Gait & Posture 40 (2014) 274–277
Contents lists available at ScienceDirect
Gait & Posture journal homepage: www.elsevier.com/locate/gaitpost
Short Communication
Multi-segment foot mobility in a hinged ankle-foot orthosis: the effect of rotation axis position A. Leardini a,*, A. Aquila a,b, P. Caravaggi a, C. Ferraresi b, S. Giannini a,c a
Movement Analysis Laboratory, Istituto Ortopedico Rizzoli, Bologna, Italy Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Italy c 1st Orthopaedic Clinic, Istituto Ortopedico Rizzoli, Bologna, Italy b
A R T I C L E I N F O
A B S T R A C T
Article history: Received 23 December 2013 Received in revised form 25 March 2014 Accepted 30 March 2014
Hinged ankle-foot orthoses are prescribed routinely for the treatment of ankle joint deficits, despite the conflicting outcomes and the little evidence on their functional efficacy. In particular, the axis of rotation of the hinge is positioned disregarding the physiological position and orientation. A multi-segment model was utilized to assess in vivo the effect of different positions for this axis on the kinematics of foot joints. A special custom-made hinged orthosis was manufactured via standard procedures for a young healthy volunteer. Four locations for the mechanical axis were obtained by a number of holes where two nuts and bolts were inserted to form the hinge: a standard position well above the malleoli, at the level of the medial malleolus, at the level of the lateral malleolus, and the physiological between the two malleoli. The shank and foot were instrumented with 15 reflective markers according to a standard protocol, and level walking was collected barefoot and with the orthosis in the four mechanical conditions. The spatio-temporal parameters observed in the physiological axis condition were the closest to normal barefoot walking. As expected, ankle joint rotation was limited to the sagittal plane. When the physiological axis was in place, rotations of the ankle out-of-sagittal planes, and of all other foot joints in the three anatomical planes, were found to be those most similar to the natural barefoot condition. These preliminary measures of intersegmental kinematics in a foot within an ankle-foot orthosis showed that only a physiological location for the ankle mechanical hinge can result in natural motion at the remaining joints and planes. ß 2014 Elsevier B.V. All rights reserved.
Keywords: Foot and ankle Orthosis Hinged AFO Multi-segmental kinematics Axis of rotation
1. Introduction Hinged ankle-foot orthoses (HAFO) are prescribed for the treatment of ankle joint deficits from neurological and orthopaedic disorders. HAFO are intended to compensate for weakness, but mainly to limit three-dimensional ankle mobility to the sagittal plane only. Quantitative assessment of their functional efficacy is still very limited, with conflicting outcomes which challenge current treatment algorithms [1]. The overall effect on activity level, or on the whole gait performance [2] as well as mechanical evidence of the function of the orthoses themselves [3–5] has been
* Corresponding author at: Movement Analysis Laboratory, Istituto Ortopedico Rizzoli, Via di Barbiano 1/10, 40136 Bologna, Italy. Tel.: +39 51 6366522; fax: +39 51 6366561. E-mail address: [email protected] (A. Leardini). http://dx.doi.org/10.1016/j.gaitpost.2014.03.188 0966-6362/ß 2014 Elsevier B.V. All rights reserved.
reported but there is very little evidence on the kinematic effects on the foot intersegmental joints. In routine custom-made manufacturing of HAFO, the mechanical hinge is positioned with a medio-lateral orientation, i.e. orthogonal to the sagittal plane of the shank, and a few centimetres above the malleoli to avoid possible interference with the shoes. This location is far from the physiological position and orientation for the ankle axis of rotation, which is known to be between the apex of the medial (MM) and lateral malleolus (LM), therefore inclined both in the frontal and transverse planes. Mobility at the ankle complex and at the other main foot joints would potentially benefit from a more physiological location of the hinge, which guides the motion of the foot plate with respect to the calf shell. The importance of joint alignment has been recently demonstrated, but only by mathematical modelling [3] and in vitro experiments [4]. Current multi-segment kinematic models provide accurate foot joint motion in non-invasive experiments, compatible also with the presence of orthoses.
[(Fig._1)TD$IG]
A. Leardini et al. / Gait & Posture 40 (2014) 274–277
275
The aim of this study is to assess in vivo the effect of the position of the mechanical hinge in unlocked HAFO on intersegmental foot kinematics. 2. Materials and methods A healthy subject (woman, 25 years old), free from any foot and ankle pathology, volunteered for the data collection. A special custom-made HAFO (Biotecnica s.r.l., Bologna, Italy) was manufactured for the subject’s right leg via standard procedures. These involved producing a lower leg plaster cast and its manual stylization, moulding of relevant thermoplastics material, testing and final refining over the cast and on the subject. In this HAFO (Fig. 1), four possible locations for its axis were established by drilling three holes each in the area of the malleoli, where two nuts and bolts were each time inserted to create the mechanical hinge. The final plastic footplate and calf shell were trimmed to avoid impingement with the skin markers. The physiological intermalleolar location for the mechanical hinge axis (MM-LM) was arranged, though its physiological inclination was sought only in the frontal plane. Exact medio-lateral orientations were also analyzed, in three different locations on the calf shell: in the standard position well above the malleoli (STD), and at the level of MM and LM. The leg of the volunteer was instrumented with fifteen reflective markers (10 mm diameter), according to a standard protocol [6]. Foot joints kinematics were first recorded during natural barefoot walking, without orthosis. Subsequently, the four different axis configurations were tested and collected, after corresponding setting of the mechanical hinge and a period of familiarization with the HAFO. A comfortable flat-soled shoe was worn on the left side. For each axis configuration, a static position in double-leg posture, and ten correct walking trials at selfselected speed were collected. An eight-camera motion capture system (Vicon Motion Systems Ltd., Oxford, UK) and two force plates (Kistler Instrument AG, Switzerland) were used to collect 100 Hz kinematics and spatio-temporal gait data. Force plates and motion of the calcaneus marker were used to identify the gait cycle between the two heel strikes. Intersegmental rotations were calculated in the sagittal, frontal and transverse planes, respectively dorsi-/plantar-flexion (Do/Pl), abduction/adduction (Abd/Add) and eversion/inversion (Eve/Inv), and for the joint between the shank and the calcaneus (Sha-Cal joint), the calcaneus and the mid-foot (Cal-Mid), the mid-foot and the metatarsus (Mid-Met), the metatarsus and the calcaneus (CalMet), and also between the shank and the entire foot (Sha-Foo). 3. Results The spatio-temporal parameters observed in the MM-LM condition were the closest to normal barefoot walking (Table 1). Those obtained in walking trials wearing the HAFO were all significantly different, i.e. t-test, from those recorded during barefoot walking, apart from the stride length in MM-LM condition. High inter-trial consistency was observed. In the barefoot condition, the mean standard deviation of each joint rotation in
Fig. 1. Pictures of the final custom-made HAFO, with the instrumented leg. (A) Front view. (B) Lateral view. (C) The three main holes on the medial side, for the nuts and bolts to be arranged to form the mechanical hinge axis of flexion (corresponding holes are on the lateral side, at the same level). (D) Close up of the foot within the footplate of the HAFO; hinge markers are here on the MM side.
each plane over the gait cycle was found smaller than 1.48 across the 10 repetitions; in the STD HAFO condition this was smaller than 1.78 in the sagittal plane, and smaller than 0.98 in the frontal and transverse planes. Therefore the mean patterns over the trials are here discussed. As expected, in general, the motion of the foot with respect to the shank (Sha-Foo) in out-of-sagittal planes was found to be limited with the HAFO with respect to the barefoot condition: in the frontal plane, the natural range of 208 reduced to about 68; in the transverse plane, the natural range of 188 reduced to less than 58 in all four HAFO conditions. In the sagittal plane, a little larger range of motion in stance and a smaller range in swing were observed for the HAFO conditions with respect to the barefoot one. For a clearer interpretation of the results, the absolute difference between every HAFO condition and barefoot was
Table 1 Mean st.dev. of the main spatio-temporal parameters over the ten repetitions, for the barefoot and the four different HAFO conditions (five columns: barefoot; standard position well above the malleoli – STD; at the level of MM; at the level of LM); physiological location through inclination MM-LM).
Stance time (%) Swing time (%) Stride length (cm) Cadence (step/min) Speed (cm/s) *
Barefoot
STD
MM
LM
MM-LM
60.3 1.0 39.7 1.0 77.1 1.4 56.7 1.1 117.4 2.8
63.2 2.3 36.8 2.3 63.9 2.8 47.3 2.0 81.0 4.0
63.6 1.3 36.4 1.3 71.7 1.0 53.4 1.3 102.7 4.0
63.5 0.7 36.5 0.7 74.8 1.5 52.4 1.2 105.1 2.0
63.3 0.7 36.7 0.7 77.0 1.5* 54.0 1.0 111.5 3.4
p > 0.05 with respect to the barefoot condition.
[(Fig._2)TD$IG]
276
A. Leardini et al. / Gait & Posture 40 (2014) 274–277
Fig. 2. Absolute difference of joint motion patterns between the four HAFO conditions (STD in yellow; MM in red; LM in cyan; MM-LM in black) and the natural barefoot condition, for each foot joint (rows) and each anatomical plane (columns). The entire gait cycle between the two heel strikes is represented (0–100%). In each plot, the mean value of the curve is reported in degrees (same colour association). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of the article.)
A. Leardini et al. / Gait & Posture 40 (2014) 274–277
calculated (Fig. 2). No considerable differences between the four HAFO conditions were observed at the Mid-Met joint, being the articulation the farthest from the ankle where the hinge position was changed. In all other joints, the three HAFO conditions with the exact medio-lateral orientation for the hinge (STD, MM and LM) showed kinematic patterns much farther than the physiological (MM-LM) condition with respect to the normal barefoot patterns. 4. Discussion For the first time experimental measurements of the kinematic effects of HAFO on intersegmental foot joint motion are reported. Previous studies investigated these effects in healthy [7] and in pathological [8,9] feet, but the foot was assumed to be a single rigid body. Only one study has reported multi-segment foot kinematics [10], but this was limited to the calcaneus and the first metatarsal, to pathological feet, and by the unnatural joint motion due to subjects wearing shoes. The present analysis was performed with an established multi-segment foot protocol [6] which has been validated in different populations [11–15]. Limitations of the study are the single subject analyzed, the unnatural unshod condition of the foot, and the partial re-orientation of the mechanical axis. The presence of the HAFO altered the overall gait patterns, the spatio-temporal parameters being all significantly different from the barefoot condition. The kinematics of most of the foot joints changed considerably with the HAFO. Whereas with this device motion of the ankle complex is forced in the sagittal plane only, it is also desirable that the kinematics of the other more distal joints remain unaltered. This was not found for the standard location for the mechanical hinge, nor in potentially more physiological locations closer to the malleoli; rather this was nearly achieved with a physiological orientation of the axis. This was true throughout the whole gait cycle, apart for a short time close to the maximum plantarflexion (Fig. 2). While more subjects and trials are certainly sought to confirm the results from this study, kinematic benefits at the foot are possible when the mechanical hinge of the current custom-made HAFO is placed closer to the exact intermalleolar axis. Acknowledgments The authors are grateful to Biotecnica s.r.l., Bologna for its technical support. This work was supported also by the Italian Ministry of Economy and Finance, programme ‘‘5 per mille’’.
277
Conflict of interest statement All authors disclose that there are no financial and personal relationships with other people or organisations that could have inappropriately influenced or biased their work for this manuscript, including also employment, consultancies, stock ownership, honoraria, paid expert testimony, patent applications/registrations, and grants or other funding. References [1] Harlaar J, Brehm M, Becher JG, Bregman DJ, Buurke J, Holtkamp F, et al. Studies examining the efficacy of ankle foot orthoses should report activity level and mechanical evidence. Prosthet Orthot Int 2010;34(3):327–35. [2] Tyson SF, Kent RM. Effects of an ankle-foot orthosis on balance and walking after stroke: a systematic review and pooled meta-analysis. Arch Phys Med Rehabil 2013;94(July (7)):1377–85. [3] Fatone S, Hansen AH. A model to predict the effect of ankle joint misalignment on calf band movement in ankle-foot orthoses. Prosthet Orthot Int 2007;31(1):76–87. [4] Gao F, Carlton W, Kapp S. Effects of joint alignment and type on mechanical properties of thermoplastic articulated AFO. Prosthet Orthot Int 2011;35(2): 181–9. [5] Ridgewell E, Sangeux M, Bach T, Baker R. A new method for measuring AFO deformation, tibial and footwear movement in three dimensional gait analysis. Gait Posture 2013;38(4):1074–6. [6] Leardini A, Benedetti MG, Berti L, Bettinelli D, Nativo R, Giannini S. Rear-foot, mid-foot and fore-foot motion during the stance phase of gait. Gait Posture 2007;25(3):453–62. [7] Radtka SA, Oliveira GB, Lindstrom KE, Borders MD. The kinematic and kinetic effects of solid, hinged, and no ankle-foot orthoses on stair locomotion in healthy adults. Gait Posture 2006;24(2):211–8. [8] Buckon CE, Thomas SS, Jakobson-Huston S, Moor M, Sussman M, Aiona M. Comparison of three ankle-foot orthosis configurations for children with spastic diplegia. Dev Med Child Neurol 2004;46(September (9)): 590–8. [9] Radtka SA, Skinner SR, Johanson ME. A comparison of gait with solid and hinged ankle-foot orthoses in children with spastic diplegic cerebral palsy. Gait Posture 2005;21(3):303–10. [10] Neville C, Lemley FR. Effect of ankle-foot orthotic devices on foot kinematics in Stage II posterior tibial tendon dysfunction. Foot Ankle Int 2012; 33(5):406–14. [11] Caravaggi P, Benedetti MG, Berti L, Leardini A. Repeatability of a multisegment foot protocol in adult subjects. Gait Posture 2011;33(1):133–5. [12] Deschamps K, Staes F, Bruyninckx H, Busschots E, Matricali GA, Spaepen P, et al. Repeatability of a 3D multi-segment foot model protocol in presence of foot deformities. Gait Posture 2012;36(3):635–8. [13] Arnold JB, Mackintosh S, Jones S, Thewlis D. Repeatability of stance phase kinematics from a multi-segment foot model in people aged 50 years and older. Gait Posture 2013;38(2):349–51. [14] Powell DW, Williams DS, Butler RJ. A comparison of two multisegment foot models in high-and low-arched athletes. J Am Podiatr Med Assoc 2013; 103(2):99–105. [15] Mahaffey R, Morrison S, Drechsler W, Cramp M. Reliability of three foot models to examine paediatric gait. J Foot Ankle Res 2013;6:43–54.
Contents lists available at ScienceDirect
Gait & Posture journal homepage: www.elsevier.com/locate/gaitpost
Short Communication
Multi-segment foot mobility in a hinged ankle-foot orthosis: the effect of rotation axis position A. Leardini a,*, A. Aquila a,b, P. Caravaggi a, C. Ferraresi b, S. Giannini a,c a
Movement Analysis Laboratory, Istituto Ortopedico Rizzoli, Bologna, Italy Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Italy c 1st Orthopaedic Clinic, Istituto Ortopedico Rizzoli, Bologna, Italy b
A R T I C L E I N F O
A B S T R A C T
Article history: Received 23 December 2013 Received in revised form 25 March 2014 Accepted 30 March 2014
Hinged ankle-foot orthoses are prescribed routinely for the treatment of ankle joint deficits, despite the conflicting outcomes and the little evidence on their functional efficacy. In particular, the axis of rotation of the hinge is positioned disregarding the physiological position and orientation. A multi-segment model was utilized to assess in vivo the effect of different positions for this axis on the kinematics of foot joints. A special custom-made hinged orthosis was manufactured via standard procedures for a young healthy volunteer. Four locations for the mechanical axis were obtained by a number of holes where two nuts and bolts were inserted to form the hinge: a standard position well above the malleoli, at the level of the medial malleolus, at the level of the lateral malleolus, and the physiological between the two malleoli. The shank and foot were instrumented with 15 reflective markers according to a standard protocol, and level walking was collected barefoot and with the orthosis in the four mechanical conditions. The spatio-temporal parameters observed in the physiological axis condition were the closest to normal barefoot walking. As expected, ankle joint rotation was limited to the sagittal plane. When the physiological axis was in place, rotations of the ankle out-of-sagittal planes, and of all other foot joints in the three anatomical planes, were found to be those most similar to the natural barefoot condition. These preliminary measures of intersegmental kinematics in a foot within an ankle-foot orthosis showed that only a physiological location for the ankle mechanical hinge can result in natural motion at the remaining joints and planes. ß 2014 Elsevier B.V. All rights reserved.
Keywords: Foot and ankle Orthosis Hinged AFO Multi-segmental kinematics Axis of rotation
1. Introduction Hinged ankle-foot orthoses (HAFO) are prescribed for the treatment of ankle joint deficits from neurological and orthopaedic disorders. HAFO are intended to compensate for weakness, but mainly to limit three-dimensional ankle mobility to the sagittal plane only. Quantitative assessment of their functional efficacy is still very limited, with conflicting outcomes which challenge current treatment algorithms [1]. The overall effect on activity level, or on the whole gait performance [2] as well as mechanical evidence of the function of the orthoses themselves [3–5] has been
* Corresponding author at: Movement Analysis Laboratory, Istituto Ortopedico Rizzoli, Via di Barbiano 1/10, 40136 Bologna, Italy. Tel.: +39 51 6366522; fax: +39 51 6366561. E-mail address: [email protected] (A. Leardini). http://dx.doi.org/10.1016/j.gaitpost.2014.03.188 0966-6362/ß 2014 Elsevier B.V. All rights reserved.
reported but there is very little evidence on the kinematic effects on the foot intersegmental joints. In routine custom-made manufacturing of HAFO, the mechanical hinge is positioned with a medio-lateral orientation, i.e. orthogonal to the sagittal plane of the shank, and a few centimetres above the malleoli to avoid possible interference with the shoes. This location is far from the physiological position and orientation for the ankle axis of rotation, which is known to be between the apex of the medial (MM) and lateral malleolus (LM), therefore inclined both in the frontal and transverse planes. Mobility at the ankle complex and at the other main foot joints would potentially benefit from a more physiological location of the hinge, which guides the motion of the foot plate with respect to the calf shell. The importance of joint alignment has been recently demonstrated, but only by mathematical modelling [3] and in vitro experiments [4]. Current multi-segment kinematic models provide accurate foot joint motion in non-invasive experiments, compatible also with the presence of orthoses.
[(Fig._1)TD$IG]
A. Leardini et al. / Gait & Posture 40 (2014) 274–277
275
The aim of this study is to assess in vivo the effect of the position of the mechanical hinge in unlocked HAFO on intersegmental foot kinematics. 2. Materials and methods A healthy subject (woman, 25 years old), free from any foot and ankle pathology, volunteered for the data collection. A special custom-made HAFO (Biotecnica s.r.l., Bologna, Italy) was manufactured for the subject’s right leg via standard procedures. These involved producing a lower leg plaster cast and its manual stylization, moulding of relevant thermoplastics material, testing and final refining over the cast and on the subject. In this HAFO (Fig. 1), four possible locations for its axis were established by drilling three holes each in the area of the malleoli, where two nuts and bolts were each time inserted to create the mechanical hinge. The final plastic footplate and calf shell were trimmed to avoid impingement with the skin markers. The physiological intermalleolar location for the mechanical hinge axis (MM-LM) was arranged, though its physiological inclination was sought only in the frontal plane. Exact medio-lateral orientations were also analyzed, in three different locations on the calf shell: in the standard position well above the malleoli (STD), and at the level of MM and LM. The leg of the volunteer was instrumented with fifteen reflective markers (10 mm diameter), according to a standard protocol [6]. Foot joints kinematics were first recorded during natural barefoot walking, without orthosis. Subsequently, the four different axis configurations were tested and collected, after corresponding setting of the mechanical hinge and a period of familiarization with the HAFO. A comfortable flat-soled shoe was worn on the left side. For each axis configuration, a static position in double-leg posture, and ten correct walking trials at selfselected speed were collected. An eight-camera motion capture system (Vicon Motion Systems Ltd., Oxford, UK) and two force plates (Kistler Instrument AG, Switzerland) were used to collect 100 Hz kinematics and spatio-temporal gait data. Force plates and motion of the calcaneus marker were used to identify the gait cycle between the two heel strikes. Intersegmental rotations were calculated in the sagittal, frontal and transverse planes, respectively dorsi-/plantar-flexion (Do/Pl), abduction/adduction (Abd/Add) and eversion/inversion (Eve/Inv), and for the joint between the shank and the calcaneus (Sha-Cal joint), the calcaneus and the mid-foot (Cal-Mid), the mid-foot and the metatarsus (Mid-Met), the metatarsus and the calcaneus (CalMet), and also between the shank and the entire foot (Sha-Foo). 3. Results The spatio-temporal parameters observed in the MM-LM condition were the closest to normal barefoot walking (Table 1). Those obtained in walking trials wearing the HAFO were all significantly different, i.e. t-test, from those recorded during barefoot walking, apart from the stride length in MM-LM condition. High inter-trial consistency was observed. In the barefoot condition, the mean standard deviation of each joint rotation in
Fig. 1. Pictures of the final custom-made HAFO, with the instrumented leg. (A) Front view. (B) Lateral view. (C) The three main holes on the medial side, for the nuts and bolts to be arranged to form the mechanical hinge axis of flexion (corresponding holes are on the lateral side, at the same level). (D) Close up of the foot within the footplate of the HAFO; hinge markers are here on the MM side.
each plane over the gait cycle was found smaller than 1.48 across the 10 repetitions; in the STD HAFO condition this was smaller than 1.78 in the sagittal plane, and smaller than 0.98 in the frontal and transverse planes. Therefore the mean patterns over the trials are here discussed. As expected, in general, the motion of the foot with respect to the shank (Sha-Foo) in out-of-sagittal planes was found to be limited with the HAFO with respect to the barefoot condition: in the frontal plane, the natural range of 208 reduced to about 68; in the transverse plane, the natural range of 188 reduced to less than 58 in all four HAFO conditions. In the sagittal plane, a little larger range of motion in stance and a smaller range in swing were observed for the HAFO conditions with respect to the barefoot one. For a clearer interpretation of the results, the absolute difference between every HAFO condition and barefoot was
Table 1 Mean st.dev. of the main spatio-temporal parameters over the ten repetitions, for the barefoot and the four different HAFO conditions (five columns: barefoot; standard position well above the malleoli – STD; at the level of MM; at the level of LM); physiological location through inclination MM-LM).
Stance time (%) Swing time (%) Stride length (cm) Cadence (step/min) Speed (cm/s) *
Barefoot
STD
MM
LM
MM-LM
60.3 1.0 39.7 1.0 77.1 1.4 56.7 1.1 117.4 2.8
63.2 2.3 36.8 2.3 63.9 2.8 47.3 2.0 81.0 4.0
63.6 1.3 36.4 1.3 71.7 1.0 53.4 1.3 102.7 4.0
63.5 0.7 36.5 0.7 74.8 1.5 52.4 1.2 105.1 2.0
63.3 0.7 36.7 0.7 77.0 1.5* 54.0 1.0 111.5 3.4
p > 0.05 with respect to the barefoot condition.
[(Fig._2)TD$IG]
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A. Leardini et al. / Gait & Posture 40 (2014) 274–277
Fig. 2. Absolute difference of joint motion patterns between the four HAFO conditions (STD in yellow; MM in red; LM in cyan; MM-LM in black) and the natural barefoot condition, for each foot joint (rows) and each anatomical plane (columns). The entire gait cycle between the two heel strikes is represented (0–100%). In each plot, the mean value of the curve is reported in degrees (same colour association). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of the article.)
A. Leardini et al. / Gait & Posture 40 (2014) 274–277
calculated (Fig. 2). No considerable differences between the four HAFO conditions were observed at the Mid-Met joint, being the articulation the farthest from the ankle where the hinge position was changed. In all other joints, the three HAFO conditions with the exact medio-lateral orientation for the hinge (STD, MM and LM) showed kinematic patterns much farther than the physiological (MM-LM) condition with respect to the normal barefoot patterns. 4. Discussion For the first time experimental measurements of the kinematic effects of HAFO on intersegmental foot joint motion are reported. Previous studies investigated these effects in healthy [7] and in pathological [8,9] feet, but the foot was assumed to be a single rigid body. Only one study has reported multi-segment foot kinematics [10], but this was limited to the calcaneus and the first metatarsal, to pathological feet, and by the unnatural joint motion due to subjects wearing shoes. The present analysis was performed with an established multi-segment foot protocol [6] which has been validated in different populations [11–15]. Limitations of the study are the single subject analyzed, the unnatural unshod condition of the foot, and the partial re-orientation of the mechanical axis. The presence of the HAFO altered the overall gait patterns, the spatio-temporal parameters being all significantly different from the barefoot condition. The kinematics of most of the foot joints changed considerably with the HAFO. Whereas with this device motion of the ankle complex is forced in the sagittal plane only, it is also desirable that the kinematics of the other more distal joints remain unaltered. This was not found for the standard location for the mechanical hinge, nor in potentially more physiological locations closer to the malleoli; rather this was nearly achieved with a physiological orientation of the axis. This was true throughout the whole gait cycle, apart for a short time close to the maximum plantarflexion (Fig. 2). While more subjects and trials are certainly sought to confirm the results from this study, kinematic benefits at the foot are possible when the mechanical hinge of the current custom-made HAFO is placed closer to the exact intermalleolar axis. Acknowledgments The authors are grateful to Biotecnica s.r.l., Bologna for its technical support. This work was supported also by the Italian Ministry of Economy and Finance, programme ‘‘5 per mille’’.
277
Conflict of interest statement All authors disclose that there are no financial and personal relationships with other people or organisations that could have inappropriately influenced or biased their work for this manuscript, including also employment, consultancies, stock ownership, honoraria, paid expert testimony, patent applications/registrations, and grants or other funding. References [1] Harlaar J, Brehm M, Becher JG, Bregman DJ, Buurke J, Holtkamp F, et al. Studies examining the efficacy of ankle foot orthoses should report activity level and mechanical evidence. Prosthet Orthot Int 2010;34(3):327–35. [2] Tyson SF, Kent RM. Effects of an ankle-foot orthosis on balance and walking after stroke: a systematic review and pooled meta-analysis. Arch Phys Med Rehabil 2013;94(July (7)):1377–85. [3] Fatone S, Hansen AH. A model to predict the effect of ankle joint misalignment on calf band movement in ankle-foot orthoses. Prosthet Orthot Int 2007;31(1):76–87. [4] Gao F, Carlton W, Kapp S. Effects of joint alignment and type on mechanical properties of thermoplastic articulated AFO. Prosthet Orthot Int 2011;35(2): 181–9. [5] Ridgewell E, Sangeux M, Bach T, Baker R. A new method for measuring AFO deformation, tibial and footwear movement in three dimensional gait analysis. Gait Posture 2013;38(4):1074–6. [6] Leardini A, Benedetti MG, Berti L, Bettinelli D, Nativo R, Giannini S. Rear-foot, mid-foot and fore-foot motion during the stance phase of gait. Gait Posture 2007;25(3):453–62. [7] Radtka SA, Oliveira GB, Lindstrom KE, Borders MD. The kinematic and kinetic effects of solid, hinged, and no ankle-foot orthoses on stair locomotion in healthy adults. Gait Posture 2006;24(2):211–8. [8] Buckon CE, Thomas SS, Jakobson-Huston S, Moor M, Sussman M, Aiona M. Comparison of three ankle-foot orthosis configurations for children with spastic diplegia. Dev Med Child Neurol 2004;46(September (9)): 590–8. [9] Radtka SA, Skinner SR, Johanson ME. A comparison of gait with solid and hinged ankle-foot orthoses in children with spastic diplegic cerebral palsy. Gait Posture 2005;21(3):303–10. [10] Neville C, Lemley FR. Effect of ankle-foot orthotic devices on foot kinematics in Stage II posterior tibial tendon dysfunction. Foot Ankle Int 2012; 33(5):406–14. [11] Caravaggi P, Benedetti MG, Berti L, Leardini A. Repeatability of a multisegment foot protocol in adult subjects. Gait Posture 2011;33(1):133–5. [12] Deschamps K, Staes F, Bruyninckx H, Busschots E, Matricali GA, Spaepen P, et al. Repeatability of a 3D multi-segment foot model protocol in presence of foot deformities. Gait Posture 2012;36(3):635–8. [13] Arnold JB, Mackintosh S, Jones S, Thewlis D. Repeatability of stance phase kinematics from a multi-segment foot model in people aged 50 years and older. Gait Posture 2013;38(2):349–51. [14] Powell DW, Williams DS, Butler RJ. A comparison of two multisegment foot models in high-and low-arched athletes. J Am Podiatr Med Assoc 2013; 103(2):99–105. [15] Mahaffey R, Morrison S, Drechsler W, Cramp M. Reliability of three foot models to examine paediatric gait. J Foot Ankle Res 2013;6:43–54.
