Use of multiple calibration in multisegment foot 3D kinematics

INTRODUCTION Soft tissue artefact has been recognized as the most critical source of error in gait analysis data. These errors affecting the estimates of anatomical landmarks trajectories in the laboratory frame can be considerably reduced by following the Multiple Calibrated Anatomical System Technique protocol which entails themultiple static calibrations of the anatomical landmarks in a technical reference frame defined by a cluster of skin markers; 2. flexion/extension angle interpolation of the anatomical landmark calibrations taken at the extremes of motion. [1]. PROPOSTA ALTERNATIVA: Soft tissue artefact (STA) has been recognized as the most critical source of error in gait analysis data. STA was proved to critically affect relevant joint kinematics and several methods were proposed to compensate for its effect [riferire la rev GP 2005??]. Among the proposed methods multiple calibration recently resulted particularly effective in compensating for STA propagation to knee kinematics [1]. PER LEGARE QUI SERVIREBBE UNA FRASETTA SULL?IMPORTANZA DEI PROTOCOLLI DI PIEDE (?? Tipo Recently, as a consequence to the rising clinical interest in the quantification of foot segments kinematics during daily living activities, several new protocols for the quantification of foot kinematics have been proposed. Although never quantified, STA propagation to foot kinematics is expected to be extremely critical, therefore…) The purpose of the present work was to describe and assess the performance of the multiple calibration methodology on foot subsegments and ankle joint rotations during gait analysis. METHODS The 3 dimensional multisegment foot protocol described in Sawacha et al. 2009 [2] was applied on the same subject first by means of direct skin marker placement (figure 1a) and second in a modified version which entails calibrating each anatomical landmark with respect to a local cluster of marker (figure 1b). Multiple calibration was performed [1] in three different positions: neutral position, maximum passive dorsiflexion (figure 1c), maximum passive plantarflexion. The multiple calibration procedure was carried on by two physicians in order to test the inter-operator repeatability of this technique. Six cameras BTS S.r.l. motion capture system (60-120 Hz) synchronized with 2 Bertec force plates (FP4060-10) were used. Three walking trials were acquired and a static acquisition in standing upright position (with their feet placed with ankles together, toes pointed 30 degrees apart) was also performed. Qui le calibrazioni., Anatomical reference systems were computed and joint angles estimated through direct skin marker application [2] and by means of performing the anatomical calibration on each anatomical landmark. Both single [3] and multiple calibration [1] were used. The latter was performed using, as control variable, the ankle dorsi/plantarflexion angle evaluated with single calibration in neutral position (figure 2). Mean and SD values of each subsegment relative angle were evaluated OVER?: dorsi/plantarflexion (dp), inversion/eversion (invev) and internal/external rotation (ier) for hindfoot-tibia (ht), midfoot-hindfoot (mh) and forefoot-midfoot (fm). RESULTS AND DISCUSSION 3dimensional foot subsegment RELATIVE? angles during the stance phase of gait (see figure 3) have been determined with the original model [2], by means of the single calibration approach in the three different conditions (respectively calibrating each anatomical landmark in the neutral position, in the maximum ankle dorsiflexion and in the maximum ankle plantarflexion) and by means of multiple calibration. In Table 1 the results of the comparison among the methodologies have been reported with respect to subsegments’ angles. Mean and standard deviation has been reported for direct skin markers method [2], and for each operator’s single and multiple calibration. Multiple calibration has been demonstrated to be an important tool for ...