Kinematic assessment of paediatric forefoot varus A. Alonso-Va ´ zquez a,b, *, M.A. Villarroya c , M.A. Franco c , J. Ası ´n d , B. Calvo a,b a Arago ´n Institute for Engineering Research (I3A), University of Zaragoza, Spain b CIBER on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Arago ´n Institute of Health (ICS), Spain c School of Health Sciences, University of Zaragoza, Spain d Statistical Methods Department, University of Zaragoza, Spain 1. Introduction Forefoot varus (FV) is defined as a static deformity where the plane of the metatarsal heads is supinated in relation to the hindfoot, when the subtalar joint is fixed in neutral position [1]. As a consequence, the first metatarsal is raised in relation to the other metatarsals [2,3]. FV is thought to induce increased pronation of the subtalar and mid-tarsal joints during foot stance, in order to allow the medial metatarsals to contact the floor. This may cause a drop of most of the structures of the foot towards its medial side, increasing the tibiocalcaneal angle. Instead of a rigid lever, the forefoot may become a mobile structure during push-off, produ- cing larger compressive and shear forces transmitted to the surrounding soft tissues [2,4–6]. All these changes may have negative effects on the rest of the foot, the more proximal joints of the lower limb and the spine, which will all have to adapt to these modifications. Thus, problems at the foot, ankle, knee, pelvis and the spine, have been reported in FV patients [5,7,8]. Common problems derived from FV may include pain, swelling, tiredness as well as problems of balance and coordination. Clinical prevalence of FV is a controversial issue. Visual examination and standard goniometry are the common tools in its clinical assessment and diagnosis. Recently, Cornwall et al. [9] suggested that between 8.8% and 15% of the population are affected by FV. However, previous studies had suggested much higher levels [3,10]. Differences in the screening protocols may well explain these discrepancies, thus, stressing the inherent difficulty of the correct clinical assessment of a pathology often hidden by the compensatory effects in other structures of the lower limb. Assessment of the dynamic motion of the foot and lower limb via in vivo three-dimensional (3D) measurements could add another perspective to the results of clinical examination. This would help confirm the diagnosis and provide insight to the Gait & Posture 29 (2009) 214–219 ARTICLE INFO Article history: Received 21 January 2008 Received in revised form 3 August 2008 Accepted 12 August 2008 Keywords: Forefoot varus Foot model Kinematics Discriminant analysis Gait analysis ABSTRACT Forefoot varus is a static deformity not easy to assess clinically. If left uncorrected, it is thought to affect both the posture of the patient and the kinematics of their lower limbs, and even the spine. Three- dimensional gait assessment could help to confirm forefoot varus diagnosis and provide objective evidence of the functional adaptive mechanisms postulated in the literature. The recently available Oxford Foot Model was used, simultaneously with a conventional lower limb model, to compare the kinematics of 10 forefoot varus children (aged 8–13) and 11 healthy controls (aged 7–13) during gait. Data acquisition was performed using a six-camera motion capture system, with a total of 27 reflective markers. A patient-by-patient comparison with the controls suggested several compensation patterns, although statistically significant differences were found only for the mean values of hip adduction/ abduction during load response and midstance and hip flexion/extension during pre-swing. A multivariate statistical technique was used to determine which of the measured variables better separated both groups. The best discriminant model presented here includes hip adduction/abduction during load response, hindfoot/tibia inversion/eversion during pre-swing, hindfoot/tibia dorsiflexion/ plantar flexion during load response and arch height during midstance, providing a rate of correct classification of 81%. The results could not fully confirm the kinematic relationships suggested in the literature. The small degree of forefoot varus deformity present in the patient group could have prevented other variables from becoming discriminant. A larger patient sample would help determine the possible different compensatory patterns to different degrees of forefoot varus. ß 2008 Elsevier B.V. All rights reserved. * Corresponding author at: Arago ´ n Institute for Engineering Research (I3A), University of Zaragoza, Betancourt Building, Maria de Luna 3, 50018 Zaragoza, Spain. Tel.: +34 976761000; fax: +34 976762578. E-mail address: analonso@unizar.es (A. Alonso-Va ´ zquez). Contents lists available at ScienceDirect Gait & Posture journal homepage: www.elsevier.com/locate/gaitpost 0966-6362/$ – see front matter ß 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.gaitpost.2008.08.009