Med Biol Eng Comput DOI 10.1007/s11517-010-0731-x ORIGINAL ARTICLE Impaired gait in ankylosing spondylitis Silvia Del Din • Elena Carraro • Zimi Sawacha • Annamaria Guiotto • Lara Bonaldo • Stefano Masiero • Claudio Cobelli Received: 22 June 2010 / Accepted: 26 December 2010 Ó International Federation for Medical and Biological Engineering 2011 Abstract Ankylosing spondylitis (AS) is a chronic, significant alterations in the sagittal plane at each joint for inflammatory rheumatic disease. The spine becomes rigid AS patients (P \ 0.049). Hip and knee joint extension from the occiput to the sacrum, leading to a stooped moments showed a statistically significant reduction position. This study aims at evaluating AS subjects gait (P \ 0.044). At the ankle joint, a decreased plantarflexion alterations. Twenty-four subjects were evaluated: 12 nor- was assessed (P \ 0.048) together with the absence of the mal and 12 pathologic in stabilized anti-TNF-alpha treat- heel rocker. Gait analysis, through gait alterations identi- ment (mean age 49.42 (10.47), 25.44 (3.19) and mean body fication, allowed planning-specific rehabilitation interven- mass index 55.75 (3.19), 23.73 (2.7), respectively). Phys- tion aimed to prevent patients’ stiffness together with ical examination and gait analysis were performed. A improve balance and avoid muscles’ fatigue. motion capture system synchronized with two force plates was used. Three-dimensional kinematics and kinetics of Keywords Ankylosing spondylitis Á Kinematics Á trunk, pelvis, hip, knee and ankle were determined during Kinetics Á Three dimensional Á Gait analysis gait. A trend towards reduction was found in gait velocity and stride length. Gait analysis results showed statistically 1 Introduction Ankylosing spondylitis (AS) is a chronic, inflammatory rheumatic disease characterised by inflammatory back pain & S. Del Din Á Z. Sawacha Á A. Guiotto Á C. Cobelli ( ) due to sacroiliitis and spondylitis, the formation of syn- Department of Information Engineering, University of Padova, Via Gradenigo 6/B, 35131 Padua, Italy desmophytes leading to ankylosis, and frequently associ- e-mail: [email protected] ated with peripheral arthritis, enthesitis and acute anterior S. Del Din uveitis [31]. AS is thought to be the most common and most e-mail: [email protected] typical form of spondyloarthropathy. Spondyloarthropa- Z. Sawacha thies usually begin in the late teens and early 20s but may e-mail: [email protected] also present earlier in childhood or at an older age; it is very A. Guiotto rare for AS to first begin after 45 years of age, but disease is e-mail: [email protected] diagnosed at an older age in many patients, in part because symptoms over the years have been minimal [19]. With an E. Carraro Á L. Bonaldo Á S. Masiero estimated prevalence of 0.9% in northern European white Department of Rehabilitation Medicine, University of Padova, Via Giustiniani, 2, 35128 Padua, Italy populations, AS is a significant health burden to the com- e-mail: [email protected] munity [4, 26]. In AS, the spine becomes rigid from the L. Bonaldo occiput to the sacrum and this leads patients to experience a e-mail: [email protected] stooped position. Subjects are unable to see the horizon and S. Masiero experience a shock absorption decrease, which forces them e-mail: [email protected] to use a more cautious gait pattern [3]. 123 Med Biol Eng Comput Patients with AS could experience a progressive spinal stiffness as well as maintaining good posture and physical, kyphosis, which may induce a forward and downward psychological and social functions [6]. displacement of the centre of mass (COM) with conse- quent use of mechanisms to compensate the displacement of the trunk [10]. In these patients, the hip joint does not 2 Methods seem to be involved in their balance control. Thus, it is not involved to compensate a shift of the COM, probably 2.1 Patients because that these subjects are not able to extend com- pletely the hips when standing. So far in static condition, Twenty-four subjects were consecutively enrolled [12 the compensation may be given by means of knees flexion control subjects (CS) and 12 Ankylosing spondylitis (AS)]. and ankles plantarflexion as suggested by Bot et al. [3]. AS patients were recruited from the patients attending the Nevertheless the poor posture, decreased range of move- outpatient clinic of the Department of Rheumatology of the ment and pain assessed in AS subjects which are com- University of Padova (Italy). Demographic characteristics monly associated with balance impairment, caused the [sex, age, body mass index (BMI)] and disease character- need for monitoring the balance impairment in AS istics (disease duration, symptoms duration) were obtained. patients [22]. All patients with AS met the most recent modified New Moreover, AS did not show any negative effect on York criteria [29] and were eligible to participate in the postural stability, indeed the only clinically significant trial if they were in treatment with standard dose of anti- association was found between dynamic postural balance TNF-alfa (Infliximab, 5 mg/kg each 6 weeks) at least from and tragus to wall distance [1]. 9 months [5]. Exclusion criteria were of age older than Even though there is a clinical evidence of an altered 70 years, concomitant cardiovascular, neurological or posture [1, 3, 22], to our knowledge there are only a few psychiatric disease and severe visual or auditory impair- contributions on gait analysis of AS patients [10, 17, 30], ments (reduced visual acuity was accepted if adequately and their findings are only related to sagittal joint kine- corrected). Patients with attested orthopaedic diseases at matics, time and space parameters. Zebouni [30] observed spine and upper limb (as fracture, spinal disc herniation, decreased range of motion at the hip and knee joints even spinal surgery, etc.) and lower extremities (as prothesis, though no differences in the hip/knee angles ratio with osteoarthritis, etc.) were also excluded. respect to control group were found; in addition, a shorter The control group consisted of normal subjects enrolled stride length in AS subjects when compared to controls was among hospital personnel. noted. Finally, Helliwell [17] observed that AS subjects The study was approved by the hospital’s ethics com- ‘walked gingerly’. mittee and informed consent was obtained from all patients Ankylosing spondylitis is often associated with severe and CS. functional impairment, work disability and a compromised Subjects underwent a morphological examination of the quality of life [6, 27], and this calls for a methodology spine using specific assessment tools. The spinal and hip allowing an adequate evaluation of AS motor function, also motility of AS patients was evaluated by means of Bath helping in assessing treatment outcomes. At the best of our Ankylosing Spondylitis Metrology Index (BASMI) [18] knowledge, a complete analysis AS subjects’ motor func- which included the following five measurements: cervical tion based on three-dimensional joint kinematics and rotation, tragus to wall distance, lumbar side flexion, kinetics has not been presented. Indeed, nowadays several lumbar flexion and intermalleolar distance. studies assed the importance of gait analysis in clinical The disease activity was evaluated with the Bath evaluations, in order to provide quantitative evaluation of Ankylosing Spondylitis Disease Activity Index (BASDAI) gait deviations [13, 23]. [14] which consists of a one through 100 scale (0 being no Thus, the aim of the study was to perform gait analysis problem and 100 being the worst problem). This includes of AS patients by means of a protocol already established six items pertaining to the five major symptoms of AS: in our laboratory which evaluates both three-dimensional fatigue, spinal pain, joint pain/swelling, areas of localized kinematics and kinetics [20, 25]. An important aspect of tenderness (also called enthesitis, or inflammation of ten- our work concerns the study population: patients who are dons and ligaments), morning stiffness duration and in stabilized anti-TNF-a treatment (i.e. treatment has not morning stiffness severity. been changed at least for about 9 months) which is con- The Bath Ankylosing Spondylitis Functional Index sidered the baseline treatment for reducing the level of (BASFI) was also used for functional ability evaluation, pain, stiffness and fatigue [2, 6]. Indeed, common reha- which consists in a self-assessment tool determining how bilitation treatments are usually prescribed as a support to well a patient is currently dealing with AS [7]; BASFI the pharmacological therapy to help reducing the level of includes eight specific questions regarding function in AS 123 Med Biol Eng Comput and two questions reflecting the patient’s ability to cope with everyday life (consists of a one through 100 scale: 0 being no problem and 100 being the worst problem). 2.2 Instrumentation The instrumental assessment of gait was performed using a six cameras stereophotogrammetric BTS motion capture system (60–120 Hz) synchronized with two Bertec force plates (FP4060-10) and integrated with two Imago S.n.c plantar pressure systems (0.64 cm2 resolution, 150 Hz). A full-body marker set was used [20, 25]: 24 reflective markers were placed on the subjects at anatomical landmarks of head, trunk, thigh, shank, foot, while 24 reflective markers were used for the six clusters (each formed by four markers) of pelvis, thigh and shank (Fig. 1). The following anatomical landmarks were considered for direct marker placement: Trunk right and left acromions, spinous process of 7th cervical vertebrae (C7), spinous process of 5th lumbar vertebrae (L5) Foot right and left calcaneus, right and left first metatarsal head, right and left second metatarsal head, right and left fifth metatarsal head The following anatomical landmarks were considered for direct marker placement and were calibrated with respect to a local cluster of marker by means of a static acquisition: Fig.