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Background
Pedobarography refers to dynamic measurements of the pressure distribution on the bottom of the foot through all stages of the gait cycle. It has been used to study weight-bearing foot function both in health and disease.
The Podia-Scan system (Sensor Products Inc., East Hanover, NJ) has been used to measure static plantar foot pressure distribution, and create images of pressure distribution across the plantar surface. It consists of a sensing mat, scanner and image analysis software. The system produces a color representation of the sole of the foot.
According to the manufacturer, the Podia-Scan system can be used for a wide variety of indications, e.g., to identify areas of potential ulceration, aid in the prescription of foot orthoses, determine the degree of pronation and supination, screen patients with diabetic peripheral neuropathy and other neuropathies, evaluate patients before and after surgery, regulate weight bearing after surgery, monitor degenerative foot disorders, assess orthotic efficacy, and detect scoliosis.
There is, however, inadequate evidence in the peer-reviewed published medical literature demonstrating the value of pedobarography for each of these indications.
Tuna et al (2005) compared probable plantar pressure alterations in patients with rheumatoid arthritis (RA) with normal subjects and examined the relation between pressure distribution under the foot and radiological foot erosion score. A total of 200 feet of 50 chronic RA patients and 50 healthy controls were evaluated. Static and dynamic pedobarographical evaluations were used to define the plantar pressure distribution. Furthermore, the modified Larsen scoring system was used to detect the staging of erosions on feet radiograms of patients with RA. Static pedobarography revealed higher pressure and contact areas in the fore-foot. All dynamic pedobarographical parameters except for plantar contact area were significantly different between patients with RA and control subjects. Patients with high erosion scores had higher static fore-foot and dynamic phalanx peak pressure values. These investigators concluded that pedobarographical examination can be useful to assess pressure distribution disorders in RA feet and may provide suitable guidelines for the design of various plantar supports.
Kul-Panza and Berker (2006) assessed pedobarographical findings and balance in patients with knee osteoarthritis (OA). A total of 48 patients with knee OA and 30 controls were included in this study. Pedobarographical measures were obtained from all patients and controls. Pain intensity of patients was measured using the visual analog scale (VAS). The percentage of pressure on fore-foot and hind-foot was measured using static pedobarography, and the peak pressures at fore-foot, mid-foot, and hind-foot were measured using dynamic pedobarography. The center-of-pressure sway length and width were measured for evaluation of balance. The percentage of right hind-foot pressure (p < 0.05) and peak pressure of the right fore-foot during walking were lower in the OA group than in the control group (p < 0.05). The sway width in the OA group was higher than in the control group (p < 0.05). The VAS score at rest was negatively correlated with peak pressures of both right and left hind-feet in the OA group (p < 0.05). The grade of OA was positively correlated with sway length and sway width (p < 0.05). These authors concluded that pedobarography may become a useful technique to determine foot pressures that change because of disturbed weight-bearing and balance problems in patients with knee OA.
Schmiegel et al (2008) evaluated the use of pedobarographic measurements for detecting changes in plantar loading characteristics and their relationship to foot pain in patients with RA. A total of 112 patients with RA (55.0 +/- 11.0 years of age) were divided into 3 groups according to their Health Assessment Questionnaire (HAQ) Score and compared to a control group of 20 healthy adults (CG). Thirty-six patients with good physical capacity belonged to group 1 (RA1; HAQ-score: 0 - 1.0), 38 patients with moderate capacity to group 2 (RA2; score: 1.1 - 2.0) and 38 patients with low capacity to group 3 (RA3; score: 2.1 to 3.0). Each patient's foot pain was clinically assessed. Pedobarography was used to analyze foot loading parameters while walking barefoot. In the forefoot, average pressures under the lateral forefoot were higher in RA1 patients than in RA2 patients and controls (p < 0.05) despite an inconspicuous clinical examination of the foot in RA1 patients. RA1 patients also demonstrated higher plantar pressures than RA2 under the second metatarsal head (p < 0.05). In contrast, no significant differences in maximum force could be demonstrated between patient groups. Furthermore, in RA3 patients with lower physical capacity, foot pain was increased as compared to RA1 and RA2 patients. The authors concluded that in RA patients, pedobarographic patterns show specific changes which characterize the level of functional capacity. In patients with foot involvement, pedobarographic measurements can be useful during the earlier stages of the disease, when clinical examination does not yet indicate the need for more aggressive treatment or orthopedic interventions. However, it has yet to be proven that pedobarographic measumrents would improve the management of patients with RA.
Charles et al (2001) examined if pedobarographic outcomes correlated with those post-operative results and if the dynamic pedobarography provided useful information in the functional evaluation of cavovarus feet. A total of 16 patients with cavovarus foot deformity (mean age of 32.8 years, range of 17 to 56) with a total of 21 feet were examined before and after surgery. The average follow-up time was 24 months (range of 6 to 50). The study protocol included physical examination, angle measurements on weight-bearing radiographs and dynamic pedobarography. Patients performed 5 trials at self-selected speed for each foot. The amount of correlation was established between: plantar peak pressure pattern and patient's subjective functional result, the evidence of callosities and increased peak pressures in fore-foot and mid-foot regions of interest, the change of calcaneal pitch or Hibbs' angle (first metatarsal - calcaneal axis) and the mid-foot contact area. The patient's functional opinion and pedobarographic improvement of peak pressures correlated in 7 feet, the patients estimated the result better in 13 feet and worse in 1 foot. In 4 regions of interest, callosities and increased peak pressures occurred together in 69 % of the cases, in 15.5 % callosities were observed without augmented peak pressures and in 15.5 % increased peak pressures were measured without evidence of callosities. No correlation was found between radiographical and pedobarographical parameters which describe a reduction of the cavus deformity: calcaneal pitch angle and mid-foot contact area (Pearson correlation coefficient, r = -0.36), Hibbs' angle and mid-foot contact area (r = 0.55), although all parameters changed significantly (p = 0.001). The authors stated that pre- and post-operative assessment of the cavovarus foot is mainly based on static methods such as clinical and radiographical evaluation. The results of this study demonstrated that the dynamic measurement of plantar peak pressures and contact area offers limited information about functional and anatomical improvement after surgery. Patients with severe deformities and muscular discoordination have difficulties walking consistently on the platform at each trial and severe decrease of plantar contact area makes the exact positioning of the masks difficult, which leads to problems with standardized measurements. In this context, the dynamic pedobarography can not be used as a profitable diagnostic tool that provides an objective measurement that can add a dynamic component to a clinical or radiographical examination.
Chan et al (2007) used dynamic pedobarography to study pressure distribution patterns in the foot after surgical correction of cavovarus feet. These researchers also assessed the influence of ankle power generation on pressure distribution in these feet. A total of 9 children (14 feet) diagnosed with Charcot-Marie-Tooth disease who had undergone operative treatment with a combination of osteotomies and muscle transfers were the subjects of this study. Pre- and post-operative pedobarographic measurements recorded included pressure over the medial fore-foot, lateral fore-foot, medial mid-foot (MMF), lateral mid-foot (LMF), and heel segments. In 6 patients (9 feet) who had a complete gait analysis, the power generation of the ankle was also obtained both pre-operatively and post-operatively. Lateral radiographical measurements included (i) the talus-first metatarsal angle, (ii) the calcaneus-first metatarsal angle, and (iii) the calcaneal pitch. The radiographs showed significant improvements in all 3 angles. Increased LMF and decreased fore-foot pressures were seen on pre-operative pedobarographic measures. Post-operatively, improvement in pressure at the LMF was seen. When post-operative measurements were compared with the normal values, only the LMF was similar; the other 4 segments showed decreased fore-foot and MMF pressures and increased heel pressures (p = 0.000 for the lateral fore-foot and MMF; p = 0.040 for the heel and medial fore-foot). The heel pressures displayed an inverse relationship to ankle power generation. The amount of correction achieved radiographically did not correlate with pedobarographic measurements. The increased heel pressure that was noted was not addressed by treatment. Normalization of pressure patterns should be the goal in treating children with symptomatic cavovarus feet. Although the foot deformity is corrected completely in neuromuscular disorders, pressure distribution was not normalized, and therefore, symptoms might persist. Both patients and parents should be informed about this possible problem before surgical intervention.
Jameson et al (2008) stated that although pedobarography has been widely used in quantitative clinical gait analysis for children, the collection, processing, analysis, and interpretation of the data vary widely. In most cases in children, foot dysfunction during gait is primarily a consequence of skeletal segmental mal-alignment, which can be characterized by the location and duration of the center of pressure progression (COPP) relative to the foot. This study determined the validity and reliability of a technique using the COPP and established a normative database for the COPP in children. Simultaneous pedobarograph and kinematic data collection was performed on 23 children (46 feet) who were neurologically healthy. The validity of the COPP technique was determined by comparing the pedobarograph-based and kinematic-based determinations of the orientation of the longitudinal (or long) axis of the foot, an essential component of the COPP approach. Intra-rater and inter-rater reliability for the pedobarograph-based technique were determined by comparing repeated measures of the long axis of the foot from 4 analysts. Normative data for the location and duration of the COPP were generated from this cohort of neurologically healthy children. The mean difference for the long axis of the foot between the pedobarograph-based and kinematic-based methods was 2.3 degrees (p < 0.001). The mean difference between first and second determinations of the long axis of the foot by the same analyst was 1.0 degrees (p < 0.001; correlation coefficient, 0.975). The mean difference between the 4 analysts' determinations of the long axis of the foot was 1.9 degrees (p < 0.001; correlation coefficient, 0.969). The normal COPP is located under the heel segment for 23.7 % of stance, under the mid-foot segment for 28.7 % of stance, and under the fore-foot segment for 47.5 % of stance. The authors concluded that this study established clinically acceptable validity and reliability for the pedobarograph COPP technique and determined the location and duration of the COPP in a cohort of neurologically healthy children. This standardized approach to the determination of foot loading patterns, based upon normative data, should facilitate the characterization of abnormal foot loading patterns, clinical decision making, and the assessment of outcome after a variety of interventions.
Richter and Zecj (2009) evaluated the clinical use, and analyzed the potential clinical benefit of intraoperative pedography (IP) in a sufficient number of cases in comparison with cases treated without IP. Patients (aged 18 years and older) who sustained an arthrodesis and/or correction of the foot and ankle were included. A total of 100 cases were included (ankle correction arthrodesis, n = 12; subtalar joint correction arthrodesis, n = 14; arthrodesis without correction midfoot, n = 15; correction arthrodesis mid-foot, n = 26; correction fore-foot, n = 33). Fifty-two patients were randomized for the use of IP. In 24 of the 52 patients (46 %), the correction was modified after IP during the same operation. The authors concluded that in 46 % of the cases a modification of the surgical correction was made after IP in the same surgical procedure. The authors stated that Wwhether IP improve the plantar force distribution of the foot and the mid- or long-term clinical outcome has to be critically analyzed when longer follow-up is completed.
Rongies et al (2009) assessed the progress of a selected model of rehabilitation on the basis of subpedal pressure distribution and center of gravity sway in pedobarographic examination and evaluated changes in pain intensity in patients with a history of coxarthrosis. The study included 21 patients with Altman grade 2 coxarthrosis. A postural pedobarographic examination was performed immediately before and after a 15-day course of rehabilitation with a PEL 38 electronic pedobarograph and computer image analyser with TWINN 99 software, version 2.08. Following the rehabilitation, the study group displayed a statistically significant reduction in pain intensity, improved balance between the average and maximum subpedal pressures of both feet as well as a decrease in the velocity of center of gravity sway. The authors concluded that (i) a correlation between reduced pain intensity and improved balance of loads on both feet, as well as decreased velocity of center of gravity sway were observed in the study group after the rehabilitation, (ii) the pedobarographic examination may become a new method of diagnosis and follow-up in rehabilitation, (iii) pedobarography, owing to its ease of repeatability and non-invasiveness, may constitute a valuable attempt at objective monitoring of the progress of rehabilitation and its results, and (iv) the study results encourage further research based on a larger cohort of patients and a control group with a multi-stage prospective design.
Sinclair et al (2009) noted that current methods of treating congenital clubfeet provide high rates of functional outcomes. Despite the clinical outcomes, radiographical assessment suggests residual equinus deformity of the hindfoot. It is unclear if these deformities result in abnormal foot-floor pressures and if they correlate with clinical outcome. These researchers evaluated 28 feet in 20 patients following Ponseti treatment for clubfoot by clinical and pedobarographic examination a mean of 33 months after removal of the last cast. The data were compared to age-matched and weight-matched normal subjects and to the unaffected foot in the unilaterally affected patients. Despite ankle range of motion of 30 degrees and a physiological hind-foot valgus alignment in 19 cases, pedobarography suggested differences in maximum force, impulse, contact area, and peak pressure compared to normal subjects. Compared to the unaffected foot the only difference was reduced peak pressure over the medial hind-foot and fore-foot with increased pressure over the lateral mid-foot. Similar to radiographical abnormalities in studies on treated clubfeet with good functional outcome, pedobarographic analyses show differences compared to a control group. The authors stated that the value of pedobarographic analysis for predicting successful treatment of congenital clubfoot is questionable since it does not correlate with the clinical outcome in patients treated with the Ponseti method.
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