three dimensions when we walk. The two major components of ground reactive forces include normal (vertical) forces associated with plantar pressure and shear (horizontal) forces. Most diabetic foot research has focused on the relationship of plantar pressure and ulcers, likely because commercial platforms, pressure mats and in-shoe systems are readily available. However, the measurement of shear force remains more mysterious and elusive. Shear is more difficult to measure and commercial systems are not available for office use.
Plantar shear is an exciting new area of research and I think shear could one day prove to be more a significant factor for ulcer risk than plantar pressure. However, future studies are needed to substantiate a decrease in diabetic ulcers from shear-reducing shoe insoles or orthotic modifications. Another conundrum with shear is that we cannot eliminate it entirely. We need shear forces and ground resistance for normal walking to help propel us forward. If we eliminate too much shear, it might be similar to walking on one of the frozen lakes we have up here in Minnesota in January (helmet recommended).