ORIGINAL ARTICLE Dynamic Foot Pressure Measurements for Assessing Foot Deformity in Persons With Spastic Cerebral Palsy Eun Sook Park, MD, PhD, Hyun Woo Kim, MD, PhD, Chang Il Park, MD, PhD, Dong-wook Rha, MD, MS, Chan Woo Park, MD ABSTRACT. Park ES, Kim HW, Park CI, Rha D, Park CW. Dynamic foot pressure measurements for assessing foot defor- mity in persons with spastic cerebral palsy. Arch Phys Med Rehabil 2006;87:703-9. Objectives: To identify characteristics of foot pressure dis- tribution in different foot deformities using a computerized insole sensor system, and to identify changes in these param- eters after corrective surgery in children with spastic cerebral palsy (CP). Design: Before-after trial. Setting: University hospital. Participants: Sixty-seven limbs of 44 children with spas- tic CP were assessed (35 equinus, 17 equinovarus, 15 equi- novalgus). Intervention: Orthopedic surgery for foot deformities. Main Outcome Measures: Parameters of foot contact pat- tern, pressure-time integral (PTI), and center of pressure (COP) trajectories were assessed before and at a minimum of 6 months postsurgery, using the F-scan system. Results: Prior to surgery, the medial midfoot relative im- pulse, which is PTI normalized by a percentage of the entire foot, differed significantly between foot deformity groups. Rel- ative impulse was high on the lateral column of the foot in the equinovarus group and on the medial column of the foot in the equinovalgus group. Center of pressure index (COPI) and coronal index reflecting the asymmetry of the medial and lateral columns of the foot differed significantly between the equinovalgus and equinovarus groups. After surgery, signifi- cant changes occurred in foot contact patterns, including total contact area, contact length, contact width of hindfoot, and the relative impulse of specific areas of the foot. In addition, there were significant changes in the parameters of COP, such as anteroposterior displacement, slope, and velocity. Conclusions: In dynamic foot pressure measurements using a computerized insole sensor system, the parameters reflecting medial or lateral changes in weight bearing, such as COPI and coronal index, appear to be useful for evaluating abnormalities and improvements after intervention in the frontal plane, such as varus and valgus. Additionally, assessment of parameters in foot contact patterns, PTIs, and COP path trajectories appears to be helpful in evaluating outcomes after corrective surgery. Key Words: Cerebral palsy; Foot deformities; Rehabilitation. © 2006 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation E QUINUS IS THE MOST COMMON foot deformity in people with cerebral palsy (CP) and often is associated with varus or valgus deformity of the hindfoot. 1,2 Foot defor- mity is caused by spasticity and an imbalance of muscles; it may adversely affect standing and walking ability. Operative treatment for foot deformity is recommended for cases in which prolonged nonoperative therapies such as phys- iotherapy, ankle-foot orthoses, casting, nerve block, and injec- tions of botulinum toxin have failed. An objective evaluation of foot disorders would be useful in planning surgical manage- ment and in assessing the outcome of treatment. Although the 3-dimensional gait analysis system has been widely used for planning corrective musculoskeletal surgery in people with CP, the system has limited ability to reveal significant changes of foot deformity after surgery. 3 Radiographic measurements of foot deformity have been considered the most useful tools for preoperative assessment when surgery is indicated. 1 The dy- namic deformity that occurs during walking, which needs to be accurately assessed for a successful surgical outcome, may not, however, be adequately judged with radiographic measure- ments. 1 Measuring foot pressure during walking may be useful for demonstrating dynamic changes in the foot. With the com- puterized insole sensor system, this pressure measurement can be reliably and quantitatively assessed. 4-7 The clinical relevance of the pressure measurement in the evaluation of foot deformity caused by neurogenic and congenital disor- ders has been reported. 1,2,8 There are several parameters in dynamic foot pressure mea- surements. These parameters can be grouped into 3 categories: measurements of foot contact pattern, measurements of plantar pressure distributions (eg, peak pressure time, pressure-time integrals [PTIs]), and assessment of the center of pressure (COP) trajectories. Foot contact patterns were used in a previ- ous study 8 to assess the improvement of a pes planovalgus deformity after lateral column lengthening. The characteristics of the PTI of foot pressure have been reported previously for evaluation of foot deformities. 1,2 The changes of peak pressure at the heel after botulinum toxin injection for equinus foot were also reported. 9 The COP trajectories during the stance phase have been used to assess a subject’s locomotion and sense of balance. 5,10-12 In addition, COP trajectories were used to detect pronation movement of the subtalar joint immediately after heel strike, which was related to poor long-term functional outcome in surgically treated clubfeet. 12 COP parameters have not, however, been used to evaluate foot deformity in subjects with CP. To our knowledge, all parameters of foot pressure measurement in different foot deformities have not been simul- taneously assessed and compared in subjects with CP. From the Department and Research Institute of Rehabilitation Medicine (ES Park, CI Park, Rha, CW Park), Department of Orthopaedic Surgery (Kim), and BK 21 Project for Medical Sciences (ES Park), Yonsei University College of Medicine, Seoul, South Korea. No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the author(s) or upon any organization with which the author(s) is/are associated. Reprint requests to Dong-wook Rha, MD, MS, Seodaemun-gu Shinchon-dong 134, Rehabilitation Hospital, Yonsei University College of Medicine, Seoul, Korea, 120- 752, e-mail: medicus@yumc.yonsei.ac.kr. 0003-9993/06/8705-10352$32.00/0 doi:10.1016/j.apmr.2005.12.038 703 Arch Phys Med Rehabil Vol 87, May 2006