Dequan Zou

Plantar Stresses on the Neuropathic Foot During Barefoot Walking

Background and Purpose: Patients with diabetes mellitus and peripheral neuropathy are at high risk for plantar skin breakdown due to unnoticed plantar stresses during walking. The purpose of this study was to determine differences in stress variables (peak plantar pressure, peak pressure gradient, peak maximal subsurface shear stress, and depth of peak maximal subsurface shear stress) between the forefoot (where most ulcers occur) and the rear foot in subjects with and without diabetes mellitus, peripheral neuropathy, and a plantar ulcer measured during barefoot walking. Subjects: Twenty-four subjects participated: 12 with diabetes mellitus, peripheral neuropathy, and a plantar ulcer (DM+PN group) and 12 with no history of diabetes mellitus or peripheral neuropathy (control group). The subjects (11 men, 13 women) had a mean age (±SD) of 54±8 years. Methods: Plantar pressures were measured during barefoot walking using a pressure platform. Stress variables were estimated at the forefoot and the rear foot for all subjects. Results: All stress variables were higher (127%–871%) in the forefoot than in the rear foot, and the peak pressure gradient showed the greatest difference (538%–871%). All stress variables were higher in the forefoot in the DM+PN group compared with the control group (34%–85%), and the peak pressure gradient showed the greatest difference (85%). The depth (X̄±SD) of peak maximum subsurface shear stress in the forefoot in the DM+PN group was half that in the control group (3.8±2.0 versus 8.0±4.3 mm, respectively). Discussion and Conclusions: These results indicate that stresses are relatively higher and located closer to the skin surface in locations where skin breakdown is most likely to occur. These stress variables may have additional value in predicting skin injury over the traditionally measured peak plantar pressure, but prospective studies using these variables to predict ulcer risk are needed to test this hypothesis.

Accuracy and reliability testing of a portable soft tissue indentor

We have designed, built, and tested a portable indentor device that allows us to determine force/displacement (F/D) measurements on soft tissue in a clinical or research setting. The indentor system consists of a load cell mounted on a three-dimensional measurement device (Metrecom). The output of the load cell and the Metrecom are recorded and analyzed by software running on a notebook computer. The displacement calibration of the Metrecom gave an average error=0.005 mm [standard deviation (SD)=0.062)]. The force calibration of the load cell resulted in an average error=0.022 N (SD=0.049) and a linearity of 1.0062(R/sup 2/=0.9998). The indentor device was tested on six different human soft tissues by two different investigators. The interreliabilities and intrareliabilities were 0.99 [interclass correlation (ICC)] indicating that the results were repeatable by more than one investigator. F/D measurements from indentor testing on two materials were comparable to values measured using an Instron device (5.34 versus, 5.52 N/mm, and 0.98 versus 1.04 N/mm). The device was used to measure the soft tissue characteristics on the plantar surface of the foot of one subject. These data were used to calculate the effective Youngs modulus for the tissue using equations derived by Zheng et al. [1999] and indicated a wide range of values dependent upon the portion of the F/D curve used. All results indicate data from this portable indentor device are reliable, accurate, and sensitive enough to identify mechanical properties of human tissues.

Differences in end-range lumbar flexion during slumped sitting and forward bending between low back pain subgroups and genders

Patterns of lumbar posture and motion are associated with low back pain (LBP). Research suggests LBP subgroups demonstrate different patterns during common tasks. This study assessed differences in end-range lumbar flexion during two tasks between two LBP subgroups classified according to the Movement System Impairment model. Additionally, the impact of gender differences on subgroup differences was assessed. Kinematic data were collected. Subjects in the Rotation (Rot) and Rotation with Extension (RotExt) LBP subgroups were asked to sit slumped and bend forward from standing. Lumbar end-range flexion was calculated. Subjects reported symptom behaviour during each test. Compared to the RotExt subgroup, the Rot subgroup demonstrated greater end-range lumbar flexion during slumped sitting and a trend towards greater end-range lumbar flexion with forward bending. Compared to females, males demonstrated greater end-range lumbar flexion during slumped sitting and forward bending. A greater proportion of people in the Rot subgroup reported symptoms with each test compared to the RotExt subgroup. Males and females were equally likely to report symptoms with each test. Gender differences were not responsible for LBP subgroup differences. Subgrouping people with LBP provides insight into differences in lumbar motion within the LBP population. Results suggesting potential consistent differences across flexion-related tasks support the presence of stereotypical movement patterns that are related to LBP.

Sex Differences in Lumbopelvic Movement Patterns During Hip Medial Rotation in People With Chronic Low Back Pain

OBJECTIVE To examine sex differences in lumbopelvic motion and symptom behavior during hip medial rotation in people with low back pain (LBP). We hypothesized that men would demonstrate greater and earlier lumbopelvic motion and would be more likely to report increased symptoms compared with women. DESIGN Cross-sectional observational study. SETTING University musculoskeletal analysis laboratory. PARTICIPANTS Persons with chronic LBP (N=59; 30 men, 29 women) were recruited from the community and a university-based physical therapy clinic. INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES Lumbopelvic rotation range of motion, amount of hip rotation completed before the start of lumbopelvic motion, and provocation of LBP symptoms during the test of prone hip medial rotation were measured. RESULTS Men demonstrated significantly more lumbopelvic rotation (men, 10.0°±5.1°; women, 4.5°±3.9°; P<.001) and completed less hip rotation before the start of lumbopelvic motion (men, 5.4°±3.8°; women, 16.0°±13.2°; P<.001) compared with women. Additionally, a significantly greater percentage of men (60.0%) than women (34.5%; P=.050) reported increased symptoms with hip medial rotation. CONCLUSIONS Men could be at greater risk than women for experiencing LBP symptoms related to hip medial rotation as a result of greater and earlier lumbopelvic motion.

Gender Differences in Modifying Lumbopelvic Motion during Hip Medial Rotation in People with Low Back Pain

Reducing increased or early lumbopelvic motion during trunk or limb movements may be an important component of low back pain treatment. The ability to reduce lumbopelvic motion may be influenced by gender. The purpose of the current study was to examine the effect of gender on the ability of people with low back pain to reduce lumbopelvic motion during hip medial rotation following physical therapy treatment. Lumbopelvic rotation and hip rotation before the start of lumbopelvic rotation were assessed pre- and posttreatment for 16 females and 15 males. Both men and women decreased lumbopelvic rotation and completed more hip rotation before the start of lumbopelvic rotation post-treatment compared to pre-treatment. Men demonstrated greater lumbopelvic rotation and completed less hip rotation before the start of lumbopelvic rotation than women both pre- and post-treatment. Both men and women reduced lumbopelvic motion relative to their starting values, but, overall, men still demonstrated greater and earlier lumbopelvic motion. These results may have important implications for understanding differences in the evaluation and treatment of men and women with low back pain.

Comparing Plantarflexor Power and Function using Carbon Fiber Versus Traditional Thermoplastic Ankle Foot Orthoses: Case Series

Background: Thermoplastic ankle foot orthoses (TAFO) control the foot during swing and initial contact of walking. Carbon fiber AFOs (CAFO) has the added ability to store and return energy at push off. The purpose of this report is to determine if plantarflexor power and function can be improved with a CAFO compared to a TAFO and identify factors that may be related to plantarflexor power improvement in two adults with reduced ankle muscle performance. Case Descriptions: Two participants with reduced ankle muscle performance completed a gait analysis and the 6 minute walk (6MW) test wearing each AFO. Physical function was higher in Participant 1 compared to Participant 2 as measured by the Foot and Ankle Ability Measure and walking speed. Outcomes: Participant 1’s 6MW distance and plantarflexor power improved wearing the CAFO compared to the TAFO (6MW distance: TAFO=427 m, CAFO=553 m and Plantarflexor power: TAFO=1.16 W/kg, CAFO=1.56 W/kg). Participant 2 showed similar outcomes in both AFO conditions (6MW distance: TAFO=290 m, CAFO=276 m and plantarflexor power: TAFO=0.89 W/kg, CAFO=0.60 W/kg). Discussion: A CAFO increased walking speed and plantarflexor power compared to a TAFO in a person with a relatively high level of physical function but not in a person with a relatively low level of physical function. These preliminary results suggest a sufficiently high level of physical function is required to “engage” the CAFO and benefit from its energy storing capabilities.