Hip strength: ankle proprioceptive threshold ratio predicts falls and injury in diabetic neuropathy.

INTRODUCTION: We determined lower limb neuromuscular capacities associated with falls and fall-related injuries in older people with declining peripheral nerve function. METHODS: Thirty-two subjects (67.4 ± 13.4 years; 19 with type 2 diabetes), representing a spectrum of peripheral neurologic function, were evaluated with frontal plane proprioceptive thresholds at the ankle, frontal plane motor function at the ankle and hip, and prospective follow-up for 1 year. RESULTS: Falls and fall-related injuries were reported by 20 (62.5%) and 14 (43.8%) subjects, respectively. The ratio of hip adductor rate of torque development to ankle proprioceptive threshold (Hip(STR) /AnkPRO ) predicted falls (pseudo-R(2) = .726) and injury (pseudo-R(2) = .382). No other variable maintained significance in the presence of Hip(STR) /AnkPRO . CONCLUSIONS: Fall and injury risk in the population studied is related inversely to Hip(STR) /AnkPRO . Increasing rapidly available hip strength in patients with neuropathic ankle sensory impairment may decrease risk of falls and related injuries.

Accuracy of Clinical Techniques for Evaluating Lower Limb Sensorimotor Functions Associated With Increased Fall Risk.

BACKGROUND: In prior work, laboratory-based measures of hip motor function and ankle proprioceptive precision were critical to maintaining unipedal stance and fall/fall-related injury risk. However, the optimal clinical evaluation techniques for predicting these measures are unknown. OBJECTIVE: To evaluate the diagnostic accuracy of common clinical maneuvers in predicting laboratory-based measures of frontal plane hip rate of torque development (Hip(RTD)) and ankle proprioceptive thresholds (AnkPRO) associated with increased fall risk. DESIGN: Prospective, observational study. SETTING: Biomechanical research laboratory. PARTICIPANTS: A total of 41 older subjects (aged 69.1 ± 8.3 years), 25 with varying degrees of diabetic distal symmetric polyneuropathy and 16 without. ASSESSMENTS: Clinical hip strength was evaluated by manual muscle testing (MMT) and lateral plank time, defined as the number of seconds that the laterally lying subject could lift the hips from the support surface. Foot/ankle evaluation included Achilles reflex and vibratory, proprioceptive, monofilament, and pinprick sensations at the great toe. MAIN OUTCOME MEASURES: Hip(RTD), abduction and adduction, using a custom whole-body dynamometer. AnkPRO determined with subjects standing using a foot cradle system and a staircase series of 100 frontal plane rotational stimuli. RESULTS: Pearson correlation coefficients (r) and receiver operator characteristic (ROC) curves revealed that LPT correlated more strongly with Hip(RTD) (r/P = 0.61/<.001 and 0.67/<.001, for abductor/adductor, respectively) than did hip abductor MMT (r/P = 0.31/.044). Subjects with greater vibratory and proprioceptive sensation, and intact Achilles reflexes, monofilament, and pin sensation had more precise AnkPRO. LPT of <12 seconds yielded a sensitivity/specificity of 91%/80% for identifying Hip(RTD) < 0.25 (body size in Newton-meters), and vibratory perception of <8 seconds yielded a sensitivity/specificity of 94%/80% for the identification of AnkPRO >1.0°. CONCLUSIONS: LPT is a more effective measure of Hip(RTD) than MMT. Similarly, clinical vibratory sense and monofilament testing are effective measures of AnkPRO, whereas clinical proprioceptive sense is not.

Gait Efficiency on an Uneven Surface Is Associated with Falls and Injury in Older Subjects with a Spectrum of Lower Limb Neuromuscular Function: A Prospective Study.

OBJECTIVE: The objective of this study was to determine which gait measures on smooth and uneven surfaces predict falls and fall-related injuries in older subjects with diabetic peripheral neuropathy. DESIGN: Twenty-seven subjects (12 women) with a spectrum of peripheral nerve function ranging from normal to moderately severe diabetic peripheral neuropathy walked on smooth and uneven surfaces, with gait parameters determined by optoelectronic kinematic techniques. Falls and injuries were then determined prospectively over the following year. RESULTS: Seventeen subjects (62.9%) fell and 12 (44.4%) sustained a fall-related injury. As compared with nonfallers, the subject group reporting any fall, as well as the subject group reporting fall-related injury, demonstrated decreased speed, greater step width (SW), shorter step length (SL), and greater SW-to-SL ratio (SW:SL) on both surfaces. Uneven surface SW:SL was the strongest predictor of falls (pseudo-r = 0.65; P = 0.012) and remained so with inclusion of other relevant variables into the model. Post hoc analysis comparing injured with noninjured fallers showed no difference in any gait parameter. CONCLUSION: SW:SL on an uneven surface is the strongest predictor of falls and injuries in older subjects with a spectrum of peripheral neurologic function. Given the relationship between SW:SL and efficiency, older neuropathic patients at increased fall risk appear to sacrifice efficiency for stability on uneven surfaces.

Influence of an irregular surface and low light on the step variability of patients with peripheral neuropathy during level gait.

Patients with peripheral neuropathy (PN) report greater difficulty walking on irregular surfaces with low light (IL) than on flat surfaces with regular lighting (FR). We tested the primary hypothesis that older PN patients would demonstrate greater step width and step width variability under IL conditions than under FR conditions. Forty-two subjects (22 male, 20 female: mean +/- S.D.: 64.7 +/- 9.8 years) with PN underwent history, physical examination, and electrodiagnostic testing. Subjects were asked to walk 10 m at a comfortable speed while kinematic and force data were measured at 100 Hz using optoelectronic markers and foot switches. Ten trials were conducted under both IL and FR conditions. Step width, time, length, and speed were calculated with a MATLAB algorithm, with the standard deviation serving as the measure of variability. The results showed that under IL, as compared to FR, conditions subjects demonstrated greater step width (197.1 +/- 40.8 mm versus 180.5 +/- 32.4 mm; P < 0.001) and step width variability (40.4 +/- 9.0 mm versus 34.5 +/- 8.4 mm; P < 0.001), step time and its variability (P < 0.001 and P = 0.003, respectively), and step length variability (P < 0.001). Average step length and gait speed decreased under IL conditions (P < 0.001 for both). Step width variability and step time variability correlated best under IL conditions with a clinical measure of PN severity and fall history, respectively. We conclude that IL conditions cause PN patients to increase the variability of their step width and other gait parameters.

Interventions improve gait regularity in patients with peripheral neuropathy while walking on an irregular surface under low light.

OBJECTIVES: To determine which, if any, of three inexpensive interventions improve gait regularity in patients with peripheral neuropathy (PN) while walking on an irregular surface under low-light conditions. DESIGN: Observational. SETTING: University of Michigan Biomechanics Research Laboratory. PARTICIPANTS: Forty-two patients with PN (20 women), mean age+/-standard deviation=64.5+/-9.7. INTERVENTIONS: A straight cane, touch of a vertical surface, or semirigid ankle orthoses. MEASUREMENTS: Step-width variability and range, step-time variability, and speed. RESULTS: Subjects demonstrated significantly less step-width variability (mean=41.0+/-1.5, 36.9+/-1.6, 37.2+/-1.3, and 35.9+/-1.5 mm for baseline, cane, orthoses, and vertical surface, respectively; P<.0001) and range (182.7+/-7.4, 163.7+/-8.3, 164.3+/-7.4, 154.3+/-6.9 mm for baseline, cane, orthoses and vertical surface, respectively; P=.0006) with each of the interventions than under baseline conditions. Step-time variability significantly decreased with use of the orthoses and vertical surface but not the cane (P=.0001). Use of a cane, but not orthoses or vertical surface, was associated with decreased speed (0.79+/-0.03, 0.73+/-0.03, 0.79+/-0.03, 0.80+/-0.03 m/s for baseline, cane, orthoses, and vertical surface, respectively; P=.0001). CONCLUSION: Older patients with PN demonstrate improved spatial and temporal measures of gait regularity with the use of a cane, ankle orthoses, or touch of a vertical surface while walking under challenging conditions. The decreased speed and stigma associated with the cane and uncertain availability of a vertical surface suggest that the ankle orthoses may be the most practical intervention.

A comparison of gait characteristics between older women with and without peripheral neuropathy in standard and challenging environments.

OBJECTIVES: To compare gait patterns in older women with and without peripheral neuropathy (PN) in standard (smooth surface, normal lighting) and challenging environments (CE) (irregular surface, low lighting). DESIGN: Observational, controlled study of 24 subjects. SETTING: Biomechanical research laboratory. PARTICIPANTS: Twenty-four older women, 12 with PN and 12 without PN (mean age +/- standard deviation =67.1 +/- 7.9 and 70.2 +/- 4.3, respectively). MEASUREMENTS: Gait parameters and, in the 12 PN subjects, neuropathy severity. RESULTS: The CE was associated with increases in step width, step-width variability, step-width range, step width-to-step length ratio, step time and step-time variability, and decreases in step length and speed. The PN subjects demonstrated a greater step width-to-step length ratio and step time and shorter step length and slower speed than the control subjects. In adapting to the CE, the PN subjects demonstrated greater increases in step width-to-step length ratio and step-time variability and a greater decrease in step length than did the control subjects. In the standard environment, only one gait parameter correlated with PN severity, whereas in the CE, four gait parameters did so. CONCLUSION: The subjects demonstrated a gait that was slower, less efficient, and more variable temporally and in the frontal plane in the CE. Control and PN subjects demonstrated similar variability in medial-lateral step placement in the CE but at the cost of speed and efficiency for the PN subjects. Because the CE magnified gait differences between the two groups of subjects and caused gait changes in the PN subjects that correlated with PN severity, the CE may offer improved resolution for detecting gait abnormalities.

The relationship between frontal plane gait variability and ankle range of motion in middle-aged and older persons with neuropathy.

OBJECTIVE: To explore the relationship between frontal plane ankle range of motion (ROM) and frontal plane control during gait, as determined by step-width variability and step-width range, among middle-aged and older persons with peripheral neuropathy (PN). DESIGN: Observational study of 39 adults (mean age +/- standard deviation = 64.7 +/- 9.5 yrs) with PN. Demographic and clinical data, including measures of ankle ROM and PN severity, and spatiotemporal gait measures were obtained. Correlation and multivariate analyses were used to identify relationships between measures of ankle ROM and frontal plane gait variability. RESULTS: Significant negative correlations were identified between frontal plane ankle ROM (inversion + eversion), and step-width variability (r = -0.344; P = 0.032) and step-width range (r = -0.386, P = 0.015). Multivariate analyses showed that the relationship between ankle ROM and step-width variability weakened in the presence of PN severity, with ROM and PN severity both demonstrating trends toward independent associations with step-width variability (P = 0.086 and 0.083, respectively; adjusted r2 = 0.145). However, ankle ROM demonstrated a stronger association with step-width range than did PN severity (P = 0.043 and 0.098, respectively; adjusted r2 = 0.169). CONCLUSIONS: Increased frontal plane ankle ROM is associated with decreased variability in frontal plane foot placement during gait among middle-aged and older persons with PN, a population at high risk for falls.

Falls and gait characteristics among older persons with peripheral neuropathy.

OBJECTIVE: To prospectively determine the frequency and circumstances of falls in older persons with peripheral neuropathy and to identify gait characteristics on smooth and irregular surfaces associated with falls in this same population. DESIGN: This was a descriptive and observational study of a prospective group cohort. Spatial and temporal gait measures on smooth and irregular surfaces, as well as basic demographic and clinical data, were obtained in 20 older persons with peripheral neuropathy. Falls and fall-related injuries were then prospectively determined for 1 yr. RESULTS: Thirteen of 20 (65%) subjects fell, and 6 of 20 (30%) subjects sustained a fall-related injury during the year of observation. Of the 76 reported falls, 69 (90.8%) were associated with a surface abnormality (irregular or slick). Gait measures on the smooth surface did not distinguish between fall groups. On the irregular surface, however, step-time variability tended to be higher for those subjects who fell than for those who did not (89 +/- 29 vs. 64 +/- 26 msecs, respectively; P = 0.077) and for those who were injured from a fall compared with those who were not injured (101 +/- 21 vs. 71 +/- 29 msecs, respectively; P = 0.038). CONCLUSIONS: Older patients with peripheral neuropathy have a high rate of falls, and these falls are often associated with walking on irregular surfaces. Gait analysis on an irregular surface may be superior to that on a smooth surface for detecting fall risk in this patient population.

Gait analysis in a challenging environment differentiates between fallers and nonfallers among older patients with peripheral neuropathy.

OBJECTIVE: To identify differences in gait based on fall history among a group of older subjects with peripheral neuropathy (PN) in 2 environments: standard (SE) (smooth surface, normal lighting) and challenging (CE) (irregular surface, low lighting). DESIGN: Observational, case-control study of PN subjects with and without a history of falling in the previous year. SETTING: A biomechanical laboratory. PARTICIPANTS: Forty-two subjects (mean age, 64.7+/-9.8 y; 20 [47.6%] women), including 22 (52.4%) with a history of at least 1 fall in the previous year. INTERVENTION: Subjects walked in the SE and CE while kinematic data were obtained. MAIN OUTCOME MEASURES: Step width variability, step time variability, step width-to-step length ratio, step length, and step time and speed (with step length and speed normalized for height) in the SE and CE. RESULTS: In the SE, gait parameters of subjects with and without a history of falls did not differ significantly. However, in the CE, subjects with a history of falls had increased step time variability (P=.001). Moreover, significant interactions between environment and fall status were identified: in the CE, subjects with a history of falls had greater increases in step time variability (P=.010) and step width-to-step length ratio (P=.009) and greater decreases in step length (P=.007) and speed (P=.045) than did subjects with no fall history. CONCLUSIONS: Analysis of gait in the CE and adjustment to the CE from the SE effectively identified gait characteristics associated with falls in an older PN population, whereas analysis of gait in the SE did not. PN-associated gait dysfunction is more sensitively detected on an irregular rather than on a flat surface.