Biomedical subjects

Velio Macellari

Publications and source records attributed to Velio Macellari.

6 recordsLinked to original sources

PubMed2003

Temporal components of the motor patterns expressed by the human spinal cord reflect foot kinematics.

What are the building blocks with which the human spinal cord constructs the motor patterns of locomotion? In principle, they could correspond to each individual activity pattern in dozens of different muscles. Alternatively, there could exist a small set of constituent temporal components that are common to all activation patterns and reflect global kinematic goals. To address this issue, we studied patients with spinal injury trained to step on a treadmill with body weight support. Patients learned to produce foot kinematics similar to that of healthy subjects but with activity patterns of individual muscles generally different from the control group. Hidden in the muscle patterns, we found a basic set of five temporal components, whose flexible combination accounted for the wide range of muscle patterns recorded in both controls and patients. Furthermore, two of the components were systematically related to foot kinematics across different stepping speeds and loading conditions. We suggest that the components are related to control signals output by spinal pattern generators, normally under the influence of descending and afferent inputs.

Adult↗

PubMed2003

Objective analysis of finger function.

Hand motor tasks, even those commonly required by daily life activities, entail complex muscle activation. This article describes a self-contained experimental set-up for the objective kinetic and kinematic analysis of each finger function under several working conditions. Special attention is given to grasping and pressing under isometric conditions. The analysis of the contribution of the thumb is particular to this system. This system has proved accurate, reliable, easy-to-use, and suitable for applications in research environments, and as a support to clinicians for diagnosis and during rehabilitation.

Adult↗

PubMed2003

Is it feasible to reconstruct body segment 3-D position and orientation using accelerometric data?

The analysis of the mechanics of the musculo-skeletal system during the execution of a motor task requires the determination of the instantaneous position and orientation of the body segments involved in relation to an inertial system of reference. By using adequately assembled uniaxial accelerometric sensors, an easy-to-manage measurement system can be obtained that estimates the three-dimensional position and orientation (P&O) of a body segment through an appropriate analytical model. However, the extent to which experimental errors, in particular accelerometers (ACs) assembly inaccuracies, affect such estimation has never been systematically investigated. This paper systematically analyzes the sensitivity of analytical models of body segment P&O reconstruction through a six-AC system and a nine-AC system to different sources of experimental error. We simulated and statistically assessed the performance of these models in the case of body segment motions typical of movements under muscular control. The results obtained indicated that the inaccuracy in the orientation of the individual AC's active axes and the offset error in the AC responses were the major sources of P&O estimation errors. In particular, no accurate estimation of position was possible with the analytical models analyzed. Under the motion conditions simulated in this study, no substantial advantages were found in using a nine-AC system rather than a six-AC system. Considering that the magnitudes of the simulated experimental errors were quite low (< or = 0.1 deg: AC's orientation; < or = 10(-4) m: uncertainty of the distance between two ACs; < or = 10(-2) ms(-2): random error; 0.5 x 10(-2) ms(-2): offset error), the results indicate that none of the two ACs systems analyzed is suitable for body segment P&O estimation in routine biomechanical applications.

Acceleration↗

PubMed2003

Contribution of plantar fascia to the increased forefoot pressures in diabetic patients.

OBJECTIVES: Secondary to peripheral neuropathy, plantar hyperpressure is a proven risk factor for foot ulceration. But limited joint mobility (LJM) and soft tissue abnormalities may also contribute. The aim of this study was to evaluate the relationships among thickness of plantar fascia, mobility of the metatarso-phalangeal joint, and forces expressed under the metatarsal heads. RESEARCH DESIGN AND METHODS: We evaluated 61 diabetic patients: 27 without neuropathy (D group), 19 with neuropathy (DN group), and 15 with previous neuropathic foot ulceration (DNPU group). We also examined 21 control subjects (C). Ultrasound evaluation was performed with a high resolution 8- to 10-MHz linear array (Toshiba Tosbee SSA 240). The foot loading pattern was evaluated with a piezo-dynamometric platform. First metatarso-phalangeal joint mobility was assessed with a mechanic goniometer. RESULTS: Diabetic patients presented increased thickness of plantar fascia (D 2.9 +/- 1.2 mm, DN 3.0 +/- 0.8 mm, DNPU 3.1 +/- 1.0 mm, and C 2.0 +/- 0.5.mm; P < 0.05), and significantly reduced motion range at the metatarso-phalangeal joint (D 54.0 +/- 29.4 degrees, DN 54.9 +/- 17.2 degrees, DNPU 46.8 +/- 20.7 degrees, and C 100.0 +/- 10.0 degrees; P < 0.05). The evaluation of foot-floor interaction under the metatarsal heads showed increased vertical forces in DN and DNPU and increased medio-lateral forces in DNPU. An inverse correlation was found between the thickness of plantar fascia and metatarso-phalangeal joint mobility (r = -0.53). The thickness of plantar fascia was directly correlated with vertical forces under the metatarsal heads (r = 0.52). CONCLUSIONS: In diabetic patients, soft tissue involvement may contribute to the increase of vertical forces under the metatarsal heads. Changes in the structure of plantar fascia may also influence the mobility of the first metatarso-phalangeal joint.

Diabetes Complications↗

PubMed2002

Two-thirds power law in human locomotion: role of ground contact forces.

Are there general rules for the generation of curvilinear motion of the end-effector? Form and kinematics of the arm trajectory are typically inter-related. A relationship between velocity and curvature of the endpoint path has been previously described and quantified as the two-thirds power law. Here we show that the two-thirds power law holds also for the foot trajectory (during the swing phase) in human locomotion for a wide range of walking speeds and gravitational loads, but air-stepping. In air-stepping, it was violated systematically. The results suggest that the power law represents a general constrain of biological motion, may be attributed to both mechanical and neural factors and can depend on natural interactions with external environment.

Adult↗

PubMed2002

Walking strategy in diabetic patients with peripheral neuropathy.

OBJECTIVE: Diabetic neuropathic patients show a peculiar loading pattern of the foot, which led us to hypothesize that a substantial modification exists in their deambulatory strategy. The aim of the present study was to support this hypothesis by quantifying the changes of the loading patterns and by monitoring the excursion of center of pressure (COP) during gait. RESEARCH DESIGN AND METHODS: -A total of 21 healthy volunteers (C) and 61 diabetic patients were evaluated: 27 diabetic subjects without neuropathy (D), 19 with neuropathy (DN), and 15 with previous neuropathic ulcer (DPU). A piezo-dynamometric platform was used to record the foot-to-floor interaction by measuring loading time and the instantaneous COP position during the stance phase of gait. RESULTS: Loading time was significantly longer in neuropathic patients than in control subjects (DPU: 816.8 +/- 150 ms; DN: 828.6 +/- 152 ms; D: 766.5 +/- 89.9 ms; C: 723.7 +/- 65.7 ms; P < 0.05). COP excursion along the medio-lateral axis of the foot clearly decreased from C to DPU groups (C: 6.41 +/- 0.1 cm; D: 4.88 +/- 0.2 cm; DN: 4.57 +/- 0.1 cm; DPU: 3.36 +/- 0.1 cm; P < 0.05) as well as COP excursion along the longitudinal axis for the DPU group only (C: 26.6 +/- 1 cm; D: 26.9 +/- 1 cm; DN: 27.2 +/- 1 cm; DPU: 24.2 +/- 1 cm; P < 0.05). COP integrals were significantly reduced for all pathological classes (DPU: 14.2 +/- 8 cm(2); DN: 25.8 +/- 6 cm(2); D: 27.7 +/- 3 cm(2); C: 38.6 +/- 6 cm(2); P < 0.05). CONCLUSIONS: The accurate quantification of loading patterns and of COP excursions and integrals highlights changes of foot-to-floor interaction in diabetic neuropathic patients. The decreased medio-lateral and longitudinal COP excursions and corresponding changes of loading times and patterns support our hypothesis that a change in the walking strategy of diabetic patients with peripheral neuropathy does occur.

Adult↗